BB mode angular power spectrum of CMB from massive gravity
Malsawmtluangi, N
2016-01-01
The primordial massive gravitational waves are placed in the squeezed vacuum state and corresponding $BB$-mode correlation angular power spectrum of the cosmic microwave background is obtained for various slow roll inflation models. The angular power spectrum is compared with the limit of BICEP2/Keck and Planck joint analysis data and the hybrid inflation model is found favorable.
Templates for the Sunyaev-Zel'dovich Angular Power Spectrum
Trac, Hy; Ostriker, Jeremiah P
2010-01-01
We present templates for the Sunyaev-Zel'dovich (SZ) angular power spectrum based on four models for the nonlinear gas distribution. The frequency-dependent SZ temperature fluctuations, with thermal (TSZ) and kinetic (KSZ) contributions, are calculated by tracing through a dark matter simulation, processed to include gas in dark matter halos and in the filamentary intergalactic medium. Different halo gas models are compared to study how star formation, energetic feedback, and nonthermal pressure support influence the angular power spectrum. The standard model has been calibrated to reproduce the stellar and gas fractions and X-ray scaling relations measured from low redshift clusters and groups. The other models illustrate the current theoretical and empirical uncertainties relating to properties of the intracluster medium. Relative to the standard model, their angular power spectra differ by approximately 50% (TSZ), 20% (KSZ), and 40% (SZ at 148 GHz) for l=3000, sigma_8=0.8, and homogeneous reionization at z...
Constraints on massive neutrinos from the CFHTLS angular power spectrum
Xia, Jun-Qing [Scuola Internazionale Superiore di Studi Avanzati, Via Bonomea 265, I-34136 Trieste (Italy); Granett, Benjamin R.; Guzzo, Luigi [INAF — Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Brera (Italy); Viel, Matteo [INAF — Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, I-34131 Trieste (Italy); Bird, Simeon [School of Natural Sciences, Institute for Advanced Study, Princeton, NJ 08540 (United States); Haehnelt, Martin G. [Institute of Astronomy and Kavli Institute for Cosmology, Madingley Road, CB3 0HA, Cambridge (United Kingdom); Coupon, Jean [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); McCracken, Henry Joy; Mellier, Yannick, E-mail: xia@sissa.it, E-mail: ben.granett@brera.inaf.it, E-mail: viel@oats.inaf.it, E-mail: spb@ias.edu, E-mail: luigi.guzzo@brera.inaf.it, E-mail: haehnelt@ast.cam.ac.uk, E-mail: coupon@asiaa.sinica.edu.tw, E-mail: hjmcc@iap.fr, E-mail: mellier@iap.fr [Institut d' Astrophysique de Paris, UMR 7095 CNRS, Universitè Pierre et Marie Curie, 98 bis Boulevard Arago, 75014 Paris (France)
2012-06-01
We use the galaxy angular power spectrum at z ∼ 0.5–1.2 from the Canada-France-Hawaii-Telescope Legacy Survey Wide fields (CFHTLS-Wide) to constrain separately the total neutrino mass Σm{sub ν} and the effective number of neutrino species N{sub eff}. This survey has recently benefited from an accurate calibration of the redshift distribution, allowing new measurements of the (non-linear) matter power spectrum in a unique range of scales and redshifts sensitive to neutrino free streaming. Our analysis makes use of a recent model for the effect of neutrinos on the weakly non-linear matter power spectrum derived from accurate N-body simulations. We show that CFHTLS, combined with WMAP7 and a prior on the Hubble constant provides an upper limit of Σm{sub ν} < 0.29 eV and N{sub eff} = 4.17{sup +1.62}{sub −1.26} (2 σ confidence levels). If we omit smaller scales which may be affected by non-linearities, these constraints become Σm{sub ν} < 0.41 eV and N{sub eff} = 3.98{sup +2.02}{sub −1.20} (2 σ confidence levels). Finally we show that the addition of other large scale structures probes can further improve these constraints, demonstrating that high redshift large volumes surveys such as CFHTLS are complementary to other cosmological probes of the neutrino mass.
Analytical model for CMB temperature angular power spectrum from cosmic (super-)strings
Yamauchi, Daisuke; Takahashi, Keitaro; Sendouda, Yuuiti; Yoo, Chul-Moon; Sasaki, Misao
2010-01-01
We present a new analytical method to calculate the small angle CMB temperature angular power spectrum due to cosmic (super-)string segments. In particular, using our method, we clarify the dependence on the intercommuting probability $P$. We find that the power spectrum is dominated by Poisson-distributed string segments. The power spectrum for a general value of $P$ has a plateau on large angular scales and shows a power-law decrease on small angular scales. The resulting spectrum in the ca...
Angular Power Spectrum in Modular Invariant Inflation Model
Hayashi, M J; Takami, T; Okame, Y; Takagi, K; Watanabe, T; Hayashi, Mitsuo J.; Hirai, Shiro; Takami, Tomoyuki; Okame, Yusuke; Takagi, Kenji; Watanabe, Tomoki
2006-01-01
We propose a scalar potential of inflation, motivated by the modular invariant supergravity and computed the angular power spectra of the adiabatic density perturbations. The potential consists of three scalar fields S, Y and T with the two free parameters. By fitting the parameters with the cosmological data at the fixed point T=1, we find the potential behaves as that of the single field S, which slowly rolls down along the minimized trajectory in Y and gives rise the sufficient inflation matching with the recent three-year WMAP data, e.g. the spectral index n_s = 0.951. The TT and TE angular power spectra obtained from our model almost completely coincides with the fitting of the LambdaCDM model. We conclude that our model is considered to be an adequate theory of inflation to explain the present data, although more theoritical foundation of the model should be required.
Angular Power Spectrum in Modular Invariant Inflation Model
A scalar potential of inflation is proposed and the angular power spectra of the adiabatic density perturbations are computed. The potential consists of three scalar fields, S, Y and T, together with two free parameters. By fitting the parameters to cosmological data at the fixed point T = 1, we find that the potential behaves like the single-field potential of S, which slowly rolls down. We further show that the inflation predictions corresponding to this potential provide a good fit to the recent three-year WMAP data, e.g. the spectral index ns = 0.951.The TT and TE angular power spectra obtained from our model almost completely coincide with the corresponding results obtained from the ΛCDM model. We conclude that our model is considered to be an adequate theory of inflation that explains the present data
Estimating the angular power spectrum of z > 2 BOSS QSOs using the MASTER method
Maldonado, Felipe; Huffenberger, Kevin; Rotti, Aditya
2016-01-01
We implement the MASTER method for angular power spectrum estimation and apply it to z > 2 quasars selected by the SDSS-III BOSS survey. Quasars are filtered for completeness and bad spectra, and include ~100,000 QSOs in the CORE sample and ~75,000 in the non-uniform BONUS sample. We estimate the angular power spectrum in redshift shells to constrain the matter power spectrum and quasar properties. In the future, we will jointly analyze overlapping Cosmic Microwave Background lensing maps from the Atacama Cosmology Telescope to place further constraints.
Using the CMB angular power spectrum to study Dark Matter-photon interactions
Wilkinson, Ryan J.; Boehm, Céline [Institute for Particle Physics Phenomenology, Durham University, South Road, Durham, DH1 3LE United Kingdom (United Kingdom); Lesgourgues, Julien, E-mail: ryan.wilkinson@durham.ac.uk, E-mail: julien.lesgourgues@cern.ch, E-mail: c.m.boehm@durham.ac.uk [Institut de Théorie des Phénomènes Physiques, École Polytechnique Fédérale de Lausanne, Lausanne, CH-1015 (Switzerland)
2014-04-01
In this paper, we explore the impact of Dark Matter-photon interactions on the CMB angular power spectrum. Using the one-year data release of the Planck satellite, we derive an upper bound on the Dark Matter-photon elastic scattering cross section of σ{sub DM−γ} ≤ 8 × 10{sup −31} (m{sub DM}/GeV) cm{sup 2} (68% CL) if the cross section is constant and a present-day value of σ{sub DM−γ} ≤ 6 × 10{sup −40}(m{sub DM}/GeV) cm{sup 2} (68% CL) if it scales as the temperature squared. For such a limiting cross section, both the B-modes and the TT angular power spectrum are suppressed with respect to ΛCDM predictions for ℓ∼>500 and ℓ∼>3000 respectively, indicating that forthcoming data from CMB polarisation experiments and Planck could help to constrain and characterise the physics of the dark sector. This essentially initiates a new type of dark matter search that is independent of whether dark matter is annihilating, decaying or asymmetric. Thus, any CMB experiment with the ability to measure the temperature and/or polarisation power spectra at high ℓ should be able to investigate the potential interactions of dark matter and contribute to our fundamental understanding of its nature.
Using the CMB angular power spectrum to study Dark Matter-photon interactions
In this paper, we explore the impact of Dark Matter-photon interactions on the CMB angular power spectrum. Using the one-year data release of the Planck satellite, we derive an upper bound on the Dark Matter-photon elastic scattering cross section of σDM−γ ≤ 8 × 10−31 (mDM/GeV) cm2 (68% CL) if the cross section is constant and a present-day value of σDM−γ ≤ 6 × 10−40(mDM/GeV) cm2 (68% CL) if it scales as the temperature squared. For such a limiting cross section, both the B-modes and the TT angular power spectrum are suppressed with respect to ΛCDM predictions for ℓ∼>500 and ℓ∼>3000 respectively, indicating that forthcoming data from CMB polarisation experiments and Planck could help to constrain and characterise the physics of the dark sector. This essentially initiates a new type of dark matter search that is independent of whether dark matter is annihilating, decaying or asymmetric. Thus, any CMB experiment with the ability to measure the temperature and/or polarisation power spectra at high ℓ should be able to investigate the potential interactions of dark matter and contribute to our fundamental understanding of its nature
Using the CMB angular power spectrum to study Dark Matter-photon interactions
Wilkinson, Ryan J; Boehm, Celine
2014-01-01
In this paper, we explore the impact of Dark Matter-photon interactions on the CMB angular power spectrum. Using the one-year data release of the Planck satellite, we derive an upper bound on the Dark Matter-photon elastic scattering cross section of sigma_{DM-photon} 500 and l > 3000 respectively, indicating that forthcoming data from CMB polarisation experiments and Planck could help to constrain and characterise the physics of the dark sector. This essentially initiates a new type of dark matter search that is independent of whether dark matter is annihilating, decaying or asymmetric. Thus, any CMB experiment with the ability to measure the temperature and/or polarisation power spectra at high l should be able to investigate the potential interactions of dark matter and contribute to our fundamental understanding of its nature.
Angular Power Spectrum and Dilatonic Inflation in Modular-Invariant Supergravity
Hayashi, M J; Okame, Y; Watanabe, T; Hayashi, Mitsuo J.; Hirai, Shiro; Okame, Yusuke; Watanabe, Tomoki
2006-01-01
The angular power spectrum is investigated in the model of supergravity, incorporating the target-space duality and the non-perturbative gaugino condensation in the hidden sector. The inflation and supersymmetry breaking occur at once by the interplay between the dilaton field as inflaton and the condensate gauge-singlet field. The model satisfies the slow-roll condition which solves the \\eta-problem. When the particle rolls down along the minimized trajectory of the potential at a duality invariant fixed point T=1, we can obtain the e-fold value \\sim 57. And then the cosmological parameters obtained from our model well match with the recent WMAP data combined with other experiments. The TT and TE angular power spectra also show that our model is compatible with the data for l > 20. However, the best fit value of \\tau in our model is smaller than that of the \\Lambda CDM model. These results suggest that, among supergravity models of inflation, the modular-invariant supergravity seems to open a hope to constru...
Angular power spectrum of sterile neutrino decay lines: the role of eROSITA
Zandanel, Fabio; Weniger, Christoph; Ando, Shin’ichiro
2016-05-01
We study the potential of the angular auto and cross-correlation power spectrum of the cosmic X-ray background in identifying sterile neutrino dark matter taking as reference the performances of the soon-to-be-launched eROSITA satellite. The main astrophysical background sources in this case are active galactic nuclei, galaxies powered by X-ray binaries, and clusters of galaxies. We show that while sterile neutrino decays are always subdominant in the autocorrelation power spectra, they can be efficiently enhanced when cross-correlating with tracers of the dark matter distribution. We estimate that the four-years eROSITA all-sky survey will potentially provide very stringent constraints on the sterile neutrino decay lifetime by cross-correlating the cosmic X-ray background with the 2MASS galaxy catalogue. This will allow to firmly test the recently claimed 3.56-keV X-ray line found towards several clusters and galaxies and its decaying dark matter interpretation. We finally stress that the main limitation of this approach is due to the shot noise of the galaxy catalogues used as tracers for the dark matter distribution, a limitation that we need to overcome to fully exploit the potential of the eROSITA satellite in this context.
Estimation of the angular power spectrum is one of the important steps in Cosmic Microwave Background (CMB) data analysis. Here, we present a nonparametric estimate of the temperature angular power spectrum for the Planck 2013 CMB data. The method implemented in this work is model-independent, and allows the data, rather than the model, to dictate the fit. Since one of the main targets of our analysis is to test the consistency of the ΛCDM model with Planck 2013 data, we use the nuisance parameters associated with the best-fit ΛCDM angular power spectrum to remove foreground contributions from the data at multipoles ℓ ≥50. We thus obtain a combined angular power spectrum data set together with the full covariance matrix, appropriately weighted over frequency channels. Our subsequent nonparametric analysis resolves six peaks (and five dips) up to ℓ ∼1850 in the temperature angular power spectrum. We present uncertainties in the peak/dip locations and heights at the 95% confidence level. We further show how these reflect the harmonicity of acoustic peaks, and can be used for acoustic scale estimation. Based on this nonparametric formalism, we found the best-fit ΛCDM model to be at 36% confidence distance from the center of the nonparametric confidence set—this is considerably larger than the confidence distance (9%) derived earlier from a similar analysis of the WMAP 7-year data. Another interesting result of our analysis is that at low multipoles, the Planck data do not suggest any upturn, contrary to the expectation based on the integrated Sachs-Wolfe contribution in the best-fit ΛCDM cosmology
Ruhl, J E; Bock, J J; Bond, J R; Borrill, J; Boscaleri, A; Contaldi, C R; Crill, B P; De Bernardis, P; De Troia, G; Ganga, K; Giacometti, M; Hivon, E; Hristov, V V; Iacoangeli, A; Jaffe, A H; Jones, W C; Lange, A E; Masi, S; Mason, P; Mauskopf, P D; Melchiorri, A; Montroy, T; Netterfield, C B; Pascale, E; Piacentini, F; Pogosyan, D; Polenta, G; Prunet, S; Romeo, G
2003-01-01
We report the most complete analysis to date of observations of the Cosmic Microwave Background (CMB) obtained during the 1998 flight of BOOMERANG. We use two quite different methods to determine the angular power spectrum of the CMB in 20 bands centered at l = 50 to 1000, applying them to 50% more data than has previously been analyzed. The power spectra produced by the two methods are in good agreement with each other, and constitute the most sensitive measurements to date over the range 300 < l < 1000. The increased precision of the power spectrum yields more precise determinations of several cosmological parameters than previous analyses of BOOMERANG data. The results continue to support an inflationary paradigm for the origin of the universe, being well fit by a 13.5 Gyr old, flat universe composed of approximately 5% baryonic matter, 30% cold dark matter, and 65% dark energy, with a scale invariant initial density perturbations.
van Engelen, A; Sehgal, N; Holder, G P; Zahn, O; Nagai, D
2013-01-01
The lensing power spectrum from cosmic microwave background (CMB) temperature maps will be measured with unprecedented precision with upcoming experiments, including upgrades to ACT and SPT. Achieving significant improvements in cosmological parameter constraints, such as percent level errors on sigma_8 and an uncertainty on the total neutrino mass of approximately 50 meV, requires percent level measurements of the CMB lensing power. This necessitates tight control of systematic biases. We study several types of biases to the temperature-based lensing reconstruction signal from foreground sources such as radio and infrared galaxies and the thermal Sunyaev-Zel'dovich effect from galaxy clusters. These foregrounds bias the CMB lensing signal due to their non-Gaussian nature. Using simulations as well as some analytical models we find that these sources can substantially impact the measured signal if left untreated. However, these biases can be brought to the percent level if one masks galaxies with fluxes at 15...
The lensing power spectrum from cosmic microwave background (CMB) temperature maps will be measured with unprecedented precision with upcoming experiments, including upgrades to the Atacama Cosmology Telescope and the South Pole Telescope. Achieving significant improvements in cosmological parameter constraints, such as percent level errors on σ8 and an uncertainty on the total neutrino mass of ∼50 meV, requires percent level measurements of the CMB lensing power. This necessitates tight control of systematic biases. We study several types of biases to the temperature-based lensing reconstruction signal from foreground sources such as radio and infrared galaxies and the thermal Sunyaev-Zel'dovich effect from galaxy clusters. These foregrounds bias the CMB lensing signal due to their non-Gaussian nature. Using simulations as well as some analytical models we find that these sources can substantially impact the measured signal if left untreated. However, these biases can be brought to the percent level if one masks galaxies with fluxes at 150 GHz above 1 mJy and galaxy clusters with masses above M vir = 1014 M ☉. To achieve such percent level bias, we find that only modes up to a maximum multipole of l max ∼ 2500 should be included in the lensing reconstruction. We also discuss ways to minimize additional bias induced by such aggressive foreground masking by, for example, exploring a two-step masking and in-painting algorithm.
Van Engelen, A.; Sehgal, N. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794 (United States); Bhattacharya, S. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Holder, G. P. [Department of Physics, McGill University, 3600 Rue University, Montreal, Quebec H3A 2T8 (Canada); Zahn, O. [Berkeley Center for Cosmological Physics, Department of Physics, University of California, and Lawrence Berkeley National Labs, Berkeley, CA 94720 (United States); Nagai, D. [Department of Physics, Department of Astronomy and Yale Center for Astronomy and Astrophysics, Yale University, New Haven, CT 06520 (United States)
2014-05-01
The lensing power spectrum from cosmic microwave background (CMB) temperature maps will be measured with unprecedented precision with upcoming experiments, including upgrades to the Atacama Cosmology Telescope and the South Pole Telescope. Achieving significant improvements in cosmological parameter constraints, such as percent level errors on σ{sub 8} and an uncertainty on the total neutrino mass of ∼50 meV, requires percent level measurements of the CMB lensing power. This necessitates tight control of systematic biases. We study several types of biases to the temperature-based lensing reconstruction signal from foreground sources such as radio and infrared galaxies and the thermal Sunyaev-Zel'dovich effect from galaxy clusters. These foregrounds bias the CMB lensing signal due to their non-Gaussian nature. Using simulations as well as some analytical models we find that these sources can substantially impact the measured signal if left untreated. However, these biases can be brought to the percent level if one masks galaxies with fluxes at 150 GHz above 1 mJy and galaxy clusters with masses above M {sub vir} = 10{sup 14} M {sub ☉}. To achieve such percent level bias, we find that only modes up to a maximum multipole of l {sub max} ∼ 2500 should be included in the lensing reconstruction. We also discuss ways to minimize additional bias induced by such aggressive foreground masking by, for example, exploring a two-step masking and in-painting algorithm.
Jones, W C; Bock, J; Bond, J; Borrill, J; Boscaleri, A; Cabella, P; Contaldi, C; Crill, B; De Bernardis, P; De Gasperis, G; De Oliveira-Costa, A; De Troia, G; Stefano, G D; Hivon, E; Jaffe, A; Kisner, T; Lange, A; MacTavish, C; Masi, S; Mauskopf, P; Melchiorri, A; Montroy, T; Natoli, P; Netterfield, C B; Pascale, E; Piacentini, F; Pogosyan, D; Polenta, G; Prunet, S; Ricciardi, S; Romeo, G; Ruhl, J; Santini, P; Tegmark, M; Veneziani, M; Vittorio, N
2005-01-01
We report on observations of the Cosmic Microwave Background (CMB) obtained during the January 2003 flight of Boomerang . These results are derived from 195 hours of observation with four 145 GHz Polarization Sensitive Bolometer (PSB) pairs, identical in design to the four 143 GHz Planck HFI polarized pixels. The data include 75 hours of observations distributed over 1.84% of the sky with an additional 120 hours concentrated on the central portion of the field, itself representing 0.22% of the full sky. From these data we derive an estimate of the angular power spectrum of temperature fluctuations of the CMB in 24 bands over the multipole range (50 900). As a consistency check, the collaboration has performed two fully independent analyses of the time ordered data, which are found to be in excellent agreement.
Choudhuri, Samir; Roy, Nirupam; Ghosh, Abhik; Ali, Sk Saiyad
2016-01-01
It is important to correctly subtract point sources from radio-interferometric data in order to measure the power spectrum of diffuse radiation like the Galactic synchrotron or the Epoch of Reionization 21-cm signal. It is computationally very expensive and challenging to image a very large area and accurately subtract all the point sources from the image. The problem is particularly severe at the sidelobes and the outer parts of the main lobe where the antenna response is highly frequency dependent and the calibration also differs from that of the phase center. Here we show that it is possible to overcome this problem by tapering the sky response. Using simulated 150 MHz observations, we demonstrate that it is possible to suppress the contribution due to point sources from the outer parts by using the Tapered Gridded Estimator to measure the angular power spectrum C_l of the sky signal. We also show from the simulation that this method can self-consistently compute the noise bias and accurately subtract it t...
Choudhuri, Samir; Bharadwaj, Somnath; Roy, Nirupam; Ghosh, Abhik; Ali, Sk. Saiyad
2016-06-01
It is important to correctly subtract point sources from radio-interferometric data in order to measure the power spectrum of diffuse radiation like the Galactic synchrotron or the Epoch of Reionization 21-cm signal. It is computationally very expensive and challenging to image a very large area and accurately subtract all the point sources from the image. The problem is particularly severe at the sidelobes and the outer parts of the main lobe where the antenna response is highly frequency dependent and the calibration also differs from that of the phase centre. Here, we show that it is possible to overcome this problem by tapering the sky response. Using simulated 150 MHz observations, we demonstrate that it is possible to suppress the contribution due to point sources from the outer parts by using the Tapered Gridded Estimator to measure the angular power spectrum Cℓ of the sky signal. We also show from the simulation that this method can self-consistently compute the noise bias and accurately subtract it to provide an unbiased estimation of Cℓ.
Lee, Jounghun
2008-01-01
We analyze the photometric redshift catalog of the Sloan Digital Sky Survey Data Release 5 (SDSS DR5) to estimate the Fisher information in the galaxy angular power spectrum with the help of the Rimes-Hamilton technique. It is found that the amount of Fisher information contained in the galaxy angular power spectrum is saturated at lensing multipole scale 300<= l <= 2000 in the redshift range 0.1<= photo-z <0.5. At l=2000, the observed information is two orders of magnitude lower than the case of Gaussian fluctuations. This supports observationally that the translinear regime of the density power spectrum contains little independent information about the initial cosmological conditions, which is consistent with the numerical trend shown by Rimes-Hamilton. Our results also suggest that the Gaussian-noise description may not be valid in weak lensing measurements.
Piacentini, F; Bock, J; Bond, J; Borrill, J; Boscaleri, A; Cabella, P; Contaldi, C; Crill, B; De Bernardis, P; De Gasperis, G; De Oliveira-Costa, A; De Troia, G; Stefano, G D; Hivon, E; Jaffe, A; Kisner, T; Jones, W; Lange, A; Masi, S; Mauskopf, P; MacTavish, C; Melchiorri, A; Montroy, T; Natoli, P; Netterfield, C B; Pascale, E; Pogosyan, D; Polenta, G; Prunet, S; Ricciardi, S; Romeo, G; Ruhl, J; Santini, P; Tegmark, M; Veneziani, M; Vittorio, N
2005-01-01
We present a measurement of the temperature-polarization angular cross power spectrum, , of the Cosmic Microwave Background. The result is based on $\\sim 200$ hours of data from 8 polarization sensitive bolometers operating at 145 GHz during the 2003 flight of BOOMERANG. We detect a significant correlation in the $\\ell$-range between 50 and 950 with a statistical significance > 3.5 sigma. Contamination by polarized foreground emission and systematic effects are negligible in comparison with statistical uncertainty. The spectrum is consistent with previous detections and with the "concordance model" that assumes adiabatic initial conditions. This is the first measurement of using bolometric detectors.
Fornasa, Mattia; Zavala, Jesus; Gaskins, Jennifer M; Sanchez-Conde, Miguel A; Gomez-Vargas, German; Komatsu, Eiichiro; Linden, Tim; Prada, Francisco; Zandanel, Fabio; Morselli, Aldo
2016-01-01
The isotropic gamma-ray background arises from the contribution of unresolved sources, including members of confirmed source classes and proposed gamma-ray emitters such as the radiation induced by dark matter annihilation and decay. Clues about the properties of the contributing sources are imprinted in the anisotropy characteristics of the gamma-ray background. We use 81 months of Pass 7 Reprocessed data from the Fermi Large Area Telescope to perform a measurement of the anisotropy angular power spectrum of the gamma-ray background. We analyze energies between 0.5 and 500 GeV, extending the range considered in the previous measurement based on 22 months of data. We also compute, for the first time, the cross-correlation angular power spectrum between different energy bins. We find that the derived angular spectra are compatible with being Poissonian, i.e. constant in multipole. Moreover, the energy dependence of the anisotropy suggests that the signal is due to two populations of sources, contributing, resp...
Planck Collaboration; Adam, R.; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bracco, A.; Bucher, M.; Burigana, C.; Butler, R. C.; Calabrese, E.; Cardoso, J.-F.; Catalano, A.; Challinor, A.; Chamballu, A.; Chary, R.-R.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Dolag, K.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dunkley, J.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Falgarone, E.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Ghosh, T.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Guillet, V.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Helou, G.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hivon, E.; Hobson, M.; Holmes, W. A.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jewell, J.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Knox, L.; Krachmalnicoff, N.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leahy, J. P.; Leonardi, R.; Lesgourgues, J.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Mazzotta, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, 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.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; 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.; Ponthieu, N.; Popa, L.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Rebolo, R.; Remazeilles, M.; Renault, C.; Renzi, A.; Ricciardi, S.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rouillé d'Orfeuil, B.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Soler, J. D.; Spencer, L. D.; 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.; Tucci, M.; Tuovinen, J.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vibert, L.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Watson, R.; Wehus, I. K.; White, M.; White, S. D. M.; Yvon, D.; Zacchei, A.; Zonca, A.
2016-02-01
The polarized thermal emission from diffuse Galactic dust is the main foreground present in measurements of the polarization of the cosmic microwave background (CMB) at frequencies above 100 GHz. In this paper we exploit the uniqueness of the Planck HFI polarization data from 100 to 353 GHz to measure the polarized dust angular power spectra CℓEE and CℓBB over the multipole range 40 <ℓ< 600 well away from the Galactic plane. These measurements will bring new insights into interstellar dust physics and allow a precise determination of the level of contamination for CMB polarization experiments. Despite the non-Gaussian and anisotropic nature of Galactic dust, we show that general statistical properties of the emission can be characterized accurately over large fractions of the sky using angular power spectra. The polarization power spectra of the dust are well described by power laws in multipole, Cℓ ∝ ℓα, with exponents αEE,BB = -2.42 ± 0.02. The amplitudes of the polarization power spectra vary with the average brightness in a way similar to the intensity power spectra. The frequency dependence of the dust polarization spectra is consistent with modified blackbody emission with βd = 1.59 and Td = 19.6 K down to the lowest Planck HFI frequencies. We find a systematic difference between the amplitudes of the Galactic B- and E-modes, CℓBB/CℓEE = 0.5. We verify that these general properties are preserved towards high Galactic latitudes with low dust column densities. We show that even in the faintest dust-emitting regions there are no "clean" windows in the sky where primordial CMB B-mode polarization measurements could be made without subtraction of foreground emission. Finally, we investigate the level of dust polarization in the specific field recently targeted by the BICEP2 experiment. Extrapolation of the Planck 353 GHz data to 150 GHz gives a dust power 𝒟ℓBB ≡ ℓ(ℓ+1)CℓBB/(2π) of 1.32 × 10-2 μKCMB2 over the multipole range
Adam, R; Aghanim, N; Arnaud, M; Aumont, J; Baccigalupi, C; Banday, A J; Barreiro, R B; Bartlett, J G; Bartolo, N; Battaner, E; Benabed, K; Benoit-Lévy, A; Bernard, J -P; Bersanelli, M; Bielewicz, P; Bonaldi, A; Bonavera, L; Bond, J R; Borrill, J; Bouchet, F R; Boulanger, F; Bracco, A; Bucher, M; Burigana, C; Butler, R C; Calabrese, E; Cardoso, J -F; Catalano, A; Challinor, A; Chamballu, A; Chary, R -R; Chiang, H C; Christensen, P R; Clements, D L; Colombi, S; Colombo, L P L; Combet, C; Couchot, F; Coulais, A; Curto, A; Cuttaia, F; Danese, L; Davies, R D; Davis, R J; de Bernardis, P; de Zotti, G; Delabrouille, J; Delouis, J -M; Désert, F -X; Dickinson, C; Diego, J M; Dolag, K; Dole, H; Donzelli, S; Doré, O; Douspis, M; Ducout, A; Dunkley, J; Dupac, X; Efstathiou, G; Elsner, F; Enßlin, T A; Eriksen, H K; Falgarone, E; Finelli, F; Forni, O; Frailis, M; Fraisse, A A; Franceschi, E; Frejsel, A; Galeotta, S; Galli, S; Ganga, K; Ghosh, T; Giard, M; Giraud-Héraud, Y; Gjerløw, E; González-Nuevo, J; Górski, K M; Gratton, S; Gregorio, A; Gruppuso, A; Guillet, V; Hansen, F K; Hanson, D; Harrison, D L; Helou, G; Henrot-Versillé, S; Hernández-Monteagudo, C; Herranz, D; Hivon, E; Holmes, W A; Huffenberger, K M; Hurier, G; Jaffe, A H; Jaffe, T R; Jewell, J; Jones, W C; Juvela, M; Keihänen, E; Keskitalo, R; Kisner, T S; Kneissl, R; Knoche, J; Knox, L; Krachmalnicoff, N; Kunz, M; Kurki-Suonio, H; Lagache, G; Lamarre, J -M; Lasenby, A; Lattanzi, M; Lawrence, C R; Leahy, J P; Leonardi, R; Lesgourgues, J; Levrier, F; Liguori, M; Lilje, P B; Linden-Vørnle, M; López-Caniego, M; Lubin, P M; Macías-Pérez, J F; Maffei, B; Maino, D; Mandolesi, N; Mangilli, A; Maris, M; Martin, P G; Martínez-González, E; Masi, S; Matarrese, S; Mazzotta, P; Melchiorri, A; Mendes, L; Mennella, A; Migliaccio, M; Mitra, S; Miville-Deschênes, 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; Nørgaard-Nielsen, H U; Noviello, F; Novikov, D; Novikov, I; 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; Ponthieu, N; Popa, L; Pratt, G W; Prunet, S; Puget, J -L; Rachen, J P; Reach, W T; Rebolo, R; Remazeilles, M; Renault, C; Renzi, A; Ricciardi, S; Ristorcelli, I; Rocha, G; Rosset, C; Rossetti, M; Roudier, G; d'Orfeuil, B Rouillé; Rubiño-Martín, J A; Rusholme, B; Sandri, M; Santos, D; Savelainen, M; Savini, G; Scott, D; Soler, J D; Spencer, L D; Stolyarov, V; Stompor, R; Sudiwala, R; Sunyaev, R; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Terenzi, L; Tomasi, M; Tristram, M; Tucci, M; Tuovinen, J; Valenziano, L; Valiviita, J; Van Tent, B; Vibert, L; Vielva, P; Villa, F; Wade, L A; Wandelt, B D; Watson, R; Wehus, I K; White, M; White, S D M; Yvon, D; Zacchei, A; Zonca, A
2016-01-01
The polarized thermal emission from Galactic dust is the main foreground present in measurements of the polarization of the cosmic microwave background (CMB) at frequencies above 100GHz. We exploit the Planck HFI polarization data from 100 to 353GHz to measure the dust angular power spectra $C_\\ell^{EE,BB}$ over the range $40<\\ell<600$. These will bring new insights into interstellar dust physics and a precise determination of the level of contamination for CMB polarization experiments. We show that statistical properties of the emission can be characterized over large fractions of the sky using $C_\\ell$. For the dust, they are well described by power laws in $\\ell$ with exponents $\\alpha^{EE,BB}=-2.42\\pm0.02$. The amplitudes of the polarization $C_\\ell$ vary with the average brightness in a way similar to the intensity ones. The dust polarization frequency dependence is consistent with modified blackbody emission with $\\beta_d=1.59$ and $T_d=19.6$K. We find a systematic ratio between the amplitudes of ...
De Bernardis, P; Bock, J J; Bond, J R; Borrill, J; Boscaleri, A; Coble, K; Contaldi, C R; Crill, B P; De Troia, G; Farese, P; Ganga, K; Giacometti, M; Hivon, E; Hristov, V V; Iacoangeli, A; Jaffe, A H; Jones, W C; Lange, A E; Martinis, L; Masi, S; Mason, P; Mauskopf, P D; Melchiorri, A; Montroy, T; Netterfield, C B; Pascale, E; Piacentini, F; Pogosyan, D; Polenta, G; Pongetti, F; Prunet, S; Romeo, G; Ruhl, J E; Scaramuzzi, F
2002-01-01
Three peaks and two dips have been detected in the power spectrum of the cosmic microwave background from the BOOMERANG experiment, at $\\ell \\sim 210, 540, 840$ and $\\ell \\sim 420, 750$, respectively. Using model-independent analyses, we find that all five features are statistically significant and we measure their location and amplitude. These are consistent with the adiabatic inflationary model. We also calculate the mean and variance of the peak and dip locations and amplitudes in a large 7-dimensional parameter space of such models, which gives good agreement with the model-independent estimates, and forecast where the next few peaks and dips should be found if the basic paradigm is correct. We test the robustness of our results by comparing Bayesian marginalization techniques on this space with likelihood maximization techniques applied to a second 7-dimensional cosmological parameter space, using an independent computational pipeline, and find excellent agreement: $\\Omega_{\\rm tot} = 1.02^{+0.06}_{-0.05...
de Bernardis, P.; Ade, P.A.R.; Bock, J.J.; Bond, J.R.; Borrill,J.; Boscaleri, A.; Coble, K.; Contaldi, C.R.; Crill, B.P.; De Troia, G.; Farese, P.; Ganga, K.; Giacometti, M.; Hivon, E.; Hristov, V.V.; Iacoangeli, A.; Jaffe, A.H.; Jones, W.C.; Lange, A.E.; Martinis, L.; Masi, S.; Mason, P.; Mauskopf, P.D.; Melchiorri, A.; Montroy, T.; Netterfield, C.B.; Pascale, E.; Piacentini, F.; Pogosyan, D.; Polenta,G.; Pongetti, F.; Prunet, S.; Romeo, G.; Ruhl, J.E.; Scaramuzzi, F.
2001-05-17
Three peaks and two dips have been detected in the power spectrum of the cosmic microwave background from the BOOMERANG experiment, at {ell} {approx} 210, 540, 840 and {ell} {approx} 420, 750, respectively. Using model-independent analyses, we find that all five features are statistically significant and we measure their location and amplitude. These are consistent with the adiabatic inflationary model. We also calculate the mean and variance of the peak and dip locations and amplitudes in a large 7-dimensional parameter space of such models, which gives good agreement with the model-independent estimates, and forecast where the next few peaks and dips should be found if the basic paradigm is correct. We test the robustness of our results by comparing Bayesian marginalization techniques on this space with likelihood maximization techniques applied to a second 7-dimensional cosmological parameter space, using an independent computational pipeline, and find excellent agreement: {Omega}{sub tot} = 1.02{sub -0.05}{sup +0.06} vs. 1.04 {+-} 0.05, {Omega}{sub b}h{sup 2} = 0.022{sub -0.003}{sup +0.004} vs. 0.019{sub -0.004}{sup +0.005}, and n{sub s} = 0.96{sub -0.09}{sup +0.10} vs. 0.90 {+-} 0.08. The deviation in primordial spectral index n{sub s} is a consequence of the strong correlation with the optical depth.
THE ANGULAR POWER SPECTRUM OF DUST-OBSCURED GALAXIES AND ITS IMPACT ON SUNYAEV ZEL'DOVICH STUDIES
A. A. Montaña
2011-01-01
Full Text Available En este trabajo medimos el espectro angular de potencias de la población de galaxias milimétricas (SMGs a partir de observaciones a 1.1 mm realizadas con la cámara AzTEC en el Atacama Submillimeter Telescope Experiment (ASTE y el James Clerk Maxwell Telecope (JCMT. La muestra de campos observados nos permite comparar el espectro angular de potencias de las SMGs medido en la dirección de regiones del Universo sin sesgo y otras sobre densas. Nuestras mediciones permiten acotar el impacto que tiene la población de SMGs en mediciones del espectro de potencias de las fluctuaciones primarias y secundarias del fondo cósmico de radiación de microndas (CMB, que actualmente están siendo medidas por una nueva generación de experimentos con resoluciones espaciales del orden de minutos de arco y que operan a longitudes de onda milimétricas.
Malik, Mehul; Leach, Jonathan; Boyd, Robert W
2012-01-01
We implement an interferometric method using two angular slits to measure the orbital angular momentum (OAM) mode spectrum of a partially coherent field. As the angular separation of the slits changes, an interference pattern for a particular OAM mode is obtained. The visibility of this interference pattern as a function of angular separation is equivalent to the angular correlation function of the field. By Fourier transforming the angular correlation function obtained from the double angular slit interference, we are able to calculate the OAM spectrum of the partially coherent field. This method has potential application for characterizing the OAM spectrum in high-dimensional quantum information protocols.
Angular Spectrum Simulation of Pulsed Ultrasound Fields
Du, Yigang; Jensen, Henrik; Jensen, Jørgen Arendt
The optimization of non-linear ultrasound imaging should in a first step be based on simulation, as this makes parameter studies considerably easier than making transducer prototypes. Such a simulation program should be capable of simulating non-linear pulsed fields for arbitrary transducer...... geometries for any kind of focusing and apodization. The Angular Spectrum Approach (ASA) is capable of simulating monochromatic non-linear acoustic wave propagation. However, for ultrasound imaging the time response of each specific point in space is required, and a pulsed ASA simulation with multi temporal...... frequencies must be performed. Combining it with Field II, the generation of non-linear simulation for any geometry with any excitation array transducer becomes feasible. The purpose of this paper is to make a general pulsed simulation software using the modified ASA. Linear and phased array transducers are...
Making waves on CMB power spectrum and inflaton dynamics
Kawasaki, Masahiro; Takahashi, Fuminobu; Takahashi, Tomo
2004-01-01
We discuss cosmic microwave background anisotropies in models with an unconventional primordial power spectrum. In particular, we consider an initial power spectrum with some ``spiky'' corrections. Interestingly, such a primordial power spectrum generates ``wavy'' structure in the CMB angular power spectrum.
A Three-Dimensional Angular Scattering Response Including Path Powers
Mammasis, Kostantinos; Santi, Paolo; Goulianos, Angelos
2011-01-01
In this paper the angular power spectrum exhibited under a three-dimensional (3-D) Gaussian scatter distribution at fixed observation points in space is investigated. Typically, these correspond to the mobile and base units respectively. Unlike other spatial channel models, the derived model accounts for the distance to each scatterer from the observation point and transforms distances into power values under the assumption of free-space propagation. The proposed 3-D spatial channel model fol...
A Remark on the Estimation of Angular Power Spectra in the Presence of Foregrounds
White, M
1998-01-01
It is common practice to estimate the errors on the angular power spectrum which could be obtained by an experiment with a given angular resolution and noise level. Several authors have also addressed the question of foreground subtraction using multi-frequency observations. In such observations the angular resolution of the different frequency channels is rarely the same. In this report we point out how the ``effective'' beam size and noise level change with ell in this case, and give an expression for the error on the angular power spectrum as a function of ell.
Červinka, Ladislav
2011-01-01
Roč. 2, č. 11 (2011), s. 1331-1347. ISSN 2153-120X Institutional research plan: CEZ:AV0Z10100521 Keywords : CMB radiation * analysis of CMB spectrum * radial distribution function of objects * early universe cluster structure * density of ordinary matter Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics
Off-axis angular spectrum method with variable sampling interval
Kim, Yong-Hae; Byun, Chun-Won; Oh, Himchan; Pi, Jae-Eun; Choi, Ji-Hun; Kim, Gi Heon; Lee, Myung-Lae; Ryu, Hojun; Hwang, Chi-Sun
2015-08-01
We proposed a novel off-axis angular spectrum method (ASM) for simulating free space wave propagation with a large shifted destination plane. The off-axis numerical simulation took wave propagation between a parallel source and a destination plane, but a destination plane was shifted from a source plane. The shifted angular spectrum method was proposed for diffraction simulation with a shifted destination plane and satisfied the Nyquist condition for sampling by limiting a bandwidth of a propagation field to avoid an aliasing error due to under sampling. However, the effective sampling number of the shifted ASM decreased when the shifted distance of the destination plane was large which caused a numerical error in the diffraction simulation. To compensate for the decrease of an effective sampling number for the large shifted destination plane, we used a variable sampling interval in a Fourier space to maintain the same effective sampling number independent of the shifted distance of the destination plane. As a result, our proposed off-axis ASM with a variable sampling interval can produce simulation results with high accuracy for nearly every shifted distance of a destination plane when an off-axis angle is less than 75°. We compared the performances of the off-axis ASM using the Chirp Z transform and non-uniform FFT for implementing a variable spatial frequency in a Fourier space.
Non-linear Galaxy Power Spectrum and Cosmological Parameters
Cooray, Asantha
2003-01-01
The galaxy power spectrum is now a well-known tool of precision cosmology. In addition to the overall shape, baryon oscillations and the small-scale suppression of power by massive neutrinos capture complimentary information on cosmological parameters when compared to the angular power spectrum of cosmic microwave background anisotropies. We study both the real space and redshift space galaxy power spectra in the context of non-linear effects and model them based on the halo approach to large...
Zhou, Hailong; Dong, Jianji; Zhang, Pei; Chen, Dongxu; Cai, Xinlun; Li, Fuli; Zhang, Xinliang
2016-01-01
The function to measure orbital angular momentum (OAM) distribution of vortex light is essential for OAM applications. Although there are lots of works to measure OAM modes, it is difficult to measure the power distribution of different OAM modes quantitatively and instantaneously, let alone measure the phase distribution among them. In this work, we demonstrate an OAM complex spectrum analyzer, which enables to measure the power and phase distribution of OAM modes simultaneously by employing rotational Doppler Effect. The original OAM mode distribution is mapped to electrical spectrum of beating signals with a photodetector. The power distribution and phase distribution of superimposed OAM beams are successfully retrieved by analyzing the electrical spectrum. We also extend the measurement to other spatial modes, such as linear polarization modes. These results represent a new landmark of spatial mode analysis and show great potentials in optical communication and OAM quantum state tomography.
Marakulin, A. O.; Sazhina, O. S.; Sazhin, M. V.
2012-07-01
The possibility of the influence of adiabatic scalar perturbations on the angular velocity spectrum of extragalactic sources is considered. The multipole expansion coefficients of the angular velocity field in terms of vector spherical harmonics are calculated. We show that there is no contribution from adiabatic perturbations to the angular spectrum for a spatially flat Universe at the dusty stage, while there is a contribution only to the electric multiple coefficients at the stage of Λ-term domination. The cases of long-wavelength and short-wavelength perturbations are considered separately. The relationship between the multipole angular velocity spectrum and the primordial scalar perturbation spectrum is discussed.
Marakulin, A. O., E-mail: marakulin@physics.msu.ru; Sazhina, O. S.; Sazhin, M. V. [Moscow State University (Russian Federation)
2012-07-15
The possibility of the influence of adiabatic scalar perturbations on the angular velocity spectrum of extragalactic sources is considered. The multipole expansion coefficients of the angular velocity field in terms of vector spherical harmonics are calculated. We show that there is no contribution from adiabatic perturbations to the angular spectrum for a spatially flat Universe at the dusty stage, while there is a contribution only to the electric multiple coefficients at the stage of {Lambda}-term domination. The cases of long-wavelength and short-wavelength perturbations are considered separately. The relationship between the multipole angular velocity spectrum and the primordial scalar perturbation spectrum is discussed.
The possibility of the influence of adiabatic scalar perturbations on the angular velocity spectrum of extragalactic sources is considered. The multipole expansion coefficients of the angular velocity field in terms of vector spherical harmonics are calculated. We show that there is no contribution from adiabatic perturbations to the angular spectrum for a spatially flat Universe at the dusty stage, while there is a contribution only to the electric multiple coefficients at the stage of Λ-term domination. The cases of long-wavelength and short-wavelength perturbations are considered separately. The relationship between the multipole angular velocity spectrum and the primordial scalar perturbation spectrum is discussed.
Linearizing the Observed Power Spectrum
Smith, C; Gross, M; Primack, Joel R; Holtzmann, J A; Smith, Clay; Klypin, Anatoly; Gross, Michael; Primack, Joel; Holtzman, Jon
1997-01-01
Reconstruction of the linear power spectrum from observational data provides a way to compare cosmological models to a large amount of data, as Peacock & Dodds (1994, 1996) have shown. By applying the appropriate corrections to the observational power spectrum it is possible to recover the underlying linear power spectrum for any cosmological model. Using extensive N-body simulations we demonstrate that the method is applicable to a wide range of cosmological models. However, we find that the recovery of the linear power spectrum from observations following PD94 is misleading because the corrections are model- dependent. When we apply the proper corrections for a given model to the observational power spectrum, we find that no model in our test group recovers the linear power spectrum well for the bias suggested by PD94 between Abell, Radio, Optical, and IRAS catalogs 4.5:1.9:1.3:1, with b_IRAS=1. When we allow b_IRAS to vary we find that: (i)CHDM models give very good fits to observations if optically-se...
Angular spectrum characters of high gain non-critical phase match optical parametric oscillators
Liu Jian-Hui; Liu Qiang; Gong Ma-Li
2011-01-01
The angular spectrum gain characters and the power magnification characters of high gain non-walk-off colinear optical parametric oscillators have been studied using the non-colinear phase match method for the first time. The experimental results of the KTiOAsO4 and the KTiOPO4 crystals are discussed in detail. At the high energy single resonant condition, low reflective ratio of the output mirror for the signal and long non-linear crystal are beneficial for small divergence angles. This method can also be used for other high gain non-walk-off phase match optical parametric processes.
Primordial power spectrum of tensor perturbations in Finsler spacetime
Li, Xin [Chongqing University, Department of Physics, Chongqing (China); Chinese Academy of Sciences, State Key Laboratory Theoretical Physics, Institute of Theoretical Physics, Beijing (China); Wang, Sai [Chinese Academy of Sciences, State Key Laboratory Theoretical Physics, Institute of Theoretical Physics, Beijing (China)
2016-02-15
We first investigate the gravitational wave in the flat Finsler spacetime. In the Finslerian universe, we derive the perturbed gravitational field equation with tensor perturbations. The Finslerian background spacetime breaks rotational symmetry and induces parity violation. Then we obtain the modified primordial power spectrum of the tensor perturbations. The parity violation feature requires that the anisotropic effect contributes to the TT, TE, EE, BB angular correlation coefficients with l{sup '} = l + 1 and TB, EB with l{sup '} = l. The numerical results show that the anisotropic contributions to the angular correlation coefficients depend on m, and TE and ET angular correlation coefficients are different. (orig.)
Primordial power spectrum of tensor perturbations in Finsler spacetime
We first investigate the gravitational wave in the flat Finsler spacetime. In the Finslerian universe, we derive the perturbed gravitational field equation with tensor perturbations. The Finslerian background spacetime breaks rotational symmetry and induces parity violation. Then we obtain the modified primordial power spectrum of the tensor perturbations. The parity violation feature requires that the anisotropic effect contributes to the TT, TE, EE, BB angular correlation coefficients with l' = l + 1 and TB, EB with l' = l. The numerical results show that the anisotropic contributions to the angular correlation coefficients depend on m, and TE and ET angular correlation coefficients are different. (orig.)
Modelling the TSZ power spectrum
Bhattacharya, Suman [Los Alamos National Laboratory; Shaw, Laurie D [YALE; Nagai, Daisuke [YALE
2010-01-01
The structure formation in university is a hierarchical process. As universe evolves, tiny density fluctuations that existed in the early universe grows under gravitational instability to form massive large scale structures. The galaxy clusters are the massive viralized objects that forms by accreting smaller clumps of mass until they collapse under their self-gravity. As such galaxy clusters are the youngest objects in the universe which makes their abundance as a function of mass and redshift, very sensitive to dark energy. Galaxy clusters can be detected by measuring the richness in optical waveband, by measuring the X-ray flux, and in the microwave sky using Sunyaev-Zel'dovich (SZ) effect. The Sunyaev-Zel'dovich (SZ) effect has long been recognized as a powerful tool for detecting clusters and probing the physics of the intra-cluster medium. Ongoing and future experiments like Atacama Cosmology Telescope, the South Pole Telescope and Planck survey are currently surveying the microwave sky to develop large catalogs of galaxy clusters that are uniformly selected by the SZ flux. However one major systematic uncertainties that cluster abundance is prone to is the connection between the cluster mass and the SZ flux. As shown by several simulation studies, the scatter and bias in the SZ flux-mass relation can be a potential source of systematic error to using clusters as a cosmology probe. In this study they take a semi-analytic approach for modeling the intra-cluster medium in order to predict the tSZ power spectrum. The advantage of this approach is, being analytic, one can vary the parameters describing gas physics and cosmology simultaneously. The model can be calibrated against X-ray observations of massive, low-z clusters, and using the SZ power spectrum which is sourced by high-z lower mass galaxy groups. This approach allows us to include the uncertainty in gas physics, as dictated by the current observational uncertainties, while measuring the
Two-color ghost imaging with enhanced angular resolving power
This article reports an experimental demonstration on nondegenerate, two-color, biphoton ghost imaging which reproduced a ghost image with enhanced angular resolving power by means of a greater field of view compared with that of classical imaging. With the same imaging magnification, the enhanced angular resolving power and field of view compared with those of classical imaging are 1.25:1 and 1.16:1, respectively. The enhancement of angular resolving power depends on the ratio between the idler and the signal photon frequencies, and the enhancement of the field of view depends mainly on the same ratio and also on the distances of the object plane and the imaging lens from the two-photon source. This article also reports the possibility of reproducing a ghost image with the enhancement of the angular resolving power by means of a greater imaging amplification compared with that of classical imaging.
Angular spectrum characters of high gain non-critical phase match optical parametric oscillators
The angular spectrum gain characters and the power magnification characters of high gain non-walk-off colinear optical parametric oscillators have been studied using the non-colinear phase match method for the first time. The experimental results of the KTiOAsO4 and the KTiOPO4 crystals are discussed in detail. At the high energy single resonant condition, low reflective ratio of the output mirror for the signal and long non-linear crystal are beneficial for small divergence angles. This method can also be used for other high gain non-walk-off phase match optical parametric processes. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)
Hierarchical Cosmic Shear Power Spectrum Inference
Alsing, Justin; Jaffe, Andrew H; Kiessling, Alina; Wandelt, Benjamin; Hoffmann, Till
2016-01-01
We develop a Bayesian hierarchical modelling approach for cosmic shear power spectrum inference, jointly sampling from the posterior distribution of the cosmic shear field and its (tomographic) power spectra. Inference of the shear power spectrum is a powerful intermediate product for a cosmic shear analysis, since it requires very few model assumptions and can be used to perform inference on a wide range of cosmological models \\emph{a posteriori} without loss of information. We show that joint posterior for the shear map and power spectrum can be sampled effectively by Gibbs sampling, iteratively drawing samples from the map and power spectrum, each conditional on the other. This approach neatly circumvents difficulties associated with complicated survey geometry and masks that plague frequentist power spectrum estimators, since the power spectrum inference provides prior information about the field in masked regions at every sampling step. We demonstrate this approach for inference of tomographic shear $E$-...
Absorption spectrum of Gafchromic EBT2 film with angular rotation
Park, Soah; Hwang, Taejin; Yoon, Jai-Woong; Han, Taejin; Kim, Haeyoung; Lee, Me-Yeon; Kim, KyoungJu; Bae, Hoonsik; Kang, Sei-Kwon
2015-01-01
It is important to study absorption spectrum in film dosimetry because the spectral absorbance of the film relates to the film's total absorption dose. We investigated the absorption spectra of Gafchromic EBT2 film with various rotational angles in a visible wavelength band. The film was irradiated with 6 MV photon beams and a total dose of 300 cGy. Absorption spectra were taken under different rotational angles after 24 h after irradiation and we fitted the spectra using Lorentzian functions. There were two dominant absorption peaks at approximately 586 nm (green) and 634 nm (red). The measured spectrum was decomposed 542 nm, 558 nm, 578 nm, 586 nm, 626 nm, 634 nm, and 641 nm. The maximum total area of the red band absorption spectrum was at 45{\\deg}(225{\\deg}) and the minimum at 90{\\deg}(270{\\deg}). As the angle of rotation changed, the intensity and integrated area of the blue and green peaks also changed with 180{\\deg} period, with minima at 90{\\deg} and 270{\\deg}, and maxima at 0{\\deg} and 180{\\deg}, alt...
The validity of high-pass angular spectrum filter in solid immersion lens system
Zheng Chong-Wei; Dai Yu-Xing
2005-01-01
The focal field of a solid immersion lens (SIL) system with a high-pass angular spectrum filter is calculated by using a vector method. Numerical results show that for a radially (azimuthally) polarized input field, a high-pass angular spectrum filter can reduce the light-spot (dark-spot) size of the SIL system. For a linearly polarized input field,however, the focal field cannot be optimized and the optical storage density of the SIL system cannot be improved by using a simple high-pass filter, either.
Impact of Wind Power on the Angular Stability of a Power System
Djemai NAIMI; Bouktir, Tarek
2008-01-01
Wind energy conversion systems are very different in nature from conventional generators. Therefore dynamic studies must be addressed in order to integrate wind power into the power system. Angular stability assessment of wind power generator is one of main issues in power system security and operation. The angular stability for the wind power generator is determined by its corresponding Critical Clearing Time (CCT). In this paper, the effect of wind power on the transient fault behavior is i...
Shear Power Spectrum Reconstruction using Pseudo-Spectrum Method
Hikage, Chiaki; Hamana, Takashi; Spergel, David
2010-01-01
This paper develops a pseudo power spectrum technique for measuring the lensing power spectrum from weak lensing surveys in both the full sky and flat sky limits. The power spectrum approaches have a number of advantages over the traditional correlation function approach. We test the pseudo spectrum method by using numerical simulations with square-shape boundary that include masked regions with complex configuration due to bright stars and saturated spikes. Even when 25% of total area of the survey is masked, the method recovers the E-mode power spectrum at a sub-percent precision over a wide range of multipoles 100
Hierarchical cosmic shear power spectrum inference
Alsing, Justin; Heavens, Alan; Jaffe, Andrew H.; Kiessling, Alina; Wandelt, Benjamin; Hoffmann, Till
2016-02-01
We develop a Bayesian hierarchical modelling approach for cosmic shear power spectrum inference, jointly sampling from the posterior distribution of the cosmic shear field and its (tomographic) power spectra. Inference of the shear power spectrum is a powerful intermediate product for a cosmic shear analysis, since it requires very few model assumptions and can be used to perform inference on a wide range of cosmological models a posteriori without loss of information. We show that joint posterior for the shear map and power spectrum can be sampled effectively by Gibbs sampling, iteratively drawing samples from the map and power spectrum, each conditional on the other. This approach neatly circumvents difficulties associated with complicated survey geometry and masks that plague frequentist power spectrum estimators, since the power spectrum inference provides prior information about the field in masked regions at every sampling step. We demonstrate this approach for inference of tomographic shear E-mode, B-mode and EB-cross power spectra from a simulated galaxy shear catalogue with a number of important features; galaxies distributed on the sky and in redshift with photometric redshift uncertainties, realistic random ellipticity noise for every galaxy and a complicated survey mask. The obtained posterior distributions for the tomographic power spectrum coefficients recover the underlying simulated power spectra for both E- and B-modes.
The Atacama Cosmology Telescope: a measurement of the primordial power spectrum
Hlozek, Renée; Addison, Graeme; Appel, John William; Bond, J Richard; Carvalho, C Sofia; Das, Sudeep; Devlin, Mark; Dünner, Rolando; Essinger-Hileman, Thomas; Fowler, Joseph; Gallardo, Patricio; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hilton, Matt; Hincks, Adam D; Hughes, John P; Irwin, Kent; Klein, Jeff; Kosowsky, Arthur; Marriage, Tobias A; Marsden, Danica; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael D; Nolta, Michael R; Page, Lyman; Parker, Lucas; Partridge, Bruce; Rojas, Felipe; Sehgal, Neelima; Sherwin, Blake; Sievers, Jon; Spergel, David; Staggs, Suzanne; Swetz, Daniel; Switzer, Eric; Thornton, Robert; Wollack, Ed
2011-01-01
We present constraints on the primordial power spectrum of adiabatic fluctuations using data from the 2008 Southern Survey of the Atacama Cosmology Telescope (ACT). The angular resolution of ACT provides sensitivity to scales beyond \\ell = 1000 for resolution of multiple peaks in the primordial temperature power spectrum, which enables us to probe the primordial power spectrum of adiabatic scalar perturbations with wavenumbers up to k \\simeq 0.2 Mpc^{-1}. We find no evidence for deviation from power-law fluctuations over two decades in scale. Matter fluctuations inferred from the primordial temperature power spectrum evolve over cosmic time and can be used to predict the matter power spectrum at late times; we illustrate the overlap of the matter power inferred from CMB measurements (which probe the power spectrum in the linear regime) with existing probes of galaxy clustering, cluster abundances and weak lensing constraints on the primordial power. This highlights the range of scales probed by current measur...
Optimal Binning of the Primordial Power Spectrum
Paykari, Paniez
2009-01-01
The primordial power spectrum describes the initial perturbations in the Universe which eventually grew into the large-scale structure we observe today, and thereby provides an indirect probe of inflation or other structure-formation mechanisms. In this paper we will investigate the best scales the primordial power spectrum can be probed, in accordance with the knowledge about other cosmological parameters such as $\\Omega_{b}$, $\\Omega_{c}$, $\\Omega_{\\Lambda}$, $h$ and $\\tau$. The aim is to find the most informative way of measuring the primordial power spectrum at different length scales, using different types of surveys and the information they provide for the desired cosmological parameters. We will find the optimal binning of the primordial power spectrum for this purpose, by making use of the Fisher matrix formalism. We will then find a statistically orthogonal basis for a set of cosmological parameters, mentioned above, and a set of bins of the primordial power spectrum to investigate the correlation be...
Theory of $\\omega^{-4/3}$ law of the power spectrum in dissipative flows
Hayakawa, Hisao
2005-01-01
It is demonstrated that $\\omega^{-4/3}$ law of the power spectrum with the angular frequency $\\omega$ in dissipative flows is produced by the emission of dispersive waves from the antikink of an congested domain. The analytic theory predicts the spectrum is proportional to $\\omega^{-2}$ for relatively low frequency and $\\omega^{-4/3}$ for high frequency.
Reconstructing the galaxy redshift distribution from angular cross power spectra
Sun, L; Tao, C
2015-01-01
The control of photometric redshift (photo-$z$) errors is a crucial and challenging task for precision weak lensing cosmology. The spacial cross-correlations (equivalently, the angular cross power spectra) of galaxies between tomographic photo-$z$ bins are sensitive to the true redshift distribution $n_i(z)$ of each bin and hence can help calibrate the photo-$z$ error distribution for weak lensing surveys. Using Fisher matrix analysis, we investigate the contributions of various components of the angular power spectra to the constraints of $n_i(z)$ parameters and demonstrate the importance of the cross power spectra therein, especially when catastrophic photo-$z$ errors are present. We further study the feasibility of reconstructing $n_i(z)$ from galaxy angular power spectra using Markov Chain Monte Carlo estimation. Considering an LSST-like survey with $10$ photo-$z$ bins, we find that the underlying redshift distribution can be determined with a fractional precision ($\\sigma(\\theta)/\\theta$ for parameter $\\...
Effect of the length of inflation on angular TT and TE power spectra in power-law inflation
Hirai, S; Hirai, Shiro; Takami, Tomoyuki
2006-01-01
The effect of the length of inflation on the power spectra of scalar and tensor perturbations is estimated using the power-law inflation model with a scale factor of a(t) = t^q. Considering various pre-inflation models with radiation-dominated or scalar matter-dominated periods before inflation in combination with two matching conditions, the temperature angular power spectrum (TT) and temperature-polarization cross-power spectrum (TE) are calculated and a likelihood analysis is performed. It is shown that the discrepancies between the Wilkinson Microwave Anisotropy Probe (WMAP) data and the LCDM model, such as suppression of the spectrum at l = 2,3 and oscillatory behavior, may be explained by the finite length of inflation model if the length of inflation is near 60 e-folds and q > 300. The proposed models retain similar values of chi^2 to that achieved by the LCDM model with respect to fit to the WMAP data, but display different characteristics of the angular TE power spectra at l < 20.
Effect of the length of inflation on angular TT and TE power spectra in power-law inflation
The effect of the length of inflation on the power spectra of scalar and tensor perturbations is estimated using the power-law inflation model with a scale factor of a(η) = (-η)p = tq. Considering various pre-inflation models with radiation-dominated or scalar matter-dominated periods before inflation in combination with two matching conditions, the temperature angular power spectrum (TT) and temperature-polarization cross-power spectrum (TE) are calculated and a likelihood analysis is performed. It is shown that the discrepancies between the Wilkinson microwave anisotropy probe (WMAP) data and the ΛCDM model, such as suppression of the spectrum at l = 2, 3 and oscillatory behaviour, may be explained by the finite length of inflation model if the length of inflation is near 60 e-folds and q ≥ 300. The proposed models retain similar values of χ2 to that achieved by the ΛCDM model with respect to fit to the WMAP data, but display different characteristics of the angular TE power spectra at l ≤ 20
Precision Prediction of the Log Power Spectrum
Repp, Andrew
2016-01-01
At translinear scales, the log power spectrum captures significantly more cosmological information than the standard power spectrum. At high wavenumbers $k$, the cosmological information in the standard power spectrum $P(k)$ fails to increase in proportion to $k$ due to correlations between large- and small-scale modes. As a result, $P(k)$ suffers from an information plateau on these translinear scales, so that analysis with the standard power spectrum cannot access the information contained in these small-scale modes. The log power spectrum $P_A(k)$, on the other hand, captures the majority of this otherwise lost information. Until now there has been no means of predicting the amplitude of the log power spectrum apart from cataloging the results of simulations. We here present a cosmology-independent prescription for the log power spectrum, and we find this prescription to display accuracy comparable to that of Smith et al. (2003), over a range of redshifts and smoothing scales, and for wavenumbers up to $1....
Acoustic scale from the angular power spectra of SDSS-III DR8 photometric luminous galaxies
Seo, Hee-Jong; White, Martin; Cuesta, Antonio; Ross, Ashley; Saito, Shun; Reid, Beth; Padmanabhan, Nikhil; Percival, Will J; de Putter, Roland; Schlegel, David; Eisenstein, Daniel; Xu, Xiaoying; Schneider, Donald; Skibba, Ramin; Verde, Licia; Nichol, Robert; Bizyaev, Dmitry; Brewington, Howard; Brinkmann, J; Costa, Luiz; Gott, J; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Dan; Palanque-Delabrouille, Nathalie; Pan, Kaike; Prada, Francisco; Ross, Nicholas; Simmons, Audrey; Simoni, Fernando; Shelden, Alaina; Snedden, Stephanie; Zehavi, Idit
2012-01-01
We measure the acoustic scale from the angular power spectra of the Sloan Digital Sky Survey III (SDSS-III) Data Release 8 imaging catalog that includes 872,921 galaxies over ~ 10,000 deg^2 between 0.45~ 0.35. We report constraints on cosmological parameters from our measurement in combination with the WMAP7 data and the previous spectroscopic BAO measurements of SDSS (Percival et al. 2010) and WiggleZ (Blake et al. 2011). We refer to our companion papers (Ho et al. 2011; de Putter et al. 2011) for investigations on information of the full power spectrum.
Primordial power spectrum features and consequences
The present Cosmic Microwave Background (CMB) temperature and polarization anisotropy data is consistent with not only a power law scalar primordial power spectrum (PPS) with a small running but also with the scalar PPS having very sharp features. This has motivated inflationary models with such sharp features. Recently, even the possibility of having nulls in the power spectrum (at certain scales) has been considered. The existence of these nulls has been shown in linear perturbation theory. What shall be the effect of higher order corrections on such nulls? Inspired by this question, we have attempted to calculate quantum radiative corrections to the Fourier transform of the 2-point function in a toy field theory and address the issue of how these corrections to the power spectrum behave in models in which the tree-level power spectrum has a sharp dip (but not a null). In particular, we have considered the possibility of the relative enhancement of radiative corrections in a model in which the tree-level spectrum goes through a dip in power at a certain scale. The mode functions of the field (whose power spectrum is to be evaluated) are chosen such that they undergo the kind of dynamics that leads to a sharp dip in the tree level power spectrum. Next, we have considered the situation in which this field has quartic self interactions, and found one loop correction in a suitably chosen renormalization scheme. Thus, we have attempted to answer the following key question in the context of this toy model (which is as important in the realistic case): In the chosen renormalization scheme, can quantum radiative corrections be enhanced relative to tree-level power spectrum at scales, at which sharp dips appear in the tree-level spectrum?
We present a theoretical and experimental analysis of the joint effects of the transverse electric field distribution and of the nonlinear crystal characteristics on the properties of photon pairs generated by spontaneous parametric downconversion (SPDC). While it is known that for a sufficiently short crystal the pump electric field distribution fully determines the joint signal–idler properties, for longer crystals the nonlinear crystal properties also play an important role. In this paper we present experimental measurements of the angular spectrum (AS) and of the conditional angular spectrum (CAS) of photon pairs produced by SPDC, carried out through spatially resolved photon counting. In our experiment we control whether or not the source operates in the short-crystal regime through the degree of pump focusing, and explicitly show how the AS and CAS measurements differ in these two regimes. Our theory provides an understanding of the boundary between these two regimes and also predicts the corresponding differing behaviors. (paper)
Gouesbet, Gérard; Lock, James A.
2016-07-01
When dealing with light scattering and propagation of an electromagnetic beam, there are essentially two kinds of expansions which have been used to describe the incident beam (i) a discrete expansion involving beam shape coefficients and (ii) a continuous expansion in terms of an angular spectrum of plane waves. In this paper, we demonstrate that the angular spectrum decomposition readily leads to two important consequences, (i) laser light beams travel in free space with an effective velocity that is smaller than the speed of light c, and (ii) the optical theorem does not hold for arbitrary shaped beams, both in the case of electromagnetic waves and scalar waves, e.g. quantum and acoustical waves.
Nosach, O.Y.; Orlov, E.P.
1976-07-01
The geometric-optics approximation is used to analyze theoretically the formation of the angular spectrum of the radiation emitted by an iodine laser, relationship between optical inhomogeneities and internal losses, and the influence of the stray scattering noise on the mode composition of the radiation. The threshold conditions are found allowing for optical inhomogeneities in the active medium. It is shown that the presence of such inhomogeneities simply bends the phase front of the radiation without altering its brightness. (AIP)
Measurement of the light orbital angular momentum spectrum using an optical geometric transformation
We recently demonstrated a new method to efficiently analyse the orbital angular momentum (OAM) states of light by application of an optical geometric transformation (Berkhout et al 2010 Phys. Rev. Lett. 105 153601). Here we study the performance of such a system to measure the change in the observed OAM spectrum, as the input beam is misaligned with respect to the analyser. We present modelled and experimental results which show that our reformatting approach does correctly measure the OAM spectrum for lateral and tilt misalignment of the input beam
Sensitivity of a Bolometric Interferometer to the CMB power spectrum
Hamilton, J -Ch; Cressiot, C; Kaplan, J; Piat, M; Rosset, C
2008-01-01
Context. The search for the B-mode polarization fluctuations in the Cosmic Microwave Background is one of the main challenges of modern cosmology. The expected level of the B-mode signal is very low and therefore implies the development of highly sensitive and low systematics instruments. An appealing possibility is bolometric interferometry. Aims. We compare in this article the sensitivity on the CMB angular power spectrum achieved with direct imaging, heterodyne and bolometric interferometry. Methods. Using a simple power spectrum estimator, we calculate its variance leading to the counterpart for Bolometric Interferometry of the well known Knox formula for direct imaging. Results. We find that bolometric interferometry is almost as sensitive as direct imaging for very large scales but suffers from the lack of equivalent/redondant baselines at smaller scales. However, as expected, it ends up being more sensitive than heterodyne interferometry thanks to the low noise of the bolometers. It therefore appears a...
Towards optimal cluster power spectrum analysis
Smith, Robert E.; Marian, Laura
2016-04-01
The power spectrum of galaxy clusters is an important probe of the cosmological model. In this paper, we develop a formalism to compute the optimal weights for the estimation of the matter power spectrum from cluster power spectrum measurements. We find a closed-form analytic expression for the optimal weights, which takes into account: the cluster mass, finite survey volume effects, survey masking, and a flux limit. The optimal weights are w(M,χ ) ∝ b(M,χ )/[1+bar{n}_h(χ ) overline{b^2}(χ )overline{P}(k)], where b(M, χ) is the bias of clusters of mass M at radial position χ(z), bar{n}_h(χ ) and overline{b^2}(χ ) are the expected space density and bias squared of all clusters, and overline{P}(k) is the matter power spectrum at wavenumber k. This result is analogous to that of Percival et al. We compare our optimal weighting scheme with mass weighting and also with the original power spectrum scheme of Feldman et al. We show that our optimal weighting scheme outperforms these approaches for both volume- and flux-limited cluster surveys. Finally, we present a new expression for the Fisher information matrix for cluster power spectrum analysis. Our expression shows that for an optimally weighted cluster survey the cosmological information content is boosted, relative to the standard approach of Tegmark.
Violation of statistical isotropy and homogeneity in the 21-cm power spectrum
Shiraishi, Maresuke; Kamionkowski, Marc; Raccanelli, Alvise
2016-01-01
Most inflationary models predict primordial perturbations to be statistically isotropic and homogeneous. Cosmic-Microwave-Background (CMB) observations, however, indicate a possible departure from statistical isotropy in the form of a dipolar power modulation at large angular scales. Alternative models of inflation, beyond the simplest single-field slow-roll models, can generate a small power asymmetry, consistent with these observations. Observations of clustering of quasars show, however, agreement with statistical isotropy at much smaller angular scales. Here we propose to use off-diagonal components of the angular power spectrum of the 21-cm fluctuations during the dark ages to test this power asymmetry. We forecast results for the planned SKA radio array, a future radio array, and the cosmic-variance-limited case as a theoretical proof of principle. Our results show that the 21-cm-line power spectrum will enable access to information at very small scales and at different redshift slices, thus improving u...
Adaptive power-controllable orbital angular momentum (OAM) multicasting
Li, Shuhui; Wang, Jian
2015-01-01
We report feedback-assisted adaptive multicasting from a single Gaussian mode to multiple orbital angular momentum (OAM) modes using a single phase-only spatial light modulator loaded with a complex phase pattern. By designing and optimizing the complex phase pattern through the adaptive correction of feedback coefficients, the power of each multicast OAM channel can be arbitrarily controlled. We experimentally demonstrate power-controllable multicasting from a single Gaussian mode to two and six OAM modes with different target power distributions. Equalized power multicasting, “up-down” power multicasting and “ladder” power multicasting are realized in the experiment. The difference between measured power distributions and target power distributions is assessed to be less than 1 dB. Moreover, we demonstrate data-carrying OAM multicasting by employing orthogonal frequency-division multiplexing 64-ary quadrature amplitude modulation (OFDM 64-QAM) signal. The measured bit-error rate curves and observed optical signal-to-noise ratio penalties show favorable operation performance of the proposed adaptive power-controllable OAM multicasting. PMID:25989251
Adaptive power-controllable orbital angular momentum (OAM) multicasting.
Li, Shuhui; Wang, Jian
2015-01-01
We report feedback-assisted adaptive multicasting from a single Gaussian mode to multiple orbital angular momentum (OAM) modes using a single phase-only spatial light modulator loaded with a complex phase pattern. By designing and optimizing the complex phase pattern through the adaptive correction of feedback coefficients, the power of each multicast OAM channel can be arbitrarily controlled. We experimentally demonstrate power-controllable multicasting from a single Gaussian mode to two and six OAM modes with different target power distributions. Equalized power multicasting, "up-down" power multicasting and "ladder" power multicasting are realized in the experiment. The difference between measured power distributions and target power distributions is assessed to be less than 1 dB. Moreover, we demonstrate data-carrying OAM multicasting by employing orthogonal frequency-division multiplexing 64-ary quadrature amplitude modulation (OFDM 64-QAM) signal. The measured bit-error rate curves and observed optical signal-to-noise ratio penalties show favorable operation performance of the proposed adaptive power-controllable OAM multicasting. PMID:25989251
H-ATLAS: THE COSMIC ABUNDANCE OF DUST FROM THE FAR-INFRARED BACKGROUND POWER SPECTRUM
Thacker, Cameron; Cooray, Asantha; Smidt, Joseph; De Bernardis, Francesco; Mitchell-Wynne, K. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Amblard, A. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Auld, R.; Eales, S.; Pascale, E. [School of Physics and Astronomy, Cardiff University, The Parade, Cardiff, CF24 3AA (United Kingdom); Baes, M.; Michalowski, M. J. [Sterrenkundig Observatorium, Universiteit Gent, KrijgslAAn 281 S9, B-9000 Gent (Belgium); Clements, D. L.; Dariush, A.; Hopwood, R. [Physics Department, Imperial College London, South Kensington campus, London, SW7 2AZ (United Kingdom); De Zotti, G. [INAF, Osservatorio Astronomico di Padova, Vicolo Osservatorio 5, I-35122 Padova (Italy); Dunne, L.; Maddox, S. [Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch (New Zealand); Hoyos, C. [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Ibar, E. [UK Astronomy Technology Centre, The Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ (United Kingdom); Jarvis, M. [Astrophysics, Department of Physics, Keble Road, Oxford, OX1 3RH (United Kingdom); and others
2013-05-01
We present a measurement of the angular power spectrum of the cosmic far-infrared background (CFIRB) anisotropies in one of the extragalactic fields of the Herschel Astrophysical Terahertz Large Area Survey at 250, 350, and 500 {mu}m bands. Consistent with recent measurements of the CFIRB power spectrum in Herschel-SPIRE maps, we confirm the existence of a clear one-halo term of galaxy clustering on arcminute angular scales with large-scale two-halo term of clustering at 30 arcmin to angular scales of a few degrees. The power spectrum at the largest angular scales, especially at 250 {mu}m, is contaminated by the Galactic cirrus. The angular power spectrum is modeled using a conditional luminosity function approach to describe the spatial distribution of unresolved galaxies that make up the bulk of the CFIRB. Integrating over the dusty galaxy population responsible for the background anisotropies, we find that the cosmic abundance of dust, relative to the critical density, to be between {Omega}{sub dust} = 10{sup -6} and 8 Multiplication-Sign 10{sup -6} in the redshift range z {approx} 0-3. This dust abundance is consistent with estimates of the dust content in the universe using quasar reddening and magnification measurements in the Sloan Digital Sky Survey.
H-ATLAS: THE COSMIC ABUNDANCE OF DUST FROM THE FAR-INFRARED BACKGROUND POWER SPECTRUM
We present a measurement of the angular power spectrum of the cosmic far-infrared background (CFIRB) anisotropies in one of the extragalactic fields of the Herschel Astrophysical Terahertz Large Area Survey at 250, 350, and 500 μm bands. Consistent with recent measurements of the CFIRB power spectrum in Herschel-SPIRE maps, we confirm the existence of a clear one-halo term of galaxy clustering on arcminute angular scales with large-scale two-halo term of clustering at 30 arcmin to angular scales of a few degrees. The power spectrum at the largest angular scales, especially at 250 μm, is contaminated by the Galactic cirrus. The angular power spectrum is modeled using a conditional luminosity function approach to describe the spatial distribution of unresolved galaxies that make up the bulk of the CFIRB. Integrating over the dusty galaxy population responsible for the background anisotropies, we find that the cosmic abundance of dust, relative to the critical density, to be between Ωdust = 10–6 and 8 × 10–6 in the redshift range z ∼ 0-3. This dust abundance is consistent with estimates of the dust content in the universe using quasar reddening and magnification measurements in the Sloan Digital Sky Survey.
H-ATLAS: The cosmic abundance of dust from the far-infrared background power spectrum
Thacker, Cameron; Smidt, Joseph; de Bernardis, Francesco; Mitchell-Wynne, K; Amblard, A; Auld, R; Baes, M; Clements, D L; Dariush, A; De Zotti, G; Dunne, L; Eales, S; Hopwood, R; Hoyos, C; Ibar, E; Jarvis, M; Maddox, S; Michalowski, M J; Pascale, E; Scott, D; Serjeant, S; Smith, M W L; Valiante, E; Van der Werf, P
2012-01-01
We present a measurement of the angular power spectrum of the cosmic far-infrared background (CFIRB) anisotropies in one of the extragalactic fields of the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) at 250, 350 and 500 \\mu m bands. Consistent with recent measurements of the CFIRB power spectrum in Herschel-SPIRE maps, we confirm the existence of a clear one-halo term of galaxy clustering on arcminute angular scales with large-scale two-halo term of clustering at 30 arcminutes to angular scales of a few degrees. The power spectrum at the largest angular scales, especially at 250 \\mu m, is contaminated by the Galactic cirrus. The angular power spectrum is modeled using a conditional luminosity function approach to describe the spatial distribution of unresolved galaxies that make up the bulk of the CFIRB. Integrating over the dusty galaxy population responsible for the background anisotropies, we find that the cosmic abundance of dust, relative to the critical density, to be between \\Omega_dus...
Primordial power spectrum features and consequences
Goswami, Gaurav
2014-01-01
The present Cosmic Microwave Background (CMB) temperature and polarization anisotropy data is consistent with not only a power law scalar primordial power spectrum (PPS) with a small running but also with the scalar PPS having very sharp features. This has motivated inflationary models with such sharp features. Recently, even the possibility of having nulls in the power spectrum (at certain scales) has been considered. The existence of these nulls has been shown in linear perturbation theory. What shall be the effect of higher order corrections on such nulls? Inspired by this question, we attempt to calculate quantum radiative corrections to the Fourier transform of the two-point function in a toy field theory and address the issue of how these corrections to the power spectrum behave in models in which the tree-level power spectrum has a sharp dip (but not a null). In particular, we consider the possibility of the relative enhancement of radiative corrections in a model in which the tree-level spectrum goes ...
Cosmological parameters from lensing power spectrum and bispectrum tomography
Takada, M; Takada, Masahiro; Jain, Bhuvnesh
2004-01-01
We examine how lensing tomography with the bispectrum and power spectrum can constrain cosmological parameters and the equation of state of dark energy. Our analysis uses the full information at the two- and three-point level from angular scales of a few degrees to 5 arcminutes (50 < l < 3000), which will be probed by lensing surveys. We use all triangle configurations, cross-power spectra and bispectra constructed from up to three redshift bins with photometric redshifts, and relevant covariances in our analysis. We find that the parameter constraints from bispectrum tomography are comparable to those from power spectrum tomography. Combining the two improves parameter accuracies by a factor of three due to their complementarity. For the dark energy parameterization w(a) = w0 + wa(1-a), the marginalized errors are sigma(w0) = 0.03 fsky^{-1/2} and sigma(wa) = 0.1 fsky^{-1/2}. The amplitude and shape of the mass power spectrum are also shown to be precisely constrained. We use hyper-extended perturbation...
Accurate calculation of computer-generated holograms using angular-spectrum layer-oriented method.
Zhao, Yan; Cao, Liangcai; Zhang, Hao; Kong, Dezhao; Jin, Guofan
2015-10-01
Fast calculation and correct depth cue are crucial issues in the calculation of computer-generated hologram (CGH) for high quality three-dimensional (3-D) display. An angular-spectrum based algorithm for layer-oriented CGH is proposed. Angular spectra from each layer are synthesized as a layer-corresponded sub-hologram based on the fast Fourier transform without paraxial approximation. The proposed method can avoid the huge computational cost of the point-oriented method and yield accurate predictions of the whole diffracted field compared with other layer-oriented methods. CGHs of versatile formats of 3-D digital scenes, including computed tomography and 3-D digital models, are demonstrated with precise depth performance and advanced image quality. PMID:26480062
Wang, Guangjun; Wang, Huaying; Wang, Dayong; Xie, Jianjun; Zhao, Jie
2007-12-01
A simple holographic high-resolution imaging system without pre-magnification, which is based on off-axis lensless Fourier transform configuration, has been developed. Experimental investigations are performed on USAF resolution test target. The method based on angular spectrum theory for reconstructing lensless Fourier hologram is given. The reconstructed results of the same hologram at different reconstructing distances are presented for what is to our knowledge the first time. Approximate diffraction limited lateral resolution is achieved. The results show that the angular spectrum method has several advantages over more commonly used Fresnel transform method. Lossless reconstruction can be achieved for any numerical aperture holograms as long as the wave field is calculated at a special reconstructing distance, which is determined by the light wavelength and the chip size and the pixel size of the CCD sensor. This is very important for reconstructing an extremely large numerical aperture hologram. Frequency-domain spectrum filtering can be applied conveniently to remove the disturbance of zero-order. The reconstructed image wave field is accurate so long as the sampling theorem is not violated. The experimental results also demonstrate that for a high quality hologram, special image processing is unnecessary to obtain a high quality image.
Impact of Wind Power on the Angular Stability of a Power System
Djemai NAIMI
2008-06-01
Full Text Available Wind energy conversion systems are very different in nature from conventional generators. Therefore dynamic studies must be addressed in order to integrate wind power into the power system. Angular stability assessment of wind power generator is one of main issues in power system security and operation. The angular stability for the wind power generator is determined by its corresponding Critical Clearing Time (CCT. In this paper, the effect of wind power on the transient fault behavior is investigated by replacing the power generated by two main types of wind turbine, increasing gradually a rate of wind power penetration and changing the location of wind resources. The simulation analysis was established on a 14 bus IEEE test system by PSAT/Matlab, which gives access to an extensive library of grid components, and relevant wind turbine model.
Power spectrum analysis for optical tweezers
Berg-Sørensen, K.; Flyvbjerg, H.
2004-01-01
Lorentzian provides. This is achieved using old and new theory for Brownian motion in an incompressible fluid, and new results for a popular photodetection system. The trap and photodetection system are then calibrated simultaneously in a manner that makes optical tweezers a tool of precision for force......The force exerted by an optical trap on a dielectric bead in a fluid is often found by fitting a Lorentzian to the power spectrum of Brownian motion of the bead in the trap. We present explicit functions of the experimental power spectrum that give the values of the parameters fitted, including...
Relativistic Corrections to the Thermal Sunyaev-Zel'dovich Power Spectrum
Hai-Ning Li
2003-01-01
We present a quantitative estimate of the relativistic corrections to the thermal SZ power spectrum produced by the energetic electrons in massive clusters. The corrections are well within 10% for current experiments with working frequencies below v ＜ 100 GHz, but become non-negligible at high frequencies v ＞350 GHz. Moreover, the corrections appear to be slightly smaller at higher e or smaller angular scales. We conclude that there is no need to include the relativistic corrections in the theoretical study of the SZ power spectrum especially at low frequencies unless the SZ power spectrum is used for precision cosmology.
Effect of Coma Aberration on Orbital Angular Momentum Spectrum of Vortex Beams
CHEN Zi-Yang; PU Ji-Xiong
2009-01-01
Spiral spectra of vortex beams with coma aberration are studied.It is shown that the orbital angular momentum (OAM) states of vortex beams with coma aberration are different from those aberration-free vortex beams.Spiral spectra of beams with coma aberration are spreading.It is found that in the presence of coma aberration,the vortex beams contain not only the original OAM component but also other components.A larger coma aberration coefficient and/or a larger beam waist will lead to a wider spreading of the spiral spectrum. The results may have potential applications in information encoding and transmittance.
Ultrasonic oil-film thickness measurement: An angular spectrum approach to assess performance limits
Zhang, J.; Drinkwater, B. W.; Dwyer-Joyce, R.S.
2007-01-01
The performance of ultrasonic oil-film thickness measurement in a ball bearing is quantified. A range of different viscosity oils (Shell T68, VG15, and VG5) are used to explore the lowest reflection coefficient and hence the thinnest oil-film thickness that the system can measure. The results show a minimum reflection coefficient of 0.07 for both oil VG15 and VG5 and 0.09 for oil T68 at 50 MHz. This corresponds to an oil-film thickness of 0.4 Î¼m for T68 oil. An angular spectrum (or Fourier d...
Angular spectrum approach for fast simulation of pulsed non-linear ultrasound fields
Du, Yigang; Jensen, Henrik; Jensen, Jørgen Arendt
The paper presents an Angular Spectrum Approach (ASA) for simulating pulsed non-linear ultrasound fields. The source of the ASA is generated by Field II, which can simulate array transducers of any arbitrary geometry and focusing. The non-linear ultrasound simulation program - Abersim, is used as...... the fundamental and keep the second harmonic field, since Abersim simulates non-linear fields with all harmonic components. ASA and Abersim are compared for the pulsed fundamental and second harmonic fields in the time domain at depths of 30 mm, 40 mm (focal depth) and 60 mm. Full widths at -6 d...
Just enough inflation. Power spectrum modifications at large scales
Cicoli, Michele [Univ. di Bologna (Italy). Dipt. di Fisica ed Astronomia; Abdus Salam International Centre for Theoretical Physics, Trieste (Italy); INFN, Sezione di Bologna (Italy); Downes, Sean [National Taiwan Univ. (China). Leung Center for Cosmology and Particle Astrophysics; Dutta, Bhaskar [Texas A und M Univ. (United States). Dept. Physics and Astronomy; Pedro, Francisco G.; Westphal, Alexander [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2014-07-15
We show that models of 'just enough' inflation, where the slow-roll evolution lasted only 50-60 e-foldings, feature modifications of the CMB power spectrum at large angular scales. We perform a systematic and model-independent analysis of any possible non-slow-roll background evolution prior to the final stage of slow-roll inflation. We find a high degree of universality since most common backgrounds like fast-roll evolution, matter or radiation-dominance give rise to a power loss at large angular scales and a peak together with an oscillatory behaviour at scales around the value of the Hubble parameter at the beginning of slow-roll inflation. Depending on the value of the equation of state parameter, different pre-inflationary epochs lead instead to an enhancement of power at low-l, and so seem disfavoured by recent observational hints for a lack of CMB power at l
Just enough inflation: power spectrum modifications at large scales
Cicoli, Michele [Dipartimento di Fisica ed Astronomia, Università di Bologna, via Irnerio 46, 40126 Bologna (Italy); Downes, Sean [Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan (China); Dutta, Bhaskar [Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843-4242 (United States); Pedro, Francisco G.; Westphal, Alexander, E-mail: mcicoli@ictp.it, E-mail: ssdownes@phys.ntu.edu.tw, E-mail: dutta@physics.tamu.edu, E-mail: francisco.pedro@desy.de, E-mail: alexander.westphal@desy.de [Deutsches Elektronen-Synchrotron DESY, Theory Group, D-22603 Hamburg (Germany)
2014-12-01
We show that models of 'just enough' inflation, where the slow-roll evolution lasted only 50- 60 e-foldings, feature modifications of the CMB power spectrum at large angular scales. We perform a systematic analytic analysis in the limit of a sudden transition between any possible non-slow-roll background evolution and the final stage of slow-roll inflation. We find a high degree of universality since most common backgrounds like fast-roll evolution, matter or radiation-dominance give rise to a power loss at large angular scales and a peak together with an oscillatory behaviour at scales around the value of the Hubble parameter at the beginning of slow-roll inflation. Depending on the value of the equation of state parameter, different pre-inflationary epochs lead instead to an enhancement of power at low ℓ, and so seem disfavoured by recent observational hints for a lack of CMB power at ℓ∼< 40. We also comment on the importance of initial conditions and the possibility to have multiple pre-inflationary stages.
Just enough inflation: power spectrum modifications at large scales
Cicoli, Michele; Dutta, Bhaskar; Pedro, Francisco G; Westphal, Alexander
2014-01-01
We show that models of `just enough' inflation, where the slow-roll evolution lasted only $50-60$ e-foldings, feature modifications of the CMB power spectrum at large angular scales. We perform a systematic and model-independent analysis of any possible non-slow-roll background evolution prior to the final stage of slow-roll inflation. We find a high degree of universality since most common backgrounds like fast-roll evolution, matter or radiation-dominance give rise to a power loss at large angular scales and a peak together with an oscillatory behaviour at scales around the value of the Hubble parameter at the beginning of slow-roll inflation. Depending on the value of the equation of state parameter, different pre-inflationary epochs lead instead to an enhancement of power at low-$\\ell$, and so seem disfavoured by recent observational hints for a lack of CMB power at $\\ell\\lesssim 40$. We also comment on the importance of initial conditions and the possibility to have multiple pre-inflationary stages.
Quantum hyper-entanglement and angular spectrum decomposition applied to sensors
Smith, James F.
2016-05-01
Hyper-entanglement with an emphasis on mode type is used to extend a previously developed atmospheric imaging system. Angular spectrum expansions combined with second quantization formalism permits many different mode types to be considered using a common formalism. Fundamental Gaussian, standard Hermite-Gaussian, standard Laguerre- Gaussian, and Bessel modes are developed. Hyper-entanglement refers to entanglement in more than one degree of freedom, e.g. polarization, energy-time and orbital angular momentum. The system functions at optical or infrared frequencies. Only the signal photon propagates in the atmosphere, the ancilla photon is retained within the detector. This results in loss being essentially classical, giving rise to stronger forms of entanglement. A simple atomic physics based model of the scattering target is developed. This model permits the derivation in closed form of the loss coefficient for photons with a given mode type scattering from the target. Signal loss models for propagation, transmission, detection, and scattering are developed and applied. The probability of detection of photonic orbital angular momentum is considered in terms of random media theory. A model of generation and detection efficiencies for the different degrees of freedom is also considered. The implications of loss mechanisms for signal to noise ratio (SNR), and other quantum information theoretic quantities are discussed. Techniques for further enhancing the system's SNR and resolution through adaptive optics are examined. The formalism permits random noise and entangled or nonentangled sources of interference to be modeled.
Inflection Points and the Power Spectrum
Downes, Sean
2013-01-01
Inflection point inflation generically includes a deviation from slow-roll when the inflaton approaches the inflection point. Such deviations are shown to be generated by transitions between singular trajectories. The effects on the power spectrum are studied within the context of universality classes for small-field models. These effects are shown to scale with universality parameters, and can explain the anomalously low power at large scales observed in the CMB. The reduction of power is related to the inflection point's basin of attraction. Implications for the likelihood of inflation are discussed.
Pulsed power for angular multiplexed laser fusion drivers
The feasibility of using rare gas-halide lasers, in particular the KrF laser, as inertial confinement fusion (ICF) drivers has been assessed. These lasers are scalable to the required high energy (approx. =1-5 MJ) in a short pulse (approx. =10 ns) by optical angular multiplexing, and integration of the output from approx. =100 kJ laser amplifier subsystems. The e-beam current density (approx. =50A/cm2) and voltage (approx. =800 kV) required for these power amplifiers lead to an e-beam impedance of approx. =0.2Ω for approx. =300 ns pump time. This impedance level requires modularization of the large area e-gun, a) to achieve a diode inductance consistent with fast current risetime, b) to circumvent dielectric breakdown constraints in the pulse forming lines, and c) to reduce the requirement for guide magnetic fields. Pulsed power systems requirements, design concepts, scalability, tradeoffs, and performance projections are discussed in this paper
The Angular Power Spectra of Photometric SDSS LRGs
Thomas, Shaun A; Lahav, Ofer
2010-01-01
We construct new galaxy angular power spectra based on the extended, updated and final SDSS II Luminous Red Galaxy (LRG) photometric redshift survey: MegaZ DR7. Encapsulating 7746 deg^{2} we utilise 723,556 photometrically determined LRGs between 0.45 < z < 0.65 in a 3.3 (Gpc h^{-1})^3 spherical harmonic analysis of the galaxy distribution. By combining four photometric redshift bins we find preliminary parameter constraints of f_{b} = \\Omega_{b}/\\Omega_{m} = 0.173 +/- 0.046 and \\Omega_{m} = 0.260 +/- 0.035 assuming H_{0} = 75 km s^{-1} Mpc^{-1}, n_{s}=1 and \\Omega_{k} = 0. These limits are consistent with the CMB and the previous data release (DR4). The C_{\\ell} are sensitive to redshift space distortions and therefore we also recast our constraints into a measurement of \\beta ~ \\Omega_{m}^{0.55}/b in different redshift shells. The robustness of these power spectra with respect to a number of potential systematics such as extinction, photometric redshift and ANNz training set extrapolation are examined...
The Atacama Cosmology Telescope: A Measurement of the Primordial Power Spectrum
Hlozek, Renee; Dunkley, Joanna; Addison, Graeme; Appel, John William; Bond, J. Richard; Carvalho, C. Sofia; Das, Sudeep; Devlin, Mark J.; Duenner, Rolando; Essinger-Hileman, Thomas; Fowler, Joseph W.; Gallardo, Patricio; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hilton, Matt; Hincks, Adam D.; Hughes, John P.; Irwin, Kent D.; Klein, Jeff; Kosowsky, Arthur; Marriage, Tobias A.; Marsden, Danica; Menanteau, Felipe; Wollack, Ed
2011-01-01
We present constraints on the primordial power spectrum of adiabatic fluctuations using data from the 2008 Southern Survey of the Atacama Cosmology Telescope (ACT). The angular resolution of ACT provides sensitivity to scales beyond l = 1000 for resolution of multiple peaks in the primordial temperature power spectrum, which enables us to probe the primordial power spectrum of adiabatic scalar perturbations with wavenumbers up to k approx. = 0.2 Mp/c. We find no evidence for deviation from power-law fluctuations over two decades in scale. Matter fluctuations inferred from the primordial temperature power spectrum evolve over cosmic time and can be used to predict the matter power spectrum at late times; we illustrate the overlap of the matter power inferred from CMB measurements (which probe the power spectrum in thc linear regime) with existing probes of galaxy clustering, cluster abundances and weak lensing constraints on the primordial power. This highlights the range of scales probed by current measurement.s of the matter power spectrum.
THE ATACAMA COSMOLOGY TELESCOPE: A MEASUREMENT OF THE PRIMORDIAL POWER SPECTRUM
We present constraints on the primordial power spectrum of adiabatic fluctuations using data from the 2008 Southern Survey of the Atacama Cosmology Telescope (ACT) in combination with measurements from the Wilkinson Microwave Anisotropy Probe and a prior on the Hubble constant. The angular resolution of ACT provides sensitivity to scales beyond l = 1000 for resolution of multiple peaks in the primordial temperature power spectrum, which enables us to probe the primordial power spectrum of adiabatic scalar perturbations with wavenumbers up to k ≅ 0.2 Mpc–1. We find no evidence for deviation from power-law fluctuations over two decades in scale. Matter fluctuations inferred from the primordial temperature power spectrum evolve over cosmic time and can be used to predict the matter power spectrum at late times; we illustrate the overlap of the matter power inferred from cosmic microwave background measurements (which probe the power spectrum in the linear regime) with existing probes of galaxy clustering, cluster abundances, and weak-lensing constraints on the primordial power. This highlights the range of scales probed by current measurements of the matter power spectrum.
CHIPS: The Cosmological HI Power Spectrum Estimator
Trott, Cathryn M; Procopio, Pietro; Wayth, Randall B; Mitchell, Daniel A; McKinley, Benjamin; Tingay, Steven J; Barry, N; Beardsley, A P; Bernardi, G; Bowman, Judd D; Briggs, F; Cappallo, R J; Carroll, P; de Oliveira-Costa, A; Dillon, Joshua S; Ewall-Wice, A; Feng, L; Greenhill, L J; Hazelton, B J; Hewitt, J N; Hurley-Walker, N; Johnston-Hollitt, M; Jacobs, Daniel C; Kaplan, D L; Kim, HS; Lenc, E; Line, J; Loeb, A; Lonsdale, C J; Morales, M F; Morgan, E; Neben, A R; Thyagarajan, Nithyanandan; Oberoi, D; Offringa, A R; Ord, S M; Paul, S; Pober, J C; Prabu, T; Riding, J; Shankar, N Udaya; Sethi, Shiv K; Srivani, K S; Subrahmanyan, R; Sullivan, I S; Tegmark, M; Webster, R L; Williams, A; Williams, C L; Wu, C; Wyithe, J S B
2016-01-01
Detection of the cosmological neutral hydrogen signal from the Epoch of Reionization, and estimation of its basic physical parameters, is the principal scientific aim of many current low-frequency radio telescopes. Here we describe the Cosmological HI Power Spectrum Estimator (CHIPS), an algorithm developed and implemented with data from the Murchison Widefield Array (MWA), to compute the two-dimensional and spherically-averaged power spectrum of brightness temperature fluctuations. The principal motivations for CHIPS are the application of realistic instrumental and foreground models to form the optimal estimator, thereby maximising the likelihood of unbiased signal estimation, and allowing a full covariant understanding of the outputs. CHIPS employs an inverse-covariance weighting of the data through the maximum likelihood estimator, thereby allowing use of the full parameter space for signal estimation ("foreground suppression"). We describe the motivation for the algorithm, implementation, application to ...
Power Spectrum Analysis of Three-Dimensional Redshift Surveys
Feldman, H A; Peacock, J A; Feldman, Hume A.; Kaiser, Nick; Peacock, John A.
1994-01-01
We develop a general method for power spectrum analysis of three dimensional redshift surveys. We present rigorous analytical estimates for the statistical uncertainty in the power and we are able to derive a rigorous optimal weighting scheme under the reasonable (and largely empirically verified) assumption that the long wavelength Fourier components are Gaussian distributed. We apply the formalism to the updated 1-in-6 QDOT IRAS redshift survey, and compare our results to data from other probes: APM angular correlations; the CfA and the Berkeley 1.2Jy IRAS redshift surveys. Our results bear out and further quantify the impression from e.g.\\ counts-in-cells analysis that there is extra power on large scales as compared to the standard CDM model with $\\Omega h\\simeq 0.5$. We apply likelihood analysis using the CDM spectrum with $\\Omega h$ as a free parameter as a phenomenological family of models; we find the best fitting parameters in redshift space and transform the results to real space. Finally, we calcul...
Power Spectrum Super-Sample Covariance
Takada, Masahiro
2013-01-01
We provide a simple, unified approach to describing the impact of super-sample covariance on power spectrum estimation in a finite-volume survey. For a wide range of survey volumes, the sample variance that arises from modes that are larger than the survey dominates the covariance of power spectrum estimators for modes much smaller than the survey. The perturbative and deeply nonlinear versions of this effect are known as beat coupling and halo sample variance respectively. We show that they are unified by the matter trispectrum of squeezed configurations and that such configurations obey a consistency relation which relates them to the response of the power spectrum to a change in the background density. Our method also applies to statistics that are based on radial projections of the density field such as weak lensing shear. While we use the halo model for an analytic description to expose the nature of the effect, the consistency description enables an accurate calibration of the full effect directly from ...
Angular spectrum simulation of X-ray focusing by Fresnel zone plates
An efficient computing simulation routine has been implemented to model explicitly several types of Fresnel zone plate taking advantage of the circular symmetry. This code was used to evaluate an optimized approach for stacking of two high-resolution Fresnel zone plates. A computing simulation routine to model any type of circularly symmetric diffractive X-ray element has been implemented. The wavefield transmitted beyond the diffractive structures is numerically computed by the angular spectrum propagation method to an arbitrary propagation distance. Cylindrical symmetry is exploited to reduce the computation and memory requirements while preserving the accuracy of the numerical calculation through a quasi-discrete Hankel transform algorithm, an approach described by Guizar-Sicairos & Gutierrez-Vega [J. Opt. Soc. Am. A, (2004 ▶), 21, 53–58]. In particular, the code has been used to investigate the requirements for the stacking of two high-resolution Fresnel zone plates with an outermost zone width of 20 nm
Fast simulation of non-linear pulsed ultrasound fields using an angular spectrum approach
Du, Yigang; Jensen, Jørgen Arendt
2013-01-01
accuracy of the nonlinear ASA is compared to the non-linear simulation program – Abersim, which is a numerical solution to the Burgers equation based on the OSM. Simulations are performed for a linear array transducer with 64 active elements, focus at 40 mm, and excitation by a 2-cycle sine wave with a......A fast non-linear pulsed ultrasound field simulation is presented. It is implemented based on an angular spectrum approach (ASA), which analytically solves the non-linear wave equation. The ASA solution to the Westervelt equation is derived in detail. The calculation speed is significantly...... increased compared to a numerical solution using an operator splitting method (OSM). The ASA has been modified and extended to pulsed non-linear ultrasound fields in combination with Field II, where any array transducer with arbitrary geometry, excitation, focusing and apodization can be simulated. The...
Alpar, M.A.
1986-12-01
Model power spectra are constructed for quasi-periodic oscillations of the type observed in some galactic bulge X-ray sources. It is shown that the angular location of clumping in the boundary layer, as well as the spread in Keplerian velocities within the boundary layer, will effect the form of the power spectrum under certain conditions. The occurrence of such features in observed power spectra would yield information on the possible role of the magnetic field in clumping and on the radial velocity of matter moving through the boundary layer.
Low Power Compact Radio Galaxies at High Angular Resolution
Giroletti, Marcello; Giovannini, G.; /Bologna U. /Bologna, Ist. Radioastronomia; Taylor, G.B.; /KIPAC, Menlo Park /NRAO, Socorro
2005-06-30
We present sub-arcsecond resolution multi-frequency (8 and 22 GHz) VLA images of five low power compact (LPC) radio sources, and phase referenced VLBA images at 1.6 GHz of their nuclear regions. At the VLA resolution we resolve the structure and identify component positions and flux densities. The phase referenced VLBA data at 1.6 GHz reveals flat-spectrum, compact cores (down to a few milliJansky) in four of the five sources. The absolute astrometry provided by the phase referencing allows us to identify the center of activity on the VLA images. Moreover, these data reveal rich structures, including two-sided jets and secondary components. On the basis of the arcsecond scale structures and of the nuclear properties, we rule out the presence of strong relativistic effects in our LPCs, which must be intrinsically small (deprojected linear sizes {approx}< 10 kpc). Fits of continuous injection models reveal break frequencies in the GHz domain, and ages in the range 10{sup 5}-10{sup 7} yrs. In LPCs, the outermost edge may be advancing more slowly than in more powerful sources or could even be stationary; some LPCs might also have ceased their activity. In general, the properties of LPCs can be related to a number of reasons, including, but not limited to: youth, frustration, low kinematic power jets, and short-lived activity in the radio.
Planck 2013 results. XXI. All-sky Compton parameter power spectrum and high-order statistics
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.; Cardoso, J.F.; Carvalho, P.; Catalano, A.; Challinor, A.; Chamballu, A.; Chiang, L.Y.; Chiang, H.C.; Christensen, P.R.; Church, S.; Clements, D.L.; Colombi, S.; Colombo, L.P.L.; Comis, B.; Couchot, F.; Coulais, A.; Crill, B.P.; Curto, A.; Cuttaia, F.; Da Silva, A.; 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.; Dupac, X.; Efstathiou, G.; Ensslin, T.A.; Eriksen, H.K.; Finelli, F.; Flores-Cacho, I.; Forni, O.; Frailis, M.; Franceschi, E.; Galeotta, S.; Ganga, K.; Genova-Santos, R.T.; Giard, M.; Giardino, G.; Giraud-Heraud, Y.; Gonzalez-Nuevo, J.; Gorski, K.M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; 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.; Hovest, W.; Huffenberger, K.M.; Hurier, G.; Jaffe, T.R.; Jaffe, A.H.; Jones, W.C.; Juvela, M.; Keihanen, E.; Keskitalo, R.; Kisner, T.S.; Kneissl, R.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lacasa, F.; Lagache, G.; Lahteenmaki, A.; Lamarre, J.M.; Lasenby, A.; Laureijs, R.J.; Lawrence, C.R.; Leahy, J.P.; Leonardi, R.; Leon-Tavares, J.; Lesgourgues, J.; Liguori, M.; Lilje, P.B.; Linden-Vornle, M.; Lopez-Caniego, M.; Lubin, P.M.; Macias-Perez, J.F.; Maffei, B.; Maino, D.; Mandolesi, N.; Marcos-Caballero, A.; Maris, M.; Marshall, D.J.; Martin, P.G.; Martinez-Gonzalez, E.; Masi, S.; Matarrese, S.; Matthai, F.; Mazzotta, P.; Melchiorri, A.; Melin, J.B.; Mendes, L.; Mennella, A.; Migliaccio, 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.; Osborne, S.; Oxborrow, C.A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Partridge, B.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G.W.; Prezeau, G.; Prunet, S.; Puget, J.L.; Rachen, J.P.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubino-Martin, J.A.; Rusholme, B.; Sandri, M.; Santos, D.; 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.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Varis, J.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L.A.; Wandelt, B.D.; White, S.D.M.; Yvon, D.; Zacchei, A.; Zonca, A.
2014-01-01
We have constructed the first all-sky map of the thermal Sunyaev-Zeldovich (tSZ) effect by applying specifically tailored component separation algorithms to the 100 to 857 GHz frequency channel maps from the Planck survey. These maps show an obvious galaxy cluster tSZ signal that is well matched with blindly detected clusters in the Planck SZ catalogue. To characterize the signal in the tSZ map we have computed its angular power spectrum. At large angular scales ($\\ell 500$) the clustered Cosmic Infrared Background (CIB) and residual point sources are the major contaminants. These foregrounds are carefully modelled and subtracted. We measure the tSZ power spectrum in angular scales, $0.17^{\\circ} \\lesssim \\theta \\lesssim 3.0^{\\circ}$, that were previously unexplored. The measured tSZ power spectrum is consistent with that expected from the Planck catalogue of SZ sources, with additional clear evidence of signal from unresolved clusters and, potentially, diffuse warm baryons. We use the tSZ power spectrum to ...
COPSS: The CO Power Spectrum Survey
Keating, Garrett K.; Bower, Geoffrey C.; Marrone, Daniel P.; Heiles, Carl E.; SZA, CARMA, COPSS
2016-01-01
Molecular gas is a vital component of galactic evolution and star formation, but its abundance in normal star-forming galaxies in the early Universe is poorly understood. Direct detection methods have been able to probe only the most luminous of galaxies at z˜3, missing the vast population of Milky Way progenitors and "building block" galaxies that are expected to bear the bulk of the molecular gas of the early Universe. Using the technique of "intensity mapping", where measurements of different 3D Fourier modes are used to construct a power spectrum, these smaller galaxies can be detectable as an integrated ensemble.We present results from the CO Power Spectrum Survey (COPSS), an intensity mapping experiment performed with the Sunyaev-Zel'dovich Array (SZA). The SZA, a 3.5m × 8-element subset of the Combined Array for Research in Millimeter-wave Astronomy, is capable of observing CO (J=1→0) at z=2.3-3.3. We present final results from of the first phase of this project, utilizing an archival dataset (covering 44 fields in 1400 hours observing time). With these data, we constrain the CO power spectrum to PCO < 2.6×104 μK2 (Mpc/h)3 at z˜3, excluding the model of Lidz et al. (2011) and putting significant constraints on one of two models from Pullen et al. (2013) at this redshift. With this limit, we are able to constrain the cosmic molecular gas density to ρH2(z˜3) < 2.8×108 M⊙ Mpc-3. We also present current results from the second phase of this project, a 5000-hour observing campaign with the SZA, which increases our sensitivity by more than an order of magnitude.
The visibility based Tapered Gridded Estimator (TGE) for the redshifted 21-cm power spectrum
Choudhuri, Samir; Chatterjee, Suman; Ali, Sk Saiyad; Roy, Nirupam; Ghosh, Abhik
2016-01-01
We present the improved visibility based Tapered Gridded Estimator (TGE) for the power spectrum of the diffuse sky signal. The visibilities are gridded to reduce the computation, and tapered through a convolution to suppress the contribution from the outer regions of the telescope's field of view. The TGE also internally estimates the noise bias, and subtracts this out to give an unbiased estimate of the power spectrum. An earlier version of the 2D TGE for the angular power spectrum $C_{\\ell}$ is improved and then extended to obtain the 3D TGE for the power spectrum $P({\\bf k})$ of the 21-cm brightness temperature fluctuations. Analytic formulas are also presented for predicting the variance of the binned power spectrum. The estimator and its variance predictions are validated using simulations of $150 \\, {\\rm MHz}$ GMRT observations. We find that the estimator accurately recovers the input model for the 1D Spherical Power Spectrum $P(k)$ and the 2D Cylindrical Power Spectrum $P(k_\\perp,k_\\parallel)$, and the...
Toward optimal cluster power spectrum analysis
Smith, Robert E
2014-01-01
The power spectrum of galaxy clusters is an important probe of the cosmological model. In this paper we determine the optimal weighting scheme for maximizing the signal-to-noise ratio for such measurements. We find a closed form analytic expression for the optimal weights. Our expression takes into account: cluster mass, finite survey volume effects, survey masking, and a flux limit. The implementation of this weighting scheme requires knowledge of the measured cluster masses, and analytic models for the bias and space-density of clusters as a function of mass and redshift. Recent studies have suggested that the optimal method for reconstruction of the matter density field from a set of clusters is mass-weighting (Seljak et al 2009, Hamaus et al 2010, Cai et al 2011). We compare our optimal weighting scheme with this approach and also with the original power spectrum scheme of Feldman et al (1994). We show that our optimal weighting scheme outperforms these approaches for both volume- and flux-limited cluster...
Acoustic oscillations in the SDSS DR4 Luminous Red Galaxy sample power spectrum
Huetsi, Gert
2005-01-01
We calculate the redshift-space power spectrum of the Sloan Digital Sky Survey (SDSS) Data Release 4 (DR4) Luminous Red Galaxy (LRG) sample, finding evidence for a full series of acoustic features down to the scales of \\sim 0.2 hMpc^{-1}. This corresponds up to the 7th peak in the CMB angular power spectrum. The acoustic scale derived, (105.4 \\pm 2.3) h^{-1}Mpc, agrees very well with the ``concordance'' model prediction and also with the one determined via the analysis of the spatial two-poin...
The CMB power spectrum out to l=1400 measured by the VSA
Grainge, K; Cleary, K; Davies, R D; Davis, R J; Dickinson, C; Genova-Santos, R; Gutíerrez, C M; Hafez, Y A; Hobson, M P; Jones, M E; Kneissl, R; Lancaster, K; Lasenby, A; Leahy, J P; Maisinger, K; Pooley, G G; Rebolo, R; Rubiño-Martín, J A; Molina, P S; Odman, C; Rusholme, B A; Saunders, R D E; Savage, R; Scott, P F; Slosar, A; Taylor, A C; Titterington, D; Waldram, E M; Watson, R A; Wilkinson, A; Grainge, Keith; Carreira, Pedro; Cleary, Kieran; Davies, Rod D.; Davis, Richard J.; Dickinson, Clive; Genova-Santos, Ricardo; Gutierrez, Carlos M.; Hafez, Yaser A.; Hobson, Michael P.; Jones, Michael E.; Kneissl, Rudiger; Lancaster, Katy; Lasenby, Anthony; Maisinger, Klaus; Pooley, Guy G.; Rebolo, Rafael; Rubino-Martin, Jose Alberto; Molina, Pedro Sosa; Odman, Carolina; Rusholme, Ben; Saunders, Richard D.E.; Savage, Richard; Scott, Paul F.; Slosar, Anze; Taylor, Angela C.; Titterington, David; Waldram, Elizabeth; Watson, Robert A.; Wilkinson, Althea
2003-01-01
We have observed the cosmic microwave background (CMB) in three regions of sky using the Very Small Array (VSA) in an extended configuration with antennas of beamwidth 2 degrees at 34 GHz. Combined with data from previous VSA observations using a more compact array with larger beamwidth, we measure the power spectrum of the primordial CMB anisotropies between angular multipoles l = 160 - 1400. Such measurements at high l are vital for breaking degeneracies in parameter estimation from the CMB power spectrum and other cosmological data. The power spectrum clearly resolves the first three acoustic peaks, shows the expected fall off in power at high l and starts to constrain the position and height of a fourth peak.
We investigate the impact of nonlinear evolution of the gravitational potentials in the ΛCDM model on the integrated Sachs-Wolfe (ISW) contribution to the cosmic microwave background (CMB) temperature power spectrum, and on the cross-power spectrum of the CMB and a set of biased tracers of the mass. We use an ensemble of N-body simulations to directly follow the potentials and compare the results to analytic PT methods. The predictions from the PT match the results to high precision for k-1. We compute the nonlinear corrections to the angular power spectrum and find them to be 100 the departures are more significant; however, the CMB signal is more than a factor 103 larger at this scale. Nonlinear ISW effects therefore play no role in shaping the CMB power spectrum for lm(z)<0.3. Numerical results confirm these expectations and we find no sign change in ISW large-scale structure cross power for low redshifts. Corrections due to nonlinearity and scale dependence of the bias are found to be <10% for l<100, and are therefore below the signal to noise of the current and future measurements. Finally, we estimate the cross-correlation coefficient between the CMB and halos and show that it can be made to match that for the dark matter and CMB to within 5% for thin redshift shells, thus mitigating the need to model bias evolution.
Power spectrum analysis for defect screening in integrated circuit devices
Tangyunyong, Paiboon; Cole Jr., Edward I.; Stein, David J.
2011-12-01
A device sample is screened for defects using its power spectrum in response to a dynamic stimulus. The device sample receives a time-varying electrical signal. The power spectrum of the device sample is measured at one of the pins of the device sample. A defect in the device sample can be identified based on results of comparing the power spectrum with one or more power spectra of the device that have a known defect status.
Power law in the angular velocity distribution of a granular needle
Piasecki, J.; Viot, P.
2005-01-01
We show how inelastic collisions induce a power law with exponent -3 in the decay of the angular velocity distribution of anisotropic particles with sufficiently small moment of inertia. We investigate this question within the Boltzmann kinetic theory for an elongated granular particle immersed in a bath. The power law persists so long as the collisions are inelastic for a large range of angular velocities provided the mass ratio of the anisotropic particle and the bath particles remains smal...
Violation of statistical isotropy and homogeneity in the 21-cm power spectrum
Shiraishi, Maresuke; Muñoz, Julian B.; Kamionkowski, Marc; Raccanelli, Alvise
2016-05-01
Most inflationary models predict primordial perturbations to be statistically isotropic and homogeneous. Cosmic microwave background (CMB) observations, however, indicate a possible departure from statistical isotropy in the form of a dipolar power modulation at large angular scales. Alternative models of inflation, beyond the simplest single-field slow-roll models, can generate a small power asymmetry, consistent with these observations. Observations of clustering of quasars show, however, agreement with statistical isotropy at much smaller angular scales. Here, we propose to use off-diagonal components of the angular power spectrum of the 21-cm fluctuations during the dark ages to test this power asymmetry. We forecast results for the planned SKA radio array, a future radio array, and the cosmic-variance-limited case as a theoretical proof of principle. Our results show that the 21-cm line power spectrum will enable access to information at very small scales and at different redshift slices, thus improving upon the current CMB constraints by ˜2 orders of magnitude for a dipolar asymmetry and by ˜1 - 3 orders of magnitude for a quadrupolar asymmetry case.
Reconstruction of the primordial power spectrum from CMB data
Guo, Zong-Kuan; Schwarz, Dominik J.; Zhang, Yuan-Zhong
2011-01-01
Measuring the deviation from scale invariance of the primordial power spectrum is a critical test of inflation. In this paper we reconstruct the shape of the primordial power spectrum of curvature perturbations from the cosmic microwave background data, including the 7-year Wilkinson Microwave Anisotropy Probe data and the Atacama Cosmology Telescope 148 GHz data, by using a binning method of a cubic spline interpolation in log-log space. We find that the power-law spectrum is preferred by th...
Non-linear corrections to inflationary power spectrum
Gong, Jinn-Ouk(Asia Pacific Center for Theoretical Physics, 67 Cheongam-ro, Pohang, 790-784, Korea); Noh, Hyerim; Hwang, Jai-chan
2010-01-01
We study non-linear contributions to the power spectrum of the curvature perturbation on super-horizon scales, produced during slow-roll inflation driven by a canonical single scalar field. We find that on large scales the linear power spectrum completely dominates and leading non-linear corrections remain totally negligible, indicating that we can safely rely on linear perturbation theory to study inflationary power spectrum. We also briefly comment on the infrared and ultraviolet behaviour ...
Multiple alignment of the orbital angular momentum in the spectrum of the 158Er nucleus is described in a phenomenological model based on the high-spin approximation for the Coriolis mixing of positive-parity states. Anomalous antialigned a bands are introduced as a continuation of aligned s bands to ensure their crossing. In the proposed diagram εIν(ωcurl) alignment in the nuclear spectra manifests itself especially clearly. 15 refs., 2 figs., 2 tabs
Wind speed power spectrum analysis for Bushland, Texas
Eggleston, E.D. [USDA-Agricultural Research Service, Bushland, TX (United States)
1996-12-31
Numerous papers and publications on wind turbulence have referenced the wind speed spectrum presented by Isaac Van der Hoven in his article entitled Power Spectrum of Horizontal Wind Speed Spectrum in the Frequency Range from 0.0007 to 900 Cycles per Hour. Van der Hoven used data measured at different heights between 91 and 125 meters above the ground, and represented the high frequency end of the spectrum with data from the peak hour of hurricane Connie. These facts suggest we should question the use of his power spectrum in the wind industry. During the USDA - Agricultural Research Service`s investigation of wind/diesel system power storage, using the appropriate wind speed power spectrum became a significant issue. We developed a power spectrum from 13 years of hourly average data, 1 year of 5 minute average data, and 2 particularly gusty day`s 1 second average data all collected at a height of 10 meters. While the general shape is similar to the Van der Hoven spectrum, few of his peaks were found in the Bushland spectrum. While higher average wind speeds tend to suggest higher amplitudes in the high frequency end of the spectrum, this is not always true. Also, the high frequency end of the spectrum is not accurately described by simple wind statistics such as standard deviation and turbulence intensity. 2 refs., 5 figs., 1 tab.
Dependence of the Cosmic Microwave Background Lensing Power Spectrum on the Matter Density
Pan, Z; White, M
2014-01-01
The anisotropies in the cosmic microwave background (CMB) provide our best laboratory for testing models of the formation and evolution of large-scale structure. The rich features in the cosmic microwave background anisotropy spectrum, in combination with highly precise observations and theoretical predictions, also allow us to simultaneously constrain a number of cosmological parameters. As observations have progressed, measurements at smaller angular scales have provided increasing leverage. These smaller angular scales provide sensitive measures of the matter density through the effect of gravitational lensing. In this work we provide an analytic explanation of the manner in which the lensing of CMB anisotropies depends on the matter density, finding that the dominant effect comes from the shape of the matter power spectrum set by the decay of small-scale potentials between horizon crossing and matter-radiation equality.
Large Scale Magnetic Fields: Density Power Spectrum in Redshift Space
Rajesh Gopal; Shiv K. Sethi
2003-09-01
We compute the density redshift-space power spectrum in the presence of tangled magnetic fields and compare it with existing observations. Our analysis shows that if these magnetic fields originated in the early universe then it is possible to construct models for which the shape of the power spectrum agrees with the large scale slope of the observed power spectrum. However requiring compatibility with observed CMBR anisotropies, the normalization of the power spectrum is too low for magnetic fields to have significant impact on the large scale structure at present. Magnetic fields of a more recent origin generically give density power spectrum ∝ 4 which doesn’t agree with the shape of the observed power spectrum at any scale. Magnetic fields generate curl modes of the velocity field which increase both the quadrupole and hexadecapole of the redshift space power spectrum. For curl modes, the hexadecapole dominates over quadrupole. So the presence of curl modes could be indicated by an anomalously large hexadecapole, which has not yet been computed from observation. It appears difficult to construct models in which tangled magnetic fields could have played a major role in shaping the large scale structure in the present epoch. However if they did, one of the best ways to infer their presence would be from the redshift space effects in the density power spectrum.
Jabir, M V; Apurv Chaitanya, N; Aadhi, A; Samanta, G K
2016-01-01
The "perfect" vortex is a new class of optical vortex beam having ring radius independent of its topological charge (order). One of the simplest techniques to generate such beams is the Fourier transformation of the Bessel-Gauss beams. The variation in ring radius of such vortices require Fourier lenses of different focal lengths and or complicated imaging setup. Here we report a novel experimental scheme to generate perfect vortex of any ring radius using a convex lens and an axicon. As a proof of principle, using a lens of focal length f = 200 mm, we have varied the radius of the vortex beam across 0.3-1.18 mm simply by adjusting the separation between the lens and axicon. This is also a simple scheme to measure the apex angle of an axicon with ease. Using such vortices we have studied non-collinear interaction of photons having orbital angular momentum (OAM) in spontaneous parametric down-conversion (SPDC) process and observed that the angular spectrum of the SPDC photons are independent of OAM of the pump photons rather depends on spatial profile of the pump beam. In the presence of spatial walk-off effect in nonlinear crystals, the SPDC photons have asymmetric angular spectrum with reducing asymmetry at increasing vortex radius. PMID:26912184
Power spectrum extraction for redshifted 21-cm Epoch of Reionization experiments: the LOFAR case
Harker, Geraint; Zaroubi, Saleem; Bernardi, Gianni; Brentjens, Michiel A.; de Bruyn, A. G.; Ciardi, Benedetta; Jelić, Vibor; Koopmans, Leon V. E.; Labropoulos, Panagiotis; Mellema, Garrelt; Offringa, André; Pandey, V. N.; Pawlik, Andreas H.; Schaye, Joop; Thomas, Rajat M.; Yatawatta, Sarod
2010-07-01
One of the aims of the Low Frequency Array (LOFAR) Epoch of Reionization (EoR) project is to measure the power spectrum of variations in the intensity of redshifted 21-cm radiation from the EoR. The sensitivity with which this power spectrum can be estimated depends on the level of thermal noise and sample variance, and also on the systematic errors arising from the extraction process, in particular from the subtraction of foreground contamination. We model the extraction process using realistic simulations of the cosmological signal, the foregrounds and noise, and so estimate the sensitivity of the LOFAR EoR experiment to the redshifted 21-cm power spectrum. Detection of emission from the EoR should be possible within 360 h of observation with a single station beam. Integrating for longer, and synthesizing multiple station beams within the primary (tile) beam, then enables us to extract progressively more accurate estimates of the power at a greater range of scales and redshifts. We discuss different observational strategies which compromise between depth of observation, sky coverage and frequency coverage. A plan in which lower frequencies receive a larger fraction of the time appears to be promising. We also study the nature of the bias which foreground fitting errors induce on the inferred power spectrum and discuss how to reduce and correct for this bias. The angular and line-of-sight power spectra have different merits in this respect, and we suggest considering them separately in the analysis of LOFAR data.
The dijet mass spectrum and angular distributions with the D0 detector
We present preliminary results from an analysis of dijet data collected during the 1994-95 Tevatron Collider run with an integrated luminosity of 91 pb-1. Measurements of dijet mass spectra and dijet angular distributions in anti pp collisions at √s- = 1.8 TeV are compared with next-to-leading order QCD theory
The thermal Sunyaev Zel'dovich effect power spectrum in light of Planck
McCarthy, Ian G; Schaye, Joop; Holder, Gilbert P
2013-01-01
(Abridged) The amplitude of the thermal Sunyaev Zel'dovich effect (tSZ) power spectrum is extremely sensitive to the abundance of galaxy clusters and therefore to fundamental cosmological parameters that control their growth, such as sigma_8 and Omega_m. Here we explore the sensitivity of the tSZ power spectrum to important non-gravitational ('sub-grid') physics by employing the cosmo-OWLS suite of large-volume cosmological hydrodynamical simulations, run in both the Planck and WMAP7 best-fit cosmologies. On intermediate and small angular scales (ell > ~1000, or theta < ~10 arcmin), accessible with the South Pole Telescope and the Atacama Cosmology Telescope, the predicted tSZ power spectrum is highly model dependent, with AGN feedback having a particularly large effect. However, at large scales, observable with the Planck telescope, the effects of sub-grid physics are minor. Comparing the simulations with observations, we find a significant amplitude offset on all measured angular scales (including large ...
Estimating Discrete Power Angular Spectra in Multiprobe OTA Setups
Fan, Wei; Nielsen, Jesper Ødum; Pedersen, Gert Frølund
2014-01-01
accurate direction-of-arrival estimates as well as power estimates of the impinging signals in the test zone. Simulation results match well with the target, as expected. Measurement results based on a virtual UCA in a practical 3-D multiprobe setup further support the simulation results. Possible reasons...
Reference MWA EoR Power Spectrum analysis
Hazelton, Bryna; Pober, Jonathan; Beardsley, Adam; Morales, Miguel F.; Sullivan, Ian S.; MWA Collaboration
2015-01-01
Observations of the Epoch of Reionization using redshifted 21cm HI emission promise to provide sensitive new cosmological constraints in the next few years. The current generation of HI EoR telescopes are targeting a statistical detection of the EoR in the power spectrum of the 21cm emission. The principal challenge lies in extracting the faint cosmological signal in the face of bright foregrounds and instrumental systematics that threaten to overwhelm it.We present the UW EoR power spectrum code, the reference code for the MWA and the first power spectrum analysis to analytically propagate the error bars through the full data analysis pipeline. We demonstrate the sensitivity of the power spectrum as a diagnostic tool for identifying subtle systematics and show power spectra of the first season of MWA observations.
The Murchison Widefield Array 21 cm Power Spectrum Analysis Methodology
Jacobs, Daniel C; Trott, C M; Dillon, Joshua S; Pindor, B; Sullivan, I S; Pober, J C; Barry, N; Beardsley, A P; Bernardi, G; Bowman, Judd D; Briggs, F; Cappallo, R J; Carroll, P; Corey, B E; de Oliveira-Costa, A; Emrich, D; Ewall-Wice, A; Feng, L; Gaensler, B M; Goeke, R; Greenhill, L J; Hewitt, J N; Hurley-Walker, N; Johnston-Hollitt, M; Kaplan, D L; Kasper, J C; Kim, H S; Kratzenberg, E; Lenc, E; Line, J; Loeb, A; Lonsdale, C J; Lynch, M J; McKinley, B; McWhirter, S R; Mitchell, D A; Morales, M F; Morgan, E; Neben, A R; Thyagarajan, N; Oberoi, D; Offringa, A R; Ord, S M; Paul, S; Prabu, T; Procopio, P; Riding, J; Rogers, A E E; Roshi, A; Shankar, N Udaya; Sethi, Shiv K; Srivani, K S; Subrahmanyan, R; Tegmark, M; Tingay, S J; Waterson, M; Wayth, R B; Webster, R L; Whitney, A R; Williams, A; Williams, C L; Wu, C; Wyithe, J S B
2016-01-01
We present the 21 cm power spectrum analysis approach of the Murchison Widefield Array Epoch of Reionization project. In this paper, we compare the outputs of multiple pipelines for the purpose of validating statistical limits cosmological hydrogen at redshifts between 6 and 12. Multiple, independent, data calibration and reduction pipelines are used to make power spectrum limits on a fiducial night of data. Comparing the outputs of imaging and power spectrum stages highlights differences in calibration, foreground subtraction and power spectrum calculation. The power spectra found using these different methods span a space defined by the various tradeoffs between speed, accuracy, and systematic control. Lessons learned from comparing the pipelines range from the algorithmic to the prosaically mundane; all demonstrate the many pitfalls of neglecting reproducibility. We briefly discuss the way these different methods attempt to handle the question of evaluating a significant detection in the presence of foregr...
Kayo, Issha
2013-01-01
We re-examine a genuine power of weak lensing bispectrum tomography for constraining cosmological parameters, when combined with the power spectrum tomography, based on the Fisher information matrix formalism. To account for the full information at two- and three-point levels, we include all the power spectrum and bispectrum information built from all-available combinations of tomographic redshift bins, multipole bins and different triangle configurations over a range of angular scales (up to lmax=2000 as our fiducial choice). For the parameter forecast, we use the halo model approach in Kayo, Takada & Jain (2013) to model the non-Gaussian error covariances as well as the cross-covariance between the power spectrum and the bispectrum, including the halo sample variance or the nonlinear version of beat-coupling. We find that adding the bispectrum information leads to about 60% improvement in the dark energy figure-of-merit compared to the lensing power spectrum tomography alone, for three redshift-bin tomo...
Das, Sudeep [Argonne National Laboratory, 9700 S. Cass Ave., Lemont, IL 60439 (United States); Louis, Thibaut; Calabrese, Erminia; Dunkley, Joanna [Sub-department of Astrophysics, University of Oxford, Keble Road, Oxford, OX1 3RH (United Kingdom); Nolta, Michael R.; Bond, J Richard; Hajian, Amir; Hincks, Adam D. [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON, M5S 3H8 Canada (Canada); Addison, Graeme E.; Halpern, Mark [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z4 Canada (Canada); Battistelli, Elia S. [Department of Physics, University of Rome ' ' La Sapienza' ' , Piazzale Aldo Moro 5, I-00185 Rome (Italy); Crichton, Devin; Gralla, Megan [Dept. of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218-2686 (United States); Devlin, Mark J.; Dicker, Simon [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA, 19104 (United States); Dünner, Rolando [Departamento de Astronomía y Astrofísica, Facultad de Física, Pontificía Universidad Católica, Casilla 306, Santiago 22 (Chile); Fowler, Joseph W. [NIST Quantum Devices Group, 325 Broadway Mailcode 817.03, Boulder, CO, 80305 (United States); Hasselfield, Matthew; Hlozek, Renée [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States); Hilton, Matt, E-mail: sudeepphys@gmail.com [Centre for Astronomy and Particle Theory, School of Physics and Astronomy, University of Nottingham, NG7 2RD (United Kingdom); and others
2014-04-01
We present the temperature power spectra of the cosmic microwave background (CMB) derived from the three seasons of data from the Atacama Cosmology Telescope (ACT) at 148 GHz and 218 GHz, as well as the cross-frequency spectrum between the two channels. We detect and correct for contamination due to the Galactic cirrus in our equatorial maps. We present the results of a number of tests for possible systematic error and conclude that any effects are not significant compared to the statistical errors we quote. Where they overlap, we cross-correlate the ACT and the South Pole Telescope (SPT) maps and show they are consistent. The measurements of higher-order peaks in the CMB power spectrum provide an additional test of the ΛCDM cosmological model, and help constrain extensions beyond the standard model. The small angular scale power spectrum also provides constraining power on the Sunyaev-Zel'dovich effects and extragalactic foregrounds. We also present a measurement of the CMB gravitational lensing convergence power spectrum at 4.6σ detection significance.
Das, Sudeep; Louis, Thibaut; Nolta, Michael R.; Addison, Graeme E.; Battisetti, Elia S.; Bond, J. Richard; Calabrese, Erminia; Crichton, Devin; Devlin, Mark J.; Dicker, Simon; Dunkley, Joanna; Dunner, Rolando; Fowler, Joseph W.; Gralla, Megan; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hilton, Matt; Hincks, Adam D.; Hlozek, Renee; Huffenberger, Kevin M.; Hughes, John P.; Irwin, Kent D; Kosowsky, Arthur; Wollack, Ed
2014-01-01
We present the temperature power spectra of the cosmic microwave background (CMB) derived from the three seasons of data from the Atacama Cosmology Telescope (ACT) at 148 GHz and 218 GHz, as well as the cross-frequency spectrum between the two channels. We detect and correct for contamination due to the Galactic cirrus in our equatorial maps. We present the results of a number of tests for possible systematic error and conclude that any effects are not significant compared to the statistical errors we quote. Where they overlap, we cross-correlate the ACT and the South Pole Telescope (SPT) maps and show they are consistent. The measurements of higher-order peaks in the CMB power spectrum provide an additional test of the ?CDM cosmological model, and help constrain extensions beyond the standard model. The small angular scale power spectrum also provides constraining power on the Sunyaev-Zel'dovich effects and extragalactic foregrounds. We also present a measurement of the CMB gravitational lensing convergence power spectrum at 4.6s detection significance.
We present the temperature power spectra of the cosmic microwave background (CMB) derived from the three seasons of data from the Atacama Cosmology Telescope (ACT) at 148 GHz and 218 GHz, as well as the cross-frequency spectrum between the two channels. We detect and correct for contamination due to the Galactic cirrus in our equatorial maps. We present the results of a number of tests for possible systematic error and conclude that any effects are not significant compared to the statistical errors we quote. Where they overlap, we cross-correlate the ACT and the South Pole Telescope (SPT) maps and show they are consistent. The measurements of higher-order peaks in the CMB power spectrum provide an additional test of the ΛCDM cosmological model, and help constrain extensions beyond the standard model. The small angular scale power spectrum also provides constraining power on the Sunyaev-Zel'dovich effects and extragalactic foregrounds. We also present a measurement of the CMB gravitational lensing convergence power spectrum at 4.6σ detection significance
Piccirillo, Bruno; Slussarenko, Sergei; Marrucci, Lorenzo; Santamato, Enrico
2015-01-01
The standard method for experimentally determining the probability distribution of an observable in quantum mechanics is the measurement of the observable spectrum. However, for infinite-dimensional degrees of freedom, this approach would require ideally infinite or, more realistically, a very large number of measurements. Here we consider an alternative method which can yield the mean and variance of an observable of an infinite-dimensional system by measuring only a two-dimensional pointer weakly coupled with the system. In our demonstrative implementation, we determine both the mean and the variance of the orbital angular momentum of a light beam without acquiring the entire spectrum, but measuring the Stokes parameters of the optical polarization (acting as pointer), after the beam has suffered a suitable spin–orbit weak interaction. This example can provide a paradigm for a new class of useful weak quantum measurements. PMID:26477715
Piccirillo, Bruno; Slussarenko, Sergei; Marrucci, Lorenzo; Santamato, Enrico
2015-10-01
The standard method for experimentally determining the probability distribution of an observable in quantum mechanics is the measurement of the observable spectrum. However, for infinite-dimensional degrees of freedom, this approach would require ideally infinite or, more realistically, a very large number of measurements. Here we consider an alternative method which can yield the mean and variance of an observable of an infinite-dimensional system by measuring only a two-dimensional pointer weakly coupled with the system. In our demonstrative implementation, we determine both the mean and the variance of the orbital angular momentum of a light beam without acquiring the entire spectrum, but measuring the Stokes parameters of the optical polarization (acting as pointer), after the beam has suffered a suitable spin-orbit weak interaction. This example can provide a paradigm for a new class of useful weak quantum measurements.
Aghanim, N; Ashdown, M; Aumont, J; Ballardini, M; Banday, A J; Barreiro, R B; Bartolo, N; Basak, S; Benabed, K; Bersanelli, M; Bielewicz, P; Bonaldi, A; Bonavera, L; Bond, J R; Borrill, J; Bouchet, F R; Burigana, C; Calabrese, E; Cardoso, J -F; Challinor, A; Chiang, H C; Colombo, L P L; Combet, C; Crill, B P; Curto, A; Cuttaia, F; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; Di Valentino, E; Dickinson, C; Diego, J M; Doré, O; Ducout, A; Dupac, X; Dusini, S; Efstathiou, G; Elsner, F; Enßlin, T A; Eriksen, H K; Fantaye, Y; Finelli, F; Forastieri, F; Frailis, M; Franceschi, E; Frolov, A; Galeotta, S; Galli, S; Ganga, K; Génova-Santos, R T; Gerbino, M; González-Nuevo, J; Górski, K M; Gruppuso, A; Gudmundsson, J E; Herranz, D; Hivon, E; Huang, Z; Jaffe, A H; Jones, W C; Keihänen, E; Keskitalo, R; Kiiveri, K; Kim, J; Kisner, T S; Knox, L; Krachmalnicoff, N; Kunz, M; Kurki-Suonio, H; Lagache, G; Lamarre, J -M; Lasenby, A; Lattanzi, M; Lawrence, C R; Jeune, M Le; Levrier, F; Lewis, A; Lilje, P B; Lilley, M; Lindholm, V; López-Caniego, M; Lubin, P M; Ma, Y -Z; Macías-Pérez, J F; Maggio, G; Maino, D; Mandolesi, N; Mangilli, A; Maris, M; Martin, P G; Martínez-González, E; Matarrese, S; Mauri, N; McEwen, J D; Meinhold, P R; Mennella, A; Migliaccio, M; Millea, M; Miville-Deschênes, M -A; Molinari, D; Moneti, A; Montier, L; Morgante, G; Moss, A; Narimani, A; Natoli, P; Oxborrow, C A; Pagano, L; Paoletti, D; Patanchon, G; Patrizii, L; Pettorino, V; Piacentini, F; Polastri, L; Polenta, G; Puget, J -L; Rachen, J P; Racine, B; Reinecke, M; Remazeilles, M; Renzi, A; Rossetti, M; Roudier, G; Rubiño-Martín, J A; Ruiz-Granados, B; Salvati, L; Sandri, M; Savelainen, M; Scott, D; Sirignano, C; Sirri, G; Stanco, L; Suur-Uski, A -S; Tauber, J A; Tavagnacco, D; Tenti, M; Toffolatti, L; Tomasi, M; Tristram, M; Trombetti, T; Valiviita, J; Van Tent, F; Vielva, P; Villa, F; Vittorio, N; Wandelt, B D; Wehus, I K; White, M; Zacchei, A; Zonca, A
2016-01-01
The six parameters of the standard $\\Lambda$CDM 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 never before been measured to cosmic-variance level precision. We investigate 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 $\\tau$, the baryon density $\\omega_{\\rm b}$, the matter density $\\omega_{\\rm m}$, the angular size of the sound horizon $\\theta_*$, the spectral index of the primordial power spectrum, $n_{\\rm s}$, and $A_{\\rm s}e^{-2\\tau}$ (where $A_{\\rm s}$ is the amplitude of the primordial power spectrum), we examine the change in best-fit values between a WMAP-like large angular-scale data set (with multipole moment $\\ell800$, or splitting at ...
Asymptotic Spectrum of Kerr Black Holes in the Small Angular Momentum Limit
Daghigh, Ramin G; Mulligan, Brian W
2010-01-01
We study analytically the highly damped quasinormal modes of Kerr black holes in the small angular momentum limit. To check the previous analytic calculations in the literature, which use a combination of radial and tortoise coordinates, we reproduce all the results using the radial coordinate only. According to the earlier calculations, the real part of the highly damped quasinormal mode frequency of Kerr black holes approaches zero in the limit where the angular momentum goes to zero. This result is not consistent with the Schwarzschild limit where the real part of the highly damped quasinormal mode frequency is equal to c^3 ln(3)/(8 pi G M). In this paper, our calculations suggest that the highly damped quasinormal modes of Kerr black holes in the zero angular momentum limit make a continuous transition from the Kerr value to the Schwarzschild value. We explore the nature of this transition using a combination of analytical and numerical techniques. Finally, we calculate the highly damped quasinormal modes...
Soheyli, Saeed; Khanlari, Marzieh Varasteh
2016-04-01
Effects of the various neutron emission energy spectra, as well as the influence of the angular momentum of pre-scission neutrons on theoretical predictions of fission fragment angular anisotropies for several heavy-ion induced fission systems are considered. Although theoretical calculations of angular anisotropy are very sensitive to neutron emission correction, the effects of the different values of kinetic energy of emitted neutrons derived from the various neutron emission energy spectra before reaching to the saddle point on the prediction of fission fragment angular distribution by the model are not significant and can be neglected, since these effects on angular anisotropies of fission fragments for a wide range of fissility parameters and excitation energies of compound nuclei are not more than 10%. Furthermore, the theoretical prediction of fission fragment angular anisotropy is not sensitive to the angular momentum of emitted neutrons.
The CMB Power Spectrum from the Background Emission Anisotropy Scanning Telescope (BEAST) Experiment
O'Dwyer, I J; Childers, J; Figueiredo, N; Halevi, D; Huey, G G; Lubin, P M; Maino, D; Mandolesi, N; Marvil, J; Meinhold, P R; Mejia, J; Natoli, P; O'Neill, H; Pina, A; Seiffert, M D; Stebor, N C; Tello, C A S; Villela, T; Wandelt, B D; Williams, B; Wünsche, C A; Dwyer, Ian J. O'; Bersanelli, Marco; Childers, Jeffrey; Figueiredo, Newton; Halevi, Doron; Huey, Gregory G.; Lubin, Philip M.; Maino, Davide; Mandolesi, Nazzareno; Marvil, Joshua; Meinhold, Peter R.; Mejia, Jorge; Natoli, Paolo; Neill, Hugh O'; Pina, Agenor; Seiffert, Michael D.; Stebor, Nathan C.; Tello, Camilo; Villela, Thyrso; Wandelt, Benjamin D.; Williams, Brian; Wuensche, Carlos Alexandre
2003-01-01
The Background Emission Anisotropy Scanning Telescope (BEAST) is a 2.2m off-axis telescope with an 8 element mixed Q (38-45GHz) and Ka (26-36GHz) band focal plane, designed for balloon borne and ground based studies of the Cosmic Microwave Background. Here we present the Cosmic Microwave Background (CMB) angular power spectrum calculated from 682 hours of data observed with the BEAST instrument. We use a binned pseudo-Cl estimator (the MASTER method). We find results that are consistent with other determinations of the CMB anisotropy for angular wavenumber l between 100 and 600. We also perform cosmological parameter estimation. The BEAST data alone produces a good constraint on Omega_k = 1-Omega_tot=-0.074 +/- 0.070, consistent with a flat Universe. A joint parameter estimation analysis with a number of previous CMB experiments produces results consistent with previous determinations.
The CMB Power Spectrum from the Background Emission Anisotropy Scanning Telescope (BEAST) Experiment
O'Dwyer, Ian J.; Bersanelli, Marco; Childers, Jeffrey; Figueiredo, Newton; Halevi, Doron; Huey, Gregory G.; Lubin, Philip M.; Maino, Davide; Mandolesi, Nazzareno; Marvil, Joshua; Meinhold, Peter R.; Mejia, Jorge; Natoli, Paolo; O'Neill, Hugh,; Pina, Agenor
2003-01-01
The Background Emission Anisotropy Scanning Telescope (BEAST) is a 2.2m off-axis telescope with an 8 element mixed Q (38-45GHz) and Ka (26-36GHz) band focal plane, designed for balloon borne and ground based studies of the Cosmic Microwave Background. Here we present the Cosmic Microwave Background (CMB) angular power spectrum calculated from 682 hours of data observed with the BEAST instrument. We use a binned pseudo-Cl estimator (the MASTER method). We find results that are consistent with ...
1/f noise in music and speech. [Power spectrum studies
Voss, R.F.; Clarke, J.
1975-11-27
The power spectrum, S(f), of many fluctuating physical variables, V(t), is approximately ''1/f-like.'' Loudness fluctuations in music and speech and pitch (melody) fluctuations in music were found to exhibit 1/f power spectra. This observation has implications for stochastic music composition. 3 figures. (RWR)
Angular measurement of the Cobalt-60 emitted radiation spectrum from a radiosurgery irradiator
The photon energy spectrum emanating from a Leksell Gamma Knife, Model 23004B, was measured between 0.250 and 3.5 MeV with the sources exposed. Measurements were made using a 2x2 inch NaI detector enclosed in a lead-shielded apparatus having a (1/4) inch diameter measurement aperture, which reduced the amount of radiation received by the crystal. All measurements were made one meter above the floor within a quadrant toward one side of the Gamma Knife couch. The measured spectra displayed the expected 60Co doublet of photon peaks at energies of 1.17 and 1.33 MeV. These peaks appeared in spectra beginning at ∼50 degrees, as one proceeds from a point directly lateral to the source enclosure (0 degrees) toward the foot of the couch (90 degrees). The average photon energy of the spectrum shifts to lower values as the doublet decreases in magnitude with increasing angle until almost vanishing at an angle equal to 90 degrees. Inserting a 16 cm diameter plastic sphere phantom, provided with the Gamma Knife, into the radiation beams increases the low energy photon emissions appearing in the spectrum, especially for measurements at the foot of the couch. Implications for the design of shielding a treatment room containing the Gamma Knife, Model B, and estimation of the radiation exposure to personnel during an emergency procedure in the treatment room with the sources exposed are discussed
Angular measurement of the cobalt-60 emitted radiation spectrum from a radiosurgery irradiator.
Drzymala, R E; Sohn, J W; Guo, C; Sobotka, L G; Purdy, J A
2001-04-01
The photon energy spectrum emanating from a Leksell Gamma Knife, Model 23004B, was measured between 0.250 and 3.5 MeV with the sources exposed. Measurements were made using a 2x2 inch NaI detector enclosed in a lead-shielded apparatus having a 1/4 inch diameter measurement aperture, which reduced the amount of radiation received by the crystal. All measurements were made one meter above the floor within a quadrant toward one side of the Gamma Knife couch. The measured spectra displayed the expected 60Co doublet of photon peaks at energies of 1.17 and 1.33 MeV. These peaks appeared in spectra beginning at approximately 50 degrees, as one proceeds from a point directly lateral to the source enclosure (0 degrees) toward the foot of the couch (90 degrees). The average photon energy of the spectrum shifts to lower values as the doublet decreases in magnitude with increasing angle until almost vanishing at an angle equal to 90 degrees. Inserting a 16 cm diameter plastic sphere phantom, provided with the Gamma Knife, into the radiation beams increases the low energy photon emissions appearing in the spectrum, especially for measurements at the foot of the couch. Implications for the design of shielding a treatment room containing the Gamma Knife, Model B, and estimation of the radiation exposure to personnel during an emergency procedure in the treatment room with the sources exposed are discussed. PMID:11339760
On the information content of the matter power spectrum
Carron, J.; Wolk, M.; Szapudi, I.
2015-10-01
We discuss an analytical approximation for the matter power spectrum covariance matrix and its inverse on translinear scales, k ˜ 0.1h - 0.8 h Mpc-1 at z = 0. We proceed to give an analytical expression for the Fisher information matrix of the non-linear density-field spectrum, and derive implications for its cosmological information content. We find that the spectrum information is characterized by a pair of upper bounds, `plateaux', caused by the trispectrum, and a `knee' in the presence of white noise. The effective number of Fourier modes, normally growing as a power law, is bounded from above by these plateaux, explaining naturally earlier findings from N-body simulations. These plateaux limit best possible measurements of the non-linear power at the per cent level in an h-3 Gpc3 volume; the extraction of model parameters from the spectrum is limited explicitly by their degeneracy to the non-linear amplitude. The value of the first, supersurvey (SS) plateau depends on the characteristic survey volume and the large-scale power; the second, intra-survey plateau is set by the small-scale power. While both have simple interpretations within the hierarchical Ansatz, the SS plateau can be predicted and generalized to still smaller scales within Takada and Hu's spectrum response formalism. Finally, the noise knee is naturally set by the density of tracers.
Probing the primordial power spectrum with cluster number counts
We investigate how well galaxy cluster number counts can constrain the primordial power spectrum. Measurements of the primary anisotropies in the cosmic microwave background may be limited, by the presence of foregrounds from secondary sources, to probing the primordial power spectrum at wave numbers less than about 0.30h Mpc-1. We break up the primordial power spectrum into a number of nodes and interpolate linearly between each node. This allows us to show that cluster number counts could then extend the constraints on the form of the primordial power spectrum up to wave numbers of about 0.45h Mpc-1. We estimate combinations of constraints from PLANCK and SPT primary cosmic microwave background and their respective Sunyaev-Zeldovich surveys. We find that their constraining ability is limited by uncertainties in the mass-scaling relations. We also estimate the constraint from clusters detected from a SNAP-like gravitational lensing survey. As there is an unambiguous and simple relationship between the filtered shear of the lensing survey and the cluster mass, it may be possible to obtain much tighter constraints on the primordial power spectrum in this case.
Humeida, Yousif; Pinfield, Valerie J.; Challis, Richard E.
2013-08-01
Ultrasonic arrays have seen increasing use for the characterisation of composite materials. In this paper, ultrasonic wave propagation in multilayer anisotropic materials has been modelled using plane wave and angular spectrum decomposition techniques. Different matrix techniques, such as the stiffness matrix method and the transfer matrix method, are used to calculate the reflection and transmission coefficients of ultrasonic plane waves in the considered media. Then, an angular decomposition technique is used to derive the bounded beams from finite-width ultrasonic array elements from the plane wave responses calculated earlier. This model is considered to be an analytical exact solution for the problem; hence the diffraction of waves in such composite materials can be calculated for different incident angles for a very wide range of frequencies. This model is validated against experimental measurements using the Full-Matrix Capture (FMC) of array data in both a homogeneous isotropic material, i.e. aluminium, and an inhomogeneous multilayer anisotropic material, i.e. a carbon fibre reinforced composite.
Ultrasonic arrays have seen increasing use for the characterisation of composite materials. In this paper, ultrasonic wave propagation in multilayer anisotropic materials has been modelled using plane wave and angular spectrum decomposition techniques. Different matrix techniques, such as the stiffness matrix method and the transfer matrix method, are used to calculate the reflection and transmission coefficients of ultrasonic plane waves in the considered media. Then, an angular decomposition technique is used to derive the bounded beams from finite-width ultrasonic array elements from the plane wave responses calculated earlier. This model is considered to be an analytical exact solution for the problem; hence the diffraction of waves in such composite materials can be calculated for different incident angles for a very wide range of frequencies. This model is validated against experimental measurements using the Full-Matrix Capture (FMC) of array data in both a homogeneous isotropic material, i.e. aluminium, and an inhomogeneous multilayer anisotropic material, i.e. a carbon fibre reinforced composite
Jabir, M V; Aadhi, A; Samanta, G K
2016-01-01
The perfect vortex is a new class of optical vortex beam having ring radius independent of its topological charge (order). One of the simplest techniques to generate such beams is the Fourier transformation of the Bessel-Gauss beam. The variation in ring radius of such vortices require Fourier lenses of different focal lengths and or complicated imaging setup. Here we report a novel experimental scheme to generate perfect vortex of any ring radius using a convex lens and an axicon. As a proof of principle, using a lens of focal length f=200mm, we have varied the radius of the vortex beam across 0.3-1.18mm simply by adjusting the separation between the lens and axicon. This is also a simple scheme to measure the apex angle of an axicon with ease. Using such vortices we have studied non-collinear interaction of photons having orbital angular momentum (OAM) in spontaneous parametric down-conversion (SPDC) process and observed that the angular spectrum of the SPDC photons are independent of OAM of the pump photon...
Mauskopf, P.D.; Ade, P.A.R.; Bock, J.J.; Borrill, J.; Boscaleri, A.; Crill, B.P.; de Bernardis, P.; DeGasperis, G.; De Troia, G.; Farese, P.; Ferreira, P.G.; Ganga, K.; Giacometti, M.; Hanany, S.; Hristov, V.V.; Iacoangeli, A.; Jaffe, A.H.; Lange, A.E.; Lee, A.T.; Masi, S.; Melchiorri, A.; Melchiorri, F.; Miglio, L.; Montroy, T.; Netterfield, C.B.; Pascale, E.; Piacentini, F.; Richards, P.L.; Romeo, G.; Ruhl, J.E.; Scannapieco, E.; Scaramuzzi, F.; Stompor, R.; Vittorio, N.
1999-11-01
We describe a measurement of the angular power spectrum of anisotrophies in the Cosmic Microwave Background (CMB) from 0.2 deg to approx. 10 deg. from the test flight of the BOOMERANG experiment. BOOMERANG is a balloon-borne telescope with a bolometric receiver designed to map CMB anisotrophies on a Long Duration Balloon flight. During a 6-hour test flight of a prototype system in 1997, we mapped > 200 square degrees at high galactic latitudes in two bands centered at 90 and 150 GHz with a resolution of 26 and 16.6 arcmin FWHM respectively. Analysis of the maps gives a power spectrum with a peak at angular scales of approx. 1 deg. with an amplitude of approx. 70-muKcmb.
We describe a measurement of the angular power spectrum of anisotrophies in the Cosmic Microwave Background (CMB) from 0.2 deg to approx. 10 deg. from the test flight of the BOOMERANG experiment. BOOMERANG is a balloon-borne telescope with a bolometric receiver designed to map CMB anisotrophies on a Long Duration Balloon flight. During a 6-hour test flight of a prototype system in 1997, we mapped > 200 square degrees at high galactic latitudes in two bands centered at 90 and 150 GHz with a resolution of 26 and 16.6 arcmin FWHM respectively. Analysis of the maps gives a power spectrum with a peak at angular scales of approx. 1 deg. with an amplitude of approx. 70-muKcmb
Mauskopf, P D; De Bernardis, P; Bock, J J; Borrill, J; Boscaleri, A; Crill, B P; De Gasperis, G; De Troia, G; Farese, P; Ferreira, P G; Ganga, K; Giacometti, M; Hanany, S; Hristov, V V; Iacoangeli, A; Jaffe, A H; Lange, A E; Lee, A T; Masi, S; Melchiorri, A; Melchiorri, F; Miglio, L; Montroy, T; Netterfield, C B; Pascale, E; Piacentini, F; Richards, P L; Romeo, G; Ruhl, J E; Scannapieco, E S; Scaramuzzi, F; Stompor, R; Vittorio, N
2000-01-01
We describe a measurement of the angular power spectrum of anisotropies in the Cosmic Microwave Background (CMB) from 0.3 degrees to ~10 degrees from the North American test flight of the BOOMERANG experiment. BOOMERANG is a balloon-borne telescope with a bolometric receiver designed to map CMB anisotropies on a Long Duration Balloon flight. During a 6-hour test flight of a prototype system in 1997, we mapped > 200 square degrees at high galactic latitudes in two bands centered at 90 and 150 GHz with a resolution of 26 and 16.6 arcmin FWHM respectively. Analysis of the maps gives a power spectrum with a peak at angular scales of ~1 degree with an amplitude ~70 uK.
Das, Sudeep; Nolta, Michael R; Addison, Graeme E; Battistelli, Elia S; Bond, J Richard; Calabrese, Erminia; Devlin, Devin Crichton Mark J; Dicker, Simon; Dunkley, Joanna; Dünner, Rolando; Fowler, Joseph W; Gralla, Megan; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hilton, Matt; Hincks, Adam D; Hlozek, Renée; Huffenberger, Kevin M; Hughes, John P; Irwin, Kent D; Kosowsky, Arthur; Lupton, Robert H; Marriage, Tobias A; Marsden, Danica; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael D; Page, Lyman A; Partridge, Bruce; Reese, Erik D; Schmitt, Benjamin L; Sehgal, Neelima; Sherwin, Blake D; Sievers, Jonathan L; Spergel, David N; Staggs, Suzanne T; Swetz, Daniel S; Switzer, Eric R; Thornton, Robert; Trac, Hy; Wollack, Ed
2013-01-01
We present the temperature power spectra of the cosmic microwave background (CMB) derived from the three seasons of data from the Atacama Cosmology Telescope (ACT) at 148 GHz and 218 GHz, as well as the cross-frequency spectrum between the two channels. We detect and correct for contamination due to the Galactic cirrus in our equatorial maps. We present the results of a number of tests for possible systematic error and conclude that any effects are not significant compared to the statistical errors we quote. Where they overlap, we cross-correlate the ACT and the South Pole Telescope (SPT) maps and show they are consistent. The measurements of higher-order peaks in the CMB power spectrum provide an additional test of the Lambda CDM cosmological model, and help constrain extensions beyond the standard model. The small angular scale power spectrum also provides constraining power on the Sunyaev-Zel'dovich effects and extragalactic foregrounds. We also present a measurement of the CMB gravitational lensing conver...
Sunyaev-Zel'dovich power spectrum with decaying cold dark matter
Takahashi, Keitaro; Oguri, Masamune; Ichiki, Kiyotomo
2004-07-01
Recent studies of the structures of galaxies and clusters imply that dark matter might be unstable and may decay with lifetime Γ-1, about the age of the Universe. We study the effects of the decay of cold dark matter on the Sunyaev-Zel'dovich (SZ) power spectrum. We analytically calculate the SZ power spectrum taking the finite lifetime of cold dark matter into account. We find the finite lifetime of dark matter decreases the power at large scale (l 4000). This is in marked contrast with the dependence of other cosmological parameters such as the amplitude of mass fluctuations σ8 and the cosmological constant Ωλ (under the assumption of a flat Universe) which mainly change the normalization of the angular power spectrum. This difference allows one to determine the lifetime and other cosmological parameters separately. We also investigate the sensitivity of future SZ surveys to the cosmological parameters including the lifetime, assuming a fiducial model Γ-1 = 10 h-1 Gyr, σ8 = 1.0 and Ωλ = 0.7. We show that future SZ surveys such as ACT, AMIBA and BOLOCAM can determine the lifetime within a factor of 2 even if σ8 and Ωλ are marginalized.
Sunyaev-Zel'dovich power spectrum with decaying cold dark matter
Takahashi, K; Ichiki, K; Takahashi, Keitaro; Oguri, Masamune; Ichiki, Kiyotomo
2003-01-01
Recent studies of structures of galaxies and clusters imply that dark matter might be unstable and decay with lifetime $\\Gamma^{-1}$ about the age of universe. We study the effects of the decay of cold dark matter on the Sunyaev-Zel'dovich (SZ) power spectrum. We analytically calculate the SZ power spectrum taking finite lifetime of cold dark matter into account. We find the finite lifetime of dark matter decreases the power at large scale ($l 4000$). This is in marked contrast with the dependence of other cosmological parameters such as the amplitude of mass fluctuations $\\sigma_{8}$ and the cosmological constant $\\Omega_{\\lambda}$ (under the assumption of a flat universe) which mainly change the normalization of the angular power spectrum. This difference allows one to determine the lifetime and other cosmological parameters rather separately. We also investigate sensitivity of a future SZ survey to the cosmological parameters including the life time, assuming a fiducial model $\\Gamma^{-1} = 10 h^{-1} {\\rm...
Tilting the Primordial Power Spectrum with Bulk Viscosity
Lidsey, James E.
1993-01-01
Within the context of the cold dark matter model, current observations suggest that inflationary models which generate a tilted primordial power spectrum with negligible gravitational waves provide the most promising mechanism for explaining large scale clustering. The general form of the inflationary potential which produces such a spectrum is a hyperbolic function and is interpreted physically as a bulk viscous stress contribution to the energy-momentum of a perfect baryotropic fluid. This ...
Power Spectrum Estimation of Randomly Sampled Signals
Velte, Clara M.; Buchhave, Preben; K. George, William
2014-01-01
The random, but velocity dependent, sampling of the LDA presents non-trivial signal processing challengesdue to the high velocity bias and the arbitrariness of particle path through the measuring volume, among other factors.To obtain the desired non-biased statistics, it has previously been shown...... proportional to velocity magnitude that consist of well-defined frequency content, which makes bias easy to spot. The idea is that if the algorithms are not able to produce correct statistics from this simple signal, then they will certainly not be able to function well for a more complex measured LDA signal...... high data rate and low inherent bias, respectively, while residence time weighting provides non-biased estimates regardless of setting. The free-running processor was also tested and compared to residence time weighting using actual LDA measurements in a turbulent round jet. Power spectra from...
Power Spectrum Estimation of Randomly Sampled Signals
Velte, C. M.; Buchhave, P.; K. George, W.
The random, but velocity dependent, sampling of the LDA presents non-trivial signal processing challenges due to the high velocity bias and the arbitrariness of particle path through the measuring volume, among other factors. To obtain the desired non-biased statistics, it has previously been shown...... algorithms are not able to produce correct statistics from this simple signal, then they will certainly not be able to function well for a more complex measured LDA signal. This is, of course, true also for other methods that are based on the tested algorithms. The extremes are tested by increasing, e......, respectively. Residence time weighting provides non-biased estimates regardless of setting. The free-running processor was also tested and compared to residence time weighting using actual LDA measurements in a turbulent round jet. Power spectra from measurements on the jet centerline and the outer part of the...
Angular Signatures of Dark Matter in the Diffuse Gamma Ray Spectrum
Hooper, D; Hooper, Dan; Serpico, Pasquale D.
2007-01-01
Dark matter annihilating in our Galaxy's halo and elsewhere in the universe is expected to generate a diffuse flux of gamma rays, potentially observable with next generation satellite-based experiments, such as GLAST. In this article, we study the signatures of dark matter in the angular distribution of this radiation. Pertaining to the extragalactic contribution, we discuss the effect of the motion of the solar system with respect to the cosmological rest frame and anisotropies due to the structure of our local universe. For the gamma ray flux from dark matter in our own Galactic halo, we discuss the effects of the offset position of the solar system, the Compton-Getting effect, the asphericity of the Milky Way halo, and the signatures of nearby substructure. We explore the prospects for the detection of these features by the GLAST satellite and find that, if ~10% or more of the diffuse gamma ray background observed by EGRET is the result of dark matter annihilations, then GLAST should be sensitive to anisot...
Methods for Bayesian power spectrum inference with galaxy surveys
Jasche, Jens
2013-01-01
We derive and implement a full Bayesian large scale structure inference method aiming at precision recovery of the cosmological power spectrum from galaxy redshift surveys. Our approach improves over previous Bayesian methods by performing a joint inference of the three dimensional density field, the cosmological power spectrum, luminosity dependent galaxy biases and corresponding normalizations. We account for all joint and correlated uncertainties between all inferred quantities. Classes of galaxies with different biases are treated as separate sub samples. The method therefore also allows the combined analysis of more than one galaxy survey. In particular, it solves the problem of inferring the power spectrum from galaxy surveys with non-trivial survey geometries by exploring the joint posterior distribution with efficient implementations of multiple block Markov chain and Hybrid Monte Carlo methods. Our Markov sampler achieves high statistical efficiency in low signal to noise regimes by using a determini...
Joint resonant CMB power spectrum and bispectrum estimation
Meerburg, P Daniel; Wandelt, Benjamin
2015-01-01
We develop the tools necessary to assess the statistical significance of resonant features in the CMB correlation functions, combining power spectrum and bispectrum measurements. This significance is typically addressed by running a large number of simulations to derive the probability density function (PDF) of the feature-amplitude in the Gaussian case. Although these simulations are tractable for the power spectrum, for the bispectrum they require significant computational resources. We show that, by assuming that the PDF is given by a multi-variate Gaussian where the covariance is determined by the Fisher matrix of the sine and cosine terms, we can efficiently produce spectra that are statistically close to those derived from full simulations. By drawing a large number of spectra from this PDF, both for the power spectrum and the bispectrum, we can quickly determine the statistical significance of candidate signatures in the CMB, considering both single frequency and multi-frequency estimators. We show tha...
Methods for Bayesian Power Spectrum Inference with Galaxy Surveys
Jasche, Jens; Wandelt, Benjamin D.
2013-12-01
We derive and implement a full Bayesian large scale structure inference method aiming at precision recovery of the cosmological power spectrum from galaxy redshift surveys. Our approach improves upon previous Bayesian methods by performing a joint inference of the three-dimensional density field, the cosmological power spectrum, luminosity dependent galaxy biases, and corresponding normalizations. We account for all joint and correlated uncertainties between all inferred quantities. Classes of galaxies with different biases are treated as separate subsamples. This method therefore also allows the combined analysis of more than one galaxy survey. In particular, it solves the problem of inferring the power spectrum from galaxy surveys with non-trivial survey geometries by exploring the joint posterior distribution with efficient implementations of multiple block Markov chain and Hybrid Monte Carlo methods. Our Markov sampler achieves high statistical efficiency in low signal-to-noise regimes by using a deterministic reversible jump algorithm. This approach reduces the correlation length of the sampler by several orders of magnitude, turning the otherwise numerically unfeasible problem of joint parameter exploration into a numerically manageable task. We test our method on an artificial mock galaxy survey, emulating characteristic features of the Sloan Digital Sky Survey data release 7, such as its survey geometry and luminosity-dependent biases. These tests demonstrate the numerical feasibility of our large scale Bayesian inference frame work when the parameter space has millions of dimensions. This method reveals and correctly treats the anti-correlation between bias amplitudes and power spectrum, which are not taken into account in current approaches to power spectrum estimation, a 20% effect across large ranges in k space. In addition, this method results in constrained realizations of density fields obtained without assuming the power spectrum or bias parameters
Reexamination of the power spectrum in de Sitter inflation.
Agulló, Iván; Navarro-Salas, José; Olmo, Gonzalo J; Parker, Leonard
2008-10-24
We find that the amplitude of quantum fluctuations of the invariant de Sitter vacuum coincides exactly with that of the vacuum of a comoving observer for a massless scalar (inflaton) field. We propose redefining the actual physical power spectrum as the difference between the amplitudes of the above vacua. An inertial particle detector continues to observe the Gibbons-Hawking temperature. However, although the resulting power spectrum is still scale-free, its amplitude can be drastically reduced since now, instead of the Hubble's scale at the inflationary period, it is determined by the square of the mass of the inflaton fluctuation field. PMID:18999735
Diagnosis of power generator sets by analyzing the crank shaft angular speed
This thesis deals with the diagnosis of a powerful 20-cylinder diesel engine which runs a generator set in a nuclear plant. The objective is to make a diagnosis by analyzing the crank shaft angular speed variations. Only combustion related faults are investigated. As the engine is very large, the first crank shaft natural modes are in the low frequencies. Torsional vibrations of the flexible crank shaft strongly complicate the analysis of the angular speed variations. Little attention has been paid to such large engines in the literature. First, a dynamical model with the assumption of a flexible crank shaft is established. The parameters of the model are optimized with the help of actual data. Then, an original automated diagnosis based on pattern recognition of the angular speed waveforms is proposed. Indeed, any faulty cylinder in combustion stroke will distort the angular speed waveform in a specific way which depends on its location with respect to nodes and anti-nodes of the modes. Reference patterns, representative of the engine conditions, are computed with the model constituting the main originality of this work. Promising results are obtained in operational phase. An experimental fuel leakage fault was correctly diagnosed, including detection and localization of the faulty cylinder and an indication of the severity of the fault. (author)
Hirai, Shiro
2009-01-01
The Taylor expansion method has been used to investigate the scale dependence of the power spectrum of the curvature perturbation. In the present study, an alternative numerical method is used to clarify the $k$ dependence. Although there is thought to be no large difference between these two methods, some differences arise among various inflation models. For example, at $k$ = 1 Mpc, there is a 1.4 % difference in the power spectrum, and with respect to the angular power spectrum, the difference of the value of $\\chi^2$ nearly 10 occur in new inflation. However, in hybrid inflation, these differences do not occur. The time dependence of the inflationary and cosmological parameters is investigated, and differences among inflation models are clarified.
Hirai, Shiro
2007-01-01
The effect of the initial condition of inflation on the power spectra of scalar and tensor perturbations is estimated assuming a slow-roll inflation model. By defining a more general initial state in inflation particular properties of the power spectrum such as oscillation can be revealed. The behavior of the power spectrum is shown to exhibit a step-like variation with respect to finite inflation length in cases of both radiation- and scalar matter-dominated pre-inflation. The power spectrum is shown to oscillate in the radiation-dominated case. The effects of such a power spectrum on the TT and TE power spectra are examined for three typical slow-roll inflation models; a small-field model, a large field model, and a hybrid model, considering both pre-inflation models. It is found that the discrepancies between WMAP3 data and the Lambda CDM model, such as suppression of the spectrum at l=2, may be explained to a certain extent by the finite length of inflation for inflation of close to 60 e-folds. The small-...
WIND TURBINE SIMULATION FOR TIME-DEPENDENT ANGULAR VELOCITY, TORQUE, AND POWER
YONGHO LEE
2013-02-01
Full Text Available Albeit the prediction of time-dependent properties of wind turbines is not required for common applications, such time-varying properties may play an important role during transient operations occurring due to various reasons. Unlike the conventional numerical simulations of wind turbine rotations that fix the angular velocity to an assumed value, the present work numerically simulates the time-varying turbine rotation in both unsteady and quasi-steady operation regimes, without specifying the angular velocity of the turbine a priori, but by calculating the actual time-dependent angular velocity and aerodynamic torque along with other properties in the course of simulation. In the present work, successful results obtained by an efficient computational fluid dynamics technique are shown, as a demonstration, for a vertical-axis wind turbine with a two-dimensionalSavonius rotor, and the cycle-averaged output powers are compared with experimental power curves and a theory developed on the basis of experimental observations.
Javahiraly, Nicolas; Chakari, Ayoub
2013-05-01
To achieve a very effective automotive power steering system, we need two important data, the angular position of the wheel and the torque applied on the shaft by the driver of the car. We present a new accurate optical fiber angular position sensor connected to an automotive power steering column. In this new design, the sensor allows the measurement of the angular position of a car steering wheel over a large and adjustable range (± several turns of the wheel). The wheel rotation induces micro-bending in the transducer part of the optical fiber sensing system. This system operates as an amplitude modulation sensor based on mode coupling in the transducing fiber in the case when all the modes are equally excited. We study the sensor response both theoretically and experimentally with a multimode step index optical fiber [rf (fiber radius) = 300 μm rc (core radius) = 50 μm nc (core index) = 1,457; N.A. = 0, 22 and the wavelength is 632,8 nm at the ambient Temperature (20°C)]. We show that the sensitivity can be controlled as a function of the sensor's length. We compare modeling and experimental validation and we conclude with a perspective on what could soon be an industrial sensor.
Matter density perturbation and power spectrum in running vacuum model
Geng, Chao-Qiang
2016-01-01
We investigate the matter density perturbation $\\delta_m$ and power spectrum $P(k)$ in the running vacuum model (RVM) with the cosmological constant being a function of the Hubble parameter, given by $\\Lambda = \\Lambda_0 + 6 \\sigma H H_0+ 3\
Joint resonant CMB power spectrum and bispectrum estimation
Meerburg, P. Daniel; Münchmeyer, Moritz; Wandelt, Benjamin
2016-02-01
We develop the tools necessary to assess the statistical significance of resonant features in the CMB correlation functions, combining power spectrum and bispectrum measurements. This significance is typically addressed by running a large number of simulations to derive the probability density function (PDF) of the feature-amplitude in the Gaussian case. Although these simulations are tractable for the power spectrum, for the bispectrum they require significant computational resources. We show that, by assuming that the PDF is given by a multivariate Gaussian where the covariance is determined by the Fisher matrix of the sine and cosine terms, we can efficiently produce spectra that are statistically close to those derived from full simulations. By drawing a large number of spectra from this PDF, both for the power spectrum and the bispectrum, we can quickly determine the statistical significance of candidate signatures in the CMB, considering both single frequency and multifrequency estimators. We show that for resonance models, cosmology and foreground parameters have little influence on the estimated amplitude, which allows us to simplify the analysis considerably. A more precise likelihood treatment can then be applied to candidate signatures only. We also discuss a modal expansion approach for the power spectrum, aimed at quickly scanning through large families of oscillating models.
Ebersole, K T; Housh, T J; Weir, J P; Johnson, G O; Evetovich, T K; Smith, D B
2000-01-01
The purpose of the present investigation was to examine the effects of leg angular velocity on the mean power frequency (MPF) and amplitude of the mechanomyographic (MMG) signal during maximal concentric (CON) isokinetic muscle actions. Sixteen adult subjects performed maximal CON leg extensions on a calibrated Cybex 6000 dynamometer at leg angular velocities of 60 and 300 degrees.s-1. MMG was detected by a piezoelectric crystal contact sensor placed over the mid-portion of the vastus lateralis muscle. The results indicated a significant (p 0.05) in MMG MPF. These findings did not support our hypothesis that increases across velocity in MMG amplitude were due to decreases in muscle stiffness as a result of a shift in the contribution of slow and fast-twitch muscle fibers to PT production. Future research should examine the potential influence of actin-myosin cycling rate as well as limb movement on the MPF and amplitude of the MMG signal. PMID:10782358
Spatial correlation in 3D MIMO channels using fourier coefficients of power spectrums
Nadeem, Qurrat Ul Ain
2015-03-01
In this paper, an exact closed-form expression for the Spatial Correlation Function (SCF) is derived for the standardized three-dimensional (3D) multiple-input multiple-output (MIMO) channel. This novel SCF is developed for a uniform linear array of antennas with non-isotropic antenna patterns. The proposed method resorts to the spherical harmonic expansion (SHE) of plane waves and the trigonometric expansion of Legendre and associated Legendre polynomials to obtain a closed-form expression for the SCF for arbitrary angular distributions and antenna patterns. The resulting expression depends on the underlying angular distributions and antenna patterns through the Fourier Series (FS) coefficients of power azimuth and elevation spectrums. The novelty of the proposed method lies in the SCF being valid for any 3D propagation environment. Numerical results validate the proposed analytical expression and study the impact of angular spreads on the correlation. The derived SCF will help evaluate the performance of correlated 3D MIMO channels in the future. © 2015 IEEE.
Unbiased pseudo-Cl power spectrum estimation with mode projection
Elsner, Franz; Peiris, Hiranya V
2016-01-01
With the steadily improving sensitivity afforded by current and future galaxy surveys, a robust extraction of two-point correlation function measurements may become increasingly hampered by the presence of astrophysical foregrounds or observational systematics. The concept of mode projection has been introduced as a means to remove contaminants for which it is possible to construct a spatial map reflecting the expected signal contribution. Owing to its computational efficiency compared to minimum-variance methods, the sub-optimal pseudo-Cl (PCL) power spectrum estimator is a popular tool for the analysis of high-resolution data sets. Here, we integrate mode projection into the framework of PCL power spectrum estimation. In contrast to results obtained with optimal estimators, we show that the uncorrected projection of template maps leads to biased power spectra. Based on analytical calculations, we find exact closed-form expressions for the expectation value of the bias and demonstrate that they can be recast...
The very low frequency power spectrum of Centaurus X-3
Gruber, D. E.
1988-01-01
The long-term variability of Cen X-3 on time scales ranging from days to years has been examined by combining data obtained by the HEAO 1 A-4 instrument with data from Vela 5B. A simple interpretation of the data is made in terms of the standard alpha-disk model of accretion disk structure and dynamics. Assuming that the low-frequency variance represents the inherent variability of the mass transfer from the companion, the decline in power at higher frequencies results from the leveling of radial structure in the accretion disk through viscous mixing. The shape of the observed power spectrum is shown to be in excellent agreement with a calculation based on a simplified form of this model. The observed low-frequency power spectrum of Cen X-3 is consistent with a disk in which viscous mixing occurs about as rapidly as possible and on the largest scale possible.
Primordial scalar power spectrum from the Euclidean big bounce
Schander, Susanne; Barrau, Aurélien; Bolliet, Boris; Linsefors, Linda; Mielczarek, Jakub; Grain, Julien
2016-01-01
In effective models of loop quantum cosmology, the holonomy corrections are associated with deformations of space-time symmetries. The most evident manifestation of the deformations is the emergence of a Euclidean phase accompanying the nonsingular bouncing dynamics of the scale factor. In this article, we compute the power spectrum of scalar perturbations generated in this model, with a massive scalar field as the matter content. Instantaneous and adiabatic vacuum-type initial conditions for scalar perturbations are imposed in the contracting phase. The evolution through the Euclidean region is calculated based on the extrapolation of the time direction pointed by the vectors normal to the Cauchy hypersurface in the Lorentzian domains. The obtained power spectrum is characterized by a suppression in the IR regime and oscillations in the intermediate energy range. Furthermore, the speculative extension of the analysis in the UV reveals a specific rise of the power leading to results incompatible with the data.
Constraining the primordial power spectrum from SNIa lensing dispersion
Ben-Dayan, Ido [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kalaydzhyan, Tigran [State Univ. of New York, Stony Brook, NY (United States). Dept. of Physics and Astronomy
2013-09-15
The (absence of detecting) lensing dispersion of Supernovae type Ia (SNIa) can be used as a novel and extremely efficient probe of cosmology. In this preliminary example we analyze its consequences for the primordial power spectrum. The main setback is the knowledge of the power spectrum in the non-linear regime, 1 Mpc{sup -1}
On the information content of the matter power spectrum
Carron, Julien; Szapudi, István
2014-01-01
We discuss an analytical approximation for the matter power spectrum covariance matrix and its inverse on translinear scales, $k \\sim 0.1h - 0.8h/\\textrm{Mpc}$ at $z = 0$. We proceed to give an analytical expression for the Fisher information matrix of the nonlinear density field spectrum, and derive implications for its cosmological information content. We find that the spectrum information is characterized by a pair of upper bounds, 'plateaux', caused by the trispectrum, and a 'knee' in the presence of white noise. The effective number of Fourier modes, normally growing as a power law, is bounded from above by these plateaux, explaining naturally earlier findings from $N$-body simulations. These plateaux limit best possible measurements of the nonlinear power at the percent level in a $h^{-3}\\textrm{Gpc}^3$ volume; the extraction of model parameters from the spectrum is limited explicitly by their degeneracy to the nonlinear amplitude. The value of the first, super-survey (SS) plateau depends on the charact...
Power spectrum of an injection-locked Josephson oscillator
Experiments have shown that a Josephson oscillator, exposed to a weak narrow-band input signal, exhibits behavior characteristic of an injection-locked oscillator. When in lock, Adler's theory of injection locking describes the experimental observations reasonably well. The range of applicability of the theory is extended to the out-of-lock regime where a spectrum of output frequencies is observed. Obtaining the theoretical output power spectrum requires solving a differential equation having the same form as the equation describing the resistively shunted junction model of Stewart and of McCumber. Experimental measurements of the output spectrum of a nearly locked Josephson oscillator are shown to be in reasonable agreement with the theory. Additional results discussed briefly include the observation of a frequency dependence of the locked Josephson oscillator output and experiments in which a Josephson oscillator-mixer was injection locked by a weak signal at the rf
Earthquake accelerogram simulation with statistical law of evolutionary power spectrum
ZHANG Cui-ran; CHEN Hou-qun; LI Min
2007-01-01
By using the technique for evolutionary power spectrum proposed by Nakayama and with reference to the Kameda formula, an evolutionary spectrum prediction model for given earthquake magnitude and distance is established based on the 80 near-source acceleration records at rock surface with large magnitude from the ground motion database of western U.S.. Then a new iteration method is developed for generation of random accelerograms non-stationary both in amplitude and frequency which are compatible with target evolutionary spectrum. The phase spectra of those simulated accelerograms are also non-stationary in time and frequency domains since the interaction between amplitude and phase angle has been considered during the generation. Furthermore, the sign of the phase spectrum increment is identified to accelerate the iteration. With the proposed statistical model for predicting evolutionary power spectra and the new method for generating compatible time history, the artificial random earthquake accelerograms non-stationary both in amplitude and frequency for certain magnitude and distance can be provided.
Power Spectrum Analysis of Polarized Emission from the Canadian Galactic Plane Survey
Stutz, R A; Kothes, R; Landecker, T
2014-01-01
Angular power spectra are calculated and presented for the entirety of the Canadian Galactic Plane Survey polarization dataset at 1.4 GHz covering an area of 1060 deg$^2$. The data analyzed are a combination of data from the 100-m Effelsberg Telescope, the 26-m Telescope at the Dominion Radio Astrophysical Observatory, and the Synthesis Telescope at the Dominion Radio Astrophysical Observatory, allowing all scales to be sampled down to arcminute resolution. The resulting power spectra cover multipoles from $\\ell \\approx 60$ to $\\ell \\approx 10^4$ and display both a power-law component at low multipoles and a flattening at high multipoles from point sources. We fit the power spectrum with a model that accounts for these components and instrumental effects. The resulting power-law indices are found to have a mode of 2.3, similar to previous results. However, there are significant regional variations in the index, defying attempts to characterize the emission with a single value. The power-law index is found to ...
Unbiased contaminant removal for 3D galaxy power spectrum measurements
Kalus, Benedict; Bacon, David; Samushia, Lado
2016-01-01
We assess and develop techniques to remove contaminants when calculating the 3D galaxy power spectrum. We separate the process into three separate stages: (i) removing the contaminant signal, (ii) estimating the uncontaminated cosmological power spectrum, (iii) debiasing the resulting estimates. For (i), we show that removing the best-fit contaminant (template subtraction), and setting the contaminated components of the covariance to be infinite (mode deprojection) are mathematically equivalent. For (ii), performing a Quadratic Maximum Likelihood (QML) estimate after mode deprojection gives an optimal unbiased solution, although it requires the manipulation of large $(N_{\\rm mode}^2)$ matrices, which is unfeasible for recent 3D galaxy surveys. Measuring a binned average of the modes for (ii) as proposed by Feldman, Kaiser & Peacock (1994, FKP) is faster and simpler, but is sub-optimal and gives rise to a biased solution. We present a method to debias the resulting FKP measurements that does not require an...
On Removing Interloper Contamination from Intensity Mapping Power Spectrum Measurements
Lidz, Adam
2016-01-01
Line intensity mapping experiments seek to trace large scale structure by measuring the spatial fluctuations in the combined emission, in some convenient spectral line, from individually unresolved galaxies. An important systematic concern for these surveys is line confusion from foreground or background galaxies emitting in other lines that happen to lie at the same observed frequency as the "target" emission line of interest. We develop an approach to separate this "interloper" emission at the power spectrum level. If one adopts the redshift of the target emission line in mapping from observed frequency and angle on the sky to co-moving units, the interloper emission is mapped to the wrong co-moving coordinates. Since the mapping is different in the line of sight and transverse directions, the interloper contribution to the power spectrum becomes anisotropic, especially if the interloper and target emission are at widely separated redshifts. This distortion is analogous to the Alcock-Paczynski test, but her...
The Turbulence Power Spectrum in Optically Thick Interstellar Clouds
Burkhart, Blakesley; Ossenkopf, V; Stutzki, J
2013-01-01
The Fourier power spectrum is one of the most widely used statistical tools to analyze the nature of magnetohydrodynamic turbulence in the interstellar medium. Lazarian & Pogosyan (2004) predicted that the spectral slope should saturate to -3 for an optically thick medium and many observations exist in support of their prediction. However, there have not been any numerical studies to-date testing these results. We analyze the spatial power spectrum of MHD simulations with a wide range of sonic and Alfv\\'enic Mach numbers, which include radiative transfer effects of the $^{13}$CO transition. We confirm numerically the predictions of Lazarian & Pogosyan (2004) that the spectral slope of line intensity maps of an optically thick medium saturates to -3. Furthermore, for very optically thin supersonic CO gas, where the density or CO abundance values are too low to excite emission in all but the densest shock compressed gas, we find that the spectral slope is shallower than expected from the column density....
Constraining the intra-cluster pressure profile from the thermal SZ power spectrum
Ramos-Ceja, M E; Pacaud, F; Bertoldi, F
2014-01-01
The angular power spectrum of the thermal Sunyaev-Zel'dovich (tSZ) effect is highly sensitive to cosmological parameters such as sigma8 and OmegaM, but its use as a precision cosmological probe is hindered by the astrophysical uncertainties in modeling the gas pressure profile in galaxy groups and clusters. In this paper we assume that the relevant cosmological parameters are accurately known, and explore the ability of current and future tSZ power spectrum measurements to constrain the intra-cluster gas pressure or the evolution of the gas mass fraction, f_gas. We use the CMB bandpower measurements from the South Pole Telescope and a Bayesian MCMC method to quantify deviations from the standard, universal gas pressure model. We explore analytical model extensions that bring the predictions for the tSZ power in agreement with experimental data. We find that a steeper pressure profile in the cluster outskirts or an evolving f_gas have mild to severe conflicts with experimental data or simulations. Varying more...
Testing the Rastall's theory using matter power spectrum
Batista, C. E. M.; Fabris, J. C.; Daouda, M. Hamani
2010-01-01
The Rastall's theory is a modification of the General Relativity theory leading to a different expression for the conservation law in the matter sector compared with the usual one. It has been argued recently that such a theory may have applications to the dark energy problem, since a pressureless fluid may lead to an accelerated universe. In the present work we confront the Rastall's theory with the power spectrum data. The results indicate a configuration that essentially reduces the Rastal...
Rejuvenating the Matter Power Spectrum III: The Cosmology Sensitivity of Gaussianized Power Spectra
Neyrinck, Mark C
2011-01-01
It was recently shown that applying a Gaussianizing transform, such as a logarithm, to the nonlinear matter density field extends the range of scales, by a factor of a few smaller, where the power spectrum excels at describing the ?field. Such a transform dramatically reduces nonlinearities in both the covariance and the shape of the power spectrum. Here, analyzing Coyote Universe real-space dark matter density fields, we investigate the consequences of these transforms for cosmological parameter estimation. The power spectrum of the log-density provides the tightest cosmological parameter error bars (marginalized or not), giving a factor of 2-3 improvement over the conventional power spectrum in all five parameters tested. For the tilt, n_s, the improvement reaches a factor of 5. Similar constraints are achieved if the log-density power spectrum and conventional power spectrum are analyzed together. Rank-order Gaussianization seems just as useful as a log transform to constrain n_s, but not other parameters....
Power spectrum for inflation models with thermal and quantum noises
Full text: In non-isentropic inflation models, most notably in warm inflation, there is a non negligible contribution from the radiation bath to the power spectrum. In fact, in warm inflation models the dominant contribution to density perturbations come from thermal fluctuations. This is opposite to the more common cold inflation models, where the quantum fluctuations of the inflation field make the sole contribution. Little or no importance has been given to those cases where neither quantum or thermal contributions make the dominant contribution to the power spectrum. In those situations, which in fact should cover most of the parameter space of realistic quantum field theory models for inflation, it is required a complete determination of both types of contributions and also to determine under which conditions one may eventually dominate over the other. This is a most required study since, as more precise measurements of the CMB rapidly become available, greater demand is placed on more precise theoretical predictions. This requires accounting for all important effects contributing to the density perturbations. For warm inflation, it requires knowing precisely when the eventual thermalized inflation fluctuations start effectively to dominate over the quantum ones and the intermediate regimes possible. We here discuss the calculation of the total power spectrum for the inflation, leading to a result that should cover all regimes ranging from cold to warm inflation. (author)
Cosmological constraints from thermal Sunyaev Zeldovich power spectrum revisited
Horowitz, Benjamin
2016-01-01
Thermal Sunyaev-Zeldovich (tSZ) power spectrum is one of the most sensitive methods to constrain cosmological parameters, scaling as the amplitude $\\sigma_8^8$. It is determined by the integral over the halo mass function multiplied by the total pressure content of clusters, and further convolved by the cluster gas pressure profile. It has been shown that various feedback effects can change significantly the pressure profile, strongly affecting the tSZ power spectrum at high $l$. Energetics arguments and SZ-halo mass scaling relations suggest feedback is unlikely to significantly change the total pressure content, making low $l$ tSZ power spectrum more robust against feedback effects. Furthermore, the separation between the cosmic infrared background (CIB) and tSZ is more reliable at low $l$. Low $l$ modes are however probing very small volumes, giving rise to very large non-gaussian sampling variance errors. By computing the trispectrum contribution we identify $90
Information content of the non-linear matter power spectrum
Rimes, C D
2005-01-01
We use an ensemble of N-body simulations of the currently favoured (concordance) cosmological model to measure the amount of information contained in the non-linear matter power spectrum, and its pre-whitened counterpart, about the amplitude of the initial power spectrum. Two surprising results emerge from this study: (i) that there is very little independent information in the power spectrum in the translinear regime (k ~ 0.2-0.8 Mpc/h at the present day) over and above the information at linear scales and (ii) that the cumulative information begins to rise sharply again with increasing wavenumber in the non-linear regime. In the fully non-linear regime, the simulations are consistent with no loss of information during translinear and non-linear evolution. If this is indeed the case then the results suggest a picture in which translinear collapse is very rapid, and is followed by a bounce prior to virialization, impelling a wholesale revision of the HKLM-PD formalism.
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.; Bond, J. R.; Brown, B.; Burger, B.; Chervenak, J.; Das, S.; Devlin, M. J.; Dicker, S. R.; Bertrand Doriese, W.; Dunner, R.; Essinger-Hileman, T.; Fisher, R. P.; Fowler, J. W.; Hajian, A.; Moseley, H.; Wollack, E.
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),
Price, Layne C.
2015-11-01
We consider a phenomenological model of inflation where the inflaton is the phase of a complex scalar field Φ . Planck-suppressed operators of O (f5/Mpl) modify the geometry of the vev ⟨Φ ⟩ at first order in the decay constant f , which adds a first-order periodic term to the definition of the canonically normalized inflaton ϕ . This correction to the inflaton induces a fixed number of extra oscillatory terms in the potential V ˜θp. We derive the same result in a toy scenario where the vacuum ⟨Φ ⟩ is an ellipse with an arbitrarily large eccentricity. These extra oscillations change the form of the power spectrum as a function of scale k and provide a possible mechanism for differentiating effective field theory motivated inflation from models where the angular shift symmetry is a gauge symmetry.
Rapid modelling of the redshift-space power spectrum multipoles for a masked density field
Wilson, M J; Taylor, A N; de la Torre, S
2015-01-01
In this work we reformulate the forward modelling of the redshift-space power spectrum multipole moments for a masked density field, as encountered in galaxy redshift surveys. Exploiting the symmetries of the redshift-space correlation function, we provide a `masked-field' generalisation of the Hankel transform relation between the multipole moments in real and Fourier space. Using this result, we detail how a likelihood analysis requiring computation for a broad range of desired $P(k)$ models may be executed $10^3-10^4$ times faster than with other common approaches, together with significant gains in spectral resolution. We present a concrete application to the complex angular geometry of the VIPERS PDR-1 release and discuss the validity of this technique for wide-angle surveys.
Power spectrum oscillations from Planck-suppressed operators in monodromy inflation
Price, Layne C
2015-01-01
We consider a phenomenological model of monodromy inflation where the inflaton is the phase of a complex scalar field $\\Phi$. Planck-suppressed operators of $\\mathcal O(f^5/M_\\mathrm{pl})$ modify the geometry of the vev $\\left \\langle \\Phi \\right \\rangle$ at first order in the decay constant $f$, which adds a first-order periodic term to the definition of the canonically normalized inflaton $\\phi$. This correction to the inflaton induces a fixed number of extra oscillatory terms in the monodromy potential $V \\sim \\theta^p$. We derive the same result in a toy scenario where the vacuum $\\left \\langle \\Phi \\right \\rangle$ is an ellipse with an arbitrarily large eccentricity. These extra oscillations change the form of the power spectrum as a function of scale $k$ and provide a possible mechanism for differentiating EFT-motivated monodromy inflation from models where the angular shift symmetry is a gauge symmetry.
We present a measurement of the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz. The measurement uses maps with 1.'4 angular resolution made with data from the Atacama Cosmology Telescope (ACT). The observations cover 228 deg2 of the southern sky, in a 4.02 wide strip centered on declination 530 south. The CMB at arcminute angular scales is particularly sensitive to the Silk damping scale, to the Sunyaev-Zel'dovich (SZ) effect from galaxy clusters, and to emission by radio sources and dusty galaxies. After masking the 108 brightest point sources in our maps, we estimate the power spectrum between 600 8 = 0.8. We constrain the model's amplitude ASZ 8, this implies σSZ8 < 0.86 (95% CL) given our SZ model. A fit of ACT and WMAP five-year data jointly to a six-parameter ΛCDM model plus point sources and the SZ effect is consistent with these results.
The optimization of spectrum in the power analyzer
Wu, R.C.; Chen, H.M. [I-Shou Univ., Kaohsiung, Taiwan (China). Dept. of Electrical Engineering; Ou, T.C. [National Sun Yat-Sen Univ., Kaohsiung, Taiwan (China). Dept. of Electrical Engineering; Tsai, J.I. [Kao Yuan Univ., Kaohsiung, Taiwan (China). Dept. of Electronic Engineering
2008-07-01
A study was conducted to investigate spectra under different sampling rates by amplitude summation and purpose V curve. The objective was to promote the accuracy of the spectrum in the power analyzer, which is influenced by different sampling rates. The study revealed that as soon as an optimal sampling rate is determined, an optimal spectrum can also be determined. Since the relationship between the amplitude summation and the sampling rate is that of a type V curve, the optimal solution can be obtained quickly. The study also compared results of Fast Fourier Transformation (FFT) and the optimal spectrum to prove the accuracy of this method. This method also offers a solution to common errors, including the picket-fence effect and leakage effect which result from the sampling period being different to the time of the signal period. By adjusting the sampling rate, the frequency scale can be changed to match the signal parameter. As such, the leakage effect can be eliminated and the exact parameter can be displayed on the spectrum. 10 refs., 3 tabs., 5 figs.
Galactic densities, substructure and the initial power spectrum
Although the currently favored cold dark matter plus cosmological constant model for structure formation assumes an n = 1 scale-invariant initial power spectrum, most inflation models produce at least mild deviations from n = 1. Because the lever arm from the CMB normalization to galaxy scales is long, even a small 'tilt' can have important implications for galactic observations. Here we calculate the COBS-normalized power spectra for several well-motivated models of inflation and compute implications for the substructure content and central densities of galaxy halos. Using an analytic model, normalized against N-body simulations, we show that while halos in the standard (n = 1) model are overdense by a factor of ∼ 6 compared to observations, several of our example inflation+LCDM models predict halo densities well within the range of observations, which prefer models with n ∼ 0.85. We go on to use a semi-analytic model (also normalized against N-body simulations) to follow the merger histories of galaxy-sized halos and track the orbital decay, disruption, and evolution of the merging substructure. Models with n ∼ 0.85 predict a factor of ∼ 3 fewer subhalos at a fixed circular velocity than the standard n 1 case. Although this level of reduction does not resolve the 'dwarf satellite problem', it does imply that the level of feedback required to match the observed number of dwarfs is sensitive to the initial power spectrum. Finally, the fraction of galaxy-halo mass that is bound up in substructure is consistent with limits imposed by multiply imaged quasars for all models considered: fsat > 0.01 even for an effective tilt of n ∼ 0.8. We conclude that, at their current level, lensing constraints of this kind do not provide an interesting probe of the primordial power spectrum
A Systematic Approach to Improve BOC Power Spectrum for GNSS
Rahul Gupta,
2015-06-01
Full Text Available An analysis of digital Phase-modulated signals is performed based on frequency spectrum which consists of a continuous and a number of discrete components at multiples of clock frequencies. The analysis shows that these components depend on the pulse shape function of multi-level digital signals to be phase modulated. In this paper, the effect of duty cycle, rise and fall times of these multi-level digital signals, on the frequency spectrum is studied. It is observed that the duty cycle variation of 10% results 30 dB increase in undesired component and the 10% increase in rise & fall times increase the power of undesired component by 12 dB. The theoretical observations of the effects are applied on the Binary Offset Carrier (BOC modulated signals as a case study, to discuss their effects in Global Navigation Satellite Systems (GNSS.
HI power spectrum of the spiral galaxy NGC628
Dutta, Prasun; Bharadwaj, Somnath; Chengalur, Jayaram N
2007-01-01
We have measured the HI power spectrum of the nearly face-on spiral galaxy NGC628 (M74) using a visibility based estimator. The power spectrum is well fitted by a power law $P(U)=AU^{\\alpha}$, with $\\alpha =- 1.6\\pm0.2$ over the length scale $800 {\\rm pc} {\\rm to} 8 {\\rm kpc}$. The slope is found to be independent of the width of the velocity channel. This value of the slope is a little more than one in excess of what has been seen at considerably smaller length scales in the Milky-Way, Small Magellanic Cloud (LMC), Large Magellanic Cloud (SMC) and the dwarf galaxy DDO210. We interpret this difference as indicating a transition from three dimensional turbulence at small scales to two dimensional turbulence in the plane of the galaxy's disk at length scales larger than galaxy's HI scale height. The slope measured here is similar to that found at large scales in the LMC. Our analysis also places an upper limit to the galaxy's scale height at $800\\ {\\rm pc}$ .
Using a nonparametric function estimation methodology, we present a comparative analysis of the Wilkinson Microwave Anisotropy Probe (WMAP) 1-, 3-, 5-, and 7-year data releases for the cosmic microwave background (CMB) angular power spectrum with respect to the following key questions. (1) How well is the power spectrum determined by the data alone? (2) How well is the ΛCDM model supported by a model-independent, data-driven analysis? (3) What are the realistic uncertainties on peak/dip locations and heights? Our results show that the height of the power spectrum is well determined by data alone for multipole l approximately less than 546 (1-year), 667 (3-year), 804 (5-year), and 842 (7-year data). We show that parametric fits based on the ΛCDM model are remarkably close to our nonparametric fits in l-regions where data are sufficiently precise. In contrast, the power spectrum for an HΛCDM model is progressively pushed away from our nonparametric fit as data quality improves with successive data realizations, suggesting incompatibility of this particular cosmological model with respect to the WMAP data sets. We present uncertainties on peak/dip locations and heights at the 95% (2σ) level of confidence and show how these uncertainties translate into hyperbolic 'bands' on the acoustic scale (lA ) and peak shift (φm) parameters. Based on the confidence set for the 7-year data, we argue that the low-l upturn in the CMB power spectrum cannot be ruled out at any confidence level in excess of about 10% (≈0.12σ). Additional outcomes of this work are a numerical formulation for minimization of a noise-weighted risk function subject to monotonicity constraints, a prescription for obtaining nonparametric fits that are closer to cosmological expectations on smoothness, and a method for sampling cosmologically meaningful power spectrum variations from the confidence set of a nonparametric fit.
Cole, S; Peacock, J A; Norberg, P; Baugh, C M; Frenk, C S; Baldry, I K; Bland-Hawthorn, J; Bridges, T; Cannon, R; Colless, M; Collins, C; Couch, W; Cross, N J G; Dalton, G B; Eke, V R; De Propris, R; Driver, S P; Efstathiou, G P; Ellis, Richard S; Glazebrook, K; Jackson, C; Jenkins, A; Lahav, O; Lewis, I; Lumsden, S; Maddox, S; Madgwick, D; Peterson, B A; Sutherland, W; Taylor, K
2005-01-01
We present a power spectrum analysis of the final 2dF Galaxy Redshift Survey, employing a direct Fourier method. The sample used comprises 221,414 galaxies with measured redshifts. We investigate in detail the modelling of the sample selection. A new angular mask is derived, based on revisions to the photometric calibration. The redshift selection function is determined by dividing the survey according to rest-frame colour, and deducing a self-consistent treatment of k-corrections and evolution for each population. The covariance matrix for the power-spectrum estimates is determined using two different approaches to the construction of mock surveys which are used to demonstrate that the input cosmological model can be correctly recovered. We are confident that the 2dFGRS power spectrum can be used to infer the matter content of the universe. On large scales, our estimated power spectrum shows evidence for the `baryon oscillations' that are predicted in CDM models. Fitting to a CDM model, assuming a primordial...
The angular power spectra of photometric Sloan Digital Sky Survey luminous red galaxies
Thomas, Shaun A.; Abdalla, Filipe B.; Lahav, Ofer
2011-04-01
We construct new galaxy angular power spectra Cℓ based on the extended, updated and final Sloan Digital Sky Survey (SDSS) II luminous red galaxy (LRG) photometric redshift survey - MegaZ (DR7). Encapsulating 7746 deg2 we utilize 723 556 photometrically determined LRGs between 0.45 preliminary parameter constraints of fb≡Ωb/Ωm= 0.173 ± 0.046 and Ωm= 0.260 ± 0.035 assuming H0= 75 km s-1 Mpc-1, ns= 1 and Ωk= 0. These limits are consistent with the cosmic microwave background and the previous data release (DR4). The Cℓ are sensitive to redshift space distortions and therefore we also recast our constraints into a measurement of β≈Ω0.55m/b in different redshift shells. The robustness of these power spectra with respect to a number of potential systematics such as extinction, photometric redshift and ANNz training set extrapolation are examined. The latter includes a cosmological comparison of available photometric redshift estimation codes where we find excellent agreement between template and empirical estimation methods. MegaZ DR7 represents a methodological prototype to next generation surveys such as the Dark Energy Survey and, furthermore, is a photometric precursor to the spectroscopic BOSS survey. Our galaxy catalogue and all power spectra data can be found at .
Power Spectrum Density of Stochastic Oscillating Accretion Disk
G. B. Long; J. W. Ou; Y. G. Zheng
2016-06-01
In this paper, we employ a stochastic oscillating accretiondisk model for the power spectral index and variability of BL Lac objectS5 0716+714. In the model, we assume that there is a relativistic oscillationof thin accretion disks and it interacts with an external thermal baththrough a friction force and a random force. We simulate the light curveand the power spectrum density (PSD) at (i) over-damped, (ii) criticallydamped and (iii) under-damped cases, respectively. Our results show thatthe simulated PSD curves depend on the intrinsic property of the accretiondisk, and it could be produced in a wide interval ranging from 0.94 to2.05 by changing the friction coefficient in a stochastic oscillating accretiondisk model. We argue that accretion disk stochastic oscillating couldbe a possible interpretation for observed PSD variability.
Power spectrum for the Bose-Einstein condensate dark matter
Velten, Hermano
2011-01-01
We assume that dark matter is composed of scalar particles that form a Bose-Einstein condensate (BEC) at some point during the cosmic evolution. Afterwards, cold dark matter is in the form of a condensate and behaves slightly different from the standard dark matter component. We study the large scale perturbative dynamics of the BEC dark matter in a model where this component coexists with baryonic matter and cosmological constant. The perturbative dynamics is studied using neo- Newtonian cosmology (where the pressure is dynamically relevant for the homogeneous and isotropic background) which is assumed to be correct for small values of the sound speed. We show that BEC dark matter effects can be seen in the matter power spectrum if the mass of the condensate particle lies in the range 15meV < m < 700meV leading to a small, but perceptible, excess of power at large scales.
Power spectrum for the Bose-Einstein condensate dark matter
Velten, Hermano, E-mail: velten@physik.uni-bielefeld.de [Departamento de Fisica, UFES, Vitoria, 29075-910 Espirito Santo (Brazil); Fakultaet fuer Physik, Universitaet Bielefeld, Postfach 100131, 33501 Bielefeld (Germany); Wamba, Etienne [Laboratory of Mechanics, Department of Physics, Faculty of Science, University of Yaounde I, P.O. Box 812, Yaounde (Cameroon)
2012-03-13
We assume that dark matter is composed of scalar particles that form a Bose-Einstein condensate (BEC) at some point during the cosmic evolution. Afterwards, cold dark matter is in the form of a condensate and behaves slightly different from the standard dark matter component. We study the large scale perturbative dynamics of the BEC dark matter in a model where this component coexists with baryonic matter and cosmological constant. The perturbative dynamics is studied using neo-Newtonian cosmology (where the pressure is dynamically relevant for the homogeneous and isotropic background) which is assumed to be correct for small values of the sound speed. We show that BEC dark matter effects can be seen in the matter power spectrum if the mass of the condensate particle lies in the range 15 MeV
Power spectrum for inflation models with quantum and thermal noises
We determine the power spectrum for inflation models covering all regimes from cold (isentropic) to warm (nonisentropic) inflation. We work in the context of the stochastic inflation approach, which can nicely describe both types of inflationary regimes concomitantly. A throughout analysis is carried out to determine the allowed parameter space for simple single field polynomial chaotic inflation models that is consistent with the most recent cosmological data from the nine-year Wilkinson Microwave Anisotropy Probe (WMAP) and in conjunction with other observational cosmological sources. We present the results for both the amplitude of the power spectrum, the spectral index and for the tensor to scalar curvature perturbation amplitude ratio. We briefly discuss cases when running is present. Despite single field polynomial-type inflaton potential models be strongly disfavored, or even be already ruled out in their simplest versions in the case of cold inflation, this is not the case for nonisentropic inflation models in general (warm inflation in particular), though higher order polynomial potentials (higher than quartic order) tend to become less favorable also in this case, presenting a much smaller region of parameter space compatible with the recent observational cosmological data
Cosmic Emulation: Fast Predictions for the Galaxy Power Spectrum
Kwan, Juliana; Habib, Salman; Padmanabhan, Nikhil; Finkel, Hal; Frontiere, Nick; Pope, Adrian
2013-01-01
The halo occupation distribution (HOD) approach has proven to be an effective method for modeling galaxy clustering and bias. In this approach, galaxies of a given type are probabilistically assigned to individual halos in N-body simulations. In this paper, we present a fast emulator for predicting the fully nonlinear galaxy power spectrum over a range of freely specifiable HOD modeling parameters. The emulator is constructed using results from 100 HOD models run on a large LCDM N-body simulation, with Gaussian Process interpolation applied to a PCA-based representation of the galaxy power spectrum. The total error is currently ~3% (~2% in the simulation and ~1% in the emulation process) from z=1 to z=0, over the considered parameter range. We use the emulator to investigate parametric dependencies in the HOD model, as well as the behavior of galaxy bias as a function of HOD parameters. The emulator is publicly available at http://www.hep.anl.gov/cosmology/CosmicEmu/emu.html.
Matter power spectrum and the challenge of percent accuracy
Schneider, Aurel; Potter, Doug; Stadel, Joachim; Onions, Julian; Reed, Darren S; Smith, Robert E; Springel, Volker; Pearce, Frazer R
2015-01-01
Future galaxy surveys require one percent precision in the theoretical knowledge of the power spectrum over a large range including very nonlinear scales. While this level of accuracy is easily obtained in the linear regime with perturbation theory, it represents a serious challenge for small scales where numerical simulations are required. In this paper we quantify the accuracy of present-day $N$-body methods, identifying main potential error sources from the set-up of initial conditions to the measurement of the final power spectrum. We directly compare three widely used $N$-body codes, Ramses, Pkdgrav3, and Gadget3 which represent three main discretisation techniques: the particle-mesh method, the tree method, and a hybrid combination of the two. For standard run parameters, the codes agree to within one percent at $k\\leq1$ $h\\,\\rm Mpc^{-1}$ and to within three percent at $k\\leq10$ $h\\,\\rm Mpc^{-1}$. In a second step, we quantify potential errors due to initial conditions, box size, and resolution using an...
Unbiased contaminant removal for 3D galaxy power spectrum measurements
Kalus, B.; Percival, W. J.; Bacon, D. J.; Samushia, L.
2016-08-01
We assess and develop techniques to remove contaminants when calculating the 3D galaxy power spectrum. We separate the process into three separate stages: (i) removing the contaminant signal, (ii) estimating the uncontaminated cosmological power spectrum, (iii) debiasing the resulting estimates. For (i), we show that removing the best-fit contaminant (mode subtraction), and setting the contaminated components of the covariance to be infinite (mode deprojection) are mathematically equivalent. For (ii), performing a Quadratic Maximum Likelihood (QML) estimate after mode deprojection gives an optimal unbiased solution, although it requires the manipulation of large N_mode^2 matrices (Nmode being the total number of modes), which is unfeasible for recent 3D galaxy surveys. Measuring a binned average of the modes for (ii) as proposed by Feldman, Kaiser & Peacock (1994, FKP) is faster and simpler, but is sub-optimal and gives rise to a biased solution. We present a method to debias the resulting FKP measurements that does not require any large matrix calculations. We argue that the sub-optimality of the FKP estimator compared with the QML estimator, caused by contaminants is less severe than that commonly ignored due to the survey window.
First Results from COPSS: The CO Power Spectrum Survey
Keating, Garrett K; Marrone, Daniel P; DeBoer, David R; Heiles, Carl; Chang, Tzu-Ching; Carlstrom, John E; Greer, Christopher H; Hawkins, David; Lamb, James W; Leitch, Erik; Miller, Amber D; Muchovej, Stephen; Woody, David P
2015-01-01
We present constraints on the abundance of carbon-monoxide in the early Universe from the CO Power Spectrum Survey (COPSS). We utilize a data set collected between 2005 and 2008 using the Sunyaev-Zel'dovich Array (SZA), which were previously used to measure arcminute-scale fluctuations of the CMB. This data set features observations of 44 fields, covering an effective area of 1.7 square degrees, over a frequency range of 27 to 35 GHz. Using the technique of intensity mapping, we are able to probe the CO(1-0) transition, with sensitivity to spatial modes between $k=0.5{-}2\\ h\\,\\textrm{Mpc}^{-1}$ over a range in redshift of $z=2.3{-}3.3$, spanning a comoving volume of $3.6\\times10^{6}\\ h^{-3}\\,\\textrm{Mpc}^{3}$. We demonstrate our ability to mitigate foregrounds, and present estimates of the impact of continuum sources on our measurement. We constrain the CO power spectrum to $P_{\\textrm{CO}}<2.6\\times10^{4}\\ \\mu\\textrm{K}^{2} (h^{-1}\\,\\textrm{Mpc})^{3}$, or $\\Delta^{2}_{\\textrm{CO}}(k\\! = \\! 1 \\ h\\,\\textrm{...
Power Spectrum and Non-Gaussianities in Anisotropic Inflation
Dey, Anindya; Paban, Sonia
2014-01-01
We study the planar regime of curvature perturbations for single field inflationary models in an axially symmetric Bianchi I background. In a theory with standard scalar field action, the power spectrum for such modes has a pole as the planarity parameter goes to zero. We show that constraints from back reaction lead to a strong lower bound on the planarity parameter for high-momentum planar modes and use this bound to calculate the signal-to-noise ratio of the anisotropic power spectrum in the CMB, which in turn places an upper bound on the Hubble scale during inflation allowed in our model. We find that non-Gaussianities for these planar modes are enhanced for the flattened triangle and the squeezed triangle configurations, but show that the estimated values of the f_NL parameters remain well below the experimental bounds from the CMB for generic planar modes (other, more promising signatures are also discussed). For a standard action, f_NL from the squeezed configuration turns out to be larger compared to ...
Power Spectrum Analysis of Polarized Emission from the Canadian Galactic Plane Survey
Stutz, R. A.; Rosolowsky, E. W.; Kothes, R.; Landecker, T. L.
2014-05-01
Angular power spectra are calculated and presented for the entirety of the Canadian Galactic Plane Survey polarization data set at 1.4 GHz covering an area of 1060 deg2. The data analyzed are a combination of data from the 100 m Effelsberg Telescope, the 26 m Telescope at the Dominion Radio Astrophysical Observatory, and the Synthesis Telescope at the Dominion Radio Astrophysical Observatory, allowing all scales to be sampled down to arcminute resolution. The resulting power spectra cover multipoles from l ≈ 60 to l ≈ 104 and display both a power-law component at low multipoles and a flattening at high multipoles from point sources. We fit the power spectrum with a model that accounts for these components and instrumental effects. The resulting power-law indices are found to have a mode of 2.3, similar to previous results. However, there are significant regional variations in the index, defying attempts to characterize the emission with a single value. The power-law index is found to increase away from the Galactic plane. A transition from small-scale to large-scale structure is evident at b = 9°, associated with the disk-halo transition in a 15° region around l = 108°. Localized variations in the index are found toward H II regions and supernova remnants, but the interpretation of these variations is inconclusive. The power in the polarized emission is anticorrelated with bright thermal emission (traced by Hα emission) indicating that the thermal emission depolarizes background synchrotron emission.
Power Allocation for Balancing Spectrum Efficiency and Power Consumption in Cognitive Relay Networks
Lun Tang
2011-10-01
Full Text Available In order to guarantee the QoS requirement of secondary users and not to affect the outage probability of primary user in cognitive relay networks, we propose two optimal power allocation models: (1 maximizing the transmission rate of secondary users; (2 minimizing the total power consumption. Theory analysis shows that two optimal power allocation models conflict between spectrum efficiency and power consumption. Furthermore, an optimal power allocation model which joints the transmission rate and the total power consumption in cognitive relay networks is proposed. By using the Lagrangian method, the optimization algorithm for this model is designed. The proposed algorithm can achieve the trade-off between the transmission rate and the total power consumption by varying the weight. Simulation results show that the proposed algorithm can effectively adjust the transmission rate and the total power consumption of secondary users.
Jabir, M. V.; Apurv Chaitanya, N.; Aadhi, A.; Samanta, G. K.
2016-01-01
The “perfect” vortex is a new class of optical vortex beam having ring radius independent of its topological charge (order). One of the simplest techniques to generate such beams is the Fourier transformation of the Bessel-Gauss beams. The variation in ring radius of such vortices require Fourier lenses of different focal lengths and or complicated imaging setup. Here we report a novel experimental scheme to generate perfect vortex of any ring radius using a convex lens and an axicon. As a proof of principle, using a lens of focal length f = 200 mm, we have varied the radius of the vortex beam across 0.3–1.18 mm simply by adjusting the separation between the lens and axicon. This is also a simple scheme to measure the apex angle of an axicon with ease. Using such vortices we have studied non-collinear interaction of photons having orbital angular momentum (OAM) in spontaneous parametric down-conversion (SPDC) process and observed that the angular spectrum of the SPDC photons are independent of OAM of the pump photons rather depends on spatial profile of the pump beam. In the presence of spatial walk-off effect in nonlinear crystals, the SPDC photons have asymmetric angular spectrum with reducing asymmetry at increasing vortex radius. PMID:26912184
Jabir, M. V.; Apurv Chaitanya, N.; Aadhi, A.; Samanta, G. K.
2016-02-01
The “perfect” vortex is a new class of optical vortex beam having ring radius independent of its topological charge (order). One of the simplest techniques to generate such beams is the Fourier transformation of the Bessel-Gauss beams. The variation in ring radius of such vortices require Fourier lenses of different focal lengths and or complicated imaging setup. Here we report a novel experimental scheme to generate perfect vortex of any ring radius using a convex lens and an axicon. As a proof of principle, using a lens of focal length f = 200 mm, we have varied the radius of the vortex beam across 0.3-1.18 mm simply by adjusting the separation between the lens and axicon. This is also a simple scheme to measure the apex angle of an axicon with ease. Using such vortices we have studied non-collinear interaction of photons having orbital angular momentum (OAM) in spontaneous parametric down-conversion (SPDC) process and observed that the angular spectrum of the SPDC photons are independent of OAM of the pump photons rather depends on spatial profile of the pump beam. In the presence of spatial walk-off effect in nonlinear crystals, the SPDC photons have asymmetric angular spectrum with reducing asymmetry at increasing vortex radius.
THE ATACAMA COSMOLOGY TELESCOPE: COSMOLOGICAL PARAMETERS FROM THE 2008 POWER SPECTRUM
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 deg2 with the Atacama Cosmology Telescope (ACT) during its 2008 season. ACT measures fluctuations at scales 500 3000 = 6.8 ± 2.9 μK2, where Bl≡l(l + 1)Cl/2π. The IR Poisson power at 148 GHz is B3000 = 7.8 ± 0.7 μK2 (Cl = 5.5 ± 0.5 nK2), and a clustered IR component is required with B3000 = 4.6 ± 0.9 μK2, assuming an analytic model for its power spectrum shape. At 218 GHz only about 15% of the power, approximately 27 μK2, is CMB anisotropy at l = 3000. The remaining 85% is attributed to IR sources (approximately 50% Poisson and 35% clustered), with spectral index α = 3.69 ± 0.14 for flux scaling as S(ν)∝να. We estimate primary cosmological parameters from the less contaminated 148 GHz spectrum, marginalizing over SZ and source power. The ΛCDM cosmological model is a good fit to the data (χ2/dof = 29/46), and ΛCDM parameters estimated from ACT+Wilkinson Microwave Anisotropy Probe (WMAP) are consistent with the seven-year WMAP limits, with scale invariant ns = 1 excluded at 99.7% confidence level (CL) (3σ). A model with no CMB lensing is disfavored at 2.8σ. 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 6σ detection of primordial helium, with YP = 0.313 ± 0.044, and a 4σ detection of relativistic species, assumed to be neutrinos, with Neff = 5.3 ± 1.3 (4.6 ± 0.8 with BAO+H0 data). From the CMB alone the running of the spectral index is constrained to be dns /dln k = -0.034 ± 0.018, the limit on the tensor-to-scalar ratio is r -7 (95% CL).
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.; Bond, J. R.; Brown, B.; Burger, B.; Chervenak, J.; Das, S.; Devlin, M. J.; Dicker, S. R.; Bertrand Doriese, W.; Dunner, R.; Essinger-Hileman, T.; Fisher, R. P.; Fowler, J. W.; Hajian, A.; Moseley, H.; Wollack, E.
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 < l < 10,000. We fit a model for the lensed CMB, Sunyaev-Zel'dovich (SZ), and foreground contribution to the 148 GHz and 218 GHz power spectra, including thermal and kinetic SZ, Poisson power from radio and infrared point sources, and clustered power from infrared point sources. At l = 3000, about half the power at 148 GHz comes from primary CMB after masking bright radio sources. The power from thermal and kinetic SZ is estimated to be Beta(sub 3000) is identical to 6.8 +/- 2.9 mu K (exp 2), where Beta (sub l) is identical to l(l + 1) C(sub l)/2pi. The IR Poisson power at 148 GHz is Bewta(sub 3000) 7.8 +/- 0.7 muK(exp 2) (C(sub l) = 5.5 +/- 0.5 nK(exp 2)), and a clustered IR component is required with Beta (sub 3000) = 4.6 +/- 0.9 muK(exp 2), assuming an analytic model for its power spectrum shape. At 218 GHz only about 15% of the power, approximately 27 mu K(exp 2), is CMB anisotropy at l = 3000. The remaining 85% is attributed to IR sources (approximately 50% Poisson and 35% clustered), with spectral index alpha = 3.69 +/- 0.14 for flux scaling as S(nu) varies as nu(sup alpha). We estimate primary 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
Fowler, J. W.; Acquaviva, V.; Ade, P. A. R.; Aguirre, P.; Amiri, M.; Appel, J. W.; Barrientos, L. F.; Bassistelli, E. S.; Bond, J. R.; Brown, B.; Burger, B.; Chervenak, J.; Das, S.; Devlin, M. J.; Dicker, S. R.; Doriese, W. B.; Dunkley, J.; Duenner, R.; Essinger-Hileman, T.; Fisher, R. P.; Hajian, A.; Halpern, M.; Hasselfield, M.; Moseley, H.; Wollack, Ed
2010-01-01
We present a measurement of the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz. The measurement uses maps with 1.4' angular resolution made with data from the Atacama Cosmology Telescope (ACT). The observations cover 228 deg(sup 2) of the southern sky, in a 4 deg. 2-wide strip centered on declination 53 deg. South. The CMB at arc minute angular scales is particularly sensitive to the Silk damping scale, to the Sunyaev-Zel'dovich (SZ) effect from galaxy dusters, and to emission by radio sources and dusty galaxies. After masking the 108 brightest point sources in our maps, we estimate the power spectrum between 600 less than l less than 8000 using the adaptive multi-taper method to minimize spectral leakage and maximize use of the full data set. Our absolute calibration is based on observations of Uranus. To verify the calibration and test the fidelity of our map at large angular scales, we cross-correlate the ACT map to the WMAP map and recover the WMAP power spectrum from 250 less than l less than 1150. The power beyond the Silk damping tail of the CMB (l approximately 5000) is consistent with models of the emission from point sources. We quantify the contribution of SZ clusters to the power spectrum by fitting to a model normalized to sigma 8 = 0.8. We constrain the model's amplitude A(sub sz) less than 1.63 (95% CL). If interpreted as a measurement of as, this implies sigma (sup SZ) (sub 8) less than 0.86 (95% CL) given our SZ model. A fit of ACT and WMAP five-year data jointly to a 6-parameter ACDM model plus point sources and the SZ effect is consistent with these results.
Constraining the intracluster pressure profile from the thermal SZ power spectrum
Ramos-Ceja, M. E.; Basu, K.; Pacaud, F.; Bertoldi, F.
2015-11-01
The angular power spectrum of the thermal Sunyaev-Zel'dovich (tSZ) effect is highly sensitive to cosmological parameters such as σ8 and Ωm, but its use as a precision cosmological probe is hindered by the astrophysical uncertainties in modeling the gas pressure profile in galaxy groups and clusters. In this paper we assume that the relevant cosmological parameters are accurately known and explore the ability of current and future tSZ power spectrum measurements to constrain the intracluster gas pressure or the evolution of the gas mass fraction, fgas. We use the CMB bandpower measurements from the South Pole Telescope and a Bayesian Markov chain Monte Carlo (MCMC) method to quantify deviations from the standard, universal gas pressure model. We explore analytical model extensions that bring the predictions for the tSZ power into agreement with experimental data. We find that a steeper pressure profile in the cluster outskirts or an evolving fgas have mild-to-severe conflicts with experimental data or simulations. Varying more than one parameter in the pressure model leads to strong degeneracies that cannot be broken with current observational constraints. We use simulated bandpowers from future tSZ survey experiments, in particular a possible 2000 deg2 CCAT survey, to show that future observations can provide almost an order of magnitude better precision on the same model parameters. This will allow us to break the current parameter degeneracies and place simultaneous constraints on the gas pressure profile and its redshift evolution, for example.
Araujo, D.; Dumoulin, R. N.; Newburgh, L. B.; Zwart, J. T. L. [Department of Physics and Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Bischoff, C.; Brizius, A.; Buder, I.; Kusaka, A. [Kavli Institute for Cosmological Physics, Department of Physics, Enrico Fermi Institute, The University of Chicago, Chicago, IL 60637 (United States); Chinone, Y. [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Cleary, K.; Reeves, R. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, 1200 E. California Blvd M/C 249-17, Pasadena, CA 91125 (United States); Monsalve, R.; Bustos, R. [Department of Physics, University of Miami, 1320 Campo Sano Drive, Coral Gables, FL 33146 (United States); Naess, S. K.; Eriksen, H. K. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo (Norway); Wehus, I. K. [Department of Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH (United Kingdom); Bronfman, L. [Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago (Chile); Church, S. E. [Kavli Institute for Particle Astrophysics and Cosmology and Department of Physics, Stanford University, Varian Physics Building, 382 Via Pueblo Mall, Stanford, CA 94305 (United States); Dickinson, C. [Jodrell Bank Centre for Astrophysics, Alan Turing Building, School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Gaier, T., E-mail: ibuder@uchicago.edu [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Collaboration: QUIET Collaboration; and others
2012-12-01
The Q/U Imaging ExperimenT (QUIET) has observed the cosmic microwave background (CMB) at 43 and 95 GHz. The 43 GHz results have been published in a previous paper, and here we report the measurement of CMB polarization power spectra using the 95 GHz data. This data set comprises 5337 hr of observations recorded by an array of 84 polarized coherent receivers with a total array sensitivity of 87 {mu}K{radical}s. Four low-foreground fields were observed, covering a total of {approx}1000 deg{sup 2} with an effective angular resolution of 12.'8, allowing for constraints on primordial gravitational waves and high signal-to-noise measurements of the E-modes across three acoustic peaks. The data reduction was performed using two independent analysis pipelines, one based on a pseudo-C {sub l} (PCL) cross-correlation approach, and the other on a maximum-likelihood (ML) approach. All data selection criteria and filters were modified until a predefined set of null tests had been satisfied before inspecting any non-null power spectrum. The results derived by the two pipelines are in good agreement. We characterize the EE, EB, and BB power spectra between l = 25 and 975 and find that the EE spectrum is consistent with {Lambda}CDM, while the BB power spectrum is consistent with zero. Based on these measurements, we constrain the tensor-to-scalar ratio to r = 1.1{sup +0.9} {sub -0.8} (r < 2.8 at 95% C.L.) as derived by the ML pipeline, and r = 1.2{sup +0.9} {sub -0.8} (r < 2.7 at 95% C.L.) as derived by the PCL pipeline. In one of the fields, we find a correlation with the dust component of the Planck Sky Model, though the corresponding excess power is small compared to statistical errors. Finally, we derive limits on all known systematic errors, and demonstrate that these correspond to a tensor-to-scalar ratio smaller than r = 0.01, the lowest level yet reported in the literature.
The Q/U Imaging ExperimenT (QUIET) has observed the cosmic microwave background (CMB) at 43 and 95 GHz. The 43 GHz results have been published in a previous paper, and here we report the measurement of CMB polarization power spectra using the 95 GHz data. This data set comprises 5337 hr of observations recorded by an array of 84 polarized coherent receivers with a total array sensitivity of 87 μK√s. Four low-foreground fields were observed, covering a total of ∼1000 deg2 with an effective angular resolution of 12.'8, allowing for constraints on primordial gravitational waves and high signal-to-noise measurements of the E-modes across three acoustic peaks. The data reduction was performed using two independent analysis pipelines, one based on a pseudo-C l (PCL) cross-correlation approach, and the other on a maximum-likelihood (ML) approach. All data selection criteria and filters were modified until a predefined set of null tests had been satisfied before inspecting any non-null power spectrum. The results derived by the two pipelines are in good agreement. We characterize the EE, EB, and BB power spectra between l = 25 and 975 and find that the EE spectrum is consistent with ΛCDM, while the BB power spectrum is consistent with zero. Based on these measurements, we constrain the tensor-to-scalar ratio to r = 1.1+0.9–0.8 (r +0.9–0.8 (r < 2.7 at 95% C.L.) as derived by the PCL pipeline. In one of the fields, we find a correlation with the dust component of the Planck Sky Model, though the corresponding excess power is small compared to statistical errors. Finally, we derive limits on all known systematic errors, and demonstrate that these correspond to a tensor-to-scalar ratio smaller than r = 0.01, the lowest level yet reported in the literature.
Shrinkage Estimation of the Power Spectrum Covariance Matrix
Pope, Adrian C
2007-01-01
We introduce a novel statistical technique, shrinkage estimation, to estimate the power spectrum covariance matrix from a limited number of simulations. We optimally combine an empirical estimate of the covariance with a model (the target) to minimize the total mean squared error compared to the true underlying covariance. We test our technique on N-body simulations and evaluate its performance by estimating cosmological parameters. Using a simple diagonal target, we show that the shrinkage estimator significantly outperforms both the empirical covariance and the target individually when using a small number of simulations. We find that reducing noise in the covariance estimate is essential for properly estimating the values of cosmological parameters as well as their confidence intervals. We extend our method to the jackknife covariance estimator and again find significant improvement, though simulations give better results. Even for thousands of simulations we still find evidence that our method improves es...
Contribution of domain wall networks to the CMB power spectrum
Lazanu, A., E-mail: A.Lazanu@damtp.cam.ac.uk [Centre for Theoretical Cosmology, Department of Applied Mathematics and Theoretical Physics, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Martins, C.J.A.P., E-mail: Carlos.Martins@astro.up.pt [Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Instituto de Astrofísica e Ciências do Espaço, CAUP, Rua das Estrelas, 4150-762 Porto (Portugal); Shellard, E.P.S., E-mail: E.P.S.Shellard@damtp.cam.ac.uk [Centre for Theoretical Cosmology, Department of Applied Mathematics and Theoretical Physics, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)
2015-07-30
We use three domain wall simulations from the radiation era to the late-time dark energy domination era based on the PRS algorithm to calculate the energy–momentum tensor components of domain wall networks in an expanding universe. Unequal time correlators in the radiation, matter and cosmological constant epochs are calculated using the scaling regime of each of the simulations. The CMB power spectrum of a network of domain walls is determined. The first ever quantitative constraint for the domain wall surface tension is obtained using a Markov chain Monte Carlo method; an energy scale of domain walls of 0.93 MeV, which is close but below the Zel'dovich bound, is determined.
Contribution of domain wall networks to the CMB power spectrum
A. Lazanu
2015-07-01
Full Text Available We use three domain wall simulations from the radiation era to the late-time dark energy domination era based on the PRS algorithm to calculate the energy–momentum tensor components of domain wall networks in an expanding universe. Unequal time correlators in the radiation, matter and cosmological constant epochs are calculated using the scaling regime of each of the simulations. The CMB power spectrum of a network of domain walls is determined. The first ever quantitative constraint for the domain wall surface tension is obtained using a Markov chain Monte Carlo method; an energy scale of domain walls of 0.93 MeV, which is close but below the Zel'dovich bound, is determined.
On Removing Interloper Contamination from Intensity Mapping Power Spectrum Measurements
Lidz, Adam; Taylor, Jessie
2016-07-01
Line intensity mapping experiments seek to trace large-scale structures by measuring the spatial fluctuations in the combined emission, in some convenient spectral line, from individually unresolved galaxies. An important systematic concern for these surveys is line confusion from foreground or background galaxies emitting in other lines that happen to lie at the same observed frequency as the “target” emission line of interest. We develop an approach to separate this “interloper” emission at the power spectrum level. If one adopts the redshift of the target emission line in mapping from observed frequency and angle on the sky to co-moving units, the interloper emission is mapped to the wrong co-moving coordinates. Because the mapping is different in the line of sight and transverse directions, the interloper contribution to the power spectrum becomes anisotropic, especially if the interloper and target emission are at widely separated redshifts. This distortion is analogous to the Alcock–Paczynski test, but here the warping arises from assuming the wrong redshift rather than an incorrect cosmological model. We apply this to the case of a hypothetical [C ii] emission survey at z∼ 7 and find that the distinctive interloper anisotropy can, in principle, be used to separate strong foreground CO emission fluctuations. In our models, however, a significantly more sensitive instrument than currently planned is required, although there are large uncertainties in forecasting the high-redshift [C ii] emission signal. With upcoming surveys, it may nevertheless be useful to apply this approach after first masking pixels suspected of containing strong interloper contamination.
Krasina, E.A.; Nevezhin, O.A.; Rubanovich, I.M.
1976-01-01
The example of a solar thermoemission power plant is used for the analysis of certain features of solar-power-plant operating regimes for various radiation densities and angular sizes of the radiation source. The calculations are performed both on the assumption of exact pointing of the collector optical axis at the radiation source and with allowance for error. Results are reported for plant-efficiency optimization calculations, together with data on the permissible error angles of the solar tracking system.
Morioka, Y.; Tomiyama, K.; Arima, H. (Kansai Electric Power Co., Inc., Osaka (Japan)); Sawai, K.; Omata, K.; Matsushima, T.; Takagi, K.; Ishibashi, A.; Saito, H. (Toshiba Corp., Tokyo (Japan))
1993-07-01
The purpose of this newly developed equipment is to separate the power system when an out-of-step between two groups of generators within it is predicted. The out-of-step prediction method is based on the generator's angular-velocity data measured by electromagnetic sensors and gears that are fastened directly to the rotors. The equipment was tested by the large-scale power system simulator APSA (Advanced Power System Analyzer), that is installed in the Kansai Electric Power Co., Inc. The equipment also underwent a field test.
Unscreening modified gravity in the matter power spectrum
Lombriser, Lucas; Mead, Alexander
2015-01-01
Viable modifications of gravity that may produce cosmic acceleration need to be screened in high-density regions such as the Solar System, where general relativity is well tested. Screening mechanisms also prevent strong anomalies in the large-scale structure and limit the constraints that can be inferred on these gravity models from cosmology. We find that by suppressing the contribution of the screened high-density regions in the matter power spectrum, allowing a greater contribution of unscreened low densities, modified gravity models can be more readily discriminated from the concordance cosmology. Moreover, by variation of density thresholds, degeneracies with other effects may be dealt with more adequately. Specializing to chameleon gravity as a worked example for screening in modified gravity, employing N-body simulations of f(R) models and the halo model of chameleon theories, we demonstrate the effectiveness of this method. We find that a percent-level measurement of the clipped power at k < 0.3 h...
We propose a high-precision method for measuring the orbital angular momentum (OAM) spectrum of ultra-broadband optical-vortex (OV) pulses from fork-like interferograms between OV pulses and a reference plane-wave pulse. It is based on spatial reconstruction of the electric fields of the pulses to be measured from the frequency-resolved interference pattern. Our method is demonstrated experimentally by obtaining the OAM spectra for different spectral components of the OV pulses, enabling us to characterize the frequency dispersion of the topological charge of the OAM spectrum by a simple experimental setup. Retrieval is carried out in quasi-real time, allowing us to investigate OAM spectra dynamically. Furthermore, we determine the relative phases (including the sign) of the topological-charge-resolved electric-field amplitudes, which are significant for evaluating OVs or OV pulses with arbitrarily superposed modes. (paper)
Ade, P A R; Anthony, A E; Arnold, K; Atlas, M; Barron, D; Boettger, D; Borrill, J; Chapman, S; Chinone, Y; Dobbs, M; Elleflot, T; Errard, J; Fabbian, G; Feng, C; Flanigan, D; Gilbert, A; Grainger, W; Halverson, N W; Hasegawa, M; Hattori, K; Hazumi, M; Holzapfel, W L; Hori, Y; Howard, J; Hyland, P; Inoue, Y; Jaehnig, G C; Jaffe, A H; Keating, B; Kermish, Z; Keskitalo, R; Kisner, T; Jeune, M Le; Lee, A T; Leitch, E M; Linder, E; Lungu, M; Matsuda, F; Matsumura, T; Meng, X; Miller, N J; Morii, H; Moyerman, S; Myers, M J; Navaroli, M; Nishino, H; Paar, H; Peloton, J; Poletti, D; Quealy, E; Rebeiz, G; Reichardt, C L; Richards, P L; Ross, C; Schanning, I; Schenck, D E; Sherwin, B D; Shimizu, A; Shimmin, C; Shimon, M; Siritanasak, P; Smecher, G; Spieler, H; Stebor, N; Steinbach, B; Stompor, R; Suzuki, A; Takakura, S; Tomaru, T; Wilson, B; Yadav, A; Zahn, O
2014-01-01
We report a measurement of the B-mode polarization power spectrum in the cosmic microwave background (CMB) using the POLARBEAR experiment in Chile. The faint B-mode polarization signature carries information about the Universe's entire history of gravitational structure formation, and the cosmic inflation that may have occurred in the very early Universe. Our measurement covers the angular multipole range 500 < l < 2100 and is based on observations of 30 square degrees with 3.5 arcmin resolution at 150 GHz. On these angular scales, gravitational lensing of the CMB by intervening structure in the Universe is expected to be the dominant source of B-mode polarization. Including both systematic and statistical uncertainties, the hypothesis of no B-mode polarization power from gravitational lensing is rejected at 97.5% confidence. The band powers are consistent with the standard cosmological model. Fitting a single lensing amplitude parameter A_BB to the measured band powers, A_BB = 1.12 +/- 0.61 (stat) +0.0...
Infrared divergence of pure Einstein gravity contributions to cosmological density power spectrum
Noh, Hyerim; Jeong, Donghui; Hwang, Jai-chan
2009-01-01
We probe the pure Einstein's gravity contributions to the second-order density power spectrum. In the small-scale, we discover that the Einstein's gravity contribution is negligibly small. This guarantees that Newton's gravity is sufficient to handle the baryon acoustic oscillation scale. In the large scale, however, we discover that the Einstein's gravity contribution to the second-order power spectrum dominates the linear-order power spectrum. Thus, pure Einstein gravity contribution appear...
Noh, Hyerim; Jeong, Donghui; Hwang, Jai-Chan
2009-07-10
We probe the pure Einstein gravity contributions to the second-order density power spectrum. On the small scale, we discover that Einstein's gravity contribution is negligibly small. This guarantees that Newton's gravity is currently sufficient to handle the baryon acoustic oscillation scale. On the large scale, however, we discover that Einstein's gavity contribution to the second-order power spectrum dominates the linear-order power spectrum. Thus, the pure Einstein gravity contribution appearing in the third-order perturbation leads to an infrared divergence in the power spectrum. PMID:19659195
Perturbative approach to covariance matrix of the matter power spectrum
Mohammed, Irshad; Vlah, Zvonimir
2016-01-01
We evaluate the covariance matrix of the matter power spectrum using perturbation theory up to dominant terms at 1-loop order and compare it to numerical simulations. We decompose the covariance matrix into the disconnected (Gaussian) part, trispectrum from the modes outside the survey (beat coupling or super-sample variance), and trispectrum from the modes inside the survey, and show how the different components contribute to the overall covariance matrix. We find the agreement with the simulations is at a 10\\% level up to $k \\sim 1 h {\\rm Mpc^{-1}}$. We show that all the connected components are dominated by the large-scale modes ($k<0.1 h {\\rm Mpc^{-1}}$), regardless of the value of the wavevectors $k,\\, k'$ of the covariance matrix, suggesting that one must be careful in applying the jackknife or bootstrap methods to the covariance matrix. We perform an eigenmode decomposition of the connected part of the covariance matrix, showing that at higher $k$ it is dominated by a single eigenmode. The full cova...
Noise power spectrum measurements under nonuniform gains and their compensations
Kim, Dong Sik; Kim, Eun; Shin, Choul Woo
2016-03-01
The fixed pattern noise, which is due to the nonuniform amplifier gains and scintillator sensitivities, should be alleviated in radiography imaging and should have less influence on measuring the noise power spectrum (NPS) of the radiography detector. In order to reduce the influence, background trend removing methods, which are based on low-pass filtering, polynomial fitting, and subtracting the average image of the uniform exposure images, are traditionally employed in the literature. In terms of removing the fixed pattern noise, the subtraction method shows a good performance. However, the number of images to be averaged is practically finite and thus the noise contained in the average image contaminates the image difference and inflates the NPS curve. In this paper, an image formation model considering the nonuniform gain is constructed and two measuring methods, which are based on the subtraction and gain correction, respectively, are considered. In order to accurately measure a normalized NPS (NNPS) in the measuring methods, the number of images to be averaged is considered for NNPS compensations. For several flat-panel radiography detectors, the NNPS measurements are conducted and compared with conventional approaches, which have no compensation stages. Through experiments it is shown that the compensation can provide accurate NNPS measurements less influenced by the fixed pattern noise.
Testing for New Physics: Neutrinos and the Primordial Power Spectrum
Canac, Nicolas; Abazajian, Kevork N; Easther, Richard; Price, Layne C
2016-01-01
We test the sensitivity of neutrino parameter constraints from combinations of CMB and LSS data sets to the assumed form of the primordial power spectrum (PPS) using Bayesian model selection. Significantly, none of the tested combinations, including recent high-precision local measurements of $\\mathrm{H}_0$ and cluster abundances, indicate a signal for massive neutrinos or extra relativistic degrees of freedom. For PPS models with a large, but fixed number of degrees of freedom, neutrino parameter constraints do not change significantly if the location of any features in the PPS are allowed to vary, although neutrino constraints are more sensitive to PPS features if they are known a priori to exist at fixed intervals in $\\log k$. Although there is no support for a non-standard neutrino sector from constraints on both neutrino mass and relativistic energy density, we see surprisingly strong evidence for features in the PPS when it is constrained with data from Planck 2015, SZ cluster counts, and recent high-pr...
Battaglia, N. [Department of Astronomy and Astrophysics, University of Toronto, 50 St George, Toronto, ON M5S 3H4 (Canada); Bond, J. R.; Pfrommer, C.; Sievers, J. L. [Canadian Institute for Theoretical Astrophysics, 60 St George, Toronto, ON M5S 3H8 (Canada)
2012-10-20
Secondary anisotropies in the cosmic microwave background are a treasure-trove of cosmological information. Interpreting current experiments probing them are limited by theoretical uncertainties rather than by measurement errors. Here we focus on the secondary anisotropies resulting from the thermal Sunyaev-Zel'dovich (tSZ) effect; the amplitude of which depends critically on the average thermal pressure profile of galaxy groups and clusters. To this end, we use a suite of hydrodynamical TreePM-SPH simulations that include radiative cooling, star formation, supernova feedback, and energetic feedback from active galactic nuclei. We examine in detail how the pressure profile depends on cluster radius, mass, and redshift and provide an empirical fitting function. We employ three different approaches for calculating the tSZ power spectrum: an analytical approach that uses our pressure profile fit, a semianalytical method of pasting our pressure fit onto simulated clusters, and a direct numerical integration of our simulated volumes. We demonstrate that the detailed structure of the intracluster medium and cosmic web affect the tSZ power spectrum. In particular, the substructure and asphericity of clusters increase the tSZ power spectrum by 10%-20% at l {approx} 2000-8000, with most of the additional power being contributed by substructures. The contributions to the power spectrum from radii larger than R {sub 500} is {approx}20% at l = 3000, thus clusters interiors (r < R {sub 500}) dominate the power spectrum amplitude at these angular scales.
On minimally parametric primordial power spectrum reconstruction and the evidence for a red tilt
The latest cosmological data seem to indicate a significant deviation from scale invariance of the primordial power spectrum when parameterized either by a power law or by a spectral index with non-zero 'running'. This deviation, by itself, serves as a powerful tool for discriminating among theories for the origin of cosmological structures such as inflationary models. Here, we use a minimally parametric smoothing spline technique to reconstruct the shape of the primordial power spectrum. This technique is well suited to searching for smooth features in the primordial power spectrum such as deviations from scale invariance or a running spectral index, although it would recover sharp features of high statistical significance. We use the WMAP three-year results in combination with data from a suite of higher resolution cosmic microwave background experiments (including the latest ACBAR 2008 release), as well as large-scale structure data from SDSS and 2dFGRS. We employ cross-validation to assess, using the data themselves, the optimal amount of smoothness in the primordial power spectrum consistent with the data. This minimally parametric reconstruction supports the evidence for a power law primordial power spectrum with a red tilt, but not for deviations from a power law power spectrum. Smooth variations in the primordial power spectrum are not significantly degenerate with the other cosmological parameters
Kubo, N
1995-04-01
To improve the quality of single-photon emission computed tomographic (SPECT) images, a restoration filter has been developed. This filter was designed according to practical "least squares filter" theory. It is necessary to know the object power spectrum and the noise power spectrum. The power spectrum is estimated from the power spectrum of a projection, when the high-frequency power spectrum of a projection is adequately approximated as a polynomial exponential expression. A study of the restoration with the filter based on a projection power spectrum was conducted, and compared with that of the "Butterworth" filtering method (cut-off frequency of 0.15 cycles/pixel), and "Wiener" filtering (signal-to-noise power spectrum ratio was a constant). Normalized mean-squared errors (NMSE) of the phantom, two line sources located in a 99mTc filled cylinder, were used. NMSE of the "Butterworth" filter, "Wiener" filter, and filtering based on a power spectrum were 0.77, 0.83, and 0.76 respectively. Clinically, brain SPECT images utilizing this new restoration filter improved the contrast. Thus, this filter may be useful in diagnosis of SPECT images. PMID:7776546
To improve the quality of single-photon emission computed tomographic (SPECT) images, a restoration filter has been developed. This filter was designed according to practical 'least squares filter' theory. It is necessary to know the object power spectrum and the noise power spectrum. The power spectrum is estimated from the power spectrum of a projection, when the high-frequency power spectrum of a projection is adequately approximated as a polynomial exponential expression. A study of the restoration with the filter based on a projection power spectrum was conducted, and compared with that of the 'Butterworth' filtering method (cut-off frequency of 0.15 cycles/pixel), and 'Wiener' filtering (signal-to-noise power spectrum ratio was a constant). Normalized mean-squared errors (NMSE) of the phantom, two line sources located in a 99mTc filled cylinder, were used. NMSE of the 'Butterworth' filter, 'Wiener' filter, and filtering based on a power spectrum were 0.77, 0.83, and 0.76 respectively. Clinically, brain SPECT images utilizing this new restoration filter improved the contrast. Thus, this filter may be useful in diagnosis of SPECT images. (author)
Red, Straight, no bends: primordial power spectrum reconstruction from CMB and large-scale structure
Ravenni, Andrea; Cuesta, Antonio J
2016-01-01
We present a minimally parametric, model independent reconstruction of the shape of the primordial power spectrum. Our smoothing spline technique is well-suited to search for smooth features such as deviations from scale invariance, and deviations from a power law such as running of the spectral index or small-scale power suppression. We use a comprehensive set of the state-of the art cosmological data: {\\it Planck} observations of the temperature and polarisation anisotropies of the cosmic microwave background, WiggleZ and Sloan Digital Sky Survey Data Release 7 galaxy power spectra and the Canada-France-Hawaii Lensing Survey correlation function. This reconstruction strongly supports the evidence for a power law primordial power spectrum with a red tilt and disfavours deviations from a power law power spectrum including small-scale power suppression such as that induced by significantly massive neutrinos. This offers a powerful confirmation of the inflationary paradigm, justifying the adoption of the inflat...
Near-field angular distributions of high velocity ions for low-power hall thrusters
Sullivan, Regina M.; Yost, Allison; Johnson, Lee K.
2009-01-01
Experimental angular distributions of high-energy primary ions in the near-field region of a small Hall thruster between 50-200 mm downstream of the thruster exit plane at a range of centerline angles have been determined using a highly-collimated, energy-selective diagnostic probe. The measurements reveal a wide angular distribution of ions exiting the thruster channel and the formation of a strong, axially-directed jet of ions along the thruster centerline. Comparisons are made to other exp...
Position-dependent power spectrum: a new observable in the large-scale structure
Chiang, Chi-Ting
2015-01-01
We present a new observable, position-dependent power spectrum, to measure the large-scale structure bispectrum in the squeezed configuration, where one wavenumber is much smaller than the other two. The squeezed-limit bispectrum measures how the small-scale power spectrum is modulated by a long-wavelength overdensity, which is due to gravitational evolution and possibly inflationary physics. We divide a survey into small subvolumes, compute the local power spectrum and the mean overdensity in each subvolume, and measure the correlation between them. The correlation measures the integral of the bispectrum, which is dominated by squeezed configurations if the scale of the local power spectrum is much smaller than the subvolume size. We use the separate universe approach to model how the small-scale power spectrum is affected by a long-wavelength overdensity gravitationally. This models the nonlinearity of the bispectrum better than the perturbation theory approach. Not only the new observable is easy to interp...
Falaggis, Konstantinos; Kozacki, Tomasz; Kujawinska, Malgorzata
2013-05-10
The angular spectrum (AS) method is a popular solution to the Helmholtz equation without the use of approximations. Modified band-limited AS methods are of particular interest for the cases of high-off-axis and large distance propagation problems, because conventional AS methods are impractical due to requirements regarding memory and computational effort. However, these techniques make use of rectangular-shaped filters that introduce ringing artifacts in the calculated field that are related to the Gibbs phenomenon. This work proposes AS algorithms based on a smooth band-limiting filter for accurate field computation as well as techniques that evaluate only nonzero components of the field. This enables accurate field calculations with an acceptable level of computational effort that cannot be offered by current AS methods reported in the scientific literature. PMID:23669842
Experimental activities are underway at INFN Legnaro National Laboratories (LNL) (Padua, Italy) and Pisa University aimed at angular-dependent neutron energy spectra measurements produced by the 9Be(p,xn) reaction, under a 5 MeV proton beam. This work has been performed in the framework of INFN TRASCO-BNCT project. Bonner Sphere Spectrometer (BSS), based on 6LiI (Eu) scintillator, was used with the shadow-cone technique. Proper unfolding codes, coupled to BSS response function calculated by Monte Carlo code, were finally used. The main results are reported here. - Highlights: • Bonner sphere spectrometer is used to determine the angular neutron energy spectrum of an accelerator-based BNCT facility. • The shadow-cone technique is a method used with Bonner sphere spectrometer to remove the neutron scattered contribution. • The response function matrix for the set of Bonner sphere spectrometer is calculated by Monte Carlo code. • Unfolding codes are used to obtain neutron spectra at different neutron emission angles (0°, 40°, 80° and 120°)
Borovskiy, A. V. [Department of Computer Science and Cybernetics, Baikal State University of Economics and Law, 11 Lenin Street, Irkutsk 664003 (Russian Federation); Galkin, A. L. [Coherent and Nonlinear Optics Department, A.M. Prokhorov General Physics Institute of the RAS, 38 Vavilov Street, Moscow 119991 (Russian Federation); Department of Physics of MBF, Pirogov Russian National Research Medical University, 1 Ostrovitianov Street, Moscow 117997 (Russian Federation); Kalashnikov, M. P., E-mail: galkin@kapella.gpi.ru [Max-Born-Institute for Nonlinear Optics and Short-Time Spectroscopy, 2a Max-Born-Strasse, Berlin 12489 (Germany)
2015-04-15
The new method of calculating energy spectra of accelerated electrons, based on the parameterization by their initial coordinates, is proposed. The energy spectra of electrons accelerated by Gaussian ultra-short relativistic laser pulse at a selected angle to the axis of the optical system focusing the laser pulse in a low density gas are theoretically calculated. The two-peak structure of the electron energy spectrum is obtained. Discussed are the reasons for its appearance as well as an applicability of other models of the laser field.
Sunyaev-Zel'dovich power spectrum with decaying cold dark matter
Takahashi, Keitaro; Oguri, Masamune; Ichiki, Kiyotomo
2003-01-01
Recent studies of structures of galaxies and clusters imply that dark matter might be unstable and decay with lifetime $\\Gamma^{-1}$ about the age of universe. We study the effects of the decay of cold dark matter on the Sunyaev-Zel'dovich (SZ) power spectrum. We analytically calculate the SZ power spectrum taking finite lifetime of cold dark matter into account. We find the finite lifetime of dark matter decreases the power at large scale ($l 4000$...
In the early universe, energy stored in small-scale density perturbations is quickly dissipated by Silk damping, a process that inevitably generates μ- and y-type spectral distortions of the cosmic microwave background (CMB). These spectral distortions depend on the shape and amplitude of the primordial power spectrum at wavenumbers k ∼4 Mpc–1. Here, we study constraints on the primordial power spectrum derived from COBE/FIRAS and forecasted for PIXIE. We show that measurements of μ and y impose strong bounds on the integrated small-scale power, and we demonstrate how to compute these constraints using k-space window functions that account for the effects of thermalization and dissipation physics. We show that COBE/FIRAS places a robust upper limit on the amplitude of the small-scale power spectrum. This limit is about three orders of magnitude stronger than the one derived from primordial black holes in the same scale range. Furthermore, this limit could be improved by another three orders of magnitude with PIXIE, potentially opening up a new window to early universe physics. To illustrate the power of these constraints, we consider several generic models for the small-scale power spectrum predicted by different inflation scenarios, including running-mass inflation models and inflation scenarios with episodes of particle production. PIXIE could place very tight constraints on these scenarios, potentially even ruling out running-mass inflation models if no distortion is detected. We also show that inflation models with sub-Planckian field excursion that generate detectable tensor perturbations should simultaneously produce a large CMB spectral distortion, a link that could potentially be established with PIXIE.
WIND TURBINE SIMULATION FOR TIME-DEPENDENT ANGULAR VELOCITY, TORQUE, AND POWER
YONGHO LEE
2013-01-01
Albeit the prediction of time-dependent properties of wind turbines is not required for common applications, such time-varying properties may play an important role during transient operations occurring due to various reasons. Unlike the conventional numerical simulations of wind turbine rotations that fix the angular velocity to an assumed value, the present work numerically simulates the time-varying turbine rotation in both unsteady and quasi-steady operation regimes, without specifying th...
Planck early results. XVIII. The power spectrum of cosmic infrared background anisotropies
Bucher, M.; Delabrouille, J.; Giraud-Héraud, Y.; Patanchon, G.; Piat, M.; Remazeilles, M.; Rosset, C.; Stompor, R.; Hobson, M.; Stolyarov, V.; Bhatia, R.; Blagrave, K.; Bond, J.R.; Martin, P.; Helou, G.; Shellard, P.; Yvon, D.; Linden-Vørnle, Michael; Nørgaard-Nielsen, Hans Ulrik; Toffolatti, L.; Netterfield, C.B.; Pinheiro Gonçalves, D.; Scott, D.; Oliver, S.; Juvela, M.; Keihänen, E.; Chiang, C.; Jones, W.C.; Cayón, L.; White, M.; Knox, L.; Lubin, P.M.; Zonca, A.; Matarrese, S.; De Bernardis, P.; Masi, S.; Melchiorri, A.; Piacentini, F.; Gregorio, A.; Balbi, A.; Cabella, P.; De Gasperis, G.; Mazzotta, P.; Vittorio, N.; Kneissl, R.; Dupac, X.; Mendes, L.; Giardino, G.; Laureijs, R.J.; Leonardi, R.; Tauber, J.A.; Kurki-Suonio, H.; Poutanen, T.; Umana, G.; Bonaldi, A.; Polenta, G.; Frailis, M.; Galeotta, S.; Maris, M.; Mennella, A.; Pasian, F.; Zacchei, A.; Burigana, C.; Cuttaia, F.; De Rosa, A.; Finelli, F.; Franceschi, E.; Gruppuso, A.; Mandolesi, N.; Morgante, G.; Natoli, P.; Ricciardi, S.; Sandri, M.; Terenzi, L.; Valenziano, L.; Villa, F.; Bersanelli, M.; Maino, D.; Tomasi, M.; Stivoli, F.; Désert, F.-X.; Chamballu, A.; Clements, D.L.; Jaffe, A.H.; Mortlock, D.; Novikov, D.; Rowan-Robinson, M.; Ganga, K.; Rusholme, B.; Benoît, A.; Aghanim, N.; Aumont, J.; Dole, H.; Douspis, M.; Grain, J.; Lagache, G.; Miville-Deschênes, M.-A.; Pajot, F.; Ponthieu, N.; Puget, J.-L.; Torre, J.-P.; Benabed, K.; Bouchet, F.R.; Colombi, S.; Delouis, J.-M.; Hivon, E.; Moneti, A.; Prunet, S.; Sygnet, J.-F.; Wandelt, B.D.; Fosalba, P.; Chiang, L.-Y.; Efstathiou, G.; Donzelli, S.; Eriksen, H.K.; Hansen, F.K.; Lilje, P.B.; Hoyland, R.J.; Rubiño-Martín, J.A.; Barreiro, R.B.; Herranz, D.; López-Caniego, M.; Martínez-González, E.; Vielva, P.; Bartlett, J.G.; Bock, J.J.; Doré, O.; Holmes, W.A.; Keskitalo, R.; Lawrence, C.R.; Mitra, S.; O'Dwyer, I.J.; Prézeau, G.; Rocha, G.; Seiffert, M.D.; Wade, L.A.; Davies, R.D.; Davis, R.J.; Maffei, B.; Ashdown, M.; Challinor, A.; Gratton, S.; Harrison, D.; Lasenby, A.; MacTavish, C.J.; Catalano, A.; Coulais, A.; Lamarre, J.-M.; Arnaud, M.; Starck, J.-L.; Cardoso, J.-F.; Hildebrandt, S.R.; MacÍas-Pérez, J.F.; Perotto, L.; Renault, C.; Santos, D.; Couchot, F.; Henrot-Versillé, S.; Perdereau, O.; Plaszczynski, S.; Tristram, M.; Kisner, T.S.; Smoot, G.F.; Dörl, U.; Enßlin, T.A.; Hovest, W.; Matthai, F.; Rachen, J.P.; Reinecke, M.; Riller, T.; Tuovinen, J.; Lockman, F.J.; Murphy, A.; Christensen, P.R.; Naselsky, P.; Novikov, I.; Crill, B.P.; Savini, G.; Baccigalupi, C.; Bonavera, L.; Danese, L.; De Zotti, G.; González-Nuevo, J.; Leach, S.; Perrotta, F.; Mann, R.; Ade, P.A.R.; Munshi, D.; Sudiwala, R.; Sunyaev, R.; Borrill, J.; Osborne, S.; Banday, A.J.; Bernard, J.-P.; Forni, O.; Giard, M.; Leroy, C.; Montier, L.; Pointecouteau, E.; Ristorcelli, I.; Reach, W.T.; Battaner, E.; Huffenberger, K.M.; Górski, K.M.
2011-01-01
Using Planck maps of six regions of low Galactic dust emission with a total area of about 140 deg2, we determine the angular power spectra of cosmic infrared background (CIB) anisotropies from multipole = 200 to = 2000 at 217, 353, 545 and 857 GHz. We use 21-cm observations of Hi as a tracer of t...
Classical and modern power spectrum estimation for tune measurement in CSNS RCS
Precise measurement of betatron tune is required for good operating condition of CSNS RCS. The fractional part of betatron tune is important and it can be measured by analyzing the signals of beam position from the appointed BPM. Usually these signals are contaminated during the acquisition process, therefore several power spectrum methods are used to improve the frequency resolution. In this article classical and modern power spectrum methods are used. In order to compare their performance, the results of simulation data and IQT data from J-PARC RCS are discussed. It is shown that modern power spectrum estimation has better performance than the classical ones, though the calculation is more complex. (authors)
Classical and modern power spectrum estimation for tune measurement in CSNS RCS
Yang, Xiaoyu; Fu, Shinian; Zeng, Lei; Bian, Xiaojuan
2013-01-01
Precise measurement of betatron tune is required for good operating condition of CSNS RCS. The fractional part of betatron tune is important and it can be measured by analyzing the signals of beam position from the appointed BPM. Usually these signals are contaminated during the acquisition process, therefore several power spectrum methods are used to improve the frequency resolution. In this article classical and modern power spectrum methods are used. In order to compare their performance, the results of simulation data and IQT data from J-PARC RCS are discussed. It is shown that modern power spectrum estimation has better performance than the classical ones, though the calculation is more complex.
Detection of periodic signatures in the solar power spectrum. On the track of l=1 gravity modes
García, R A; Jiménez-Reyes, S J; Ballot, J; Pallé, P L; Eff-Darwich, A; Mathur, S; Provost, J
2006-01-01
In the present work we show robust indications of the existence of g modes in the Sun using 10 years of GOLF data. The present analysis is based on the exploitation of the collective properties of the predicted low-frequency (25 to 140 microHz) g modes: their asymptotic nature, which implies a quasi equidistant separation of their periods for a given angular degree (l). The Power Spectrum (PS) of the Power Spectrum Density (PSD), reveals a significant structure indicating the presence of features (peaks) in the PSD with near equidistant periods corresponding to l=1 modes in the range n=-4 to n=-26. The study of its statistical significance of this feature was fully undertaken and complemented with Monte Carlo simulations. This structure has a confidence level better than 99.86% not to be due to pure noise. Furthermore, a detailed study of this structure suggests that the gravity modes have a much more complex structure than the one initially expected (line-widths, magnetic splittings...). Compared to the late...
Power Laws and the Cosmic Ray Energy Spectrum
Hague, J. D.; Becker, B. R.; Gold, M.S.; Matthews, J. A. J.
2006-01-01
Two separate statistical tests are applied to the AGASA and preliminary Auger Cosmic Ray Energy spectra in an attempt to find deviation from a pure power-law. The first test is constructed from the probability distribution for the maximum event of a sample drawn from a power-law. The second employs the TP-statistic, a function defined to deviate from zero when the sample deviates from the power-law form, regardless of the value of the power index. The AGASA data show no significant deviation ...
Yang, X H; Chu Yao Quan; Fang, L Z; Yang, Xiao-Hu; Feng, Long-Long; Chu, Yao-Quan; Fang, Li-Zhi
2001-01-01
The power spectrum estimator based on the discrete wavelet transform (DWT) for 3-dimensional samples has been studied. The DWT estimator for multi-dimensional samples provides two types of spectra with respect to diagonal and off-diagonal modes, which are very flexible to deal with configuration-related problems in the power spectrum detection. With simulation samples and mock catalogues of the Las Campanas redshift survey (LCRS), we show (1) the slice-like geometry of the LCRS doesn't affect the off-diagonal power spectrum with ``slice-like'' mode; (2) the Poisson sampling with the LCRS selection function doesn't cause more than 1-$\\sigma$ error in the DWT power spectrum; and (3) the powers of peculiar velocity fluctuations, which cause the redshift distortion, are approximately scale-independent. These results insure that the uncertainties of the power spectrum measurement are under control. The scatter of the DWT power spectra of the six strips of the LCRS survey is found to be rather small. It is less tha...
A Measurement of Primordial Non-Gaussianity Using WMAP 5-Year Temperature Skewness Power Spectrum
Smidt, Joseph; Amblard, Alexandre; Serra, Paolo; Cooray, Asantha
2009-01-01
We constrain the primordial non-Gaussianity parameter of the local model f_{NL} using the skewness power spectrum associated with the two-to-one cumulant correlator of cosmic microwave background temperature anisotropies. This bispectrum-related power spectrum was constructed after weighting the temperature map with the appropriate window functions to form an estimator that probes the multipolar dependence of the underlying bispectrum associated with the primordial non-Gaussianity. We also es...
Effect of noise on the power spectrum of passively mode-locked lasers
Eliyahu, Danny; Salvatore, Randal A.; Yariv, Amnon
1997-01-01
We analyze the effects of noise on the power spectrum of pulse trains generated by a continuously operating passively mode-locked laser. The shape of the different harmonics of the power spectrum is calculated in the presence of correlated timing fluctuations between neighboring pulses and in the presence of amplitude fluctuations. The spectra at the different harmonics are influenced mainly by the nonstationary timing-jitter fluctuations; amplitude fluctuations slightly modify the spectral t...
Dalton, Brian H; Power, Geoffrey A; Paturel, Justin R; Rice, Charles L
2015-06-01
The underlying factors related to the divergent findings of age-related fatigue for dynamic tasks are not well understood. The purpose here was to investigate age-related fatigability and recovery between a repeated constrained (isokinetic) and an unconstrained velocity (isotonic) task, in which participants performed fatiguing contractions at the velocity (isokinetic) or resistance (isotonic) corresponding with maximal power. To compare between tasks, isotonic torque-power relationships were constructed prior to and following both fatiguing tasks and during short-term recovery. Contractile properties were recorded from 9 old (~75 years) and 11 young (~25 years) men during three testing sessions. In the first session, maximal power was assessed, and sessions 2 and 3 involved an isokinetic or an isotonic concentric fatigue task performed until maximal power was reduced by 40 %. Compared with young, the older men performed the same number of contractions to task failure for the isokinetic task (~45 contractions), but 20 % fewer for the isotonic task (p < 0.05). Regardless of age and task, maximal voluntary isometric contraction strength, angular velocity, and power were reduced by ~30, ~13, and ~25 %, respectively, immediately following task failure, and only isometric torque was not recovered fully by 10 min. In conclusion, older men are more fatigable than the young when performing a repetitive maximal dynamic task at a relative resistance (isotonic) but not an absolute velocity (isokinetic), corresponding to maximal power. PMID:25943700
Siemens's spectrum of deliveries and services for nuclear power plants
In 2001, Siemens and Framatome merged their nuclear activities in the present Areva NP joint venture. Siemens has since focused on the construction and further development of conventional power plants and on the so-called conventional island (CI), the non-nuclear part of a nuclear power plant, i.e. the steam turbine, generator, and plant I and C systems, and also on service for the conventional part of nuclear power plants. Its role as a minority shareholder in Areva NP constrained Siemens. For this reason, the company in January 2009 decided to terminate its interest in Areva NP effective January 30, 2012. By January 2012 at the latest, Siemens will transfer to the majority shareholder Areva, holding 66 percent of the shares, its interest in the joint venture. For the time being, the joint venture still entails certain limitations to Siemens's activities in the nuclear field. Its delivery of the conventional island for the Olkiluoto 3 (OL3) nuclear power plant in Finland confirms the company's know-how in power plant construction. When commissioned, its 1,720 MW power will make OL3 the world's largest nuclear generating unit. The turbo-generator of the CI comprises a double-flow HP turbine and a 6-flow LP turbine. The driven 4-pole generator with a power of up to 2,200 MVA consists of a water-cooled stator and a hydrogen-cooled rotor. (orig.)