Primack, Joel R.
2000-01-01
The cosmological parameters that I emphasize are the age of the universe $t_0$, the Hubble parameter $H_0 \\equiv 100 h$ km s$^{-1}$ Mpc$^{-1}$, the average matter density $\\Omega_m$, the baryonic matter density $\\Omega_b$, the neutrino density $\\Omega_\
Inflation and cosmological parameter estimation
Energy Technology Data Exchange (ETDEWEB)
Hamann, J.
2007-05-15
In this work, we focus on two aspects of cosmological data analysis: inference of parameter values and the search for new effects in the inflationary sector. Constraints on cosmological parameters are commonly derived under the assumption of a minimal model. We point out that this procedure systematically underestimates errors and possibly biases estimates, due to overly restrictive assumptions. In a more conservative approach, we analyse cosmological data using a more general eleven-parameter model. We find that regions of the parameter space that were previously thought ruled out are still compatible with the data; the bounds on individual parameters are relaxed by up to a factor of two, compared to the results for the minimal six-parameter model. Moreover, we analyse a class of inflation models, in which the slow roll conditions are briefly violated, due to a step in the potential. We show that the presence of a step generically leads to an oscillating spectrum and perform a fit to CMB and galaxy clustering data. We do not find conclusive evidence for a step in the potential and derive strong bounds on quantities that parameterise the step. (orig.)
Cosmological parameter estimation using Particle Swarm Optimization
Prasad, J.; Souradeep, T.
2014-03-01
Constraining parameters of a theoretical model from observational data is an important exercise in cosmology. There are many theoretically motivated models, which demand greater number of cosmological parameters than the standard model of cosmology uses, and make the problem of parameter estimation challenging. It is a common practice to employ Bayesian formalism for parameter estimation for which, in general, likelihood surface is probed. For the standard cosmological model with six parameters, likelihood surface is quite smooth and does not have local maxima, and sampling based methods like Markov Chain Monte Carlo (MCMC) method are quite successful. However, when there are a large number of parameters or the likelihood surface is not smooth, other methods may be more effective. In this paper, we have demonstrated application of another method inspired from artificial intelligence, called Particle Swarm Optimization (PSO) for estimating cosmological parameters from Cosmic Microwave Background (CMB) data taken from the WMAP satellite.
Cosmological parameter estimation using Particle Swarm Optimization
International Nuclear Information System (INIS)
Prasad, J; Souradeep, T
2014-01-01
Constraining parameters of a theoretical model from observational data is an important exercise in cosmology. There are many theoretically motivated models, which demand greater number of cosmological parameters than the standard model of cosmology uses, and make the problem of parameter estimation challenging. It is a common practice to employ Bayesian formalism for parameter estimation for which, in general, likelihood surface is probed. For the standard cosmological model with six parameters, likelihood surface is quite smooth and does not have local maxima, and sampling based methods like Markov Chain Monte Carlo (MCMC) method are quite successful. However, when there are a large number of parameters or the likelihood surface is not smooth, other methods may be more effective. In this paper, we have demonstrated application of another method inspired from artificial intelligence, called Particle Swarm Optimization (PSO) for estimating cosmological parameters from Cosmic Microwave Background (CMB) data taken from the WMAP satellite
Chandra Cluster Cosmology Project III: Cosmological Parameter Constraints
DEFF Research Database (Denmark)
Vikhlinin, A.; Kravtsov, A. V.; Burenin, R. A.
2009-01-01
function evolution to be used as a useful growth of a structure-based dark energy probe. In this paper, we present cosmological parameter constraints obtained from Chandra observations of 37 clusters with langzrang = 0.55 derived from 400 deg2 ROSAT serendipitous survey and 49 brightest z ≈ 0.05 clusters...
Constraints on cosmological parameters in power-law cosmology
International Nuclear Information System (INIS)
Rani, Sarita; Singh, J.K.; Altaibayeva, A.; Myrzakulov, R.; Shahalam, M.
2015-01-01
In this paper, we examine observational constraints on the power law cosmology; essentially dependent on two parameters H 0 (Hubble constant) and q (deceleration parameter). We investigate the constraints on these parameters using the latest 28 points of H(z) data and 580 points of Union2.1 compilation data and, compare the results with the results of ΛCDM . We also forecast constraints using a simulated data set for the future JDEM, supernovae survey. Our studies give better insight into power law cosmology than the earlier done analysis by Kumar [arXiv:1109.6924] indicating it tuning well with Union2.1 compilation data but not with H(z) data. However, the constraints obtained on i.e. H 0 average and q average using the simulated data set for the future JDEM, supernovae survey are found to be inconsistent with the values obtained from the H(z) and Union2.1 compilation data. We also perform the statefinder analysis and find that the power-law cosmological models approach the standard ΛCDM model as q → −1. Finally, we observe that although the power law cosmology explains several prominent features of evolution of the Universe, it fails in details
Cosmological Constraints on Mirror Matter Parameters
International Nuclear Information System (INIS)
Wallemacq, Quentin; Ciarcelluti, Paolo
2014-01-01
Up-to-date estimates of the cosmological parameters are presented as a result of numerical simulations of cosmic microwave background and large scale structure, considering a flat Universe in which the dark matter is made entirely or partly of mirror matter, and the primordial perturbations are scalar adiabatic and in linear regime. A statistical analysis using the Markov Chain Monte Carlo method allows to obtain constraints of the cosmological parameters. As a result, we show that a Universe with pure mirror dark matter is statistically equivalent to the case of an admixture with cold dark matter. The upper limits for the ratio of the temperatures of ordinary and mirror sectors are around 0.3 for both the cosmological models, which show the presence of a dominant fraction of mirror matter, 0.06≲Ω_m_i_r_r_o_rh"2≲0.12.
Cluster cosmology with next-generation surveys.
Ascaso, B.
2017-03-01
The advent of next-generation surveys will provide a large number of cluster detections that will serve the basis for constraining cos mological parameters using cluster counts. The main two observational ingredients needed are the cluster selection function and the calibration of the mass-observable relation. In this talk, we present the methodology designed to obtain robust predictions of both ingredients based on realistic cosmological simulations mimicking the following next-generation surveys: J-PAS, LSST and Euclid. We display recent results on the selection functions for these mentioned surveys together with others coming from other next-generation surveys such as eROSITA, ACTpol and SPTpol. We notice that the optical and IR surveys will reach the lowest masses between 0.3
International Nuclear Information System (INIS)
Novikov, I.D.
1979-01-01
Progress made by this Commission over the period 1976-1978 is reviewed. Topics include the Hubble constant, deceleration parameter, large-scale distribution of matter in the universe, radio astronomy and cosmology, space astronomy and cosmology, formation of galaxies, physics near the cosmological singularity, and unconventional cosmological models. (C.F.)
Bias-limited extraction of cosmological parameters
Energy Technology Data Exchange (ETDEWEB)
Shimon, Meir; Itzhaki, Nissan; Rephaeli, Yoel, E-mail: meirs@wise.tau.ac.il, E-mail: nitzhaki@post.tau.ac.il, E-mail: yoelr@wise.tau.ac.il [School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel)
2013-03-01
It is known that modeling uncertainties and astrophysical foregrounds can potentially introduce appreciable bias in the deduced values of cosmological parameters. While it is commonly assumed that these uncertainties will be accounted for to a sufficient level of precision, the level of bias has not been properly quantified in most cases of interest. We show that the requirement that the bias in derived values of cosmological parameters does not surpass nominal statistical error, translates into a maximal level of overall error O(N{sup −½}) on |ΔP(k)|/P(k) and |ΔC{sub l}|/C{sub l}, where P(k), C{sub l}, and N are the matter power spectrum, angular power spectrum, and number of (independent Fourier) modes at a given scale l or k probed by the cosmological survey, respectively. This required level has important consequences on the precision with which cosmological parameters are hoped to be determined by future surveys: in virtually all ongoing and near future surveys N typically falls in the range 10{sup 6}−10{sup 9}, implying that the required overall theoretical modeling and numerical precision is already very high. Future redshifted-21-cm observations, projected to sample ∼ 10{sup 14} modes, will require knowledge of the matter power spectrum to a fantastic 10{sup −7} precision level. We conclude that realizing the expected potential of future cosmological surveys, which aim at detecting 10{sup 6}−10{sup 14} modes, sets the formidable challenge of reducing the overall level of uncertainty to 10{sup −3}−10{sup −7}.
Cosmological parameters from SDSS and WMAP
International Nuclear Information System (INIS)
Tegmark, Max; Strauss, Michael A.; Bahcall, Neta A.; Schlegel, David; Finkbeiner, Douglas; Gunn, James E.; Ostriker, Jeremiah P.; Seljak, Uros; Ivezic, Zeljko; Knapp, Gillian R.; Lupton, Robert H.; Blanton, Michael R.; Scoccimarro, Roman; Hogg, David W.; Abazajian, Kevork; Xu Yongzhong; Dodelson, Scott; Sandvik, Havard; Wang Xiaomin; Jain, Bhuvnesh
2004-01-01
We measure cosmological parameters using the three-dimensional power spectrum P(k) from over 200 000 galaxies in the Sloan Digital Sky Survey (SDSS) in combination with Wilkinson Microwave Anisotropy Probe (WMAP) and other data. Our results are consistent with a 'vanilla' flat adiabatic cold dark matter model with a cosmological constant without tilt (n s =1), running tilt, tensor modes, or massive neutrinos. Adding SDSS information more than halves the WMAP-only error bars on some parameters, tightening 1σ constraints on the Hubble parameter from h≅0.74 -0.07 +0.18 to h≅0.70 -0.03 +0.04 , on the matter density from Ω m ≅0.25±0.10 to Ω m ≅0.30±0.04 (1σ) and on neutrino masses from 0 ≅16.3 -1.8 +2.3 Gyr to t 0 ≅14.1 -0.9 +1.0 Gyr by adding SDSS and SN Ia data. Including tensors, running tilt, neutrino mass and equation of state in the list of free parameters, many constraints are still quite weak, but future cosmological measurements from SDSS and other sources should allow these to be substantially tightened
Planck 2013 results. XVI. Cosmological parameters
Ade, P.A.R.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A.J.; Barreiro, R.B.; Bartlett, J.G.; Battaner, E.; Benabed, K.; Benoit, A.; Benoit-Levy, A.; Bernard, J.P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bock, J.J.; Bonaldi, A.; Bond, J.R.; Borrill, J.; Bouchet, F.R.; Bridges, M.; Bucher, M.; Burigana, C.; Butler, R.C.; Calabrese, E.; Cappellini, B.; Cardoso, J.F.; Catalano, A.; Challinor, A.; Chamballu, A.; Chary, R.R.; Chen, X.; Chiang, L.Y.; Chiang, H.C.; Christensen, P.R.; Church, S.; Clements, D.L.; Colombi, S.; Colombo, L.P.L.; Couchot, F.; Coulais, A.; Crill, B.P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R.D.; Davis, R.J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.M.; Desert, F.X.; Dickinson, C.; Diego, J.M.; Dolag, K.; Dole, H.; Donzelli, S.; Dore, O.; Douspis, M.; Dunkley, J.; Dupac, X.; Efstathiou, G.; Elsner, F.; Ensslin, T.A.; Eriksen, H.K.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A.A.; Franceschi, E.; Gaier, T.C.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Giardino, G.; Giraud-Heraud, Y.; Gjerlow, E.; Gonzalez-Nuevo, J.; Gorski, K.M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J.E.; Haissinski, J.; Hamann, J.; Hansen, F.K.; Hanson, D.; Harrison, D.; Henrot-Versille, S.; Hernandez-Monteagudo, C.; Herranz, D.; Hildebrandt, S.R.; Hivon, E.; Hobson, M.; Holmes, W.A.; Hornstrup, A.; Hou, Z.; Hovest, W.; Huffenberger, K.M.; Jaffe, T.R.; Jaffe, A.H.; Jewell, J.; Jones, W.C.; Juvela, M.; Keihanen, E.; Keskitalo, R.; Kisner, T.S.; Kneissl, R.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lahteenmaki, A.; Lamarre, J.M.; Lasenby, A.; Lattanzi, M.; Laureijs, R.J.; Lawrence, C.R.; Leach, S.; Leahy, J.P.; Leonardi, R.; Leon-Tavares, J.; Lesgourgues, J.; Lewis, A.; Liguori, M.; Lilje, P.B.; Linden-Vornle, M.; Lopez-Caniego, M.; Lubin, P.M.; Macias-Perez, J.F.; Maffei, B.; Maino, D.; Mandolesi, N.; Maris, M.; Marshall, D.J.; Martin, P.G.; Martinez-Gonzalez, E.; Masi, S.; Matarrese, S.; Matthai, F.; Mazzotta, P.; Meinhold, P.R.; Melchiorri, A.; Melin, J.B.; Mendes, L.; Menegoni, E.; Mennella, A.; Migliaccio, M.; Millea, M.; Mitra, S.; Miville-Deschenes, M.A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C.B.; Norgaard-Nielsen, H.U.; Noviello, F.; Novikov, D.; Novikov, I.; O'Dwyer, I.J.; Osborne, S.; Oxborrow, C.A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Partridge, B.; Pasian, F.; Patanchon, G.; Pearson, D.; Pearson, T.J.; Peiris, H.V.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Platania, P.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G.W.; Prezeau, G.; Prunet, S.; Puget, J.L.; Rachen, J.P.; Reach, W.T.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rowan-Robinson, M.; Rubino-Martin, J.A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Seiffert, M.D.; Shellard, E.P.S.; Spencer, L.D.; Starck, J.L.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Sureau, F.; Sutton, D.; Suur-Uski, A.S.; Sygnet, J.F.; Tauber, J.A.; Tavagnacco, D.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Turler, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L.A.; Wandelt, B.D.; Wehus, I.K.; White, M.; White, S.D.M.; Wilkinson, A.; Yvon, D.; Zacchei, A.; Zonca, A.
2014-10-29
We present the first results based on Planck measurements of the CMB temperature and lensing-potential power spectra. The Planck spectra at high multipoles are extremely well described by the standard spatially-flat six-parameter LCDM cosmology. In this model Planck data determine the cosmological parameters to high precision. We find a low value of the Hubble constant, H0=67.3+/-1.2 km/s/Mpc and a high value of the matter density parameter, Omega_m=0.315+/-0.017 (+/-1 sigma errors) in excellent agreement with constraints from baryon acoustic oscillation (BAO) surveys. Including curvature, we find that the Universe is consistent with spatial flatness to percent-level precision using Planck CMB data alone. We present results from an analysis of extensions to the standard cosmology, using astrophysical data sets in addition to Planck and high-resolution CMB data. None of these models are favoured significantly over standard LCDM. The deviation of the scalar spectral index from unity is insensitive to the additi...
Constraining cosmological parameter with SN Ia
International Nuclear Information System (INIS)
Putri, A N Indra; Wulandari, H R Tri
2016-01-01
A type I supemovae (SN Ia) is an exploding white dwarf, whose mass exceeds Chandrasekar limit (1.44 solar mass). If a white dwarf is in a binary system, it may accrete matter from the companion, resulting in an excess mass that cannot be balanced by the pressure of degenerated electrons in the core. SNe Ia are highly luminous objects, that they are visible from very high distances. After some corrections (stretch (s), colour (c), K-corrections, etc.), the variations in the light curves of SNe Ia can be suppressed to be no more than 10%. Their high luminosity and almost uniform intrinsic brightness at the peak light, i.e. M B ∼ -19, make SNe Ia ideal standard candle. Because of their visibility from large distances, SNe Ia can be employed as a cosmological measuring tool. It was analysis of SNe Ia data that indicated for the first time, that the universe is not only expanding, but also accelerating. This work analyzed a compilation of SNe Ia data to determine several cosmological parameters (H 0 , Ω m , Ω a , and w ). It can be concluded from the analysis, that our universe is a flat, dark energy dominated universe, and that the cosmological constant A is a suitable candidate for dark energy. (paper)
Planck 2015 results. XIII. Cosmological parameters
Ade, P.A.R.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A.J.; Barreiro, R.B.; Bartlett, J.G.; Bartolo, N.; Battaner, E.; Battye, R.; Benabed, K.; Benoit, A.; Benoit-Levy, A.; Bernard, J.P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J.R.; Borrill, J.; Bouchet, F.R.; Boulanger, F.; Bucher, M.; Burigana, C.; Butler, R.C.; Calabrese, E.; Cardoso, J.F.; Catalano, A.; Challinor, A.; Chamballu, A.; Chary, R.R.; Chiang, H.C.; Chluba, J.; Christensen, P.R.; Church, S.; Clements, D.L.; Colombi, S.; Colombo, L.P.L.; Combet, C.; Coulais, A.; Crill, B.P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R.D.; Davis, R.J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Desert, F.X.; Di Valentino, E.; Dickinson, C.; Diego, J.M.; Dolag, K.; Dole, H.; Donzelli, S.; Dore, O.; Douspis, M.; Ducout, A.; Dunkley, J.; Dupac, X.; Efstathiou, G.; Elsner, F.; Ensslin, T.A.; Eriksen, H.K.; Farhang, M.; Fergusson, J.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A.A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Gauthier, C.; Gerbino, M.; Ghosh, T.; Giard, M.; Giraud-Heraud, Y.; Giusarma, E.; Gjerlow, E.; Gonzalez-Nuevo, J.; Gorski, K.M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J.E.; Hamann, J.; Hansen, F.K.; Hanson, D.; Harrison, D.L.; Helou, G.; Henrot-Versille, S.; Hernandez-Monteagudo, C.; Herranz, D.; Hildebrandt, S.R.; Hivon, E.; Hobson, M.; Holmes, W.A.; Hornstrup, A.; Hovest, W.; Huang, Z.; Huffenberger, K.M.; Hurier, G.; Jaffe, A.H.; Jaffe, T.R.; Jones, W.C.; Juvela, M.; Keihanen, E.; Keskitalo, R.; Kisner, T.S.; Kneissl, R.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lahteenmaki, A.; Lamarre, J.M.; Lasenby, A.; Lattanzi, M.; Lawrence, C.R.; Leahy, J.P.; Leonardi, R.; Lesgourgues, J.; Levrier, F.; Lewis, A.; Liguori, M.; Lilje, P.B.; Linden-Vornle, M.; Lopez-Caniego, M.; Lubin, P.M.; Macias-Perez, J.F.; Maggio, G.; Mandolesi, N.; Mangilli, A.; Marchini, A.; Martin, P.G.; Martinelli, M.; Martinez-Gonzalez, E.; Masi, S.; Matarrese, S.; Mazzotta, P.; McGehee, P.; Meinhold, P.R.; Melchiorri, A.; Melin, J.B.; Mendes, L.; Mennella, A.; Migliaccio, M.; Millea, M.; Mitra, S.; Miville-Deschenes, M.A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Murphy, J.A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C.B.; Norgaard-Nielsen, H.U.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C.A.; Paci, F.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Partridge, B.; Pasian, F.; Patanchon, G.; Pearson, T.J.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Popa, L.; Pratt, G.W.; Prezeau, G.; Prunet, S.; Puget, J.L.; Rachen, J.P.; Reach, W.T.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; d'Orfeuil, B.Rouille; Rowan-Robinson, M.; Rubino-Martin, J.A.; Rusholme, B.; Said, N.; Salvatelli, V.; Salvati, L.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Seiffert, M.D.; Serra, P.; Shellard, E.P.S.; Spencer, L.D.; Spinelli, M.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.S.; Sygnet, J.F.; Tauber, J.A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Trombetti, T.; Tucci, M.; Tuovinen, J.; Turler, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L.A.; Wandelt, B.D.; Wehus, I.K.; White, M.; White, S.D.M.; Wilkinson, A.; Yvon, D.; Zacchei, A.; Zonca, A.
2016-01-01
We present results based on full-mission Planck observations of temperature and polarization anisotropies of the CMB. These data are consistent with the six-parameter inflationary LCDM cosmology. From the Planck temperature and lensing data, for this cosmology we find a Hubble constant, H0= (67.8 +/- 0.9) km/s/Mpc, a matter density parameter Omega_m = 0.308 +/- 0.012 and a scalar spectral index with n_s = 0.968 +/- 0.006. (We quote 68% errors on measured parameters and 95% limits on other parameters.) Combined with Planck temperature and lensing data, Planck LFI polarization measurements lead to a reionization optical depth of tau = 0.066 +/- 0.016. Combining Planck with other astrophysical data we find N_ eff = 3.15 +/- 0.23 for the effective number of relativistic degrees of freedom and the sum of neutrino masses is constrained to < 0.23 eV. Spatial curvature is found to be |Omega_K| < 0.005. For LCDM we find a limit on the tensor-to-scalar ratio of r <0.11 consistent with the B-mode constraints fr...
Cosmological parameter estimation using particle swarm optimization
Prasad, Jayanti; Souradeep, Tarun
2012-06-01
Constraining theoretical models, which are represented by a set of parameters, using observational data is an important exercise in cosmology. In Bayesian framework this is done by finding the probability distribution of parameters which best fits to the observational data using sampling based methods like Markov chain Monte Carlo (MCMC). It has been argued that MCMC may not be the best option in certain problems in which the target function (likelihood) poses local maxima or have very high dimensionality. Apart from this, there may be examples in which we are mainly interested to find the point in the parameter space at which the probability distribution has the largest value. In this situation the problem of parameter estimation becomes an optimization problem. In the present work we show that particle swarm optimization (PSO), which is an artificial intelligence inspired population based search procedure, can also be used for cosmological parameter estimation. Using PSO we were able to recover the best-fit Λ cold dark matter (LCDM) model parameters from the WMAP seven year data without using any prior guess value or any other property of the probability distribution of parameters like standard deviation, as is common in MCMC. We also report the results of an exercise in which we consider a binned primordial power spectrum (to increase the dimensionality of problem) and find that a power spectrum with features gives lower chi square than the standard power law. Since PSO does not sample the likelihood surface in a fair way, we follow a fitting procedure to find the spread of likelihood function around the best-fit point.
CHANDRA CLUSTER COSMOLOGY PROJECT III: COSMOLOGICAL PARAMETER CONSTRAINTS
International Nuclear Information System (INIS)
Vikhlinin, A.; Forman, W. R.; Jones, C.; Murray, S. S.; Kravtsov, A. V.; Burenin, R. A.; Voevodkin, A.; Ebeling, H.; Hornstrup, A.; Nagai, D.; Quintana, H.
2009-01-01
Chandra observations of large samples of galaxy clusters detected in X-rays by ROSAT provide a new, robust determination of the cluster mass functions at low and high redshifts. Statistical and systematic errors are now sufficiently small, and the redshift leverage sufficiently large for the mass function evolution to be used as a useful growth of a structure-based dark energy probe. In this paper, we present cosmological parameter constraints obtained from Chandra observations of 37 clusters with (z) = 0.55 derived from 400 deg 2 ROSAT serendipitous survey and 49 brightest z ∼ 0.05 clusters detected in the All-Sky Survey. Evolution of the mass function between these redshifts requires Ω Λ > 0 with a ∼5σ significance, and constrains the dark energy equation-of-state parameter to w 0 = -1.14 ± 0.21, assuming a constant w and a flat universe. Cluster information also significantly improves constraints when combined with other methods. Fitting our cluster data jointly with the latest supernovae, Wilkinson Microwave Anisotropy Probe, and baryonic acoustic oscillation measurements, we obtain w 0 = -0.991 ± 0.045 (stat) ±0.039 (sys), a factor of 1.5 reduction in statistical uncertainties, and nearly a factor of 2 improvement in systematics compared with constraints that can be obtained without clusters. The joint analysis of these four data sets puts a conservative upper limit on the masses of light neutrinos Σm ν M h and σ 8 from the low-redshift cluster mass function.
Exploring cosmic origins with CORE: Cosmological parameters
Di Valentino, E.; Brinckmann, T.; Gerbino, M.; Poulin, V.; Bouchet, F. R.; Lesgourgues, J.; Melchiorri, A.; Chluba, J.; Clesse, S.; Delabrouille, J.; Dvorkin, C.; Forastieri, F.; Galli, S.; Hooper, D. C.; Lattanzi, M.; Martins, C. J. A. P.; Salvati, L.; Cabass, G.; Caputo, A.; Giusarma, E.; Hivon, E.; Natoli, P.; Pagano, L.; Paradiso, S.; Rubiño-Martin, J. A.; Achúcarro, A.; Ade, P.; Allison, R.; Arroja, F.; Ashdown, M.; Ballardini, M.; Banday, A. J.; Banerji, R.; Bartolo, N.; Bartlett, J. G.; Basak, S.; Baumann, D.; de Bernardis, P.; Bersanelli, M.; Bonaldi, A.; Bonato, M.; Borrill, J.; Boulanger, F.; Bucher, M.; Burigana, C.; Buzzelli, A.; Cai, Z.-Y.; Calvo, M.; Carvalho, C. S.; Castellano, G.; Challinor, A.; Charles, I.; Colantoni, I.; Coppolecchia, A.; Crook, M.; D'Alessandro, G.; De Petris, M.; De Zotti, G.; Diego, J. M.; Errard, J.; Feeney, S.; Fernandez-Cobos, R.; Ferraro, S.; Finelli, F.; de Gasperis, G.; Génova-Santos, R. T.; González-Nuevo, J.; Grandis, S.; Greenslade, J.; Hagstotz, S.; Hanany, S.; Handley, W.; Hazra, D. K.; Hernández-Monteagudo, C.; Hervias-Caimapo, C.; Hills, M.; Kiiveri, K.; Kisner, T.; Kitching, T.; Kunz, M.; Kurki-Suonio, H.; Lamagna, L.; Lasenby, A.; Lewis, A.; Liguori, M.; Lindholm, V.; Lopez-Caniego, M.; Luzzi, G.; Maffei, B.; Martin, S.; Martinez-Gonzalez, E.; Masi, S.; Matarrese, S.; McCarthy, D.; Melin, J.-B.; Mohr, J. J.; Molinari, D.; Monfardini, A.; Negrello, M.; Notari, A.; Paiella, A.; Paoletti, D.; Patanchon, G.; Piacentini, F.; Piat, M.; Pisano, G.; Polastri, L.; Polenta, G.; Pollo, A.; Quartin, M.; Remazeilles, M.; Roman, M.; Ringeval, C.; Tartari, A.; Tomasi, M.; Tramonte, D.; Trappe, N.; Trombetti, T.; Tucker, C.; Väliviita, J.; van de Weygaert, R.; Van Tent, B.; Vennin, V.; Vermeulen, G.; Vielva, P.; Vittorio, N.; Young, K.; Zannoni, M.
2018-04-01
We forecast the main cosmological parameter constraints achievable with the CORE space mission which is dedicated to mapping the polarisation of the Cosmic Microwave Background (CMB). CORE was recently submitted in response to ESA's fifth call for medium-sized mission proposals (M5). Here we report the results from our pre-submission study of the impact of various instrumental options, in particular the telescope size and sensitivity level, and review the great, transformative potential of the mission as proposed. Specifically, we assess the impact on a broad range of fundamental parameters of our Universe as a function of the expected CMB characteristics, with other papers in the series focusing on controlling astrophysical and instrumental residual systematics. In this paper, we assume that only a few central CORE frequency channels are usable for our purpose, all others being devoted to the cleaning of astrophysical contaminants. On the theoretical side, we assume ΛCDM as our general framework and quantify the improvement provided by CORE over the current constraints from the Planck 2015 release. We also study the joint sensitivity of CORE and of future Baryon Acoustic Oscillation and Large Scale Structure experiments like DESI and Euclid. Specific constraints on the physics of inflation are presented in another paper of the series. In addition to the six parameters of the base ΛCDM, which describe the matter content of a spatially flat universe with adiabatic and scalar primordial fluctuations from inflation, we derive the precision achievable on parameters like those describing curvature, neutrino physics, extra light relics, primordial helium abundance, dark matter annihilation, recombination physics, variation of fundamental constants, dark energy, modified gravity, reionization and cosmic birefringence. In addition to assessing the improvement on the precision of individual parameters, we also forecast the post-CORE overall reduction of the allowed
Higgs field and cosmological parameters in the fractal quantum system
Directory of Open Access Journals (Sweden)
Abramov Valeriy
2017-01-01
Full Text Available For the fractal model of the Universe the relations of cosmological parameters and the Higgs field are established. Estimates of the critical density, the expansion and speed-up parameters of the Universe (the Hubble constant and the cosmological redshift; temperature and anisotropy of the cosmic microwave background radiation were performed.
Planck 2015 results: XIII. Cosmological parameters
DEFF Research Database (Denmark)
Ade, P. A R; Aghanim, N.; Arnaud, M.
2016-01-01
is constrained to w =-1.006 ± 0.045, consistent with the expected value for a cosmological constant. The standard big bang nucleosynthesis predictions for the helium and deuterium abundances for the best-fit Planck base ΛCDM cosmology are in excellent agreement with observations. We also constraints...... of the theory; for example, combining Planck observations with other astrophysical data we find Neff = 3.15 ± 0.23 for the effective number of relativistic degrees of freedom, consistent with the value Neff = 3.046 of the Standard Model of particle physics. The sum of neutrino masses is constrained to â'mν
Assumptions of the primordial spectrum and cosmological parameter estimation
International Nuclear Information System (INIS)
Shafieloo, Arman; Souradeep, Tarun
2011-01-01
The observables of the perturbed universe, cosmic microwave background (CMB) anisotropy and large structures depend on a set of cosmological parameters, as well as the assumed nature of primordial perturbations. In particular, the shape of the primordial power spectrum (PPS) is, at best, a well-motivated assumption. It is known that the assumed functional form of the PPS in cosmological parameter estimation can affect the best-fit-parameters and their relative confidence limits. In this paper, we demonstrate that a specific assumed form actually drives the best-fit parameters into distinct basins of likelihood in the space of cosmological parameters where the likelihood resists improvement via modifications to the PPS. The regions where considerably better likelihoods are obtained allowing free-form PPS lie outside these basins. In the absence of a preferred model of inflation, this raises a concern that current cosmological parameter estimates are strongly prejudiced by the assumed form of PPS. Our results strongly motivate approaches toward simultaneous estimation of the cosmological parameters and the shape of the primordial spectrum from upcoming cosmological data. It is equally important for theorists to keep an open mind towards early universe scenarios that produce features in the PPS. (paper)
SCoPE: an efficient method of Cosmological Parameter Estimation
International Nuclear Information System (INIS)
Das, Santanu; Souradeep, Tarun
2014-01-01
Markov Chain Monte Carlo (MCMC) sampler is widely used for cosmological parameter estimation from CMB and other data. However, due to the intrinsic serial nature of the MCMC sampler, convergence is often very slow. Here we present a fast and independently written Monte Carlo method for cosmological parameter estimation named as Slick Cosmological Parameter Estimator (SCoPE), that employs delayed rejection to increase the acceptance rate of a chain, and pre-fetching that helps an individual chain to run on parallel CPUs. An inter-chain covariance update is also incorporated to prevent clustering of the chains allowing faster and better mixing of the chains. We use an adaptive method for covariance calculation to calculate and update the covariance automatically as the chains progress. Our analysis shows that the acceptance probability of each step in SCoPE is more than 95% and the convergence of the chains are faster. Using SCoPE, we carry out some cosmological parameter estimations with different cosmological models using WMAP-9 and Planck results. One of the current research interests in cosmology is quantifying the nature of dark energy. We analyze the cosmological parameters from two illustrative commonly used parameterisations of dark energy models. We also asses primordial helium fraction in the universe can be constrained by the present CMB data from WMAP-9 and Planck. The results from our MCMC analysis on the one hand helps us to understand the workability of the SCoPE better, on the other hand it provides a completely independent estimation of cosmological parameters from WMAP-9 and Planck data
International Nuclear Information System (INIS)
Gomez Martinez, Silvina Paola; Madriz Aguilar, Jose Edgar; Bellini, Mauricio
2007-01-01
We study gravitational waves generated during the inflationary epoch in presence of a decaying cosmological parameter on a 5D geometrical background which is Riemann flat. Two examples are considered, one with a constant cosmological parameter and the second with a decreasing one
Learn-as-you-go acceleration of cosmological parameter estimates
International Nuclear Information System (INIS)
Aslanyan, Grigor; Easther, Richard; Price, Layne C.
2015-01-01
Cosmological analyses can be accelerated by approximating slow calculations using a training set, which is either precomputed or generated dynamically. However, this approach is only safe if the approximations are well understood and controlled. This paper surveys issues associated with the use of machine-learning based emulation strategies for accelerating cosmological parameter estimation. We describe a learn-as-you-go algorithm that is implemented in the Cosmo++ code and (1) trains the emulator while simultaneously estimating posterior probabilities; (2) identifies unreliable estimates, computing the exact numerical likelihoods if necessary; and (3) progressively learns and updates the error model as the calculation progresses. We explicitly describe and model the emulation error and show how this can be propagated into the posterior probabilities. We apply these techniques to the Planck likelihood and the calculation of ΛCDM posterior probabilities. The computation is significantly accelerated without a pre-defined training set and uncertainties in the posterior probabilities are subdominant to statistical fluctuations. We have obtained a speedup factor of 6.5 for Metropolis-Hastings and 3.5 for nested sampling. Finally, we discuss the general requirements for a credible error model and show how to update them on-the-fly
García-Bellido, J
2015-01-01
In these lectures I review the present status of the so-called Standard Cosmological Model, based on the hot Big Bang Theory and the Inflationary Paradigm. I will make special emphasis on the recent developments in observational cosmology, mainly the acceleration of the universe, the precise measurements of the microwave background anisotropies, and the formation of structure like galaxies and clusters of galaxies from tiny primordial fluctuations generated during inflation.
Stochastic evolution of cosmological parameters in the early universe
Indian Academy of Sciences (India)
We develop a stochastic formulation of cosmology in the early universe, after considering the scatter in the redshift-apparent magnitude diagram in the early epochs as an observational evidence for the non-deterministic evolution of early universe. We consider the stochastic evolution of density parameter in the early ...
Data-constrained reionization and its effects on cosmological parameters
International Nuclear Information System (INIS)
Pandolfi, S.; Ferrara, A.; Choudhury, T. Roy; Mitra, S.; Melchiorri, A.
2011-01-01
We perform an analysis of the recent WMAP7 data considering physically motivated and viable reionization scenarios with the aim of assessing their effects on cosmological parameter determinations. The main novelties are: (i) the combination of cosmic microwave background data with astrophysical results from quasar absorption line experiments; (ii) the joint variation of both the cosmological and astrophysical [governing the evolution of the free electron fraction x e (z)] parameters. Including a realistic, data-constrained reionization history in the analysis induces appreciable changes in the cosmological parameter values deduced through a standard WMAP7 analysis. Particularly noteworthy are the variations in Ω b h 2 =0.02258 -0.00056 +0.00057 [WMAP7 (Sudden)] vs Ω b h 2 =0.02183±0.00054[WMAP7+ASTRO (CF)] and the new constraints for the scalar spectral index, for which WMAP7+ASTRO (CF) excludes the Harrison-Zel'dovich value n s =1 at >3σ. Finally, the electron-scattering optical depth value is considerably decreased with respect to the standard WMAP7, i.e. τ e =0.080±0.012. We conclude that the inclusion of astrophysical data sets, allowing to robustly constrain the reionization history, in the extraction procedure of cosmological parameters leads to relatively important differences in the final determination of their values.
Constraining dynamical neutrino mass generation with cosmological data
Energy Technology Data Exchange (ETDEWEB)
Koksbang, S.M.; Hannestad, S., E-mail: koksbang@phys.au.dk, E-mail: sth@phys.au.dk [Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark)
2017-09-01
We study models in which neutrino masses are generated dynamically at cosmologically late times. Our study is purely phenomenological and parameterized in terms of three effective parameters characterizing the redshift of mass generation, the width of the transition region, and the present day neutrino mass. We also study the possibility that neutrinos become strongly self-interacting at the time where the mass is generated. We find that in a number of cases, models with large present day neutrino masses are allowed by current CMB, BAO and supernova data. The increase in the allowed mass range makes it possible that a non-zero neutrino mass could be measured in direct detection experiments such as KATRIN. Intriguingly we also find that there are allowed models in which neutrinos become strongly self-interacting around the epoch of recombination.
Cosmological parameters from large scale structure - geometric versus shape information
Hamann, Jan; Lesgourgues, Julien; Rampf, Cornelius; Wong, Yvonne Y Y
2010-01-01
The matter power spectrum as derived from large scale structure (LSS) surveys contains two important and distinct pieces of information: an overall smooth shape and the imprint of baryon acoustic oscillations (BAO). We investigate the separate impact of these two types of information on cosmological parameter estimation, and show that for the simplest cosmological models, the broad-band shape information currently contained in the SDSS DR7 halo power spectrum (HPS) is by far superseded by geometric information derived from the baryonic features. An immediate corollary is that contrary to popular beliefs, the upper limit on the neutrino mass m_\
The Atacama Cosmology Telescope: Cosmological Parameters from the 2008 Power Spectrum
Dunkley, J.; Hlozek, R.; Sievers, J.; Acquaviva, V.; Ade, P. A. R.; Aguirre, P.; Amiri, M.; Appel, J. W.; Barrientos, L. F.; Battistelli, E. S.;
2011-01-01
We present cosmological parameters derived from the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz and 218 GHz over 296 deg(exp 2) with the Atacama Cosmology Telescope (ACT) during its 2008 season. ACT measures fluctuations at scales 500 cosmological parameters from the less contaminated 148 GHz spectrum, marginalizing over SZ and source power. The ACDM cosmological model is a good fit to the data (chi square/dof = 29/46), and ACDM parameters estimated from ACT+Wilkinson Microwave Anisotropy Probe (WMAP) are consistent with the seven-year WMAP limits, with scale invariant n(sub s) = 1 excluded at 99.7% confidence level (CL) (3 sigma). A model with no CMB lensing is disfavored at 2.8 sigma. By measuring the third to seventh acoustic peaks, and probing the Silk damping regime, the ACT data improve limits on cosmological parameters that affect the small-scale CMB power. The ACT data combined with WMAP give a 6 sigma detection of primordial helium, with Y(sub p) = 0.313 +/- 0.044, and a 4 sigma detection of relativistic species, assumed to be neutrinos, with N(sub eff) = 5.3 +/- 1.3 (4.6 +/- 0.8 with BAO+H(sub 0) data). From the CMB alone the running of the spectral index is constrained to be d(sub s) / d ln k = -0,034 +/- 0,018, the limit on the tensor-to-scalar ratio is r < 0,25 (95% CL), and the possible contribution of Nambu cosmic strings to the power spectrum is constrained to string tension G(sub mu) < 1.6 x 10(exp -7) (95% CL),
Planck 2013 results. XVI. Cosmological parameters
DEFF Research Database (Denmark)
Planck Collaboration,; Ade, P. A. R.; Aghanim, N.
2013-01-01
parameters to high precision. We find a low value of the Hubble constant, H0=67.3+/-1.2 km/s/Mpc and a high value of the matter density parameter, Omega_m=0.315+/-0.017 (+/-1 sigma errors) in excellent agreement with constraints from baryon acoustic oscillation (BAO) surveys. Including curvature, we find...... over standard LCDM. The deviation of the scalar spectral index from unity is insensitive to the addition of tensor modes and to changes in the matter content of the Universe. We find a 95% upper limit of r...
Impact of relativistic effects on cosmological parameter estimation
Lorenz, Christiane S.; Alonso, David; Ferreira, Pedro G.
2018-01-01
Future surveys will access large volumes of space and hence very long wavelength fluctuations of the matter density and gravitational field. It has been argued that the set of secondary effects that affect the galaxy distribution, relativistic in nature, will bring new, complementary cosmological constraints. We study this claim in detail by focusing on a subset of wide-area future surveys: Stage-4 cosmic microwave background experiments and photometric redshift surveys. In particular, we look at the magnification lensing contribution to galaxy clustering and general-relativistic corrections to all observables. We quantify the amount of information encoded in these effects in terms of the tightening of the final cosmological constraints as well as the potential bias in inferred parameters associated with neglecting them. We do so for a wide range of cosmological parameters, covering neutrino masses, standard dark-energy parametrizations and scalar-tensor gravity theories. Our results show that, while the effect of lensing magnification to number counts does not contain a significant amount of information when galaxy clustering is combined with cosmic shear measurements, this contribution does play a significant role in biasing estimates on a host of parameter families if unaccounted for. Since the amplitude of the magnification term is controlled by the slope of the source number counts with apparent magnitude, s (z ), we also estimate the accuracy to which this quantity must be known to avoid systematic parameter biases, finding that future surveys will need to determine s (z ) to the ˜5 %- 10 % level. On the contrary, large-scale general-relativistic corrections are irrelevant both in terms of information content and parameter bias for most cosmological parameters but significant for the level of primordial non-Gaussianity.
Improved constraints on cosmological parameters from SNIa data
International Nuclear Information System (INIS)
March, M.C.; Trotta, R.
2011-02-01
We present a new method based on a Bayesian hierarchical model to extract constraints on cosmological parameters from SNIa data obtained with the SALT-II lightcurve fitter. We demonstrate with simulated data sets that our method delivers considerably tighter statistical constraints on the cosmological parameters and that it outperforms the usual χ 2 approach 2/3 of the times. As a further benefit, a full posterior probability distribution for the dispersion of the intrinsic magnitude of SNe is obtained. We apply this method to recent SNIa data and find that it improves statistical constraints on cosmological parameters from SNIa data alone by about 40% w.r.t. the standard approach. From the combination of SNIa, CMB and BAO data we obtain Ω m =0.29±0.01, Ω Λ =0.72±0.01 (assuming w=-1) and Ω m =0.28±0.01, w=-0.90±0.04 (assuming flatness; statistical uncertainties only). We constrain the intrinsic dispersion of the B-band magnitude of the SNIa population, obtaining σ μ int =0.13±0.01 [mag]. Applications to systematic uncertainties will be discussed in a forthcoming paper. (orig.)
Improved constraints on cosmological parameters from SNIa data
Energy Technology Data Exchange (ETDEWEB)
March, M.C.; Trotta, R. [Imperial College, London (United Kingdom). Astrophysics Group; Berkes, P. [Brandeis Univ., Waltham (United States). Volen Centre for Complex Systems; Starkman, G.D. [Case Western Reserve Univ., Cleveland (United States). CERCA and Dept. of Physics; Vaudrevange, P.M. [Case Western Reserve Univ., Cleveland (United States). CERCA and Dept. of Physics; Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2011-02-15
We present a new method based on a Bayesian hierarchical model to extract constraints on cosmological parameters from SNIa data obtained with the SALT-II lightcurve fitter. We demonstrate with simulated data sets that our method delivers considerably tighter statistical constraints on the cosmological parameters and that it outperforms the usual {chi}{sup 2} approach 2/3 of the times. As a further benefit, a full posterior probability distribution for the dispersion of the intrinsic magnitude of SNe is obtained. We apply this method to recent SNIa data and find that it improves statistical constraints on cosmological parameters from SNIa data alone by about 40% w.r.t. the standard approach. From the combination of SNIa, CMB and BAO data we obtain {omega}{sub m}=0.29{+-}0.01, {omega}{sub {lambda}}=0.72{+-}0.01 (assuming w=-1) and {omega}{sub m}=0.28{+-}0.01, w=-0.90{+-}0.04 (assuming flatness; statistical uncertainties only). We constrain the intrinsic dispersion of the B-band magnitude of the SNIa population, obtaining {sigma}{sub {mu}}{sup int}=0.13{+-}0.01 [mag]. Applications to systematic uncertainties will be discussed in a forthcoming paper. (orig.)
Testing general relativity at cosmological scales: Implementation and parameter correlations
International Nuclear Information System (INIS)
Dossett, Jason N.; Ishak, Mustapha; Moldenhauer, Jacob
2011-01-01
The testing of general relativity at cosmological scales has become a possible and timely endeavor that is not only motivated by the pressing question of cosmic acceleration but also by the proposals of some extensions to general relativity that would manifest themselves at large scales of distance. We analyze here correlations between modified gravity growth parameters and some core cosmological parameters using the latest cosmological data sets including the refined Cosmic Evolution Survey 3D weak lensing. We provide the parametrized modified growth equations and their evolution. We implement known functional and binning approaches, and propose a new hybrid approach to evolve the modified gravity parameters in redshift (time) and scale. The hybrid parametrization combines a binned redshift dependence and a smooth evolution in scale avoiding a jump in the matter power spectrum. The formalism developed to test the consistency of current and future data with general relativity is implemented in a package that we make publicly available and call ISiTGR (Integrated Software in Testing General Relativity), an integrated set of modified modules for the publicly available packages CosmoMC and CAMB, including a modified version of the integrated Sachs-Wolfe-galaxy cross correlation module of Ho et al. and a new weak-lensing likelihood module for the refined Hubble Space Telescope Cosmic Evolution Survey weak gravitational lensing tomography data. We obtain parameter constraints and correlation coefficients finding that modified gravity parameters are significantly correlated with σ 8 and mildly correlated with Ω m , for all evolution methods. The degeneracies between σ 8 and modified gravity parameters are found to be substantial for the functional form and also for some specific bins in the hybrid and binned methods indicating that these degeneracies will need to be taken into consideration when using future high precision data.
GRID-BASED EXPLORATION OF COSMOLOGICAL PARAMETER SPACE WITH SNAKE
International Nuclear Information System (INIS)
Mikkelsen, K.; Næss, S. K.; Eriksen, H. K.
2013-01-01
We present a fully parallelized grid-based parameter estimation algorithm for investigating multidimensional likelihoods called Snake, and apply it to cosmological parameter estimation. The basic idea is to map out the likelihood grid-cell by grid-cell according to decreasing likelihood, and stop when a certain threshold has been reached. This approach improves vastly on the 'curse of dimensionality' problem plaguing standard grid-based parameter estimation simply by disregarding grid cells with negligible likelihood. The main advantages of this method compared to standard Metropolis-Hastings Markov Chain Monte Carlo methods include (1) trivial extraction of arbitrary conditional distributions; (2) direct access to Bayesian evidences; (3) better sampling of the tails of the distribution; and (4) nearly perfect parallelization scaling. The main disadvantage is, as in the case of brute-force grid-based evaluation, a dependency on the number of parameters, N par . One of the main goals of the present paper is to determine how large N par can be, while still maintaining reasonable computational efficiency; we find that N par = 12 is well within the capabilities of the method. The performance of the code is tested by comparing cosmological parameters estimated using Snake and the WMAP-7 data with those obtained using CosmoMC, the current standard code in the field. We find fully consistent results, with similar computational expenses, but shorter wall time due to the perfect parallelization scheme
GRID-BASED EXPLORATION OF COSMOLOGICAL PARAMETER SPACE WITH SNAKE
Energy Technology Data Exchange (ETDEWEB)
Mikkelsen, K.; Næss, S. K.; Eriksen, H. K., E-mail: kristin.mikkelsen@astro.uio.no [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, NO-0315 Oslo (Norway)
2013-11-10
We present a fully parallelized grid-based parameter estimation algorithm for investigating multidimensional likelihoods called Snake, and apply it to cosmological parameter estimation. The basic idea is to map out the likelihood grid-cell by grid-cell according to decreasing likelihood, and stop when a certain threshold has been reached. This approach improves vastly on the 'curse of dimensionality' problem plaguing standard grid-based parameter estimation simply by disregarding grid cells with negligible likelihood. The main advantages of this method compared to standard Metropolis-Hastings Markov Chain Monte Carlo methods include (1) trivial extraction of arbitrary conditional distributions; (2) direct access to Bayesian evidences; (3) better sampling of the tails of the distribution; and (4) nearly perfect parallelization scaling. The main disadvantage is, as in the case of brute-force grid-based evaluation, a dependency on the number of parameters, N{sub par}. One of the main goals of the present paper is to determine how large N{sub par} can be, while still maintaining reasonable computational efficiency; we find that N{sub par} = 12 is well within the capabilities of the method. The performance of the code is tested by comparing cosmological parameters estimated using Snake and the WMAP-7 data with those obtained using CosmoMC, the current standard code in the field. We find fully consistent results, with similar computational expenses, but shorter wall time due to the perfect parallelization scheme.
The Atacama Cosmology Telescope: cosmological parameters from three seasons of data
International Nuclear Information System (INIS)
Sievers, Jonathan L.; Appel, John William; Hlozek, Renée A.; Nolta, Michael R.; Battaglia, Nick; Bond, J. Richard; Acquaviva, Viviana; Addison, Graeme E.; Amiri, Mandana; Battistelli, Elia S.; Burger, Bryce; Ade, Peter A. R.; Aguirre, Paula; Barrientos, L. Felipe; Brown, Ben; Calabrese, Erminia; Chervenak, Jay; Crichton, Devin; Das, Sudeep; Devlin, Mark J.
2013-01-01
We present constraints on cosmological and astrophysical parameters from high-resolution microwave background maps at 148 GHz and 218 GHz made by the Atacama Cosmology Telescope (ACT) in three seasons of observations from 2008 to 2010. A model of primary cosmological and secondary foreground parameters is fit to the map power spectra and lensing deflection power spectrum, including contributions from both the thermal Sunyaev-Zeldovich (tSZ) effect and the kinematic Sunyaev-Zeldovich (kSZ) effect, Poisson and correlated anisotropy from unresolved infrared sources, radio sources, and the correlation between the tSZ effect and infrared sources. The power ℓ 2 C ℓ /2π of the thermal SZ power spectrum at 148 GHz is measured to be 3.4±1.4 μK 2 at ℓ = 3000, while the corresponding amplitude of the kinematic SZ power spectrum has a 95% confidence level upper limit of 8.6 μK 2 . Combining ACT power spectra with the WMAP 7-year temperature and polarization power spectra, we find excellent consistency with the LCDM model. We constrain the number of effective relativistic degrees of freedom in the early universe to be N eff = 2.79±0.56, in agreement with the canonical value of N eff = 3.046 for three massless neutrinos. We constrain the sum of the neutrino masses to be Σm ν < 0.39 eV at 95% confidence when combining ACT and WMAP 7-year data with BAO and Hubble constant measurements. We constrain the amount of primordial helium to be Y p = 0.225±0.034, and measure no variation in the fine structure constant α since recombination, with α/α 0 = 1.004±0.005. We also find no evidence for any running of the scalar spectral index, dn s /dln k = −0.004±0.012
Measuring Cosmological Parameters with Photometrically Classified Pan-STARRS Supernovae
Jones, David; Scolnic, Daniel; Riess, Adam; Rest, Armin; Kirshner, Robert; Berger, Edo; Kessler, Rick; Pan, Yen-Chen; Foley, Ryan; Chornock, Ryan; Ortega, Carolyn; Challis, Peter; Burgett, William; Chambers, Kenneth; Draper, Peter; Flewelling, Heather; Huber, Mark; Kaiser, Nick; Kudritzki, Rolf; Metcalfe, Nigel; Tonry, John; Wainscoat, Richard J.; Waters, Chris; Gall, E. E. E.; Kotak, Rubina; McCrum, Matt; Smartt, Stephen; Smith, Ken
2018-01-01
We use nearly 1,200 supernovae (SNe) from Pan-STARRS and ~200 low-z (z energy equation of state parameter w to be -0.986±0.058 (stat+sys). If we allow w to evolve with redshift as w(a) = w0 + wa(1-a), we find w0 = -0.923±0.148 and wa = -0.404±0.797. These results are consistent with measurements of cosmological parameters from the JLA and from a new analysis of 1049 spectroscopically confirmed SNe Ia (Scolnic et al. 2017). We try four different photometric classification priors for Pan-STARRS SNe and two alternate ways of modeling the CC SN contamination, finding that none of these variants gives a w that differs by more than 1% from the baseline measurement. The systematic uncertainty on w due to marginalizing over the CC SN contamination, σwCC = 0.019, is approximately equal to the photometric calibration uncertainty and is lower than the systematic uncertainty in the SN\\,Ia dispersion model (σwdisp = 0.024). Our data provide one of the best current constraints on w, demonstrating that samples with ~5% CC SN contamination can give competitive cosmological constraints when the contaminating distribution is marginalized over in a Bayesian framework.
DIRECTIONAL DEPENDENCE OF ΛCDM COSMOLOGICAL PARAMETERS
International Nuclear Information System (INIS)
Axelsson, M.; Fantaye, Y.; Hansen, F. K.; Eriksen, H. K.; Banday, A. J.; Gorski, K. M.
2013-01-01
We study hemispherical power asymmetry in the Wilkinson Microwave Anisotropy Probe 9 yr data. We analyze the combined V- and W-band sky maps, after application of the KQ85 mask, and find that the asymmetry is statistically significant at the 3.4σ confidence level for l = 2-600, where the data are signal-dominated, with a preferred asymmetry direction (l, b) = (227, –27). Individual asymmetry axes estimated from six independent multipole ranges are all consistent with this direction. Subsequently, we estimate cosmological parameters on different parts of the sky and show that the parameters A s , n s , and Ω b are the most sensitive to this power asymmetry. In particular, for the two opposite hemispheres aligned with the preferred asymmetry axis, we find n s = 0.959 ± 0.022 and n s = 0.989 ± 0.024, respectively
Energy Technology Data Exchange (ETDEWEB)
Huang, Qing-Guo; Wang, Ke, E-mail: huangqg@itp.ac.cn, E-mail: wangke@itp.ac.cn [CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Zhong Guan Cun East Street 55 #, Beijing 100190 (China)
2017-07-01
The early reionization (ERE) is supposed to be a physical process which happens after recombination, but before the instantaneous reionization caused by the first generation of stars. We investigate the effect of the ERE on the temperature and polarization power spectra of cosmic microwave background (CMB), and adopt principal components analysis (PCA) to model-independently reconstruct the ionization history during the ERE. In addition, we also discuss how the ERE affects the cosmological parameter estimates, and find that the ERE does not impose any significant influences on the tensor-to-scalar ratio r and the neutrino mass at the sensitivities of current experiments. The better CMB polarization data can be used to give a tighter constraint on the ERE and might be important for more precisely constraining cosmological parameters in the future.
International Nuclear Information System (INIS)
Lusset, Vincent
2006-01-01
The Supernova Legacy Survey is a second generation experiment for the measurement of cosmological parameters using type-la supernovae. Il follows the discovery of the acceleration of the expansion of the Universe, attributed to an unknown 'dark energy'. This thesis presents a type-la supernovae search using an offline analysis of SNLS data. It makes it possible to detect the supernovae that were missed online and to study possible selection biases. One of its principal characteristics is that it uses entirely automatic selection criteria. This type of automated offline analysis had never been carried out before for data reaching this redshift. This analysis enabled us to discover 73 additional SNIa candidates compared to those identified in the real time analysis on the same data, representing an increase of more than 50% of the number of supernovae. The final Hubble diagram contains 262 SNIa which gives us, for a flat ACDM model, the following values for the cosmological parameters: Ω_M = 0,31 ± 0,028 (stat) ± 0,036 (syst) et Ω_A = 0,69. This offline analysis of SNLS data opens new horizons, both by checking for possible biases in current measurements of cosmological parameters by supernovae experiments and by preparing the third generation experiments, on the ground or in space, which will detect thousands of SNIa. (author) [fr
Big Bang Nucleosynthesis and Cosmological Constraints on Neutrino Oscillation Parameters
Kirilova, Daniela P; Kirilova, Daniela; Chizhov, Mihail
2001-01-01
We present a review of cosmological nucleosynthesis (CN) with neutrino oscillations, discussing the different effects of oscillations on CN, namely: increase of the effective degrees of freedom during CN, spectrum distortion of the oscillating neutrinos, neutrino number density depletion, and growth of neutrino-antineutrino asymmetry due to active-sterile oscillations. We discuss the importance of these effects for the primordial yield of helium-4. Primordially produced He-4 value is obtained in a selfconsistent study of the nucleons and the oscillating neutrinos. The effects of spectrum distortion, depletion and neutrino-antineutrino asymmetry growth on helium-4 production are explicitly calculated. An update of the cosmological constraints on active-sterile neutrino oscillations parameters is presented, giving the values: delta m^2 sin^8 (2 theta) 0, and |delta m^2| < 8.2 x 10^{-10} eV^2 at large mixing angles for delta m^2 < 0. According to these constraints, besides the active-sterile LMA solution,...
The Atacama Cosmology Telescope: Cosmological Parameters from Three Seasons of Data
Seivers, Jonathan L.; Hlozek, Renee A.; Nolta, Michael R.; Acquaviva, Viviana; Addison, Graeme E.; Ade, Peter A. R.; Aguirre, Paula; Amiri, Mandana; Appel, John W.; Barrientos, L. Felipe;
2013-01-01
We present constraints on cosmological and astrophysical parameters from highresolution microwave background maps at 148 GHz and 218 GHz made by the Atacama Cosmology Telescope (ACT) in three seasons of observations from 2008 to 2010. A model of primary cosmological and secondary foreground parameters is fit to the map power spectra and lensing deflection power spectrum, including contributions from both the thermal Sunyaev-Zeldovich (tSZ) effect and the kinematic Sunyaev-Zeldovich (kSZ) effect, Poisson and correlated anisotropy from unresolved infrared sources, radio sources, and the correlation between the tSZ effect and infrared sources. The power l(sup 2)C(sub l)/2pi of the thermal SZ power spectrum at 148 GHz is measured to be 3.4 +/- 1.4 micro-K(sup 2) at l = 3000, while the corresponding amplitude of the kinematic SZ power spectrum has a 95% confidence level upper limit of 8.6 micro-K(sup 2). Combining ACT power spectra with the WMAP 7-year temperature and polarization power spectra, we find excellent consistency with the LCDM model. We constrain the number of effective relativistic degrees of freedom in the early universe to be N(sub eff) = 2.79 +/- 0.56, in agreement with the canonical value of N(sub eff) = 3.046 for three massless neutrinos. We constrain the sum of the neutrino masses to be sigma(m?) is less than 0.39 eV at 95% confidence when combining ACT and WMAP 7-year data with BAO and Hubble constant measurements. We constrain the amount of primordial helium to be Y(sub p) = 0.225 +/- 0.034, and measure no variation in the fine structure constant alpha since recombination, with alpha/alpha(sub 0) = 1.004 +/- 0.005. We also find no evidence for any running of the scalar spectral index, derivative(n(sub s))/derivative(ln k) = -0.004 +/- 0.012.
Cosmological Parameters and Hyper-Parameters: The Hubble Constant from Boomerang and Maxima
Lahav, Ofer
Recently several studies have jointly analysed data from different cosmological probes with the motivation of estimating cosmological parameters. Here we generalise this procedure to allow freedom in the relative weights of various probes. This is done by including in the joint likelihood function a set of `Hyper-Parameters', which are dealt with using Bayesian considerations. The resulting algorithm, which assumes uniform priors on the log of the Hyper-Parameters, is very simple to implement. We illustrate the method by estimating the Hubble constant H0 from different sets of recent CMB experiments (including Saskatoon, Python V, MSAM1, TOCO, Boomerang and Maxima). The approach can be generalised for a combination of cosmic probes, and for other priors on the Hyper-Parameters. Reference: Lahav, Bridle, Hobson, Lasenby & Sodre, 2000, MNRAS, in press (astro-ph/9912105)
Cosmological Parameter Estimation with Large Scale Structure Observations
Di Dio, Enea; Durrer, Ruth; Lesgourgues, Julien
2014-01-01
We estimate the sensitivity of future galaxy surveys to cosmological parameters, using the redshift dependent angular power spectra of galaxy number counts, $C_\\ell(z_1,z_2)$, calculated with all relativistic corrections at first order in perturbation theory. We pay special attention to the redshift dependence of the non-linearity scale and present Fisher matrix forecasts for Euclid-like and DES-like galaxy surveys. We compare the standard $P(k)$ analysis with the new $C_\\ell(z_1,z_2)$ method. We show that for surveys with photometric redshifts the new analysis performs significantly better than the $P(k)$ analysis. For spectroscopic redshifts, however, the large number of redshift bins which would be needed to fully profit from the redshift information, is severely limited by shot noise. We also identify surveys which can measure the lensing contribution and we study the monopole, $C_0(z_1,z_2)$.
Constraining cosmological parameters with observational data including weak lensing effects
Energy Technology Data Exchange (ETDEWEB)
Li Hong [Institute of High Energy Physics, Chinese Academy of Science, PO Box 918-4, Beijing 100049 (China); Theoretical Physics Center for Science Facilities (TPCSF), Chinese Academy of Science (China)], E-mail: hongli@mail.ihep.ac.cn; Liu Jie [Institute of High Energy Physics, Chinese Academy of Science, PO Box 918-4, Beijing 100049 (China); Xia Junqing [Scuola Internazionale Superiore di Studi Avanzati, Via Beirut 2-4, I-34014 Trieste (Italy); Sun Lei; Fan Zuhui [Department of Astronomy, School of Physics, Peking University, Beijing 100871 (China); Tao Charling; Tilquin, Andre [Centre de Physique des Particules de Marseille, CNRS/IN2P3-Luminy and Universite de la Mediterranee, Case 907, F-13288 Marseille Cedex 9 (France); Zhang Xinmin [Institute of High Energy Physics, Chinese Academy of Science, PO Box 918-4, Beijing 100049 (China); Theoretical Physics Center for Science Facilities (TPCSF), Chinese Academy of Science (China)
2009-05-11
In this Letter, we study the cosmological implications of the 100 square degree Weak Lensing survey (the CFHTLS-Wide, RCS, VIRMOS-DESCART and GaBoDS surveys). We combine these weak lensing data with the cosmic microwave background (CMB) measurements from the WMAP5, BOOMERanG, CBI, VSA, ACBAR, the SDSS LRG matter power spectrum and the Type Ia Supernoave (SNIa) data with the 'Union' compilation (307 sample), using the Markov Chain Monte Carlo method to determine the cosmological parameters, such as the equation-of-state (EoS) of dark energy w, the density fluctuation amplitude {sigma}{sub 8}, the total neutrino mass {sigma}m{sub {nu}} and the parameters associated with the power spectrum of the primordial fluctuations. Our results show that the {lambda}CDM model remains a good fit to all of these data. In a flat universe, we obtain a tight limit on the constant EoS of dark energy, w=-0.97{+-}0.041 (1{sigma}). For the dynamical dark energy model with time evolving EoS parameterized as w{sub de}(a)=w{sub 0}+w{sub a}(1-a), we find that the best-fit values are w{sub 0}=-1.064 and w{sub a}=0.375, implying the mildly preference of Quintom model whose EoS gets across the cosmological constant boundary during evolution. Regarding the total neutrino mass limit, we obtain the upper limit, {sigma}m{sub {nu}}<0.471 eV (95% C.L.) within the framework of the flat {lambda}CDM model. Due to the obvious degeneracies between the neutrino mass and the EoS of dark energy model, this upper limit will be relaxed by a factor of 2 in the framework of dynamical dark energy models. Assuming that the primordial fluctuations are adiabatic with a power law spectrum, within the {lambda}CDM model, we find that the upper limit on the ratio of the tensor to scalar is r<0.35 (95% C.L.) and the inflationary models with the slope n{sub s}{>=}1 are excluded at more than 2{sigma} confidence level. In this Letter we pay particular attention to the contribution from the weak lensing data and
Entropy generation in cosmological particle creation
International Nuclear Information System (INIS)
Castagnino, M.A.; Gaioli, F.H.; Sforza, D.M.
1996-01-01
A very simplified model of the Universe is considered in order to propose an alternative approach to the irreversible evolution of the Universe at very early times. The entropy generation at the quantum stage can be thought of as a consequence of an instability of the system. Then particle creation arises from this instability
International Nuclear Information System (INIS)
Contopoulos, G.; Kotsakis, D.
1987-01-01
An extensive first part on a wealth of observational results relevant to cosmology lays the foundation for the second and central part of the book; the chapters on general relativity, the various cosmological theories, and the early universe. The authors present in a complete and almost non-mathematical way the ideas and theoretical concepts of modern cosmology including the exciting impact of high-energy particle physics, e.g. in the concept of the ''inflationary universe''. The final part addresses the deeper implications of cosmology, the arrow of time, the universality of physical laws, inflation and causality, and the anthropic principle
Determining cosmological parameters with the latest observational data
International Nuclear Information System (INIS)
Xia Junqing; Li Hong; Zhao Gongbo; Zhang Xinmin
2008-01-01
In this paper, we combine the latest observational data, including the WMAP five-year data (WMAP5), BOOMERanG, CBI, VSA, ACBAR, as well as the baryon acoustic oscillations (BAO) and type Ia supernovae (SN) ''union'' compilation (307 sample), and use the Markov Chain Monte Carlo method to determine the cosmological parameters, such as the equation of state (EoS) of dark energy, the curvature of the universe, the total neutrino mass, and the parameters associated with the power spectrum of primordial fluctuations. In a flat universe, we obtain the tight limit on the constant EoS of dark energy as w=-0.977±0.056(stat)±0.057(sys). For the dynamical dark energy models with the time evolving EoS parametrized as w de (a)=w 0 +w 1 (1-a), we find that the best-fit values are w 0 =-1.08 and w 1 =0.368, while the ΛCDM model remains a good fit to the current data. For the curvature of the universe Ω k , our results give -0.012 k de =-1. When considering the dynamics of dark energy, the flat universe is still a good fit to the current data, -0.015 k s ≥1 are excluded at more than 2σ confidence level. However, in the framework of dynamical dark energy models, the allowed region in the parameter space of (n s ,r) is enlarged significantly. Finally, we find no strong evidence for the large running of the spectral index.
A small cosmological constant and backreaction of non-finetuned parameters
International Nuclear Information System (INIS)
Krause, Axel
2003-01-01
We include the backreaction on warped geometry induced by non-finetuned parameters in a two domain-wall set-up to obtain an exponentially small Cosmological Constant Λ4. The mechanism to suppress the Cosmological Constant involves one classical fine-tuning as compared to an infinity of finetunings at the quantum level in standard D = 4 field theory. (author)
Cai, Rong-Gen; Yang, Tao
2017-02-01
We investigate the constraint ability of the gravitational wave (GW) as the standard siren on the cosmological parameters by using the third-generation gravitational wave detector: the Einstein Telescope. The binary merger of a neutron with either a neutron or black hole is hypothesized to be the progenitor of a short and intense burst of γ rays; some fraction of those binary mergers could be detected both through electromagnetic radiation and gravitational waves. Thus we can determine both the luminosity distance and redshift of the source separately. We simulate the luminosity distances and redshift measurements from 100 to 1000 GW events. We use two different algorithms to constrain the cosmological parameters. For the Hubble constant H0 and dark matter density parameter Ωm, we adopt the Markov chain Monte Carlo approach. We find that with about 500-600 GW events we can constrain the Hubble constant with an accuracy comparable to Planck temperature data and Planck lensing combined results, while for the dark matter density, GWs alone seem not able to provide the constraints as good as for the Hubble constant; the sensitivity of 1000 GW events is a little lower than that of Planck data. It should require more than 1000 events to match the Planck sensitivity. Yet, for analyzing the more complex dynamical property of dark energy, i.e., the equation of state w , we adopt a new powerful nonparametric method: the Gaussian process. We can reconstruct w directly from the observational luminosity distance at every redshift. In the low redshift region, we find that about 700 GW events can give the constraints of w (z ) comparable to the constraints of a constant w by Planck data with type-Ia supernovae. Those results show that GWs as the standard sirens to probe the cosmological parameters can provide an independent and complementary alternative to current experiments.
Cosmological parameters from CMB and other data: A Monte Carlo approach
International Nuclear Information System (INIS)
Lewis, Antony; Bridle, Sarah
2002-01-01
We present a fast Markov chain Monte Carlo exploration of cosmological parameter space. We perform a joint analysis of results from recent cosmic microwave background (CMB) experiments and provide parameter constraints, including σ 8 , from the CMB independent of other data. We next combine data from the CMB, HST Key Project, 2dF galaxy redshift survey, supernovae type Ia and big-bang nucleosynthesis. The Monte Carlo method allows the rapid investigation of a large number of parameters, and we present results from 6 and 9 parameter analyses of flat models, and an 11 parameter analysis of non-flat models. Our results include constraints on the neutrino mass (m ν < or approx. 3 eV), equation of state of the dark energy, and the tensor amplitude, as well as demonstrating the effect of additional parameters on the base parameter constraints. In a series of appendixes we describe the many uses of importance sampling, including computing results from new data and accuracy correction of results generated from an approximate method. We also discuss the different ways of converting parameter samples to parameter constraints, the effect of the prior, assess the goodness of fit and consistency, and describe the use of analytic marginalization over normalization parameters
Vittorio, Nicola
2018-01-01
Modern cosmology has changed significantly over the years, from the discovery to the precision measurement era. The data now available provide a wealth of information, mostly consistent with a model where dark matter and dark energy are in a rough proportion of 3:7. The time is right for a fresh new textbook which captures the state-of-the art in cosmology. Written by one of the world's leading cosmologists, this brand new, thoroughly class-tested textbook provides graduate and undergraduate students with coverage of the very latest developments and experimental results in the field. Prof. Nicola Vittorio shows what is meant by precision cosmology, from both theoretical and observational perspectives.
Cosmological parameters from pre-planck cosmic microwave background measurements
Calabrese, E.; Hlozek, R.; Battaglia, N.; Battistelli, E.; Bond, J.; Chluba, J.; Crichton, D.; Das, S.; Devlin, M.; Dunkley, J.; Dünner, R.; Farhang, M.; Gralla, M.; Hajian, A.; Halpern, M.; Hasselfield, M.; Hincks, A.; Irwin, K.; Kosowsky, A.; Louis, T.; Marriage, T.; Moodley, K.; Newburgh, L.; Niemack, M.; Nolta, M.; Page, L.; Sehgal, N.; Sherwin, B.; Sievers, J.; Sifon, Andalaft C.J.; Spergel, D.; Staggs, S.; Switzer, E.; Wollack, E.
2013-01-01
Recent data from the WMAP, ACT and SPT experiments provide precise measurements of the cosmic microwave background temperature power spectrum over a wide range of angular scales. The combination of these observations is well fit by the standard, spatially flat {$Lambda$}CDM cosmological model,
Nonsingular electrovacuum solutions with dynamically generated cosmological constant
Energy Technology Data Exchange (ETDEWEB)
Guendelman, E.I., E-mail: guendel@bgumail.bgu.ac.il [Physics Department, Ben Gurion University of the Negev, Beer Sheva 84105 (Israel); Olmo, Gonzalo J., E-mail: gonzalo.olmo@csic.es [Departamento de Física Teórica and IFIC, Centro Mixto Universidad de Valencia – CSIC, Universidad de Valencia, Burjassot 46100, Valencia (Spain); Rubiera-Garcia, D., E-mail: drubiera@fisica.ufpb.br [Departamento de Física, Universidade Federal da Paraíba, 58051-900 João Pessoa, Paraíba (Brazil); Vasihoun, M., E-mail: maharyw@gmail.com [Physics Department, Ben Gurion University of the Negev, Beer Sheva 84105 (Israel)
2013-11-04
We consider static spherically symmetric configurations in a Palatini extension of General Relativity including R{sup 2} and Ricci-squared terms, which is known to replace the central singularity by a wormhole in the electrovacuum case. We modify the matter sector of the theory by adding to the usual Maxwell term a nonlinear electromagnetic extension which is known to implement a confinement mechanism in flat space. One feature of the resulting theory is that the nonlinear electric field leads to a dynamically generated cosmological constant. We show that with this matter source the solutions of the model are asymptotically de Sitter and possess a wormhole topology. We discuss in some detail the conditions that guarantee the absence of singularities and of traversable wormholes.
Cosmological-model-parameter determination from satellite-acquired type Ia and IIP Supernova Data
International Nuclear Information System (INIS)
Podariu, Silviu; Nugent, Peter; Ratra, Bharat
2000-01-01
We examine the constraints that satellite-acquired Type Ia and IIP supernova apparent magnitude versus redshift data will place on cosmological model parameters in models with and without a constant or time-variable cosmological constant lambda. High-quality data which could be acquired in the near future will result in tight constraints on these parameters. For example, if all other parameters of a spatially-flat model with a constant lambda are known, the supernova data should constrain the non-relativistic matter density parameter omega to better than 1 (2, 0.5) at 1 sigma with neutral (worst case, best case) assumptions about data quality
Generating three-parameter sensor
Directory of Open Access Journals (Sweden)
Filinyuk M. A.
2014-08-01
Full Text Available Generating sensors provide the possibility of getting remote information and its easy conversion into digital form. Typically, these are one-parameter sensors formed by combination of a primary transmitter (PT and a sine wave generator. Two-parameter sensors are not widely used as their implementation causes a problem with ambiguity output when measuring the PT. Nevertheless, the problem of creating miniature, thrifty multi-parameter RF sensors for different branches of science and industry remains relevant. Considering ways of designing RF sensors, we study the possibility of constructing a three-parameter microwave radio frequency range sensor, which is based on a two-stage three-parameter generalized immitance convertor (GIC. Resistive, inductive and capacitive PT are used as sensing elements. A mathematical model of the sensor, which describes the relation of the sensor parameters to the parameters of GIC and PT was developed. The basic parameters of the sensor, its transfer function and sensitivity were studied. It is shown that the maximum value of the power generated signal will be observed at a frequency of 175 MHz, and the frequency ranges depending on the parameters of the PT will be different. Research results and adequacy of the mathematical model were verified by the experiment. Error of the calculated dependences of the lasing frequency on PT parameters change, compared with the experimental data does not exceed 2 %. The relative sensitivity of the sensor based on two-stage GIC showed that for the resistive channel it is about 1.88, for the capacitive channel –1,54 and for the inductive channel –11,5. Thus, it becomes possible to increase the sensor sensitivity compared with the sensitivity of the PT almost 1,2—2 times, and by using the two stage GIC a multifunctional sensor is provided.
Type Ia Supernova Intrinsic Magnitude Dispersion and the Fitting of Cosmological Parameters
Kim, A. G.
2011-02-01
I present an analysis for fitting cosmological parameters from a Hubble diagram of a standard candle with unknown intrinsic magnitude dispersion. The dispersion is determined from the data, simultaneously with the cosmological parameters. This contrasts with the strategies used to date. The advantages of the presented analysis are that it is done in a single fit (it is not iterative), it provides a statistically founded and unbiased estimate of the intrinsic dispersion, and its cosmological-parameter uncertainties account for the intrinsic-dispersion uncertainty. Applied to Type Ia supernovae, my strategy provides a statistical measure to test for subtypes and assess the significance of any magnitude corrections applied to the calibrated candle. Parameter bias and differences between likelihood distributions produced by the presented and currently used fitters are negligibly small for existing and projected supernova data sets.
Fast Generation of Ensembles of Cosmological N-Body Simulations via Mode-Resampling
Energy Technology Data Exchange (ETDEWEB)
Schneider, M D; Cole, S; Frenk, C S; Szapudi, I
2011-02-14
We present an algorithm for quickly generating multiple realizations of N-body simulations to be used, for example, for cosmological parameter estimation from surveys of large-scale structure. Our algorithm uses a new method to resample the large-scale (Gaussian-distributed) Fourier modes in a periodic N-body simulation box in a manner that properly accounts for the nonlinear mode-coupling between large and small scales. We find that our method for adding new large-scale mode realizations recovers the nonlinear power spectrum to sub-percent accuracy on scales larger than about half the Nyquist frequency of the simulation box. Using 20 N-body simulations, we obtain a power spectrum covariance matrix estimate that matches the estimator from Takahashi et al. (from 5000 simulations) with < 20% errors in all matrix elements. Comparing the rates of convergence, we determine that our algorithm requires {approx}8 times fewer simulations to achieve a given error tolerance in estimates of the power spectrum covariance matrix. The degree of success of our algorithm indicates that we understand the main physical processes that give rise to the correlations in the matter power spectrum. Namely, the large-scale Fourier modes modulate both the degree of structure growth through the variation in the effective local matter density and also the spatial frequency of small-scale perturbations through large-scale displacements. We expect our algorithm to be useful for noise modeling when constraining cosmological parameters from weak lensing (cosmic shear) and galaxy surveys, rescaling summary statistics of N-body simulations for new cosmological parameter values, and any applications where the influence of Fourier modes larger than the simulation size must be accounted for.
Determination of cosmological parameters: An introduction for non ...
Indian Academy of Sciences (India)
Then I show how the age of the universe depends on them, followed by the evolution of the scale parameter of the universe for various values of the density parameters. Then I define strategies for measuring them, and show the results for the recent determination of these parameters from measurements on supernovas of ...
International Nuclear Information System (INIS)
Tegmark, Max; Zaldarriaga, Matias
2002-01-01
We present a method for measuring the cosmic matter budget without assumptions about speculative early Universe physics, and for measuring the primordial power spectrum P * (k) nonparametrically, either by combining CMB and LSS information or by using CMB polarization. Our method complements currently fashionable 'black box' cosmological parameter analysis, constraining cosmological models in a more physically intuitive fashion by mapping measurements of CMB, weak lensing and cluster abundance into k space, where they can be directly compared with each other and with galaxy and Lyα forest clustering. Including the new CBI results, we find that CMB measurements of P(k) overlap with those from 2dF galaxy clustering by over an order of magnitude in scale, and even overlap with weak lensing measurements. We describe how our approach can be used to raise the ambition level beyond cosmological parameter fitting as data improves, testing rather than assuming the underlying physics
Joint cosmic microwave background and weak lensing analysis: constraints on cosmological parameters.
Contaldi, Carlo R; Hoekstra, Henk; Lewis, Antony
2003-06-06
We use cosmic microwave background (CMB) observations together with the red-sequence cluster survey weak lensing results to derive constraints on a range of cosmological parameters. This particular choice of observations is motivated by their robust physical interpretation and complementarity. Our combined analysis, including a weak nucleosynthesis constraint, yields accurate determinations of a number of parameters including the amplitude of fluctuations sigma(8)=0.89+/-0.05 and matter density Omega(m)=0.30+/-0.03. We also find a value for the Hubble parameter of H(0)=70+/-3 km s(-1) Mpc(-1), in good agreement with the Hubble Space Telescope key-project result. We conclude that the combination of CMB and weak lensing data provides some of the most powerful constraints available in cosmology today.
Liguori, M
2008-01-01
We study the impact of cosmological parameters' uncertainties on estimates of the primordial NG parameter f_NL in local and equilateral models of non-Gaussianity. We show that propagating these errors increases the f_NL relative uncertainty by 16% for WMAP and 5 % for Planck in the local case, whereas for equilateral configurations the correction term are 14% and 4%, respectively. If we assume for local f_NL a central value of order 60, according to recent WMAP 5-years estimates, we obtain for Planck a final correction \\Delta f_NL = 3. Although not dramatic, this correction is at the level of the expected estimator uncertainty for Planck, and should then be taken into account when quoting the significance of an eventual future detection. In current estimates of f_NL the cosmological parameters are held fixed at their best-fit values. We finally note that the impact of uncertainties in the cosmological parameters on the final f_NL error bar would become totally negligible if the parameters were allowed to vary...
FORECASTING COSMOLOGICAL PARAMETER CONSTRAINTS FROM NEAR-FUTURE SPACE-BASED GALAXY SURVEYS
International Nuclear Information System (INIS)
Pavlov, Anatoly; Ratra, Bharat; Samushia, Lado
2012-01-01
The next generation of space-based galaxy surveys is expected to measure the growth rate of structure to a level of about one percent over a range of redshifts. The rate of growth of structure as a function of redshift depends on the behavior of dark energy and so can be used to constrain parameters of dark energy models. In this work, we investigate how well these future data will be able to constrain the time dependence of the dark energy density. We consider parameterizations of the dark energy equation of state, such as XCDM and ωCDM, as well as a consistent physical model of time-evolving scalar field dark energy, φCDM. We show that if the standard, specially flat cosmological model is taken as a fiducial model of the universe, these near-future measurements of structure growth will be able to constrain the time dependence of scalar field dark energy density to a precision of about 10%, which is almost an order of magnitude better than what can be achieved from a compilation of currently available data sets.
Evolution of the Brans—Dicke Parameter in Generalized Chameleon Cosmology
International Nuclear Information System (INIS)
Jamil, Mubasher; Momeni, D.
2011-01-01
Motivated by an earlier study of Sahoo and Singh [Mod. Phys. Lett. A 17 (2002) 2409], we investigate the time dependence of the Brans-Dicke parameter ω(t) for an expanding Universe in the generalized Brans-Dicke Chameleon cosmology, and obtain an explicit dependence of ω(t) in different expansion phases of the Universe. Also, we discuss how the observed accelerated expansion of the observable Universe can be accommodated in the present formalism. (geophysics, astronomy, and astrophysics)
Hannachi, Zitouni; Guessoum, Nidhal; Azzam, Walid
2016-07-01
Context: We use the correlation relations between the energy emitted by the GRBs in their prompt phases and the X-ray afterglow fluxes, in an effort to constrain cosmological parameters and construct a Hubble diagram at high redshifts, i.e. beyond those found in Type Ia supernovae. Methods: We use a sample of 128 Swift GRBs, which we have selected among more than 800 ones observed until July 2015. The selection is based on a few observational constraints: GRB flux higher than 0.4 photons/cm^2/s in the band 15-150 keV; spectrum fitted with simple power law; redshift accurately known and given; and X-ray afterglow observed and flux measured. The statistical method of maximum likelihood is then used to determine the best cosmological parameters (Ω_M, Ω_L) that give the best correlation between the isotropic gamma energies E_{iso} and the afterglow fluxes at the break time t_{b}. The χ^2 statistical test is also used as a way to compare results from two methods. Results & Conclusions: Although the number of GRBs with high redshifts is rather small, and despite the notable dispersion found in the data, the results we have obtained are quite encouraging and promising. The values of the cosmological parameters obtained here are close to those currently used.
Sunyaev-Zeldovich effect in WMAP and its effect on cosmological parameters
International Nuclear Information System (INIS)
Huffenberger, Kevin M.; Seljak, Uros; Makarov, Alexey
2004-01-01
We use multifrequency information in first year Wilkinson microwave anisotropy probe (WMAP) data to search for the Sunyaev-Zeldovich (SZ) effect. WMAP has sufficiently broad frequency coverage to constrain the SZ effect without the addition of higher frequency data: the SZ power spectrum amplitude is expected to increase 50% from W to Q frequency band. This, in combination with the low noise in WMAP, allows us to strongly constrain the SZ contribution. We derive an optimal frequency combination of WMAP cross-spectra to extract the SZ effect in the presence of noise, cosmic microwave background (CMB), and radio point sources, which are marginalized over. We find that the SZ contribution is less than 2% (95% C.L.) at the first acoustic peak in W band. Under the assumption that the removed radio point sources are not correlated with the SZ effect this limit implies σ 8 <1.07 at 95% C.L. We investigate the effect on the cosmological parameters of allowing an SZ component. We run Monte Carlo Markov chains with and without an SZ component and find that the addition of the SZ effect does not affect any of the cosmological conclusions. We conclude that the SZ effect does not contaminate the WMAP CMB or change cosmological parameters, refuting the recent claims that they may be corrupted
Integrated Sachs-Wolfe effect versus redshift test for the cosmological parameters
Kantowski, R.; Chen, B.; Dai, X.
2015-04-01
We describe a method using the integrated Sachs-Wolfe (ISW) effect caused by individual inhomogeneities to determine the cosmological parameters H0, Ωm , and ΩΛ, etc. This ISW-redshift test requires detailed knowledge of the internal kinematics of a set of individual density perturbations, e.g., galaxy clusters and/or cosmic voids, in particular their density and velocity profiles, and their mass accretion rates. It assumes the density perturbations are isolated and embedded (equivalently compensated) and makes use of the newly found relation between the ISW temperature perturbation of the cosmic microwave background (CMB) and the Fermat potential of the lens. Given measurements of the amplitudes of the temperature variations in the CMB caused by such clusters or voids at various redshifts and estimates of their angular sizes or masses, one can constrain the cosmological parameters. More realistically, the converse is more likely, i.e., if the background cosmology is sufficiently constrained, measurement of ISW profiles of clusters and voids (e.g., hot and cold spots and rings) can constrain dynamical properties of the dark matter, including accretion, associated with such lenses and thus constrain the evolution of these objects with redshift.
Effects of the interaction between dark energy and dark matter on cosmological parameters
International Nuclear Information System (INIS)
He, Jian-Hua; Wang, Bin
2008-01-01
We examine the effects of possible phenomenological interactions between dark energy and dark matter on cosmological parameters and their efficiency in solving the coincidence problem. We work with two simple parameterizations of the dynamical dark energy equation of state and the constant dark energy equation of state. Using observational data coming from the new 182 Gold type Ia supernova samples, the shift parameter of the Cosmic Microwave Background given by the three-year Wilkinson Microwave Anisotropy Probe observations and the baryon acoustic oscillation measurement from the Sloan Digital Sky Survey, we perform a statistical joint analysis of different forms of phenomenological interaction between dark energy and dark matter
Energy Technology Data Exchange (ETDEWEB)
Sobreira, F.; Rosenfeld, R. [Universidade Estadual Paulista Julio de Mesquita Filho (IFT/UNESP), Sao Paulo, SP (Brazil). Inst. Fisica Teorica; Simoni, F. de; Costa, L.A.N. da; Gaia, M.A.G.; Ramos, B.; Ogando, R.; Makler, M. [Laboratorio Interinstitucional de e-Astronomia (LIneA), Rio de Janeiro, RJ (Brazil)
2011-07-01
Full text: We study the cosmological constraints expected for the upcoming project Dark Energy Survey (DES) with the full functional form of the 2-point angular correlation function. The angular correlation function model applied in this work includes the effects of linear redshift-space distortion, photometric redshift errors (assumed to be Gaussian) and non-linearities prevenient from gravitational infall. The Fisher information matrix is constructed with the full covariance matrix, which takes the correlation between nearby redshift shells in a proper manner. The survey was sliced into 20 redshift shells in the range 0:4 {<=} z {<=} 1:40 with a variable angular scale in order to search only the scale around the signal from the baryon acoustic oscillation, therefore well within the validity of the non-linear model employed. We found that under those assumptions and with a flat {Lambda}CDM WMAP7 fiducial model, the DES will be able to constrain the dark energy equation of state parameter w with a precision of {approx} 20% and the cold dark matter with {approx} 11% when marginalizing over the other 25 parameters (bias is treated as a free parameter for each shell). When applying WMAP7 priors on {Omega}{sub baryon}, {Omega} c{sub dm}, n{sub s}, and HST priors on the Hubble parameter, w is constrained with {approx} 9% precision. This shows that the full shape of the angular correlation function with DES data will be a powerful probe to constrain cosmological parameters. (author)
Cosmological Parameter Estimation Using the Genus Amplitude—Application to Mock Galaxy Catalogs
Appleby, Stephen; Park, Changbom; Hong, Sungwook E.; Kim, Juhan
2018-01-01
We study the topology of the matter density field in two-dimensional slices and consider how we can use the amplitude A of the genus for cosmological parameter estimation. Using the latest Horizon Run 4 simulation data, we calculate the genus of the smoothed density field constructed from light cone mock galaxy catalogs. Information can be extracted from the amplitude of the genus by considering both its redshift evolution and magnitude. The constancy of the genus amplitude with redshift can be used as a standard population, from which we derive constraints on the equation of state of dark energy {w}{de}—by measuring A at z∼ 0.1 and z∼ 1, we can place an order {{Δ }}{w}{de}∼ { O }(15 % ) constraint on {w}{de}. By comparing A to its Gaussian expectation value, we can potentially derive an additional stringent constraint on the matter density {{Δ }}{{{Ω }}}{mat}∼ 0.01. We discuss the primary sources of contamination associated with the two measurements—redshift space distortion (RSD) and shot noise. With accurate knowledge of galaxy bias, we can successfully remove the effect of RSD, and the combined effect of shot noise and nonlinear gravitational evolution is suppressed by smoothing over suitably large scales {R}{{G}}≥slant 15 {Mpc}/h. Without knowledge of the bias, we discuss how joint measurements of the two- and three-dimensional genus can be used to constrain the growth factor β =f/b. The method can be applied optimally to redshift slices of a galaxy distribution generated using the drop-off technique.
Determination of the cosmological parameters and the nature of dark energy
International Nuclear Information System (INIS)
Linden, S.
2010-04-01
The measured properties of the dark energy component being consistent with a Cosmological Constant, Λ, this cosmological standard model is referred to as the Λ-Cold-Dark-Matter (ΛCDM) model. Despite its overall success, this model suffers from various problems. The existence of a Cosmological Constant raises fundamental questions. Attempts to describe it as the energy contribution from the vacuum as following from Quantum Field Theory failed quantitatively. In consequence, a large number of alternative models have been developed to describe the dark energy component: modified gravity, additional dimensions, Quintessence models. Also, astrophysical effects have been considered to mimic an accelerated expansion. The basics of the ΛCDM model and the various attempts of explaining dark energy are outlined in this thesis. Another major problem of the model comes from the dependencies of the fit results on a number of a priori assumptions and parameterization effects. Today, combined analyses of the various cosmological probes are performed to extract the parameters of the model. Due to a wrong model assumption or a bad parameterization of the real physics, one might end up measuring with high precision something which is not there. We show, that indeed due to the high precision of modern cosmological measurements, purely kinematic approaches to distance measurements no longer yield valid fit results except for accidental special cases, and that a fit of the exact (integral) redshift-distance relation is necessary. The main results of this work concern the use of the CPL parameterization of dark energy when coping with the dynamics of tracker solutions of Quintessence models, and the risk of introducing biases on the parameters due to the possibly prohibited extrapolation to arbitrary high redshifts of the SN type Ia magnitude calibration relation, which is obtained in the low-redshift regime. Whereas the risks of applying CPL shows up to be small for a wide range of
Jones, D. O.; Scolnic, D. M.; Riess, A. G.; Rest, A.; Kirshner, R. P.; Berger, E.; Kessler, R.; Pan, Y.-C.; Foley, R. J.; Chornock, R.; Ortega, C. A.; Challis, P. J.; Burgett, W. S.; Chambers, K. C.; Draper, P. W.; Flewelling, H.; Huber, M. E.; Kaiser, N.; Kudritzki, R.-P.; Metcalfe, N.; Tonry, J.; Wainscoat, R. J.; Waters, C.; Gall, E. E. E.; Kotak, R.; McCrum, M.; Smartt, S. J.; Smith, K. W.
2018-04-01
We use 1169 Pan-STARRS supernovae (SNe) and 195 low-z (z used to infer unbiased cosmological parameters by using a Bayesian methodology that marginalizes over core-collapse (CC) SN contamination. Our sample contains nearly twice as many SNe as the largest previous SN Ia compilation. Combining SNe with cosmic microwave background (CMB) constraints from Planck, we measure the dark energy equation-of-state parameter w to be ‑0.989 ± 0.057 (stat+sys). If w evolves with redshift as w(a) = w 0 + w a (1 ‑ a), we find w 0 = ‑0.912 ± 0.149 and w a = ‑0.513 ± 0.826. These results are consistent with cosmological parameters from the Joint Light-curve Analysis and the Pantheon sample. We try four different photometric classification priors for Pan-STARRS SNe and two alternate ways of modeling CC SN contamination, finding that no variant gives a w differing by more than 2% from the baseline measurement. The systematic uncertainty on w due to marginalizing over CC SN contamination, {σ }wCC}=0.012, is the third-smallest source of systematic uncertainty in this work. We find limited (1.6σ) evidence for evolution of the SN color-luminosity relation with redshift, a possible systematic that could constitute a significant uncertainty in future high-z analyses. Our data provide one of the best current constraints on w, demonstrating that samples with ∼5% CC SN contamination can give competitive cosmological constraints when the contaminating distribution is marginalized over in a Bayesian framework.
The Atacama Cosmology Telescope: Two-Season ACTPol Spectra and Parameters
Louis, Thibaut; Grace, Emily; Hasselfield, Matthew; Lungu, Marius; Maurin, Loic; Addison, Graeme E.; Adem Peter A. R.; Aiola, Simone; Allison, Rupert; Amiri, Mandana;
2017-01-01
We present the temperature and polarization angular power spectra measuredby the Atacama Cosmology Telescope Polarimeter (ACTPol). We analyze night-time datacollected during 2013-14 using two detector arrays at 149 GHz, from 548 deg(exp. 2) of sky onthe celestial equator. We use these spectra, and the spectra measured with the MBAC camera on ACT from 2008-10, in combination with Planck and WMAP data to estimate cosmological parameters from the temperature, polarization, and temperature-polarization cross-correlations. We find the new ACTPol data to be consistent with the CDM model. The ACTPol temperature-polarization cross-spectrum now provides stronger constraints on multiple parameters than the ACTPol temperature spectrum, including the baryon density, the acoustic peak angular scale, and the derived Hubble constant. The new ACTPol dataprovide information on damping tail parameters. The joint uncertainty on the number of neutrino species and the primordial helium fraction is reduced by 20% when adding ACTPol to Planck temperature data alone.
The Atacama Cosmology Telescope: two-season ACTPol spectra and parameters
Energy Technology Data Exchange (ETDEWEB)
Louis, Thibaut [UPMC Univ Paris 06, UMR7095, Institut d' Astrophysique de Paris, F-75014, Paris (France); Grace, Emily; Aiola, Simone; Choi, Steve K. [Joseph Henry Laboratories of Physics, Jadwin Hall, Princeton University, Princeton, NJ 08544 (United States); Hasselfield, Matthew [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Lungu, Marius; Angile, Elio [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Maurin, Loïc [Instituto de Astrofísica and Centro de Astro-Ingeniería, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago (Chile); Addison, Graeme E. [Department of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218-2686 (United States); Ade, Peter A. R. [School of Physics and Astronomy, Cardiff University, The Parade, Cardiff, Wales, CF24 3AA (United Kingdom); Allison, Rupert; Calabrese, Erminia [Sub-Department of Astrophysics, University of Oxford, Keble Road, Oxford, OX1 3RH (United Kingdom); Amiri, Mandana [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z4 (Canada); Battaglia, Nicholas [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States); Beall, James A.; Britton, Joe; Cho, Hsiao-mei [NIST Quantum Devices Group, 325 Broadway Mailcode 817.03, Boulder, CO 80305 (United States); De Bernardis, Francesco [Department of Physics, Cornell University, Ithaca, NY 14853 (United States); Bond, J Richard, E-mail: louis@iap.fr [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON, M5S 3H8 (Canada); and others
2017-06-01
We present the temperature and polarization angular power spectra measured by the Atacama Cosmology Telescope Polarimeter (ACTPol). We analyze night-time data collected during 2013–14 using two detector arrays at 149 GHz, from 548 deg{sup 2} of sky on the celestial equator. We use these spectra, and the spectra measured with the MBAC camera on ACT from 2008–10, in combination with planck and wmap data to estimate cosmological parameters from the temperature, polarization, and temperature-polarization cross-correlations. We find the new ACTPol data to be consistent with the ΛCDM model. The ACTPol temperature-polarization cross-spectrum now provides stronger constraints on multiple parameters than the ACTPol temperature spectrum, including the baryon density, the acoustic peak angular scale, and the derived Hubble constant. The new ACTPol data provide information on damping tail parameters. The joint uncertainty on the number of neutrino species and the primordial helium fraction is reduced by 20% when adding ACTPol to Planck temperature data alone.
KiDS-450: the tomographic weak lensing power spectrum and constraints on cosmological parameters
Köhlinger, F.; Viola, M.; Joachimi, B.; Hoekstra, H.; van Uitert, E.; Hildebrandt, H.; Choi, A.; Erben, T.; Heymans, C.; Joudaki, S.; Klaes, D.; Kuijken, K.; Merten, J.; Miller, L.; Schneider, P.; Valentijn, E. A.
2017-11-01
We present measurements of the weak gravitational lensing shear power spectrum based on 450 ° ^2 of imaging data from the Kilo Degree Survey. We employ a quadratic estimator in two and three redshift bins and extract band powers of redshift autocorrelation and cross-correlation spectra in the multipole range 76 ≤ ℓ ≤ 1310. The cosmological interpretation of the measured shear power spectra is performed in a Bayesian framework assuming a ΛCDM model with spatially flat geometry, while accounting for small residual uncertainties in the shear calibration and redshift distributions as well as marginalizing over intrinsic alignments, baryon feedback and an excess-noise power model. Moreover, massive neutrinos are included in the modelling. The cosmological main result is expressed in terms of the parameter combination S_8 ≡ σ _8 √{Ω_m/0.3} yielding S8 = 0.651 ± 0.058 (three z-bins), confirming the recently reported tension in this parameter with constraints from Planck at 3.2σ (three z-bins). We cross-check the results of the three z-bin analysis with the weaker constraints from the two z-bin analysis and find them to be consistent. The high-level data products of this analysis, such as the band power measurements, covariance matrices, redshift distributions and likelihood evaluation chains are available at http://kids.strw.leidenuniv.nl.
Perturbations in loop quantum cosmology
International Nuclear Information System (INIS)
Nelson, W; Agullo, I; Ashtekar, A
2014-01-01
The era of precision cosmology has allowed us to accurately determine many important cosmological parameters, in particular via the CMB. Confronting Loop Quantum Cosmology with these observations provides us with a powerful test of the theory. For this to be possible, we need a detailed understanding of the generation and evolution of inhomogeneous perturbations during the early, quantum gravity phase of the universe. Here, we have described how Loop Quantum Cosmology provides a completion of the inflationary paradigm, that is consistent with the observed power spectra of the CMB
NINE-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE (WMAP) OBSERVATIONS: COSMOLOGICAL PARAMETER RESULTS
International Nuclear Information System (INIS)
Hinshaw, G.; Halpern, M.; Larson, D.; Bennett, C. L.; Weiland, J. L.; Komatsu, E.; Spergel, D. N.; Dunkley, J.; Nolta, M. R.; Hill, R. S.; Odegard, N.; Page, L.; Jarosik, N.; Smith, K. M.; Gold, B.; Kogut, A.; Wollack, E.; Limon, M.; Meyer, S. S.; Tucker, G. S.
2013-01-01
We present cosmological parameter constraints based on the final nine-year Wilkinson Microwave Anisotropy Probe (WMAP) data, in conjunction with a number of additional cosmological data sets. The WMAP data alone, and in combination, continue to be remarkably well fit by a six-parameter ΛCDM model. When WMAP data are combined with measurements of the high-l cosmic microwave background anisotropy, the baryon acoustic oscillation scale, and the Hubble constant, the matter and energy densities, Ω b h 2 , Ω c h 2 , and Ω Λ , are each determined to a precision of ∼1.5%. The amplitude of the primordial spectrum is measured to within 3%, and there is now evidence for a tilt in the primordial spectrum at the 5σ level, confirming the first detection of tilt based on the five-year WMAP data. At the end of the WMAP mission, the nine-year data decrease the allowable volume of the six-dimensional ΛCDM parameter space by a factor of 68,000 relative to pre-WMAP measurements. We investigate a number of data combinations and show that their ΛCDM parameter fits are consistent. New limits on deviations from the six-parameter model are presented, for example: the fractional contribution of tensor modes is limited to r k = -0.0027 +0.0039 -0.0038 ; the summed mass of neutrinos is limited to Σm ν eff = 3.84 ± 0.40, when the full data are analyzed. The joint constraint on N eff and the primordial helium abundance, Y He , agrees with the prediction of standard big bang nucleosynthesis. We compare recent Planck measurements of the Sunyaev-Zel'dovich effect with our seven-year measurements, and show their mutual agreement. Our analysis of the polarization pattern around temperature extrema is updated. This confirms a fundamental prediction of the standard cosmological model and provides a striking illustration of acoustic oscillations and adiabatic initial conditions in the early universe
Directory of Open Access Journals (Sweden)
Gregory Beskin
2014-08-01
Full Text Available The results of a study of 43 peaked R-band light curves of optical counterparts of gamma-ray bursts with known redshifts are presented. The parameters of optical transients were calculated in the comoving frame, and then a search for pair correlations between them was conducted. A statistical analysis showed a strong correlation between the peak luminosity and the redshift both for pure afterglows and for events with residual gamma activity, which cannot be explained as an effect of observational selection.This suggests a cosmological evolution of the parameters of the local interstellar medium around the sources of the gamma-ray burst. In the models of forward and reverse shock waves, a relation between the density of the interstellar medium and the redshift was built for gamma-ray burst afterglows, leading to a power-law dependence of the star-formation rate at regions around GRBs on redshift with a slope of about 6.
Directory of Open Access Journals (Sweden)
Pierluigi Monaco
2016-10-01
Full Text Available Precision cosmology has recently triggered new attention on the topic of approximate methods for the clustering of matter on large scales, whose foundations date back to the period from the late 1960s to early 1990s. Indeed, although the prospect of reaching sub-percent accuracy in the measurement of clustering poses a challenge even to full N-body simulations, an accurate estimation of the covariance matrix of clustering statistics, not to mention the sampling of parameter space, requires usage of a large number (hundreds in the most favourable cases of simulated (mock galaxy catalogs. Combination of few N-body simulations with a large number of realizations performed with approximate methods gives the most promising approach to solve these problems with a reasonable amount of resources. In this paper I review this topic, starting from the foundations of the methods, then going through the pioneering efforts of the 1990s, and finally presenting the latest extensions and a few codes that are now being used in present-generation surveys and thoroughly tested to assess their performance in the context of future surveys.
Program for parameter studies of steam generators
International Nuclear Information System (INIS)
Mathisen, R.P.
1982-11-01
R2-GEN is a computer code for stationary thermal parameter studies of steam generators. The geometry and data are valid for Ringhals-2 generators. Subroutines and relevant calculations are included. The program is based on a heterogeneous flow model and some applications on tubes with varying contamination are presented. (G.B.)
Energy Technology Data Exchange (ETDEWEB)
Villani, Mattia, E-mail: villani@fi.infn.it [Sezione INFN di Firenze, Polo Scientifico Via Sansone 1, 50019, Sesto Fiorentino (Italy)
2014-06-01
We consider the Goode-Wainwright representation of the Szekeres cosmological models and calculate the Taylor expansion of the luminosity distance in order to study the effects of the inhomogeneities on cosmographic parameters. Without making a particular choice for the arbitrary functions defining the metric, we Taylor expand up to the second order in redshift for Family I and up to the third order for Family II Szekeres metrics under the hypotesis, based on observation, that local structure formation is over. In a conservative fashion, we also allow for the existence of a non null cosmological constant.
Cosmological parameter uncertainties from SALT-II type Ia supernova light curve models
International Nuclear Information System (INIS)
Mosher, J.; Sako, M.; Guy, J.; Astier, P.; Betoule, M.; El-Hage, P.; Pain, R.; Regnault, N.; Kessler, R.; Frieman, J. A.; Marriner, J.; Biswas, R.; Kuhlmann, S.; Schneider, D. P.
2014-01-01
We use simulated type Ia supernova (SN Ia) samples, including both photometry and spectra, to perform the first direct validation of cosmology analysis using the SALT-II light curve model. This validation includes residuals from the light curve training process, systematic biases in SN Ia distance measurements, and a bias on the dark energy equation of state parameter w. Using the SN-analysis package SNANA, we simulate and analyze realistic samples corresponding to the data samples used in the SNLS3 analysis: ∼120 low-redshift (z < 0.1) SNe Ia, ∼255 Sloan Digital Sky Survey SNe Ia (z < 0.4), and ∼290 SNLS SNe Ia (z ≤ 1). To probe systematic uncertainties in detail, we vary the input spectral model, the model of intrinsic scatter, and the smoothing (i.e., regularization) parameters used during the SALT-II model training. Using realistic intrinsic scatter models results in a slight bias in the ultraviolet portion of the trained SALT-II model, and w biases (w input – w recovered ) ranging from –0.005 ± 0.012 to –0.024 ± 0.010. These biases are indistinguishable from each other within the uncertainty; the average bias on w is –0.014 ± 0.007.
Cosmological Parameter Uncertainties from SALT-II Type Ia Supernova Light Curve Models
Energy Technology Data Exchange (ETDEWEB)
Mosher, J. [Pennsylvania U.; Guy, J. [LBL, Berkeley; Kessler, R. [Chicago U., KICP; Astier, P. [Paris U., VI-VII; Marriner, J. [Fermilab; Betoule, M. [Paris U., VI-VII; Sako, M. [Pennsylvania U.; El-Hage, P. [Paris U., VI-VII; Biswas, R. [Argonne; Pain, R. [Paris U., VI-VII; Kuhlmann, S. [Argonne; Regnault, N. [Paris U., VI-VII; Frieman, J. A. [Fermilab; Schneider, D. P. [Penn State U.
2014-08-29
We use simulated type Ia supernova (SN Ia) samples, including both photometry and spectra, to perform the first direct validation of cosmology analysis using the SALT-II light curve model. This validation includes residuals from the light curve training process, systematic biases in SN Ia distance measurements, and a bias on the dark energy equation of state parameter w. Using the SN-analysis package SNANA, we simulate and analyze realistic samples corresponding to the data samples used in the SNLS3 analysis: ~120 low-redshift (z < 0.1) SNe Ia, ~255 Sloan Digital Sky Survey SNe Ia (z < 0.4), and ~290 SNLS SNe Ia (z ≤ 1). To probe systematic uncertainties in detail, we vary the input spectral model, the model of intrinsic scatter, and the smoothing (i.e., regularization) parameters used during the SALT-II model training. Using realistic intrinsic scatter models results in a slight bias in the ultraviolet portion of the trained SALT-II model, and w biases (w (input) – w (recovered)) ranging from –0.005 ± 0.012 to –0.024 ± 0.010. These biases are indistinguishable from each other within the uncertainty, the average bias on w is –0.014 ± 0.007.
Properties of the stars of early generations in the scale covariant cosmology
International Nuclear Information System (INIS)
Maeder, A.
1978-01-01
We examine here some consequences of cosmological propositions which accept that further invariances exist in the theory of gravitation. Several astrophysical tests have already been performed, with the noticeable and worrying results that astrophysics only supports scale invariance if matter creation still occurs in the Universe. Within this cosmological framework, stars being very different from the present ones would have existed in the past with higher rate of nuclear transformation and higher luminosity per unit of mass. The basic properties of these stars at an early epoch (t = 1/5 t 0 ) are examined with numerical models: the zero-age sequence, the central conditions in stars, the various critical stellar masses, the mass- and gravity-luminosity relation, the paths in the HR diagram, the changes of lifetimes, the evolution in the log Tsub(c) vs log rhosub(c) diagram. Useful expressions are also given for deriving by scaling the above properties at epochs other than the one considered in numerical applications. A major change occurs for the problem of the helium synthesis. In the scale covariant cosmology, the big-bang He-synthesis seems to be only of very marginal importance and the essential of the present He-content of the Universe could be accounted by stellar processes at the early generations of stars. This has for consequence that the ratio ΔY/ΔZ of Helium to the metals synthetized during the history of the Galaxy would be much larger than as predicted by standard cosmology. (orig.) [de
On estimating cosmology-dependent covariance matrices
International Nuclear Information System (INIS)
Morrison, Christopher B.; Schneider, Michael D.
2013-01-01
We describe a statistical model to estimate the covariance matrix of matter tracer two-point correlation functions with cosmological simulations. Assuming a fixed number of cosmological simulation runs, we describe how to build a 'statistical emulator' of the two-point function covariance over a specified range of input cosmological parameters. Because the simulation runs with different cosmological models help to constrain the form of the covariance, we predict that the cosmology-dependent covariance may be estimated with a comparable number of simulations as would be needed to estimate the covariance for fixed cosmology. Our framework is a necessary first step in planning a simulations campaign for analyzing the next generation of cosmological surveys
International Nuclear Information System (INIS)
Hamann, Jan; Hannestad, Steen; Melchiorri, Alessandro; Wong, Yvonne Y Y
2008-01-01
We explore and compare the performances of two non-linear correction and scale-dependent biasing models for the extraction of cosmological information from galaxy power spectrum data, especially in the context of beyond-ΛCDM (CDM: cold dark matter) cosmologies. The first model is the well known Q model, first applied in the analysis of Two-degree Field Galaxy Redshift Survey data. The second, the P model, is inspired by the halo model, in which non-linear evolution and scale-dependent biasing are encapsulated in a single non-Poisson shot noise term. We find that while the two models perform equally well in providing adequate correction for a range of galaxy clustering data in standard ΛCDM cosmology and in extensions with massive neutrinos, the Q model can give unphysical results in cosmologies containing a subdominant free-streaming dark matter whose temperature depends on the particle mass, e.g., relic thermal axions, unless a suitable prior is imposed on the correction parameter. This last case also exposes the danger of analytic marginalization, a technique sometimes used in the marginalization of nuisance parameters. In contrast, the P model suffers no undesirable effects, and is the recommended non-linear correction model also because of its physical transparency
Hamann, Jan; Hannestad, Steen; Melchiorri, Alessandro; Wong, Yvonne Y. Y.
2008-07-01
We explore and compare the performances of two non-linear correction and scale-dependent biasing models for the extraction of cosmological information from galaxy power spectrum data, especially in the context of beyond-ΛCDM (CDM: cold dark matter) cosmologies. The first model is the well known Q model, first applied in the analysis of Two-degree Field Galaxy Redshift Survey data. The second, the P model, is inspired by the halo model, in which non-linear evolution and scale-dependent biasing are encapsulated in a single non-Poisson shot noise term. We find that while the two models perform equally well in providing adequate correction for a range of galaxy clustering data in standard ΛCDM cosmology and in extensions with massive neutrinos, the Q model can give unphysical results in cosmologies containing a subdominant free-streaming dark matter whose temperature depends on the particle mass, e.g., relic thermal axions, unless a suitable prior is imposed on the correction parameter. This last case also exposes the danger of analytic marginalization, a technique sometimes used in the marginalization of nuisance parameters. In contrast, the P model suffers no undesirable effects, and is the recommended non-linear correction model also because of its physical transparency.
Thompson, Rodger I.
2018-04-01
This investigation explores using the beta function formalism to calculate analytic solutions for the observable parameters in rolling scalar field cosmologies. The beta function in this case is the derivative of the scalar ϕ with respect to the natural log of the scale factor a, β (φ )=d φ /d ln (a). Once the beta function is specified, modulo a boundary condition, the evolution of the scalar ϕ as a function of the scale factor is completely determined. A rolling scalar field cosmology is defined by its action which can contain a range of physically motivated dark energy potentials. The beta function is chosen so that the associated "beta potential" is an accurate, but not exact, representation of the appropriate dark energy model potential. The basic concept is that the action with the beta potential is so similar to the action with the model potential that solutions using the beta action are accurate representations of solutions using the model action. The beta function provides an extra equation to calculate analytic functions of the cosmologies parameters as a function of the scale factor that are that are not calculable using only the model action. As an example this investigation uses a quintessence cosmology to demonstrate the method for power and inverse power law dark energy potentials. An interesting result of the investigation is that the Hubble parameter H is almost completely insensitive to the power of the potentials and that ΛCDM is part of the family of quintessence cosmology power law potentials with a power of zero.
Directory of Open Access Journals (Sweden)
Lorenzo Iorio
2018-03-01
Full Text Available Independent tests aiming to constrain the value of the cosmological constant Λ are usually difficult because of its extreme smallness ( Λ ≃ 1 × 10 - 52 m - 2 , or 2 . 89 × 10 - 122 in Planck units . Bounds on it from Solar System orbital motions determined with spacecraft tracking are currently at the ≃ 10 - 43 – 10 - 44 m - 2 ( 5 – 1 × 10 - 113 in Planck units level, but they may turn out to be optimistic since Λ has not yet been explicitly modeled in the planetary data reductions. Accurate ( σ τ p ≃ 1 – 10 μ s timing of expected pulsars orbiting the Black Hole at the Galactic Center, preferably along highly eccentric and wide orbits, might, at least in principle, improve the planetary constraints by several orders of magnitude. By looking at the average time shift per orbit Δ δ τ ¯ p Λ , an S2-like orbital configuration with e = 0 . 8839 , P b = 16 yr would permit a preliminarily upper bound of the order of Λ ≲ 9 × 10 - 47 m - 2 ≲ 2 × 10 - 116 in Planck units if only σ τ p were to be considered. Our results can be easily extended to modified models of gravity using Λ -type parameters.
Energy Technology Data Exchange (ETDEWEB)
Jennings, E.; Madigan, M.
2017-04-01
Given the complexity of modern cosmological parameter inference where we arefaced with non-Gaussian data and noise, correlated systematics and multi-probecorrelated data sets, the Approximate Bayesian Computation (ABC) method is apromising alternative to traditional Markov Chain Monte Carlo approaches in thecase where the Likelihood is intractable or unknown. The ABC method is called"Likelihood free" as it avoids explicit evaluation of the Likelihood by using aforward model simulation of the data which can include systematics. Weintroduce astroABC, an open source ABC Sequential Monte Carlo (SMC) sampler forparameter estimation. A key challenge in astrophysics is the efficient use oflarge multi-probe datasets to constrain high dimensional, possibly correlatedparameter spaces. With this in mind astroABC allows for massive parallelizationusing MPI, a framework that handles spawning of jobs across multiple nodes. Akey new feature of astroABC is the ability to create MPI groups with differentcommunicators, one for the sampler and several others for the forward modelsimulation, which speeds up sampling time considerably. For smaller jobs thePython multiprocessing option is also available. Other key features include: aSequential Monte Carlo sampler, a method for iteratively adapting tolerancelevels, local covariance estimate using scikit-learn's KDTree, modules forspecifying optimal covariance matrix for a component-wise or multivariatenormal perturbation kernel, output and restart files are backed up everyiteration, user defined metric and simulation methods, a module for specifyingheterogeneous parameter priors including non-standard prior PDFs, a module forspecifying a constant, linear, log or exponential tolerance level,well-documented examples and sample scripts. This code is hosted online athttps://github.com/EliseJ/astroABC
Mass generation, the cosmological constant problem, conformal symmetry, and the Higgs boson
Mannheim, Philip D.
2017-05-01
In 2013 the Nobel Prize in Physics was awarded to Francois Englert and Peter Higgs for their work in 1964 along with the late Robert Brout on the mass generation mechanism (the Higgs mechanism) in local gauge theories. This mechanism requires the existence of a massive scalar particle, the Higgs boson, and in 2012 the Higgs boson was finally discovered at the Large Hadron Collider after being sought for almost half a century. In this article we review the work that led to the discovery of the Higgs boson and discuss its implications. We approach the topic from the perspective of a dynamically generated Higgs boson that is a fermion-antifermion bound state rather than an elementary field that appears in an input Lagrangian. In particular, we emphasize the connection with the Bardeen-Cooper-Schrieffer theory of superconductivity. We identify the double-well Higgs potential not as a fundamental potential but as a mean-field effective Lagrangian with a dynamical Higgs boson being generated through a residual interaction that accompanies the mean-field Lagrangian. We discuss what we believe to be the key challenge raised by the discovery of the Higgs boson, namely determining whether it is elementary or composite, and through study of a conformal invariant field theory model as realized with critical scaling and anomalous dimensions, suggest that the width of the Higgs boson might serve as a suitable diagnostic for discriminating between an elementary Higgs boson and a composite one. We discuss the implications of Higgs boson mass generation for the cosmological constant problem, as the cosmological constant receives contributions from the very mechanism that generates the Higgs boson mass in the first place. We show that the contribution to the cosmological constant due to a composite Higgs boson is more tractable and under control than the contribution due to an elementary Higgs boson, and is potentially completely under control if there is an underlying conformal
On the impact of large angle CMB polarization data on cosmological parameters
Energy Technology Data Exchange (ETDEWEB)
Lattanzi, Massimiliano; Mandolesi, Nazzareno; Natoli, Paolo [Dipartimento di Fisica e Scienze della Terra, Università di Ferrara, Via Giuseppe Saragat 1, I-44122 Ferrara (Italy); Burigana, Carlo; Gruppuso, Alessandro; Trombetti, Tiziana [Istituto Nazionale di Astrofisica, Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, Via Piero Gobetti 101, I-40129 Bologna (Italy); Gerbino, Martina [The Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm (Sweden); Polenta, Gianluca [Agenzia Spaziale Italiana Science Data Center, Via del Politecnico snc, 00133, Roma (Italy); Salvati, Laura, E-mail: lattanzi@fe.infn.it, E-mail: burigana@iasfbo.inaf.it, E-mail: martina.gerbino@fysik.su.se, E-mail: gruppuso@iasfbo.inaf.it, E-mail: nazzareno.mandolesi@unife.it, E-mail: paolo.natoli@unife.it, E-mail: gianluca.polenta@asdc.asi.it, E-mail: laura.salvati@ias.u-psud.fr, E-mail: trombetti@iasfbo.inaf.it [Dipartimento di Fisica, Università La Sapienza, Piazzale Aldo Moro 2, I-00185 Roma (Italy)
2017-02-01
We study the impact of the large-angle CMB polarization datasets publicly released by the WMAP and Planck satellites on the estimation of cosmological parameters of the ΛCDM model. To complement large-angle polarization, we consider the high resolution (or 'high-ℓ') CMB datasets from either WMAP or Planck as well as CMB lensing as traced by Planck 's measured four point correlation function. In the case of WMAP, we compute the large-angle polarization likelihood starting over from low resolution frequency maps and their covariance matrices, and perform our own foreground mitigation technique, which includes as a possible alternative Planck 353 GHz data to trace polarized dust. We find that the latter choice induces a downward shift in the optical depth τ, roughly of order 2σ, robust to the choice of the complementary high resolution dataset. When the Planck 353 GHz is consistently used to minimize polarized dust emission, WMAP and Planck 70 GHz large-angle polarization data are in remarkable agreement: by combining them we find τ = 0.066 {sup +0.012}{sub −0.013}, again very stable against the particular choice for high-ℓ data. We find that the amplitude of primordial fluctuations A {sub s} , notoriously degenerate with τ, is the parameter second most affected by the assumptions on polarized dust removal, but the other parameters are also affected, typically between 0.5 and 1σ. In particular, cleaning dust with Planck 's 353 GHz data imposes a 1σ downward shift in the value of the Hubble constant H {sub 0}, significantly contributing to the tension reported between CMB based and direct measurements of the present expansion rate. On the other hand, we find that the appearance of the so-called low ℓ anomaly, a well-known tension between the high- and low-resolution CMB anisotropy amplitude, is not significantly affected by the details of large-angle polarization, or by the particular high-ℓ dataset employed.
Mandelbaum, Rachel; Slosar, Anže; Baldauf, Tobias; Seljak, Uroš; Hirata, Christopher M.; Nakajima, Reiko; Reyes, Reinabelle; Smith, Robert E.
2013-06-01
Recent studies have shown that the cross-correlation coefficient between galaxies and dark matter is very close to unity on scales outside a few virial radii of galaxy haloes, independent of the details of how galaxies populate dark matter haloes. This finding makes it possible to determine the dark matter clustering from measurements of galaxy-galaxy weak lensing and galaxy clustering. We present new cosmological parameter constraints based on large-scale measurements of spectroscopic galaxy samples from the Sloan Digital Sky Survey (SDSS) data release 7. We generalize the approach of Baldauf et al. to remove small-scale information (below 2 and 4 h-1 Mpc for lensing and clustering measurements, respectively), where the cross-correlation coefficient differs from unity. We derive constraints for three galaxy samples covering 7131 deg2, containing 69 150, 62 150 and 35 088 galaxies with mean redshifts of 0.11, 0.28 and 0.40. We clearly detect scale-dependent galaxy bias for the more luminous galaxy samples, at a level consistent with theoretical expectations. When we vary both σ8 and Ωm (and marginalize over non-linear galaxy bias) in a flat Λ cold dark matter model, the best-constrained quantity is σ8(Ωm/0.25)0.57 = 0.80 ± 0.05 (1σ, stat. + sys.), where statistical and systematic errors (photometric redshift and shear calibration) have comparable contributions, and we have fixed ns = 0.96 and h = 0.7. These strong constraints on the matter clustering suggest that this method is competitive with cosmic shear in current data, while having very complementary and in some ways less serious systematics. We therefore expect that this method will play a prominent role in future weak lensing surveys. When we combine these data with Wilkinson Microwave Anisotropy Probe 7-year (WMAP7) cosmic microwave background (CMB) data, constraints on σ8, Ωm, H0, wde and ∑mν become 30-80 per cent tighter than with CMB data alone, since our data break several parameter
International Nuclear Information System (INIS)
Yao, Ji; Ishak, Mustapha; Lin, Weikang; Troxel, Michael
2017-01-01
Intrinsic alignments (IA) of galaxies have been recognized as one of the most serious contaminants to weak lensing. These systematics need to be isolated and mitigated in order for ongoing and future lensing surveys to reach their full potential. The IA self-calibration (SC) method was shown in previous studies to be able to reduce the GI contamination by up to a factor of 10 for the 2-point and 3-point correlations. The SC method does not require the assumption of an IA model in its working and can extract the GI signal from the same photo-z survey offering the possibility to test and understand structure formation scenarios and their relationship to IA models. In this paper, we study the effects of the IA SC mitigation method on the precision and accuracy of cosmological parameter constraints from future cosmic shear surveys LSST, WFIRST and Euclid. We perform analytical and numerical calculations to estimate the loss of precision and the residual bias in the best fit cosmological parameters after the self-calibration is performed. We take into account uncertainties from photometric redshifts and the galaxy bias. We find that the confidence contours are slightly inflated from applying the SC method itself while a significant increase is due to the inclusion of the photo-z uncertainties. The bias of cosmological parameters is reduced from several-σ, when IA is not corrected for, to below 1-σ after SC is applied. These numbers are comparable to those resulting from applying the method of marginalizing over IA model parameters despite the fact that the two methods operate very differently. We conclude that implementing the SC for these future cosmic-shear surveys will not only allow one to efficiently mitigate the GI contaminant but also help to understand their modeling and link to structure formation.
Energy Technology Data Exchange (ETDEWEB)
Yao, Ji; Ishak, Mustapha; Lin, Weikang [Department of Physics, The University of Texas at Dallas, Dallas, TX 75080 (United States); Troxel, Michael, E-mail: jxy131230@utdallas.edu, E-mail: mxi054000@utdallas.edu, E-mail: wxl123830@utdallas.edu, E-mail: michael.a.troxel@gmail.com [Department of Physics, Ohio State University, Columbus, OH 43210 (United States)
2017-10-01
Intrinsic alignments (IA) of galaxies have been recognized as one of the most serious contaminants to weak lensing. These systematics need to be isolated and mitigated in order for ongoing and future lensing surveys to reach their full potential. The IA self-calibration (SC) method was shown in previous studies to be able to reduce the GI contamination by up to a factor of 10 for the 2-point and 3-point correlations. The SC method does not require the assumption of an IA model in its working and can extract the GI signal from the same photo-z survey offering the possibility to test and understand structure formation scenarios and their relationship to IA models. In this paper, we study the effects of the IA SC mitigation method on the precision and accuracy of cosmological parameter constraints from future cosmic shear surveys LSST, WFIRST and Euclid. We perform analytical and numerical calculations to estimate the loss of precision and the residual bias in the best fit cosmological parameters after the self-calibration is performed. We take into account uncertainties from photometric redshifts and the galaxy bias. We find that the confidence contours are slightly inflated from applying the SC method itself while a significant increase is due to the inclusion of the photo-z uncertainties. The bias of cosmological parameters is reduced from several-σ, when IA is not corrected for, to below 1-σ after SC is applied. These numbers are comparable to those resulting from applying the method of marginalizing over IA model parameters despite the fact that the two methods operate very differently. We conclude that implementing the SC for these future cosmic-shear surveys will not only allow one to efficiently mitigate the GI contaminant but also help to understand their modeling and link to structure formation.
Rocha, G.; Pagano, L.; Górski, K. M.; Huffenberger, K. M.; Lawrence, C. R.; Lange, A. E.
2010-04-01
We introduce a new method to propagate uncertainties in the beam shapes used to measure the cosmic microwave background to cosmological parameters determined from those measurements. The method, called markov chain beam randomization (MCBR), randomly samples from a set of templates or functions that describe the beam uncertainties. The method is much faster than direct numerical integration over systematic “nuisance” parameters, and is not restricted to simple, idealized cases as is analytic marginalization. It does not assume the data are normally distributed, and does not require Gaussian priors on the specific systematic uncertainties. We show that MCBR properly accounts for and provides the marginalized errors of the parameters. The method can be generalized and used to propagate any systematic uncertainties for which a set of templates is available. We apply the method to the Planck satellite, and consider future experiments. Beam measurement errors should have a small effect on cosmological parameters as long as the beam fitting is performed after removal of 1/f noise.
Scalar-tensor cosmology with cosmological constant
International Nuclear Information System (INIS)
Maslanka, K.
1983-01-01
The equations of scalar-tensor theory of gravitation with cosmological constant in the case of homogeneous and isotropic cosmological model can be reduced to dynamical system of three differential equations with unknown functions H=R/R, THETA=phi/phi, S=e/phi. When new variables are introduced the system becomes more symmetrical and cosmological solutions R(t), phi(t), e(t) are found. It is shown that when cosmological constant is introduced large class of solutions which depend also on Dicke-Brans parameter can be obtained. Investigations of these solutions give general limits for cosmological constant and mean density of matter in plane model. (author)
Enqvist, K
2012-01-01
The very basics of cosmological inflation are discussed. We derive the equations of motion for the inflaton field, introduce the slow-roll parameters, and present the computation of the inflationary perturbations and their connection to the temperature fluctuations of the cosmic microwave background.
The influence of super-horizon scales on cosmological observables generated during inflation
Matarrese, Sabino; Musso, Marcello A.; Riotto, Antonio
2004-05-01
Using the techniques of out-of-equilibrium field theory, we study the influence on properties of cosmological perturbations generated during inflation on observable scales coming from fluctuations corresponding today to scales much bigger than the present Hubble radius. We write the effective action for the coarse grained inflaton perturbations, integrating out the sub-horizon modes, which manifest themselves as a coloured noise and lead to memory effects. Using the simple model of a scalar field with cubic self-interactions evolving in a fixed de Sitter background, we evaluate the two- and three-point correlation function on observable scales. Our basic procedure shows that perturbations do preserve some memory of the super-horizon scale dynamics, in the form of scale dependent imprints in the statistical moments. In particular, we find a blue tilt of the power spectrum on large scales, in agreement with the recent results of the WMAP collaboration which show a suppression of the lower multipoles in the cosmic microwave background anisotropies, and a substantial enhancement of the intrinsic non-Gaussianity on large scales.
International Nuclear Information System (INIS)
Finelli, Fabio; Brandenberger, Robert
2002-01-01
In pre-big-bang and in ekpyrotic cosmology, perturbations on cosmological scales today are generated from quantum vacuum fluctuations during a phase when the Universe is contracting (viewed in the Einstein frame). The backgrounds studied to date do not yield a scale-invariant spectrum of adiabatic fluctuations. Here, we present a new contracting background model (neither of pre-big-bang nor of the ekpyrotic form) involving a single scalar field coupled to gravity in which a scale-invariant spectrum of curvature fluctuations and gravitational waves results. The equation of state of this scalar field corresponds to cold matter. We demonstrate that if this contracting phase can be matched via a nonsingular bounce to an expanding Friedmann cosmology, the scale-invariance of the curvature fluctuations is maintained. We also find new background solutions for pre-big-bang and for ekpyrotic cosmology, which involve two scalar fields with exponential potentials with background values which are evolving in time. We comment on the difficulty of obtaining a scale-invariant spectrum of adiabatic fluctuations with background solutions which have been studied in the past
International Nuclear Information System (INIS)
Wesson, P.S.
1979-01-01
The Cosmological Principle states: the universe looks the same to all observers regardless of where they are located. To most astronomers today the Cosmological Principle means the universe looks the same to all observers because density of the galaxies is the same in all places. A new Cosmological Principle is proposed. It is called the Dimensional Cosmological Principle. It uses the properties of matter in the universe: density (rho), pressure (p), and mass (m) within some region of space of length (l). The laws of physics require incorporation of constants for gravity (G) and the speed of light (C). After combining the six parameters into dimensionless numbers, the best choices are: 8πGl 2 rho/c 2 , 8πGl 2 rho/c 4 , and 2 Gm/c 2 l (the Schwarzchild factor). The Dimensional Cosmological Principal came about because old ideas conflicted with the rapidly-growing body of observational evidence indicating that galaxies in the universe have a clumpy rather than uniform distribution
Duality gives rise to Chaplygin cosmologies with a big rip
International Nuclear Information System (INIS)
Chimento, Luis P; Lazkoz, Ruth
2006-01-01
We consider modifications to the Friedmann equation motivated by recent proposals along these lines pursuing an explanation to the observed late time acceleration. Here we show that these approaches can be framed within a theory with modified gravity, and we discuss the construction of the duals of the cosmologies generated within that framework. We then investigate the modifications required to generate extended, generalized and modified Chaplygin cosmologies, and then show that their duals belong to a larger family of cosmologies we call enlarged Chaplygin cosmologies. Finally, by letting the parameters of these models take values not earlier considered in the literature we show that some representatives of that family of cosmologies display sudden future singularities. This fact indicates that the behaviour of these spacetimes is rather different from that of generalized or modified Chaplygin gas cosmologies. This reinforces the idea that modifications of gravity can be responsible for unexpected evolutionary features in the universe
Energy Technology Data Exchange (ETDEWEB)
Ernazarov, K.K. [RUDN University, Institute of Gravitation and Cosmology, Moscow (Russian Federation); Ivashchuk, V.D. [RUDN University, Institute of Gravitation and Cosmology, Moscow (Russian Federation); VNIIMS, Center for Gravitation and Fundamental Metrology, Moscow (Russian Federation)
2017-06-15
We consider a D-dimensional gravitational model with a Gauss-Bonnet term and the cosmological term Λ. We restrict the metrics to diagonal cosmological ones and find for certain Λ a class of solutions with exponential time dependence of three scale factors, governed by three non-coinciding Hubble-like parameters H > 0, h{sub 1} and h{sub 2}, corresponding to factor spaces of dimensions m > 2, k{sub 1} > 1 and k{sub 2} > 1, respectively, with k{sub 1} ≠ k{sub 2} and D = 1 + m + k{sub 1} + k{sub 2}. Any of these solutions describes an exponential expansion of 3d subspace with Hubble parameter H and zero variation of the effective gravitational constant G. We prove the stability of these solutions in a class of cosmological solutions with diagonal metrics. (orig.)
New evaluation parameter for wearable thermoelectric generators
Wijethunge, Dimuthu; Kim, Woochul
2018-04-01
Wearable devices constitute a key application area for thermoelectric devices. However, owing to new constraints in wearable applications, a few conventional device optimization techniques are not appropriate and material evaluation parameters, such as figure of merit (zT) and power factor (PF), tend to be inadequate. We illustrated the incompleteness of zT and PF by performing simulations and considering different thermoelectric materials. The results indicate a weak correlation between device performance and zT and PF. In this study, we propose a new evaluation parameter, zTwearable, which is better suited for wearable applications compared to conventional zT. Owing to size restrictions, gap filler based device optimization is extremely critical in wearable devices. With respect to the occasions in which gap fillers are used, expressions for power, effective thermal conductivity (keff), and optimum load electrical ratio (mopt) are derived. According to the new parameters, the thermal conductivity of the material has become much more critical now. The proposed new evaluation parameter, namely, zTwearable, is extremely useful in the selection of an appropriate thermoelectric material among various candidates prior to the commencement of the actual design process.
Loading factor and inclination parameter of diagonal type MHD generators
International Nuclear Information System (INIS)
Ishikawa, Motoo
1979-01-01
Regarding diagonal type MHD generators is studied the relation between the loading factor and inclination parameter which is required for attaining the maximum power density with a given electrical efficiency on the assumption of infinitely segmented electrodes. The average current density on electrodes is calculated against the Hall parameter, loading factor, and inclination parameter. The diagonal type generator is compared with Faraday type generator regarding the average current density. Decreasing the loading factor from inlet to outlet is appropriate to small size generators but increasing to large size generators. The inclination parameter had better decrease in both generators, being smaller for small generators than for large ones. The average current density on electrodes of diagonal type generators varies less with the loading factor than the Faraday type. In large size generators its value can become smaller compared with that of the Faraday type. (author)
CERN. Geneva
2017-01-01
Extensions of Einstein’s theory of General Relativity are under investigation as a potential explanation of the accelerating expansion rate of the universe. I’ll present a cosmologist’s overview of attempts to test these ideas in an efficient and unbiased manner. I’ll start by introducing the bestiary of alternative gravity theories that have been put forwards. This proliferation of models motivates us to develop model-independent, agnostic tools for comparing the theory space to cosmological data. I’ll introduce the effective field theory for cosmological perturbations, a framework designed to unify modified gravity theories in terms of a manageable set of parameters. Having outlined the formalism, I’ll talk about the current constraints on this framework, and the improvements expected from the next generation of large galaxy clustering, weak lensing and intensity mapping experiments.
Aylor, K.; Hou, Z.; Knox, L.; Story, K. T.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Cho, H.-M.; Chown, R.; Crawford, T. M.; Crites, A. T.; de Haan, T.; Dobbs, M. A.; Everett, W. B.; George, E. M.; Halverson, N. W.; Harrington, N. L.; Holder, G. P.; Holzapfel, W. L.; Hrubes, J. D.; Keisler, R.; Lee, A. T.; Leitch, E. M.; Luong-Van, D.; Marrone, D. P.; McMahon, J. J.; Meyer, S. S.; Millea, M.; Mocanu, L. M.; Mohr, J. J.; Natoli, T.; Omori, Y.; Padin, S.; Pryke, C.; Reichardt, C. L.; Ruhl, J. E.; Sayre, J. T.; Schaffer, K. K.; Shirokoff, E.; Staniszewski, Z.; Stark, A. A.; Vanderlinde, K.; Vieira, J. D.; Williamson, R.
2017-11-01
The Planck cosmic microwave background temperature data are best fit with a ΛCDM model that mildly contradicts constraints from other cosmological probes. The South Pole Telescope (SPT) 2540 {\\deg }2 SPT-SZ survey offers measurements on sub-degree angular scales (multipoles 650≤slant {\\ell }≤slant 2500) with sufficient precision to use as an independent check of the Planck data. Here we build on the recent joint analysis of the SPT-SZ and Planck data in Hou et al. by comparing ΛCDM parameter estimates using the temperature power spectrum from both data sets in the SPT-SZ survey region. We also restrict the multipole range used in parameter fitting to focus on modes measured well by both SPT and Planck, thereby greatly reducing sample variance as a driver of parameter differences and creating a stringent test for systematic errors. We find no evidence of systematic errors from these tests. When we expand the maximum multipole of SPT data used, we see low-significance shifts in the angular scale of the sound horizon and the physical baryon and cold dark matter densities, with a resulting trend to higher Hubble constant. When we compare SPT and Planck data on the SPT-SZ sky patch to Planck full-sky data but keep the multipole range restricted, we find differences in the parameters n s and {A}s{e}-2τ . We perform further checks, investigating instrumental effects and modeling assumptions, and we find no evidence that the effects investigated are responsible for any of the parameter shifts. Taken together, these tests reveal no evidence for systematic errors in SPT or Planck data in the overlapping sky coverage and multipole range and at most weak evidence for a breakdown of ΛCDM or systematic errors influencing either the Planck data outside the SPT-SZ survey area or the SPT data at {\\ell }> 2000.
Energy Technology Data Exchange (ETDEWEB)
Romano, Antonio Enea [University of Crete, Department of Physics and CCTP, Heraklion (Greece); Kyoto University, Yukawa Institute for Theoretical Physics, Kyoto (Japan); Universidad de Antioquia, Instituto de Fisica, Medellin (Colombia); Vallejo, Sergio Andres [Kyoto University, Yukawa Institute for Theoretical Physics, Kyoto (Japan); Universidad de Antioquia, Instituto de Fisica, Medellin (Colombia)
2016-04-15
In order to estimate the effects of a local structure on the Hubble parameter we calculate the low-redshift expansion for H(z) and (δH)/(H) for an observer at the center of a spherically symmetric matter distribution in the presence of a cosmological constant. We then test the accuracy of the formulas comparing them with fully relativistic non-perturbative numerical calculations for different cases for the density profile. The low-redshift expansion we obtain gives results more precise than perturbation theory since it is based on the use of an exact solution of Einstein's field equations. For larger density contrasts the low-redshift formulas accuracy improves respect to the perturbation theory accuracy because the latter is based on the assumption of a small density contrast, while the former does not rely on such an assumption. The formulas can be used to take into account the effects on the Hubble expansion parameter due to the monopole component of the local structure. If the H(z) observations will show deviations from the ΛCDM prediction compatible with the formulas we have derived, this could be considered an independent evidence of the existence of a local inhomogeneity, and the formulas could be used to determine the characteristics of this local structure. (orig.)
Combination and interpretation of observables in Cosmology
Directory of Open Access Journals (Sweden)
Virey Jean-Marc
2010-04-01
Full Text Available The standard cosmological model has deep theoretical foundations but need the introduction of two major unknown components, dark matter and dark energy, to be in agreement with various observations. Dark matter describes a non-relativistic collisionless fluid of (non baryonic matter which amount to 25% of the total density of the universe. Dark energy is a new kind of fluid not of matter type, representing 70% of the total density which should explain the recent acceleration of the expansion of the universe. Alternatively, one can reject this idea of adding one or two new components but argue that the equations used to make the interpretation should be modified consmological scales. Instead of dark matter one can invoke a failure of Newton's laws. Instead of dark energy, two approaches are proposed : general relativity (in term of the Einstein equation should be modified, or the cosmological principle which fixes the metric used for cosmology should be abandonned. One of the main objective of the community is to find the path of the relevant interpretations thanks to the next generation of experiments which should provide large statistics of observationnal data. Unfortunately, cosmological in formations are difficult to pin down directly fromt he measurements, and it is mandatory to combine the various observables to get the cosmological parameters. This is not problematic from the statistical point of view, but assumptions and approximations made for the analysis may bias our interprettion of the data. Consequently, a strong attention should be paied to the statistical methods used to make parameters estimation and for model testing. After a review of the basics of cosmology where the cosmological parameters are introduced, we discuss the various cosmological probes and their associated observables used to extract cosmological informations. We present the results obtained from several statistical analyses combining data of diferent nature but
On the cosmological gravitational waves and cosmological distances
Belinski, V. A.; Vereshchagin, G. V.
2018-03-01
We show that solitonic cosmological gravitational waves propagated through the Friedmann universe and generated by the inhomogeneities of the gravitational field near the Big Bang can be responsible for increase of cosmological distances.
Audren, Benjamin; Bird, Simeon; Haehnelt, Martin G.; Viel, Matteo
2013-01-01
We present forecasts for the accuracy of determining the parameters of a minimal cosmological model and the total neutrino mass based on combined mock data for a future Euclid-like galaxy survey and Planck. We consider two different galaxy surveys: a spectroscopic redshift survey and a cosmic shear survey. We make use of the Monte Carlo Markov Chains (MCMC) technique and assume two sets of theoretical errors. The first error is meant to account for uncertainties in the modelling of the effect of neutrinos on the non-linear galaxy power spectrum and we assume this error to be fully correlated in Fourier space. The second error is meant to parametrize the overall residual uncertainties in modelling the non-linear galaxy power spectrum at small scales, and is conservatively assumed to be uncorrelated and to increase with the ratio of a given scale to the scale of non-linearity. It hence increases with wavenumber and decreases with redshift. With these two assumptions for the errors and assuming further conservat...
A method for generating subgroup parameters from resonance tables
International Nuclear Information System (INIS)
Devan, K.; Mohanakrishnan, P.
1993-01-01
A method for generating subgroup or band parameters from resonance tables is described. A computer code SPART was written using this method. This code generates the subgroup parameters for any number of bands within the specified broad groups at different temperatures by reading the required input data from the binary cross section library in the Cadarache format. The results obtained with SPART code for two bands were compared with that obtained from GROUPIE code and a good agreement was obtained. Results of the generation of subgroup parameters in four bands for sample case of 239 Pu from resonance tables of Cadarache Ver.2 library is also presented. (author). 8 refs., 2 tabs
Axions in inflationary cosmology
International Nuclear Information System (INIS)
Linde, A.
1991-01-01
The problem of the cosmological constraints on the axion mass is re-examined. It is argued that in the context of inflationary cosmology the constraint m a > or approx.10 -5 eV can be avoided even when the axion perturbations produced during inflation are taken into account. It is shown also that in most axion models the effective parameter f a rapidly changes during inflation. This modifies some earlier statements concerning isothermal perturbations in the axion cosmology. A hybrid inflation scenario is proposed which combines some advantages of chaotic inflation with specific features of new and/or extended inflation. Its implications for the axion cosmology are discussed. (orig.)
International Nuclear Information System (INIS)
Wainwright, J.
1990-01-01
The workshop on mathematical cosmology was devoted to four topics of current interest. This report contains a brief discussion of the historical background of each topic and a concise summary of the content of each talk. The topics were; the observational cosmology program, the cosmological perturbation program, isotropic singularities, and the evolution of Bianchi cosmologies. (author)
Topics in inflationary cosmologies
International Nuclear Information System (INIS)
Mahajan, S.
1986-04-01
Several aspects of inflationary cosmologies are discussed. An introduction to the standard hot big bang cosmological model is reviewed, and some of the problems associated with it are presented. A short review of the proposals for solving the cosmological conundrums of the big bang model is presented. Old and the new inflationary scenarios are discussed and shown to be unacceptable. Some alternative scenarios especially those using supersymmetry are reviewed briefly. A study is given of inflationary models where the same set of fields that breaks supersymmetry is also responsible for inflation. In these models, the scale of supersymmetry breaking is related to the slope of the potential near the origin and can thus be kept low. It is found that a supersymmetry breaking scale of the order of the weak breaking scale. The cosmology obtained from the simplest of such models is discussed in detail and it is shown that there are no particular problems except a low reheating temperature and a violation of the thermal constraint. A possible solution to the thermal constraint problem is given by introducing a second field, and the role played by this second field in the scenario is discussed. An alternative mechanism for the generation of baryon number within the framework of supergravity inflationary models is studied using the gravitational couplings of the heavy fields with the hidden sector (the sector which breaks supersymmetry). This mechanism is applied to two specific models - one with and one without supersymmetry breaking. The baryon to entropy ratio is found to be dependent on parameters which are model dependent. Finally, the effect of direct coupling between the two sectors on results is related, 88 refs., 6 figs
International Nuclear Information System (INIS)
Klebanov, I.; Susskind, L.
1988-10-01
We review Coleman's wormhole mechanism for the vanishing of the cosmological constant. We find a discouraging result that wormholes much bigger than the Planck size are generated. We also consider the implications of the wormhole theory for cosmology. 7 refs., 2 figs
van de Weygaert, Rien; van Albada, Tjeerd S.
1996-01-01
A detailed account of the ways in which a square kilometer array could further cosmological research. Observational and theoretical studies of the large scale structure and morphology of the local universe are reviewed against the potential capabilities of a new generation telescope. Cosmological
International Nuclear Information System (INIS)
Raychaudhuri, A.K.
1979-01-01
The subject is covered in chapters, entitled; introduction; Newtonian gravitation and cosmology; general relativity and relativistic cosmology; analysis of observational data; relativistic models not obeying the cosmological principle; microwave radiation background; thermal history of the universe and nucleosynthesis; singularity of cosmological models; gravitational constant as a field variable; cosmological models based on Einstein-Cartan theory; cosmological singularity in two recent theories; fate of perturbations of isotropic universes; formation of galaxies; baryon symmetric cosmology; assorted topics (including extragalactic radio sources; Mach principle). (U.K.)
Cosmology and the early universe
Di Bari, Pasquale
2018-01-01
This book discusses cosmology from both an observational and a strong theoretical perspective. The first part focuses on gravitation, notably the expansion of the universe and determination of cosmological parameters, before moving onto the main emphasis of the book, the physics of the early universe, and the connections between cosmological models and particle physics. Readers will gain a comprehensive account of cosmology and the latest observational results, without requiring prior knowledge of relativistic theories, making the text ideal for students.
Gravitational waves generated from the cosmological QCD phase transition within AdS/QCD
Directory of Open Access Journals (Sweden)
M. Ahmadvand
2017-09-01
Full Text Available We study the gravitational waves produced by the collision of the bubbles as a probe for the cosmological first order QCD phase transition, considering heavy static quarks. Using AdS/QCD and the correspondence between a first order Hawking–Page phase transition and confinement–deconfinement phase transition, we find the spectrum and the strain amplitude of the gravitational wave within the hard and soft wall models. We postulate the duration of the phase transition corresponds to the evaporation time of the black hole in the five dimensional dual gravity space, and thereby obtain a bound on the string length in the space and correspondingly on the duration of the QCD phase transition. We also show that IPTA and SKA detectors will be able to detect these gravitational waves, which can be an evidence for the first order deconfinement transition.
Modeling and Parameter Estimation of a Small Wind Generation System
Directory of Open Access Journals (Sweden)
Carlos A. Ramírez Gómez
2013-11-01
Full Text Available The modeling and parameter estimation of a small wind generation system is presented in this paper. The system consists of a wind turbine, a permanent magnet synchronous generator, a three phase rectifier, and a direct current load. In order to estimate the parameters wind speed data are registered in a weather station located in the Fraternidad Campus at ITM. Wind speed data were applied to a reference model programed with PSIM software. From that simulation, variables were registered to estimate the parameters. The wind generation system model together with the estimated parameters is an excellent representation of the detailed model, but the estimated model offers a higher flexibility than the programed model in PSIM software.
Synchronous Generator Model Parameter Estimation Based on Noisy Dynamic Waveforms
Berhausen, Sebastian; Paszek, Stefan
2016-01-01
In recent years, there have occurred system failures in many power systems all over the world. They have resulted in a lack of power supply to a large number of recipients. To minimize the risk of occurrence of power failures, it is necessary to perform multivariate investigations, including simulations, of power system operating conditions. To conduct reliable simulations, the current base of parameters of the models of generating units, containing the models of synchronous generators, is necessary. In the paper, there is presented a method for parameter estimation of a synchronous generator nonlinear model based on the analysis of selected transient waveforms caused by introducing a disturbance (in the form of a pseudorandom signal) in the generator voltage regulation channel. The parameter estimation was performed by minimizing the objective function defined as a mean square error for deviations between the measurement waveforms and the waveforms calculated based on the generator mathematical model. A hybrid algorithm was used for the minimization of the objective function. In the paper, there is described a filter system used for filtering the noisy measurement waveforms. The calculation results of the model of a 44 kW synchronous generator installed on a laboratory stand of the Institute of Electrical Engineering and Computer Science of the Silesian University of Technology are also given. The presented estimation method can be successfully applied to parameter estimation of different models of high-power synchronous generators operating in a power system.
Cosmological production of noncommutative black holes
International Nuclear Information System (INIS)
Mann, Robert B.; Nicolini, Piero
2011-01-01
We investigate the pair creation of noncommutative black holes in a background with a positive cosmological constant. As a first step we derive the noncommutative geometry inspired Schwarzschild-de Sitter solution. By varying the mass and the cosmological constant parameters, we find several spacetimes compatible with the new solution: positive-mass spacetimes admit one cosmological horizon and two, one, or no black hole horizons, while negative-mass spacetimes have just a cosmological horizon. These new black holes share the properties of the corresponding asymptotically flat solutions, including the nonsingular core and thermodynamic stability in the final phase of the evaporation. As a second step we determine the action which generates the matter sector of gravitational field equations and we construct instantons describing the pair production of black holes and the other admissible topologies. As a result we find that for current values of the cosmological constant the de Sitter background is quantum mechanically stable according to experience. However, positive-mass noncommutative black holes and solitons would have plentifully been produced during inflationary times for Planckian values of the cosmological constant. As a special result we find that, in these early epochs of the Universe, Planck size black holes production would have been largely disfavored. We also find a potential instability for production of negative-mass solitons.
International Nuclear Information System (INIS)
Kehagias, A.; Riotto, A.
2016-01-01
Symmetries play an interesting role in cosmology. They are useful in characterizing the cosmological perturbations generated during inflation and lead to consistency relations involving the soft limit of the statistical correlators of large-scale structure dark matter and galaxies overdensities. On the other hand, in observational cosmology the carriers of the information about these large-scale statistical distributions are light rays traveling on null geodesics. Motivated by this simple consideration, we study the structure of null infinity and the associated BMS symmetry in a cosmological setting. For decelerating Friedmann-Robertson-Walker backgrounds, for which future null infinity exists, we find that the BMS transformations which leaves the asymptotic metric invariant to leading order. Contrary to the asymptotic flat case, the BMS transformations in cosmology generate Goldstone modes corresponding to scalar, vector and tensor degrees of freedom which may exist at null infinity and perturb the asymptotic data. Therefore, BMS transformations generate physically inequivalent vacua as they populate the universe at null infinity with these physical degrees of freedom. We also discuss the gravitational memory effect when cosmological expansion is taken into account. In this case, there are extra contribution to the gravitational memory due to the tail of the retarded Green functions which are supported not only on the light-cone, but also in its interior. The gravitational memory effect can be understood also from an asymptotic point of view as a transition among cosmological BMS-related vacua.
Energy Technology Data Exchange (ETDEWEB)
Kehagias, A. [Physics Division, National Technical University of Athens, 15780 Zografou Campus, Athens (Greece); Riotto, A. [Department of Theoretical Physics,24 quai E. Ansermet, CH-1211 Geneva 4 (Switzerland); Center for Astroparticle Physics (CAP),24 quai E. Ansermet, CH-1211 Geneva 4 (Switzerland)
2016-05-25
Symmetries play an interesting role in cosmology. They are useful in characterizing the cosmological perturbations generated during inflation and lead to consistency relations involving the soft limit of the statistical correlators of large-scale structure dark matter and galaxies overdensities. On the other hand, in observational cosmology the carriers of the information about these large-scale statistical distributions are light rays traveling on null geodesics. Motivated by this simple consideration, we study the structure of null infinity and the associated BMS symmetry in a cosmological setting. For decelerating Friedmann-Robertson-Walker backgrounds, for which future null infinity exists, we find that the BMS transformations which leaves the asymptotic metric invariant to leading order. Contrary to the asymptotic flat case, the BMS transformations in cosmology generate Goldstone modes corresponding to scalar, vector and tensor degrees of freedom which may exist at null infinity and perturb the asymptotic data. Therefore, BMS transformations generate physically inequivalent vacua as they populate the universe at null infinity with these physical degrees of freedom. We also discuss the gravitational memory effect when cosmological expansion is taken into account. In this case, there are extra contribution to the gravitational memory due to the tail of the retarded Green functions which are supported not only on the light-cone, but also in its interior. The gravitational memory effect can be understood also from an asymptotic point of view as a transition among cosmological BMS-related vacua.
International Nuclear Information System (INIS)
Landsberg, P.T.; Evans, D.A.
1977-01-01
The subject is dealt with in chapters, entitled: cosmology -some fundamentals; Newtonian gravitation - some fundamentals; the cosmological differential equation - the particle model and the continuum model; some simple Friedmann models; the classification of the Friedmann models; the steady-state model; universe with pressure; optical effects of the expansion according to various theories of light; optical observations and cosmological models. (U.K.)
Energy Technology Data Exchange (ETDEWEB)
Simard, G.; et al.
2017-12-20
We report constraints on cosmological parameters from the angular power spectrum of a cosmic microwave background (CMB) gravitational lensing potential map created using temperature data from 2500 deg$^2$ of South Pole Telescope (SPT) data supplemented with data from Planck in the same sky region, with the statistical power in the combined map primarily from the SPT data. We fit the corresponding lensing angular power spectrum to a model including cold dark matter and a cosmological constant ($\\Lambda$CDM), and to models with single-parameter extensions to $\\Lambda$CDM. We find constraints that are comparable to and consistent with constraints found using the full-sky Planck CMB lensing data. Specifically, we find $\\sigma_8 \\Omega_{\\rm m}^{0.25}=0.598 \\pm 0.024$ from the lensing data alone with relatively weak priors placed on the other $\\Lambda$CDM parameters. In combination with primary CMB data from Planck, we explore single-parameter extensions to the $\\Lambda$CDM model. We find $\\Omega_k = -0.012^{+0.021}_{-0.023}$ or $M_{\
Effect of economic parameters on power generation expansion planning
International Nuclear Information System (INIS)
Sevilgen, Sueleyman Hakan; Hueseyin Erdem, Hasan; Cetin, Burhanettin; Volkan Akkaya, Ali; Dagdas, Ahmet
2005-01-01
The increasing consumption of electricity within time forces countries to build additional power plants. Because of technical and economic differences of the additional power plants, economic methodologies are used to determine the best technology for the additional capacity. The annual levelized cost method is used for this purpose, and the technology giving the minimum value for the additional load range is chosen. However, the economic parameters such as interest rate, construction escalation, fuel escalation, maintenance escalation and discount factor can affect the annual levelized cost considerably and change the economic range of the plants. Determining the values of the economical parameters in the future is very difficult, especially in developing countries. For this reason, the analysis of the changing rates of the mentioned values is of great importance for the planners of the additional capacity. In this study, the changing rates of the economic parameters that influence the annual levelized cost of the alternative power plant types are discussed. The alternative power plants considered for the electricity generation sector of Turkey and the economic parameters dominating each plant type are determined. It is clearly seen that the annual levelized cost for additional power plants varies with the economic parameters. The results show that the economic parameters variation has to be taken into consideration in electricity generation planning
Energy Technology Data Exchange (ETDEWEB)
Linden, S.
2010-04-15
The measured properties of the dark energy component being consistent with a Cosmological Constant, {Lambda}, this cosmological standard model is referred to as the {Lambda}-Cold-Dark-Matter ({Lambda}CDM) model. Despite its overall success, this model suffers from various problems. The existence of a Cosmological Constant raises fundamental questions. Attempts to describe it as the energy contribution from the vacuum as following from Quantum Field Theory failed quantitatively. In consequence, a large number of alternative models have been developed to describe the dark energy component: modified gravity, additional dimensions, Quintessence models. Also, astrophysical effects have been considered to mimic an accelerated expansion. The basics of the {Lambda}CDM model and the various attempts of explaining dark energy are outlined in this thesis. Another major problem of the model comes from the dependencies of the fit results on a number of a priori assumptions and parameterization effects. Today, combined analyses of the various cosmological probes are performed to extract the parameters of the model. Due to a wrong model assumption or a bad parameterization of the real physics, one might end up measuring with high precision something which is not there. We show, that indeed due to the high precision of modern cosmological measurements, purely kinematic approaches to distance measurements no longer yield valid fit results except for accidental special cases, and that a fit of the exact (integral) redshift-distance relation is necessary. The main results of this work concern the use of the CPL parameterization of dark energy when coping with the dynamics of tracker solutions of Quintessence models, and the risk of introducing biases on the parameters due to the possibly prohibited extrapolation to arbitrary high redshifts of the SN type Ia magnitude calibration relation, which is obtained in the low-redshift regime. Whereas the risks of applying CPL shows up to be
Stability analysis in tachyonic potential chameleon cosmology
International Nuclear Information System (INIS)
Farajollahi, H.; Salehi, A.; Tayebi, F.; Ravanpak, A.
2011-01-01
We study general properties of attractors for tachyonic potential chameleon scalar-field model which possess cosmological scaling solutions. An analytic formulation is given to obtain fixed points with a discussion on their stability. The model predicts a dynamical equation of state parameter with phantom crossing behavior for an accelerating universe. We constrain the parameters of the model by best fitting with the recent data-sets from supernovae and simulated data points for redshift drift experiment generated by Monte Carlo simulations
Stability analysis in tachyonic potential chameleon cosmology
Energy Technology Data Exchange (ETDEWEB)
Farajollahi, H.; Salehi, A.; Tayebi, F.; Ravanpak, A., E-mail: hosseinf@guilan.ac.ir, E-mail: a.salehi@guilan.ac.ir, E-mail: ftayebi@guilan.ac.ir, E-mail: aravanpak@guilan.ac.ir [Department of Physics, University of Guilan, Rasht (Iran, Islamic Republic of)
2011-05-01
We study general properties of attractors for tachyonic potential chameleon scalar-field model which possess cosmological scaling solutions. An analytic formulation is given to obtain fixed points with a discussion on their stability. The model predicts a dynamical equation of state parameter with phantom crossing behavior for an accelerating universe. We constrain the parameters of the model by best fitting with the recent data-sets from supernovae and simulated data points for redshift drift experiment generated by Monte Carlo simulations.
Cosmological applications in Kaluza—Klein theory
International Nuclear Information System (INIS)
Wanas, M.I.; Nashed, Gamal G. L.; Nowaya, A.A.
2012-01-01
The field equations of Kaluza—Klein (KK) theory have been applied in the domain of cosmology. These equations are solved for a flat universe by taking the gravitational and the cosmological constants as a function of time t. We use Taylor's expansion of cosmological function, Λ(t), up to the first order of the time t. The cosmological parameters are calculated and some cosmological problems are discussed. (geophysics, astronomy, and astrophysics)
Observable cosmology and cosmological models
International Nuclear Information System (INIS)
Kardashev, N.S.; Lukash, V.N.; Novikov, I.D.
1987-01-01
Modern state of observation cosmology is briefly discussed. Among other things, a problem, related to Hibble constant and slowdown constant determining is considered. Within ''pancake'' theory hot (neutrino) cosmological model explains well the large-scale structure of the Universe, but does not explain the galaxy formation. A cold cosmological model explains well light object formation, but contradicts data on large-scale structure
Zhang Yuan Zhong
2002-01-01
This book is one of a series in the areas of high-energy physics, cosmology and gravitation published by the Institute of Physics. It includes courses given at a doctoral school on 'Relativistic Cosmology: Theory and Observation' held in Spring 2000 at the Centre for Scientific Culture 'Alessandro Volta', Italy, sponsored by SIGRAV-Societa Italiana di Relativita e Gravitazione (Italian Society of Relativity and Gravitation) and the University of Insubria. This book collects 15 review reports given by a number of outstanding scientists. They touch upon the main aspects of modern cosmology from observational matters to theoretical models, such as cosmological models, the early universe, dark matter and dark energy, modern observational cosmology, cosmic microwave background, gravitational lensing, and numerical simulations in cosmology. In particular, the introduction to the basics of cosmology includes the basic equations, covariant and tetrad descriptions, Friedmann models, observation and horizons, etc. The ...
Monte Carlo generation of dosimetric parameters for eye plaque dosimetry
International Nuclear Information System (INIS)
Cutajar, D.L.; Green, J.A.; Guatelli, S.; Rosenfeld, A.B.
2010-01-01
Full text: The Centre for Medical Radiation Physics have undertaken the dcvelopment of a quality assurance tool, using silicon pixelated detectors, for the calibration of eye plaques prior to insertion. Dosimetric software to correlate the measured and predicted dose rates has been constructed. The dosimetric parameters within the software, for both 1-125 and Ru-I 06 based eye plaques, were optimised using the Geant4 Monte Carlo toolkit. Methods For 1-125 based plaques, an novel application was developed to generate TG-43 parameters for any seed input. TG-43 parameters were generated for an Oncura model 6711 seed, with data points every millimetre up to 25 mm in the radial direction, and every 5 degrees in polar angle, and correlated to published data. For the Ru106 based plaques, an application was developed to generate dose rates about a Bebig model CCD plaque. Toroids were used to score the deposited dose, taking advantage of the cylindrical symmetry of the plaque, with radii in millimetre increments up to 25 mm, and depth from the plaque surface in millimetre increments up to 25 mm. Results TheTG43 parameters generated for the 6711 seed correlate well with published TG43 data at the given intervals, with radial dose function within 3%, and anisotropy function within 5% for angles greater than 30 degrees. The Ru-l 06 plaque data correlated well with the Bebig protocol of measurement. Conclusion Geant4 is a useful Monte Carlo tool for the generation of dosimetric data for eye plaque dosimetry. which may improve the quality assurance of eye plaque treatment. (author)
Cosmology and particle physics
International Nuclear Information System (INIS)
Barrow, J.D.
1982-01-01
A brief overview is given of recent work that integrates cosmology and particle physics. The observational data regarding the abundance of matter and radiation in the Universe is described. The manner in which the cosmological survival density of stable massive particles can be calculated is discussed along with the process of cosmological nucleosynthesis. Several applications of these general arguments are given with reference to the survival density of nucleons, neutrinos and unconfined fractionally charge particles. The use of nucleosynthesis to limit the number of lepton generations is described together with the implications of a small neutrino mass for the origin of galaxies and clusters. (Auth.)
Seismic analysis of steam generator and parameter sensitivity studies
International Nuclear Information System (INIS)
Qian Hao; Xu Dinggen; Yang Ren'an; Liang Xingyun
2013-01-01
Background: The steam generator (SG) serves as the primary means for removing the heat generated within the reactor core and is part of the reactor coolant system (RCS) pressure boundary. Purpose: Seismic analysis in required for SG, whose seismic category is Cat. I. Methods: The analysis model of SG is created with moisture separator assembly and tube bundle assembly herein. The seismic analysis is performed with RCS pipe and Reactor Pressure Vessel (RPV). Results: The seismic stress results of SG are obtained. In addition, parameter sensitivities of seismic analysis results are studied, such as the effect of another SG, support, anti-vibration bars (AVBs), and so on. Our results show that seismic results are sensitive to support and AVBs setting. Conclusions: The guidance and comments on these parameters are summarized for equipment design and analysis, which should be focused on in future new type NPP SG's research and design. (authors)
Entropy generation and inflation in collision induced pre-big-bang cosmology
Feinstein, A.; Kunze, K.E.; Vazquez-Mozo, M.A.
2000-01-01
We study inflation and entropy generation in a recently proposed pre-big-bang model universe produced in a collision of gravitational and dilaton waves. It is shown that enough inflation occurs provided the incoming waves are sufficiently weak. We also find that entropy in this model is dynamically
Fast optimization algorithms and the cosmological constant
Bao, Ning; Bousso, Raphael; Jordan, Stephen; Lackey, Brad
2017-11-01
Denef and Douglas have observed that in certain landscape models the problem of finding small values of the cosmological constant is a large instance of a problem that is hard for the complexity class NP (Nondeterministic Polynomial-time). The number of elementary operations (quantum gates) needed to solve this problem by brute force search exceeds the estimated computational capacity of the observable Universe. Here we describe a way out of this puzzling circumstance: despite being NP-hard, the problem of finding a small cosmological constant can be attacked by more sophisticated algorithms whose performance vastly exceeds brute force search. In fact, in some parameter regimes the average-case complexity is polynomial. We demonstrate this by explicitly finding a cosmological constant of order 10-120 in a randomly generated 1 09-dimensional Arkani-Hamed-Dimopoulos-Kachru landscape.
Cosmological evolution as squeezing: a toy model for group field cosmology
Adjei, Eugene; Gielen, Steffen; Wieland, Wolfgang
2018-05-01
We present a simple model of quantum cosmology based on the group field theory (GFT) approach to quantum gravity. The model is formulated on a subspace of the GFT Fock space for the quanta of geometry, with a fixed volume per quantum. In this Hilbert space, cosmological expansion corresponds to the generation of new quanta. Our main insight is that the evolution of a flat Friedmann–Lemaître–Robertson–Walker universe with a massless scalar field can be described on this Hilbert space as squeezing, familiar from quantum optics. As in GFT cosmology, we find that the three-volume satisfies an effective Friedmann equation similar to the one of loop quantum cosmology, connecting the classical contracting and expanding solutions by a quantum bounce. The only free parameter in the model is identified with Newton’s constant. We also comment on the possible topological interpretation of our squeezed states. This paper can serve as an introduction into the main ideas of GFT cosmology without requiring the full GFT formalism; our results can also motivate new developments in GFT and its cosmological application.
International Nuclear Information System (INIS)
Nojiri, S; Odintsov, S D; Oikonomou, V K
2016-01-01
We combine the unimodular gravity and mimetic gravity theories into a unified theoretical framework, which is proposed to provide a suggestive proposal for a framework that may assist in the discussion and search for a solution to the cosmological constant problem and the dark matter issue. After providing the formulation of the unimodular mimetic gravity and investigating all the new features that the vacuum unimodular gravity implies, by using the underlying reconstruction method, we realize some well known cosmological evolutions, with some of these being exotic for the ordinary Einstein–Hilbert gravity. Specifically we provide the vacuum unimodular mimetic gravity description of the de Sitter cosmology and of the perfect fluid with constant equation of state cosmology. As we demonstrate, these cosmologies can be realized by vacuum mimetic unimodular gravity, without the existence of any matter fluid source. Moreover, we investigate how cosmologically viable cosmologies, which are compatible with the recent observational data, can be realized by the vacuum unimodular mimetic gravity. Since in some cases, a graceful exit from inflation problem might exist, we provide a qualitative description of the mechanism that can potentially generate the graceful exit from inflation in these theories, by searching for the unstable de Sitter solutions in the context of unimodular mimetic theories of gravity. (paper)
Axion cold dark matter in nonstandard cosmologies
International Nuclear Information System (INIS)
Visinelli, Luca; Gondolo, Paolo
2010-01-01
We study the parameter space of cold dark matter axions in two cosmological scenarios with nonstandard thermal histories before big bang nucleosynthesis: the low-temperature reheating (LTR) cosmology and the kination cosmology. If the Peccei-Quinn symmetry breaks during inflation, we find more allowed parameter space in the LTR cosmology than in the standard cosmology and less in the kination cosmology. On the contrary, if the Peccei-Quinn symmetry breaks after inflation, the Peccei-Quinn scale is orders of magnitude higher than standard in the LTR cosmology and lower in the kination cosmology. We show that the axion velocity dispersion may be used to distinguish some of these nonstandard cosmologies. Thus, axion cold dark matter may be a good probe of the history of the Universe before big bang nucleosynthesis.
International Nuclear Information System (INIS)
Meusburger, C.; Schroers, B. J.
2008-01-01
Each of the local isometry groups arising in three-dimensional (3d) gravity can be viewed as a group of unit (split) quaternions over a ring which depends on the cosmological constant. In this paper we explain and prove this statement and use it as a unifying framework for studying Poisson structures associated with the local isometry groups. We show that, in all cases except for the case of Euclidean signature with positive cosmological constant, the local isometry groups are equipped with the Poisson-Lie structure of a classical double. We calculate the dressing action of the factor groups on each other and find, among others, a simple and unified description of the symplectic leaves of SU(2) and SL(2,R). We also compute the Poisson structure on the dual Poisson-Lie groups of the local isometry groups and on their Heisenberg doubles; together, they determine the Poisson structure of the phase space of 3d gravity in the so-called combinatorial description
Cosmological evidence for leptonic asymmetry after Planck
Energy Technology Data Exchange (ETDEWEB)
Caramete, A.; Popa, L.A., E-mail: acaramete@spacescience.ro, E-mail: lpopa@spacescience.ro [Institute of Space Science, 409 Atomistilor Street, Magurele, Ilfov 077125 (Romania)
2014-02-01
Recently, the PLANCK satellite found a larger and most precise value of the matter energy density, that impacts on the present values of other cosmological parameters such as the Hubble constant H{sub 0}, the present cluster abundances S{sub 8}, and the age of the Universe t{sub U}. The existing tension between PLANCK determination of these parameters in the frame of the base ΛCDM model and their determination from other measurements generated lively discussions, one possible interpretation being that some sources of systematic errors in cosmological measurements are not completely understood. An alternative interpretation is related to the fact that the CMB observations, that probe the high redshift Universe are interpreted in terms of cosmological parameters at present time by extrapolation within the base ΛCDM model that can be inadequate or incomplete. In this paper we quantify this tension by exploring several extensions of the base ΛCDM model that include the leptonic asymmetry. We set bounds on the radiation content of the Universe and neutrino properties by using the latest cosmological measurements, imposing also self-consistent BBN constraints on the primordial helium abundance. For all asymmetric cosmological models we find the preference of cosmological data for smaller values of active and sterile neutrino masses. This increases the tension between cosmological and short baseline neutrino oscillation data that favors a sterile neutrino with the mass of around 1 eV. For the case of degenerate massive neutrinos, we find that the discrepancies with the local determinations of H{sub 0}, and t{sub U} are alleviated at ∼ 1.3σ level while S{sub 8} is in agreement with its determination from CFHTLenS survey data at ∼ 1σ and with the prediction of cluster mass-observation relation at ∼ 0.5σ. We also find 2σ statistical preference of the cosmological data for the leptonic asymmetric models involving three massive neutrino species and neutrino direct
Cosmological Probes for Supersymmetry
Directory of Open Access Journals (Sweden)
Maxim Khlopov
2015-05-01
Full Text Available The multi-parameter character of supersymmetric dark-matter models implies the combination of their experimental studies with astrophysical and cosmological probes. The physics of the early Universe provides nontrivial effects of non-equilibrium particles and primordial cosmological structures. Primordial black holes (PBHs are a profound signature of such structures that may arise as a cosmological consequence of supersymmetric (SUSY models. SUSY-based mechanisms of baryosynthesis can lead to the possibility of antimatter domains in a baryon asymmetric Universe. In the context of cosmoparticle physics, which studies the fundamental relationship of the micro- and macro-worlds, the development of SUSY illustrates the main principles of this approach, as the physical basis of the modern cosmology provides cross-disciplinary tests in physical and astronomical studies.
Jones, Bernard J. T.
2017-04-01
Preface; Notation and conventions; Part I. 100 Years of Cosmology: 1. Emerging cosmology; 2. The cosmic expansion; 3. The cosmic microwave background; 4. Recent cosmology; Part II. Newtonian Cosmology: 5. Newtonian cosmology; 6. Dark energy cosmological models; 7. The early universe; 8. The inhomogeneous universe; 9. The inflationary universe; Part III. Relativistic Cosmology: 10. Minkowski space; 11. The energy momentum tensor; 12. General relativity; 13. Space-time geometry and calculus; 14. The Einstein field equations; 15. Solutions of the Einstein equations; 16. The Robertson-Walker solution; 17. Congruences, curvature and Raychaudhuri; 18. Observing and measuring the universe; Part IV. The Physics of Matter and Radiation: 19. Physics of the CMB radiation; 20. Recombination of the primeval plasma; 21. CMB polarisation; 22. CMB anisotropy; Part V. Precision Tools for Precision Cosmology: 23. Likelihood; 24. Frequentist hypothesis testing; 25. Statistical inference: Bayesian; 26. CMB data processing; 27. Parametrising the universe; 28. Precision cosmology; 29. Epilogue; Appendix A. SI, CGS and Planck units; Appendix B. Magnitudes and distances; Appendix C. Representing vectors and tensors; Appendix D. The electromagnetic field; Appendix E. Statistical distributions; Appendix F. Functions on a sphere; Appendix G. Acknowledgements; References; Index.
Conformal Cosmology and Supernova Data
Behnke, Danilo; Blaschke, David; Pervushin, Victor; Proskurin, Denis
2000-01-01
We define the cosmological parameters $H_{c,0}$, $\\Omega_{m,c}$ and $\\Omega_{\\Lambda, c}$ within the Conformal Cosmology as obtained by the homogeneous approximation to the conformal-invariant generalization of Einstein's General Relativity theory. We present the definitions of the age of the universe and of the luminosity distance in the context of this approach. A possible explanation of the recent data from distant supernovae Ia without a cosmological constant is presented.
Perspectives on Gamma-Ray Burst Physics and Cosmology with Next Generation Facilities
Yuan, Weimin; Amati, Lorenzo; Cannizzo, John K.; Cordier, Bertrand; Gehrels, Neil; Ghirlanda, Giancarlo; Götz, Diego; Produit, Nicolas; Qiu, Yulei; Sun, Jianchao; Tanvir, Nial R.; Wei, Jianyan; Zhang, Chen
2016-12-01
High-redshift Gamma-Ray Bursts (GRBs) beyond redshift {˜}6 are potentially powerful tools to probe the distant early Universe. Their detections in large numbers and at truly high redshifts call for the next generation of high-energy wide-field instruments with unprecedented sensitivity at least one order of magnitude higher than the ones currently in orbit. On the other hand, follow-up observations of the afterglows of high-redshift GRBs and identification of their host galaxies, which would be difficult for the currently operating telescopes, require new, extremely large facilities of at multi-wavelengths. This chapter describes future experiments that are expected to advance this exciting field, both being currently built and being proposed. The legacy of Swift will be continued by SVOM, which is equipped with a set of space-based multi-wavelength instruments as well as and a ground segment including a wide angle camera and two follow-up telescopes. The established Lobster-eye X-ray focusing optics provides a promising technology for the detection of faint GRBs at very large distances, based on which the THESEUS, Einstein Probe and other mission concepts have been proposed. Follow-up observations and exploration of the reionization era will be enabled by large facilities such as SKA in the radio, the 30 m class telescopes in the optical/near-IR, and the space-borne WFIRST and JWST in the optical/near-IR/mid-IR. In addition, the X-ray and γ-ray polarization experiment POLAR is also introduced.
Energy Technology Data Exchange (ETDEWEB)
Maurya, D. Ch., E-mail: dcmaurya563@gmail.com; Zia, R., E-mail: rashidzya@gmail.com; Pradhan, A., E-mail: pradhan.anirudh@gmail.com [GLA University, Department of Mathematics, Institute of Applied Sciences and Humanities (India)
2016-10-15
We discuss a spatially homogeneous and anisotropic string cosmological models in the Brans–Dicke theory of gravitation. For a spatially homogeneous metric, it is assumed that the expansion scalar θ is proportional to the shear scalar σ. This condition leads to A = kB{sup m}, where k and m are constants. With these assumptions and also assuming a variable scale factor a = a(t), we find solutions of the Brans–Dicke field equations. Various phenomena like the Big Bang, expanding universe, and shift from anisotropy to isotropy are observed in the model. It can also be seen that in early stage of the evolution of the universe, strings dominate over particles, whereas the universe is dominated by massive strings at the late time. Some physical and geometrical behaviors of the models are also discussed and observed to be in good agreement with the recent observations of SNe la supernovae.
Sanders, RH; Papantonopoulos, E
2005-01-01
I discuss the classical cosmological tests, i.e., angular size-redshift, flux-redshift, and galaxy number counts, in the light of the cosmology prescribed by the interpretation of the CMB anisotropies. The discussion is somewhat of a primer for physicists, with emphasis upon the possible systematic
ADVANTG An Automated Variance Reduction Parameter Generator, Rev. 1
Energy Technology Data Exchange (ETDEWEB)
Mosher, Scott W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Johnson, Seth R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Bevill, Aaron M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Ibrahim, Ahmad M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Daily, Charles R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Evans, Thomas M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Wagner, John C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Johnson, Jeffrey O. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Grove, Robert E. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2015-08-01
The primary objective of ADVANTG is to reduce both the user effort and the computational time required to obtain accurate and precise tally estimates across a broad range of challenging transport applications. ADVANTG has been applied to simulations of real-world radiation shielding, detection, and neutron activation problems. Examples of shielding applications include material damage and dose rate analyses of the Oak Ridge National Laboratory (ORNL) Spallation Neutron Source and High Flux Isotope Reactor (Risner and Blakeman 2013) and the ITER Tokamak (Ibrahim et al. 2011). ADVANTG has been applied to a suite of radiation detection, safeguards, and special nuclear material movement detection test problems (Shaver et al. 2011). ADVANTG has also been used in the prediction of activation rates within light water reactor facilities (Pantelias and Mosher 2013). In these projects, ADVANTG was demonstrated to significantly increase the tally figure of merit (FOM) relative to an analog MCNP simulation. The ADVANTG-generated parameters were also shown to be more effective than manually generated geometry splitting parameters.
Efficient exploration of cosmology dependence in the EFT of LSS
Energy Technology Data Exchange (ETDEWEB)
Cataneo, Matteo [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen (Denmark); Foreman, Simon; Senatore, Leonardo, E-mail: matteoc@dark-cosmology.dk, E-mail: sfore@stanford.edu, E-mail: senatore@stanford.edu [Stanford Institute for Theoretical Physics and Department of Physics, Stanford University, 382 Via Pueblo Mall, Stanford, CA 94306 (United States)
2017-04-01
The most effective use of data from current and upcoming large scale structure (LSS) and CMB observations requires the ability to predict the clustering of LSS with very high precision. The Effective Field Theory of Large Scale Structure (EFTofLSS) provides an instrument for performing analytical computations of LSS observables with the required precision in the mildly nonlinear regime. In this paper, we develop efficient implementations of these computations that allow for an exploration of their dependence on cosmological parameters. They are based on two ideas. First, once an observable has been computed with high precision for a reference cosmology, for a new cosmology the same can be easily obtained with comparable precision just by adding the difference in that observable, evaluated with much less precision. Second, most cosmologies of interest are sufficiently close to the Planck best-fit cosmology that observables can be obtained from a Taylor expansion around the reference cosmology. These ideas are implemented for the matter power spectrum at two loops and are released as public codes. When applied to cosmologies that are within 3σ of the Planck best-fit model, the first method evaluates the power spectrum in a few minutes on a laptop, with results that have 1% or better precision, while with the Taylor expansion the same quantity is instantly generated with similar precision. The ideas and codes we present may easily be extended for other applications or higher-precision results.
Modified General Relativity and Cosmology
Abdel-Rahman, A.-M. M.
1997-10-01
Aspects of the modified general relativity theory of Rastall, Al-Rawaf and Taha are discussed in both the radiation- and matter-dominated flat cosmological models. A nucleosynthesis constraint on the theory's free parameter is obtained and the implication for the age of the Universe is discussed. The consistency of the modified matter- dominated model with the neoclassical cosmological tests is demonstrated.
Cosmological effects of nonlinear electrodynamics
International Nuclear Information System (INIS)
Novello, M; Goulart, E; Salim, J M; Bergliaffa, S E Perez
2007-01-01
It will be shown that a given realization of nonlinear electrodynamics, used as a source of Einstein's equations, generates a cosmological model with interesting features, namely a phase of current cosmic acceleration, and the absence of an initial singularity, thus pointing to a way of solving two important problems in cosmology
Producing a scale-invariant spectrum of perturbations in a Hagedorn phase of string cosmology.
Nayeri, Ali; Brandenberger, Robert H; Vafa, Cumrun
2006-07-14
We study the generation of cosmological perturbations during the Hagedorn phase of string gas cosmology. Using tools of string thermodynamics we provide indications that it may be possible to obtain a nearly scale-invariant spectrum of cosmological fluctuations on scales which are of cosmological interest today. In our cosmological scenario, the early Hagedorn phase of string gas cosmology goes over smoothly into the radiation-dominated phase of standard cosmology, without having a period of cosmological inflation.
International Nuclear Information System (INIS)
Leibundgut, B.
2005-01-01
Supernovae have developed into a versatile tool for cosmology. Their impact on the cosmological model has been profound and led to the discovery of the accelerated expansion. The current status of the cosmological model as perceived through supernova observations will be presented. Supernovae are currently the only astrophysical objects that can measure the dynamics of the cosmic expansion during the past eight billion years. Ongoing experiments are trying to determine the characteristics of the accelerated expansion and give insight into what might be the physical explanation for the acceleration. (author)
Estimation of common cause failure parameters for diesel generators
International Nuclear Information System (INIS)
Tirira, J.; Lanore, J.M.
2002-10-01
This paper presents a summary of some results concerning the feedback analysis of French Emergency diesel generator (EDG). The database of common cause failure for EDG has been updated. The data collected covers a period of 10 years. Several latent common cause failure (CCF) events counting in tens are identified. In fact, in this number of events collected, most are potential CCF. From events identified, 15% events are characterized as complete CCF. The database is organised following the structure proposed by 'International Common Cause Data Exchange' (ICDE project). Events collected are analyzed by failure mode and degree of failure. Qualitative analysis of root causes, coupling factors and corrective actions are studied. The exercise of quantitative analysis is in progress for evaluating CCF parameters taking into account the average impact vector and the rate of the independent failures. The interest of the average impact vector approach is that it makes it possible to take into account a wide experience feedback, not limited to complete CCF but including also many events related to partial or potential CCF. It has to be noted that there are no finalized quantitative conclusions yet to be drawn and analysis is in progress for evaluating diesel CCF parameters. In fact, the numerical coding CCF representation of the events uses a part of subjective analysis, which requests a complete and detailed event examination. (authors)
Effect of flow parameters on flare stack generator noise
International Nuclear Information System (INIS)
Dinn, T.S.
1998-01-01
The SoundPLAN Computer Noise Model was used to determine the general effect of flare noise in a community adjacent to a petrochemical plant. Tests were conducted to determine the effect of process flow conditions and the pulsating flame on the flare stack generator noise from both a refinery flare and process flare. Flaring under normal plant operations, the flaring of fuel gas and the flaring of hydrogen were the three conditions that were tested. It was shown that the steam flow rate was the determining factor in the flare stack generated noise. Variations in the water seal level in the flare line surge tank increased or decreased the gas flowrate, which resulted in a pulsating flame. The period and amplitude of the pulsating noise from the flare stacks was determined by measuring several parameters. Flare stack noise oscillations were found to be greater for the process flare than for the refinery flare stack. It was suggested that minimizing the amount of steam fed to the flare and improving the burner design would minimize noise. 2 tabs., 6 figs
Parameters of oscillation generation regions in open star cluster models
Danilov, V. M.; Putkov, S. I.
2017-07-01
We determine the masses and radii of central regions of open star cluster (OCL) models with small or zero entropy production and estimate the masses of oscillation generation regions in clustermodels based on the data of the phase-space coordinates of stars. The radii of such regions are close to the core radii of the OCL models. We develop a new method for estimating the total OCL masses based on the cluster core mass, the cluster and cluster core radii, and radial distribution of stars. This method yields estimates of dynamical masses of Pleiades, Praesepe, and M67, which agree well with the estimates of the total masses of the corresponding clusters based on proper motions and spectroscopic data for cluster stars.We construct the spectra and dispersion curves of the oscillations of the field of azimuthal velocities v φ in OCL models. Weak, low-amplitude unstable oscillations of v φ develop in cluster models near the cluster core boundary, and weak damped oscillations of v φ often develop at frequencies close to the frequencies of more powerful oscillations, which may reduce the non-stationarity degree in OCL models. We determine the number and parameters of such oscillations near the cores boundaries of cluster models. Such oscillations points to the possible role that gradient instability near the core of cluster models plays in the decrease of the mass of the oscillation generation regions and production of entropy in the cores of OCL models with massive extended cores.
International Nuclear Information System (INIS)
Berstein, J.
1984-01-01
These lectures offer a self-contained review of the role of neutrinos in cosmology. The first part deals with the question 'What is a neutrino.' and describes in a historical context the theoretical ideas and experimental discoveries related to the different types of neutrinos and their properties. The basic differences between the Dirac neutrino and the Majorana neutrino are pointed out and the evidence for different neutrino 'flavours', neutrino mass, and neutrino oscillations is discussed. The second part summarizes current views on cosmology, particularly as they are affected by recent theoretical and experimental advances in high-energy particle physics. Finally, the close relationship between neutrino physics and cosmology is brought out in more detail, to show how cosmological constraints can limit the various theoretical possibilities for neutrinos and, more particularly, how increasing knowledge of neutrino properties can contribute to our understanding of the origin, history, and future of the Universe. The level is that of the beginning graduate student. (orig.)
International Nuclear Information System (INIS)
Khalatnikov, I.M.; Belinskij, V.A.
1984-01-01
Application of the qualitative theory of dynamic systems to analysis of homogeneous cosmological models is described. Together with the well-known cases, requiring ideal liquid, the properties of cosmological evolution of matter with dissipative processes due to viscosity are considered. New cosmological effects occur, when viscosity terms being one and the same order with the rest terms in the equations of gravitation or even exceeding them. In these cases the description of the dissipative process by means of only two viscosity coefficients (volume and shift) may become inapplicable because all the rest decomposition terms of dissipative addition to the energy-momentum in velocity gradient can be large application of equations with hydrodynamic viscosty should be considered as a model of dissipative effects in cosmology
Lesgourgues, Julien; Miele, Gennaro; Pastor, Sergio
2013-01-01
The role that neutrinos have played in the evolution of the Universe is the focus of one of the most fascinating research areas that has stemmed from the interplay between cosmology, astrophysics and particle physics. In this self-contained book, the authors bring together all aspects of the role of neutrinos in cosmology, spanning from leptogenesis to primordial nucleosynthesis, their role in CMB and structure formation, to the problem of their direct detection. The book starts by guiding the reader through aspects of fundamental neutrino physics, such as the standard cosmological model and the statistical mechanics in the expanding Universe, before discussing the history of neutrinos in chronological order from the very early stages until today. This timely book will interest graduate students and researchers in astrophysics, cosmology and particle physics, who work with either a theoretical or experimental focus.
International Nuclear Information System (INIS)
Zeldovich, Y.B.
1983-01-01
This paper fives a general review of modern cosmology. The following subjects are discussed: hot big bang and periodization of the evolution; Hubble expansion; the structure of the universe (pancake theory); baryon asymmetry; inflatory universe. (Auth.)
Energy Technology Data Exchange (ETDEWEB)
Zhang Yuanzhong
2002-06-21
This book is one of a series in the areas of high-energy physics, cosmology and gravitation published by the Institute of Physics. It includes courses given at a doctoral school on 'Relativistic Cosmology: Theory and Observation' held in Spring 2000 at the Centre for Scientific Culture 'Alessandro Volta', Italy, sponsored by SIGRAV-Societa Italiana di Relativita e Gravitazione (Italian Society of Relativity and Gravitation) and the University of Insubria. This book collects 15 review reports given by a number of outstanding scientists. They touch upon the main aspects of modern cosmology from observational matters to theoretical models, such as cosmological models, the early universe, dark matter and dark energy, modern observational cosmology, cosmic microwave background, gravitational lensing, and numerical simulations in cosmology. In particular, the introduction to the basics of cosmology includes the basic equations, covariant and tetrad descriptions, Friedmann models, observation and horizons, etc. The chapters on the early universe involve inflationary theories, particle physics in the early universe, and the creation of matter in the universe. The chapters on dark matter (DM) deal with experimental evidence of DM, neutrino oscillations, DM candidates in supersymmetry models and supergravity, structure formation in the universe, dark-matter search with innovative techniques, and dark energy (cosmological constant), etc. The chapters about structure in the universe consist of the basis for structure formation, quantifying large-scale structure, cosmic background fluctuation, galaxy space distribution, and the clustering of galaxies. In the field of modern observational cosmology, galaxy surveys and cluster surveys are given. The chapter on gravitational lensing describes the lens basics and models, galactic microlensing and galaxy clusters as lenses. The last chapter, 'Numerical simulations in cosmology', deals with spatial and
International Nuclear Information System (INIS)
Zeldovich, Ya.
1984-01-01
The knowledge is summed up of contemporary cosmology on the universe and its development resulting from a great number of highly sensitive observations and the application of contemporary physical theories to the entire universe. The questions are assessed of mass density in the universe, the structure and origin of the universe, its baryon asymmetry and the quantum explanation of the origin of the universe. Physical problems are presented which should be resolved for the future development of cosmology. (Ha)
CERN. Geneva
2007-01-01
The understanding of the Universe at the largest and smallest scales traditionally has been the subject of cosmology and particle physics, respectively. Studying the evolution of the Universe connects today's large scales with the tiny scales in the very early Universe and provides the link between the physics of particles and of the cosmos. This series of five lectures aims at a modern and critical presentation of the basic ideas, methods, models and observations in today's particle cosmology.
Energy Technology Data Exchange (ETDEWEB)
Sefusatti, Emiliano; /Fermilab /CCPP, New York; Crocce, Martin; Pueblas, Sebastian; Scoccimarro, Roman; /CCPP, New York
2006-04-01
The present spatial distribution of galaxies in the Universe is non-Gaussian, with 40% skewness in 50 h{sup -1} Mpc spheres, and remarkably little is known about the information encoded in it about cosmological parameters beyond the power spectrum. In this work they present an attempt to bridge this gap by studying the bispectrum, paying particular attention to a joint analysis with the power spectrum and their combination with CMB data. They address the covariance properties of the power spectrum and bispectrum including the effects of beat coupling that lead to interesting cross-correlations, and discuss how baryon acoustic oscillations break degeneracies. They show that the bispectrum has significant information on cosmological parameters well beyond its power in constraining galaxy bias, and when combined with the power spectrum is more complementary than combining power spectra of different samples of galaxies, since non-Gaussianity provides a somewhat different direction in parameter space. In the framework of flat cosmological models they show that most of the improvement of adding bispectrum information corresponds to parameters related to the amplitude and effective spectral index of perturbations, which can be improved by almost a factor of two. Moreover, they demonstrate that the expected statistical uncertainties in {sigma}s of a few percent are robust to relaxing the dark energy beyond a cosmological constant.
Joudaki, Shahab; Blake, Chris; Johnson, Andrew; Amon, Alexandra; Asgari, Marika; Choi, Ami; Erben, Thomas; Glazebrook, Karl; Harnois-Déraps, Joachim; Heymans, Catherine; Hildebrandt, Hendrik; Hoekstra, Henk; Klaes, Dominik; Kuijken, Konrad; Lidman, Chris; Mead, Alexander; Miller, Lance; Parkinson, David; Poole, Gregory B.; Schneider, Peter; Viola, Massimo; Wolf, Christian
2018-03-01
We perform a combined analysis of cosmic shear tomography, galaxy-galaxy lensing tomography, and redshift-space multipole power spectra (monopole and quadrupole) using 450 deg2 of imaging data by the Kilo Degree Survey (KiDS-450) overlapping with two spectroscopic surveys: the 2-degree Field Lensing Survey (2dFLenS) and the Baryon Oscillation Spectroscopic Survey (BOSS). We restrict the galaxy-galaxy lensing and multipole power spectrum measurements to the overlapping regions with KiDS, and self-consistently compute the full covariance between the different observables using a large suite of N-body simulations. We methodically analyse different combinations of the observables, finding that the galaxy-galaxy lensing measurements are particularly useful in improving the constraint on the intrinsic alignment amplitude, while the multipole power spectra are useful in tightening the constraints along the lensing degeneracy direction. The fully combined constraint on S_8 ≡ σ _8 √{Ω _m/0.3}=0.742± 0.035, which is an improvement by 20 per cent compared to KiDS alone, corresponds to a 2.6σ discordance with Planck, and is not significantly affected by fitting to a more conservative set of scales. Given the tightening of the parameter space, we are unable to resolve the discordance with an extended cosmology that is simultaneously favoured in a model selection sense, including the sum of neutrino masses, curvature, evolving dark energy and modified gravity. The complementarity of our observables allows for constraints on modified gravity degrees of freedom that are not simultaneously bounded with either probe alone, and up to a factor of three improvement in the S8 constraint in the extended cosmology compared to KiDS alone.
Inflationary cosmology from quantum conformal gravity
International Nuclear Information System (INIS)
Jizba, Petr; Kleinert, Hagen; Scardigli, Fabio
2015-01-01
We analyze the functional integral for quantum conformal gravity and show that, with the help of a Hubbard-Stratonovich transformation, the action can be broken into a local quadratic-curvature theory coupled to a scalar field. A one-loop effective-action calculation reveals that strong fluctuations of the metric field are capable of spontaneously generating a dimensionally transmuted parameter which, in the weak-field sector of the broken phase, induces a Starobinsky-type f(R)-model with a gravi-cosmological constant. A resulting non-trivial relation between Starobinsky's parameter and the gravi-cosmological constant is highlighted and implications for cosmic inflation are briefly discussed and compared with the recent PLANCK and BICEP2 data. (orig.)
Exploring Cosmology with Supernovae
DEFF Research Database (Denmark)
Li, Xue
distribution of strong gravitational lensing is developed. For Type Ia supernova (SNe Ia), the rate is lower than core-collapse supernovae (CC SNe). The rate of SNe Ia declines beyond z 1:5. Based on these reasons, we investigate a potential candidate to measure cosmological distance: GRB......-SNe. They are a subclass of CC SNe. Light curves of GRB-SNe are obtained and their properties are studied. We ascertain that the properties of GRB-SNe make them another candidate for standardizable candles in measuring the cosmic distance. Cosmological parameters M and are constrained with the help of GRB-SNe. The first...
International Nuclear Information System (INIS)
Novello, M.; Salim, J.M.; Torres, J.; Oliveira, H.P. de
1989-01-01
A set of spatially homogeneous and isotropic cosmological geometries generated by a class of non-perfect is investigated fluids. The irreversibility if this system is studied in the context of causal thermodynamics which provides a useful mechanism to conform to the non-violation of the causal principle. (author) [pt
Modified geodetic brane cosmology
International Nuclear Information System (INIS)
Cordero, Rubén; Cruz, Miguel; Molgado, Alberto; Rojas, Efraín
2012-01-01
We explore the cosmological implications provided by the geodetic brane gravity action corrected by an extrinsic curvature brane term, describing a codimension-1 brane embedded in a 5D fixed Minkowski spacetime. In the geodetic brane gravity action, we accommodate the correction term through a linear term in the extrinsic curvature swept out by the brane. We study the resulting geodetic-type equation of motion. Within a Friedmann–Robertson–Walker metric, we obtain a generalized Friedmann equation describing the associated cosmological evolution. We observe that, when the radiation-like energy contribution from the extra dimension is vanishing, this effective model leads to a self-(non-self)-accelerated expansion of the brane-like universe in dependence on the nature of the concomitant parameter β associated with the correction, which resembles an analogous behaviour in the DGP brane cosmology. Several possibilities in the description for the cosmic evolution of this model are embodied and characterized by the involved density parameters related in turn to the cosmological constant, the geometry characterizing the model, the introduced β parameter as well as the dark-like energy and the matter content on the brane. (paper)
International Nuclear Information System (INIS)
Schramm, D.N.; Fields, B.; Thomas, D.
1992-01-01
The possible implications of the quark-hadron transition for cosmology are explored. Possible surviving signatures are discussed. In particular, the possibility of generating a dark matter candidate such as strange nuggets or planetary mass black holes is noted. Much discussion is devoted to the possible role of the transition for cosmological nucleosynthesis. It is emphasized that even an optimized first order phase transition will not significantly alter the nucleosynthesis constraints on the cosmological baryon density nor on neutrino counting. However, it is noted that Be and B observations in old stars may eventually be able to be a signature of a cosmologically significant quark-hadron transition. It is pointed out that the critical point in this regard is whether the observed B/Be ratio can be produced by spallation processes or requires cosmological input. Spallation cannot produce a B/Be ratio below 7.6. A supporting signature would be Be and B ratios to oxygen that greatly exceed galactic values. At present, all data is still consistent with a spallagenic origin
Rajantie, Arttu
2018-03-06
The discovery of the Higgs boson in 2012 and other results from the Large Hadron Collider have confirmed the standard model of particle physics as the correct theory of elementary particles and their interactions up to energies of several TeV. Remarkably, the theory may even remain valid all the way to the Planck scale of quantum gravity, and therefore it provides a solid theoretical basis for describing the early Universe. Furthermore, the Higgs field itself has unique properties that may have allowed it to play a central role in the evolution of the Universe, from inflation to cosmological phase transitions and the origin of both baryonic and dark matter, and possibly to determine its ultimate fate through the electroweak vacuum instability. These connections between particle physics and cosmology have given rise to a new and growing field of Higgs cosmology, which promises to shed new light on some of the most puzzling questions about the Universe as new data from particle physics experiments and cosmological observations become available.This article is part of the Theo Murphy meeting issue 'Higgs cosmology'. © 2018 The Author(s).
Rajantie, Arttu
2018-01-01
The discovery of the Higgs boson in 2012 and other results from the Large Hadron Collider have confirmed the standard model of particle physics as the correct theory of elementary particles and their interactions up to energies of several TeV. Remarkably, the theory may even remain valid all the way to the Planck scale of quantum gravity, and therefore it provides a solid theoretical basis for describing the early Universe. Furthermore, the Higgs field itself has unique properties that may have allowed it to play a central role in the evolution of the Universe, from inflation to cosmological phase transitions and the origin of both baryonic and dark matter, and possibly to determine its ultimate fate through the electroweak vacuum instability. These connections between particle physics and cosmology have given rise to a new and growing field of Higgs cosmology, which promises to shed new light on some of the most puzzling questions about the Universe as new data from particle physics experiments and cosmological observations become available. This article is part of the Theo Murphy meeting issue `Higgs cosmology'.
DEFF Research Database (Denmark)
Aghanim, N.; Akrami, Y.; Ashdown, M.
2017-01-01
The six parameters of the standard ΛCDM model have best-fit values derived from the Planck temperature power spectrum that are shifted somewhat from the best-fit values derived from WMAP data. These shifts are driven by features in the Planck temperature power spectrum at angular scales that had ...
Sanders, Robert H
2016-01-01
The advent of sensitive high-resolution observations of the cosmic microwave background radiation and their successful interpretation in terms of the standard cosmological model has led to great confidence in this model's reality. The prevailing attitude is that we now understand the Universe and need only work out the details. In this book, Sanders traces the development and successes of Lambda-CDM, and argues that this triumphalism may be premature. The model's two major components, dark energy and dark matter, have the character of the pre-twentieth-century luminiferous aether. While there is astronomical evidence for these hypothetical fluids, their enigmatic properties call into question our assumptions of the universality of locally determined physical law. Sanders explains how modified Newtonian dynamics (MOND) is a significant challenge for cold dark matter. Overall, the message is hopeful: the field of cosmology has not become frozen, and there is much fundamental work ahead for tomorrow's cosmologis...
International Nuclear Information System (INIS)
Dickau, Jonathan J.
2009-01-01
The use of fractals and fractal-like forms to describe or model the universe has had a long and varied history, which begins long before the word fractal was actually coined. Since the introduction of mathematical rigor to the subject of fractals, by Mandelbrot and others, there have been numerous cosmological theories and analyses of astronomical observations which suggest that the universe exhibits fractality or is by nature fractal. In recent years, the term fractal cosmology has come into usage, as a description for those theories and methods of analysis whereby a fractal nature of the cosmos is shown.
Cao, Shu-Lei; Duan, Xiao-Wei; Meng, Xiao-Lei; Zhang, Tong-Jie
2018-04-01
Aiming at exploring the nature of dark energy (DE), we use forty-three observational Hubble parameter data (OHD) in the redshift range 0 measurements. The binning methods turn out to be promising and considered to be robust. By applying the two-point diagnostic to the binned data, we find that although the best-fit values of Omh^2 fluctuate as the continuous redshift intervals change, on average, they are continuous with being constant within 1 σ confidence interval. Therefore, we conclude that the ΛCDM model cannot be ruled out.
Cold-Crucible Design Parameters for Next Generation HLW Melters
International Nuclear Information System (INIS)
Gombert, D.; Richardson, J.; Aloy, A.; Day, D.
2002-01-01
The cold-crucible induction melter (CCIM) design eliminates many materials and operating constraints inherent in joule-heated melter (JHM) technology, which is the standard for vitrification of high-activity wastes worldwide. The cold-crucible design is smaller, less expensive, and generates much less waste for ultimate disposal. It should also allow a much more flexible operating envelope, which will be crucial if the heterogeneous wastes at the DOE reprocessing sites are to be vitrified. A joule-heated melter operates by passing current between water-cooled electrodes through a molten pool in a refractory-lined chamber. This design is inherently limited by susceptibility of materials to corrosion and melting. In addition, redox conditions and free metal content have exacerbated materials problems or lead to electrical short-circuiting causing failures in DOE melters. In contrast, the CCIM design is based on inductive coupling of a water-cooled high-frequency electrical coil with the glass, causing eddycurrents that produce heat and mixing. A critical difference is that inductance coupling transfers energy through a nonconductive solid layer of slag coating the metal container inside the coil, whereas the jouleheated design relies on passing current through conductive molten glass in direct contact with the metal electrodes and ceramic refractories. The frozen slag in the CCIM design protects the containment and eliminates the need for refractory, while the corrosive molten glass can be the limiting factor in the JH melter design. The CCIM design also eliminates the need for electrodes that typically limit operating temperature to below 1200 degrees C. While significant marketing claims have been made by French and Russian technology suppliers and developers, little data is available for engineering and economic evaluation of the technology, and no facilities are available in the US to support testing. A currently funded project at the Idaho National Engineering
Generation of deviation parameters for amino acid singlets, doublets ...
Indian Academy of Sciences (India)
We present a new method, secondary structure prediction by deviation parameter (SSPDP) for predicting the secondary structure of proteins from amino acid sequence. Deviation parameters (DP) for amino acid singlets, doublets and triplets were computed with respect to secondary structural elements of proteins based on ...
Ellis, G F R
1993-01-01
Many topics were covered in the submitted papers, showing much life in this subject at present. They ranged from conventional calculations in specific cosmological models to provocatively speculative work. Space and time restrictions required selecting from them, for summarisation here; the book of Abstracts should be consulted for a full overview.
International Nuclear Information System (INIS)
Chow, Nathan; Khoury, Justin
2009-01-01
We study the cosmology of a galileon scalar-tensor theory, obtained by covariantizing the decoupling Lagrangian of the Dvali-Gabadadze-Poratti (DGP) model. Despite being local in 3+1 dimensions, the resulting cosmological evolution is remarkably similar to that of the full 4+1-dimensional DGP framework, both for the expansion history and the evolution of density perturbations. As in the DGP model, the covariant galileon theory yields two branches of solutions, depending on the sign of the galileon velocity. Perturbations are stable on one branch and ghostlike on the other. An interesting effect uncovered in our analysis is a cosmological version of the Vainshtein screening mechanism: at early times, the galileon dynamics are dominated by self-interaction terms, resulting in its energy density being suppressed compared to matter or radiation; once the matter density has redshifted sufficiently, the galileon becomes an important component of the energy density and contributes to dark energy. We estimate conservatively that the resulting expansion history is consistent with the observed late-time cosmology, provided that the scale of modification satisfies r c > or approx. 15 Gpc.
DEFF Research Database (Denmark)
Aghanim, N.; Akrami, Y.; Ashdown, M.
2017-01-01
never before been measured to cosmic-variance level precision. We have investigated these shifts to determine whether they are within the range of expectation and to understand their origin in the data. Taking our parameter set to be the optical depth of the reionized intergalactic medium τ, the baryon...... density ωb, the matter density ωm, the angular size of the sound horizon θ∗, the spectral index of the primordial power spectrum, ns, and Ase- 2τ (where As is the amplitude of the primordial power spectrum), we have examined the change in best-fit values between a WMAP-like large angular-scale data set...
Dynamics of 'abc' and 'qd' constant parameters induction generator model
DEFF Research Database (Denmark)
Fajardo-R, L.A.; Medina, A.; Iov, F.
2009-01-01
In this paper, parametric sensibility effects on dynamics of the induction generator in the presence of local perturbations are investigated. The study is conducted in a 3x2 MW wind park dealing with abc, qd0 and qd reduced order, induction generator model respectively, and with fluxes as state...
International Nuclear Information System (INIS)
Amendola, Luca; Campos, Gabriela Camargo; Rosenfeld, Rogerio
2007-01-01
Models where the dark matter component of the Universe interacts with the dark energy field have been proposed as a solution to the cosmic coincidence problem, since in the attractor regime both dark energy and dark matter scale in the same way. In these models the mass of the cold dark matter particles is a function of the dark energy field responsible for the present acceleration of the Universe, and different scenarios can be parametrized by how the mass of the cold dark matter particles evolves with time. In this article we study the impact of a constant coupling δ between dark energy and dark matter on the determination of a redshift dependent dark energy equation of state w DE (z) and on the dark matter density today from SNIa data. We derive an analytical expression for the luminosity distance in this case. In particular, we show that the presence of such a coupling increases the tension between the cosmic microwave background data from the analysis of the shift parameter in models with constant w DE and SNIa data for realistic values of the present dark matter density fraction. Thus, an independent measurement of the present dark matter density can place constraints on models with interacting dark energy
Cosmology and the weak interaction
Energy Technology Data Exchange (ETDEWEB)
Schramm, D.N. (Fermi National Accelerator Lab., Batavia, IL (USA)):(Chicago Univ., IL (USA))
1989-12-01
The weak interaction plays a critical role in modern Big Bang cosmology. This review will emphasize two of its most publicized cosmological connections: Big Bang nucleosynthesis and Dark Matter. The first of these is connected to the cosmological prediction of Neutrino Flavours, N{sub {nu}} {approximately} 3 which is now being confirmed at SLC and LEP. The second is interrelated to the whole problem of galaxy and structure formation in the universe. This review will demonstrate the role of the weak interaction both for dark matter candidates and for the problem of generating seeds to form structure. 87 refs., 3 figs., 5 tabs.
Cosmology and the weak interaction
International Nuclear Information System (INIS)
Schramm, D.N.
1989-12-01
The weak interaction plays a critical role in modern Big Bang cosmology. This review will emphasize two of its most publicized cosmological connections: Big Bang nucleosynthesis and Dark Matter. The first of these is connected to the cosmological prediction of Neutrino Flavours, N ν ∼ 3 which is now being confirmed at SLC and LEP. The second is interrelated to the whole problem of galaxy and structure formation in the universe. This review will demonstrate the role of the weak interaction both for dark matter candidates and for the problem of generating seeds to form structure. 87 refs., 3 figs., 5 tabs
Graviton fluctuations erase the cosmological constant
Wetterich, C.
2017-10-01
Graviton fluctuations induce strong non-perturbative infrared renormalization effects for the cosmological constant. The functional renormalization flow drives a positive cosmological constant towards zero, solving the cosmological constant problem without the need to tune parameters. We propose a simple computation of the graviton contribution to the flow of the effective potential for scalar fields. Within variable gravity, with effective Planck mass proportional to the scalar field, we find that the potential increases asymptotically at most quadratically with the scalar field. The solutions of the derived cosmological equations lead to an asymptotically vanishing cosmological "constant" in the infinite future, providing for dynamical dark energy in the present cosmological epoch. Beyond a solution of the cosmological constant problem, our simplified computation also entails a sizeable positive graviton-induced anomalous dimension for the quartic Higgs coupling in the ultraviolet regime, substantiating the successful prediction of the Higgs boson mass within the asymptotic safety scenario for quantum gravity.
Roberts, Alex
2016-08-01
Recently, a new framework for describing the multiverse has been proposed which is based on the principles of quantum mechanics. The framework allows for well-defined predictions, both regarding global properties of the universe and outcomes of particular experiments, according to a single probability formula. This provides complete unification of the eternally inflating multiverse and many worlds in quantum mechanics. We elucidate how cosmological parameters can be calculated in this framework, and study the probability distribution for the value of the cosmological constant. We consider both positive and negative values, and find that the observed value is consistent with the calculated distribution at an order of magnitude level. In particular, in contrast to the case of earlier measure proposals, our framework prefers a positive cosmological constant over a negative one. These results depend only moderately on how we model galaxy formation and life evolution therein. We explore supersymmetric theories in which the Higgs mass is boosted by the non-decoupling D-terms of an extended U(1) X gauge symmetry, defined here to be a general linear combination of hypercharge, baryon number, and lepton number. Crucially, the gauge coupling, gX, is bounded from below to accommodate the Higgs mass, while the quarks and leptons are required by gauge invariance to carry non-zero charge under U(1)X. This induces an irreducible rate, sigmaBR, for pp → X → ll relevant to existing and future resonance searches, and gives rise to higher dimension operators that are stringently constrained by precision electroweak measurements. Combined, these bounds define a maximally allowed region in the space of observables, (sigmaBR, mX), outside of which is excluded by naturalness and experimental limits. If natural supersymmetry utilizes non-decoupling D-terms, then the associated X boson can only be observed within this window, providing a model independent 'litmus test' for this broad
Ekpyrotic and cyclic cosmology
International Nuclear Information System (INIS)
Lehners, Jean-Luc
2008-01-01
Ekpyrotic and cyclic cosmologies provide theories of the very early and of the very late universe. In these models, the big bang is described as a collision of branes - and thus the big bang is not the beginning of time. Before the big bang, there is an ekpyrotic phase with equation of state w=P/(ρ) >>1 (where P is the average pressure and ρ the average energy density) during which the universe slowly contracts. This phase resolves the standard cosmological puzzles and generates a nearly scale-invariant spectrum of cosmological perturbations containing a significant non-Gaussian component. At the same time it produces small-amplitude gravitational waves with a blue spectrum. The dark energy dominating the present-day cosmological evolution is reinterpreted as a small attractive force between our brane and a parallel one. This force eventually induces a new ekpyrotic phase and a new brane collision, leading to the idea of a cyclic universe. This review discusses the detailed properties of these models, their embedding in M-theory and their viability, with an emphasis on open issues and observational signatures
Magnetogenesis in matter—Ekpyrotic bouncing cosmology
Energy Technology Data Exchange (ETDEWEB)
Koley, Ratna; Samtani, Sidhartha, E-mail: ratna.physics@presiuniv.ac.in, E-mail: samtanisidhartha@gmail.com [Department of Physics, Presidency University, 86/1 College Street, Kolkata, 700073 (India)
2017-04-01
In the recent past there have been many attempts to associate the generation of primordial magnetic seed fields with the inflationary era, but with limited success. We thus take a different approach by using a model for nonsingular bouncing cosmology. A coupling of the electromagnetic Lagrangian F {sub μν} F {sup μν} with a non background scalar field has been considered for the breaking of conformal invariance. We have shown that non singular bouncing cosmology supports magnetogenesis evading the long standing back reaction and strong coupling problems which have plagued inflationary magnetogenesis. In this model, we have achieved a scale invariant power spectrum for the parameter range compatible with observed CMB anisotropies. The desired strength of the magnetic field has also been obtained that goes in accordance with present observations. It is also important to note that no BKL instability arises within this parameter range. The energy scales for different stages of evolution of the bouncing model are so chosen that they solve certain problems of standard Big Bang cosmology as well.
International Nuclear Information System (INIS)
Fliche, H.-H.; Souriau, J.-M.
1978-03-01
On the basis of colorimetric data a composite spectrum of quasars is established from the visible to the Lyman's limit. Its agreement with the spectrum of the quasar 3C273, obtained directly, confirms the homogeneity of these objects. The compatibility of the following hypotheses: negligible evolution of quasars, Friedmann type model of the universe with cosmological constant, is studied by means of two tests: a non-correlation test adopted to the observation conditions and the construction of diagrams (absolute magnitude, volume) using the K-correction deduced from the composite spectrum. This procedure happens to give relatively well-defined values of the parameters; the central values of the density parameter, the reduced curvature and the reduced cosmological constant are: Ω 0 =0.053, k 0 =0.245, lambda-zero=1.19, which correspond to a big bang model, eternally expanding, spatially finite, in which Hubble's parameter H is presently increasing. This model responds well to different cosmological tests: density of matter, diameter of radio sources, age of the universe. Its characteristics suggest various cosmogonic mechanisms, espacially mass formation by growth of empty spherical bubbles [fr
Grant, E.; Murdin, P.
2000-11-01
During the early Middle Ages (ca 500 to ca 1130) scholars with an interest in cosmology had little useful and dependable literature. They relied heavily on a partial Latin translation of PLATO's Timaeus by Chalcidius (4th century AD), and on a series of encyclopedic treatises associated with the names of Pliny the Elder (ca AD 23-79), Seneca (4 BC-AD 65), Macrobius (fl 5th century AD), Martianus ...
iCosmo: an interactive cosmology package
Refregier, A.; Amara, A.; Kitching, T. D.; Rassat, A.
2011-04-01
Aims: The interactive software package iCosmo, designed to perform cosmological calculations is described. Methods: iCosmo is a software package to perfom interactive cosmological calculations for the low-redshift universe. Computing distance measures, the matter power spectrum, and the growth factor is supported for any values of the cosmological parameters. It also computes derived observed quantities for several cosmological probes such as cosmic shear, baryon acoustic oscillations, and type Ia supernovae. The associated errors for these observable quantities can be derived for customised surveys, or for pre-set values corresponding to current or planned instruments. The code also allows for calculation of cosmological forecasts with Fisher matrices, which can be manipulated to combine different surveys and cosmological probes. The code is written in the IDL language and thus benefits from the convenient interactive features and scientific libraries available in this language. iCosmo can also be used as an engine to perform cosmological calculations in batch mode, and forms a convenient adaptive platform for the development of further cosmological modules. With its extensive documentation, it may also serve as a useful resource for teaching and for newcomers to the field of cosmology. Results: The iCosmo package is described with a number of examples and command sequences. The code is freely available with documentation at http://www.icosmo.org, along with an interactive web interface and is part of the Initiative for Cosmology, a common archive for cosmological resources.
Moody Music Generator: Characterising Control Parameters Using Crowdsourcing
DEFF Research Database (Denmark)
Scirea, Marco; Togelius, Julian; Nelson, Mark
2015-01-01
. In this paper we conduct a listener study to determine how people actually perceive the various moods the generator can produce. Rather than directly attempting to validate that our two control param- eters represent arousal and valence, instead we conduct an open-ended study to crowd-source labels...
International Nuclear Information System (INIS)
Partridge, R.B.
1977-01-01
Some sixty years after the development of relativistic cosmology by Einstein and his colleagues, observations are finally beginning to have an important impact on our views of the Universe. The available evidence seems to support one of the simplest cosmological models, the hot Big Bang model. The aim of this paper is to assess the observational support for certain assumptions underlying the hot Big Bang model. These are that the Universe is isobaric and homogeneous on a large scale; that it is expanding from an initial state of high density and temperature; and that the proper theory to describe the dynamics of the Universe is unmodified General Relativity. The properties of the cosmic microwave background radiation and recent observations of the abundance of light elements, in particular, support these assumptions. Also examined here are the data bearing on the related questions of the geometry and the future of the Universe (is it ever-expanding, or fated to recollapse). Finally, some difficulties and faults of the standard model are discussed, particularly various aspects of the 'initial condition' problem. It appears that the simplest Big Bang cosmological model calls for a highly specific set of initial conditions to produce the presently observed properties of the Universe. (Auth.)
the Universe About Cosmology Planck Satellite Launched Cosmology Videos Professor George Smoot's group conducts research on the early universe (cosmology) using the Cosmic Microwave Background radiation (CMB science goals regarding cosmology. George Smoot named Director of Korean Cosmology Institute The GRB
Automatic generation of biasing parameters for MORSE shielding problems
International Nuclear Information System (INIS)
Hoogenboom, J.E.
1995-01-01
It would be favourable if the biasing functions could be obtained from the Monte Carlo calculation itself. This is discussed in this paper as well as the way to obtain biasing parameters from it for splitting, Russian roulette and path length stretching. The method is demonstrated for a shielding problem solved with the MORSE-SGC/S Monte Carlo code of the SCALE-system. (K.A.)
International Nuclear Information System (INIS)
ColIn, Pedro; Vazquez-Semadeni, Enrique; Avila-Reese, Vladimir; Valenzuela, Octavio; Ceverino, Daniel
2010-01-01
We present numerical simulations aimed at exploring the effects of varying the sub-grid physics parameters on the evolution and the properties of the galaxy formed in a low-mass dark matter halo (∼7 x 10 10 h -1 M sun at redshift z = 0). The simulations are run within a cosmological setting with a nominal resolution of 218 pc comoving and are stopped at z = 0.43. For simulations that cannot resolve individual molecular clouds, we propose the criterion that the threshold density for star formation, n SF , should be chosen such that the column density of the star-forming cells equals the threshold value for molecule formation, N ∼ 10 21 cm -2 , or ∼8 M sun pc -2 . In all of our simulations, an extended old/intermediate-age stellar halo and a more compact younger stellar disk are formed, and in most cases, the halo's specific angular momentum is slightly larger than that of the galaxy, and sensitive to the SF/feedback parameters. We found that a non-negligible fraction of the halo stars are formed in situ in a spheroidal distribution. Changes in the sub-grid physics parameters affect significantly and in a complex way the evolution and properties of the galaxy: (1) lower threshold densities n SF produce larger stellar effective radii R e , less peaked circular velocity curves V c (R), and greater amounts of low-density and hot gas in the disk mid-plane; (2) when stellar feedback is modeled by temporarily switching off radiative cooling in the star-forming regions, R e increases (by a factor of ∼2 in our particular model), the circular velocity curve becomes flatter, and a complex multi-phase gaseous disk structure develops; (3) a more efficient local conversion of gas mass to stars, measured by a stellar particle mass distribution biased toward larger values, increases the strength of the feedback energy injection-driving outflows and inducing burstier SF histories; (4) if feedback is too strong, gas loss by galactic outflows-which are easier to produce in low
International Nuclear Information System (INIS)
Seljak, Uros; Makarov, Alexey; McDonald, Patrick; Anderson, Scott F.; Bahcall, Neta A.; Cen, Renyue; Gunn, James E.; Lupton, Robert H.; Schlegel, David J.; Brinkmann, J.; Burles, Scott; Doi, Mamoru; Ivezic, Zeljko; Kent, Stephen; Loveday, Jon; Munn, Jeffrey A.; Nichol, Robert C.; Ostriker, Jeremiah P.; Schneider, Donald P.; Berk, Daniel E. Vanden
2005-01-01
We combine the constraints from the recent Lyα forest analysis of the Sloan Digital Sky Survey (SDSS) and the SDSS galaxy bias analysis with previous constraints from SDSS galaxy clustering, the latest supernovae, and 1st year WMAP cosmic microwave background anisotropies. We find significant improvements on all of the cosmological parameters compared to previous constraints, which highlights the importance of combining Lyα forest constraints with other probes. Combining WMAP and the Lyα forest we find for the primordial slope n s =0.98±0.02. We see no evidence of running, dn/dlnk=-0.003±0.010, a factor of 3 improvement over previous constraints. We also find no evidence of tensors, r 2 model is within the 2-sigma contour, V∝φ 4 is outside the 3-sigma contour. For the amplitude we find σ 8 =0.90±0.03 from the Lyα forest and WMAP alone. We find no evidence of neutrino mass: for the case of 3 massive neutrino families with an inflationary prior, eV and the mass of lightest neutrino is m 1 ν λ =0.72±0.02, w(z=0.3)=-0.98 -0.12 +0.10 , the latter changing to w(z=0.3)=-0.92 -0.10 +0.09 if tensors are allowed. We find no evidence for variation of the equation of state with redshift, w(z=1)=-1.03 -0.28 +0.21 . These results rely on the current understanding of the Lyα forest and other probes, which need to be explored further both observationally and theoretically, but extensive tests reveal no evidence of inconsistency among different data sets used here
Time variation of the cosmological redshift in Dicke-Brans-Jordan cosmologies
International Nuclear Information System (INIS)
Ruediger, R.
1982-01-01
In this paper the time variation z of the cosmological redshift z is discussed for Dicke-Brans-Jordan (DBJ) cosmologies. We determine the general z-z relation in the functional form zH -1 0 = F(z; q 0 , sigma 0 ,xi 0 , ω) for small values of z, where all the symbols have their conventional meanings. For certain combinations of cosmological parameters, which are within the present observational limitations, the DBJ terms in the function F can dominate the general relativistic terms. Furthermore, zH -1 0 can be positive in DBJ cosmologies in contrast to general relativistic cosmologies with q 0 >0
Parameterized post-Newtonian cosmology
International Nuclear Information System (INIS)
Sanghai, Viraj A A; Clifton, Timothy
2017-01-01
Einstein’s theory of gravity has been extensively tested on solar system scales, and for isolated astrophysical systems, using the perturbative framework known as the parameterized post-Newtonian (PPN) formalism. This framework is designed for use in the weak-field and slow-motion limit of gravity, and can be used to constrain a large class of metric theories of gravity with data collected from the aforementioned systems. Given the potential of future surveys to probe cosmological scales to high precision, it is a topic of much contemporary interest to construct a similar framework to link Einstein’s theory of gravity and its alternatives to observations on cosmological scales. Our approach to this problem is to adapt and extend the existing PPN formalism for use in cosmology. We derive a set of equations that use the same parameters to consistently model both weak fields and cosmology. This allows us to parameterize a large class of modified theories of gravity and dark energy models on cosmological scales, using just four functions of time. These four functions can be directly linked to the background expansion of the universe, first-order cosmological perturbations, and the weak-field limit of the theory. They also reduce to the standard PPN parameters on solar system scales. We illustrate how dark energy models and scalar-tensor and vector-tensor theories of gravity fit into this framework, which we refer to as ‘parameterized post-Newtonian cosmology’ (PPNC). (paper)
Parameterized post-Newtonian cosmology
Sanghai, Viraj A. A.; Clifton, Timothy
2017-03-01
Einstein’s theory of gravity has been extensively tested on solar system scales, and for isolated astrophysical systems, using the perturbative framework known as the parameterized post-Newtonian (PPN) formalism. This framework is designed for use in the weak-field and slow-motion limit of gravity, and can be used to constrain a large class of metric theories of gravity with data collected from the aforementioned systems. Given the potential of future surveys to probe cosmological scales to high precision, it is a topic of much contemporary interest to construct a similar framework to link Einstein’s theory of gravity and its alternatives to observations on cosmological scales. Our approach to this problem is to adapt and extend the existing PPN formalism for use in cosmology. We derive a set of equations that use the same parameters to consistently model both weak fields and cosmology. This allows us to parameterize a large class of modified theories of gravity and dark energy models on cosmological scales, using just four functions of time. These four functions can be directly linked to the background expansion of the universe, first-order cosmological perturbations, and the weak-field limit of the theory. They also reduce to the standard PPN parameters on solar system scales. We illustrate how dark energy models and scalar-tensor and vector-tensor theories of gravity fit into this framework, which we refer to as ‘parameterized post-Newtonian cosmology’ (PPNC).
Gravitational particle production in braneworld cosmology.
Bambi, C; Urban, F R
2007-11-09
Gravitational particle production in a time variable metric of an expanding universe is efficient only when the Hubble parameter H is not too small in comparison with the particle mass. In standard cosmology, the huge value of the Planck mass M{Pl} makes the mechanism phenomenologically irrelevant. On the other hand, in braneworld cosmology, the expansion rate of the early Universe can be much faster, and many weakly interacting particles can be abundantly created. Cosmological implications are discussed.
Evolution in bouncing quantum cosmology
International Nuclear Information System (INIS)
Mielczarek, Jakub; Piechocki, Włodzimierz
2012-01-01
We present the method of describing an evolution in quantum cosmology in the framework of the reduced phase space quantization of loop cosmology. We apply our method to the flat Friedmann-Robertson-Walker model coupled to a massless scalar field. We identify the physical quantum Hamiltonian that is positive-definite and generates globally a unitary evolution of the considered quantum system. We examine the properties of expectation values of physical observables in the process of the quantum big bounce transition. The dispersion of evolved observables is studied for the Gaussian state. Calculated relative fluctuations enable an examination of the semi-classicality conditions and possible occurrence of the cosmic forgetfulness. Preliminary estimations based on the cosmological data suggest that there was no cosmic amnesia. Presented results are analytical, and numerical computations are only used for the visualization purposes. Our method may be generalized to sophisticated cosmological models including the Bianchi-type universes. (paper)
Brandenberger, Robert H.
2008-01-01
String gas cosmology is a string theory-based approach to early universe cosmology which is based on making use of robust features of string theory such as the existence of new states and new symmetries. A first goal of string gas cosmology is to understand how string theory can effect the earliest moments of cosmology before the effective field theory approach which underlies standard and inflationary cosmology becomes valid. String gas cosmology may also provide an alternative to the curren...
EMS mutant spectra generated by multi-parameter flow cytometry
Energy Technology Data Exchange (ETDEWEB)
Keysar, Stephen B. [Cell and Molecular Biology Graduate Program, Colorado State University, Fort Collins, CO (United States); Fox, Michael H., E-mail: michael.fox@colostate.edu [Cell and Molecular Biology Graduate Program, Colorado State University, Fort Collins, CO (United States); Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO (United States)
2009-12-01
The CHO A{sub L} cell line contains a single copy of human chromosome 11 that encodes several cell surface proteins including glycosyl phosphatidylinositol (GPI) linked CD59 and CD90, as well as CD98, CD44 and CD151 which are not GPI-linked. The flow cytometry mutation assay (FCMA) measures mutations of the CD59 gene by the absence of fluorescence when stained with antibodies against the CD59 cell surface protein. We have measured simultaneous mutations in CD59, CD44, CD90, CD98 and CD151 to generate a mutant spectrum for ionizing radiation. After treatment with ethyl methanesulfonate (EMS) many cells have an intermediate level of CD59 staining. Single cells were sorted from CD59{sup -} regions with varying levels of fluorescence and the resulting clonal populations had a stable phenotype for CD59 expression. Mutant spectra were generated by flow cytometry using the isolated clones and nearly all clones were mutated in CD59 only. Interestingly, about 60% of the CD59 negative clones were actually GPI mutants determined by staining with the GPI specific fluorescently labeled bacterial toxin aerolysin (FLAER). The GPI negative cells are most likely caused by mutations in the X-linked pigA gene important in GPI biosynthesis. Small mutations of pigA and CD59 were expected for the alkylating agent EMS and the resulting spectra are significantly different than the large deletions found when analyzing radiation mutants. After analyzing the CD59{sup -} clonal populations we have adjusted the FCMA mutant regions from 1% to 10% of the mean of the CD59 positive peak to include the majority of CD59 mutants.
Generation of CR mammographic image for evaluation quality parameters
International Nuclear Information System (INIS)
Flores, Mabel B.; Mourao, Arnaldo P.; Centro Federal de Educacao Tecnologica de Minas Gerais
2017-01-01
Currently, among the diseases most feared by women, breast cancer ranks first in the world with an incidence of more than 1.6 million cases and a mortality of more than 521.9 thousand cases by year, which makes this disease the type of cancer with higher incidence and mortality compared to the other types of cancer that mainly affect the female gender, without considering non-melanoma skin cancer. In Brazil, more than 14.4 thousand deaths were registered in 2013 and more than 57 thousand new cases were estimated for 2016. The use of computerized radiography (CR) for the generation of mammographic digital images is widely used in Brazil for the screening of breast cancer. The aim of this investigation is to study the variation of CR plate response to exposure to X-ray beams in a mammography unit. Two CR plates from different manufacturers and a compressed breast phantom containing calcium carbonate structures of different sizes simulating calcifications were used for this study. An X-ray beam generated by 30 kV was selected to realize successive exposures of each plate by performing a time variation of 0.5 to 3.5 s, obtaining the raw images. The acquired images were evaluated with the ImageJ software to determine the saturation time of the plates when exposed to X-ray beams and the qualitative resolution of each plate. The plates were found to saturate at different times when exposed under the same conditions to X-ray beams. By means of the images acquired with the breast phantom, it was possible to observe only structures of calcium carbonate with sizes greater than 177 μm. (author)
Generation of CR mammographic image for evaluation quality parameters
Energy Technology Data Exchange (ETDEWEB)
Flores, Mabel B.; Mourao, Arnaldo P., E-mail: mbustos@ufmg.br, E-mail: apratabhz@gmail.com [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Engenharia Nuclear; Centro Federal de Educacao Tecnologica de Minas Gerais (CEFET-MG), Belo Horizonte, MG (Brazil). Centro de Engenharia Politecnica
2017-11-01
Currently, among the diseases most feared by women, breast cancer ranks first in the world with an incidence of more than 1.6 million cases and a mortality of more than 521.9 thousand cases by year, which makes this disease the type of cancer with higher incidence and mortality compared to the other types of cancer that mainly affect the female gender, without considering non-melanoma skin cancer. In Brazil, more than 14.4 thousand deaths were registered in 2013 and more than 57 thousand new cases were estimated for 2016. The use of computerized radiography (CR) for the generation of mammographic digital images is widely used in Brazil for the screening of breast cancer. The aim of this investigation is to study the variation of CR plate response to exposure to X-ray beams in a mammography unit. Two CR plates from different manufacturers and a compressed breast phantom containing calcium carbonate structures of different sizes simulating calcifications were used for this study. An X-ray beam generated by 30 kV was selected to realize successive exposures of each plate by performing a time variation of 0.5 to 3.5 s, obtaining the raw images. The acquired images were evaluated with the ImageJ software to determine the saturation time of the plates when exposed to X-ray beams and the qualitative resolution of each plate. The plates were found to saturate at different times when exposed under the same conditions to X-ray beams. By means of the images acquired with the breast phantom, it was possible to observe only structures of calcium carbonate with sizes greater than 177 μm. (author)
Quintessential brane cosmology
International Nuclear Information System (INIS)
Kunze, K.E.; Vazquez-Mozo, M.A.
2002-01-01
We study a class of braneworlds where the cosmological evolution arises as the result of the movement of a three-brane in a five-dimensional static dilatonic bulk, with and without reflection symmetry. The resulting four-dimensional Friedmann equation includes a term which, for a certain range of the parameters, effectively works as a quintessence component, producing an acceleration of the universe at late times. Using current observations and bounds derived from big-bang nucleosynthesis, we estimate the parameters that characterize the model
Magnetohydrodynamic cosmologies
International Nuclear Information System (INIS)
Portugal, R.; Soares, I.D.
1991-01-01
We analyse a class of cosmological models in magnetohydrodynamic regime extending and completing the results of a previous paper. The material content of the models is a perfect fluid plus electromagnetic fields. The fluid is neutral in average but admits an electrical current which satisfies Ohm's law. All models fulfil the physical requirements of near equilibrium thermodynamics and can be favourably used as a more realistic description of the interior of a collapsing star in a magnetohydrodynamic regime with or without a magnetic field. (author)
Bardeen, J. M.
The last several years have seen a tremendous ferment of activity in astrophysical cosmology. Much of the theoretical impetus has come from particle physics theories of the early universe and candidates for dark matter, but what promise to be even more significant are improved direct observations of high z galaxies and intergalactic matter, deeper and more comprehensive redshift surveys, and the increasing power of computer simulations of the dynamical evolution of large scale structure. Upper limits on the anisotropy of the microwave background radiation are gradually getting tighter and constraining more severely theoretical scenarios for the evolution of the universe.
International Nuclear Information System (INIS)
Bardeen, J.M.
1986-01-01
The last several years have seen a tremendous ferment of activity in astrophysical cosmology. Much of the theoretical impetus has come from particle physics theories of the early universe and candidates for dark matter, but what promise to be even more significant are improved direct observations of high z galaxies and intergalactic matter, deeper and more comprehensive redshift surveys, and the increasing power of computer simulations of the dynamical evolution of large scale structure. Upper limits on the anisotropy of the microwave background radiation are gradually getting tighter and constraining more severely theoretical scenarios for the evolution of the universe. 47 refs
Boeyens, Jan CA
2010-01-01
The composition of the most remote objects brought into view by the Hubble telescope can no longer be reconciled with the nucleogenesis of standard cosmology and the alternative explanation, in terms of the LAMBDA-Cold-Dark-Matter model, has no recognizable chemical basis. A more rational scheme, based on the chemistry and periodicity of atomic matter, opens up an exciting new interpretation of the cosmos in terms of projective geometry and general relativity. The response of atomic structure to environmental pressure predicts non-Doppler cosmical redshifts and equilibrium nucleogenesis by alp
Page, Don N.
2006-01-01
A complete model of the universe needs at least three parts: (1) a complete set of physical variables and dynamical laws for them, (2) the correct solution of the dynamical laws, and (3) the connection with conscious experience. In quantum cosmology, item (2) is the quantum state of the cosmos. Hartle and Hawking have made the `no-boundary' proposal, that the wavefunction of the universe is given by a path integral over all compact Euclidean 4-dimensional geometries and matter fields that hav...
Religion, theology and cosmology
Directory of Open Access Journals (Sweden)
John T. Fitzgerald
2013-10-01
Full Text Available Cosmology is one of the predominant research areas of the contemporary world. Advances in modern cosmology have prompted renewed interest in the intersections between religion, theology and cosmology. This article, which is intended as a brief introduction to the series of studies on theological cosmology in this journal, identifies three general areas of theological interest stemming from the modern scientific study of cosmology: contemporary theology and ethics; cosmology and world religions; and ancient cosmologies. These intersections raise important questions about the relationship of religion and cosmology, which has recently been addressed by William Scott Green and is the focus of the final portion of the article.
Supersymmetric GUTs and cosmology
International Nuclear Information System (INIS)
Lazarides, G.; Shafi, Q.
1982-06-01
By examining the behaviour of supersymmetric GUTs in the very early universe we find two classes of realistic models. In one of them supersymmetry is broken at or near the superheavy GUT scale. The cosmological implications of such models are expected to be similar to those of nonsupersymmetric GUTs. In the second class of models, the superheavy GUT scale is related to the supersymmetry breaking scale a la Witten. Two types of cosmological scenarios appear possible in this case, either with or without an intermediate (new) inflationary phase. They can be experimentally distinguished, since the former predicts an absence and the latter an observable number density of superheavy monopoles. A mechanism for generating baryon asymmetry in such models is pointed out. Further constraint on model building appears if global R invariance is employed to resolve the strong CP problem. (author)
Zhao, Wen; Wen, Linqing
2018-03-01
We use the Fisher information matrix to investigate the angular resolution and luminosity distance uncertainty for coalescing binary neutron stars (BNSs) and neutron star-black hole binaries (NSBHs) detected by the third-generation (3G) gravitational-wave (GW) detectors. Our study focuses on an individual 3G detector and a network of up to four 3G detectors at different locations including the United States, Europe, China, and Australia for the proposed Einstein Telescope (ET) and Cosmic Explorer (CE) detectors. In particular, we examine the effect of the Earth's rotation, as GW signals from BNS and low-mass NSBH systems could be hours long for 3G detectors. In this case, an individual detector can be effectively treated as a detector network with long baselines formed by the trajectory of the detector as it rotates with the Earth. Therefore, a single detector or two-detector networks could also be used to localize the GW sources effectively. We find that a time-dependent antenna beam-pattern function can help better localize BNS and NSBH sources, especially edge-on ones. The medium angular resolution for one ET-D detector is around 150 deg2 for BNSs at a redshift of z =0.1 , which improves rapidly with a decreasing low-frequency cutoff flow in sensitivity. The medium angular resolution for a network of two CE detectors in the United States and Europe, respectively, is around 20 deg2 at z =0.2 for the simulated BNS and NSBH samples. While for a network of two ET-D detectors, the similar angular resolution can be achieved at a much higher redshift of z =0.5 . The angular resolution of a network of three detectors is mainly determined by the baselines between detectors regardless of the CE or ET detector type. The medium angular resolution of BNS for a network of three detectors of the ET-D or CE type in the United States, Europe, and Australia is around 10 deg2 at z =2 . We discuss the implications of our results for multimessenger astronomy and, in particular, for
International Nuclear Information System (INIS)
Chimento, L P; Forte, M; Devecchi, F P; Kremer, G M; Ribas, M O; Samojeden, L L
2011-01-01
In this work we review if fermionic sources could be responsible for accelerated periods during the evolution of a FRW universe. In a first attempt, besides the fermionic source, a matter constituent would answer for the decelerated periods. The coupled differential equations that emerge from the field equations are integrated numerically. The self-interaction potential of the fermionic field is considered as a function of the scalar and pseudo-scalar invariants. It is shown that the fermionic field could behave like an inflaton field in the early universe, giving place to a transition to a matter dominated (decelerated) period. In a second formulation we turn our attention to analytical results, specifically using the idea of form-invariance transformations. These transformations can be used for obtaining accelerated cosmologies starting with conventional cosmological models. Here we reconsider the scalar field case and extend the discussion to fermionic fields. Finally we investigate the role of a Dirac field in a Brans-Dicke (BD) context. The results show that this source, in combination with the BD scalar, promote a final eternal accelerated era, after a matter dominated period.
Weak lensing cosmology beyond ΛCDM
International Nuclear Information System (INIS)
Das, Sudeep; Linder, Eric V.; Nakajima, Reiko; Putter, Roland de
2012-01-01
Weak gravitational lensing is one of the key probes of the cosmological model, dark energy, and dark matter, providing insight into both the cosmic expansion history and large scale structure growth history. Taking into account a broad spectrum of physics affecting growth — dynamical dark energy, extended gravity, neutrino masses, and spatial curvature — we analyze the cosmological constraints. Similarly we consider the effects of a range of systematic uncertainties, in shear measurement, photometric redshifts, intrinsic alignments, and the nonlinear power spectrum, on cosmological parameter extraction. We also investigate, and provide fitting formulas for, the influence of survey parameters such as redshift depth, galaxy number densities, and sky area on the cosmological constraints in the beyond-ΛCDM parameter space. Finally, we examine the robustness of results for different fiducial cosmologies
Brane cosmology with curvature corrections
International Nuclear Information System (INIS)
Kofinas, Georgios; Maartens, Roy; Papantonopoulos, Eleftherios
2003-01-01
We study the cosmology of the Randall-Sundrum brane-world where the Einstein-Hilbert action is modified by curvature correction terms: a four-dimensional scalar curvature from induced gravity on the brane, and a five-dimensional Gauss-Bonnet curvature term. The combined effect of these curvature corrections to the action removes the infinite-density big bang singularity, although the curvature can still diverge for some parameter values. A radiation brane undergoes accelerated expansion near the minimal scale factor, for a range of parameters. This acceleration is driven by the geometric effects, without an inflation field or negative pressures. At late times, conventional cosmology is recovered. (author)
Cosmology of a charged universe
International Nuclear Information System (INIS)
Barnes, A.
1979-01-01
The Proca generalization of electrodynamics admits the possibility that the universe could possess a net electric charge uniformly distributed throughout space, while possessing no electric field. A charged intergalactic (and intragalactic) medium of this kind could contain enough energy to be of cosmological importance. A general-relativistic model of cosmological expansion dominated by such a charged background has been calculated, and is consistent with present observational limits on the Hubble constant, the decleration parameter, and the age of the universe. However, if this cosmology applied at the present epoch, the very early expansion of the universe would have been much more rapid than in conventional ''big bang'' cosmologies, too rapid for cosmological nucleosynthesis or thermalization of the background radiation to have occurred. Hence, domination of the present expansion by background charge appears to be incompatible with the 3 K background and big-bang production of light elements. If the present background charge density were sufficiently small (but not strictly zero), expansion from the epoch of nucleosynthesis would proceed according to the conventional scenario, but the energy due to the background charge would have dominated at some earlier epoch. This last possibility leads to equality of pressure and energy density in the primordial universe, a condition of special significance in certain cosmological theories
Nonlocal gravity. Conceptual aspects and cosmological predictions
Belgacem, Enis; Dirian, Yves; Foffa, Stefano; Maggiore, Michele
2018-03-01
Even if the fundamental action of gravity is local, the corresponding quantum effective action, that includes the effect of quantum fluctuations, is a nonlocal object. These nonlocalities are well understood in the ultraviolet regime but much less in the infrared, where they could in principle give rise to important cosmological effects. Here we systematize and extend previous work of our group, in which it is assumed that a mass scale Λ is dynamically generated in the infrared, giving rise to nonlocal terms in the quantum effective action of gravity. We give a detailed discussion of conceptual aspects related to nonlocal gravity (including causality, degrees of freedom, ambiguities related to the boundary conditions of the nonlocal operator, scenarios for the emergence of a dynamical scale in the infrared) and of the cosmological consequences of these models. The requirement of providing a viable cosmological evolution severely restricts the form of the nonlocal terms, and selects a model (the so-called RR model) that corresponds to a dynamical mass generation for the conformal mode. For such a model: (1) there is a FRW background evolution, where the nonlocal term acts as an effective dark energy with a phantom equation of state, providing accelerated expansion without a cosmological constant. (2) Cosmological perturbations are well behaved. (3) Implementing the model in a Boltzmann code and comparing with observations we find that the RR model fits the CMB, BAO, SNe, structure formation data and local H0 measurements at a level statistically equivalent to ΛCDM. (4) Bayesian parameter estimation shows that the value of H0 obtained in the RR model is higher than in ΛCDM, reducing to 2.0σ the tension with the value from local measurements. (5) The RR model provides a prediction for the sum of neutrino masses that falls within the limits set by oscillation and terrestrial experiments (in contrast to ΛCDM, where letting the sum of neutrino masses vary as a free
International Nuclear Information System (INIS)
Wang Xiaomin; Tegmark, Max; Zaldarriaga, Matias
2002-01-01
We perform a detailed analysis of the latest cosmic microwave background (CMB) measurements (including BOOMERaNG, DASI, Maxima and CBI), both alone and jointly with other cosmological data sets involving, e.g., galaxy clustering and the Lyman Alpha Forest. We first address the question of whether the CMB data are internally consistent once calibration and beam uncertainties are taken into account, performing a series of statistical tests. With a few minor caveats, our answer is yes, and we compress all data into a single set of 24 bandpowers with associated covariance matrix and window functions. We then compute joint constraints on the 11 parameters of the 'standard' adiabatic inflationary cosmological model. Our best fit model passes a series of physical consistency checks and agrees with essentially all currently available cosmological data. In addition to sharp constraints on the cosmic matter budget in good agreement with those of the BOOMERaNG, DASI and Maxima teams, we obtain a heaviest neutrino mass range 0.04-4.2 eV and the sharpest constraints to date on gravity waves which (together with preference for a slight red-tilt) favor 'small-field' inflation models
Green, Dan
2016-01-01
This volume makes explicit use of the synergy between cosmology and high energy physics, for example, supersymmetry and dark matter, or nucleosynthesis and the baryon-to-photon ratio. In particular the exciting possible connection between the recently discovered Higgs scalar and the scalar field responsible for inflation is explored.The recent great advances in the accuracy of the basic cosmological parameters is exploited in that no free scale parameters such as h appear, rather the basic calculations are done numerically using all sources of energy density simultaneously. Scripts are provided that allow the reader to calculate exact results for the basic parameters. Throughout MATLAB tools such as symbolic math, numerical solutions, plots and 'movies' of the dynamical evolution of systems are used. The GUI package is also shown as an example of the real time manipulation of parameters which is available to the reader.All the MATLAB scripts are made available to the reader to explore examples of the uses of ...
International Nuclear Information System (INIS)
Hawking, S.W.
1984-01-01
The subject of these lectures is quantum effects in cosmology. The author deals first with situations in which the gravitational field can be treated as a classical, unquantized background on which the quantum matter fields propagate. This is the case with inflation at the GUT era. Nevertheless the curvature of spacetime can have important effects on the behaviour of the quantum fields and on the development of long-range correlations. He then turns to the question of the quantization of the gravitational field itself. The plan of these lectures is as follows: Euclidean approach to quantum field theory in flat space; the extension of techniques to quantum fields on a curved background with the four-sphere, the Euclidean version of De Sitter space as a particular example; the GUT era; quantization of the gravitational field by Euclidean path integrals; mini superspace model. (Auth.)
Krioukov, Dmitri; Kitsak, Maksim; Sinkovits, Robert S; Rideout, David; Meyer, David; Boguñá, Marián
2012-01-01
Prediction and control of the dynamics of complex networks is a central problem in network science. Structural and dynamical similarities of different real networks suggest that some universal laws might accurately describe the dynamics of these networks, albeit the nature and common origin of such laws remain elusive. Here we show that the causal network representing the large-scale structure of spacetime in our accelerating universe is a power-law graph with strong clustering, similar to many complex networks such as the Internet, social, or biological networks. We prove that this structural similarity is a consequence of the asymptotic equivalence between the large-scale growth dynamics of complex networks and causal networks. This equivalence suggests that unexpectedly similar laws govern the dynamics of complex networks and spacetime in the universe, with implications to network science and cosmology.
Narlikar, Jayant Vishnu
2002-01-01
The third edition of this successful textbook is fully updated and includes important recent developments in cosmology. It begins with an introduction to cosmology and general relativity, and goes on to cover the mathematical models of standard cosmology. The physical aspects of cosmology, including primordial nucleosynthesis, the astroparticle physics of inflation, and the current ideas on structure formation are discussed. Alternative models of cosmology are reviewed, including the model of Quasi-Steady State Cosmology, which has recently been proposed as an alternative to Big Bang Cosmology.
Remapping dark matter halo catalogues between cosmological simulations
Mead, A. J.; Peacock, J. A.
2014-05-01
We present and test a method for modifying the catalogue of dark matter haloes produced from a given cosmological simulation, so that it resembles the result of a simulation with an entirely different set of parameters. This extends the method of Angulo & White, which rescales the full particle distribution from a simulation. Working directly with the halo catalogue offers an advantage in speed, and also allows modifications of the internal structure of the haloes to account for non-linear differences between cosmologies. Our method can be used directly on a halo catalogue in a self-contained manner without any additional information about the overall density field; although the large-scale displacement field is required by the method, this can be inferred from the halo catalogue alone. We show proof of concept of our method by rescaling a matter-only simulation with no baryon acoustic oscillation (BAO) features to a more standard Λ cold dark matter model containing a cosmological constant and a BAO signal. In conjunction with the halo occupation approach, this method provides a basis for the rapid generation of mock galaxy samples spanning a wide range of cosmological parameters.
Possible role of Berry phase in inflationary cosmological perturbations
International Nuclear Information System (INIS)
Pal, Barun Kumar; Pal, Supratik; Basu, B
2012-01-01
Here we have derived a cosmological analogue of Berry phase by obtaining the corresponding wavefunction for the system of inflationary cosmological perturbations solving the Schrodinger equation. We have further shown that cosmological Berry phase can be related inflationary observable parameters. As a result one can, atleast in principle, establish a supplementary probe of inflationary cosmology through the measurement of the associated Berry phase. But we do not make any strong comment on this.
Statefinder diagnostic for cosmology with the abnormally weighting energy hypothesis
International Nuclear Information System (INIS)
Liu Daojun; Liu Weizhong
2008-01-01
In this paper, we apply the statefinder diagnostic to the cosmology with the abnormally weighting energy hypothesis (AWE cosmology), in which dark energy in the observational (ordinary matter) frame results from the violation of the weak equivalence principle by pressureless matter. It is found that there exist closed loops in the statefinder plane, which is an interesting characteristic of the evolution trajectories of statefinder parameters and can be used to distinguish AWE cosmology from other cosmological models
A method for generating subgroup parameters from resonance tables and the SPART code
International Nuclear Information System (INIS)
Devan, K.; Mohanakrishnan, P.
1995-01-01
A method for generating subgroup or band parameters from resonance tables is described. A computer code SPART was written using this method. This code generates the subgroup parameters for any number of bands within the specified broad groups at different temperatures by reading the required input data from the binary cross section library in the Cadarache format. The results obtained with SPART code for two bands were compared with that obtained from GROUPIE code and a good agreement was obtained. Results of the generation of subgroup parameters in four bands for sample case of 239 Pu from resonance tables of Cadarache Ver.2 library is also presented. 6 refs, 2 tabs
International Nuclear Information System (INIS)
Passos, E.J.V. de; Toledo Piza, A.F.R. de.
The properties of the subspaces of the many-body Hilbert space which are associated with the use of the Generator Coordinate Method (GCM) in connection with one parameter, and with two-conjugate parameter families of generator states are examined in detail. It is shown that natural orthonormal base vectors in each case are immediately related to Peierls-Voccoz and Peierls-Thouless projections respectively. Through the formal consideration of a canonical transformation to collective, P and Q, and intrinsic degrees of freedom, the properties of the GCM subspaces with respect to the kinematical separation of these degrees of freedom are discussed in detail. An application is made, using the ideas developed in this paper, a) to translation; b) to illustrate the qualitative understanting of the content of existing GCM calculations of giant ressonances in light nuclei and c) to the definition of appropriate asymptotic states in current GCM descriptions of scattering [pt
Multi-dimensional cosmology and GUP
Energy Technology Data Exchange (ETDEWEB)
Zeynali, K.; Motavalli, H. [Department of Theoretical Physics and Astrophysics, University of Tabriz, 51666-16471, Tabriz (Iran, Islamic Republic of); Darabi, F., E-mail: k.zeinali@arums.ac.ir, E-mail: f.darabi@azaruniv.edu, E-mail: motavalli@tabrizu.ac.ir [Department of Physics, Azarbaijan Shahid Madani University, 53714-161, Tabriz (Iran, Islamic Republic of)
2012-12-01
We consider a multidimensional cosmological model with FRW type metric having 4-dimensional space-time and d-dimensional Ricci-flat internal space sectors with a higher dimensional cosmological constant. We study the classical cosmology in commutative and GUP cases and obtain the corresponding exact solutions for negative and positive cosmological constants. It is shown that for negative cosmological constant, the commutative and GUP cases result in finite size universes with smaller size and longer ages, and larger size and shorter age, respectively. For positive cosmological constant, the commutative and GUP cases result in infinite size universes having late time accelerating behavior in good agreement with current observations. The accelerating phase starts in the GUP case sooner than the commutative case. In both commutative and GUP cases, and for both negative and positive cosmological constants, the internal space is stabilized to the sub-Planck size, at least within the present age of the universe. Then, we study the quantum cosmology by deriving the Wheeler-DeWitt equation, and obtain the exact solutions in the commutative case and the perturbative solutions in GUP case, to first order in the GUP small parameter, for both negative and positive cosmological constants. It is shown that good correspondence exists between the classical and quantum solutions.
Multi-dimensional cosmology and GUP
International Nuclear Information System (INIS)
Zeynali, K.; Motavalli, H.; Darabi, F.
2012-01-01
We consider a multidimensional cosmological model with FRW type metric having 4-dimensional space-time and d-dimensional Ricci-flat internal space sectors with a higher dimensional cosmological constant. We study the classical cosmology in commutative and GUP cases and obtain the corresponding exact solutions for negative and positive cosmological constants. It is shown that for negative cosmological constant, the commutative and GUP cases result in finite size universes with smaller size and longer ages, and larger size and shorter age, respectively. For positive cosmological constant, the commutative and GUP cases result in infinite size universes having late time accelerating behavior in good agreement with current observations. The accelerating phase starts in the GUP case sooner than the commutative case. In both commutative and GUP cases, and for both negative and positive cosmological constants, the internal space is stabilized to the sub-Planck size, at least within the present age of the universe. Then, we study the quantum cosmology by deriving the Wheeler-DeWitt equation, and obtain the exact solutions in the commutative case and the perturbative solutions in GUP case, to first order in the GUP small parameter, for both negative and positive cosmological constants. It is shown that good correspondence exists between the classical and quantum solutions
Integrated cosmological probes: concordance quantified
Energy Technology Data Exchange (ETDEWEB)
Nicola, Andrina; Amara, Adam; Refregier, Alexandre, E-mail: andrina.nicola@phys.ethz.ch, E-mail: adam.amara@phys.ethz.ch, E-mail: alexandre.refregier@phys.ethz.ch [Department of Physics, ETH Zürich, Wolfgang-Pauli-Strasse 27, CH-8093 Zürich (Switzerland)
2017-10-01
Assessing the consistency of parameter constraints derived from different cosmological probes is an important way to test the validity of the underlying cosmological model. In an earlier work [1], we computed constraints on cosmological parameters for ΛCDM from an integrated analysis of CMB temperature anisotropies and CMB lensing from Planck, galaxy clustering and weak lensing from SDSS, weak lensing from DES SV as well as Type Ia supernovae and Hubble parameter measurements. In this work, we extend this analysis and quantify the concordance between the derived constraints and those derived by the Planck Collaboration as well as WMAP9, SPT and ACT. As a measure for consistency, we use the Surprise statistic [2], which is based on the relative entropy. In the framework of a flat ΛCDM cosmological model, we find all data sets to be consistent with one another at a level of less than 1σ. We highlight that the relative entropy is sensitive to inconsistencies in the models that are used in different parts of the analysis. In particular, inconsistent assumptions for the neutrino mass break its invariance on the parameter choice. When consistent model assumptions are used, the data sets considered in this work all agree with each other and ΛCDM, without evidence for tensions.
Cosmological models in general relativity
Indian Academy of Sciences (India)
Cosmological models in general relativity. B B PAUL. Department of Physics, Nowgong College, Nagaon, Assam, India. MS received 4 October 2002; revised 6 March 2003; accepted 21 May 2003. Abstract. LRS Bianchi type-I space-time filled with perfect fluid is considered here with deceler- ation parameter as variable.
Forecast and analysis of the cosmological redshift drift
Energy Technology Data Exchange (ETDEWEB)
Lazkoz, Ruth; Leanizbarrutia, Iker [University of the Basque Country UPV/EHU, Department of Theoretical Physics, Bilbao (Spain); Salzano, Vincenzo [University of Szczecin, Institute of Physics, Sczcecin (Poland)
2018-01-15
The cosmological redshift drift could lead to the next step in high-precision cosmic geometric observations, becoming a direct and irrefutable test for cosmic acceleration. In order to test the viability and possible properties of this effect, also called Sandage-Loeb (SL) test, we generate a model-independent mock data set in order to compare its constraining power with that of the future mock data sets of Type Ia Supernovae (SNe) and Baryon Acoustic Oscillations (BAO). The performance of those data sets is analyzed by testing several cosmological models with the Markov chain Monte Carlo (MCMC) method, both independently as well as combining all data sets. Final results show that, in general, SL data sets allow for remarkable constraints on the matter density parameter today Ω{sub m} on every tested model, showing also a great complementarity with SNe and BAO data regarding dark energy parameters. (orig.)
Forecast and analysis of the cosmological redshift drift.
Lazkoz, Ruth; Leanizbarrutia, Iker; Salzano, Vincenzo
2018-01-01
The cosmological redshift drift could lead to the next step in high-precision cosmic geometric observations, becoming a direct and irrefutable test for cosmic acceleration. In order to test the viability and possible properties of this effect, also called Sandage-Loeb (SL) test, we generate a model-independent mock data set in order to compare its constraining power with that of the future mock data sets of Type Ia Supernovae (SNe) and Baryon Acoustic Oscillations (BAO). The performance of those data sets is analyzed by testing several cosmological models with the Markov chain Monte Carlo (MCMC) method, both independently as well as combining all data sets. Final results show that, in general, SL data sets allow for remarkable constraints on the matter density parameter today [Formula: see text] on every tested model, showing also a great complementarity with SNe and BAO data regarding dark energy parameters.
Generation of a library of two-group diffusion and kinetics parameters for DYN3D
International Nuclear Information System (INIS)
Petkov, P.T.; Christoskov, I.D.; Kamenov, K.; Antov, A.
2002-01-01
A library of two-group diffusion and kinetics parameters has been generated for the neutron kinetics code DYN3D for analysis of reactivity initiated accidents for the WWER-440 reactors, based on the MAGRU approximation methodology for the diffusion and kinetics parameters. The accuracy of this methodology has been tested and the conclusion is that it is not adequate. A new approximation methodology, based on interpolation for the most widely varying parameters, i.e. the moderator temperature and density, and on approximation for all other independent parameters, is presented. The methodology of calculation of the kinetics parameters using primary data from ENDF-B/VI is described in detail (Authors)
A choice of the parameters of NPP steam generators on the basis of vector optimization
International Nuclear Information System (INIS)
Lemeshev, V.U.; Metreveli, D.G.
1981-01-01
The optimization problem of the parameters of the designed systems is considered as the problem of multicriterion optimization. It is proposed to choose non-dominant, optimal according to Pareto, parameters. An algorithm is built on the basis of the required and sufficient non-dominant conditions to find non-dominant solutions. This algorithm has been employed to solve the problem on a choice of optimal parameters for the counterflow shell-tube steam generator of NPP of BRGD type [ru
International Nuclear Information System (INIS)
Niedermann, Florian; Schneider, Robert
2015-01-01
We derive the modified Friedmann equations for a generalization of the Dvali-Gabadadze-Porrati (DGP) model in which the brane has one additional compact dimension. The main new feature is the emission of gravitational waves into the bulk. We study two classes of solutions: first, if the compact dimension is stabilized, the waves vanish and one exactly recovers DGP cosmology. However, a stabilization by means of physical matter is not possible for a tension-dominated brane, thus implying a late time modification of 4D cosmology different from DGP. Second, for a freely expanding compact direction, we find exact attractor solutions with zero 4D Hubble parameter despite the presence of a 4D cosmological constant. The model hence constitutes an explicit example of dynamical degravitation at the full nonlinear level. Without stabilization, however, there is no 4D regime and the model is ruled out observationally, as we demonstrate explicitly by comparing to supernova data
Cosmological tests of coupled Galileons
International Nuclear Information System (INIS)
Brax, Philippe; Burrage, Clare; Davis, Anne-Christine; Gubitosi, Giulia
2015-01-01
We investigate the cosmological properties of Galileon models which admit Minkowski space as a stable solution in vacuum. This is motivated by stable, positive tension brane world constructions that give rise to Galileons. We include both conformal and disformal couplings to matter and focus on constraints on the theory that arise because of these couplings. The disformal coupling to baryonic matter is extremely constrained by astrophysical and particle physics effects. The disformal coupling to photons induces a cosmological variation of the speed of light and therefore distorsions of the Cosmic Microwave Background spectrum which are known to be very small. The conformal coupling to baryons leads to a variation of particle masses since Big Bang Nucleosynthesis which is also tightly constrained. We consider the background cosmology of Galileon models coupled to Cold Dark Matter (CDM), photons and baryons and impose that the speed of light and particle masses respect the observational bounds on cosmological time scales. We find that requiring that the equation of state for the Galileon models must be close to -1 now restricts severely their parameter space and can only be achieved with a combination of the conformal and disformal couplings. This leads to large variations of particle masses and the speed of light which are not compatible with observations. As a result, we find that cosmological Galileon models are viable dark energy theories coupled to dark matter but their couplings, both disformal and conformal, to baryons and photons must be heavily suppressed making them only sensitive to CDM
Correlation of Steam Generator Mixing Parameters for Severe Accident Hot-Leg Natural Circulation
Energy Technology Data Exchange (ETDEWEB)
Liao, Yehong; Guentay, Salih [Paul Scherrer Institut, Villigen PSI, CH-5232 (Switzerland)
2008-07-01
Steam generator inlet plenum mixing phenomenon with hot-leg counter-current natural circulation during a PWR station blackout severe accident is one of the important processes governing which component will fail first as a result of thermal challenge from the circulating gas with high temperature and pressure. Since steam generator tube failure represents bypass release of fission product from the reactor to environment, study of inlet plenum mixing parameters is important to risk analysis. Probability distribution functions of individual mixing parameter should be obtained from experiments or calculated by analysis. In order to perform sensitivity studies of the synergetic effects of all mixing parameters on the severe accident-induced steam generator tube failure, the distribution and correlation of these mixing parameters must be known to remove undue conservatism in thermal-hydraulic calculations. This paper discusses physical laws governing three mixing parameters in a steady state and setups the correlation among these mixing parameters. The correlation is then applied to obtain the distribution of one of the mixing parameters that has not been given in the previous CFD analysis. Using the distributions and considering the inter-dependence of the three mixing parameters, three sensitivity cases enveloping the mixing parameter uncertainties are recommended for the plant analysis. (authors)
Dimensional cosmological principles
International Nuclear Information System (INIS)
Chi, L.K.
1985-01-01
The dimensional cosmological principles proposed by Wesson require that the density, pressure, and mass of cosmological models be functions of the dimensionless variables which are themselves combinations of the gravitational constant, the speed of light, and the spacetime coordinates. The space coordinate is not the comoving coordinate. In this paper, the dimensional cosmological principle and the dimensional perfect cosmological principle are reformulated by using the comoving coordinate. The dimensional perfect cosmological principle is further modified to allow the possibility that mass creation may occur. Self-similar spacetimes are found to be models obeying the new dimensional cosmological principle
Cosmology and particle physics
International Nuclear Information System (INIS)
Turner, M.S.
1985-01-01
The author reviews the standard cosmology, focusing on primordial nucleosynthesis, and discusses how the standard cosmology has been used to place constraints on the properties of various particles. Baryogenesis is examined in which the B, C, CP violating interactions in GUTs provide a dynamical explanation for the predominance of matter over antimatter and the present baryon-to-baryon ratio. Monoposes, cosmology and astrophysics are reviewed. The author also discusses supersymmetry/supergravity and cosmology, superstrings and cosmology in extra dimensions, and axions, astrophics, and cosmology
Hierarchical parameter estimation of DFIG and drive train system in a wind turbine generator
Institute of Scientific and Technical Information of China (English)
Xueping PAN; Ping JU; Feng WU; Yuqing JIN
2017-01-01
A new hierarchical parameter estimation method for doubly fed induction generator (DFIG) and drive train system in a wind turbine generator (WTG) is proposed in this paper.Firstly,the parameters of the DFIG and the drive train are estimated locally under different types of disturbances.Secondly,a coordination estimation method is further applied to identify the parameters of the DFIG and the drive train simultaneously with the purpose of attaining the global optimal estimation results.The main benefit of the proposed scheme is the improved estimation accuracy.Estimation results confirm the applicability of the proposed estimation technique.
Effects of Chemistry Parameters of Primary Water affecting Leakage of Steam Generator Tube Cracks
Energy Technology Data Exchange (ETDEWEB)
Shin, D. M.; Cho, N. C.; Kang, Y. S.; Lee, K. H. [KHNP CRI, Daejeon (Korea, Republic of)
2016-10-15
Degradation of steam generator (SG) tubes can affect pressure boundary tightness. As a defense-in-depth measure, primary to secondary leak monitoring program for steam generators is implemented, and operation is allowed under leakage limits in nuclear power plants. Chemistry parameters that affect steam generator tube leakage due to primary water stress corrosion cracking (PWSCC) are investigated in this study. Tube sleeves were installed to inhibit leakage and improve tube integrity as a part of maintenance methods. Steam generators occurred small leak during operation have been replaced with new steam generators according to plant maintenance strategies. The correlations between steam generator leakage and chemistry parameters are presented. Effects of primary water chemistry parameters on leakage from tube cracks were investigated for the steam generators experiencing small leak. Unit A experienced small leakage from steam generator tubes in the end of operation cycle. It was concluded that increased solubility of oxides due to high pHT could make leakage paths, and low boron concentration lead to less blockage in cracks. Increased dissolved hydrogen may retard crack propagations, but it did not reduce leak rate of the leaking steam generator. In order to inhibit and reduce leakage, pH{sub T} was controlled by servicing cation bed operation. The test results of decreasing pHT indicate low pHT can reduce leak rate of PWSCC cracks in the end of cycle.
Effects of Chemistry Parameters of Primary Water affecting Leakage of Steam Generator Tube Cracks
International Nuclear Information System (INIS)
Shin, D. M.; Cho, N. C.; Kang, Y. S.; Lee, K. H.
2016-01-01
Degradation of steam generator (SG) tubes can affect pressure boundary tightness. As a defense-in-depth measure, primary to secondary leak monitoring program for steam generators is implemented, and operation is allowed under leakage limits in nuclear power plants. Chemistry parameters that affect steam generator tube leakage due to primary water stress corrosion cracking (PWSCC) are investigated in this study. Tube sleeves were installed to inhibit leakage and improve tube integrity as a part of maintenance methods. Steam generators occurred small leak during operation have been replaced with new steam generators according to plant maintenance strategies. The correlations between steam generator leakage and chemistry parameters are presented. Effects of primary water chemistry parameters on leakage from tube cracks were investigated for the steam generators experiencing small leak. Unit A experienced small leakage from steam generator tubes in the end of operation cycle. It was concluded that increased solubility of oxides due to high pHT could make leakage paths, and low boron concentration lead to less blockage in cracks. Increased dissolved hydrogen may retard crack propagations, but it did not reduce leak rate of the leaking steam generator. In order to inhibit and reduce leakage, pH_T was controlled by servicing cation bed operation. The test results of decreasing pHT indicate low pHT can reduce leak rate of PWSCC cracks in the end of cycle
International Nuclear Information System (INIS)
Cai Qi; Shang Yanlong; Chen Lisheng; Zhao Yuguang
2013-01-01
Vector-universal generating function was presented to analyze the availability of thermodynamic system with multiple performance parameters. Vector-universal generating function of component's performance was defined, the arithmetic model based on vector-universal generating function was derived for the thermodynamic system, and the calculation method was given for state probability of multi-state component. With the stochastic simulation of the degeneration trend of the multiple factors, the system availability with multiple performance parameters was obtained under composite factors. It is shown by an example that the results of the availability obtained by the binary availability analysis method are somewhat conservative, and the results considering parameter failure based on vector-universal generating function reflect the operation characteristics of the thermodynamic system better. (authors)
Inflation and the theory of cosmological perturbations
International Nuclear Information System (INIS)
Riotto, A.
2003-01-01
These lectures provide a pedagogical introduction to inflation and the theory of cosmological perturbations generated during inflation which are thought to be the origin of structure in the universe. (author)
Wormholes and the cosmological constant problem.
Klebanov, I.
The author reviews the cosmological constant problem and the recently proposed wormhole mechanism for its solution. Summation over wormholes in the Euclidean path integral for gravity turns all the coupling parameters into dynamical variables, sampled from a probability distribution. A formal saddle point analysis results in a distribution with a sharp peak at the cosmological constant equal to zero, which appears to solve the cosmological constant problem. He discusses the instabilities of the gravitational Euclidean path integral and the difficulties with its interpretation. He presents an alternate formalism for baby universes, based on the "third quantization" of the Wheeler-De Witt equation. This approach is analyzed in a minisuperspace model for quantum gravity, where it reduces to simple quantum mechanics. Once again, the coupling parameters become dynamical. Unfortunately, the a priori probability distribution for the cosmological constant and other parameters is typically a smooth function, with no sharp peaks.
International Nuclear Information System (INIS)
Gaisser, T.K.; Shafi, Q.; Barr, S.M.; Seckel, D.; Rusjan, E.; Fletcher, R.S.
1991-01-01
This report discusses research of professor at Bartol research institute in the following general areas: particle phenomenology and non-accelerator physics; particle physics and cosmology; theories with higher symmetry; and particle astrophysics and cosmology
International Nuclear Information System (INIS)
Heller, M.
1985-01-01
Two Friedman's cosmological papers (1922, 1924) and his own interpretation of the obtained results are briefly reviewed. Discussion follows of Friedman's role in the early development of relativistic cosmology. 18 refs. (author)
Kunze, Kerstin E.
2016-12-20
Cosmology is becoming an important tool to test particle physics models. We provide an overview of the standard model of cosmology with an emphasis on the observations relevant for testing fundamental physics.
Identification of Synchronous Generator Electric Parameters Connected to the Distribution Grid
Directory of Open Access Journals (Sweden)
Frolov M. Yu.
2017-04-01
Full Text Available According to modern trends, the power grids with distributed generation will have an open system architecture. It means that active consumers, owners of distributed power units, including mobile units, must have free access to the grid, like when using internet, so it is necessary to have plug and play technologies. Thanks to them, the system will be able to identify the unit type and the unit parameters. Therefore, the main aim of research, described in the paper, was to develop and research a new method of electric parameters identification of synchronous generator. The main feature of the proposed method is that parameter identification is performed while the generator to the grid, so it fits in the technological process of operation of the machine and does not influence on the connection time of the machine. For the implementation of the method, it is not necessary to create dangerous operation modes for the machine or to have additional expensive equipment and it can be used for salient pole machines and round rotor machines. The parameter identification accuracy can be achieved by more accurate account of electromechanical transient process, and making of overdetermined system with many more numbers of equations. Parameter identification will be made with each generator connection to the grid. Comparing data obtained from each connection, the middle values can be find by numerical method, and thus, each subsequent identification will accurate the machine parameters.
Roos, Matts
2015-01-01
The Fourth Edition of Introduction to Cosmology provides a concise, authoritative study of cosmology at an introductory level. Starting from elementary principles and the early history of cosmology, the text carefully guides the student on to curved spacetimes, special and general relativity, gravitational lensing, the thermal history of the Universe, and cosmological models, including extended gravity models, black holes and Hawking's recent conjectures on the not-so-black holes.
Particle physics and cosmology
International Nuclear Information System (INIS)
Turner, M.S.; Schramm, D.N.
1985-01-01
During the past year, the research of the members of our group has spanned virtually all the topics at the interface of cosmology and particle physics: inflationary Universe scenarios, astrophysical and cosmological constraints on particle properties, ultra-high energy cosmic ray physics, quantum field theory in curved space-time, cosmology with extra dimensions, superstring cosmology, neutrino astronomy with large, underground detectors, and the formation of structure in the Universe
Experimental studies of parameters affecting the heat generation in friction stir welding process
Directory of Open Access Journals (Sweden)
Mijajlović Miroslav M.
2012-01-01
Full Text Available Heat generation is a complex process of transformation of a specific type of energy into heat. During friction stir welding, one part of mechanical energy delivered to the welding tool is consumed in the welding process, another is used for deformational processes etc., and the rest of the energy is transformed into heat. The analytical procedure for the estimation of heat generated during friction stir welding is very complex because it includes a significant number of variables and parameters, and many of them cannot be fully mathematically explained. Because of that, the analytical model for the estimation of heat generated during friction stir welding defines variables and parameters that dominantly affect heat generation. These parameters are numerous and some of them, e. g. loads, friction coefficient, torque, temperature, are estimated experimentally. Due to the complex geometry of the friction stir welding process and requirements of the measuring equipment, adequate measuring configurations and specific constructional solutions that provide adequate measuring positions are necessary. This paper gives an overview of the process of heat generation during friction stir welding, the most influencing parameters on heat generation, constructional solutions for the measuring equipment needed for these experimental researches and examples of measured values.
Phantom cosmologies and fermions
International Nuclear Information System (INIS)
Chimento, Luis P; Forte, Monica; Devecchi, Fernando P; Kremer, Gilberto M
2008-01-01
Form invariance transformations can be used for constructing phantom cosmologies starting with conventional cosmological models. In this work we reconsider the scalar field case and extend the discussion to fermionic fields, where the 'phantomization' process exhibits a new class of possible accelerated regimes. As an application we analyze the cosmological constant group for a fermionic seed fluid
Particle physics and cosmology
International Nuclear Information System (INIS)
Schramm, D.N.; Turner, M.S.
1982-06-01
work is described in these areas: cosmological baryon production; cosmological production of free quarks and other exotic particle species; the quark-hadron transition in the early universe; astrophysical and cosmological constraints on particle properties; massive neutrinos; phase transitions in the early universe; and astrophysical implications of an axion-like particle
International Nuclear Information System (INIS)
Weinberg, S.
1989-01-01
Cosmological constant problem is discussed. History of the problem is briefly considered. Five different approaches to solution of the problem are described: supersymmetry, supergravity, superstring; anthropic approach; mechamism of lagrangian alignment; modification of gravitation theory and quantum cosmology. It is noted that approach, based on quantum cosmology is the most promising one
. ______________________________________________________________________________________ Nobelist George Smoot to Direct Korean Cosmology Institute Nobel Laureate George Smoot has been appointed director of a new cosmology institute in South Korea that will work closely with the year-old Berkeley the Early Universe (IEU) at EWHA Womans University in Seoul, Korea will provide cosmology education
International Nuclear Information System (INIS)
Davies, P.
1991-01-01
The main concepts of cosmology are discussed, and some of the misconceptions are clarified. The features of big bang cosmology are examined, and it is noted that the existence of the cosmic background radiation provides welcome confirmation of the big bang theory. Calculations of relative abundances of the elements conform with observations, further strengthening the confidence in the basic ideas of big bang cosmology
CERN. Geneva. Audiovisual Unit
2001-01-01
Cosmology and particle physics have enjoyed a useful relationship over the entire histories of both subjects. Today, ideas and techniques in cosmology are frequently used to elucidate and constrain theories of elementary particles. These lectures give an elementary overview of the essential elements of cosmology, which is necessary to understand this relationship.
CERN. Geneva
1999-01-01
Cosmology and particle physics have enjoyed a useful relationship over the entire histories of both subjects. Today, ideas and techniques in cosmology are frequently used to elucidate and constrain theories of elementary particles. These lectures give an elementary overview of the essential elements of cosmology, which is necessary to understand this relationship.
International Nuclear Information System (INIS)
Langer, M.
2007-01-01
This is a very concise introductory lecture to Cosmology. We start by reviewing the basics of homogeneous and isotropic cosmology. We then spend some time on the description of the Cosmic Microwave Background. Finally, a small section is devoted to the discussion of the cosmological constant and of some of the related problems
Cosmology with decaying particles
International Nuclear Information System (INIS)
Turner, M.S.
1984-09-01
We consider a cosmological model in which an unstable massive relic particle species (denoted by X) has an initial mass density relative to baryons β -1 identically equal rho/sub X//rho/sub B/ >> 1, and then decays recently (redshift z less than or equal to 1000) into particles which are still relativistic today (denoted by R). We write down and solve the coupled equations for the cosmic scale factor a(t), the energy density in the various components (rho/sub X/, rho/sub R/, rho/sub B/), and the growth of linear density perturbations (delta rho/rho). The solutions form a one parameter (β) family of solutions; physically β -1 approx. = (Ω/sub R//Ω/sub NR/) x (1 + z/sub D/) = (ratio today of energy density of relativistic to nonrelativistic particles) x (1 + redshift of (decay)). We discuss the observational implications of such a cosmological model and compare our results to earlier results computed in the simultaneous decay approximation. In an appendix we briefly consider the case where one of the decay products of the X is massive and becomes nonrelativistic by the present epoch. 21 references
Cosmology with decaying particles
Energy Technology Data Exchange (ETDEWEB)
Turner, M.S.
1984-09-01
We consider a cosmological model in which an unstable massive relic particle species (denoted by X) has an initial mass density relative to baryons ..beta../sup -1/ identically equal rho/sub X//rho/sub B/ >> 1, and then decays recently (redshift z less than or equal to 1000) into particles which are still relativistic today (denoted by R). We write down and solve the coupled equations for the cosmic scale factor a(t), the energy density in the various components (rho/sub X/, rho/sub R/, rho/sub B/), and the growth of linear density perturbations (delta rho/rho). The solutions form a one parameter (..beta..) family of solutions; physically ..beta../sup -1/ approx. = (..cap omega../sub R//..cap omega../sub NR/) x (1 + z/sub D/) = (ratio today of energy density of relativistic to nonrelativistic particles) x (1 + redshift of (decay)). We discuss the observational implications of such a cosmological model and compare our results to earlier results computed in the simultaneous decay approximation. In an appendix we briefly consider the case where one of the decay products of the X is massive and becomes nonrelativistic by the present epoch. 21 references.
Chamcham, Khalil; Silk, Joseph; Barrow, John D.; Saunders, Simon
2017-04-01
Part I. Issues in the Philosophy of Cosmology: 1. Cosmology, cosmologia and the testing of cosmological theories George F. R. Ellis; 2. Black holes, cosmology and the passage of time: three problems at the limits of science Bernard Carr; 3. Moving boundaries? - comments on the relationship between philosophy and cosmology Claus Beisbart; 4. On the question why there exists something rather than nothing Roderich Tumulka; Part II. Structures in the Universe and the Structure of Modern Cosmology: 5. Some generalities about generality John D. Barrow; 6. Emergent structures of effective field theories Jean-Philippe Uzan; 7. Cosmological structure formation Joel R. Primack; 8. Formation of galaxies Joseph Silk; Part III. Foundations of Cosmology: Gravity and the Quantum: 9. The observer strikes back James Hartle and Thomas Hertog; 10. Testing inflation Chris Smeenk; 11. Why Boltzmann brains do not fluctuate into existence from the de Sitter vacuum Kimberly K. Boddy, Sean M. Carroll and Jason Pollack; 12. Holographic inflation revised Tom Banks; 13. Progress and gravity: overcoming divisions between general relativity and particle physics and between physics and HPS J. Brian Pitts; Part IV. Quantum Foundations and Quantum Gravity: 14. Is time's arrow perspectival? Carlo Rovelli; 15. Relational quantum cosmology Francesca Vidotto; 16. Cosmological ontology and epistemology Don N. Page; 17. Quantum origin of cosmological structure and dynamical reduction theories Daniel Sudarsky; 18. Towards a novel approach to semi-classical gravity Ward Struyve; Part V. Methodological and Philosophical Issues: 19. Limits of time in cosmology Svend E. Rugh and Henrik Zinkernagel; 20. Self-locating priors and cosmological measures Cian Dorr and Frank Arntzenius; 21. On probability and cosmology: inference beyond data? Martin Sahlén; 22. Testing the multiverse: Bayes, fine-tuning and typicality Luke A. Barnes; 23. A new perspective on Einstein's philosophy of cosmology Cormac O
Topics in inflationary cosmology
International Nuclear Information System (INIS)
Kahn, R.N.
1985-01-01
This thesis examines several topics in the theory of inflationary cosmology. It first proves the existence of Hawking Radiation during the slow-rolling period of a new inflationary universe. It then derives and somewhat extends Bardeen's gauge invariant formalism for calculating the growth of linear gravitational perturbations in a Friedmann-Robertson-Walker cosmological background. This formalism is then applied, first to several new inflationary universe models all of which show a Zel'dovich spectrum of fluctuations, but with amplitude sigma(100 4 ) above observational limits. The general formalism is next applied to models that exhibit primordial inflation. Fluctuations in these models also exhibit a Zel'dovich spectrum here with an acceptable amplitude. Finally the thesis presents the results of new, numerical calculations. A classical, (2 + 1) dimensional computer model is developed that includes a Higgs field (which drives inflation) along with enough auxiliary fields to generate dynamically not only a thermal bath, but also the fluctuations that naturally accompany that bath. The thesis ends with a discussion of future prospects
Indian cosmogonies and cosmologies
Directory of Open Access Journals (Sweden)
Pajin Dušan
2011-01-01
Full Text Available Various ideas on how the universe appeared and develops, were in Indian tradition related to mythic, religious, or philosophical ideas and contexts, and developed during some 3.000 years - from the time of Vedas, to Puranas. Conserning its appeareance, two main ideas were presented. In one concept it appeared out of itself (auto-generated, and gods were among the first to appear in the cosmic sequences. In the other, it was a kind of divine creation, with hard work (like the dismembering of the primal Purusha, or as emanation of divine dance. Indian tradition had also various critiques of mythic and religious concepts (from the 8th c. BC, to the 6c., who favoured naturalistic and materialistic explanations, and concepts, in their cosmogony and cosmology. One the peculiarities was that indian cosmogony and cosmology includes great time spans, since they used a digit system which was later (in the 13th c. introduced to Europe by Fibonacci (Leonardo of Pisa, 1170-1240.
Particle physics and cosmology
International Nuclear Information System (INIS)
Kolb, E.W.
1986-10-01
This series of lectures is about the role of particle physics in physical processes that occurred in the very early stages of the bug gang. Of particular interest is the role of particle physics in determining the evolution of the early Universe, and the effect of particle physics on the present structure of the Universe. The use of the big bang as a laboratory for placing limits on new particle physics theories will also be discussed. Section 1 reviews the standard cosmology, including primordial nucleosynthesis. Section 2 reviews the decoupling of weakly interacting particles in the early Universe, and discusses neutrino cosmology and the resulting limits that may be placed on the mass and lifetime of massive neutrinos. Section 3 discusses the evolution of the vacuum through phase transitions in the early Universe and the formation of topological defects in the transitions. Section 4 covers recent work on the generation of the baryon asymmetry by baryon-number violating reactions in Grand Unified Theories, and mentions some recent work on baryon number violation effects at the electroweak transition. Section 5 is devoted to theories of cosmic inflation. Finally, Section 6 is a discussion of the role of extra spatial dimensions in the evolution of the early Universe. 78 refs., 32 figs., 6 tabs
Philosophical Roots of Cosmology
Ivanovic, M.
2008-10-01
We shall consider the philosophical roots of cosmology in the earlier Greek philosophy. Our goal is to answer the question: Are earlier Greek theories of pure philosophical-mythological character, as often philosophers cited it, or they have scientific character. On the bases of methodological criteria, we shall contend that the latter is the case. In order to answer the question about contemporary situation of the relation philosophy-cosmology, we shall consider the next question: Is contemporary cosmology completely independent of philosophical conjectures? The answer demands consideration of methodological character about scientific status of contemporary cosmology. We also consider some aspects of the relation contemporary philosophy-cosmology.
Stabilization of Voltage Parameters of Induction Generator Excited by a Voltage Inverter
Directory of Open Access Journals (Sweden)
Padalko D.A.
2017-12-01
Full Text Available The article reveals the operational aspects of induction generator. Methods for stabilization of induction generator (IG parameters under inverter excitation are investigated. The study was carried out using mathematical description and simulation modeling in MATLAB Simulink. The paper provides analysis of causes of generated voltage amplitude and frequency displacement when the loading condition and the rate vary. Due to the parametric resonance nature of IG self-excitation, the author introduces the expression that allows estimating the capacitor capacitance required to maintain the generation process, depending on the rotor speed of electric machine, load nature and rate. Based on the studies, it was proved that it is possible to stabilize the IG voltage parameters by maintaining the magnetizing circuit inductance Lm at the constant level., and realizing a control law close to U/f = const. The study proves that using the inverter together with the voltage regulator allows ensuring the quality of electricity corresponding to modern standards. The necessity of problem solving of the required quality of the voltage by the harmonic component for the exciter - inverter with PWM is shown. The prospects of the power generation system based on induction machine (IM with a semiconductor frequency converter, which serves as an adjustable supplier of capacitive current for IM for autonomous objects, are substantiated. The use of semiconductor frequency converters makes it possible to provide high stability of the output voltage parameters and good speed of the mechatronic generation system with an asynchronous machine.
A natural cosmological constant from chameleons
International Nuclear Information System (INIS)
Nastase, Horatiu; Weltman, Amanda
2015-01-01
We present a simple model where the effective cosmological constant appears from chameleon scalar fields. For a Kachru–Kallosh–Linde–Trivedi (KKLT)-inspired form of the potential and a particular chameleon coupling to the local density, patches of approximately constant scalar field potential cluster around regions of matter with density above a certain value, generating the effect of a cosmological constant on large scales. This construction addresses both the cosmological constant problem (why Λ is so small, yet nonzero) and the coincidence problem (why Λ is comparable to the matter density now)
A natural cosmological constant from chameleons
Directory of Open Access Journals (Sweden)
Horatiu Nastase
2015-07-01
Full Text Available We present a simple model where the effective cosmological constant appears from chameleon scalar fields. For a Kachru–Kallosh–Linde–Trivedi (KKLT-inspired form of the potential and a particular chameleon coupling to the local density, patches of approximately constant scalar field potential cluster around regions of matter with density above a certain value, generating the effect of a cosmological constant on large scales. This construction addresses both the cosmological constant problem (why Λ is so small, yet nonzero and the coincidence problem (why Λ is comparable to the matter density now.
A natural cosmological constant from chameleons
Energy Technology Data Exchange (ETDEWEB)
Nastase, Horatiu, E-mail: nastase@ift.unesp.br [Instituto de Física Teórica, UNESP-Universidade Estadual Paulista, R. Dr. Bento T. Ferraz 271, Bl. II, Sao Paulo 01140-070, SP (Brazil); Weltman, Amanda, E-mail: amanda.weltman@uct.ac.za [Astrophysics, Cosmology & Gravity Center, Department of Mathematics and Applied Mathematics, University of Cape Town, Private Bag, Rondebosch 7700 (South Africa)
2015-07-30
We present a simple model where the effective cosmological constant appears from chameleon scalar fields. For a Kachru–Kallosh–Linde–Trivedi (KKLT)-inspired form of the potential and a particular chameleon coupling to the local density, patches of approximately constant scalar field potential cluster around regions of matter with density above a certain value, generating the effect of a cosmological constant on large scales. This construction addresses both the cosmological constant problem (why Λ is so small, yet nonzero) and the coincidence problem (why Λ is comparable to the matter density now)
Towards an observational appraisal of string cosmology
Energy Technology Data Exchange (ETDEWEB)
Mulryne, David J [Astronomy Unit, School of Mathematical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS (United Kingdom); Ward, John, E-mail: d.mulryne@qmul.ac.uk, E-mail: jwa@uvic.ca [Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 1A1 (Canada)
2011-10-21
We review the current observational status of string cosmology when confronted with experimental datasets. We begin by defining common observational parameters and discuss how they are determined for a given model. Then we review the observable footprints of several string theoretic models, discussing the significance of various potential signals. Throughout we comment on present and future prospects of finding evidence for string theory in cosmology and on significant issues for the future.
Towards an observational appraisal of string cosmology
International Nuclear Information System (INIS)
Mulryne, David J; Ward, John
2011-01-01
We review the current observational status of string cosmology when confronted with experimental datasets. We begin by defining common observational parameters and discuss how they are determined for a given model. Then we review the observable footprints of several string theoretic models, discussing the significance of various potential signals. Throughout we comment on present and future prospects of finding evidence for string theory in cosmology and on significant issues for the future.
Cosmological imprints of pre-inflationary particles
Energy Technology Data Exchange (ETDEWEB)
Fialkov, Anastasia; Itzhaki, Nissan; Kovetz, Ely D., E-mail: anastasia.fialkov@gmail.com, E-mail: nitzhaki@post.tau.ac.il, E-mail: elykovetz@gmail.com [Tel-Aviv University, Ramat-Aviv, 69978 (Israel)
2010-02-01
We study some of the cosmological imprints of pre-inflationary particles. We show that each such particle provides a seed for a spherically symmetric cosmic defect. The profile of this cosmic defect is fixed and its magnitude is linear in a single parameter that is determined by the mass of the pre-inflationary particle. We study the CMB and peculiar velocity imprints of this cosmic defect and suggest that it could explain some of the large scale cosmological anomalies.
Cosmological imprints of pre-inflationary particles
International Nuclear Information System (INIS)
Fialkov, Anastasia; Itzhaki, Nissan; Kovetz, Ely D.
2010-01-01
We study some of the cosmological imprints of pre-inflationary particles. We show that each such particle provides a seed for a spherically symmetric cosmic defect. The profile of this cosmic defect is fixed and its magnitude is linear in a single parameter that is determined by the mass of the pre-inflationary particle. We study the CMB and peculiar velocity imprints of this cosmic defect and suggest that it could explain some of the large scale cosmological anomalies
BMSSM implications for cosmology
International Nuclear Information System (INIS)
Bernal, Nicolas; Blum, Kfir; Nir, Yosef; Losada, Marta
2009-01-01
The addition of non-renormalizable terms involving the Higgs fields to the MSSM (BMSSM) ameliorates the little hierarchy problem of the MSSM. We analyze in detail the two main cosmological issues affected by the BMSSM: dark matter and baryogenesis. The regions for which the relic abundance of the LSP is consistent with WMAP and collider constraints are identified, showing that the bulk region and other previously excluded regions are now permitted. Requiring vacuum stability limits the allowed regions. Based on a two-loop finite temperature effective potential analysis, we show that the electroweak phase transition can be sufficiently first order in regions that for the MSSM are incompatible with the LEP Higgs mass bound, including parameter values of tan β∼ t -tilde 1 >m t , m Q < < TeV.
International Nuclear Information System (INIS)
Tayler, R.J.
1983-01-01
The standard model of the hot big bang cosmological theory, which appears to be in agreement, at least qualitatively, with the observed properties of the Universe, assumes that the early Universe was homogeneous and isotropic and that it has been continuously expanding from a state characterized by very high temperature and density, where matter and radiation were to a good approximation in a state of thermodynamic equilibrium. In this standard model, it is assumed that baryon number, charge number and the various lepton numbers are all conserved. Only the baryon number is non-zero and this, expressed as the ratio of the net number of baryons (baryons minus antibaryons) to the number of photons per unit volume is the undefined parameter in the model. The author discusses the importance of knowing how many types of neutrinos there are with regard to the He 4 abundance, and the implication of a small, non-zero neutrino mass. (Auth.)
Experimental parameter study for passive vortex generators on a 30% thick airfoil
Baldacchino, D.; Simao Ferreira, C.; De Tavernier, D.A.M.; Timmer, W.A.; van Bussel, G.J.W.
2018-01-01
Passive vane-type vortex generators (VGs) are commonly used on wind turbine blades to mitigate the effects of flow separation. However, significant uncertainty surrounds VG design guidelines. Understanding the influence of VG parameters on airfoil performance requires a systematic approach
Li, Jiangtao; Zhao, Zheng; Li, Longjie; He, Jiaxin; Li, Chenjie; Wang, Yifeng; Su, Can
2017-09-01
A transmission line transformer has potential advantages for nanosecond pulse generation including excellent frequency response and no leakage inductance. The wave propagation process in a secondary mode line is indispensable due to an obvious inside transient electromagnetic transition in this scenario. The equivalent model of the transmission line transformer is crucial for predicting the output waveform and evaluating the effects of magnetic cores on output performance. However, traditional lumped parameter models are not sufficient for nanosecond pulse generation due to the natural neglect of wave propagations in secondary mode lines based on a lumped parameter assumption. In this paper, a distributed parameter model of transmission line transformer was established to investigate wave propagation in the secondary mode line and its influential factors through theoretical analysis and experimental verification. The wave propagation discontinuity in the secondary mode line induced by magnetic cores is emphasized. Characteristics of the magnetic core under a nanosecond pulse were obtained by experiments. Distribution and formation of the secondary mode current were determined for revealing essential wave propagation processes in secondary mode lines. The output waveform and efficiency were found to be affected dramatically by wave propagation discontinuity in secondary mode lines induced by magnetic cores. The proposed distributed parameter model was proved more suitable for nanosecond pulse generation in aspects of secondary mode current, output efficiency, and output waveform. In depth, comprehension of underlying mechanisms and a broader view of the working principle of the transmission line transformer for nanosecond pulse generation can be obtained through this research.
Energy Technology Data Exchange (ETDEWEB)
Oliveira, Sebastiao E.M. de; Padua Guarini, Antonio de [Centro de Pesquisas de Energia Eletrica (CEPEL), Rio de Janeiro, RJ (Brazil); Souza, Joao A. de; Valgas, Helio M; Pinto, Roberto del Giudice R. [Companhia Energetica de Minas Gerais (CEMIG), Belo Horizonte, MG (Brazil)
1994-12-31
This work describes the results of the set frequency response tests performed in the generator number 2, 6.9 kV, 25 MVA, of Camargos hydroelectric power plant, CEMIG, and the parameters relatives to determined structures of model. This tests are unpublished in Brazil. (author) 7 refs., 16 figs., 7 tabs.
Chemical and physical parameters affecting the performance of the Os-191/Ir-191m generator
International Nuclear Information System (INIS)
Packard, A.B.; Butler, T.A.; Knapp, F.F.; O'Brien, G.M.; Treves, S.
1984-01-01
The development of an Os-191/Ir-191m generator suitable for radionuclide angiography in humans has elicited much interest. This generator employs ''(OsO 2 Cl 4 ) 2- '' on AG MP-1 anion exchange resin with a Dowex-2 scavenger column and is eluted with normal saline at pH 1. The parent Os species is, however, neither welldefined nor homogeneous leading to less than optimal breakthrough of Os-191 (5 x 10 -3 %) and modest Ir-191m yield (10-15%). The effect of a range of parameters on generator performance has been evaluated as has been the way in which the assembly and loading process affects generator performance. In addition, a number of potential alternative generator systems have been evaluated
International Nuclear Information System (INIS)
Kim, Joo Yeon; Ryu, Hyung Joon; Jung, Gyu Hwan; Lee, Jai Ki
2011-01-01
The dependency within the sequential realizations in the generated Markov chains and their reliabilities are monitored by introducing the autocorrelation and the potential scale reduction factor (PSRF) by model parameters in the atmospheric dispersion. These two diagnostics have been applied for the posterior quantities of the release point and the release rate inferred through the inverse tracking of unknown model parameters for the Yonggwang atmospheric tracer experiment in Korea. The autocorrelations of model parameters are decreasing to low values approaching to zero with increase of lag, resulted in decrease of the dependencies within the two sequential realizations. Their PSRFs are reduced to within 1.2 and the adequate simulation number recognized from these results. From these two convergence diagnostics, the validation of Markov chains generated have been ensured and PSRF then is especially suggested as the efficient tool for convergence monitoring for the source reconstruction in atmospheric dispersion. (author)
Comparative parameters of solar cells for power generation: test stand implementation using DSP
International Nuclear Information System (INIS)
Álvarez López, Ramón Antonio; García Angarita, Maritza Andrea
2014-01-01
The technologies used in solar modules are distinguished mainly by th eenergy conversion efficiency. Consequently, the module selection is critic to the long term performance of photovoltaic generating facility. Therefore, the selection must be supported by experimental results obtained under a specific operation condition. The article implements an experimentally test for obtain the characteristic parameters of a solar module, we analyze the energy conversion efficiency and other correlated parameters that directly affect the performance of a photovoltaic generator. The results show that the use of a rapid prototyping system using open hardware, such as TMS320F28335 development kit makes it easy to build a test photovoltaic generation systems. Latter justified by the low cost of such devices and ease of programming. (author)
Cosmological perturbation theory and quantum gravity
Energy Technology Data Exchange (ETDEWEB)
Brunetti, Romeo [Dipartimento di Matematica, Università di Trento,Via Sommarive 14, 38123 Povo TN (Italy); Fredenhagen, Klaus [II Institute für Theoretische Physik, Universität Hamburg,Luruper Chaussee 149, 22761 Hamburg (Germany); Hack, Thomas-Paul [Institute für Theoretische Physik, Universität Leipzig,Brüderstr. 16, 04103 Leipzig (Germany); Pinamonti, Nicola [Dipartimento di Matematica, Università di Genova,Via Dodecaneso 35, 16146 Genova (Italy); INFN, Sezione di Genova,Via Dodecaneso 33, 16146 Genova (Italy); Rejzner, Katarzyna [Department of Mathematics, University of York,Heslington, York YO10 5DD (United Kingdom)
2016-08-04
It is shown how cosmological perturbation theory arises from a fully quantized perturbative theory of quantum gravity. Central for the derivation is a non-perturbative concept of gauge-invariant local observables by means of which perturbative invariant expressions of arbitrary order are generated. In particular, in the linearised theory, first order gauge-invariant observables familiar from cosmological perturbation theory are recovered. Explicit expressions of second order quantities are presented as well.
Ultracompact Minihalos as Probes of Inflationary Cosmology.
Aslanyan, Grigor; Price, Layne C; Adams, Jenni; Bringmann, Torsten; Clark, Hamish A; Easther, Richard; Lewis, Geraint F; Scott, Pat
2016-09-30
Cosmological inflation generates primordial density perturbations on all scales, including those far too small to contribute to the cosmic microwave background. At these scales, isolated ultracompact minihalos of dark matter can form well before standard structure formation, if the perturbations have sufficient amplitude. Minihalos affect pulsar timing data and are potentially bright sources of gamma rays. The resulting constraints significantly extend the observable window of inflation in the presence of cold dark matter, coupling two of the key problems in modern cosmology.
Behavior of cosmological models with varying G
International Nuclear Information System (INIS)
Barrow, J.D.; Parsons, P.
1997-01-01
We provide a detailed analysis of Friedmann-Robertson-Walker universes in a wide range of scalar-tensor theories of gravity. We apply solution-generating methods to three parametrized classes of scalar-tensor theory which lead naturally to general relativity in the weak-field limit. We restrict the parameters which specify these theories by the requirements imposed by the weak-field tests of gravitation theories in the solar system and by the requirement that viable cosmological solutions be obtained. We construct a range of exact solutions for open, closed, and flat isotropic universes containing matter with equation of state p≤(1)/(3)ρ and in vacuum. We study the range of early- and late-time behaviors displayed, examine when there is a open-quotes bounceclose quotes at early times, and expansion maxima in closed models. copyright 1997 The American Physical Society
Extending cosmology: the metric approach
Mendoza, S.
2012-01-01
Comment: 2012, Extending Cosmology: The Metric Approach, Open Questions in Cosmology; Review article for an Intech "Open questions in cosmology" book chapter (19 pages, 3 figures). Available from: http://www.intechopen.com/books/open-questions-in-cosmology/extending-cosmology-the-metric-approach
International Nuclear Information System (INIS)
Kapron, H.
1976-01-01
The investigations of pulsation in the MHD generators are described. The influence of termodynamic parameters pulsation on electric parameters of the MHD generator is presented using the method of little disturbances. The results of this investigation are formulas for momentary and average values of: electrical conductivity, the Hall parameter, current density and intensity of electrical field. Analitical investigations were verified by the experiments. (author)
Rapid generation of control parameters of Multi-Infeed system through online simulation
Directory of Open Access Journals (Sweden)
Rasool Aazim
2017-05-01
Full Text Available Simulated Self-Generated - Particle Swarm optimization (SSG-PSO toolbox that automatically generates PI control parameters very quickly in PSCAD is designed. This toolbox operates by utilizing transient simulation to evaluate objective function and converges the fitness values of objective function through PSO algorithm during run time simulation of Multi-infeed HVDC systems. Integral Square Error-Objective Function (ISE-OF is used to accomplish the task. To make the toolbox faster, ranges are set for PSO generated value that limit the time of data acquisition for the objective function by only considering transition time of a system. This toolbox has a capability to optimize multiple controllers at same time. The PI values are generated faster and the results are showing markedly improved performance of a system during startup and under fault condition. The experimental results are presented in this paper.
Modified mean generation time parameter in the neutron point kinetics equations
Energy Technology Data Exchange (ETDEWEB)
Diniz, Rodrigo C.; Gonçalves, Alessandro C.; Rosa, Felipe S.S., E-mail: alessandro@nuclear.ufrj.br, E-mail: frosa@if.ufrj.br [Coordenacao de Pos-Graduacao e Pesquisa de Engenharia (PEN/COPPE/UFRJ), Rio de Janeiro, RJ (Brazil)
2017-07-01
This paper proposes an approximation for the modified point kinetics equations proposed by NUNES et. al, 2015, through the adjustment of a kinetic parameter. This approximation consists of analyzing the terms of the modified point kinetics equations in order to identify the least important ones for the solution, resulting in a modification of the mean generation time parameter that incorporates all influences of the additional terms of the modified kinetics. This approximation is applied on the inverse kinetics, to compare the results with the inverse kinetics from the modified kinetics in order to validate the proposed model. (author)
Modified mean generation time parameter in the neutron point kinetics equations
International Nuclear Information System (INIS)
Diniz, Rodrigo C.; Gonçalves, Alessandro C.; Rosa, Felipe S.S.
2017-01-01
This paper proposes an approximation for the modified point kinetics equations proposed by NUNES et. al, 2015, through the adjustment of a kinetic parameter. This approximation consists of analyzing the terms of the modified point kinetics equations in order to identify the least important ones for the solution, resulting in a modification of the mean generation time parameter that incorporates all influences of the additional terms of the modified kinetics. This approximation is applied on the inverse kinetics, to compare the results with the inverse kinetics from the modified kinetics in order to validate the proposed model. (author)
Directory of Open Access Journals (Sweden)
Balbi Amedeo
2013-09-01
Full Text Available Time has always played a crucial role in cosmology. I review some of the aspects of the present cosmological model which are more directly related to time, such as: the definition of a cosmic time; the existence of typical timescales and epochs in an expanding universe; the problem of the initial singularity and the origin of time; the cosmological arrow of time.
Inflation and quantum cosmology
International Nuclear Information System (INIS)
Linde, A.
1991-01-01
In this article a review of the present status of inflationary cosmology is given. We start with a discussion of the simplest version of the chaotic inflation scenario. Then we discuss some recent develoments in the inflationary cosmology, including the theory of a self-reproducing inflationary universe (eternal chaotic inflation). We do it with the help of stochastic approach to inflation. The results obtained within this approach are compared with the results obtained in the context of Euclidean quantum cosmology. (WL)
International Nuclear Information System (INIS)
Surdin, M.
1980-01-01
It is shown that viewed from the 'outside', our universe is a black hole. Hence the 'inside' cosmology considered is termed as the Bright Universe Cosmology. The model proposed avoids the singularities of cosmologies of the Big Bang variety, it gives a good account of the redshifts, the cosmic background radiation, the number counts; it also gives a satisfactory explanation of the 'large numbers coincidence' and of the variation in time of fundamental constants. (Auth.)
Cosmology [2011 European School of High-Energy Physics
Energy Technology Data Exchange (ETDEWEB)
Rubakov, V A [Moscow, INR (Russian Federation)
2014-07-01
In these lectures we first concentrate on the cosmological problems which, hopefully, have to do with the new physics to be probed at the LHC: the nature and origin of dark matter and generation of matter-antimatter asymmetry. We give several examples showing the LHC cosmological potential. These are WIMPs as cold dark matter, gravitinos as warm dark matter, and electroweak baryogenesis as a mechanism for generating matter-antimatter asymmetry. In the remaining part of the lectures we discuss the cosmological perturbations as a tool for studying the epoch preceeding the conventional hot stage of the cosmological evolution.
The cosmological constant in theories with finite spacetime
International Nuclear Information System (INIS)
Kummer, Janis
2014-08-01
We study the role of the cosmological constant in different theories with finite spacetime. The cosmological constant appears both as an initial condition and as a constant of integration. In the context of the cosmological constant problem a new model will be presented. This modification of general relativity generates a small, non-vanishing cosmological constant, which is radiatively stable. The dynamics of the expansion of the universe in this model will be analyzed. Eventually, we try to solve the emergent problems concerning the generation of accelerated expansion using a quintessence model of dark energy.
Energy Technology Data Exchange (ETDEWEB)
Evans, Annette; Strezov, Vladimir; Evans, Tim
2010-09-15
The sustainability parameters of electricity generation have been assessed by the application of eight key indicators. Photovoltaics, wind, hydro, geothermal, biomass, natural gas, coal and nuclear power have been assessed according to their price, greenhouse gas emissions, efficiency, land use, water use, availability, limitations and social impacts on a per kilowatt hour basis. The relevance of this information to the Australian context is discussed. Also included are the results of a survey on Australian opinions regarding electricity generation, which found that Australian prefer solar electricity above any other method, however coal, biomass and nuclear power have low acceptance.
Self-accelerating universe in Galileon cosmology
International Nuclear Information System (INIS)
Silva, Fabio P.; Koyama, Kazuya
2009-01-01
We present a cosmological model with a solution that self-accelerates at late times without signs of ghost instabilities on small scales. The model is a natural extension of the Brans-Dicke (BD) theory including a nonlinear derivative interaction, which appears in a theory with the Galilean shift symmetry. The existence of the self-accelerating universe requires a negative BD parameter but, thanks to the nonlinear term, small fluctuations around the solution are stable on small scales. General relativity is recovered at early times and on small scales by this nonlinear interaction via the Vainshtein mechanism. At late time, gravity is strongly modified and the background cosmology shows a phantomlike behavior and the growth rate of structure formation is enhanced. Thus this model leaves distinct signatures in cosmological observations and it can be distinguished from standard LCDM cosmology.
Improved standard cosmology: Comparison with observation
International Nuclear Information System (INIS)
Wesson, P.S.
1982-01-01
A cosmological model describing inhomogeneous clusters of galaxies embedded in a homogeneous background is compared to observation. In this model, a cluster is described as a spherically symmetric distribution of matter with an inverse-square density law and an isothermal equation of state, while the background universe is essentially the Einstein/de Sitter one of standard cosmology, but with a small pressure. The model is found to be in overall good agreement with observation, and its adjustable parameters are assigned numerical values. The equation of state for a cluster and the finite cosmological pressure are properties of the model which can in principle be investigated by carrying out observations. Subject headings: cosmology: galaxies: clusters of: relativity
Development of the Universe and New Cosmology
Sakharov, Alexander S
2003-01-01
Cosmology is undergoing an explosive period of activity, fueled both by new, accurate astrophysical data and by innovative theoretical developments. Cosmological parameters such as the total density of the Universe and the rate of cosmological expansion are being precisely measured for the first time, and a consistent standard picture of the Universe is beginning to emerge. Recent developments in cosmology give rise the intriguing possibility that all structures in the Universe, from superclusters to planets, had a quantum-mechanical origin in its earliest moments. Furthermore, these ideas are not idle theorizing, but predictive, and subject to meaningful experimental test. We review the concordance model of the development of the Universe, as well as evidence for the observational revolution that this field is going through. This already provides us with important information on particle physics, which is inaccessible to accelerators.
International Nuclear Information System (INIS)
Feng, Jonathan L.
2005-01-01
Cosmology now provides unambiguous, quantitative evidence for new particle physics. I discuss the implications of cosmology for supersymmetry and vice versa. Topics include: motivations for supersymmetry; supersymmetry breaking; dark energy; freeze out and WIMPs; neutralino dark matter; cosmologically preferred regions of minimal supergravity; direct and indirect detection of neutralinos; the DAMA and HEAT signals; inflation and reheating; gravitino dark matter; Big Bang nucleosynthesis; and the cosmic microwave background. I conclude with speculations about the prospects for a microscopic description of the dark universe, stressing the necessity of diverse experiments on both sides of the particle physics/cosmology interface
International Nuclear Information System (INIS)
Sasaki, Misao
1983-01-01
We review the recent status of the inflationary cosmology. After exhibiting the essence of difficulties associated with the horizon, flatness and baryon number problems in the standard big-bang cosmology, we discuss that the inflationary universe scenario is one of the most plausible solutions to these fundamental cosmological problems. Since there are two qualitatively different versions of the inflationary universe scenario, we review each of them separately and discuss merits and demerits of each version. The Hawking radiation in de Sitter space is also reviewed since it may play an essential role in the inflationary cosmology. (author)
Roos, Matts
2003-01-01
The Third Edition of the hugely successful Introduction to Cosmology provides a concise, authoritative study of cosmology at an introductory level. Starting from elementary principles and the history of cosmology, the text carefully guides the student on to curved spacetimes, general relativity, black holes, cosmological models, particles and symmetries, and phase transitions. Extensively revised, this latest edition includes broader and updated coverage of distance measures, gravitational lensing and waves, dark energy and quintessence, the thermal history of the Universe, inflation,
Directory of Open Access Journals (Sweden)
Shchinnikov P.A.
2011-04-01
Full Text Available It is presented analysis of the influence of parameters of state of the process of control on the increase of the fuel consumption of heat power generating units. There are presented results of calculations of the increase of the fuel consumption at the deviation of the working steam temperature and pressure from rated values. Result of calculus is compared with the experiment.
Cosmological anisotropy from non-comoving dark matter and dark energy
International Nuclear Information System (INIS)
Harko, Tiberiu; Lobo, Francisco S. N.
2013-01-01
We consider a cosmological model in which the two major fluid components of the Universe, dark energy and dark matter, flow with distinct four-velocities. This cosmological configuration is equivalent to a single anisotropic fluid, expanding with a four-velocity that is an appropriate combination of the two fluid four-velocities. The energy density of the single cosmological fluid is larger than the sum of the energy densities of the two perfect fluids, i.e., dark energy and dark matter, respectively, and contains a correction term due to the anisotropy generated by the differences in the four-velocities. Furthermore, the gravitational field equations of the two-fluid anisotropic cosmological model are obtained for a Bianchi type I geometry. By assuming that the non-comoving motion of the dark energy and dark matter induces small perturbations in the homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker type cosmological background, and that the anisotropy parameter is small, the equations of the cosmological perturbations due to the non-comoving nature of the two major components are obtained. The time evolution of the metric perturbations is explicitly obtained for the cases of the exponential and power law background cosmological expansion. The imprints of a non-comoving dark energy - dark matter on the Cosmic Microwave Background and on the luminosity distance are briefly discussed, and the temperature anisotropies and the quadrupole are explicitly obtained in terms of the metric perturbations of the flat background metric. Therefore, if there is a slight difference between the four-velocities of the dark energy and dark matter, the Universe would acquire some anisotropic characteristics, and its geometry will deviate from the standard FLRW one. In fact, the recent Planck results show that the presence of an intrinsic large scale anisotropy in the Universe cannot be excluded a priori, so that the model presented in this work can be considered as a
Regional averaging and scaling in relativistic cosmology
International Nuclear Information System (INIS)
Buchert, Thomas; Carfora, Mauro
2002-01-01
Averaged inhomogeneous cosmologies lie at the forefront of interest, since cosmological parameters such as the rate of expansion or the mass density are to be considered as volume-averaged quantities and only these can be compared with observations. For this reason the relevant parameters are intrinsically scale-dependent and one wishes to control this dependence without restricting the cosmological model by unphysical assumptions. In the latter respect we contrast our way to approach the averaging problem in relativistic cosmology with shortcomings of averaged Newtonian models. Explicitly, we investigate the scale-dependence of Eulerian volume averages of scalar functions on Riemannian three-manifolds. We propose a complementary view of a Lagrangian smoothing of (tensorial) variables as opposed to their Eulerian averaging on spatial domains. This programme is realized with the help of a global Ricci deformation flow for the metric. We explain rigorously the origin of the Ricci flow which, on heuristic grounds, has already been suggested as a possible candidate for smoothing the initial dataset for cosmological spacetimes. The smoothing of geometry implies a renormalization of averaged spatial variables. We discuss the results in terms of effective cosmological parameters that would be assigned to the smoothed cosmological spacetime. In particular, we find that on the smoothed spatial domain B-bar evaluated cosmological parameters obey Ω-bar B-bar m + Ω-bar B-bar R + Ω-bar B-bar A + Ω-bar B-bar Q 1, where Ω-bar B-bar m , Ω-bar B-bar R and Ω-bar B-bar A correspond to the standard Friedmannian parameters, while Ω-bar B-bar Q is a remnant of cosmic variance of expansion and shear fluctuations on the averaging domain. All these parameters are 'dressed' after smoothing out the geometrical fluctuations, and we give the relations of the 'dressed' to the 'bare' parameters. While the former provide the framework of interpreting observations with a 'Friedmannian bias
Multiverse understanding of cosmological coincidences
International Nuclear Information System (INIS)
Bousso, Raphael; Hall, Lawrence J.; Nomura, Yasunori
2009-01-01
There is a deep cosmological mystery: although dependent on very different underlying physics, the time scales of structure formation, of galaxy cooling (both radiatively and against the CMB), and of vacuum domination do not differ by many orders of magnitude, but are all comparable to the present age of the universe. By scanning four landscape parameters simultaneously, we show that this quadruple coincidence is resolved. We assume only that the statistical distribution of parameter values in the multiverse grows towards certain catastrophic boundaries we identify, across which there are drastic regime changes. We find order-of-magnitude predictions for the cosmological constant, the primordial density contrast, the temperature at matter-radiation equality, the typical galaxy mass, and the age of the universe, in terms of the fine structure constant and the electron, proton and Planck masses. Our approach permits a systematic evaluation of measure proposals; with the causal patch measure, we find no runaway of the primordial density contrast and the cosmological constant to large values.
International Nuclear Information System (INIS)
Shang Shuo; Fearon, Eamonn; Wellburn, Dan; Sato, Taku; Edwardson, Stuart; Dearden, G; Watkins, K G
2011-01-01
The laser assisted direct write (LADW) method can be used to generate electrical circuitry on a substrate by depositing metallic ink and curing the ink thermally by a laser. Laser curing has emerged over recent years as a novel yet efficient alternative to oven curing. This method can be used in situ, over complicated 3D contours of large parts (e.g. aircraft wings) and selectively cure over heat sensitive substrates, with little or no thermal damage. In previous studies, empirical methods have been used to generate processing windows for this technique, relating to the several interdependent processing parameters on which the curing quality and efficiency strongly depend. Incorrect parameters can result in a track that is cured in some areas and uncured in others, or in damaged substrates. This paper addresses the strong need for a quantitative model which can systematically output the processing conditions for a given combination of ink, substrate and laser source; transforming the LADW technique from a purely empirical approach, to a simple, repeatable, mathematically sound, efficient and predictable process. The method comprises a novel and generic finite element model (FEM) that for the first time predicts the evolution of the thermal profile of the ink track during laser curing and thus generates a parametric map which indicates the most suitable combination of parameters for process optimization. Experimental data are compared with simulation results to verify the accuracy of the model.
Inflation and late-time acceleration in braneworld cosmological models with varying brane tension
International Nuclear Information System (INIS)
Wong, K.C.; Cheng, K.S.; Harko, T.
2010-01-01
Braneworld models with variable brane tension λ introduce a new degree of freedom that allows for evolving gravitational and cosmological constants, the latter being a natural candidate for dark energy. We consider a thermodynamic interpretation of the varying brane tension models, by showing that the field equations with variable λ can be interpreted as describing matter creation in a cosmological framework. The particle creation rate is determined by the variation rate of the brane tension, as well as by the brane-bulk energy-matter transfer rate. We investigate the effect of a variable brane tension on the cosmological evolution of the Universe, in the framework of a particular model in which the brane tension is an exponentially dependent function of the scale factor. The resulting cosmology shows the presence of an initial inflationary expansion, followed by a decelerating phase, and by a smooth transition towards a late accelerated de Sitter type expansion. The varying brane tension is also responsible for the generation of the matter in the Universe (reheating period). The physical constraints on the model parameters, resulting from the observational cosmological data, are also investigated. (orig.)
International Nuclear Information System (INIS)
Baryshev, Yu.V.; Morozov, V.N.
1988-01-01
It is shown that MHD turbulence can be generated by collisionless shock waves due to anisotropy of the pressure behind the front of the reverse sock at the hot spot of a powerful radio galaxy. The energy density of the MHD turbulence generated behind the shock front is estimated. Analysis of the theoretical studies and experimental data on collisionless shock waves in the solar wind indicates that an important part is played by streams of ions reflected by the shock fronts, the streams generating plasma and MHD turbulence in the region ahead of the front. The extension of these ideas to shock waves in powerful radio galaxies must be made with care because of the great difference between the parameters of the shock waves in the two cases
Parameters of a supershort avalanche electron beam generated in atmospheric-pressure air
International Nuclear Information System (INIS)
Tarasenko, V. F.
2011-01-01
Conditions under which the number of runaway electrons in atmospheric-pressure air reaches ∼5 × 10 10 are determined. Recommendations for creating runaway electron accelerators are given. Methods for measuring the parameters of a supershort avalanche electron beam and X-ray pulses from gas-filled diodes, as well as the discharge current and gap voltage, are described. A technique for determining the instant of runaway electron generation with respect to the voltage pulse is proposed. It is shown that the reduction in the gap voltage and the decrease in the beam current coincide in time. The mechanism of intense electron beam generation in gas-filled diodes is analyzed. It is confirmed experimentally that, in optimal regimes, the number of electrons generated in atmospheric-pressure air with energies T > eU m , where U m is the maximum gap voltage, is relatively small.
Parameters of a supershort avalanche electron beam generated in atmospheric-pressure air
Tarasenko, V. F.
2011-05-01
Conditions under which the number of runaway electrons in atmospheric-pressure air reaches ˜5 × 1010 are determined. Recommendations for creating runaway electron accelerators are given. Methods for measuring the parameters of a supershort avalanche electron beam and X-ray pulses from gas-filled diodes, as well as the discharge current and gap voltage, are described. A technique for determining the instant of runaway electron generation with respect to the voltage pulse is proposed. It is shown that the reduction in the gap voltage and the decrease in the beam current coincide in time. The mechanism of intense electron beam generation in gas-filled diodes is analyzed. It is confirmed experimentally that, in optimal regimes, the number of electrons generated in atmospheric-pressure air with energies T > eU m , where U m is the maximum gap voltage, is relatively small.
Cosmology and CPT violating neutrinos
Energy Technology Data Exchange (ETDEWEB)
Barenboim, Gabriela; Salvado, Jordi [Universitat de Valencia-CSIC, Departament de Fisica Teorica y Instituto de Fisica Corpuscular, Burjassot (Spain)
2017-11-15
The combination charge conjugation-parity-time reversal (CPT) is a fundamental symmetry in our current understanding of nature. As such, testing CPT violation is a strongly motivated path to explore new physics. In this paper we study CPT violation in the neutrino sector, giving for the first time a bound, for a fundamental particle, in the CPT violating particle-antiparticle gravitational mass difference. We argue that cosmology is nowadays the only data sensitive to CPT violation for the neutrino-antineutrino mass splitting and we use the latest data release from Planck combined with the current baryonic-acoustic-oscillation measurement to perform a full cosmological analysis. To show the potential of the future experiments we also show the results for Euclid, a next generation large scale structure experiment. (orig.)
Exact cosmological solutions for MOG
International Nuclear Information System (INIS)
Roshan, Mahmood
2015-01-01
We find some new exact cosmological solutions for the covariant scalar-tensor-vector gravity theory, the so-called modified gravity (MOG). The exact solution of the vacuum field equations has been derived. Also, for non-vacuum cases we have found some exact solutions with the aid of the Noether symmetry approach. More specifically, the symmetry vector and also the Noether conserved quantity associated to the point-like Lagrangian of the theory have been found. Also we find the exact form of the generic vector field potential of this theory by considering the behavior of the relevant point-like Lagrangian under the infinitesimal generator of the Noether symmetry. Finally, we discuss the cosmological implications of the solutions. (orig.)
Particle physics and cosmology
International Nuclear Information System (INIS)
Ellis, J.; Nanopoulos, D.
1983-01-01
The authors describe the connection between cosmology and particle physics in an introductory way. In this connection the big bang theory and unified gauge models of strong, electromagnetic, and weak interactions are considered. Furthermore cosmological nucleosynthesis is discussed in this framework, and the problem of cosmic neutrinos is considered with special regards to its rest mass. (HSI).
Cosmology and particle physics
International Nuclear Information System (INIS)
Turner, M.S.
1986-01-01
Progress in cosmology has become linked to progress in elementary particle physics. In these six lectures, the author illustrates the two-way nature of the interplay between these fields by focusing on a few selected topics. In the next section the author reviews the standard cosmology, especially concentrating on primordial nucleosynthesis and discusses how the standard cosmology has been used to place constraints on the properties of various particles. Grand Unification makes two striking predictions: (i) B non-conservation; (ii) the existence of stable, superheavy magnetic monopoles. Both have had great cosmological impact. In the following section the author discusses baryogenesis, the very attractive scenario in which the B,C,CP violating interactions in GUTs provide a dynamical explanation for the predominance of matter over antimatter and the present baryon-to-photon ratio. Monopoles are a cosmological disaster and an astrophysicist's delight. In Section 4 discusses monopoles, cosmology, and astrophysics. In the fourth lecture the author discusses how a very early (t≤10/sup -34/ sec) phase transition associated with spontaneous symmetry breaking (SSB) has the potential to explain a handful of very fundamental cosmological facts, facts which can be accommodated by the standard cosmology, but which are not ''explained'' by it. The fifth lecture is devoted to a discussion of structure formation in the universe
Barkana, Rennan; Tsujikawa, Shinji; Kim, Jihn E; Nagamine, Kentaro
2018-01-01
The Encyclopedia of Cosmology, in four volumes, is a major, long-lasting, seminal reference at the graduate student level, laid out by the most prominent, respected researchers in the general field of Cosmology. These volumes will be a comprehensive review of the most important concepts and current status in the field, covering both theory and observation.
Astroparticle physics and cosmology
International Nuclear Information System (INIS)
Senjanovic, G.; Smirnov, A.Yu.; Thompson, G.
2001-01-01
In this volume a wide spectrum of topics of modern astroparticle physics, such as neutrino astrophysics, dark matter of the universe, high energy cosmic rays, topological defects in cosmology, γ-ray bursts, phase transitions at high temperatures, is covered. The articles written by top level experts in the field give a comprehensive view of the state-of-the-art of modern cosmology
Energy Technology Data Exchange (ETDEWEB)
Vilenkin, Alexander, E-mail: vilenkin@cosmos.phy.tufts.ed [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States)
2010-01-01
The 'new standard cosmology', based on the theory of inflation, has very impressive observational support. I review some outstanding problems of the new cosmology and the global view of the universe - the multiverse - that it suggests. I focus in particular on prospects for further observational tests of inflation and of the multiverse.
International Nuclear Information System (INIS)
Vilenkin, Alexander
2010-01-01
The n ew standard cosmology , based on the theory of inflation, has very impressive observational support. I review some outstanding problems of the new cosmology and the global view of the universe - the multiverse - that it suggests. I focus in particular on prospects for further observational tests of inflation and of the multiverse.
Astroparticle physics and cosmology
Energy Technology Data Exchange (ETDEWEB)
Senjanovic, G; Smirnov, A Yu; Thompson, G [eds.
2001-11-15
In this volume a wide spectrum of topics of modern astroparticle physics, such as neutrino astrophysics, dark matter of the universe, high energy cosmic rays, topological defects in cosmology, {gamma}-ray bursts, phase transitions at high temperatures, is covered. The articles written by top level experts in the field give a comprehensive view of the state-of-the-art of modern cosmology.
International Nuclear Information System (INIS)
Stecker, F.W.
1989-01-01
This paper discusses two aspects of antimatter and cosmology: 1. the fundamental cosmological question as to whether antimatter plays an equally important role as matter in the universe (overall baryon symmetry), and 2. cosmic-ray antimatter tests for the nature of the dark matter in the universe. (orig.)
Lesgourgues, Julien
2012-01-01
Neutrinos can play an important role in the evolution of the Universe, modifying some of the cosmological observables. In this contribution we summarize the main aspects of cosmological relic neutrinos and we describe how the precision of present cosmological data can be used to learn about neutrino properties, in particular their mass, providing complementary information to beta decay and neutrinoless double-beta decay experiments. We show how the analysis of current cosmological observations, such as the anisotropies of the cosmic microwave background or the distribution of large-scale structure, provides an upper bound on the sum of neutrino masses of order 1 eV or less, with very good perspectives from future cosmological measurements which are expected to be sensitive to neutrino masses well into the sub-eV range.
International Nuclear Information System (INIS)
Verde, L.
2011-01-01
This is the summary of two lectures that aim to give an overview of cosmology. I will not try to be toa rigorous in derivations, nor to give a full historical overview. The idea is to provide a 'taste' of cosmology and some of the interesting topics it covers. The standard cosmological model is presented and I highlight the successes of cosmology over the past decade or so. Keys to the development of the standard cosmological model are observations of the cosmic microwave background and of large-scale structure, which are introduced. Inflation and dark energy and the outlook for the future are also discussed. Slides from the lectures are available from the school web site: physicschool.web.cern.ch/PhysicSchool/CLASHEP/CLASHEP2011/. (author)
Classical and quantum cosmology
Calcagni, Gianluca
2017-01-01
This comprehensive textbook is devoted to classical and quantum cosmology, with particular emphasis on modern approaches to quantum gravity and string theory and on their observational imprint. It covers major challenges in theoretical physics such as the big bang and the cosmological constant problem. An extensive review of standard cosmology, the cosmic microwave background, inflation and dark energy sets the scene for the phenomenological application of all the main quantum-gravity and string-theory models of cosmology. Born of the author's teaching experience and commitment to bridging the gap between cosmologists and theoreticians working beyond the established laws of particle physics and general relativity, this is a unique text where quantum-gravity approaches and string theory are treated on an equal footing. As well as introducing cosmology to undergraduate and graduate students with its pedagogical presentation and the help of 45 solved exercises, this book, which includes an ambitious bibliography...
Verde, L.
2013-06-27
This is the summary of two lectures that aim to give an overview of cosmology. I will not try to be too rigorous in derivations, nor to give a full historical overview. The idea is to provide a "taste" of cosmology and some of the interesting topics it covers. The standard cosmological model is presented and I highlight the successes of cosmology over the past decade or so. Keys to the development of the standard cosmological model are observations of the cosmic microwave background and of large-scale structure, which are introduced. Inflation and dark energy and the outlook for the future are also discussed. Slides from the lectures are available from the school website: physicschool.web.cern.ch/PhysicSchool/CLASHEP/CLASHEP2011/.
International Nuclear Information System (INIS)
Gekman, O.
1982-01-01
The brief essay of the development of the main ideas of relativistic cosmology is presented. The Einstein's cosmological work about the Universe - ''Cosmological considerations in connection with the general relativity theory'' - gave the basis to all further treatments in this field. In 1922 A. Friedman's work appeared, in which the first expanding Universe model was proposed as a solution of the Einstein field equations. The model was spherically closed, but its curvature radius was a function of time. About 1955 the searches for anisotropic homogeneous solutions to Einstein field equation began. It turned out that isotropic cosmological models are unstable in general. The predominant part of them transform to anisotropic at insignificant breaking of isotropy. The discovery of isotropic background cosmic radiation in 1965, along with the Hubble low of the Universe expansion, served as the direct confirmation of cosmology based on the Einstein theory
Stecker, F. W.; Puget, J. L.
1972-01-01
Following the big-bang baryon symmetric cosmology of Omnes, the redshift was calculated to be on the order of 500-600. It is show that, at these redshifts, annihilation pressure at the boundaries between regions of matter and antimatter drives large scale supersonic turbulence which can trigger galaxy formation. This picture is consistent with the gamma-ray background observations discussed previously. Gravitational binding of galaxies then occurs at a redshift of about 70, at which time vortical turbulent velocities of about 3 x 10 to the 7th power cm/s lead to angular momenta for galaxies comparable with measured values.
Quantum symmetry, the cosmological constant and Planck-scale phenomenology
International Nuclear Information System (INIS)
Amelino-Camelia, Giovanni; Smolin, Lee; Starodubtsev, Artem
2004-01-01
We present a simple algebraic mechanism for the emergence of deformations of Poincare symmetries in the low-energy limit of quantum theories of gravity. The deformations, called κ-Poincare algebras, are parametrized by a dimensional parameter proportional to the Planck mass, and imply modified energy-momentum relations of a type that may be observable in near future experiments. Our analysis assumes that the low energy limit of a quantum theory of gravity must also involve a limit in which the cosmological constant is taken very small with respect to the Planck scale, and makes use of the fact that in some quantum theories of gravity the cosmological constant results in the (anti)de Sitter symmetry algebra being quantum deformed. We show that deformed Poincare symmetries inevitably emerge in the small-cosmological-constant limit of quantum gravity in 2 + 1 dimensions, where geometry does not have local degrees of freedom. In 3 + 1 dimensions we observe that, besides the quantum deformation of the (anti)de Sitter symmetry algebra, one must also take into account that there are local degrees of freedom leading to a renormalization of the generators for energy and momentum of the excitations. At the present level of development of quantum gravity in 3 + 1 dimensions, it is not yet possible to derive this renormalization from first principles, but we establish the conditions needed for the emergence of a deformed low energy limit symmetry algebra also in the case of 3 + 1 dimensions
Nonsingular bouncing cosmologies in light of BICEP2
International Nuclear Information System (INIS)
Cai, Yi-Fu; Quintin, Jerome; Saridakis, Emmanuel N.; Wilson-Ewing, Edward
2014-01-01
We confront various nonsingular bouncing cosmologies with the recently released BICEP2 data and investigate the observational constraints on their parameter space. In particular, within the context of the effective field approach, we analyze the constraints on the matter bounce curvaton scenario with a light scalar field, and the new matter bounce cosmology model in which the universe successively experiences a period of matter contraction and an ekpyrotic phase. Additionally, we consider three nonsingular bouncing cosmologies obtained in the framework of modified gravity theories, namely the Hořava-Lifshitz bounce model, the f(T) bounce model, and loop quantum cosmology
String cosmology basic ideas and general results
Veneziano, Gabriele
1995-01-01
After recalling a few basic concepts from cosmology and string theory, I will outline the main ideas/assumptions underlying (our own group's approach to) string cosmology and show how these lead to the definition of a two-parameter family of ``minimal" models. I will then briefly explain how to compute, in terms of those parameters, the spectrum of scalar, tensor and electromagnetic perturbations, and mention their most relevant physical consequences. More details on the latter part of this talk can be found in Maurizio Gasperini's contribution to these proceedings.
Cosmological measurements with general relativistic galaxy correlations
International Nuclear Information System (INIS)
Raccanelli, Alvise; Montanari, Francesco; Durrer, Ruth; Bertacca, Daniele; Doré, Olivier
2016-01-01
We investigate the cosmological dependence and the constraining power of large-scale galaxy correlations, including all redshift-distortions, wide-angle, lensing and gravitational potential effects on linear scales. We analyze the cosmological information present in the lensing convergence and in the gravitational potential terms describing the so-called ''relativistic effects'', and we find that, while smaller than the information contained in intrinsic galaxy clustering, it is not negligible. We investigate how neglecting them does bias cosmological measurements performed by future spectroscopic and photometric large-scale surveys such as SKA and Euclid. We perform a Fisher analysis using the CLASS code, modified to include scale-dependent galaxy bias and redshift-dependent magnification and evolution bias. Our results show that neglecting relativistic terms, especially lensing convergence, introduces an error in the forecasted precision in measuring cosmological parameters of the order of a few tens of percent, in particular when measuring the matter content of the Universe and primordial non-Gaussianity parameters. The analysis suggests a possible substantial systematic error in cosmological parameter constraints. Therefore, we argue that radial correlations and integrated relativistic terms need to be taken into account when forecasting the constraining power of future large-scale number counts of galaxy surveys.
Conformal cosmological model and SNe Ia data
International Nuclear Information System (INIS)
Zakharov, A. F.; Pervushin, V. N.
2012-01-01
Now there is a huge scientific activity in astrophysical studies and cosmological ones in particular. Cosmology transforms from a pure theoretical branch of science into an observational one. All the cosmological models have to pass observational tests. The supernovae type Ia (SNe Ia) test is among the most important ones. If one applies the test to determine parameters of the standard Friedmann-Robertson-Walker cosmological model one can conclude that observations lead to the discovery of the dominance of the Λ term and as a result to an acceleration of the Universe. However, there are big mysteries connected with an origin and an essence of dark matter (DM) and the Λ term or dark energy (DE). Alternative theories of gravitation are treated as a possible solution of DM and DE puzzles. The conformal cosmological approach is one of possible alternatives to the standard ΛCDM model. As it was noted several years ago, in the framework of the conformal cosmological approach an introduction of a rigid matter can explain observational data without Λ term (or dark energy). We confirm the claim with much larger set of observational data.
How does pressure gravitate? Cosmological constant problem confronts observational cosmology
Narimani, Ali; Afshordi, Niayesh; Scott, Douglas
2014-08-01
An important and long-standing puzzle in the history of modern physics is the gross inconsistency between theoretical expectations and cosmological observations of the vacuum energy density, by at least 60 orders of magnitude, otherwise known as the cosmological constant problem. A characteristic feature of vacuum energy is that it has a pressure with the same amplitude, but opposite sign to its energy density, while all the precision tests of General Relativity are either in vacuum, or for media with negligible pressure. Therefore, one may wonder whether an anomalous coupling to pressure might be responsible for decoupling vacuum from gravity. We test this possibility in the context of the Gravitational Aether proposal, using current cosmological observations, which probe the gravity of relativistic pressure in the radiation era. Interestingly, we find that the best fit for anomalous pressure coupling is about half-way between General Relativity (GR), and Gravitational Aether (GA), if we include Planck together with WMAP and BICEP2 polarization cosmic microwave background (CMB) observations. Taken at face value, this data combination excludes both GR and GA at around the 3 σ level. However, including higher resolution CMB observations (``highL'') or baryonic acoustic oscillations (BAO) pushes the best fit closer to GR, excluding the Gravitational Aether solution to the cosmological constant problem at the 4- 5 σ level. This constraint effectively places a limit on the anomalous coupling to pressure in the parametrized post-Newtonian (PPN) expansion, ζ4 = 0.105 ± 0.049 (+highL CMB), or ζ4 = 0.066 ± 0.039 (+BAO). These represent the most precise measurement of this parameter to date, indicating a mild tension with GR (for ΛCDM including tensors, with 0ζ4=), and also among different data sets.
How does pressure gravitate? Cosmological constant problem confronts observational cosmology
International Nuclear Information System (INIS)
Narimani, Ali; Scott, Douglas; Afshordi, Niayesh
2014-01-01
An important and long-standing puzzle in the history of modern physics is the gross inconsistency between theoretical expectations and cosmological observations of the vacuum energy density, by at least 60 orders of magnitude, otherwise known as the cosmological constant problem. A characteristic feature of vacuum energy is that it has a pressure with the same amplitude, but opposite sign to its energy density, while all the precision tests of General Relativity are either in vacuum, or for media with negligible pressure. Therefore, one may wonder whether an anomalous coupling to pressure might be responsible for decoupling vacuum from gravity. We test this possibility in the context of the Gravitational Aether proposal, using current cosmological observations, which probe the gravity of relativistic pressure in the radiation era. Interestingly, we find that the best fit for anomalous pressure coupling is about half-way between General Relativity (GR), and Gravitational Aether (GA), if we include Planck together with WMAP and BICEP2 polarization cosmic microwave background (CMB) observations. Taken at face value, this data combination excludes both GR and GA at around the 3 σ level. However, including higher resolution CMB observations (''highL'') or baryonic acoustic oscillations (BAO) pushes the best fit closer to GR, excluding the Gravitational Aether solution to the cosmological constant problem at the 4- 5 σ level. This constraint effectively places a limit on the anomalous coupling to pressure in the parametrized post-Newtonian (PPN) expansion, ζ 4 = 0.105 ± 0.049 (+highL CMB), or ζ 4 = 0.066 ± 0.039 (+BAO). These represent the most precise measurement of this parameter to date, indicating a mild tension with GR (for ΛCDM including tensors, with 0ζ 4 =), and also among different data sets
Parameter Sensitivity of High–Order Equivalent Circuit Models Of Turbine Generator
Directory of Open Access Journals (Sweden)
T. Niewierowicz–Swiecicka
2010-01-01
Full Text Available This work shows the results of a parametric sensitivity analysis applied to a state–space representation of high–order two–axis equivalent circuits (ECs of a turbo generator (150 MVA, 120 MW, 13.8 kV y 50 Hz. The main purpose of this study is to evaluate each parameter impact on the transient response of the analyzed two–axis models –d–axis ECs with one to five damper branches and q–axis ECs from one to four damper branches–. The parametric sensitivity concept is formulated in a general context and the sensibility function is established from the generator response to a short circuit condition. Results ponder the importance played by each parameter in the model behavior. The algorithms were design within MATLAB® environment. The study gives way to conclusions on electromagnetic aspects of solid rotor synchronous generators that have not been previously studied. The methodology presented here can be applied to any other physical system.
Remark on application of the Banach metric method to cosmology
International Nuclear Information System (INIS)
Szydlowski, M.; Heller, M.
1982-01-01
If the cosmological equations can be reduced to the form of a dynamic system, the space of all their solutions is a Banach space. The influence of different parameters on the dynamics of the world models can be easily studied by means of the Banach metric. The method is tested for the Friedman cosmological models perturbed by the bulk viscosity. (author)
International Nuclear Information System (INIS)
Copeland, Edmund J.; Padilla, Antonio; Saffin, Paul M.
2012-01-01
We have recently proposed a novel self tuning mechanism to alleviate the famous cosmological constant problem, based on the general scalar tensor theory proposed by Horndeski. The self-tuning model ends up consisting of four geometric terms in the action, with each term containing a free potential function of the scalar field; the four together being labeled as the Fab-Four. In this paper we begin the important task of deriving the cosmology associated with the Fab-Four Lagrangian. Performing a phase plane analysis of the system we are able to obtain a number of fixed points for the system, with some remarkable new solutions emerging from the trade-off between the various potentials. As well as obtaining inflationary solutions we also find conventional radiation/matter-like solutions, but in regimes where the energy density is dominated by a cosmological constant, and where we do not have any explicit forms of radiation or matter. Stability conditions for matter solutions are obtained and we show how it is possible for there to exist an extended period of 'matter domination' opening up the possibility that we can generate cosmological structures, and recover a consistent cosmology even in the presence of a large cosmological constant
International Nuclear Information System (INIS)
Luo Weixi; Zeng Zhengzhong; Lei Tianshi; Wang Liangping; Hu Yixiang; Sun Tieping; Huang Tao
2012-01-01
The plasma source (cable guns) of the plasma opening switch (POS) on Qiangguang Ⅰ generator was chosen as the study object. The plasma source performance was investigated by using charge collectors. Experimental results show that the plasma ejection density is positively correlated with the structural parameter, the distance between gun core tip and muzzle plane, and the plasma ejection velocity is negatively correlated with the parameter. The increasing rate of plasma ejection density is less than that of drive current. As far as a plasma source with tens of cable plasma guns is concerned, the influence of single cable gun's discharge dispersancy on plasma uniformity is little. Analysis of uncertainty shows that the uncertainty of measurement can be reduced by increasing the number of experiments and averaging the results. The combined standard uncertainty of plasma ejection density is less than 10%. (authors)
Atmospheric and Fundamental Parameters of Stars in Hubble's Next Generation Spectral Library
Heap, Sally
2010-01-01
Hubble's Next Generation Spectral Library (NGSL) consists of R approximately 1000 spectra of 374 stars of assorted temperature, gravity, and metallicity. We are presently working to determine the atmospheric and fundamental parameters of the stars from the NGSL spectra themselves via full-spectrum fitting of model spectra to the observed (extinction-corrected) spectrum over the full wavelength range, 0.2-1.0 micron. We use two grids of model spectra for this purpose: the very low-resolution spectral grid from Castelli-Kurucz (2004), and the grid from MARCS (2008). Both the observed spectrum and the MARCS spectra are first degraded in resolution to match the very low resolution of the Castelli-Kurucz models, so that our fitting technique is the same for both model grids. We will present our preliminary results with a comparison with those from the Sloan/Segue Stellar Parameter Pipeline, ELODIE, and MILES, etc.
Parameter optimization of differential evolution algorithm for automatic playlist generation problem
Alamag, Kaye Melina Natividad B.; Addawe, Joel M.
2017-11-01
With the digitalization of music, the number of collection of music increased largely and there is a need to create lists of music that filter the collection according to user preferences, thus giving rise to the Automatic Playlist Generation Problem (APGP). Previous attempts to solve this problem include the use of search and optimization algorithms. If a music database is very large, the algorithm to be used must be able to search the lists thoroughly taking into account the quality of the playlist given a set of user constraints. In this paper we perform an evolutionary meta-heuristic optimization algorithm, Differential Evolution (DE) using different combination of parameter values and select the best performing set when used to solve four standard test functions. Performance of the proposed algorithm is then compared with normal Genetic Algorithm (GA) and a hybrid GA with Tabu Search. Numerical simulations are carried out to show better results from Differential Evolution approach with the optimized parameter values.
Fluid observers and tilting cosmology
International Nuclear Information System (INIS)
Coley, A A; Hervik, S; Lim, W C
2006-01-01
We study perfect fluid cosmological models with a constant equation of state parameter γ in which there are two naturally defined timelike congruences, a geometrically defined geodesic congruence and a non-geodesic fluid congruence. We establish an appropriate set of boost formulae relating the physical variables, and consequently the observed quantities, in the two frames. We study expanding spatially homogeneous tilted perfect fluid models, with an emphasis on future evolution with extreme tilt. We show that for ultra-radiative equations of state (i.e. γ > 4/3), generically the tilt becomes extreme at late times and the fluid observers will reach infinite expansion within a finite proper time and experience a singularity similar to that of the big rip. In addition, we show that for sub-radiative equations of state (i.e. γ < 4/3), the tilt can become extreme at late times and give rise to an effective quintessential equation of state. To establish the connection with phantom cosmology and quintessence, we calculate the effective equation of state in the models under consideration and we determine the future asymptotic behaviour of the tilting models in the fluid frame variables using the boost formulae. We also discuss spatially inhomogeneous models and tilting spatially homogeneous models with a cosmological constant
Cosmological aspects of spontaneous baryogenesis
Energy Technology Data Exchange (ETDEWEB)
Simone, Andrea De; Kobayashi, Takeshi [SISSA,Via Bonomea 265, 34136 Trieste (Italy); INFN, Sezione di Trieste,Via Bonomea 265, 34136 Trieste (Italy)
2016-08-24
We investigate cosmological aspects of spontaneous baryogenesis driven by a scalar field, and present general constraints that are independent of the particle physics model. The relevant constraints are obtained by studying the backreaction of the produced baryons on the scalar field, the cosmological expansion history after baryogenesis, and the baryon isocurvature perturbations. We show that cosmological considerations alone provide powerful constraints, especially for the minimal scenario with a quadratic scalar potential. Intriguingly, we find that for a given inflation scale, the other parameters including the reheat temperature, decoupling temperature of the baryon violating interactions, and the mass and decay constant of the scalar are restricted to lie within ranges of at most a few orders of magnitude. We also discuss possible extensions to the minimal setup, and propose two ideas for evading constraints on isocurvature perturbations: one is to suppress the baryon isocurvature with nonquadratic scalar potentials, another is to compensate the baryon isocurvature with cold dark matter isocurvature by making the scalar survive until the present.
Methods of Generating Key Sequences Based on Parameters of Handwritten Passwords and Signatures
Directory of Open Access Journals (Sweden)
Pavel Lozhnikov
2016-10-01
Full Text Available The modern encryption methods are reliable if strong keys (passwords are used, but the human factor issue cannot be solved by cryptographic methods. The best variant is binding all authenticators (passwords, encryption keys, and others to the identities. When a user is authenticated by biometrical characteristics, the problem of protecting a biometrical template stored on a remote server becomes a concern. The paper proposes several methods of generating keys (passwords by means of the fuzzy extractors method based on signature parameters without storing templates in an open way.
Classification of cosmology with arbitrary matter in the Horava-Lifshitz model
International Nuclear Information System (INIS)
Minamitsuji, Masato
2010-01-01
In this work, we discuss the cosmological evolutions in the nonrelativistic and possibly renormalizable gravitational theory, called the Horava-Lifshitz (HL) theory. We consider the original HL model (type I), and the modified version obtained by an analytic continuation of parameters (type II). We classify the possible cosmological evolutions with arbitrary matter. We will find a variety of cosmology.
Cosmology with primordial black holes
International Nuclear Information System (INIS)
Lindley, D.
1981-09-01
Cosmologies containing a substantial amount of matter in the form of evaporating primordial black holes are investigated. A review of constraints on the numbers of such black holes, including an analysis of a new limit found by looking at the destruction of deuterium by high energy photons, shows that there must be a negligible population of small black holes from the era of cosmological nucleosynthesis onwards, but that there are no strong constraints before this time. The major part of the work is based on the construction of detailed, self-consistent cosmological models in which black holes are continually forming and evaporating The interest in these models centres on the question of baryon generation, which occurs via the asymmetric decay of a new type of particle which appears as a consequence of the recently developed Grand Unified Theories of elementary particles. Unfortunately, there is so much uncertainty in the models that firm conclusions are difficult to reach; however, it seems feasible in principle that primordial black holes could be responsible for a significant part of the present matter density of the Universe. (author)
Cosmological implications of modified gravity induced by quantum metric fluctuations
Energy Technology Data Exchange (ETDEWEB)
Liu, Xing [Sun Yat-Sen University, School of Physics, Guangzhou (China); Sun Yat-Sen University, Yat Sen School, Guangzhou (China); Harko, Tiberiu [Babes-Bolyai University, Department of Physics, Cluj-Napoca (Romania); University College London, Department of Mathematics, London (United Kingdom); Liang, Shi-Dong [Sun Yat-Sen University, School of Physics, Guangzhou (China); Sun Yat-Sen University, State Key Laboratory of Optoelectronic Material and Technology, Guangdong Province Key Laboratory of Display Material and Technology, School of Physics, Guangzhou (China)
2016-08-15
We investigate the cosmological implications of modified gravities induced by the quantum fluctuations of the gravitational metric. If the metric can be decomposed as the sum of the classical and of a fluctuating part, of quantum origin, then the corresponding Einstein quantum gravity generates at the classical level modified gravity models with a non-minimal coupling between geometry and matter. As a first step in our study, after assuming that the expectation value of the quantum correction can be generally expressed in terms of an arbitrary second order tensor constructed from the metric and from the thermodynamic quantities characterizing the matter content of the Universe, we derive the (classical) gravitational field equations in their general form. We analyze in detail the cosmological models obtained by assuming that the quantum correction tensor is given by the coupling of a scalar field and of a scalar function to the metric tensor, and by a term proportional to the matter energy-momentum tensor. For each considered model we obtain the gravitational field equations, and the generalized Friedmann equations for the case of a flat homogeneous and isotropic geometry. In some of these models the divergence of the matter energy-momentum tensor is non-zero, indicating a process of matter creation, which corresponds to an irreversible energy flow from the gravitational field to the matter fluid, and which is direct consequence of the non-minimal curvature-matter coupling. The cosmological evolution equations of these modified gravity models induced by the quantum fluctuations of the metric are investigated in detail by using both analytical and numerical methods, and it is shown that a large variety of cosmological models can be constructed, which, depending on the numerical values of the model parameters, can exhibit both accelerating and decelerating behaviors. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Verde, Licia; Jimenez, Raul [Institute of Cosmos Sciences, University of Barcelona, IEEC-UB, Martí Franquès, 1, E08028 Barcelona (Spain); Bellini, Emilio [University of Oxford, Denys Wilkinson Building, Keble Road, Oxford, OX1 3RH (United Kingdom); Pigozzo, Cassio [Instituto de Física, Universidade Federal da Bahia, Salvador, BA (Brazil); Heavens, Alan F., E-mail: liciaverde@icc.ub.edu, E-mail: emilio.bellini@physics.ox.ac.uk, E-mail: cpigozzo@ufba.br, E-mail: a.heavens@imperial.ac.uk, E-mail: raul.jimenez@icc.ub.edu [Imperial Centre for Inference and Cosmology (ICIC), Imperial College, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom)
2017-04-01
We investigate our knowledge of early universe cosmology by exploring how much additional energy density can be placed in different components beyond those in the ΛCDM model. To do this we use a method to separate early- and late-universe information enclosed in observational data, thus markedly reducing the model-dependency of the conclusions. We find that the 95% credibility regions for extra energy components of the early universe at recombination are: non-accelerating additional fluid density parameter Ω{sub MR} < 0.006 and extra radiation parameterised as extra effective neutrino species 2.3 < N {sub eff} < 3.2 when imposing flatness. Our constraints thus show that even when analyzing the data in this largely model-independent way, the possibility of hiding extra energy components beyond ΛCDM in the early universe is seriously constrained by current observations. We also find that the standard ruler, the sound horizon at radiation drag, can be well determined in a way that does not depend on late-time Universe assumptions, but depends strongly on early-time physics and in particular on additional components that behave like radiation. We find that the standard ruler length determined in this way is r {sub s} = 147.4 ± 0.7 Mpc if the radiation and neutrino components are standard, but the uncertainty increases by an order of magnitude when non-standard dark radiation components are allowed, to r {sub s} = 150 ± 5 Mpc.
Cosmology with exponential potentials
International Nuclear Information System (INIS)
Kehagias, Alex; Kofinas, Georgios
2004-01-01
We examine in the context of general relativity the dynamics of a spatially flat Robertson-Walker universe filled with a classical minimally coupled scalar field φ of exponential potential V(φ) ∼ exp(-μφ) plus pressureless baryonic matter. This system is reduced to a first-order ordinary differential equation for Ω φ (w φ ) or q(w φ ), providing direct evidence on the acceleration/deceleration properties of the system. As a consequence, for positive potentials, passage into acceleration not at late times is generically a feature of the system for any value of μ, even when the late-times attractors are decelerating. Furthermore, the structure formation bound, together with the constraints Ω m0 ∼ 0.25 - 0.3, -1 ≤ w φ0 ≤ -0.6, provides, independently of initial conditions and other parameters, the necessary condition 0 N , while the less conservative constraint -1 ≤ w φ ≤ -0.93 gives 0 N . Special solutions are found to possess intervals of acceleration. For the almost cosmological constant case w φ ∼ -1, the general relation Ω φ (w φ ) is obtained. The generic (nonlinearized) late-times solution of the system in the plane (w φ , Ω φ ) or (w φ , q) is also derived
Cosmological helium production simplified
International Nuclear Information System (INIS)
Bernstein, J.; Brown, L.S.; Feinberg, G.
1988-01-01
We present a simplified model of helium synthesis in the early universe. The purpose of the model is to explain clearly the physical ideas relevant to the cosmological helium synthesis, in a manner that does not overlay these ideas with complex computer calculations. The model closely follows the standard calculation, except that it neglects the small effect of Fermi-Dirac statistics for the leptons. We also neglect the temperature difference between photons and neutrinos during the period in which neutrons and protons interconvert. These approximations allow us to express the neutron-proton conversion rates in a closed form, which agrees to 10% accuracy or better with the exact rates. Using these analytic expressions for the rates, we reduce the calculation of the neutron-proton ratio as a function of temperature to a simple numerical integral. We also estimate the effect of neutron decay on the helium abundance. Our result for this quantity agrees well with precise computer calculations. We use our semi-analytic formulas to determine how the predicted helium abundance varies with such parameters as the neutron life-time, the baryon to photon ratio, the number of neutrino species, and a possible electron-neutrino chemical potential. 19 refs., 1 fig., 1 tab
Neutrino properties from cosmology
DEFF Research Database (Denmark)
Hannestad, S.
2013-01-01
In recent years precision cosmology has become an increasingly powerful probe of particle physics. Perhaps the prime example of this is the very stringent cosmological upper bound on the neutrino mass. However, other aspects of neutrino physics, such as their decoupling history and possible non......-standard interactions, can also be probed using observations of cosmic structure. Here, I review the current status of cosmological bounds on neutrino properties and discuss the potential of future observations, for example by the recently approved EUCLID mission, to precisely measure neutrino properties....
Cosmology and particle physics
Energy Technology Data Exchange (ETDEWEB)
Steigman, G [California Univ., Santa Barbara (USA). Inst. for Theoretical Physics; Bartol Research Foundation, Newark, Delaware (USA))
1982-01-29
The cosmic connections between physics on the very largest and very smallest scales are reviewed with an emphasis on the symbiotic relation between elementary particle physics and cosmology. After a review of the early Universe as a cosmic accelerator, various cosmological and astrophysical constraints on models of particle physics are outlined. To illustrate this approach to particle physics via cosmology, reference is made to several areas of current research: baryon non-conservation and baryon asymmetry; free quarks, heavy hadrons and other exotic relics; primordial nucleosynthesis and neutrino masses.
Neutrino properties from cosmology
CERN. Geneva
2013-01-01
Future, massive large-scale structure survey have been presented and approved.On the theory side, a significant effort has bene devoted to achieve better modeling of small scale clustering that is of cosmological non-linearities. As a result it has become clear that forthcoming cosmological data have enough statitsical power to detect the effect of non-zero neutrino mass (even at the lower mass scale limit imposed by oscillations) and to constrain the absolute neutrino mass scale.Cosmological data can also constrain the numb...
International Nuclear Information System (INIS)
Elghool, Ali; Basrawi, Firdaus; Ibrahim, Thamir Khalil; Habib, Khairul; Ibrahim, Hassan; Idris, Daing Mohamad Nafiz Daing
2017-01-01
Highlights: • Coupling a thermoelectric power generation (TEG) to a heat sink is presented. • Review the classifications and parameters affecting performance of the TEG with heat sink. • Discuss different mathematical models of the heat sinks. • The passive heat sinks are most appropriate because of the inherent efficiency of TEG. • Medium temperature range below 300 °C is found to be most suitable for HPHS. - Abstract: In recent years, there have been growing interests in key areas related to global warming resulting from environmental emissions, and the diminishing sources of fossil fuel. The increased interest has led to significant research efforts towards finding novel technologies in clean energy production. Consequently, the merits of a thermo-electric generator (TEG) have promised a revival of alternative means of producing green energy. It is, however, impractical to account for the cost of thermal energy input to the TEG which is in the form of final waste heat. This is because the technology presents critical limitations in determining its cost efficiency nor its economic disadvantages. This paper reviews the principles of thermo-electric power production, as well the materials use, performance achieved, and application areas. The paper also takes a particular deliberation on TEG heat sinks geometries and categories. The review emphasizes more on the TEG performance while considering a number of heat sink parameters related to its performance.
Determination of tritium generation and release parameters at lithium CPS under neutron irradiation
Energy Technology Data Exchange (ETDEWEB)
Ponkratov, Yuriy, E-mail: ponkratov@nnc.kz [Institute of Atomic Energy, National Nuclear Center of RK, Kurchatov (Kazakhstan); Baklanov, Viktor; Skakov, Mazhyn; Kulsartov, Timur; Tazhibayeva, Irina; Gordienko, Yuriy; Zaurbekova, Zhanna; Tulubayev, Yevgeniy [Institute of Atomic Energy, National Nuclear Center of RK, Kurchatov (Kazakhstan); Chikhray, Yevgeniy [Institute of Experimental and Theoretical Physics of Kazakh National University, Almaty (Kazakhstan); Lyublinski, Igor [JSC “Star”, Moscow (Russian Federation); NRNU “MEPhI”, Moscow (Russian Federation); Vertkov, Alexey [JSC “Star”, Moscow (Russian Federation)
2016-11-01
Highlights: • The main parameters of tritium generation and release from lithium capillary-porous system (CPS) under neutron irradiation at the IVG.1 M research reactor is described in paper. • In the experiments a very small tritium release was fixed likely due to its high solubility in liquid lithium. • If the lithium CPS will be used as a plasma facing material in temperature range up to 773 K under neutron irradiation only helium will release from lithium CPS into a vacuum chamber. - Abstract: This paper describes the main parameters of tritium generation and release from lithium capillary-porous system (CPS) under neutron irradiation at the IVG.1 M research reactor. The experiments were carried out using the method of mass-spectrometric registration of released gases and using a specially constructed ampoule device. Irradiation was carried out at different reactor thermal powers (1, 2 and 6 MW) and sample temperatures from 473 to 773 K. In the experiments a very small tritium release was detected likely due to its high solubility in liquid lithium. It can be caused by formation of lithium tritide during tritium diffusion to the lithium surface.
Directory of Open Access Journals (Sweden)
Wei Dong
2015-02-01
Full Text Available In this paper, a quadrotor test bed is developed. The technical approach for this test bed is firstly proposed by utilizing a commercial quadrotor, a Vicon motion capture system and a ground station. Then, the mathematical model of the quadrotor is formulated considering aerodynamic effects, and the parameter identification approaches for this model are provided accordingly. Based on the developed model and identified parameters, a simulation environment that is consistent with the real system is developed. Subsequently, a flight control strategy and a trajectory generation method, both of which are conceptually and computationally lightweight, are developed and tested in the simulation environment. The developed algorithms are then directly transplanted to the real system, and the experimental results show that their responses in the real-time flights match well with those from the simulations. This indicates that the control algorithms developed for the quadrotor can be preliminarily verified and refined though simulations, and then directly implemented to the real system, which could significantly reduce the experimental risks and costs. Meanwhile, real-time experiments show that the developed flight controller can efficiently stabilize the quadrotor when external disturbances exist, and the trajectory generation approach can provide safe guidance for the quadrotor to fly smoothly through cluttered environments with obstacle rings. All of these features are valuable for real applications, thus demonstrating the feasibility of further development.
Optimization of Shielding- Collimator Parameters for ING-27 Neutron Generator Using MCNP5
Directory of Open Access Journals (Sweden)
Hegazy Aya Hamdy
2018-01-01
Full Text Available Neutron generators are now used in various fields. They produce only fast neutrons; D-D neutron generator produces 2.45 MeV neutrons and D-T produces 14.1 MeV neutrons. In order to optimize shielding-collimator parameters to achieve higher neutron flux at the investigated sample (The signal with lower neutron and gamma rays flux at the area of the detectors, design iterations are widely used. This work was applied to ROMASHA setup, TANGRA project, FLNP, Joint Institute for Nuclear Research. The studied parameters were; (1 shielding-collimator material, (2 Distance between the shielding-collimator assembly first plate and center of the neutron beam, and (3 thickness of collimator sheets. MCNP5 was used to simulate ROMASHA setup after it was validated on the experimental results of irradiation of Carbon-12 sample for one hour to detect its 4.44 MeV characteristic gamma line. The ratio between the signal and total neutron flux that enters each detector was calculated and plotted, concluding that the optimum shielding-collimator assembly is Tungsten of 5 cm thickness for each plate, and a distance of 2.3 cm. Also, the ratio between the signal and total gamma rays flux was calculated and plotted for each detector, leading to the previous conclusion but the distance was 1 cm.
Optimization of Shielding- Collimator Parameters for ING-27 Neutron Generator Using MCNP5
Hegazy, Aya Hamdy; Skoy, V. R.; Hossny, K.
2018-04-01
Neutron generators are now used in various fields. They produce only fast neutrons; D-D neutron generator produces 2.45 MeV neutrons and D-T produces 14.1 MeV neutrons. In order to optimize shielding-collimator parameters to achieve higher neutron flux at the investigated sample (The signal) with lower neutron and gamma rays flux at the area of the detectors, design iterations are widely used. This work was applied to ROMASHA setup, TANGRA project, FLNP, Joint Institute for Nuclear Research. The studied parameters were; (1) shielding-collimator material, (2) Distance between the shielding-collimator assembly first plate and center of the neutron beam, and (3) thickness of collimator sheets. MCNP5 was used to simulate ROMASHA setup after it was validated on the experimental results of irradiation of Carbon-12 sample for one hour to detect its 4.44 MeV characteristic gamma line. The ratio between the signal and total neutron flux that enters each detector was calculated and plotted, concluding that the optimum shielding-collimator assembly is Tungsten of 5 cm thickness for each plate, and a distance of 2.3 cm. Also, the ratio between the signal and total gamma rays flux was calculated and plotted for each detector, leading to the previous conclusion but the distance was 1 cm.
Directory of Open Access Journals (Sweden)
Mohammd Mohammed S.
2015-01-01
Full Text Available The aim of this work is to develop a method for optimization of operating parameters of a triple pressure heat recovery steam generator. Two types of optimization: (a thermodynamic and (b thermoeconomic were preformed. The purpose of the thermodynamic optimization is to maximize the efficiency of the plant. The selected objective for this purpose is minimization of the exergy destruction in the heat recovery steam generator (HRSG. The purpose of the thermoeconomic optimization is to decrease the production cost of electricity. Here, the total annual cost of HRSG, defined as a sum of annual values of the capital costs and the cost of the exergy destruction, is selected as the objective function. The optimal values of the most influencing variables are obtained by minimizing the objective function while satisfying a group of constraints. The optimization algorithm is developed and tested on a case of CCGT plant with complex configuration. Six operating parameters were subject of optimization: pressures and pinch point temperatures of every three (high, intermediate and low pressure steam stream in the HRSG. The influence of these variables on the objective function and production cost are investigated in detail. The differences between results of thermodynamic and the thermoeconomic optimization are discussed.
Spectral Properties, Generation Order Parameters, and Luminosities for Spin-powered X-Ray Pulsars
Wang, Wei; Zhao, Yongheng
2004-02-01
We show the spectral properties of 15 spin-powered X-ray pulsars, and the correlation between the average power-law photon index and spin-down rate. Generation order parameters (GOPs) based on polar cap models are introduced to characterize the X-ray pulsars. We calculate three definitions of generation order parameters arising from the different effects of magnetic and electric fields on photon absorption during cascade processes, and study the relations between the GOPs and spectral properties of X-ray pulsars. There exists a possible correlation between the photon index and GOP in our pulsar sample. Furthermore, we present a method stemming from the concept of GOPs to estimate the nonthermal X-ray luminosity for spin-powered pulsars. Then X-ray luminosity is calculated in the context of our polar cap accelerator model, which is consistent with most observed X-ray pulsar data. The ratio between the X-ray luminosity estimated by our method and the pulsar's spin-down power is consistent with the LX~10-3Lsd feature.
Entropy, matter, and cosmology.
Prigogine, I; Géhéniau, J
1986-09-01
The role of irreversible processes corresponding to creation of matter in general relativity is investigated. The use of Landau-Lifshitz pseudotensors together with conformal (Minkowski) coordinates suggests that this creation took place in the early universe at the stage of the variation of the conformal factor. The entropy production in this creation process is calculated. It is shown that these dissipative processes lead to the possibility of cosmological models that start from empty conditions and gradually build up matter and entropy. Gravitational entropy takes a simple meaning as associated to the entropy that is necessary to produce matter. This leads to an extension of the third law of thermodynamics, as now the zero point of entropy becomes the space-time structure out of which matter is generated. The theory can be put into a convenient form using a supplementary "C" field in Einstein's field equations. The role of the C field is to express the coupling between gravitation and matter leading to irreversible entropy production.
Introduction to particle cosmology the standard model of cosmology and its open problems
Bambi, Cosimo
2016-01-01
This book introduces the basic concepts of particle cosmology and covers all the main aspects of the Big Bang Model (expansion of the Universe, Big Bang Nucleosynthesis, Cosmic Microwave Background, large scale structures) and the search for new physics (inflation, baryogenesis, dark matter, dark energy). It also includes the majority of recent discoveries, such as the precise determination of cosmological parameters using experiments like WMAP and Planck, the discovery of the Higgs boson at LHC, the non-discovery to date of supersymmetric particles, and the search for the imprint of gravitational waves on the CMB polarization by Planck and BICEP. This textbook is based on the authors’ courses on Cosmology, and aims at introducing Particle Cosmology to senior undergraduate and graduate students. It has been especially written to be accessible even for those students who do not have a strong background in General Relativity and quantum field theory. The content of this book is organized in an easy-to-use ...
Model of cosmology and particle physics at an intermediate scale
International Nuclear Information System (INIS)
Bastero-Gil, M.; Di Clemente, V.; King, S. F.
2005-01-01
We propose a model of cosmology and particle physics in which all relevant scales arise in a natural way from an intermediate string scale. We are led to assign the string scale to the intermediate scale M * ∼10 13 GeV by four independent pieces of physics: electroweak symmetry breaking; the μ parameter; the axion scale; and the neutrino mass scale. The model involves hybrid inflation with the waterfall field N being responsible for generating the μ term, the right-handed neutrino mass scale, and the Peccei-Quinn symmetry breaking scale. The large scale structure of the Universe is generated by the lightest right-handed sneutrino playing the role of a coupled curvaton. We show that the correct curvature perturbations may be successfully generated providing the lightest right-handed neutrino is weakly coupled in the seesaw mechanism, consistent with sequential dominance
The cosmological constant problem
International Nuclear Information System (INIS)
Dolgov, A.D.
1989-05-01
A review of the cosmological term problem is presented. Baby universe model and the compensating field model are discussed. The importance of more accurate data on the Hubble constant and the Universe age is stressed. 18 refs
Time in contemporary cosmology
International Nuclear Information System (INIS)
Mavrides, Stamatia
1980-01-01
Cosmological time is defined, as is coordinated universal time against local times of special relativity. The problems of time and matter, age of the universe, Goedel models, arrow of time, are also discussed [fr
International Nuclear Information System (INIS)
Coule, D H
2005-01-01
We contrast the initial condition requirements of various contemporary cosmological models including inflationary and bouncing cosmologies. Canonical quantization of general relativity is used, as a first approximation to full quantum gravity, to determine whether suitable initial conditions are present. Various proposals such as Hartle-Hawking's 'no boundary' or tunnelling boundary conditions are assessed on grounds of naturalness and fine tuning. Alternatively, a quiescent initial state or an initial closed timelike curve 'time machine' is considered. Possible extensions to brane models are also addressed. Further ideas about universe creation from a meta-universe are outlined. Semiclassical and time asymmetry requirements of cosmology are briefly discussed and contrasted with the black-hole final-state proposal. We compare the recent loop quantum cosmology of Bojowald and co-workers with these earlier schemes. A number of possible difficulties and limitations are outlined. (topical review)
International Nuclear Information System (INIS)
Turner, Michael S.
1999-01-01
For two decades the hot big-bang model as been referred to as the standard cosmology - and for good reason. For just as long cosmologists have known that there are fundamental questions that are not answered by the standard cosmology and point to a grander theory. The best candidate for that grander theory is inflation + cold dark matter. It holds that the Universe is flat, that slowly moving elementary particles left over from the earliest moments provide the cosmic infrastructure, and that the primeval density inhomogeneities that seed all the structure arose from quantum fluctuations. There is now prima facie evidence that supports two basic tenets of this paradigm. An avalanche of high-quality cosmological observations will soon make this case stronger or will break it. Key questions remain to be answered; foremost among them are: identification and detection of the cold dark matter particles and elucidation of the dark-energy component. These are exciting times in cosmology!
International Nuclear Information System (INIS)
Senjanovic, G.; Virginia Polytechnic Inst. and State Univ., Blacksburg
1984-07-01
Extended supersymmetry, Kaluza-Klein theory and family unification all suggest the existence of mirror fermions, with same quantum numbers but opposite helicities from ordinary fermions. The laboratory and especially cosmological implications of such particles are reviewed and summarized. (author)
Lachieze-Rey, Marc
This book delivers a quantitative account of the science of cosmology, designed for a non-specialist audience. The basic principles are outlined using simple maths and physics, while still providing rigorous models of the Universe. It offers an ideal introduction to the key ideas in cosmology, without going into technical details. The approach used is based on the fundamental ideas of general relativity such as the spacetime interval, comoving coordinates, and spacetime curvature. It provides an up-to-date and thoughtful discussion of the big bang, and the crucial questions of structure and galaxy formation. Questions of method and philosophical approaches in cosmology are also briefly discussed. Advanced undergraduates in either physics or mathematics would benefit greatly from use either as a course text or as a supplementary guide to cosmology courses.
Ryden, Barbara
2017-01-01
This second edition of Introduction to Cosmology is an exciting update of an award-winning textbook. It is aimed primarily at advanced undergraduate students in physics and astronomy, but is also useful as a supplementary text at higher levels. It explains modern cosmological concepts, such as dark energy, in the context of the Big Bang theory. Its clear, lucid writing style, with a wealth of useful everyday analogies, makes it exceptionally engaging. Emphasis is placed on the links between theoretical concepts of cosmology and the observable properties of the universe, building deeper physical insights in the reader. The second edition includes recent observational results, fuller descriptions of special and general relativity, expanded discussions of dark energy, and a new chapter on baryonic matter that makes up stars and galaxies. It is an ideal textbook for the era of precision cosmology in the accelerating universe.
Tensors, relativity, and cosmology
Dalarsson, Mirjana
2015-01-01
Tensors, Relativity, and Cosmology, Second Edition, combines relativity, astrophysics, and cosmology in a single volume, providing a simplified introduction to each subject that is followed by detailed mathematical derivations. The book includes a section on general relativity that gives the case for a curved space-time, presents the mathematical background (tensor calculus, Riemannian geometry), discusses the Einstein equation and its solutions (including black holes and Penrose processes), and considers the energy-momentum tensor for various solutions. In addition, a section on relativistic astrophysics discusses stellar contraction and collapse, neutron stars and their equations of state, black holes, and accretion onto collapsed objects, with a final section on cosmology discussing cosmological models, observational tests, and scenarios for the early universe. This fully revised and updated second edition includes new material on relativistic effects, such as the behavior of clocks and measuring rods in m...
International Nuclear Information System (INIS)
Bacchetta, Alessandro; Jung, Hannes; Kutak, Krzysztof
2010-02-01
A method for tuning parameters in Monte Carlo generators is described and applied to a specific case. The method works in the following way: each observable is generated several times using different values of the parameters to be tuned. The output is then approximated by some analytic form to describe the dependence of the observables on the parameters. This approximation is used to find the values of the parameter that give the best description of the experimental data. This results in significantly faster fitting compared to an approach in which the generator is called iteratively. As an application, we employ this method to fit the parameters of the unintegrated gluon density used in the Cascade Monte Carlo generator, using inclusive deep inelastic data measured by the H1 Collaboration. We discuss the results of the fit, its limitations, and its strong points. (orig.)
Top ten accelerating cosmological models
International Nuclear Information System (INIS)
Szydlowski, Marek; Kurek, Aleksandra; Krawiec, Adam
2006-01-01
Recent astronomical observations indicate that the Universe is presently almost flat and undergoing a period of accelerated expansion. Basing on Einstein's general relativity all these observations can be explained by the hypothesis of a dark energy component in addition to cold dark matter (CDM). Because the nature of this dark energy is unknown, it was proposed some alternative scenario to explain the current accelerating Universe. The key point of this scenario is to modify the standard FRW equation instead of mysterious dark energy component. The standard approach to constrain model parameters, based on the likelihood method, gives a best-fit model and confidence ranges for those parameters. We always arbitrary choose the set of parameters which define a model which we compare with observational data. Because in the generic case, the introducing of new parameters improves a fit to the data set, there appears the problem of elimination of model parameters which can play an insufficient role. The Bayesian information criteria of model selection (BIC) is dedicated to promotion a set of parameters which should be incorporated to the model. We divide class of all accelerating cosmological models into two groups according to the two types of explanation acceleration of the Universe. Then the Bayesian framework of model selection is used to determine the set of parameters which gives preferred fit to the SNIa data. We find a few of flat cosmological models which can be recommend by the Bayes factor. We show that models with dark energy as a new fluid are favoured over models featuring a modified FRW equation
Magnetohydrodynamics and Plasma Cosmology
Kleidis, Kostas; Kuiroukidis, Apostolos; Papadopoulos, Demetrios; Vlahos, Loukas
2007-09-01
We study the linear magnetohydrodynamic (MHD) equations, both in the Newtonian and the general-relativistic limit, as regards a viscous magnetized fluid of finite conductivity and discuss instability criteria. In addition, we explore the excitation of cosmological perturbations in anisotropic spacetimes, in the presence of an ambient magnetic field. Acoustic, electromagnetic (e/m) and fast-magnetosonic modes, propagating normal to the magnetic field, can be excited, resulting in several implications of cosmological significance.
International Nuclear Information System (INIS)
Novikov, I.D.
1999-01-01
In this talk a brief survey has been carried out on the development of cosmology from the days Leopold Infeld was active in the field up to the present. Attention in particular is paid to the history of our knowledge of Hubble's expansion, of the cosmological constant, of the average density of matter and its distribution, and of the related issue of possible types of matter in the Universe. (author)
Cosmological phase transitions
International Nuclear Information System (INIS)
Kolb, E.W.
1993-10-01
If modern ideas about the role of spontaneous symmetry breaking in fundamental physics are correct, then the Universe should have undergone a series of phase transitions early in its history. The study of cosmological phase transitions has become an important aspect of early-Universe cosmology. In this lecture I review some very recent work on three aspects of phase transitions: the electroweak transition, texture, and axions
Directory of Open Access Journals (Sweden)
Daywitt W. C.
2009-04-01
Full Text Available Both the big-bang and the quasi-steady-state cosmologies originate in some type of Planck state. This paper presents a new cosmological theory based on the Planck- vacuum negative-energy state, a state consisting of a degenerate collection of negative- energy Planck particles. A heuristic look at the Einstein field equation provides a con- vincing argument that such a vacuum state could provide a theoretical explanation for the visible universe.
Cosmology with cosmic microwave background anisotropy
Indian Academy of Sciences (India)
Measurements of CMB anisotropy and, more recently, polarization have played a very important role in allowing precise determination of various parameters of the `standard' cosmological model. The expectation of the paradigm of inflation and the generic prediction of the simplest realization of inflationary scenario in the ...
Cosmological Models and Stability
Andersson, Lars
Principles in the form of heuristic guidelines or generally accepted dogma play an important role in the development of physical theories. In particular, philosophical considerations and principles figure prominently in the work of Albert Einstein. As mentioned in the talk by Jiří Bičák at this conference, Einstein formulated the equivalence principle, an essential step on the road to general relativity, during his time in Prague 1911-1912. In this talk, I would like to discuss some aspects of cosmological models. As cosmology is an area of physics where "principles" such as the "cosmological principle" or the "Copernican principle" play a prominent role in motivating the class of models which form part of the current standard model, I will start by comparing the role of the equivalence principle to that of the principles used in cosmology. I will then briefly describe the standard model of cosmology to give a perspective on some mathematical problems and conjectures on cosmological models, which are discussed in the later part of this paper.
Observable gravitational waves in pre-big bang cosmology: an update
Energy Technology Data Exchange (ETDEWEB)
Gasperini, M., E-mail: gasperini@ba.infn.it [Dipartimento di Fisica, Università di Bari, Via G. Amendola 173, 70126 Bari (Italy)
2016-12-01
In the light of the recent results concerning CMB observations and GW detection we address the question of whether it is possible, in a self-consistent inflationary framework, to simultaneously generate a spectrum of scalar metric perturbations in agreement with Planck data and a stochastic background of primordial gravitational radiation compatible with the design sensitivity of aLIGO/Virgo and/or eLISA. We suggest that this is possible in a string cosmology context, for a wide region of the parameter space of the so-called pre-big bang models. We also discuss the associated values of the tensor-to-scalar ratio relevant to the CMB polarization experiments. We conclude that future, cross-correlated results from CMB observations and GW detectors will be able to confirm or disprove pre-big bang models and—in any case—will impose new significant constraints on the basic string theory/cosmology parameters.
Observable gravitational waves in pre-big bang cosmology: an update
International Nuclear Information System (INIS)
Gasperini, M.
2016-01-01
In the light of the recent results concerning CMB observations and GW detection we address the question of whether it is possible, in a self-consistent inflationary framework, to simultaneously generate a spectrum of scalar metric perturbations in agreement with Planck data and a stochastic background of primordial gravitational radiation compatible with the design sensitivity of aLIGO/Virgo and/or eLISA. We suggest that this is possible in a string cosmology context, for a wide region of the parameter space of the so-called pre-big bang models. We also discuss the associated values of the tensor-to-scalar ratio relevant to the CMB polarization experiments. We conclude that future, cross-correlated results from CMB observations and GW detectors will be able to confirm or disprove pre-big bang models and—in any case—will impose new significant constraints on the basic string theory/cosmology parameters.
BOOK REVIEW: Observational Cosmology Observational Cosmology
Howell, Dale Andrew
2013-04-01
Observational Cosmology by Stephen Serjeant fills a niche that was underserved in the textbook market: an up-to-date, thorough cosmology textbook focused on observations, aimed at advanced undergraduates. Not everything about the book is perfect - some subjects get short shrift, in some cases jargon dominates, and there are too few exercises. Still, on the whole, the book is a welcome addition. For decades, the classic textbooks of cosmology have focused on theory. But for every Sunyaev-Zel'dovich effect there is a Butcher-Oemler effect; there are as many cosmological phenomena established by observations, and only explained later by theory, as there were predicted by theory and confirmed by observations. In fact, in the last decade, there has been an explosion of new cosmological findings driven by observations. Some are so new that you won't find them mentioned in books just a few years old. So it is not just refreshing to see a book that reflects the new realities of cosmology, it is vital, if students are to truly stay up on a field that has widened in scope considerably. Observational Cosmology is filled with full-color images, and graphs from the latest experiments. How exciting it is that we live in an era where satellites and large experiments have gathered so much data to reveal astounding details about the origin of the universe and its evolution. To have all the latest data gathered together and explained in one book will be a revelation to students. In fact, at times it was to me. I've picked up modern cosmological knowledge through a patchwork of reading papers, going to colloquia, and serving on grant and telescope allocation panels. To go back and see them explained from square one, and summarized succinctly, filled in quite a few gaps in my own knowledge and corrected a few misconceptions I'd acquired along the way. To make room for all these graphs and observational details, a few things had to be left out. For one, there are few derivations
Cosmology of a covariant Galilean field.
De Felice, Antonio; Tsujikawa, Shinji
2010-09-10
We study the cosmology of a covariant scalar field respecting a Galilean symmetry in flat space-time. We show the existence of a tracker solution that finally approaches a de Sitter fixed point responsible for cosmic acceleration today. The viable region of model parameters is clarified by deriving conditions under which ghosts and Laplacian instabilities of scalar and tensor perturbations are absent. The field equation of state exhibits a peculiar phantomlike behavior along the tracker, which allows a possibility to observationally distinguish the Galileon gravity from the cold dark matter model with a cosmological constant.
LigParGen web server: an automatic OPLS-AA parameter generator for organic ligands
Dodda, Leela S.
2017-01-01
Abstract The accurate calculation of protein/nucleic acid–ligand interactions or condensed phase properties by force field-based methods require a precise description of the energetics of intermolecular interactions. Despite the progress made in force fields, small molecule parameterization remains an open problem due to the magnitude of the chemical space; the most critical issue is the estimation of a balanced set of atomic charges with the ability to reproduce experimental properties. The LigParGen web server provides an intuitive interface for generating OPLS-AA/1.14*CM1A(-LBCC) force field parameters for organic ligands, in the formats of commonly used molecular dynamics and Monte Carlo simulation packages. This server has high value for researchers interested in studying any phenomena based on intermolecular interactions with ligands via molecular mechanics simulations. It is free and open to all at jorgensenresearch.com/ligpargen, and has no login requirements. PMID:28444340
International Nuclear Information System (INIS)
Nam Gung, Chan; Lee, Yoon Sang; Hwang, Seong Sik; Kim, Hong Pyo
2004-01-01
The eddy current testing (ECT) is a nondestructive technique. It is used for evaluation of material's integrity, especially, steam generator (SG) tubing in nuclear plants, due to their rapid inspection, safe and easy operation. For depth measurement of defects, we prepared Electro Discharge Machined (EDM) notches that have several of defects and applied multi-parameter (MP) algorithm. It is a crack shape estimation program developed in Argonne National Laboratory (ANL). To evaluate the MP algorithm, we compared defect profile with fractography of the defects. In the following sections, we described the basic structure of a computer-aided data analysis algorithm used as means of more accurate and efficient processing of ECT data, and explained the specification of a standard calibration. Finally, we discussed the accuracy of estimated depth profile compared with conventional ECT method
Searching for sterile neutrinos in dynamical dark energy cosmologies
Feng, Lu; Zhang, Jing-Fei; Zhang, Xin
2018-05-01
We investigate how the dark energy properties change the cosmological limits on sterile neutrino parameters by using recent cosmological observations. We consider the simplest dynamical dark energy models, the wCDM model and the holographic dark energy (HDE) model, to make an analysis. The cosmological observations used in this work include the Planck 2015 CMB temperature and polarization data, the baryon acoustic oscillation data, the type Ia supernova data, the Hubble constant direct measurement data, and the Planck CMB lensing data. We find that, m v,terile ff energy properties could significantly influence the constraint limits of sterile neutrino parameters.
Kantowski--Sachs cosmological models as big-bang models
International Nuclear Information System (INIS)
Weber, E.
1985-01-01
In the presence of a nonzero cosmological constant Λ, we classify the anisotropic cosmological models of the Kantowski--Sachs type by means of the quantities epsilon 2 0 , q 0 , summation 0 corresponding, respectively, to the relative root-mean-square deviation from isotropy, the deceleration parameter, and the density parameter of the perfect fluid at a given time t = t 0 . We obtain for Λ>0 a set of big-bang models of zero measure as well as a set of cosmological models of nonzero measure evolving toward the de Sitter solution
International Nuclear Information System (INIS)
Beck, R.; Mihailovic, M.V.; Poljsak, M.
1980-05-01
Collisions between complex nuclei are described variationally in terms of the GCM with the aim to provide an evidence that it is a manageable calculational procedure. The variational principle of Kohn and Kato is used to derive the expression for the K matrix. The space of scattering states is spanned entirely by antisymmetrized products of shell model wave functions describing separate clusters; the generator coordinate is the separation between the two shell model potentials. Scattering boundary conditions are enforced by solving an integral equation for the channel GC amplitude in each open channel separately. The main part of evaluation of collision parameters is performed by calculating double integrals of a form factor between channel GC amplitudes. A theorem about a property of the form factors is proved which allows reduction of the amount of work needed to calculate double integrals. The application of the method to the elastic 3 H to 4 He scattering has shown the feasibility of the calculation. It is shown how an analysis of calculated scattering parameters and corresponding scattering states in terms of quasibound states enables one to make a consistent comparison with experiment and to extract some knowledge of the reaction mechanism. Finally a comparative list of the calculational procedures of the GCM and RGM for reactions is made. (author)
The case for the cosmological constant
Indian Academy of Sciences (India)
A time dependent cosmological A-term can be generated by scalar field ... Perlmutter et al (1999) indicate that the joint probability distribution of ΩС ΩA is well .... and С must be adjusted to very high levels of accuracy in order to ensure. С.
Cosmological constant in the quantum multiverse
International Nuclear Information System (INIS)
Larsen, Grant; Nomura, Yasunori; Roberts, Hannes L. L.
2011-01-01
Recently, a new framework for describing the multiverse has been proposed which is based on the principles of quantum mechanics. The framework allows for well-defined predictions, both regarding global properties of the universe and outcomes of particular experiments, according to a single probability formula. This provides complete unification of the eternally inflating multiverse and many worlds in quantum mechanics. In this paper, we elucidate how cosmological parameters can be calculated in this framework, and study the probability distribution for the value of the cosmological constant. We consider both positive and negative values, and find that the observed value is consistent with the calculated distribution at an order of magnitude level. In particular, in contrast to the case of earlier measure proposals, our framework prefers a positive cosmological constant over a negative one. These results depend only moderately on how we model galaxy formation and life evolution therein.
Cosmological evolution of p-brane networks
International Nuclear Information System (INIS)
Sousa, L.; Avelino, P. P.
2011-01-01
In this paper we derive, directly from the Nambu-Goto action, the relevant components of the acceleration of cosmological featureless p-branes, extending previous analysis based on the field theory equations in the thin-brane limit. The component of the acceleration parallel to the velocity is at the core of the velocity-dependent one-scale model for the evolution of p-brane networks. We use this model to show that, in a decelerating expanding universe in which the p-branes are relevant cosmologically, interactions cannot lead to frustration, except for fine-tuned nonrelativistic networks with a dimensionless curvature parameter k<<1. We discuss the implications of our findings for the cosmological evolution of p-brane networks.
Planck 2013 Cosmology Results: a Review
Directory of Open Access Journals (Sweden)
José Alberto Rubino-Martín
2014-12-01
Full Text Available This talk presents an overview of the cosmological results derived from the first 15.5 months of observations of the ESA’s Planck mission. These cosmological results are mainly based on the Planck measurements of the cosmic microwave background (CMB temperature and lensing-potential power spectra, although we also briefly discuss other aspects of the Planck data, as the statistical characterization of the reconstructed CMB maps, or the constraints on cosmological parameters using the number counts of galaxy clusters detected by means of the Sunyaev-Zeldovich effect in the Planck maps. All these results are described in detail in a series of papers released by ESA and the Planck collaboration in March 2013.
Cosmology in Poincaré gauge gravity with a pseudoscalar torsion
Energy Technology Data Exchange (ETDEWEB)
Lu, Jianbo; Chee, Guoying [Department of Physics, Liaoning Normal University,Dalian 116029 (China)
2016-05-04
A cosmology of Poincare{sup ´} gauge theory is developed, where several properties of universe corresponding to the cosmological equations with the pseudoscalar torsion function are investigated. The cosmological constant is found to be the intrinsic torsion and curvature of the vacuum universe and is derived from the theory naturally rather than added artificially, i.e. the dark energy originates from geometry and includes the cosmological constant but differs from it. The cosmological constant puzzle, the coincidence and fine tuning problem are relieved naturally at the same time. By solving the cosmological equations, the analytic cosmological solution is obtained and can be compared with the ΛCDM model. In addition, the expressions of density parameters of the matter and the geometric dark energy are derived, and it is shown that the evolution of state equations for the geometric dark energy agrees with the current observational data. At last, the full equations of linear cosmological perturbations and the solutions are obtained.
Constraining holographic cosmology using Planck data
Afshordi, Niayesh; Gould, Elizabeth; Skenderis, Kostas
2017-06-01
Holographic cosmology offers a novel framework for describing the very early Universe in which cosmological predictions are expressed in terms of the observables of a three-dimensional quantum field theory (QFT). This framework includes conventional slow-roll inflation, which is described in terms of a strongly coupled QFT, but it also allows for qualitatively new models for the very early Universe, where the dual QFT may be weakly coupled. The new models describe a universe which is nongeometric at early times. While standard slow-roll inflation leads to a (near-) power-law primordial power spectrum, perturbative super-renormalizable QFTs yield a new holographic spectral shape. Here, we compare the two predictions against cosmological observations. We use CosmoMC to determine the best fit parameters, and MultiNest for Bayesian evidence, comparing the likelihoods. We find that the dual QFT should be nonperturbative at the very low multipoles (l ≲30 ), while for higher multipoles (l ≳30 ) the new holographic model, based on perturbative QFT, fits the data just as well as the standard power-law spectrum assumed in Λ CDM cosmology. This finding opens the door to applications of nonperturbative QFT techniques, such as lattice simulations, to observational cosmology on gigaparsec scales and beyond.
Origin of a small cosmological constant in a brane world
International Nuclear Information System (INIS)
Ghoroku, Kazuo; Yahiro, Masanobu
2002-01-01
We address the relation between the parameters of an accelerating brane universe embedded in five-dimensional bulk space. It is pointed out that the tiny cosmological constant of our world can be obtained as quantum corrections around a given brane solution in the bulk theory or in the field theory on the boundary from a holographic viewpoint. Some implications to the cosmology and constraints on the parameters are also given
Li, Tingting; Fu, Xing; Dorantes-Gonzalez, Dante J.; Chen, Kun; Li, Yanning; Wu, Sen
2015-10-01
Laser-induced Surface Acoustic Waves (LSAWs) has been promisingly and widely used in recent years due to its rapid, high accuracy and non-contact evaluation potential of layered and thin film materials. For now, researchers have applied this technology on the characterization of materials' physical parameters, like Young's Modulus, density, and Poisson's ratio; or mechanical changes such as surface cracks and skin feature like a melanoma. While so far, little research has been done on providing practical guidelines on pulse laser parameters to best generate SAWs. In this paper finite element simulations of the thermos-elastic process based on human skin model for the generation of LSAWs were conducted to give the effects of pulse laser parameters have on the generated SAWs. And recommendations on the parameters to generate strong SAWs for detection and surface characterization without cause any damage to skin are given.
Stable cosmology in chameleon bigravity
De Felice, Antonio; Mukohyama, Shinji; Oliosi, Michele; Watanabe, Yota
2018-02-01
The recently proposed chameleonic extension of bigravity theory, by including a scalar field dependence in the graviton potential, avoids several fine-tunings found to be necessary in usual massive bigravity. In particular it ensures that the Higuchi bound is satisfied at all scales, that no Vainshtein mechanism is needed to satisfy Solar System experiments, and that the strong coupling scale is always above the scale of cosmological interest all the way up to the early Universe. This paper extends the previous work by presenting a stable example of cosmology in the chameleon bigravity model. We find a set of initial conditions and parameters such that the derived stability conditions on general flat Friedmann background are satisfied at all times. The evolution goes through radiation-dominated, matter-dominated, and de Sitter eras. We argue that the parameter space allowing for such a stable evolution may be large enough to encompass an observationally viable evolution. We also argue that our model satisfies all known constraints due to gravitational wave observations so far and thus can be considered as a unique testing ground of gravitational wave phenomenologies in bimetric theories of gravity.
The importance of local measurements for cosmology
Verde, Licia; Jimenez, Raul
2013-01-01
We explore how local, cosmology-independent measurements of the Hubble constant and the age of the Universe help to provide a powerful consistency check of the currently favored cosmological model (flat LambdaCDM) and model-independent constraints on cosmology. We use cosmic microwave background (CMB) data to define the model-dependent cosmological parameters, and add local measurements to assess consistency and determine whether extensions to the model are justified. At current precision, there is no significant tension between the locally measured Hubble constant and age of the Universe (with errors of 3% and 5% respectively) and the corresponding parameters derived from the CMB. However, if errors on the local measurements could be decreased by a factor of two, one could decisively conclude if there is tension or not. We also compare the local and CMB data assuming simple extensions of the flat, $\\Lambda$CDM model (including curvature, dark energy with a constant equation of state parameter not equal to -1...
Cosmological implications of primordial black holes
Energy Technology Data Exchange (ETDEWEB)
Luis Bernal, José; Bellomo, Nicola; Raccanelli, Alvise; Verde, Licia, E-mail: joseluis.bernal@icc.ub.edu, E-mail: nicola.bellomo@icc.ub.edu, E-mail: alvise@icc.ub.edu, E-mail: liciaverde@icc.ub.edu [ICC, University of Barcelona, IEEC-UB, Martí i Franquès, 1, E08028 Barcelona (Spain)
2017-10-01
The possibility that a relevant fraction of the dark matter might be comprised of Primordial Black Holes (PBHs) has been seriously reconsidered after LIGO's detection of a ∼ 30 M {sub ⊙} binary black holes merger. Despite the strong interest in the model, there is a lack of studies on possible cosmological implications and effects on cosmological parameters inference. We investigate correlations with the other standard cosmological parameters using cosmic microwave background observations, finding significant degeneracies, especially with the tilt of the primordial power spectrum and the sound horizon at radiation drag. However, these degeneracies can be greatly reduced with the inclusion of small scale polarization data. We also explore if PBHs as dark matter in simple extensions of the standard ΛCDM cosmological model induces extra degeneracies, especially between the additional parameters and the PBH's ones. Finally, we present cosmic microwave background constraints on the fraction of dark matter in PBHs, not only for monochromatic PBH mass distributions but also for popular extended mass distributions. Our results show that extended mass distribution's constraints are tighter, but also that a considerable amount of constraining power comes from the high-ℓ polarization data. Moreover, we constrain the shape of such mass distributions in terms of the correspondent constraints on the PBH mass fraction.
Hiding neutrino mass in modified gravity cosmologies
Energy Technology Data Exchange (ETDEWEB)
Bellomo, Nicola; Bellini, Emilio; Hu, Bin; Jimenez, Raul; Verde, Licia [ICC, University of Barcelona (UB-IEEC), Marti i Franques 1, 08028, Barcelona (Spain); Pena-Garay, Carlos, E-mail: nicola.bellomo@icc.ub.edu, E-mail: emilio.bellini@physics.ox.ac.uk, E-mail: binhu@icc.ub.edu, E-mail: raul.jimenez@icc.ub.edu, E-mail: penya@ific.uv.es, E-mail: liciaverde@icc.ub.edu [Instituto de Fisica Corpuscular, CSIC-UVEG, P.O. 22085, Valencia, 46071 (Spain)
2017-02-01
Cosmological observables show a dependence with the neutrino mass, which is partially degenerate with parameters of extended models of gravity. We study and explore this degeneracy in Horndeski generalized scalar-tensor theories of gravity. Using forecasted cosmic microwave background and galaxy power spectrum datasets, we find that a single parameter in the linear regime of the effective theory dominates the correlation with the total neutrino mass. For any given mass, a particular value of this parameter approximately cancels the power suppression due to the neutrino mass at a given redshift. The extent of the cancellation of this degeneracy depends on the cosmological large-scale structure data used at different redshifts. We constrain the parameters and functions of the effective gravity theory and determine the influence of gravity on the determination of the neutrino mass from present and future surveys.
Conformal symmetries of FRW accelerating cosmologies
International Nuclear Information System (INIS)
Kehagias, A.; Riotto, A.
2014-01-01
We show that any accelerating Friedmann–Robertson–Walker (FRW) cosmology with equation of state w<−1/3 (and therefore not only a de Sitter stage with w=−1) exhibits three-dimensional conformal symmetry on future constant-time hypersurfaces if the bulk theory is invariant under bulk conformal Killing vectors. We also offer an alternative derivation of this result in terms of conformal Killing vectors and show that long wavelength comoving curvature perturbations of the perturbed FRW metric are just conformal Killing motions of the FRW background. We then extend the boundary conformal symmetry to the bulk for accelerating cosmologies. Our findings indicate that one can easily generate perturbations of scalar fields which are not only scale invariant, but also fully conformally invariant on super-Hubble scales. Measuring a scale-invariant power spectrum for the cosmological perturbation does not automatically imply that the universe went through a de Sitter stage
Neutrino mass priors for cosmology from random matrices
Long, Andrew J.; Raveri, Marco; Hu, Wayne; Dodelson, Scott
2018-02-01
Cosmological measurements of structure are placing increasingly strong constraints on the sum of the neutrino masses, Σ mν, through Bayesian inference. Because these constraints depend on the choice for the prior probability π (Σ mν), we argue that this prior should be motivated by fundamental physical principles rather than the ad hoc choices that are common in the literature. The first step in this direction is to specify the prior directly at the level of the neutrino mass matrix Mν, since this is the parameter appearing in the Lagrangian of the particle physics theory. Thus by specifying a probability distribution over Mν, and by including the known squared mass splittings, we predict a theoretical probability distribution over Σ mν that we interpret as a Bayesian prior probability π (Σ mν). Assuming a basis-invariant probability distribution on Mν, also known as the anarchy hypothesis, we find that π (Σ mν) peaks close to the smallest Σ mν allowed by the measured mass splittings, roughly 0.06 eV (0.1 eV) for normal (inverted) ordering, due to the phenomenon of eigenvalue repulsion in random matrices. We consider three models for neutrino mass generation: Dirac, Majorana, and Majorana via the seesaw mechanism; differences in the predicted priors π (Σ mν) allow for the possibility of having indications about the physical origin of neutrino masses once sufficient experimental sensitivity is achieved. We present fitting functions for π (Σ mν), which provide a simple means for applying these priors to cosmological constraints on the neutrino masses or marginalizing over their impact on other cosmological parameters.
Sehgal, Neelima; Trac, Hy; Acquaviva, Viviana; Ade, Peter A. R.; Aguirre, Paula; Amiri, Mandana; Appel, John W.; Barrientos, L. Felipe; Battistelli, Elia S.; Bond, J. Richard;
2010-01-01
We present constraints on cosmological parameters based on a sample of Sunyaev-Zel'dovich-selected galaxy clusters detected in a millimeter-wave survey by the Atacama Cosmology Telescope. The cluster sample used in this analysis consists of 9 optically-confirmed high-mass clusters comprising the high-significance end of the total cluster sample identified in 455 square degrees of sky surveyed during 2008 at 148 GHz. We focus on the most massive systems to reduce the degeneracy between unknown cluster astrophysics and cosmology derived from SZ surveys. We describe the scaling relation between cluster mass and SZ signal with a 4-parameter fit. Marginalizing over the values of the parameters in this fit with conservative priors gives (sigma)8 = 0.851 +/- 0.115 and w = -1.14 +/- 0.35 for a spatially-flat wCDM cosmological model with WMAP 7-year priors on cosmological parameters. This gives a modest improvement in statistical uncertainty over WMAP 7-year constraints alone. Fixing the scaling relation between cluster mass and SZ signal to a fiducial relation obtained from numerical simulations and calibrated by X-ray observations, we find (sigma)8 + 0.821 +/- 0.044 and w = -1.05 +/- 0.20. These results are consistent with constraints from WMAP 7 plus baryon acoustic oscillations plus type Ia supernova which give (sigma)8 = 0.802 +/- 0.038 and w = -0.98 +/- 0.053. A stacking analysis of the clusters in this sample compared to clusters simulated assuming the fiducial model also shows good agreement. These results suggest that, given the sample of clusters used here, both the astrophysics of massive clusters and the cosmological parameters derived from them are broadly consistent with current models.
The Atacama Cosmology Telescope: Cosmology from Galaxy Clusters Detected via the Sunyaev-Zeldovich Effect
International Nuclear Information System (INIS)
Sehgal, N.
2011-01-01
We present constraints on cosmological parameters based on a sample of Sunyaev-Zeldovich-selected galaxy clusters detected in a millimeter-wave survey by the Atacama Cosmology Telescope. The cluster sample used in this analysis consists of 9 optically-confirmed high-mass clusters comprising the high-significance end of the total cluster sample identified in 455 square degrees of sky surveyed during 2008 at 148GHz. We focus on the most massive systems to reduce the degeneracy between unknown cluster astrophysics and cosmology derived from SZ surveys. We describe the scaling relation between cluster mass and SZ signal with a 4-parameter fit. Marginalizing over the values of the parameters in this fit with conservative priors gives σ 8 = 0.851 ± 0.115 and w = -1.14 ± 0.35 for a spatially-flat wCDM cosmological model with WMAP 7-year priors on cosmological parameters. This gives a modest improvement in statistical uncertainty over WMAP 7-year constraints alone. Fixing the scaling relation between cluster mass and SZ signal to a fiducial relation obtained from numerical simulations and calibrated by X-ray observations, we find σ 8 = 0.821 ± 0.044 and w = -1.05 ± 0.20. These results are consistent with constraints from WMAP 7 plus baryon acoustic oscillations plus type Ia supernoava which give σ 8 = 0.802 ± 0.038 and w = -0.98 ± 0.053. A stacking analysis of the clusters in this sample compared to clusters simulated assuming the fiducial model also shows good agreement. These results suggest that, given the sample of clusters used here, both the astrophysics of massive clusters and the cosmological parameters derived from them are broadly consistent with current models.
Energy Technology Data Exchange (ETDEWEB)
Weyant, Anja; Wood-Vasey, W. Michael [Pittsburgh Particle Physics, Astrophysics, and Cosmology Center (PITT PACC), Physics and Astronomy Department, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Schafer, Chad, E-mail: anw19@pitt.edu [Department of Statistics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States)
2013-02-20
Cosmological inference becomes increasingly difficult when complex data-generating processes cannot be modeled by simple probability distributions. With the ever-increasing size of data sets in cosmology, there is an increasing burden placed on adequate modeling; systematic errors in the model will dominate where previously these were swamped by statistical errors. For example, Gaussian distributions are an insufficient representation for errors in quantities like photometric redshifts. Likewise, it can be difficult to quantify analytically the distribution of errors that are introduced in complex fitting codes. Without a simple form for these distributions, it becomes difficult to accurately construct a likelihood function for the data as a function of parameters of interest. Approximate Bayesian computation (ABC) provides a means of probing the posterior distribution when direct calculation of a sufficiently accurate likelihood is intractable. ABC allows one to bypass direct calculation of the likelihood but instead relies upon the ability to simulate the forward process that generated the data. These simulations can naturally incorporate priors placed on nuisance parameters, and hence these can be marginalized in a natural way. We present and discuss ABC methods in the context of supernova cosmology using data from the SDSS-II Supernova Survey. Assuming a flat cosmology and constant dark energy equation of state, we demonstrate that ABC can recover an accurate posterior distribution. Finally, we show that ABC can still produce an accurate posterior distribution when we contaminate the sample with Type IIP supernovae.
International Nuclear Information System (INIS)
Weyant, Anja; Wood-Vasey, W. Michael; Schafer, Chad
2013-01-01
Cosmological inference becomes increasingly difficult when complex data-generating processes cannot be modeled by simple probability distributions. With the ever-increasing size of data sets in cosmology, there is an increasing burden placed on adequate modeling; systematic errors in the model will dominate where previously these were swamped by statistical errors. For example, Gaussian distributions are an insufficient representation for errors in quantities like photometric redshifts. Likewise, it can be difficult to quantify analytically the distribution of errors that are introduced in complex fitting codes. Without a simple form for these distributions, it becomes difficult to accurately construct a likelihood function for the data as a function of parameters of interest. Approximate Bayesian computation (ABC) provides a means of probing the posterior distribution when direct calculation of a sufficiently accurate likelihood is intractable. ABC allows one to bypass direct calculation of the likelihood but instead relies upon the ability to simulate the forward process that generated the data. These simulations can naturally incorporate priors placed on nuisance parameters, and hence these can be marginalized in a natural way. We present and discuss ABC methods in the context of supernova cosmology using data from the SDSS-II Supernova Survey. Assuming a flat cosmology and constant dark energy equation of state, we demonstrate that ABC can recover an accurate posterior distribution. Finally, we show that ABC can still produce an accurate posterior distribution when we contaminate the sample with Type IIP supernovae.
Inhomogeneous anisotropic cosmology
International Nuclear Information System (INIS)
Kleban, Matthew; Senatore, Leonardo
2016-01-01
In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with “flat” (including toroidal) and “open” (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are “flat” or “open”. Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with “flat” or “open” topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.
Is there evidence for additional neutrino species from cosmology?
Feeney, Stephen M.; Verde, Licia
2013-01-01
It has been suggested that recent cosmological and flavor-oscillation data favor the existence of additional neutrino species beyond the three predicted by the Standard Model of particle physics. We apply Bayesian model selection to determine whether there is indeed any evidence from current cosmological datasets for the standard cosmological model to be extended to include additional neutrino flavors. The datasets employed include cosmic microwave background temperature, polarization and lensing power spectra, and measurements of the baryon acoustic oscillation scale and the Hubble constant. We also consider other extensions to the standard neutrino model, such as massive neutrinos, and possible degeneracies with other cosmological parameters. The Bayesian evidence indicates that current cosmological data do not require any non-standard neutrino properties.
Induced cosmological constant in braneworlds with warped internal spaces
International Nuclear Information System (INIS)
Saharian, Aram A.
2006-01-01
We investigate the vacuum energy density induced by quantum fluctuations of a bulk scalar field with general curvature coupling parameter on two codimension one parallel branes in a (D + 1)-dimensional background spacetime AdS D1+1 x Σ with a warped internal space Σ. It is assumed that on the branes the field obeys Robin boundary conditions. Using the generalized zeta function technique in combination with contour integral representations, the surface energies on the branes are presented in the form of the sums of single brane and second brane induced parts. For the geometry of a single brane both regions, on the left (L-region) and on the right (R-region), of the brane are considered. The surface densities for separate L- and R-regions contain pole and finite contributions. For an infinitely thin brane taking these regions together, in odd spatial dimensions the pole parts cancel and the total surface energy is finite. The parts in the surface densities generated by the presence of the second brane are finite for all nonzero values of the interbrane separation. The contribution of the Kaluza-Klein modes along Σ is investigated in various limiting cases. It is shown that for large distances between the branes the induced surface densities give rise to an exponentially suppressed cosmological constant on the brane. In the higher dimensional generalization of the Randall-Sundrum braneworld model, for the interbrane distances solving the hierarchy problem, the cosmological constant generated on the visible brane is of the right order of magnitude with the value suggested by the cosmological observations. (author)
Energy Technology Data Exchange (ETDEWEB)
Meliopoulos, Sakis [Georgia Inst. of Technology, Atlanta, GA (United States); Cokkinides, George [Georgia Inst. of Technology, Atlanta, GA (United States); Fardanesh, Bruce [New York Power Authority, NY (United States); Hedrington, Clinton [U.S. Virgin Islands Water and Power Authority (WAPA), St. Croix (U.S. Virgin Islands)
2013-12-31
This is the final report for this project that was performed in the period: October1, 2009 to June 30, 2013. In this project, a fully distributed high-fidelity dynamic state estimator (DSE) that continuously tracks the real time dynamic model of a wide area system with update rates better than 60 times per second is achieved. The proposed technology is based on GPS-synchronized measurements but also utilizes data from all available Intelligent Electronic Devices in the system (numerical relays, digital fault recorders, digital meters, etc.). The distributed state estimator provides the real time model of the system not only the voltage phasors. The proposed system provides the infrastructure for a variety of applications and two very important applications (a) a high fidelity generating unit parameters estimation and (b) an energy function based transient stability monitoring of a wide area electric power system with predictive capability. Also the dynamic distributed state estimation results are stored (the storage scheme includes data and coincidental model) enabling an automatic reconstruction and “play back” of a system wide disturbance. This approach enables complete play back capability with fidelity equal to that of real time with the advantage of “playing back” at a user selected speed. The proposed technologies were developed and tested in the lab during the first 18 months of the project and then demonstrated on two actual systems, the USVI Water and Power Administration system and the New York Power Authority’s Blenheim-Gilboa pumped hydro plant in the last 18 months of the project. The four main thrusts of this project, mentioned above, are extremely important to the industry. The DSE with the achieved update rates (more than 60 times per second) provides a superior solution to the “grid visibility” question. The generator parameter identification method fills an important and practical need of the industry. The “energy function” based
Belinski, Vladimir
2018-01-01
Written for researchers focusing on general relativity, supergravity, and cosmology, this is a self-contained exposition of the structure of the cosmological singularity in generic solutions of the Einstein equations, and an up-to-date mathematical derivation of the theory underlying the Belinski–Khalatnikov–Lifshitz (BKL) conjecture on this field. Part I provides a comprehensive review of the theory underlying the BKL conjecture. The generic asymptotic behavior near the cosmological singularity of the gravitational field, and fields describing other kinds of matter, is explained in detail. Part II focuses on the billiard reformulation of the BKL behavior. Taking a general approach, this section does not assume any simplifying symmetry conditions and applies to theories involving a range of matter fields and space-time dimensions, including supergravities. Overall, this book will equip theoretical and mathematical physicists with the theoretical fundamentals of the Big Bang, Big Crunch, Black Hole singula...
Tomaschitz, R
1994-01-01
Spinor fields are studied in infinite, topologically multiply connected Robertson-Walker cosmologies. Unitary spinor representations for the discrete covering groups of the spacelike slices are constructed. The spectral resolution of Dirac's equation is given in terms of horospherical elementary waves, on which the treatment of spin and energy is based in these cosmologies. The meaning of the energy and the particle-antiparticle concept is explained in the context of this varying cosmic background. Discrete symmetries, in particular inversions of the multiply connected spacelike slices, are studied. The violation of the unitarity of the parity operator, due to self-interference of P-reflected wave packets, is discussed. The violation of the CP and CPT invariance - already on the level of the free Dirac equation on this cosmological background - is pointed out.
DEFF Research Database (Denmark)
Skaanes, Thea
2015-01-01
Abstract: This article concerns Hadza cosmology examined through objects, rituals and the Hadza concept of epeme. A brief background to the Hadza and the eldwork that informs this study is followed by a close analysis of three key objects that are central to the argument presented. The objects...... are intimately linked to women and to aspects of the social and cosmological identity of the individual makers. one object is a materi- alisation of the woman’s name and it leads to an examination by interview of naming practices more generally. Naming a child gives it a spirit and places the child in a strong...... of ethnographic research indicating the potential and need for further examination of the power and role of objects in Hadza society. Keywords: Hadza, epeme, ritual, cosmology, power objects...
Silk, Joseph; Barrow, John D; Saunders, Simon
2017-01-01
Following a long-term international collaboration between leaders in cosmology and the philosophy of science, this volume addresses foundational questions at the limit of science across these disciplines, questions raised by observational and theoretical progress in modern cosmology. Space missions have mapped the Universe up to its early instants, opening up questions on what came before the Big Bang, the nature of space and time, and the quantum origin of the Universe. As the foundational volume of an emerging academic discipline, experts from relevant fields lay out the fundamental problems of contemporary cosmology and explore the routes toward finding possible solutions. Written for graduates and researchers in physics and philosophy, particular efforts are made to inform academics from other fields, as well as the educated public, who wish to understand our modern vision of the Universe, related philosophical questions, and the significant impacts on scientific methodology.
Energy Technology Data Exchange (ETDEWEB)
Vignati, E.; Hertel, O.; Berkowicz, R. [National Environmental Research Inst., Dept. of Atmospheric Enviroment (Denmark); Raaschou-Nielsen, O. [Danish Cancer Society, Division of Cancer Epidemiology (Denmark)
1997-05-01
The method for generation of the input data for the calculations with OSPM is presented in this report. The described method which is based on information provided from a questionnaire, will be used for model calculations of long term exposure for a large number of children in connection with an epidemiological study. A test of the calculation method has been performed on a few locations in which detailed measurements of air pollution, meteorological data and traffic were available. Comparisons between measured and calculated concentrations were made for hourly, monthly and yearly values. Beside the measured concentrations, the test results were compared to results obtained with the optimal street configuration data and measured traffic. The main conclusions drawn from this investigation are: (1) The calculation method works satisfactory well for long term averages, whereas the uncertainties are high when short term averages are considered. (2) The street width is one of the most crucial input parameters for the calculation of street pollution levels for both short and long term averages. Using H.C. Andersens Boulevard as an example, it was shown that estimation of street width based on traffic amount can lead to large overestimation of the concentration levels (in this case 50% for NO{sub x} and 30% for NO{sub 2}). (3) The street orientation and geometry is important for prediction of short term concentrations but this importance diminished for longer term averages. (4) The uncertainties in diurnal traffic profiles can influence the accuracy of short term averages, but are less important for long term averages. The correlation is good between modelled and measured concentrations when the actual background concentrations are replaced with the generated values. Even though extreme situations are difficult to reproduce with this method, the comparison between the yearly averaged modelled and measured concentrations is very good. (LN) 20 refs.
TCP, quantum gravity, the cosmological constant and all that .
International Nuclear Information System (INIS)
Banks, T.
1985-01-01
We study cosmology from the point of view of quantum gravity. Some light is thrown on the nature of time, and it is suggested that the cosmological arrow of time is generated by a spontaneous breakdown of TCP. Conventional cosmological models in which quantum fields interact with a time-dependent gravitational field are shown to describe an approximation to the quantum gravitational wave function which is valid in the long-wavelength limit. Two problems with initial conditions are resolved in models in which a negative bare cosmological constant is cancelled by the classical excitation of a Bose field eta with a very flat potential. These models can also give a natural explanation for the observed value of the cosmological constant. (orig.)
Non equilibrium relativistic cosmology
International Nuclear Information System (INIS)
Novello, M.; Salim, J.M.
1982-01-01
A certain systematization through the discussion of results already known on cosmology and the presentation of new ones is given. In section 2 a brief review of the necessary mathematical background is also given. The theory of perturbation of Friedmann-like Universes is presented in section 3. The reduction of Einstein's equations for homogeneous Universes to an autonomous planar system of differential equations is done in section 4. Finally in section 5 the alternative gravitational non-minimal coupling and its consequences to cosmology are discussed. (Author) [pt
CERN. Geneva
2000-01-01
Most of the puzzles with standard big bang cosmology can be avoided if the big bang is NOT identified with the beginning of time. The short-distance cutoff and duality symmetries of superstring theory suggest a new (so-called pre-big bang) cosmology in which the birth of our Universe is the result of a long classical evolution characterized by a gravitational instability. I will motivate and describe this heretical scenario and compare its phenomenological implications with those of ortodox (post-big bang) inflation.
2012-01-01
This volume tells of the quest for cosmology as seen by some of the finest cosmologists in the world. It starts with "Galaxy Formation from Start to Finish" and ends with "The First Supermassive Black Holes in the Universe," exploring in between the grand themes of galaxies, the early universe, expansion of the universe, dark matter and dark energy. This up-to-date collection of review articles offers a general introduction to cosmology and is intended for all probing into the profound questions on where we came from and where we are going.
Silk, Joseph
2011-01-01
Horizons of Cosmology: Exploring Worlds Seen and Unseen is the fourth title published in the Templeton Science and Religion Series, in which scientists from a wide range of fields distill their experience and knowledge into brief tours of their respective specialties. In this volume, highly esteemed astrophysicist Joseph Silk explores the vast mysteries and speculations of the field of cosmology in a way that balances an accessible style for the general reader and enough technical detail for advanced students and professionals. Indeed, while the p
Relativistic Cosmology Revisited
Directory of Open Access Journals (Sweden)
Crothers S. J.
2007-04-01
Full Text Available In a previous paper the writer treated of particular classes of cosmological solutions for certain Einstein spaces and claimed that no such solutions exist in relation thereto. In that paper the assumption that the proper radius is zero when the line-element is singular was generally applied. This general assumption is unjustified and must be dropped. Consequently, solutions do exist in relation to the aforementioned types, and are explored herein. The concept of the Big Bang cosmology is found to be inconsistent with General Relativity
Tkachev, Igor
2017-01-01
This lecture course covers cosmology from the particle physicist perspective. Therefore, the emphasis will be on the evidence for the new physics in cosmological and astrophysical data together with minimal theoretical frameworks needed to understand and appreciate the evidence. I review the case for non-baryonic dark matter and describe popular models which incorporate it. In parallel, the story of dark energy will be developed, which includes accelerated expansion of the Universe today, the Universe origin in the Big Bang, and support for the Inflationary theory in CMBR data.
International Nuclear Information System (INIS)
Stabell, R.
1979-01-01
Einstein applied his gravitation theory to a universe model with positively curved space in 1917. In order to maintain a static universe he introduced the cosmological constant, which in the light of later nonstatic universe models, he described as his life's greatest mistake. The best known such model is the Einstein-de Sitter model, which is here discussed in some detail. The 'big bang' theory is also discussed leading to the cosmic background radiation. The early phase of the 'big bang' cosmology, the first ten seconds, and the first minutes are discussed, leading to the transparent stage. (JIW)
Cosmological models without singularities
International Nuclear Information System (INIS)
Petry, W.
1981-01-01
A previously studied theory of gravitation in flat space-time is applied to homogeneous and isotropic cosmological models. There exist two different classes of models without singularities: (i) ever-expanding models, (ii) oscillating models. The first class contains models with hot big bang. For these models there exist at the beginning of the universe-in contrast to Einstein's theory-very high but finite densities of matter and radiation with a big bang of very short duration. After short time these models pass into the homogeneous and isotropic models of Einstein's theory with spatial curvature equal to zero and cosmological constant ALPHA >= O. (author)
Difficulties with inflationary cosmology
International Nuclear Information System (INIS)
Penrose, R.
1989-01-01
According to the author, the idea of inflationary cosmology is an ingenious attempt to solve some of the major puzzles of cosmology, most notably the flatness problem, the homogeneity (horizon) problem, and the monopole problem. The homogeneity problem, in particular, is intimately connected with a largely unappreciated, but profound puzzle presented by the second law of thermodynamics. The author argues that the mechanism of inflation does not, by itself, come to terms with this and consequently, comes nowhere close to providing an understanding of the large-scale homogeneity of the universe
International Nuclear Information System (INIS)
Marrakchi, A.E.L.; Tapia, V.
1992-05-01
Some cosmological implications of the recently proposed fourth-rank theory of gravitation are studied. The model exhibits the possibility of being free from the horizon and flatness problems at the price of introducing a negative pressure. The field equations we obtain are compatible with k obs =0 and Ω obs t clas approx. 10 20 t Planck approx. 10 -23 s. When interpreted at the light of General Relativity the treatment is shown to be almost equivalent to that of the standard model of cosmology combined with the inflationary scenario. Hence, an interpretation of the negative pressure hypothesis is provided. (author). 8 refs
Cosmological constants and variations
International Nuclear Information System (INIS)
Barrow, John D
2005-01-01
We review properties of theories for the variation of the gravitation and fine structure 'constants'. We highlight some general features of the cosmological models that exist in these theories with reference to recent quasar data that is consistent with time-variation in the fine structure 'constant' since a redshift of 3.5. The behaviour of a simple class of varying alpha cosmologies is outlined in the light of all the observational constraints. We also discuss some of the consequences of varying 'constants' for oscillating universes and show by means of exact solutions that they appear to evolve monotonically in time even though the scale factor of the universe oscillates
Zucker, M. H.
This paper is a critical analysis and reassessment of entropic functioning as it applies to the question of whether the ultimate fate of the universe will be determined in the future to be "open" (expanding forever to expire in a big chill), "closed" (collapsing to a big crunch), or "flat" (balanced forever between the two). The second law of thermodynamics declares that entropy can only increase and that this principle extends, inevitably, to the universe as a whole. This paper takes the position that this extension is an unwarranted projection based neither on experience nonfact - an extrapolation that ignores the powerful effect of a gravitational force acting within a closed system. Since it was originally presented by Clausius, the thermodynamic concept of entropy has been redefined in terms of "order" and "disorder" - order being equated with a low degree of entropy and disorder with a high degree. This revised terminology more subjective than precise, has generated considerable confusion in cosmology in several critical instances. For example - the chaotic fireball of the big bang, interpreted by Stephen Hawking as a state of disorder (high entropy), is infinitely hot and, thermally, represents zero entropy (order). Hawking, apparently focusing on the disorderly "chaotic" aspect, equated it with a high degree of entropy - overlooking the fact that the universe is a thermodynamic system and that the key factor in evaluating the big-bang phenomenon is the infinitely high temperature at the early universe, which can only be equated with zero entropy. This analysis resolves this confusion and reestablishes entropy as a cosmological function integrally linked to temperature. The paper goes on to show that, while all subsystems contained within the universe require external sources of energization to have their temperatures raised, this requirement does not apply to the universe as a whole. The universe is the only system that, by itself can raise its own
Directory of Open Access Journals (Sweden)
Juliana Zottis
2014-03-01
Full Text Available The drawing process of steel bars is usually used to check better dimensional accuracy and mechanical properties to the material. In the other hand, the major concern found in manufacturing axes through this process is the appearance of distortion of shape. Such distortions are directly linked to the accumulation of residual stresses generated during the processes. As a result, this paper aims to study the influence of process parameters such as shape of puller, speed and lubrication used in wire drawing analyzing the accumulation of residual stress after the process. The stress analysis was performed by FEM being used two simulation software: Simufact.formingGP and DeformTM. Through these analyzes, it was found that the shape of how the bar is pulled causes a reduction of up to 100 MPa in residual stresses in the center of the bar, which represents an important factor in the study of the possible causes of the distortion. As well as factors speed and homogeneity of lubrication significantly altered the profile of residual stresses in the bar.
Energy Technology Data Exchange (ETDEWEB)
Ramos, D S [Companhia Energetica de Sao Paulo, SP (Brazil); Albuquerque, J C.R.; Rosenblat, J [ELETROBRAS, Rio de Janeiro, RJ (Brazil)
1994-12-31
The paper presents a new formulation that makes feasible a composition of long run production marginal costs with the long run transmission marginal costs, including the costs related to the interconnection EHV networks and that related to the voltage levels below. The goal top be attained is to have available a more adequate parameter in order to compare production cost related to a plant, that will be connected to a certain voltage level network, to the cost related supplying the sam,e amount of energy from the bulk power system which will be represented by the marginal costs up to the voltage level under consideration. This procedure brings to light the Transmission Avoided Costs concepts, that are stressed throughout the text. The proposed methodology is now being used, in the brazilian Power Sector, as a rule of thumb in order to guide planning decisions about the schedule of new plants that have installed capacity below 30 MW. For plants with higher capacity, the transmission avoided costs are evaluated for each specific case, simulating the system behavior without the quoted hydroelectric plant. This paper focuses, an an application example, the case of the Canoas Hydroelectric Project, recently included in the Generation Expansion Reference Plan after a detailed analysis supported by the methodology described here. (author) 7 refs., 3 tabs.
Conformal symmetry and holographic cosmology
Bzowski, A.W.
2013-01-01
This thesis presents a novel approach to cosmology using gauge/gravity duality. Analysis of the implications of conformal invariance in field theories leads to quantitative cosmological predictions which are in agreement with current data. Furthermore, holographic cosmology extends the theory of
Quintessence and the cosmological constant
International Nuclear Information System (INIS)
Doran, M.; Wetterich, C.
2003-01-01
Quintessence -- the energy density of a slowly evolving scalar field -- may constitute a dynamical form of the homogeneous dark energy in the universe. We review the basic idea in the light of the cosmological constant problem. Cosmological observations or a time variation of fundamental 'constants' can distinguish quintessence from a cosmological constant
Cosmology with weak lensing surveys
International Nuclear Information System (INIS)
Munshi, Dipak; Valageas, Patrick; Waerbeke, Ludovic van; Heavens, Alan
2008-01-01
Weak gravitational lensing is responsible for the shearing and magnification of the images of high-redshift sources due to the presence of intervening matter. The distortions are due to fluctuations in the gravitational potential, and are directly related to the distribution of matter and to the geometry and dynamics of the Universe. As a consequence, weak gravitational lensing offers unique possibilities for probing the Dark Matter and Dark Energy in the Universe. In this review, we summarise the theoretical and observational state of the subject, focussing on the statistical aspects of weak lensing, and consider the prospects for weak lensing surveys in the future. Weak gravitational lensing surveys are complementary to both galaxy surveys and cosmic microwave background (CMB) observations as they probe the unbiased non-linear matter power spectrum at modest redshifts. Most of the cosmological parameters are accurately estimated from CMB and large-scale galaxy surveys, so the focus of attention is shifting to understanding the nature of Dark Matter and Dark Energy. On the theoretical side, recent advances in the use of 3D information of the sources from photometric redshifts promise greater statistical power, and these are further enhanced by the use of statistics beyond two-point quantities such as the power spectrum. The use of 3D information also alleviates difficulties arising from physical effects such as the intrinsic alignment of galaxies, which can mimic weak lensing to some extent. On the observational side, in the next few years weak lensing surveys such as CFHTLS, VST-KIDS and Pan-STARRS, and the planned Dark Energy Survey, will provide the first weak lensing surveys covering very large sky areas and depth. In the long run even more ambitious programmes such as DUNE, the Supernova Anisotropy Probe (SNAP) and Large-aperture Synoptic Survey Telescope (LSST) are planned. Weak lensing of diffuse components such as the CMB and 21 cm emission can also
Cosmology with weak lensing surveys
Energy Technology Data Exchange (ETDEWEB)
Munshi, Dipak [Institute of Astronomy, Madingley Road, Cambridge, CB3 OHA (United Kingdom); Astrophysics Group, Cavendish Laboratory, Madingley Road, Cambridge CB3 OHE (United Kingdom)], E-mail: munshi@ast.cam.ac.uk; Valageas, Patrick [Service de Physique Theorique, CEA Saclay, 91191 Gif-sur-Yvette (France); Waerbeke, Ludovic van [University of British Columbia, Department of Physics and Astronomy, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada); Heavens, Alan [SUPA - Scottish Universities Physics Alliance, Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom)
2008-06-15
Weak gravitational lensing is responsible for the shearing and magnification of the images of high-redshift sources due to the presence of intervening matter. The distortions are due to fluctuations in the gravitational potential, and are directly related to the distribution of matter and to the geometry and dynamics of the Universe. As a consequence, weak gravitational lensing offers unique possibilities for probing the Dark Matter and Dark Energy in the Universe. In this review, we summarise the theoretical and observational state of the subject, focussing on the statistical aspects of weak lensing, and consider the prospects for weak lensing surveys in the future. Weak gravitational lensing surveys are complementary to both galaxy surveys and cosmic microwave background (CMB) observations as they probe the unbiased non-linear matter power spectrum at modest redshifts. Most of the cosmological parameters are accurately estimated from CMB and large-scale galaxy surveys, so the focus of attention is shifting to understanding the nature of Dark Matter and Dark Energy. On the theoretical side, recent advances in the use of 3D information of the sources from photometric redshifts promise greater statistical power, and these are further enhanced by the use of statistics beyond two-point quantities such as the power spectrum. The use of 3D information also alleviates difficulties arising from physical effects such as the intrinsic alignment of galaxies, which can mimic weak lensing to some extent. On the observational side, in the next few years weak lensing surveys such as CFHTLS, VST-KIDS and Pan-STARRS, and the planned Dark Energy Survey, will provide the first weak lensing surveys covering very large sky areas and depth. In the long run even more ambitious programmes such as DUNE, the Supernova Anisotropy Probe (SNAP) and Large-aperture Synoptic Survey Telescope (LSST) are planned. Weak lensing of diffuse components such as the CMB and 21 cm emission can also
Condensed matter analogues of cosmology
Kibble, Tom; Srivastava, Ajit
2013-10-01
It is always exciting when developments in one branch of physics turn out to have relevance in a quite different branch. It would be hard to find two branches farther apart in terms of energy scales than early-universe cosmology and low-temperature condensed matter physics. Nevertheless ideas about the formation of topological defects during rapid phase transitions that originated in the context of the very early universe have proved remarkably fruitful when applied to a variety of condensed matter systems. The mathematical frameworks for describing these systems can be very similar. This interconnection has led to a deeper understanding of the phenomena in condensed matter systems utilizing ideas from cosmology. At the same time, one can view these condensed matter analogues as providing, at least in a limited sense, experimental access to the phenomena of the early universe for which no direct probe is possible. As this special issue well illustrates, this remains a dynamic and exciting field. The basic idea is that when a system goes through a rapid symmetry-breaking phase transition from a symmetric phase into one with spontaneously broken symmetry, the order parameter may make different choices in different regions, creating domains that when they meet can trap defects. The scale of those domains, and hence the density of defects, is constrained by the rate at which the system goes through the transition and the speed with which order parameter information propagates. This is what has come to be known as the Kibble-Zurek mechanism. The resultant scaling laws have now been tested in a considerable variety of different systems. The earliest experiments illustrating the analogy between cosmology and condensed matter were in liquid crystals, in particular on the isotropic-to-nematic transition, primarily because it is very easy to induce the phase transition (typically at room temperature) and to image precisely what is going on. This field remains one of the
A Bayesian and Physics-Based Ground Motion Parameters Map Generation System
Ramirez-Guzman, L.; Quiroz, A.; Sandoval, H.; Perez-Yanez, C.; Ruiz, A. L.; Delgado, R.; Macias, M. A.; Alcántara, L.
2014-12-01
We present the Ground Motion Parameters Map Generation (GMPMG) system developed by the Institute of Engineering at the National Autonomous University of Mexico (UNAM). The system delivers estimates of information associated with the social impact of earthquakes, engineering ground motion parameters (gmp), and macroseismic intensity maps. The gmp calculated are peak ground acceleration and velocity (pga and pgv) and response spectral acceleration (SA). The GMPMG relies on real-time data received from strong ground motion stations belonging to UNAM's networks throughout Mexico. Data are gathered via satellite and internet service providers, and managed with the data acquisition software Earthworm. The system is self-contained and can perform all calculations required for estimating gmp and intensity maps due to earthquakes, automatically or manually. An initial data processing, by baseline correcting and removing records containing glitches or low signal-to-noise ratio, is performed. The system then assigns a hypocentral location using first arrivals and a simplified 3D model, followed by a moment tensor inversion, which is performed using a pre-calculated Receiver Green's Tensors (RGT) database for a realistic 3D model of Mexico. A backup system to compute epicentral location and magnitude is in place. A Bayesian Kriging is employed to combine recorded values with grids of computed gmp. The latter are obtained by using appropriate ground motion prediction equations (for pgv, pga and SA with T=0.3, 0.5, 1 and 1.5 s ) and numerical simulations performed in real time, using the aforementioned RGT database (for SA with T=2, 2.5 and 3 s). Estimated intensity maps are then computed using SA(T=2S) to Modified Mercalli Intensity correlations derived for central Mexico. The maps are made available to the institutions in charge of the disaster prevention systems. In order to analyze the accuracy of the maps, we compare them against observations not considered in the
Indian Academy of Sciences (India)
in quality, quantity, and the scope of cosmological observations. While the ob- ... In this article, I summarize both the oral and poster presentations made at the workshop. ... the angular spectrum of CMB anisotropy with recent measurements of the power spectrum of ..... A thermodynamical treatment within the framework of.
Culture and Children's Cosmology
Siegal, Michael; Butterworth, George; Newcombe, Peter A.
2004-01-01
In this investigation, we examined children's knowledge of cosmology in relation to the shape of the earth and the day-night cycle. Using explicit questioning involving a choice of alternative answers and 3D models, we carried out a comparison of children aged 4-9 years living in Australia and England. Though Australia and England have a close…
Cosmological dynamical systems
Leon, Genly
2011-01-01
In this book are studied, from the perspective of the dynamical systems, several Universe models. In chapter 1 we give a bird's eye view on cosmology and cosmological problems. Chapter 2 is devoted to a brief review on some results and useful tools from the qualitative theory of dynamical systems. They provide the theoretical basis for the qualitative study of concrete cosmological models. Chapters 1 and 2 are a review of well-known results. Chapters 3, 4, 5 and 6 are devoted to our main results. In these chapters are extended and settled in a substantially different, more strict mathematical language, several results obtained by one of us in arXiv:0812.1013 [gr-qc]; arXiv:1009.0689 [gr-qc]; arXiv:0904.1577[gr-qc]; and arXiv:0909.3571 [hep-th]. In chapter 6, we provide a different approach to the subject discussed in astro-ph/0503478. Additionally, we perform a Poincar\\'e compactification process allowing to construct a global phase space containing all the cosmological information in both finite and infinite...
International Nuclear Information System (INIS)
Schramm, D.N.
1995-01-01
Primordial nucleosynthesis has established itself as one of the three pillars of Big Bang cosmology. Many of the Big Bang Nucleosynthesis reactions involve unstable nuclei. Hence there is a tight relationship hetween the subject of this conference and cosmology. The prime role of unstable nuclei in cosmology is related to lithium synthesis and the lack of cosmological synthesis of Be and B. These nuclei will thus be focused upon. Nucleosynthesis involves comparing calculated abundances with observed abundances. In general, abundance determinations are dominated by systematic rather than statistical errors, and work on bounding systematics is crucial. The quark-hadron inspired inhomogeneous calculations now unanimously agree that only relatively small variations in Ω b are possible vis-a-vis the homogeneous model; hence the robustness of Ω b ∼0.05 is now apparent. (These calculations depend critically on unstable nuclei.) The above argues that the bulk of the baryons in the universe are not producing visible light. A comparison with the ROSAT cluster data is also shown to be consistent with the standard BBN model. Ω b ∼1 seems to be definitely excluded, so if Ω TOTAL =1, as some recent observations may hint, then non-baryonic dark matter is required. The implications of the recently reported halo microlensing events are discussed. In summary, it is argued that the physics of unstable nuclei affects the fundamental dark matter argument. ((orig.))
McFadden, P.; Skenderis, K.
2010-01-01
We propose a holographic description of four-dimensional single-scalar inflationary universes, and show how cosmological observables, such as the primordial power spectrum, are encoded in the correlation functions of a three-dimensional quantum field theory (QFT). The holographic description
Solitons in relativistic cosmologies
International Nuclear Information System (INIS)
Pullin, J.
1988-08-01
The application to the construction of solitonic cosmologies in General Relativity of the Inverse Scattering Technique of Belinskii an Zakharov is analyzed. Three improvements to the mentioned technique are proposed: the inclusion of higher order poles in the scattering matrix, a new renormalization technique for diagonal metrics and the extension of the technique to include backgrounds with material content by means of a Kaluza-Klein formalism. As a consequence of these improvements, three new aspects can be analyzed: a) The construction of anisotropic and inhomogeneous cosmological models which can mimic the formation of halos and voids, due to the presence of a material content. The new renormalization technique allows to construct an exact perturbation theory. b) The analysis of the dynamics of models with cosmological constant (inflationary models) and their perturbations. c) The study of interaction of gravitational solitonic waves on material backgrounds. Moreover, some additional works, connected with the existance of 'Crack of doom' type singularities in Kaluza-Klein cosmologies, stochastic perturbations in inflationary universes and inflationary phase transitions in rotating universes are described. (Author) [es
Indian Academy of Sciences (India)
This report is based on a recent work in collaboration with Bagla and Padmanabhan. [1]. In this paper, we construct cosmological models with homogeneous tachyon matter [2] to provide the dark energy component which drives acceleration of the universe (for a recent review of dark energy models, see [3]). We assume that.
International Nuclear Information System (INIS)
Heller, M.
1986-01-01
It is proposed to understand cosmology as a non-local physics. Non-local methods, when developed from locally performed observations, imply a considerable extrapolation, which in turn is possible without some unverifiable assumptions. Cosmology is, therefore, not only a science on the Universe but also about assumptions that render such a science possible. As far as theoretical aspects of cosmology are concerned, cosmology can be treated as a theory of the space of all solutions to Einstein's field equations (called the ensemble of universes). The very distinction is touched upon between solutions of differential equations, expressing laws of nature, and boundary conditions identifying particular instances of the law's operation. Both observational and theoretical studies demonstrate that our Universe occupies a distinguished position within the ensemble of universes. This fact remains in a close relationship with the existence and developing of structures in the Universe. Possible philosophies aimed at justifying or neutralizing our distinguished situation in the ensemble of universes are discussed at some length. 60 refs. (author)
Energy Technology Data Exchange (ETDEWEB)
Turner, Michael S
1999-03-01
For two decades the hot big-bang model as been referred to as the standard cosmology - and for good reason. For just as long cosmologists have known that there are fundamental questions that are not answered by the standard cosmology and point to a grander theory. The best candidate for that grander theory is inflation + cold dark matter. It holds that the Universe is flat, that slowly moving elementary particles left over from the earliest moments provide the cosmic infrastructure, and that the primeval density inhomogeneities that seed all the structure arose from quantum fluctuations. There is now prima facie evidence that supports two basic tenets of this paradigm. An avalanche of high-quality cosmological observations will soon make this case stronger or will break it. Key questions remain to be answered; foremost among them are: identification and detection of the cold dark matter particles and elucidation of the dark-energy component. These are exciting times in cosmology{exclamation_point}.
Excessive extrapolations in cosmology
Czech Academy of Sciences Publication Activity Database
Křížek, Michal; Somer, L.
2016-01-01
Roč. 22, č. 3 (2016), s. 270-280 ISSN 0202-2893 Institutional support: RVO:67985840 Keywords : cosmology * friedmann equation Subject RIV: BA - General Mathematics Impact factor: 0.734, year: 2016 http://link.springer.com/article/10.1134%2FS0202289316030105
, i.e. with the cosmology hidden. Looking Beyond Lambda with the Union Supernova Compilation by Rubin et Matrix Description Covariance Matrix with Systematics Description Full Table of All SNe Description Beyond Lambda Figures Updated 11-18-11 Contact: drubin at physics dot fsu dot edu, saul at lbl dot gov
Kevane, C J
1961-02-24
A cosmological model based on a gravitational plasma of matter and antimatter is discussed. The antigravitational interaction of matter and antimatter leads to segregation and an expansion of the plasma universe. The expansion time scale is controlled by the aggregation time scale.
Relic gravitational waves and cosmology
International Nuclear Information System (INIS)
Grishchuk, Leonid P
2005-01-01
The paper begins with a brief recollection of interactions of the author with Ya B Zeldovich in the context of the study of relic gravitational waves. The principles and early results on the quantum-mechanical generation of cosmological perturbations are then summarized. The expected amplitudes of relic gravitational waves differ in various frequency windows, and therefore the techniques and prospects of their detection are distinct. One section of the paper describes the present state of efforts in direct detection of relic gravitational waves. Another section is devoted to indirect detection via the anisotropy and polarization measurements of the cosmic microwave background (CMB) radiation. It is emphasized throughout the paper that the inference about the existence and expected amount of relic gravitational waves is based on a solid theoretical foundation and the best available cosmological observations. It is also explained in great detail what went wrong with the so-called 'inflationary gravitational waves', whose amount is predicted by inflationary theorists to be negligibly small, thus depriving them of any observational significance. (reviews of topical problems)
Relaxing a large cosmological constant
International Nuclear Information System (INIS)
Bauer, Florian; Sola, Joan; Stefancic, Hrvoje
2009-01-01
The cosmological constant (CC) problem is the biggest enigma of theoretical physics ever. In recent times, it has been rephrased as the dark energy (DE) problem in order to encompass a wider spectrum of possibilities. It is, in any case, a polyhedric puzzle with many faces, including the cosmic coincidence problem, i.e. why the density of matter ρ m is presently so close to the CC density ρ Λ . However, the oldest, toughest and most intriguing face of this polyhedron is the big CC problem, namely why the measured value of ρ Λ at present is so small as compared to any typical density scale existing in high energy physics, especially taking into account the many phase transitions that our Universe has undergone since the early times, including inflation. In this Letter, we propose to extend the field equations of General Relativity by including a class of invariant terms that automatically relax the value of the CC irrespective of the initial size of the vacuum energy in the early epochs. We show that, at late times, the Universe enters an eternal de Sitter stage mimicking a tiny positive cosmological constant. Thus, these models could be able to solve the big CC problem without fine-tuning and have also a bearing on the cosmic coincidence problem. Remarkably, they mimic the ΛCDM model to a large extent, but they still leave some characteristic imprints that should be testable in the next generation of experiments.
Projective relativity, cosmology and gravitation
International Nuclear Information System (INIS)
Arcidiacono, G.
1986-01-01
This book describes the latest applications of projective geometry to cosmology and gravitation. The contents of the book are; the Poincare group and Special Relativity, the thermodynamics and electromagnetism, general relativity, gravitation and cosmology, group theory and models of universe, the special projective relativity, the Fantappie group and Big-Bang cosmology, a new cosmological projective mechanics, the plasma physics and cosmology, the projective magnetohydrodynamics field, projective relativity and waves propagation, the generalizations of the gravitational field, the general projective relativity, the projective gravitational field, the De Sitter Universe and quantum physics, the conformal relativity and Newton gravitation
Post-inflationary brane cosmology
International Nuclear Information System (INIS)
Mazumdar, Anupam
2001-01-01
The brane cosmology has invoked new challenges to the usual Big Bang cosmology. In this paper we present a brief account on thermal history of the post-inflationary brane cosmology. We have realized that it is not obvious that the post-inflationary brane cosmology would always deviate from the standard Big Bang cosmology. However, if it deviates some stringent conditions on the brane tension are to be satisfied. In this regard we study various implications on gravitino production and its abundance. We discuss Affleck-Dine mechanism for baryogenesis and make some comments on moduli and dilaton problems in this context
Open problems in string cosmology
International Nuclear Information System (INIS)
Toumbas, N.
2010-01-01
Some of the open problems in string cosmology are highlighted within the context of the recently constructed thermal and quantum superstring cosmological solutions. Emphasis is given on the high temperature cosmological regime, where it is argued that thermal string vacua in the presence of gravito-magnetic fluxes can be used to bypass the Hagedorn instabilities of string gas cosmology. This article is based on a talk given at the workshop on ''Cosmology and Strings'', Corfu, September 6-13, 2009. (Abstract Copyright [2010], Wiley Periodicals, Inc.)
Cosmology and a general scalar-tensor theory of gravity
International Nuclear Information System (INIS)
Bishop, N.T.
1976-01-01
The cosmological models resulting from a general scalar-tensor theory of gravity are discussed. Those models for which the scalar field varies as a power of the cosmological expansion factor (i.e. phi varies as Rsup(n)) are considered in detail, leading to a set of such models compatible with observation. This set includes models in which the scalar coupling parameter ω is negative. The models described here are similar to those of Newtonian cosmology obtained from an impotence principle. (author)
Holographic dark energy in Brans-Dicke cosmology with chameleon scalar field
International Nuclear Information System (INIS)
Setare, M.R.; Jamil, Mubasher
2010-01-01
We study a cosmological implication of holographic dark energy in the Brans-Dicke gravity. We employ the holographic model of dark energy to obtain the equation of state for the holographic energy density in non-flat (closed) universe enclosed by the event horizon measured from the sphere of horizon named L. Our analysis shows that one can obtain the phantom crossing scenario if the model parameter α (of order unity) is tuned accordingly. Moreover, this behavior is achieved by treating the Brans-Dicke scalar field as a Chameleon scalar field and taking a non-minimal coupling of the scalar field with matter. Hence one can generate phantom-like equation of state from a holographic dark energy model in non-flat universe in the Brans-Dicke cosmology framework.
Acceleration-enlarged symmetries in nonrelativistic space-time with a cosmological constant TH1"-->
Lukierski, J.; Stichel, P. C.; Zakrzewski, W. J.
2008-05-01
By considering the nonrelativistic limit of de Sitter geometry one obtains the nonrelativistic space-time with a cosmological constant and Newton Hooke (NH) symmetries. We show that the NH symmetry algebra can be enlarged by the addition of the constant acceleration generators and endowed with central extensions (one in any dimension (D) and three in D=(2+1)). We present a classical Lagrangian and Hamiltonian framework for constructing models quasi-invariant under enlarged NH symmetries that depend on three parameters described by three nonvanishing central charges. The Hamiltonian dynamics then splits into external and internal sectors with new noncommutative structures of external and internal phase spaces. We show that in the limit of vanishing cosmological constant the system reduces to the one, which possesses acceleration-enlarged Galilean symmetries.
Holographic dark energy in Brans-Dicke cosmology with chameleon scalar field
Energy Technology Data Exchange (ETDEWEB)
Setare, M.R., E-mail: rezakord@ipm.i [Department of Science of Bijar, University of Kurdistan, Bijar (Iran, Islamic Republic of); Jamil, Mubasher, E-mail: mjamil@camp.edu.p [Center for Advanced Mathematics and Physics, National University of Sciences and Technology, Rawalpindi 46000 (Pakistan)
2010-06-07
We study a cosmological implication of holographic dark energy in the Brans-Dicke gravity. We employ the holographic model of dark energy to obtain the equation of state for the holographic energy density in non-flat (closed) universe enclosed by the event horizon measured from the sphere of horizon named L. Our analysis shows that one can obtain the phantom crossing scenario if the model parameter {alpha} (of order unity) is tuned accordingly. Moreover, this behavior is achieved by treating the Brans-Dicke scalar field as a Chameleon scalar field and taking a non-minimal coupling of the scalar field with matter. Hence one can generate phantom-like equation of state from a holographic dark energy model in non-flat universe in the Brans-Dicke cosmology framework.
International Nuclear Information System (INIS)
Artymowski, Michał; Lewicki, Marek; Wells, James D.
2017-01-01
We consider various models realizing baryogenesis during the electroweak phase transition (EWBG). Our focus is their possible detection in future collider experiments and possible observation of gravitational waves emitted during the phase transition. We also discuss the possibility of a non-standard cosmological history which can facilitate EWBG. We show how acceptable parameter space can be extended due to such a modification and conclude that next generation precision experiments such as the ILC will be able to confirm or falsify many models realizing EWBG. We also show that, in general, collider searches are a more powerful probe than gravitational wave searches. However, observation of a deviation from the SM without any hints of gravitational waves can point to models with modified cosmological history that generically enable EWBG with weaker phase transition and thus, smaller GW signals.
Energy Technology Data Exchange (ETDEWEB)
Artymowski, Michał [Jagiellonian University,Łojasiewicza 11, 30-348 Kraków (Poland); Lewicki, Marek [Faculty of Physics, University of Warsaw,ul. Pasteura 5, 02-093 Warsaw (Poland); Michigan Center for Theoretical Physics, University of Michigan,Ann Arbor MI 48109 (United States); Wells, James D. [Michigan Center for Theoretical Physics, University of Michigan,Ann Arbor MI 48109 (United States); Deutsches Elektronen-Synchrotron DESY, Theory Group,D-22603 Hamburg (Germany)
2017-03-13
We consider various models realizing baryogenesis during the electroweak phase transition (EWBG). Our focus is their possible detection in future collider experiments and possible observation of gravitational waves emitted during the phase transition. We also discuss the possibility of a non-standard cosmological history which can facilitate EWBG. We show how acceptable parameter space can be extended due to such a modification and conclude that next generation precision experiments such as the ILC will be able to confirm or falsify many models realizing EWBG. We also show that, in general, collider searches are a more powerful probe than gravitational wave searches. However, observation of a deviation from the SM without any hints of gravitational waves can point to models with modified cosmological history that generically enable EWBG with weaker phase transition and thus, smaller GW signals.
The Cosmological Dependence of Galaxy Cluster Morphologies
Crone, Mary Margaret
1995-01-01
Measuring the density of the universe has been a fundamental problem in cosmology ever since the "Big Bang" model was developed over sixty years ago. In this simple and successful model, the age and eventual fate of the universe are determined by its density, its rate of expansion, and the value of a universal "cosmological constant". Analytic models suggest that many properties of galaxy clusters are sensitive to cosmological parameters. In this thesis, I use N-body simulations to examine cluster density profiles, abundances, and degree of subclustering to test the feasibility of using them as cosmological tests. The dependence on both cosmology and initial density field is examined, using a grid of cosmologies and scale-free initial power spectra P(k)~ k n. Einstein-deSitter ( Omegao=1), open ( Omegao=0.2 and 0.1) and flat, low density (Omegao=0.2, lambdao=0.8) models are studied, with initial spectral indices n=-2, -1 and 0. Of particular interest are the results for cluster profiles and substructure. The average density profiles are well fit by a power law p(r)~ r ^{-alpha} for radii where the local density contrast is between 100 and 3000. There is a clear trend toward steeper slopes with both increasing n and decreasing Omegao, with profile slopes in the open models consistently higher than Omega=1 values for the range of n examined. The amount of substructure in each model is quantified and explained in terms of cluster merger histories and the behavior of substructure statistics. The statistic which best distinguishes models is a very simple measure of deviations from symmetry in the projected mass distribution --the "Center-of-Mass Shift" as a function of overdensity. Some statistics which are quite sensitive to substructure perform relatively poorly as cosmological indicators. Density profiles and the Center-of-Mass test are both well-suited for comparison with weak lensing data and galaxy distributions. Such data are currently being collected and should
Quantum cosmology - science of Genesis
International Nuclear Information System (INIS)
Padmanabhan, Thanu
1987-01-01
Quantum cosmology, the marriage between the theories of the microscopic and macroscopic Universe, is examined in an attempt to explain the birth of the Universe in the 'big bang'. A quantum cosmological model of the Universe does not exist, but a rough approximation, or 'poor man's' version of quantum cosmology has been developed. The idea is to combine the theory of quantum mechanics with the classical cosmological solutions to obtain a quantum mechanical version of cosmology. Such a model of quantum cosmology is described -here the quantum universe behaves like a hydrogen atom with the Planck length replacing the Bohr radius. Properties of quantum cosmologies and the significance of the Planck length are both discussed. (UK)
Dynamic field theory and equations of motion in cosmology
Energy Technology Data Exchange (ETDEWEB)
Kopeikin, Sergei M., E-mail: kopeikins@missouri.edu [Department of Physics and Astronomy, University of Missouri, 322 Physics Bldg., Columbia, MO 65211 (United States); Petrov, Alexander N., E-mail: alex.petrov55@gmail.com [Sternberg Astronomical Institute, Lomonosov Moscow State University, Universitetskij Prospect 13, Moscow 119992 (Russian Federation)
2014-11-15
We discuss a field-theoretical approach based on general-relativistic variational principle to derive the covariant field equations and hydrodynamic equations of motion of baryonic matter governed by cosmological perturbations of dark matter and dark energy. The action depends on the gravitational and matter Lagrangian. The gravitational Lagrangian depends on the metric tensor and its first and second derivatives. The matter Lagrangian includes dark matter, dark energy and the ordinary baryonic matter which plays the role of a bare perturbation. The total Lagrangian is expanded in an asymptotic Taylor series around the background cosmological manifold defined as a solution of Einstein’s equations in the form of the Friedmann–Lemaître–Robertson–Walker (FLRW) metric tensor. The small parameter of the decomposition is the magnitude of the metric tensor perturbation. Each term of the series expansion is gauge-invariant and all of them together form a basis for the successive post-Friedmannian approximations around the background metric. The approximation scheme is covariant and the asymptotic nature of the Lagrangian decomposition does not require the post-Friedmannian perturbations to be small though computationally it works the most effectively when the perturbed metric is close enough to the background FLRW metric. The temporal evolution of the background metric is governed by dark matter and dark energy and we associate the large scale inhomogeneities in these two components as those generated by the primordial cosmological perturbations with an effective matter density contrast δρ/ρ≤1. The small scale inhomogeneities are generated by the condensations of baryonic matter considered as the bare perturbations of the background manifold that admits δρ/ρ≫1. Mathematically, the large scale perturbations are given by the homogeneous solution of the linearized field equations while the small scale perturbations are described by a particular solution of
International Nuclear Information System (INIS)
Brozda, J.
2006-01-01
Combustion of bituminous coal and lignite in power boilers brings into the atmosphere a lot of contaminations. The emission of pollutants can be reduced by the application of supercritical steam parameters, which also improves the efficiency of power units, but in that case constructional materials of the new generation are needed, among them austenitic steels. The development of power units with supercritical and ultra supercritical steam parameters is presented as well as applied structural materials. Austenitic steels used in power boiler constructions are listed. Basic characteristics of austenitic steels of the new generation are given and principles of their forming and welding. (author)
Cosmological attractors in massive gravity
Dubovsky, S; Tkachev, I I
2005-01-01
We study Lorentz-violating models of massive gravity which preserve rotations and are invariant under time-dependent shifts of the spatial coordinates. In the linear approximation the Newtonian potential in these models has an extra ``confining'' term proportional to the distance from the source. We argue that during cosmological expansion the Universe may be driven to an attractor point with larger symmetry which includes particular simultaneous dilatations of time and space coordinates. The confining term in the potential vanishes as one approaches the attractor. In the vicinity of the attractor the extra contribution is present in the Friedmann equation which, in a certain range of parameters, gives rise to the cosmic acceleration.
Cosmological tests of general relativity
International Nuclear Information System (INIS)
Hut, P.
1977-01-01
It is stated that the general relativity theory could be tested on a cosmological scale by measuring the Hubble constant and the deceleration parameter, if, in addition, everything could be known about the matter filling the universe. If, on the other hand, nothing could be presupposed about the matter content of the universe general relativity could not be tested by measuring any number of time derivatives of the scale factor. But upon making the assumption of a universe filled with non-interacting mixture of non-relativistic matter and radiation general relativity can in principle be tested by measuring the first five derivatives of the scale factor. Some general relations are here presented using this assumption. (author)
Directory of Open Access Journals (Sweden)
Gasparjans Aleksandrs
2015-07-01
Full Text Available A method of technical diagnostics of ship diesel engine – generator installation – is proposed. Spectral-power diagnostic parameters of the synchronous generator voltage and currents are used. The electric machine in this case is the multipurpose sensor of diagnostic parameters. A judgment on the quality of the operational processes in diesel engine cylinders and its technical condition is possible on the basis of these parameters. This method is applicable to piston compressor installations with electric drive. On the basis of such parameters as rotating torque, angular speed and angular acceleration it is possible to estimate the quality of the operating process in the cylinders of a diesel engine, the condition of its cylinder-piston group and the crank gear mechanism. The investigation was realized on the basis of a diesel-generator with linear load. The generator operation was considered for the case of constant RL load. Together with the above mentioned, the condition of bearings of synchronous machines, uniformity of the air gap, windings of the electric machine were estimated during the experiments as well. The frequency spectrum of the stator current of the generator was researched and analyzed. In this case the synchronous machine is becoming a rather exact multipurpose diagnostic sensor. The signal of non-uniformity in the operation process of diesel engine cylinders and its technical condition is the increasing of the amplitudes of typical frequencies.
Where does cosmological perturbation theory break down?
International Nuclear Information System (INIS)
Armendariz-Picon, Cristian; Fontanini, Michele; Penco, Riccardo; Trodden, Mark
2009-01-01
It is often assumed that initial conditions for the evolution of a cosmological mode should be set at the time its physical wavelength reaches a cut-off of the order of the Planck length. Beyond that scale, trans-Planckian corrections to the dispersion relation are supposed to become dominant, leading to the breakdown of cosmological perturbation theory. In this paper, we apply the effective field theory approach to the coupled metric-inflaton system in order to calculate the corrections to the power spectrum of scalar and tensor perturbations induced by higher-dimension operators at short wavelengths. These corrections can be interpreted as modifications of the dispersion relation, and thus open a window to probe the validity of cosmological perturbation theory. Both for scalars and tensors, the modifications become important when the Hubble parameter is of the order of the Planck mass, or when the physical wave number of a cosmological perturbation mode approaches the square of the Planck mass divided by the Hubble constant. Thus, the cut-off length at which such a breakdown occurs is finite, but much smaller than the Planck length.
Cosmological constraints on Brans-Dicke theory.
Avilez, A; Skordis, C
2014-07-04
We report strong cosmological constraints on the Brans-Dicke (BD) theory of gravity using cosmic microwave background data from Planck. We consider two types of models. First, the initial condition of the scalar field is fixed to give the same effective gravitational strength Geff today as the one measured on Earth, GN. In this case, the BD parameter ω is constrained to ω>692 at the 99% confidence level, an order of magnitude improvement over previous constraints. In the second type, the initial condition for the scalar is a free parameter leading to a somewhat stronger constraint of ω>890, while Geff is constrained to 0.981theory and are valid for any Horndeski theory, the most general second-order scalar-tensor theory, which approximates the BD theory on cosmological scales. In this sense, our constraints place strong limits on possible modifications of gravity that might explain cosmic acceleration.
Seeding black holes in cosmological simulations
Taylor, P.; Kobayashi, C.
2014-08-01
We present a new model for the formation of black holes in cosmological simulations, motivated by the first star formation. Black holes form from high density peaks of primordial gas, and grow via both gas accretion and mergers. Massive black holes heat the surrounding material, suppressing star formation at the centres of galaxies, and driving galactic winds. We perform an investigation into the physical effects of the model parameters, and obtain a `best' set of these parameters by comparing the outcome of simulations to observations. With this best set, we successfully reproduce the cosmic star formation rate history, black hole mass-velocity dispersion relation, and the size-velocity dispersion relation of galaxies. The black hole seed mass is ˜103 M⊙, which is orders of magnitude smaller than that which has been used in previous cosmological simulations with active galactic nuclei, but suggests that the origin of the seed black holes is the death of Population III stars.
International Nuclear Information System (INIS)
2006-01-01
This year's Nobel prize is welcome recognition for cosmology. Back in the 1960s, according to Paul Davies' new book The Goldilocks Enigma (see 'Seeking anthropic answers' in this issue), cynics used to quip that there is 'speculation, speculation squared - and cosmology'. Anyone trying to understand the origin and fate of the universe was, in other words, dealing with questions that were simply impractical - or even impossible - to answer. But that has all changed with the development of new telescopes, satellites and data-processing techniques - to the extent that cosmology is now generally viewed as a perfectly acceptable branch of science. If anyone was in any doubt of cosmology's new status, the Royal Swedish Academy of Sciences last month gave the subject welcome recognition with the award of this year's Nobel prize to John Mather and George Smoot (see pp6-7; print version only). The pair were the driving force behind the COBE satellite that in 1992 produced the now famous image of the cosmic microwave background. The mission's data almost certainly proved that the universe started with a Big Bang, while tiny fluctuations in the temperature signal between different parts of the sky were shown to be the seeds of the stars and galaxies we see today. These results are regarded by many as the start of a new era of 'precision cosmology'. But for cosmologists, the job is far from over. There are still massive holes in our understanding of the cosmos, notably the nature of dark matter and dark energy, which together account for over 95% of the total universe. Indeed, some regard dark energy and matter as just ad hoc assumptions needed to fit the data. (Hypothetical particles called 'axions' are one possible contender for dark matter (see pp20-23; print version only), but don't bet your house on it.) Some physicists even think it makes more sense to adjust Newtonian gravity rather than invoke dark matter. But the notion that cosmology is in crisis, as argued by some
Cosmology with torsion: An alternative to cosmic inflation
International Nuclear Information System (INIS)
Poplawski, Nikodem J.
2010-01-01
We propose a simple scenario which explains why our Universe appears spatially flat, homogeneous and isotropic. We use the Einstein-Cartan-Kibble-Sciama (ECKS) theory of gravity which naturally extends general relativity to include the spin of matter. The torsion of spacetime generates gravitational repulsion in the early Universe filled with quarks and leptons, preventing the cosmological singularity: the Universe expands from a state of minimum but finite radius. We show that the dynamics of the closed Universe immediately after this state naturally solves the flatness and horizon problems in cosmology because of an extremely small and negative torsion density parameter, Ω S ∼-10 -69 . Thus the ECKS gravity provides a compelling alternative to speculative mechanisms of standard cosmic inflation. This scenario also suggests that the contraction of our Universe preceding the bounce at the minimum radius may correspond to the dynamics of matter inside a collapsing black hole existing in another universe, which could explain the origin of the Big Bang.
Local cosmology of the solar system
Bel, Ll.
2010-01-01
A time-dependent model of space-time is used to describe the gravitational field of the sun. This model is a spherically symmetric approximate solution of Einstein's equations in vacuum. Near the sun it approximates one of the models derived from the Schwarzschild solution, while at large distances it becomes a milne's-like zero space-time curvature model. Two local cosmology free parameters provide simple descriptions for the secular increasing of the astronomical unit, as well as the "anoma...
Bouncing cosmologies from quantum gravity condensates
Oriti, Daniele; Sindoni, Lorenzo; Wilson-Ewing, Edward
2017-02-01
We show how the large-scale cosmological dynamics can be obtained from the hydrodynamics of isotropic group field theory condensate states in the Gross-Pitaevskii approximation. The correct Friedmann equations are recovered in the classical limit for some choices of the parameters in the action for the group field theory, and quantum gravity corrections arise in the high-curvature regime causing a bounce which generically resolves the big-bang and big-crunch singularities.
Classical Cosmology Through Animation Stories
Mijic, Milan; Kang, E. Y. E.; Longson, T.; State LA SciVi Project, Cal
2010-05-01
Computer animations are a powerful tool for explanation and communication of ideas, especially to a younger generation. Our team completed a three part sequence of short, computer animated stories about the insight and discoveries that lead to the understanding of the overall structure of the universe. Our principal characters are Immanuel Kant, Henrietta Leavitt, and Edwin Hubble. We utilized animations to model and visualize the physical concepts behind each discovery and to recreate the characters, locations, and flavor of the time. The animations vary in length from 6 to 11 minutes. The instructors or presenters may wish to utilize them separately or together. The animations may be used for learning classical cosmology in a visual way in GE astronomy courses, in pre-college science classes, or in public science education setting.
International Nuclear Information System (INIS)
Faizal, Mir
2012-01-01
In this paper, we construct a model for group field cosmology. The classical equations of motion for the non-interactive part of this model generate the Hamiltonian constraint of loop quantum gravity for a homogeneous isotropic universe filled with a scalar matter field. The interactions represent topology changing processes that occur due to joining and splitting of universes. These universes in the multiverse are assumed to obey both bosonic and fermionic statistics, and so a supersymmetric multiverse is constructed using superspace formalism. We also introduce gauge symmetry in this model. The supersymmetry and gauge symmetry are introduced at the level of third quantized fields, and not the second quantized ones. This is the first time that supersymmetry has been discussed at the level of third quantized fields. (paper)
An Introduction to General Relativity and Cosmology
International Nuclear Information System (INIS)
Wainwright, John
2007-01-01
inflation scenario, arguing that the problems that it aims to solve (the so-called horizon problem and the flatness problem) are a consequence of the very special geometry of the FL models. In particular, the flatness problem loses its urgency when one broadens the class of cosmological models, since the condition for flatness depends on spatial position. They also discuss in detail an analysis due to Celerier and Schneider showing how the horizon problem can be resolved using a delayed big-bang singularity in a Lemaitre-Tolman cosmology. We comment on two notable omissions as regards cosmology. First, the authors only refer in passing to the notion of the density parameter, which plays an important role in the analysis of the FL models, and which can also be introduced in more general models. Second, there is no discussion of perturbations of the FL models, although two related concepts, the density contrast and the curvature contrast, are analysed in the Lemaitre-Tolman models. A second unusual feature is that there is a considerable emphasis on exact solutions, their derivation and physical interpretation. Derivations that are given in detail are for the spatially homogeneous solution of Bianchi type I with pressure-free matter, the Lemaitre-Tolman solutions, the Szekeres solutions and the Kerr solution (the original derivation using the Kerr-Schild metric, and Carter's derivation using separability of the Klein-Gordon equation). Readers may wish to compare the above-mentioned derivation of the Bianchi type I solutions, which uses metric components and coordinates, with the derivation given, using the orthonormal frame formalism. In summary, this book is an interesting and informative introduction to general relativity and cosmology. The unconventional choice of topics and emphasis may, however, lead some readers to conclude that it may be more suitable as a reference work than as the text for a course. (book review)
A critical review of classical bouncing cosmologies
Energy Technology Data Exchange (ETDEWEB)
Battefeld, Diana, E-mail: dbattefe@astro.physik.uni-goettingen.de [Institut for Astrophysics, University of Goettingen, Friedrich-Hund Platz 1, D-37077 (Germany); Peter, Patrick, E-mail: peter@iap.fr [Institut d’Astrophysique de Paris, UMR 7095-CNRS, Université Pierre et Marie Curie, 98 bis boulevard Arago, 75014 Paris (France)
2015-04-01
Given the proliferation of bouncing models in recent years, we gather and critically assess these proposals in a comprehensive review. The PLANCK data shows an unmistakably red, quasi scale-invariant, purely adiabatic primordial power spectrum and no primary non-Gaussianities. While these observations are consistent with inflationary predictions, bouncing cosmologies aspire to provide an alternative framework to explain them. Such models face many problems, both of the purely theoretical kind, such as the necessity of violating the NEC and instabilities, and at the cosmological application level, as exemplified by the possible presence of shear. We provide a pedagogical introduction to these problems and also assess the fitness of different proposals with respect to the data. For example, many models predict a slightly blue spectrum and must be fine-tuned to generate a red spectral index; as a side effect, large non-Gaussianities often result. We highlight several promising attempts to violate the NEC without introducing dangerous instabilities at the classical and/or quantum level. If primordial gravitational waves are observed, certain bouncing cosmologies, such as the cyclic scenario, are in trouble, while others remain valid. We conclude that, while most bouncing cosmologies are far from providing an alternative to the inflationary paradigm, a handful of interesting proposals have surfaced, which warrant further research. The constraints and lessons learned as laid out in this review might guide future research.
Cosmological reconstruction and Om diagnostic analysis of Einstein-Aether theory
Energy Technology Data Exchange (ETDEWEB)
Pasqua, Antonio [Department of Physics, University of Trieste, Via Valerio 2, 34127 Trieste (Italy); Chattopadhyay, Surajit [Pailan College of Management and Technology, Bengal Pailan Park, Kolkata-700 104 (India); Momeni, Davood; Myrzakulov, Ratbay [Eurasian International Center for Theoretical Physics and Department of General and Theoretical Physics, Eurasian National University, Astana 010008 (Kazakhstan); Raza, Muhammad [Department of Mathematics, COMSATS Institute of Information Technology, Sahiwal 57000 (Pakistan); Faizal, Mir, E-mail: toto.pasqua@gmail.com, E-mail: surajcha@iucaa.ernet.in, E-mail: d.momeni@yahoo.com, E-mail: mraza@zju.edu.cn, E-mail: rmyrzakulov@gmail.com, E-mail: mirfaizalmir@gmail.com [Irving K. Barber School of Arts and Sciences, University of British Columbia—Okanagan, Kelowna, British Columbia V1V 1V7 (Canada)
2017-04-01
In this paper, we analyze the cosmological models in Einstein-Aether gravity, which is a modified theory of gravity in which a time-like vector field breaks the Lorentz symmetry. We use this formalism to analyse different cosmological models with different behavior of the scale factor. In this analysis, we use a certain functional dependence of the Dark Energy (DE) on the Hubble parameter H . It will be demonstrated that the Aether vector field has a non-trivial effect on these cosmological models. We also perform the Om diagnostic in Einstein-Aether gravity and we fit the parameters of the cosmological models using recent observational data.
Physically self-consistent basis for modern cosmology
International Nuclear Information System (INIS)
Khlopov, M.Yu.
2000-01-01
Cosmoparticle physics appeared as a natural result of internal development of cosmology seeking physical grounds for inflation, baryosynthesis, and nonbaryonic dark matter and of particle physics going outside the Standard Model of particle interactions. Its aim is to study the foundations of particle physics and cosmology and their fundamental relationship in the combination of respective indirect cosmological, astrophysical, and physical effects. The ideas on new particles and fields predicted by particle theory and on their cosmological impact are discussed, as well as the methods of cosmoparticle physics to probe these ideas, are considered with special analysis of physical mechanisms for inflation, baryosynthesis, and nonbaryonic dark matter. These mechanisms are shown to reflect the main principle of modern cosmology, putting, instead of formal parameters of cosmological models, physical processes governing the evolution of the big-bang universe. Their realization on the basis of particle theory induces additional model-dependent predictions, accessible to various methods of nonaccelerator particle physics. Probes for such predictions, with the use of astrophysical data, are the aim of cosmoarcheology studying astrophysical effects of new physics. The possibility of finding quantitatively definite relationships between cosmological and laboratory effects on the basis of cosmoparticle approach, as well as of obtaining a unique solution to the problem of physical candidates for inflation, mechanisms of baryogenesis, and multicomponent dark matter, is exemplified in terms of gauge model with broken family symmetry, underlying horizontal unification and possessing quantitatively definite physical grounds for inflation, baryosynthesis, and effectively multicomponent dark-matter scenarios
The Hubble IR cutoff in holographic ellipsoidal cosmologies
Energy Technology Data Exchange (ETDEWEB)
Cataldo, Mauricio [Universidad del Bio-Bio, Departamento de Fisica, Facultad de Ciencias, Concepcion (Chile); Cruz, Norman [Grupo de Cosmologia y Gravitacion-UBB, Concepcion (Chile)
2018-01-15
It is well known that for spatially flat FRW cosmologies, the holographic dark energy disfavors the Hubble parameter as a candidate for the IR cutoff. For overcoming this problem, we explore the use of this cutoff in holographic ellipsoidal cosmological models, and derive the general ellipsoidal metric induced by a such holographic energy density. Despite the drawbacks that this cutoff presents in homogeneous and isotropic universes, based on this general metric, we developed a suitable ellipsoidal holographic cosmological model, filled with a dark matter and a dark energy components. At late time stages, the cosmic evolution is dominated by a holographic anisotropic dark energy with barotropic equations of state. The cosmologies expand in all directions in accelerated manner. Since the ellipsoidal cosmologies given here are not asymptotically FRW, the deviation from homogeneity and isotropy of the universe on large cosmological scales remains constant during all cosmic evolution. This feature allows the studied holographic ellipsoidal cosmologies to be ruled by an equation of state ω = p/ρ, whose range belongs to quintessence or even phantom matter. (orig.)
Towards a superstring cosmology
International Nuclear Information System (INIS)
Taylor, J.G.
1987-01-01
If superstring theory is a theory of everything then it must give a satisfactory description of the very early evolution of the universe. Since the very early universe is not directly observable, then by satisfactory it is mean that the later evolution following the earlier (pre-Planck time era) phase leads to agreement with prediction for the various observable phenomena such as (B-bar B), inflation, galaxy structure, the cosmological constant (infimum), etc. Moreover it is to be hoped that the initial singularity of classical general relativistic cosmology is also avoided. It is clear that superstring theory is not yet able to tackle these problems. This paper describes what has been done so far to construct very simplified versions of string theory relevant to the early universe, and discusses the critical questions still to be answered
Nonlocal teleparallel cosmology.
Bahamonde, Sebastian; Capozziello, Salvatore; Faizal, Mir; Nunes, Rafael C
2017-01-01
Even though it is not possible to differentiate general relativity from teleparallel gravity using classical experiments, it could be possible to discriminate between them by quantum gravitational effects. These effects have motivated the introduction of nonlocal deformations of general relativity, and similar effects are also expected to occur in teleparallel gravity. Here, we study nonlocal deformations of teleparallel gravity along with its cosmological solutions. We observe that nonlocal teleparallel gravity (like nonlocal general relativity) is consistent with the present cosmological data obtained by SNe Ia + BAO + CC + [Formula: see text] observations. Along this track, future experiments probing nonlocal effects could be used to test whether general relativity or teleparallel gravity gives the most consistent picture of gravitational interaction.
Bojowald, Martin
2015-02-01
In quantum cosmology, one applies quantum physics to the whole universe. While no unique version and no completely well-defined theory is available yet, the framework gives rise to interesting conceptual, mathematical and physical questions. This review presents quantum cosmology in a new picture that tries to incorporate the importance of inhomogeneity. De-emphasizing the traditional minisuperspace view, the dynamics is rather formulated in terms of the interplay of many interacting 'microscopic' degrees of freedom that describe the space-time geometry. There is thus a close relationship with more-established systems in condensed-matter and particle physics even while the large set of space-time symmetries (general covariance) requires some adaptations and new developments. These extensions of standard methods are needed both at the fundamental level and at the stage of evaluating the theory by effective descriptions.
Elementary particles and cosmology
International Nuclear Information System (INIS)
Audouze, J.; Paty, M.
2000-01-01
The universe is the most efficient laboratory of particle physics and the understanding of cosmological processes implies the knowledge of how elementary particles interact. This article recalls the mutual influences between on the one hand: astrophysics and cosmology and on the other hand: nuclear physics and particle physics. The big-bang theory relies on nuclear physics to explain the successive stages of nucleo-synthesis and the study of solar neutrinos has led to discover new aspects of this particle: it is likely that neutrinos undergo oscillations from one neutrino type to another. In some universe events such as the bursting of a super-nova, particles are released with a kinetic energy that would be impossible to reach on earth with a particle accelerator. These events are become common points of interest between astrophysicists and particle physicists and have promoted a deeper cooperation between astrophysics and elementary particle physics. (A.C.)
Nonlocal teleparallel cosmology
Energy Technology Data Exchange (ETDEWEB)
Bahamonde, Sebastian [University College London, Department of Mathematics, London (United Kingdom); Capozziello, Salvatore [Universita di Napoli ' ' Federico II' ' , Dipartimento di Fisica ' ' E. Pancini' ' , Naples (Italy); Gran Sasso Science Institute, L' Aquila (Italy); Compl. Univ. di Monte S. Angelo, Naples (Italy); INFN, Napoli (Italy); Faizal, Mir [University of British Columbia - Okanagan, Irving K. Barber School of Arts and Sciences, Kelowna, BC (Canada); University of Lethbridge, Department of Physics and Astronomy, Lethbridge, AB (Canada); Nunes, Rafael C. [Universidade Federal de Juiz de Fora, Departamento de Fisica, Juiz de Fora, MG (Brazil)
2017-09-15
Even though it is not possible to differentiate general relativity from teleparallel gravity using classical experiments, it could be possible to discriminate between them by quantum gravitational effects. These effects have motivated the introduction of nonlocal deformations of general relativity, and similar effects are also expected to occur in teleparallel gravity. Here, we study nonlocal deformations of teleparallel gravity along with its cosmological solutions. We observe that nonlocal teleparallel gravity (like nonlocal general relativity) is consistent with the present cosmological data obtained by SNe Ia + BAO + CC + H{sub 0} observations. Along this track, future experiments probing nonlocal effects could be used to test whether general relativity or teleparallel gravity gives the most consistent picture of gravitational interaction. (orig.)
International Nuclear Information System (INIS)
Padmanabhan, T.
1989-01-01
Quantum cosmology is to quantum gravity what the Bohr model is to the full quantum mechanical description of the hydrogen atom. In quantum cosmology one attempts to give a quantum-mechanical meaning to classical solutions of general relativity. This is discussed in this chapter. The approach is illustrated by quantizing only the conformal degree of freedom of the gravitational field, in particular the Friedmann-Robertson-Walker models. And, as in the hydrogen atom, the classical singularity of general relativity is avoided and one has analogous stationary states in the quantum Universe. The chapter ends with a model of the fundamental role that the Planck length may play as the universal cutoff in all field theories, thus ridding the theory of ultra-violet divergences. Two appendices introduce field theory in the Schroedinger representation and the Schroedinger equation for quantum gravity, namely the Wheeler-De Wit equation. (author). 38 refs.; 2 figs.; 1 tab
Massive neutrinos and cosmology
International Nuclear Information System (INIS)
Shandarin, S.F.
1991-01-01
This paper discussed the importance of the consequences of a nonzero neutrino rest mass on cosmology, perhaps, first recognized by Gershtein and Zeldovich, after the discover of the 3-K microwave background radiation MBR. Since the first works on the primordial synthesis of 4 He, it has been known that additional neutrino species increase the rate of expansion of the universe during the epoch of the primordial nucleosynthesis, which increases the yield of 4 He. Combining the results of the theory with astronomical measurements of the 4 He abundance and the estimate of the mass density of MBR, Shvartsman suggested the upper limit on the mass density of all relativistic matter at that epoch: ρ rel ≤ 5ρ MBR which eventually became the upper limit for the number of neutrino species: N ν ≤ 7. At that time, the constraints based on cosmological arguments were much stronger than one based on laboratory experiments
Merritt, David
2017-02-01
I argue that some important elements of the current cosmological model are 'conventionalist' in the sense defined by Karl Popper. These elements include dark matter and dark energy; both are auxiliary hypotheses that were invoked in response to observations that falsified the standard model as it existed at the time. The use of conventionalist stratagems in response to unexpected observations implies that the field of cosmology is in a state of 'degenerating problemshift' in the language of Imre Lakatos. I show that the 'concordance' argument, often put forward by cosmologists in support of the current paradigm, is weaker than the convergence arguments that were made in the past in support of the atomic theory of matter or the quantization of energy.
Cosmology, inflation, and supersymmetry
International Nuclear Information System (INIS)
Albrecht, A.; Dimopoulos, S.; Fischler, W.; Kolb, E.W.; Raby, S.; Steinhardt, P.J.
1982-01-01
Cosmological consequences of supersymmetric grand unified models based on the Witten-O'Raifeartaigh potential are discussed. In particular we study the development of the phase transition in the spontaneous breaking of supersymmetry. We find that in realistic models where light fields feel supersymmetry breaking only through coupling to massive fields, e.g., the Geometric Hierarchy model, the universe does not inflate or reheat. Thus, the standard cosmological flatness, monopole, and horizon problems remain. In addition, we find that the transition is never completed, in the sense that the universe remains dominated by coherent Higgs field energy, resulting in an apparent matter dominated universe with Ω greater than or equal to 10 30
Constraints on cosmological birefringence energy dependence from CMB polarization data
International Nuclear Information System (INIS)
Gubitosi, G.; Paci, F.
2013-01-01
We study the possibility of constraining the energy dependence of cosmological birefringence by using CMB polarization data. We consider four possible behaviors, characteristic of different theoretical scenarios: energy-independent birefringence motivated by Chern-Simons interactions of the electromagnetic field, linear energy dependence motivated by a 'Weyl' interaction of the electromagnetic field, quadratic energy dependence, motivated by quantum gravity modifications of low-energy electrodynamics, and inverse quadratic dependence, motivated by Faraday rotation generated by primordial magnetic fields. We constrain the parameters associated to each kind of dependence and use our results to give constraints on the models mentioned. We forecast the sensitivity that Planck data will be able to achieve in this respect
Cosmological constraints with clustering-based redshifts
Kovetz, Ely D.; Raccanelli, Alvise; Rahman, Mubdi
2017-07-01
We demonstrate that observations lacking reliable redshift information, such as photometric and radio continuum surveys, can produce robust measurements of cosmological parameters when empowered by clustering-based redshift estimation. This method infers the redshift distribution based on the spatial clustering of sources, using cross-correlation with a reference data set with known redshifts. Applying this method to the existing Sloan Digital Sky Survey (SDSS) photometric galaxies, and projecting to future radio continuum surveys, we show that sources can be efficiently divided into several redshift bins, increasing their ability to constrain cosmological parameters. We forecast constraints on the dark-energy equation of state and on local non-Gaussianity parameters. We explore several pertinent issues, including the trade-off between including more sources and minimizing the overlap between bins, the shot-noise limitations on binning and the predicted performance of the method at high redshifts, and most importantly pay special attention to possible degeneracies with the galaxy bias. Remarkably, we find that once this technique is implemented, constraints on dynamical dark energy from the SDSS imaging catalogue can be competitive with, or better than, those from the spectroscopic BOSS survey and even future planned experiments. Further, constraints on primordial non-Gaussianity from future large-sky radio-continuum surveys can outperform those from the Planck cosmic microwave background experiment and rival those from future spectroscopic galaxy surveys. The application of this method thus holds tremendous promise for cosmology.