International Nuclear Information System (INIS)
Cui Weiguang; Zhang Pengjie; Yang Xiaohu
2010-01-01
A large fraction of cosmological information on dark energy and gravity is encoded in the nonlinear regime. Precision cosmology thus requires precision modeling of nonlinearities in general dark energy and modified gravity models. We modify the Gadget-2 code and run a series of N-body simulations on modified gravity cosmology to study the nonlinearities. The modified gravity model that we investigate in the present paper is characterized by a single parameter ζ, which determines the enhancement of particle acceleration with respect to general relativity (GR), given the identical mass distribution (ζ=1 in GR). The first nonlinear statistics we investigate is the nonlinear matter power spectrum at k < or approx. 3h/Mpc, which is the relevant range for robust weak lensing power spectrum modeling at l < or approx. 2000. In this study, we focus on the relative difference in the nonlinear power spectra at corresponding redshifts where different gravity models have the same linear power spectra. This particular statistics highlights the imprint of modified gravity in the nonlinear regime and the importance of including the nonlinear regime in testing GR. By design, it is less susceptible to the sample variance and numerical artifacts. We adopt a mass assignment method based on wavelet to improve the power spectrum measurement. We run a series of tests to determine the suitable simulation specifications (particle number, box size, and initial redshift). We find that, the nonlinear power spectra can differ by ∼30% for 10% deviation from GR (|ζ-1|=0.1) where the rms density fluctuations reach 10. This large difference, on one hand, shows the richness of information on gravity in the corresponding scales, and on the other hand, invalidates simple extrapolations of some existing fitting formulae to modified gravity cosmology.
Energy Technology Data Exchange (ETDEWEB)
Heitmann, Katrin [Los Alamos National Laboratory; Habib, Salman [Los Alamos National Laboratory; Higdon, David [Los Alamos National Laboratory; Williams, Brian J [Los Alamos National Laboratory; White, Martin [Los Alamos National Laboratory; Wagner, Christian [Los Alamos National Laboratory
2008-01-01
The power spectrum of density fluctuations is a foundational source of cosmological information. Precision cosmological probes targeted primarily at investigations of dark energy require accurate theoretical determinations of the power spectrum in the nonlinear regime. To exploit the observational power of future cosmological surveys, accuracy demands on the theory are at the one percent level or better. Numerical simulations are currently the only way to produce sufficiently error-controlled predictions for the power spectrum. The very high computational cost of (precision) N-body simulations is a major obstacle to obtaining predictions in the nonlinear regime, while scanning over cosmological parameters. Near-future observations, however, are likely to provide a meaningful constraint only on constant dark energy equation of state 'wCDM' cosmologies. In this paper we demonstrate that a limited set of only 37 cosmological models -- the 'Coyote Universe' suite -- can be used to predict the nonlinear matter power spectrum at the required accuracy over a prior parameter range set by cosmic microwave background observations. This paper is the second in a series of three, with the final aim to provide a high-accuracy prediction scheme for the nonlinear matter power spectrum for wCDM cosmologies.
Nonlinear cosmological consistency relations and effective matter stresses
International Nuclear Information System (INIS)
Ballesteros, Guillermo; Hollenstein, Lukas; Jain, Rajeev Kumar; Kunz, Martin
2012-01-01
We propose a fully nonlinear framework to construct consistency relations for testing generic cosmological scenarios using the evolution of large scale structure. It is based on the covariant approach in combination with a frame that is purely given by the metric, the normal frame. As an example, we apply this framework to the ΛCDM model, by extending the usual first order conditions on the metric potentials to second order, where the two potentials start to differ from each other. We argue that working in the normal frame is not only a practical choice but also helps with the physical interpretation of nonlinear dynamics. In this frame, effective pressures and anisotropic stresses appear at second order in perturbation theory, even for ''pressureless'' dust. We quantify their effect and compare them, for illustration, to the pressure of a generic clustering dark energy fluid and the anisotropic stress in the DGP model. Besides, we also discuss the effect of a mismatch of the potentials on the determination of galaxy bias
International Nuclear Information System (INIS)
Hamann, Jan; Hannestad, Steen; Melchiorri, Alessandro; Wong, Yvonne Y Y
2008-01-01
We explore and compare the performances of two non-linear correction and scale-dependent biasing models for the extraction of cosmological information from galaxy power spectrum data, especially in the context of beyond-ΛCDM (CDM: cold dark matter) cosmologies. The first model is the well known Q model, first applied in the analysis of Two-degree Field Galaxy Redshift Survey data. The second, the P model, is inspired by the halo model, in which non-linear evolution and scale-dependent biasing are encapsulated in a single non-Poisson shot noise term. We find that while the two models perform equally well in providing adequate correction for a range of galaxy clustering data in standard ΛCDM cosmology and in extensions with massive neutrinos, the Q model can give unphysical results in cosmologies containing a subdominant free-streaming dark matter whose temperature depends on the particle mass, e.g., relic thermal axions, unless a suitable prior is imposed on the correction parameter. This last case also exposes the danger of analytic marginalization, a technique sometimes used in the marginalization of nuisance parameters. In contrast, the P model suffers no undesirable effects, and is the recommended non-linear correction model also because of its physical transparency
Hamann, Jan; Hannestad, Steen; Melchiorri, Alessandro; Wong, Yvonne Y. Y.
2008-07-01
We explore and compare the performances of two non-linear correction and scale-dependent biasing models for the extraction of cosmological information from galaxy power spectrum data, especially in the context of beyond-ΛCDM (CDM: cold dark matter) cosmologies. The first model is the well known Q model, first applied in the analysis of Two-degree Field Galaxy Redshift Survey data. The second, the P model, is inspired by the halo model, in which non-linear evolution and scale-dependent biasing are encapsulated in a single non-Poisson shot noise term. We find that while the two models perform equally well in providing adequate correction for a range of galaxy clustering data in standard ΛCDM cosmology and in extensions with massive neutrinos, the Q model can give unphysical results in cosmologies containing a subdominant free-streaming dark matter whose temperature depends on the particle mass, e.g., relic thermal axions, unless a suitable prior is imposed on the correction parameter. This last case also exposes the danger of analytic marginalization, a technique sometimes used in the marginalization of nuisance parameters. In contrast, the P model suffers no undesirable effects, and is the recommended non-linear correction model also because of its physical transparency.
Nonlinear electrodynamics and cosmology
International Nuclear Information System (INIS)
Breton, Nora
2010-01-01
Nonlinear electrodynamics (NLED) generalizes Maxwell's theory for strong fields. When coupled to general relativity NLED presents interesting features like the non-vanishing of the trace of the energy-momentum tensor that leads to the possibility of violation of some energy conditions and of acting as a repulsive contribution in the Raychaudhuri equation. This theory is worth to study in cosmological and astrophysical situations characterized by strong electromagnetic and gravitational fields.
Cosmological leverage from the matter power spectrum in the presence of baryon and nonlinear effects
International Nuclear Information System (INIS)
Bielefeld, Jannis; Huterer, Dragan; Linder, Eric V.
2015-01-01
We investigate how the use of higher wavenumbers (smaller scales) in the galaxy clustering power spectrum influences cosmological constraints. We take into account uncertainties from nonlinear density fluctuations, (scale dependent) galaxy bias, and baryonic effects. Allowing for substantially model independent uncertainties through separate fit parameters in each wavenumber bin that also allow for the redshift evolution, we quantify strong gains in dark energy and neutrino mass leverage with increasing maximum wavenumber, despite marginalizing over numerous (up to 125) extra fit parameters. The leverage is due to not only an increased number of modes but, more significantly, breaking of degeneracies beyond the linear regime
International Nuclear Information System (INIS)
Effenberger, R.
1974-09-01
The author summarizes some of the many questions and answers which have been raised over the years regarding the nature of matter, the origin of its forms and the associated concept of cosmology including the formation of the universe, our place in it and its course of evolution. An examination of the development of the classical concept of matter and its subsequent transformations within the space-time fields of relativity and quantum theory is also presented
Tkachev, Igor
2017-01-01
This lecture course covers cosmology from the particle physicist perspective. Therefore, the emphasis will be on the evidence for the new physics in cosmological and astrophysical data together with minimal theoretical frameworks needed to understand and appreciate the evidence. I review the case for non-baryonic dark matter and describe popular models which incorporate it. In parallel, the story of dark energy will be developed, which includes accelerated expansion of the Universe today, the Universe origin in the Big Bang, and support for the Inflationary theory in CMBR data.
International Nuclear Information System (INIS)
Schramm, D.N.; Fields, B.; Thomas, D.
1992-01-01
The possible implications of the quark-hadron transition for cosmology are explored. Possible surviving signatures are discussed. In particular, the possibility of generating a dark matter candidate such as strange nuggets or planetary mass black holes is noted. Much discussion is devoted to the possible role of the transition for cosmological nucleosynthesis. It is emphasized that even an optimized first order phase transition will not significantly alter the nucleosynthesis constraints on the cosmological baryon density nor on neutrino counting. However, it is noted that Be and B observations in old stars may eventually be able to be a signature of a cosmologically significant quark-hadron transition. It is pointed out that the critical point in this regard is whether the observed B/Be ratio can be produced by spallation processes or requires cosmological input. Spallation cannot produce a B/Be ratio below 7.6. A supporting signature would be Be and B ratios to oxygen that greatly exceed galactic values. At present, all data is still consistent with a spallagenic origin
Cosmological effects of nonlinear electrodynamics
International Nuclear Information System (INIS)
Novello, M; Goulart, E; Salim, J M; Bergliaffa, S E Perez
2007-01-01
It will be shown that a given realization of nonlinear electrodynamics, used as a source of Einstein's equations, generates a cosmological model with interesting features, namely a phase of current cosmic acceleration, and the absence of an initial singularity, thus pointing to a way of solving two important problems in cosmology
Energy Technology Data Exchange (ETDEWEB)
Schramm, D.N.
1992-03-01
The cosmological dark matter problem is reviewed. The Big Bang Nucleosynthesis constraints on the baryon density are compared with the densities implied by visible matter, dark halos, dynamics of clusters, gravitational lenses, large-scale velocity flows, and the {Omega} = 1 flatness/inflation argument. It is shown that (1) the majority of baryons are dark; and (2) non-baryonic dark matter is probably required on large scales. It is also noted that halo dark matter could be either baryonic or non-baryonic. Descrimination between ``cold`` and ``hot`` non-baryonic candidates is shown to depend on the assumed ``seeds`` that stimulate structure formation. Gaussian density fluctuations, such as those induced by quantum fluctuations, favor cold dark matter, whereas topological defects such as strings, textures or domain walls may work equally or better with hot dark matter. A possible connection between cold dark matter, globular cluster ages and the Hubble constant is mentioned. Recent large-scale structure measurements, coupled with microwave anisotropy limits, are shown to raise some questions for the previously favored density fluctuation picture. Accelerator and underground limits on dark matter candidates are also reviewed.
Energy Technology Data Exchange (ETDEWEB)
Schramm, D.N.
1992-03-01
The cosmological dark matter problem is reviewed. The Big Bang Nucleosynthesis constraints on the baryon density are compared with the densities implied by visible matter, dark halos, dynamics of clusters, gravitational lenses, large-scale velocity flows, and the {Omega} = 1 flatness/inflation argument. It is shown that (1) the majority of baryons are dark; and (2) non-baryonic dark matter is probably required on large scales. It is also noted that halo dark matter could be either baryonic or non-baryonic. Descrimination between cold'' and hot'' non-baryonic candidates is shown to depend on the assumed seeds'' that stimulate structure formation. Gaussian density fluctuations, such as those induced by quantum fluctuations, favor cold dark matter, whereas topological defects such as strings, textures or domain walls may work equally or better with hot dark matter. A possible connection between cold dark matter, globular cluster ages and the Hubble constant is mentioned. Recent large-scale structure measurements, coupled with microwave anisotropy limits, are shown to raise some questions for the previously favored density fluctuation picture. Accelerator and underground limits on dark matter candidates are also reviewed.
International Nuclear Information System (INIS)
Schramm, D.N.
1992-03-01
The cosmological dark matter problem is reviewed. The Big Bang Nucleosynthesis constraints on the baryon density are compared with the densities implied by visible matter, dark halos, dynamics of clusters, gravitational lenses, large-scale velocity flows, and the Ω = 1 flatness/inflation argument. It is shown that (1) the majority of baryons are dark; and (2) non-baryonic dark matter is probably required on large scales. It is also noted that halo dark matter could be either baryonic or non-baryonic. Descrimination between ''cold'' and ''hot'' non-baryonic candidates is shown to depend on the assumed ''seeds'' that stimulate structure formation. Gaussian density fluctuations, such as those induced by quantum fluctuations, favor cold dark matter, whereas topological defects such as strings, textures or domain walls may work equally or better with hot dark matter. A possible connection between cold dark matter, globular cluster ages and the Hubble constant is mentioned. Recent large-scale structure measurements, coupled with microwave anisotropy limits, are shown to raise some questions for the previously favored density fluctuation picture. Accelerator and underground limits on dark matter candidates are also reviewed
Entropy, matter, and cosmology.
Prigogine, I; Géhéniau, J
1986-09-01
The role of irreversible processes corresponding to creation of matter in general relativity is investigated. The use of Landau-Lifshitz pseudotensors together with conformal (Minkowski) coordinates suggests that this creation took place in the early universe at the stage of the variation of the conformal factor. The entropy production in this creation process is calculated. It is shown that these dissipative processes lead to the possibility of cosmological models that start from empty conditions and gradually build up matter and entropy. Gravitational entropy takes a simple meaning as associated to the entropy that is necessary to produce matter. This leads to an extension of the third law of thermodynamics, as now the zero point of entropy becomes the space-time structure out of which matter is generated. The theory can be put into a convenient form using a supplementary "C" field in Einstein's field equations. The role of the C field is to express the coupling between gravitation and matter leading to irreversible entropy production.
Introduction. Cosmology meets condensed matter.
Kibble, T W B; Pickett, G R
2008-08-28
At first sight, low-temperature condensed-matter physics and early Universe cosmology seem worlds apart. Yet, in the last few years a remarkable synergy has developed between the two. It has emerged that, in terms of their mathematical description, there are surprisingly close parallels between them. This interplay has been the subject of a very successful European Science Foundation (ESF) programme entitled COSLAB ('Cosmology in the Laboratory') that ran from 2001 to 2006, itself built on an earlier ESF network called TOPDEF ('Topological Defects: Non-equilibrium Field Theory in Particle Physics, Condensed Matter and Cosmology'). The articles presented in this issue of Philosophical Transactions A are based on talks given at the Royal Society Discussion Meeting 'Cosmology meets condensed matter', held on 28 and 29 January 2008. Many of the speakers had participated earlier in the COSLAB programme, but the strength of the field is illustrated by the presence also of quite a few new participants.
Omnes, R.
1973-01-01
The possible existence of antimatter on a large scale in the universe is evaluated. As a starting point, an attempt was made to understand the origin of matter as being essentially analogous to the origin of backgound thermal radiation. Several theories and models are examined, with particular emphasis on nucleon-antinucleon interactions at intermediate energies. Data also cover annihilation interaction with the matter-antimatter boundary to produce the essential fluid motion known as coalesence.
International Nuclear Information System (INIS)
Effenberger, R.
1975-07-01
The author looks empirically at the processes by which the various forms of matter, the chemical elements, come into existence. In doing so he examines unification within relativity and quantum mechanics, atomic and nuclear structure, the quantum idea as a unifying concept, particle physics and finally nucleosynthesis and a viable nucleosynthetic theory
Cosmological N-body simulations with generic hot dark matter
DEFF Research Database (Denmark)
Brandbyge, Jacob; Hannestad, Steen
2017-01-01
We have calculated the non-linear effects of generic fermionic and bosonic hot dark matter components in cosmological N-body simulations. For sub-eV masses, the non-linear power spectrum suppression caused by thermal free-streaming resembles the one seen for massive neutrinos, whereas for masses...
Axion cold dark matter in nonstandard cosmologies
International Nuclear Information System (INIS)
Visinelli, Luca; Gondolo, Paolo
2010-01-01
We study the parameter space of cold dark matter axions in two cosmological scenarios with nonstandard thermal histories before big bang nucleosynthesis: the low-temperature reheating (LTR) cosmology and the kination cosmology. If the Peccei-Quinn symmetry breaks during inflation, we find more allowed parameter space in the LTR cosmology than in the standard cosmology and less in the kination cosmology. On the contrary, if the Peccei-Quinn symmetry breaks after inflation, the Peccei-Quinn scale is orders of magnitude higher than standard in the LTR cosmology and lower in the kination cosmology. We show that the axion velocity dispersion may be used to distinguish some of these nonstandard cosmologies. Thus, axion cold dark matter may be a good probe of the history of the Universe before big bang nucleosynthesis.
A new cosmological paradigm: the cosmological constant and dark matter
International Nuclear Information System (INIS)
Krauss, L.M.
1998-01-01
The Standard Cosmological Model of the 1980 close-quote s is no more. I describe the definitive evidence that the density of matter is insufficient to result in a flat universe, as well as the mounting evidence that the cosmological constant is not zero. I finally discuss the implications of these results for particle physics and direct searches for non-baryonic dark matter. copyright 1998 American Institute of Physics
Condensed matter analogues of cosmology
Kibble, Tom; Srivastava, Ajit
2013-10-01
It is always exciting when developments in one branch of physics turn out to have relevance in a quite different branch. It would be hard to find two branches farther apart in terms of energy scales than early-universe cosmology and low-temperature condensed matter physics. Nevertheless ideas about the formation of topological defects during rapid phase transitions that originated in the context of the very early universe have proved remarkably fruitful when applied to a variety of condensed matter systems. The mathematical frameworks for describing these systems can be very similar. This interconnection has led to a deeper understanding of the phenomena in condensed matter systems utilizing ideas from cosmology. At the same time, one can view these condensed matter analogues as providing, at least in a limited sense, experimental access to the phenomena of the early universe for which no direct probe is possible. As this special issue well illustrates, this remains a dynamic and exciting field. The basic idea is that when a system goes through a rapid symmetry-breaking phase transition from a symmetric phase into one with spontaneously broken symmetry, the order parameter may make different choices in different regions, creating domains that when they meet can trap defects. The scale of those domains, and hence the density of defects, is constrained by the rate at which the system goes through the transition and the speed with which order parameter information propagates. This is what has come to be known as the Kibble-Zurek mechanism. The resultant scaling laws have now been tested in a considerable variety of different systems. The earliest experiments illustrating the analogy between cosmology and condensed matter were in liquid crystals, in particular on the isotropic-to-nematic transition, primarily because it is very easy to induce the phase transition (typically at room temperature) and to image precisely what is going on. This field remains one of the
Cosmological N -body simulations with generic hot dark matter
Energy Technology Data Exchange (ETDEWEB)
Brandbyge, Jacob; Hannestad, Steen, E-mail: jacobb@phys.au.dk, E-mail: sth@phys.au.dk [Department of Physics and Astronomy, University of Aarhus, Ny Munkegade 120, DK–8000 Aarhus C (Denmark)
2017-10-01
We have calculated the non-linear effects of generic fermionic and bosonic hot dark matter components in cosmological N -body simulations. For sub-eV masses, the non-linear power spectrum suppression caused by thermal free-streaming resembles the one seen for massive neutrinos, whereas for masses larger than 1 eV, the non-linear relative suppression of power is smaller than in linear theory. We furthermore find that in the non-linear regime, one can map fermionic to bosonic models by performing a simple transformation.
Nonlinear evolution of f(R) cosmologies. I. Methodology
International Nuclear Information System (INIS)
Oyaizu, Hiroaki
2008-01-01
We introduce the method and the implementation of a cosmological simulation of a class of metric-variation f(R) models that accelerate the cosmological expansion without a cosmological constant and evade solar-system bounds of small-field deviations to general relativity. Such simulations are shown to reduce to solving a nonlinear Poisson equation for the scalar degree of freedom introduced by the f(R) modifications. We detail the method to efficiently solve the nonlinear Poisson equation by using a Newton-Gauss-Seidel relaxation scheme coupled with the multigrid method to accelerate the convergence. The simulations are shown to satisfy tests comparing the simulated outcome to analytical solutions for simple situations, and the dynamics of the simulations are tested with orbital and Zeldovich collapse tests. Finally, we present several static and dynamical simulations using realistic cosmological parameters to highlight the differences between standard physics and f(R) physics. In general, we find that the f(R) modifications result in stronger gravitational attraction that enhances the dark matter power spectrum by ∼20% for large but observationally allowed f(R) modifications. A more detailed study of the nonlinear f(R) effects on the power spectrum are presented in a companion paper.
Long wavelength limit of evolution of nonlinear cosmological perturbations
International Nuclear Information System (INIS)
Hamazaki, Takashi
2008-01-01
In the general matter composition where the multiple scalar fields and the multiple perfect fluids coexist, in the leading order of the gradient expansion, we construct all of the solutions of the nonlinear evolutions of the locally homogeneous universe. From the momentum constraint, we derive the constraints which the solution constants of the locally homogeneous universe must satisfy. We construct the gauge invariant perturbation variables in the arbitrarily higher order nonlinear cosmological perturbation theory around the spatially flat Friedmann-Robertson-Walker universe. We construct the nonlinear long wavelength limit formula representing the long wavelength limit of the evolution of the nonlinear gauge invariant perturbation variables in terms of perturbations of the evolutions of the locally homogeneous universe. By using the long wavelength limit formula, we investigate the evolution of nonlinear cosmological perturbations in the universe dominated by the multiple slow rolling scalar fields with an arbitrary potential. The τ function and the N potential introduced in this paper make it possible to write the evolution of the multiple slow rolling scalar fields with an arbitrary interaction potential and the arbitrarily higher order nonlinear Bardeen parameter at the end of the slow rolling phase analytically. It is shown that the nonlinear parameters such as f NL and g NL are suppressed by the slow rolling expansion parameters.
Fundamental Particle Structure in the Cosmological Dark Matter
Khlopov, Maxim
2013-11-01
The nonbaryonic dark matter of the universe is assumed to consist of new stable forms of matter. Their stability reflects symmetry of micro-world and mechanisms of its symmetry breaking. Particle candidates for cosmological dark matter are lightest particles that bear new conserved quantum numbers. Dark matter particles may represent ideal gas of noninteracting particles. Self-interacting dark matter weakly or superweakly coupled to ordinary matter is also possible, reflecting nontrivial pattern of particle symmetry in the hidden sector of particle theory. In the early universe the structure of particle symmetry breaking gives rise to cosmological phase transitions, from which macroscopic cosmological defects or primordial nonlinear structures can be originated. Primordial black holes (PBHs) can be not only a candidate for dark matter, but also represent a universal probe for superhigh energy physics in the early universe. Evaporating PBHs turn to be a source of even superweakly interacting particles, while clouds of massive PBHs can serve as nonlinear seeds for galaxy formation. The observed broken symmetry of the three known families may provide a simultaneous solution for the problems of the mass of neutrino and strong CP-violation in the unique framework of models of horizontal unification. Dark matter candidates can also appear in the new families of quarks and leptons and the existence of new stable charged leptons and quarks is possible, hidden in elusive "dark atoms." Such possibility, strongly restricted by the constraints on anomalous isotopes of light elements, is not excluded in scenarios that predict stable double charged particles. The excessive -2 charged particles are bound in these scenarios with primordial helium in O-helium "atoms," maintaining specific nuclear-interacting form of the dark matter, which may provide an interesting solution for the puzzles of the direct dark matter searches. In the context of cosmoparticle physics, studying
Cosmological simulations of multicomponent cold dark matter.
Medvedev, Mikhail V
2014-08-15
The nature of dark matter is unknown. A number of dark matter candidates are quantum flavor-mixed particles but this property has never been accounted for in cosmology. Here we explore this possibility from the first principles via extensive N-body cosmological simulations and demonstrate that the two-component dark matter model agrees with observational data at all scales. Substantial reduction of substructure and flattening of density profiles in the centers of dark matter halos found in simulations can simultaneously resolve several outstanding puzzles of modern cosmology. The model shares the "why now?" fine-tuning caveat pertinent to all self-interacting models. Predictions for direct and indirect detection dark matter experiments are made.
Cosmological Constraints on Mirror Matter Parameters
International Nuclear Information System (INIS)
Wallemacq, Quentin; Ciarcelluti, Paolo
2014-01-01
Up-to-date estimates of the cosmological parameters are presented as a result of numerical simulations of cosmic microwave background and large scale structure, considering a flat Universe in which the dark matter is made entirely or partly of mirror matter, and the primordial perturbations are scalar adiabatic and in linear regime. A statistical analysis using the Markov Chain Monte Carlo method allows to obtain constraints of the cosmological parameters. As a result, we show that a Universe with pure mirror dark matter is statistically equivalent to the case of an admixture with cold dark matter. The upper limits for the ratio of the temperatures of ordinary and mirror sectors are around 0.3 for both the cosmological models, which show the presence of a dominant fraction of mirror matter, 0.06≲Ω_m_i_r_r_o_rh"2≲0.12.
Sasaki, Misao; Wands, David
2010-06-01
In recent years there has been a resurgence of interest in the study of non-linear perturbations of cosmological models. This has been the result of both theoretical developments and observational advances. New theoretical challenges arise at second and higher order due to mode coupling and the need to develop new gauge-invariant variables beyond first order. In particular, non-linear interactions lead to deviations from a Gaussian distribution of primordial perturbations even if initial vacuum fluctuations are exactly Gaussian. These non-Gaussianities provide an important probe of models for the origin of structure in the very early universe. We now have a detailed picture of the primordial distribution of matter from surveys of the cosmic microwave background, notably NASA's WMAP satellite. The situation will continue to improve with future data from the ESA Planck satellite launched in 2009. To fully exploit these data cosmologists need to extend non-linear cosmological perturbation theory beyond the linear theory that has previously been sufficient on cosmological scales. Another recent development has been the realization that large-scale structure, revealed in high-redshift galaxy surveys, could also be sensitive to non-linearities in the primordial curvature perturbation. This focus section brings together a collection of invited papers which explore several topical issues in this subject. We hope it will be of interest to theoretical physicists and astrophysicists alike interested in understanding and interpreting recent developments in cosmological perturbation theory and models of the early universe. Of course it is only an incomplete snapshot of a rapidly developing field and we hope the reader will be inspired to read further work on the subject and, perhaps, fill in some of the missing pieces. This focus section is dedicated to the memory of Lev Kofman (1957-2009), an enthusiastic pioneer of inflationary cosmology and non-Gaussian perturbations.
Cold dark matter in brane cosmology scenario
International Nuclear Information System (INIS)
Dahab, Eiman Abou El; Khalil, Shaaban
2006-01-01
We analyze the dark matter problem in the context of brane cosmology. We investigate the impact of the non-conventional brane cosmology on the relic abundance of non-relativistic stable particles in high and low reheating temperature scenarios. We show that in case of high reheating temperature, the brane cosmology may enhance the dark matter relic density by many order of magnitudes and a stringent lower bound on the five dimensional scale is obtained. We also consider low reheating temperature scenarios with chemical equilibrium and non-equilibrium. We emphasize that in non-equilibrium case, the resulting relic density is very small. While with equilibrium, it is increased by a factor of O(10 2 ) with respect to the standard thermal production. Therefore, dark matter particles with large cross section, which is favored by detection expirements, can be consistent with the recent relic density observational limits
Quark matter in astrophysics and cosmology
International Nuclear Information System (INIS)
Olinto, A.V.
1987-10-01
We dicuss the role of quark matter in astrophysics and cosmology. The implications of the dynamics of the quark-hadron phase transition in the early universe for the element abundances from big bang nucleosynthesis and the composition of the dark matter in the universe are addressed. We discuss the possibility of deciding on an equation of state for high density matter by observing the cooling of a neutron star remnant of SN1987A. Quark matter models for the Centauros events, Cygnus X-3 cosmic ray events, high energy gamma-ray bursts and the solar neutrino problem are described. 25 refs., 3 figs
Remapping dark matter halo catalogues between cosmological simulations
Mead, A. J.; Peacock, J. A.
2014-05-01
We present and test a method for modifying the catalogue of dark matter haloes produced from a given cosmological simulation, so that it resembles the result of a simulation with an entirely different set of parameters. This extends the method of Angulo & White, which rescales the full particle distribution from a simulation. Working directly with the halo catalogue offers an advantage in speed, and also allows modifications of the internal structure of the haloes to account for non-linear differences between cosmologies. Our method can be used directly on a halo catalogue in a self-contained manner without any additional information about the overall density field; although the large-scale displacement field is required by the method, this can be inferred from the halo catalogue alone. We show proof of concept of our method by rescaling a matter-only simulation with no baryon acoustic oscillation (BAO) features to a more standard Λ cold dark matter model containing a cosmological constant and a BAO signal. In conjunction with the halo occupation approach, this method provides a basis for the rapid generation of mock galaxy samples spanning a wide range of cosmological parameters.
Inhomogenous loop quantum cosmology with matter
International Nuclear Information System (INIS)
Martín-de Bias, D; Mena Marugán, G A; Martín-Benito, M
2012-01-01
The linearly polarized Gowdy T 3 model with a massless scalar field with the same symmetries as the metric is quantized by applying a hybrid approach. The homogeneous geometry degrees of freedom are loop quantized, fact which leads to the resolution of the cosmological singularity, while a Fock quantization is employed for both matter and gravitational inhomogeneities. Owing to the inclusion of the massless scalar field this system allows us to modelize flat Friedmann-Robertson-Walker cosmologies filled with inhomogeneities propagating in one direction. It provides a perfect scenario to study the quantum back-reaction between the inhomogeneities and the polymeric homogeneous and isotropic background.
The Cosmology of Composite Inelastic Dark Matter
Energy Technology Data Exchange (ETDEWEB)
Spier Moreira Alves, Daniele; Behbahani, Siavosh R.; /SLAC /Stanford U., ITP; Schuster, Philip; Wacker, Jay G.; /SLAC
2011-08-19
Composite dark matter is a natural setting for implementing inelastic dark matter - the O(100 keV) mass splitting arises from spin-spin interactions of constituent fermions. In models where the constituents are charged under an axial U(1) gauge symmetry that also couples to the Standard Model quarks, dark matter scatters inelastically off Standard Model nuclei and can explain the DAMA/LIBRA annual modulation signal. This article describes the early Universe cosmology of a minimal implementation of a composite inelastic dark matter model where the dark matter is a meson composed of a light and a heavy quark. The synthesis of the constituent quarks into dark hadrons results in several qualitatively different configurations of the resulting dark matter composition depending on the relative mass scales in the system.
International Nuclear Information System (INIS)
Novikov, I.D.
1979-01-01
Progress made by this Commission over the period 1976-1978 is reviewed. Topics include the Hubble constant, deceleration parameter, large-scale distribution of matter in the universe, radio astronomy and cosmology, space astronomy and cosmology, formation of galaxies, physics near the cosmological singularity, and unconventional cosmological models. (C.F.)
Growth of matter perturbation in quintessence cosmology
Mulki, Fargiza A. M.; Wulandari, Hesti R. T.
2017-01-01
Big bang theory states that universe emerged from singularity with very high temperature and density, then expands homogeneously and isotropically. This theory gives rise standard cosmological principle which declares that universe is homogeneous and isotropic on large scales. However, universe is not perfectly homogeneous and isotropic on small scales. There exist structures starting from clusters, galaxies even to stars and planetary system scales. Cosmological perturbation theory is a fundamental theory that explains the origin of structures. According to this theory, the structures can be regarded as small perturbations in the early universe, which evolves as the universe expands. In addition to the problem of inhomogeneities of the universe, observations of supernovae Ia suggest that our universe is being accelerated. Various models of dark energy have been proposed to explain cosmic acceleration, one of them is cosmological constant. Because of several problems arise from cosmological constant, the alternative models have been proposed, one of these models is quintessence. We reconstruct growth of structure model following quintessence scenario at several epochs of the universe, which is specified by the effective equation of state parameters for each stage. Discussion begins with the dynamics of quintessence, in which exponential potential is analytically derived, which leads to various conditions of the universe. We then focus on scaling and quintessence dominated solutions. Subsequently, we review the basics of cosmological perturbation theory and derive formulas to investigate how matter perturbation evolves with time in subhorizon scales which leads to structure formation, and also analyze the influence of quintessence to the structure formation. From analytical exploration, we obtain the growth rate of matter perturbation and the existence of quintessence as a dark energy that slows down the growth of structure formation of the universe.
Nonlinear evolution of f(R) cosmologies. II. Power spectrum
International Nuclear Information System (INIS)
Oyaizu, Hiroaki; Hu, Wayne; Lima, Marcos
2008-01-01
We carry out a suite of cosmological simulations of modified action f(R) models where cosmic acceleration arises from an alteration of gravity instead of dark energy. These models introduce an extra scalar degree of freedom which enhances the force of gravity below the inverse mass or Compton scale of the scalar. The simulations exhibit the so-called chameleon mechanism, necessary for satisfying local constraints on gravity, where this scale depends on environment, in particular, the depth of the local gravitational potential. We find that the chameleon mechanism can substantially suppress the enhancement of power spectrum in the nonlinear regime if the background field value is comparable to or smaller than the depth of the gravitational potentials of typical structures. Nonetheless power spectrum enhancements at intermediate scales remain at a measurable level for models even when the expansion history is indistinguishable from a cosmological constant, cold dark matter model. Simple scaling relations that take the linear power spectrum into a nonlinear spectrum fail to capture the modifications of f(R) due to the change in collapsed structures, the chameleon mechanism, and the time evolution of the modifications.
Cosmological implications of Dark Matter bound states
Energy Technology Data Exchange (ETDEWEB)
Mitridate, Andrea [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126, Pisa (Italy); Redi, Michele; Smirnov, Juri [INFN, Sezione di Firenze, and Dipartimento di Fisica e Astronomia, Università di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino (Italy); Strumia, Alessandro, E-mail: andrea.mitridate@gmail.com, E-mail: michele.redi@fi.infn.it, E-mail: juri.smirnov@mpi-hd.mpg.de, E-mail: alessandro.strumia@cern.ch [Dipartimento di Fisica dell' Università di Pisa and INFN, Pisa (Italy)
2017-05-01
We present generic formulæ for computing how Sommerfeld corrections together with bound-state formation affects the thermal abundance of Dark Matter with non-abelian gauge interactions. We consider DM as a fermion 3plet (wino) or 5plet under SU(2) {sub L} . In the latter case bound states raise to 11.5 TeV the DM mass required to reproduce the cosmological DM abundance and give indirect detection signals such as (for this mass) a dominant γ-line around 70 GeV. Furthermore, we consider DM co-annihilating with a colored particle, such as a squark or a gluino, finding that bound state effects are especially relevant in the latter case.
Higher dimensional strange quark matter solutions in self creation cosmology
Energy Technology Data Exchange (ETDEWEB)
Şen, R., E-mail: ramazansen-1991@hotmail.com [Institute for Natural and Applied Sciences, Çanakkale Onsekiz Mart University, 17020, Çanakkale (Turkey); Aygün, S., E-mail: saygun@comu.edu.tr [Department of Physics, Art and Science Faculty, Çanakkale Onsekiz Mart University, Çanakkale 17020 (Turkey)
2016-03-25
In this study, we have generalized the higher dimensional flat Friedmann-Robertson-Walker (FRW) universe solutions for a cloud of string with perfect fluid attached strange quark matter (SQM) in Self Creation Cosmology (SCC). We have obtained that the cloud of string with perfect fluid does not survive and the string tension density vanishes for this model. However, we get dark energy model for strange quark matter with positive density and negative pressure in self creation cosmology.
Bouncing Cosmologies with Dark Matter and Dark Energy
Directory of Open Access Journals (Sweden)
Yi-Fu Cai
2016-12-01
Full Text Available We review matter bounce scenarios where the matter content is dark matter and dark energy. These cosmologies predict a nearly scale-invariant power spectrum with a slightly red tilt for scalar perturbations and a small tensor-to-scalar ratio. Importantly, these models predict a positive running of the scalar index, contrary to the predictions of the simplest inflationary and ekpyrotic models, and hence, could potentially be falsified by future observations. We also review how bouncing cosmological space-times can arise in theories where either the Einstein equations are modified or where matter fields that violate the null energy condition are included.
Condensate cosmology: Dark energy from dark matter
International Nuclear Information System (INIS)
Bassett, Bruce A.; Parkinson, David; Kunz, Martin; Ungarelli, Carlo
2003-01-01
Imagine a scenario in which the dark energy forms via the condensation of dark matter at some low redshift. The Compton wavelength therefore changes from small to very large at the transition, unlike quintessence or metamorphosis. We study cosmic microwave background (CMB), large scale structure, supernova and radio galaxy constraints on condensation by performing a four parameter likelihood analysis over the Hubble constant and the three parameters associated with Q, the condensate field: Ω Q , w f and z t (energy density and equation of state today, and redshift of transition). Condensation roughly interpolates between ΛCDM (for large z t ) and SCDM (low z t ) and provides a slightly better fit to the data than ΛCDM. We confirm that there is no degeneracy in the CMB between H and z t and discuss the implications of late-time transitions for the Lyman-α forest. Finally we discuss the nonlinear phase of both condensation and metamorphosis, which is much more interesting than in standard quintessence models
Exact non-linear equations for cosmological perturbations
Energy Technology Data Exchange (ETDEWEB)
Gong, Jinn-Ouk [Asia Pacific Center for Theoretical Physics, Pohang 37673 (Korea, Republic of); Hwang, Jai-chan [Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu 41566 (Korea, Republic of); Noh, Hyerim [Korea Astronomy and Space Science Institute, Daejeon 34055 (Korea, Republic of); Wu, David Chan Lon; Yoo, Jaiyul, E-mail: jinn-ouk.gong@apctp.org, E-mail: jchan@knu.ac.kr, E-mail: hr@kasi.re.kr, E-mail: clwu@physik.uzh.ch, E-mail: jyoo@physik.uzh.ch [Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, Universität Zürich, CH-8057 Zürich (Switzerland)
2017-10-01
We present a complete set of exact and fully non-linear equations describing all three types of cosmological perturbations—scalar, vector and tensor perturbations. We derive the equations in a thoroughly gauge-ready manner, so that any spatial and temporal gauge conditions can be employed. The equations are completely general without any physical restriction except that we assume a flat homogeneous and isotropic universe as a background. We also comment briefly on the application of our formulation to the non-expanding Minkowski background.
Dark matter and dark energy a challenge for modern cosmology
Gorini, Vittorio; Moschella, Ugo; Matarrese, Sabino
2011-01-01
This book brings together reviews from leading international authorities on the developments in the study of dark matter and dark energy, as seen from both their cosmological and particle physics side. Studying the physical and astrophysical properties of the dark components of our Universe is a crucial step towards the ultimate goal of unveiling their nature. The work developed from a doctoral school sponsored by the Italian Society of General Relativity and Gravitation. The book starts with a concise introduction to the standard cosmological model, as well as with a presentation of the theory of linear perturbations around a homogeneous and isotropic background. It covers the particle physics and cosmological aspects of dark matter and (dynamical) dark energy, including a discussion of how modified theories of gravity could provide a possible candidate for dark energy. A detailed presentation is also given of the possible ways of testing the theory in terms of cosmic microwave background, galaxy redshift su...
The dark side of cosmology: dark matter and dark energy.
Spergel, David N
2015-03-06
A simple model with only six parameters (the age of the universe, the density of atoms, the density of matter, the amplitude of the initial fluctuations, the scale dependence of this amplitude, and the epoch of first star formation) fits all of our cosmological data . Although simple, this standard model is strange. The model implies that most of the matter in our Galaxy is in the form of "dark matter," a new type of particle not yet detected in the laboratory, and most of the energy in the universe is in the form of "dark energy," energy associated with empty space. Both dark matter and dark energy require extensions to our current understanding of particle physics or point toward a breakdown of general relativity on cosmological scales. Copyright © 2015, American Association for the Advancement of Science.
On the non-linear scale of cosmological perturbation theory
Blas, Diego; Konstandin, Thomas
2013-01-01
We discuss the convergence of cosmological perturbation theory. We prove that the polynomial enhancement of the non-linear corrections expected from the effects of soft modes is absent in equal-time correlators like the power or bispectrum. We first show this at leading order by resumming the most important corrections of soft modes to an arbitrary skeleton of hard fluctuations. We derive the same result in the eikonal approximation, which also allows us to show the absence of enhancement at any order. We complement the proof by an explicit calculation of the power spectrum at two-loop order, and by further numerical checks at higher orders. Using these insights, we argue that the modification of the power spectrum from soft modes corresponds at most to logarithmic corrections. Finally, we discuss the asymptotic behavior in the large and small momentum regimes and identify the expansion parameter pertinent to non-linear corrections.
On the non-linear scale of cosmological perturbation theory
International Nuclear Information System (INIS)
Blas, Diego; Garny, Mathias; Konstandin, Thomas
2013-04-01
We discuss the convergence of cosmological perturbation theory. We prove that the polynomial enhancement of the non-linear corrections expected from the effects of soft modes is absent in equal-time correlators like the power or bispectrum. We first show this at leading order by resumming the most important corrections of soft modes to an arbitrary skeleton of hard fluctuations. We derive the same result in the eikonal approximation, which also allows us to show the absence of enhancement at any order. We complement the proof by an explicit calculation of the power spectrum at two-loop order, and by further numerical checks at higher orders. Using these insights, we argue that the modification of the power spectrum from soft modes corresponds at most to logarithmic corrections. Finally, we discuss the asymptotic behavior in the large and small momentum regimes and identify the expansion parameter pertinent to non-linear corrections.
On the non-linear scale of cosmological perturbation theory
Energy Technology Data Exchange (ETDEWEB)
Blas, Diego [European Organization for Nuclear Research (CERN), Geneva (Switzerland); Garny, Mathias; Konstandin, Thomas [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2013-04-15
We discuss the convergence of cosmological perturbation theory. We prove that the polynomial enhancement of the non-linear corrections expected from the effects of soft modes is absent in equal-time correlators like the power or bispectrum. We first show this at leading order by resumming the most important corrections of soft modes to an arbitrary skeleton of hard fluctuations. We derive the same result in the eikonal approximation, which also allows us to show the absence of enhancement at any order. We complement the proof by an explicit calculation of the power spectrum at two-loop order, and by further numerical checks at higher orders. Using these insights, we argue that the modification of the power spectrum from soft modes corresponds at most to logarithmic corrections. Finally, we discuss the asymptotic behavior in the large and small momentum regimes and identify the expansion parameter pertinent to non-linear corrections.
Non-gaussianity versus nonlinearity of cosmological perturbations.
Verde, L
2001-06-01
Following the discovery of the cosmic microwave background, the hot big-bang model has become the standard cosmological model. In this theory, small primordial fluctuations are subsequently amplified by gravity to form the large-scale structure seen today. Different theories for unified models of particle physics, lead to different predictions for the statistical properties of the primordial fluctuations, that can be divided in two classes: gaussian and non-gaussian. Convincing evidence against or for gaussian initial conditions would rule out many scenarios and point us toward a physical theory for the origin of structures. The statistical distribution of cosmological perturbations, as we observe them, can deviate from the gaussian distribution in several different ways. Even if perturbations start off gaussian, nonlinear gravitational evolution can introduce non-gaussian features. Additionally, our knowledge of the Universe comes principally from the study of luminous material such as galaxies, but galaxies might not be faithful tracers of the underlying mass distribution. The relationship between fluctuations in the mass and in the galaxies distribution (bias), is often assumed to be local, but could well be nonlinear. Moreover, galaxy catalogues use the redshift as third spatial coordinate: the resulting redshift-space map of the galaxy distribution is nonlinearly distorted by peculiar velocities. Nonlinear gravitational evolution, biasing, and redshift-space distortion introduce non-gaussianity, even in an initially gaussian fluctuation field. I investigate the statistical tools that allow us, in principle, to disentangle the above different effects, and the observational datasets we require to do so in practice.
Sterile neutrino, hidden dark matter and their cosmological signatures
International Nuclear Information System (INIS)
Das, Subinoy
2012-01-01
Though thermal dark matter has been the central idea behind the dark matter candidates, it is highly possible that dark matter of the universe is non-thermal in origin or it might be in thermal contact with some hidden or dark sector but not with standard model. Here we explore the cosmological bounds as well as the signatures on two types of non-thermal dark matter candidates. First we discuss a hidden dark matter with almost no interaction (or very feeble) with standard model particles so that it is not in thermal contact with visible sector but we assume it is thermalized with in a hidden sector due to some interaction. While encompassing the standard cold WIMP scenario, we do not require the freeze-out process to be non-relativistic. Rather, freeze-out may also occur when dark matter particles are semi-relativistic or relativistic. Especially we focus on the warm dark matter scenario in this set up and find the constraints on the warm dark matter mass, cross-section and hidden to visible sector temperature ratio which accounts for the observed dark-matter density, satisfies the Tremaine-Gunn bound on dark-matter phase space density and has a free-streaming length consistent with cosmological constraints on the matter power spectrum. Our method can also be applied to keV sterile neutrino dark matter which is not thermalized with standard model but is thermalized with in a dark sector. The second part of this proceeding focuses on an exotic dark matter candidate which arises from the existence of eV mass sterile neutrino through a late phase transition. Due to existence of a strong scalar force the light sterile states get trapped into stable degenerate micro nuggets. We find that its signature in matter power spectra is close to a warm dark matter candidate.
Light higgsino dark matter from non-thermal cosmology
Energy Technology Data Exchange (ETDEWEB)
Aparicio, Luis [ICTP,Strada Costiera 11, Trieste 34014 (Italy); Cicoli, Michele [ICTP,Strada Costiera 11, Trieste 34014 (Italy); Dipartimento di Fisica e Astronomia, Università di Bologna,via Irnerio 46, 40126 Bologna (Italy); INFN, Sezione di Bologna,via Irnerio 46, 40126 Bologna (Italy); Dutta, Bhaskar [Department of Physics and Astronomy,Mitchell Institute for Fundamental Physics and Astronomy,TAMU, College Station, TX 77843-4242 (United States); Muia, Francesco [Dipartimento di Fisica e Astronomia, Università di Bologna,via Irnerio 46, 40126 Bologna (Italy); INFN, Sezione di Bologna,via Irnerio 46, 40126 Bologna (Italy); Quevedo, Fernando [ICTP,Strada Costiera 11, Trieste 34014 (Italy); DAMTP, Centre for Mathematical Sciences,Wilberforce Road, Cambridge, CB3 0WA (United Kingdom)
2016-11-08
We study the scenario of higgsino dark matter in the context of a non-standard cosmology with a period of matter domination prior to Big Bang nucleosynthesis. Matter domination changes the dark matter relic abundance if it ends via reheating to a temperature below the higgsino thermal freeze-out temperature. We perform a model independent analysis of the higgsino dark matter production in such scenario. We show that light higgsino-type dark matter is possible for reheating temperatures close to 1 GeV. We study the impact of dark matter indirect detection and collider physics in this context. We show that Fermi-LAT data rule out non-thermal higgsinos with masses below 300 GeV. Future indirect dark matter searches from Fermi-LAT and CTA will be able to cover essentially the full parameter space. Contrary to the thermal case, collider signals from a 100 TeV collider could fully test the non-thermal higgsino scenario. In the second part of the paper we discuss the motivation of such non-thermal cosmology from the perspective of string theory with late-time decaying moduli for both KKLT and LVS moduli stabilisation mechanisms. We finally describe the impact of embedding higgsino dark matter in these scenarios.
Gravitino/axino as decaying dark matter and cosmological tensions
Directory of Open Access Journals (Sweden)
Koichi Hamaguchi
2017-09-01
Full Text Available In supersymmetric axion models, if the gravitino or axino is the lightest SUSY particle (LSP, the other is often the next-to-LSP (NLSP. We investigate the cosmology of such a scenario and point out that the lifetime of the NLSP naturally becomes comparable to the present age of the universe in a viable parameter region. This is a well-motivated example of the so-called decaying dark matter model, which is recently considered as an extension of the ΛCDM model to relax some cosmological tensions.
Some problems of quantum cosmology and dark matter physics
Wang, Jin
The quantum cosmology is studied of the string universe obtained by embedding the Robertson-Walker metric in the nonlinear sigma model. It was found that initially the universe exists in a series of metastable bound states with the scale factor taking discrete values. Then it tunnels through a barrier and comes out in an inflationary state. This tunneling (or evolution in imaginary time) also has the effect of heating up the matter field so that we have a condition of chaotic inflation. The asymptotic solutions agree with those obtained from the classical Einstein equations. Quantum cosmology was considered of a 4-D universe using the effective action of superstrings. Both Hartle-Hawking and Vilenkin boundary conditions were applied to the solution of Wheeler-DeWitt equation. Under certain conditions (fermions added) the universe was found to tunnel through to the Lorentzian regime from the Euclidean regime and time is dynamically generated. Chudnovsky and Vilenkin's idea was applied to possible existence of cosmic strings in the Sun. Stellar evolution with cosmic strings at solar age gives a radius and luminosity of the star which are in contradiction with observation. The astrophysical bound was studied on the change of gravitational constant with time. It was found that (G/G) less than 10-12yr-1 is the condition that has to be satisfied in order not to cause the conflict with observation. The effect was studied of axions on the steller evolution of a 10 solar mass star model. If the axion mass is larger than .1 ev the star's age is significantly different at late stages, compared to the star without axions. It is argued that if cosmions (or WIMPS) solve the solar neutrino problem, then they must also play an important role in the evolution of low mass star main sequence stars. If they do so, then a simple (long mean free path) model for the interaction of cosmions with baryons leads to changes in the structure of the nuclear-burning core which may in principle
Onset of the nonlinear regime in unified dark matter models
International Nuclear Information System (INIS)
Avelino, P.P.; Beca, L.M.G.; Carvalho, J.P.M. de; Martins, C.J.A.P.; Copeland, E.J.
2004-01-01
We discuss the onset of the nonlinear regime in the context of unified dark matter models involving a generalized Chaplygin gas. We show that the transition from dark-matter-like to dark-energy-like behavior will never be smooth. In some regions of space the transition will never take place while in others it may happen sooner or later than naively expected. As a result the linear theory used in previous studies may break down late in the matter dominated era even on large cosmological scales. We study the importance of this effect showing that its magnitude depends on the exact form of the equation of state in the low density regime. We expect that our results will be relevant for other unified dark matter scenarios, particularly those where the quartessence candidate is a perfect fluid
Simulating nonlinear cosmological structure formation with massive neutrinos
Energy Technology Data Exchange (ETDEWEB)
Banerjee, Arka; Dalal, Neal, E-mail: abanerj6@illinois.edu, E-mail: dalaln@illinois.edu [Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, IL 61801-3080 (United States)
2016-11-01
We present a new method for simulating cosmologies that contain massive particles with thermal free streaming motion, such as massive neutrinos or warm/hot dark matter. This method combines particle and fluid descriptions of the thermal species to eliminate the shot noise known to plague conventional N-body simulations. We describe this method in detail, along with results for a number of test cases to validate our method, and check its range of applicability. Using this method, we demonstrate that massive neutrinos can produce a significant scale-dependence in the large-scale biasing of deep voids in the matter field. We show that this scale-dependence may be quantitatively understood using an extremely simple spherical expansion model which reproduces the behavior of the void bias for different neutrino parameters.
Simulating nonlinear cosmological structure formation with massive neutrinos
International Nuclear Information System (INIS)
Banerjee, Arka; Dalal, Neal
2016-01-01
We present a new method for simulating cosmologies that contain massive particles with thermal free streaming motion, such as massive neutrinos or warm/hot dark matter. This method combines particle and fluid descriptions of the thermal species to eliminate the shot noise known to plague conventional N-body simulations. We describe this method in detail, along with results for a number of test cases to validate our method, and check its range of applicability. Using this method, we demonstrate that massive neutrinos can produce a significant scale-dependence in the large-scale biasing of deep voids in the matter field. We show that this scale-dependence may be quantitatively understood using an extremely simple spherical expansion model which reproduces the behavior of the void bias for different neutrino parameters.
Vittorio, Nicola
2018-01-01
Modern cosmology has changed significantly over the years, from the discovery to the precision measurement era. The data now available provide a wealth of information, mostly consistent with a model where dark matter and dark energy are in a rough proportion of 3:7. The time is right for a fresh new textbook which captures the state-of-the art in cosmology. Written by one of the world's leading cosmologists, this brand new, thoroughly class-tested textbook provides graduate and undergraduate students with coverage of the very latest developments and experimental results in the field. Prof. Nicola Vittorio shows what is meant by precision cosmology, from both theoretical and observational perspectives.
Anisotropic Bianchi II cosmological models with matter and electromagnetic fields
International Nuclear Information System (INIS)
Soares, D.
1978-01-01
A class of solutions of Einstein-Maxwell equations is presented, which corresponds to anisotropic Bianchi II spatially homogeneous cosmological models with perfect fluid and electromagnetic field. A particular model is examined and shown to be unstable for perturbations of the electromagnetic field strength parameter about a particular value. This value defines a limiar unstable case in which the ratio epsilon, of the fluid density to the e.m. energy density is monotonically increasing with a minimum finite value at the singularity. Beyond this limiar, the model has a matter dominated singularity, and a characteristic stage appears where epsilon has a minimum, at a finite time from the singularity. For large times, the models tend to an exact solution for zero electromagnetic field and fluid with p = (1/5)p. Some cosmological features of the models are calculated, as the effect of anisotropy on matter density and expansion time scale factors, as compared to the corresponding Friedmann model [pt
Rippled cosmological dark matter from a damped oscillating Newton constant
International Nuclear Information System (INIS)
Davidson, Aharon
2005-01-01
Let the reciprocal Newton 'constant' be an apparently non-dynamical Brans-Dicke scalar field damped oscillating towards its general relativistic VEV. We show, without introducing additional matter fields or dust, that the corresponding cosmological evolution averagely resembles, in the Jordan frame, the familiar dark radiation → dark matter → dark energy domination sequence. The fingerprints of our theory are fine ripples, hopefully testable, in the FRW scale factor; they die away at the general relativity limit. The possibility that the Brans-Dicke scalar also serves as the inflaton is favourably examined
Nuclear matter as a nonlinear optical medium
International Nuclear Information System (INIS)
Hefter, E.F.; Papini, G.
1986-01-01
This paper is concerned with the question whether nuclear matter should be considered as a nonlinear optical medium. Taking, in a pragmatic way, quality and quantity of the results of well-established linear and nonlinear approaches as the main criterion, an affirmative answer is seen to be consistent with long-standing practices adhered to in nuclear physics
Universal subhalo accretion in cold and warm dark matter cosmologies
Kubik, Bogna; Libeskind, Noam I.; Knebe, Alexander; Courtois, Hélène; Yepes, Gustavo; Gottlöber, Stefan; Hoffman, Yehuda
2017-12-01
The influence of the large-scale structure on host haloes may be studied by examining the angular infall pattern of subhaloes. In particular, since warm dark matter (WDM) and cold dark matter (CDM) cosmologies predict different abundances and internal properties for haloes at the low-mass end of the mass function, it is interesting to examine if there are differences in how these low-mass haloes are accreted. The accretion events are defined as the moment a halo becomes a substructure, namely when it crosses its host's virial radius. We quantify the cosmic web at each point by the shear tensor and examine where, with respect to its eigenvectors, such accretion events occur in ΛCDM and ΛWDM (1 keV sterile neutrino) cosmological models. We find that the CDM and WDM subhaloes are preferentially accreted along the principal axis of the shear tensor corresponding to the direction of weakest collapse. The beaming strength is modulated by the host and subhalo masses and by the redshift at which the accretion event occurs. Although strongest for the most massive hosts and subhaloes at high redshift, the preferential infall is found to be always aligned with the axis of weakest collapse, thus we say that it has universal nature. We compare the strength of beaming in the ΛWDM cosmology with the one found in the ΛCDM scenario. While the main findings remain the same, the accretion in the ΛWDM model for the most massive host haloes appears more beamed than in ΛCDM cosmology across all the redshifts.
The most general cosmological dynamics for ELKO matter fields
International Nuclear Information System (INIS)
Fabbri, Luca
2011-01-01
Not long ago, the definition of eigenspinors of charge-conjugation belonging to a special Wigner class has lead to the unexpected theoretical discovery of a form of matter with spin 1/2 and mass dimension 1, called ELKO matter field; ELKO matter fields defined in flat spacetimes have been later extended to curved and twisted spacetimes, in order to include in their dynamics the coupling to gravitational fields possessing both metric and torsional degrees of freedom: the inclusion of non-commuting spinorial covariant derivatives allows for the introduction of more general dynamical terms influencing the behaviour of ELKO matter fields. In this Letter, we shall solve the theoretical problem of finding the most general dynamics for ELKO matter, and we will face the phenomenological issue concerning how the new dynamical terms may affect the behavior of ELKO matter; we will see that new effects will arise for which the very existence of ELKO matter will be endangered, due to the fact that ELKOs will turn incompatible with the cosmological principle. Thus we have that anisotropic universes must be taken into account if ELKOs are to be considered in their most general form.
Evidence for dark matter interactions in cosmological precision data?
International Nuclear Information System (INIS)
Lesgourgues, Julien; Marques-Tavares, Gustavo; Schmaltz, Martin
2016-01-01
We study a two-parameter extension of the cosmological standard model ΛCDM in which cold dark matter interacts with a new form of dark radiation. The two parameters correspond to the energy density in the dark radiation fluid ΔN fluid and the interaction strength between dark matter and dark radiation. The interactions give rise to a very weak ''dark matter drag'' which damps the growth of matter density perturbations throughout radiation domination, allowing to reconcile the tension between predictions of large scale structure from the CMB and direct measurements of σ 8 . We perform a precision fit to Planck CMB data, BAO, large scale structure, and direct measurements of the expansion rate of the universe today. Our model lowers the χ-squared relative to ΛCDM by about 12, corresponding to a preference for non-zero dark matter drag by more than 3σ. Particle physics models which naturally produce a dark matter drag of the required form include the recently proposed non-Abelian dark matter model in which the dark radiation corresponds to massless dark gluons
The matter-ekpyrotic bounce scenario in Loop Quantum Cosmology
Energy Technology Data Exchange (ETDEWEB)
Haro, Jaume; Amorós, Jaume; Saló, Llibert Aresté, E-mail: jaime.haro@upc.edu, E-mail: jaume.amoros@upc.edu, E-mail: llibert.areste@estudiant.upc.edu [Departament de Matemàtica Aplicada, Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain)
2017-09-01
We will perform a detailed study of the matter-ekpyrotic bouncing scenario in Loop Quantum Cosmology using the methods of the dynamical systems theory. We will show that when the background is driven by a single scalar field, at very late times, in the contracting phase, all orbits depict a matter dominated Universe, which evolves to an ekpyrotic phase. After the bounce the Universe enters in the expanding phase, where the orbits leave the ekpyrotic regime going to a kination (also named deflationary) regime. Moreover, this scenario supports the production of heavy massive particles conformally coupled with gravity, which reheats the universe at temperatures compatible with the nucleosynthesis bounds and also the production of massless particles non-conformally coupled with gravity leading to very high reheating temperatures but ensuring the nucleosynthesis success. Dealing with cosmological perturbations, these background dynamics produce a nearly scale invariant power spectrum for the modes that leave the Hubble radius, in the contracting phase, when the Universe is quasi-matter dominated, whose spectral index and corresponding running is compatible with the recent experimental data obtained by PLANCK's team.
The matter-ekpyrotic bounce scenario in Loop Quantum Cosmology
Haro, Jaume; Amorós, Jaume; Aresté Saló, Llibert
2017-09-01
We will perform a detailed study of the matter-ekpyrotic bouncing scenario in Loop Quantum Cosmology using the methods of the dynamical systems theory. We will show that when the background is driven by a single scalar field, at very late times, in the contracting phase, all orbits depict a matter dominated Universe, which evolves to an ekpyrotic phase. After the bounce the Universe enters in the expanding phase, where the orbits leave the ekpyrotic regime going to a kination (also named deflationary) regime. Moreover, this scenario supports the production of heavy massive particles conformally coupled with gravity, which reheats the universe at temperatures compatible with the nucleosynthesis bounds and also the production of massless particles non-conformally coupled with gravity leading to very high reheating temperatures but ensuring the nucleosynthesis success. Dealing with cosmological perturbations, these background dynamics produce a nearly scale invariant power spectrum for the modes that leave the Hubble radius, in the contracting phase, when the Universe is quasi-matter dominated, whose spectral index and corresponding running is compatible with the recent experimental data obtained by PLANCK's team.
Classification of cosmology with arbitrary matter in the Horava-Lifshitz model
International Nuclear Information System (INIS)
Minamitsuji, Masato
2010-01-01
In this work, we discuss the cosmological evolutions in the nonrelativistic and possibly renormalizable gravitational theory, called the Horava-Lifshitz (HL) theory. We consider the original HL model (type I), and the modified version obtained by an analytic continuation of parameters (type II). We classify the possible cosmological evolutions with arbitrary matter. We will find a variety of cosmology.
Homogeneous and isotropic cosmologies with nonlinear electromagnetic radiation
International Nuclear Information System (INIS)
Vollick, Dan N.
2008-01-01
In this paper I examine cosmological models that contain a stochastic background of nonlinear electromagnetic radiation. I show that for Born-Infeld electrodynamics the equation of state parameter, w=P/ρ, remains close to 1/3 throughout the evolution of the universe if E 2 =B 2 in the late universe to a high degree of accuracy. Theories with electromagnetic Lagrangians of the form L=-(1/4)F 2 +αF 4 have recently been studied in magnetic universes, where the electric field vanishes. It was shown that the F 4 term can produce a bounce in the early universe, avoiding an initial singularity. Here I show that the inclusion of an electric field, with E 2 ≅B 2 in the late universe, eliminates the bounce and the universe begins with an initial singularity. I also examine theories with Lagrangians of the form L=-(1/4)F 2 -μ 8 /F 2 , which have been shown to produce a period of late time accelerated expansion in magnetic universes. I show that, if an electric field is introduced, the accelerated phase will only occur if E 2 2 .
Matter couplings in Horava-Lifshitz theories and their cosmological applications
International Nuclear Information System (INIS)
Carloni, Sante; Elizalde, Emilio; Silva, Pedro J
2011-01-01
In this paper, the issue of how to introduce matter in Horava-Lifshitz theories of gravity is addressed. This is a key point in order to complete the proper definition of these theories and, more importantly, to study their possible phenomenological implications. As is well known, in Horava-Lifshitz gravity, the breakdown of Lorentz invariance invalidates the usual notion of minimally coupled matter. Two different approaches to bypass this problem are described here. One is based on a Kaluza-Klein reinterpretation of the 3+1 decomposition of the gravity degrees of freedom, which naturally leads to a definition of a U(1) gauge symmetry and, hence, to a new type of minimal coupling. The other approach relies on a midi-superspace formalism and the subsequent parametrization of the matter stress-energy tensor in terms of deep infrared variables. Using the last option, the phase space of Horava-Lifshitz cosmology in the presence of general matter couplings is studied. It is found, in particular, that the equation of state of the effective matter may be very different from the actual matter one, owing to the nonlinear interactions which exist between matter and gravity.
Smoothing expansion rate data to reconstruct cosmological matter perturbations
Energy Technology Data Exchange (ETDEWEB)
Gonzalez, J.E.; Alcaniz, J.S.; Carvalho, J.C., E-mail: javierernesto@on.br, E-mail: alcaniz@on.br, E-mail: jcarvalho@on.br [Departamento de Astronomia, Observatório Nacional, Rua Gal. José Cristino, 77, Rio de Janeiro, RJ 20921-400 (Brazil)
2017-08-01
The existing degeneracy between different dark energy and modified gravity cosmologies at the background level may be broken by analyzing quantities at the perturbative level. In this work, we apply a non-parametric smoothing (NPS) method to reconstruct the expansion history of the Universe ( H ( z )) from model-independent cosmic chronometers and high- z quasar data. Assuming a homogeneous and isotropic flat universe and general relativity (GR) as the gravity theory, we calculate the non-relativistic matter perturbations in the linear regime using the H ( z ) reconstruction and realistic values of Ω {sub m} {sub 0} and σ{sub 8} from Planck and WMAP-9 collaborations. We find a good agreement between the measurements of the growth rate and f σ{sub 8}( z ) from current large-scale structure observations and the estimates obtained from the reconstruction of the cosmic expansion history. Considering a recently proposed null test for GR using matter perturbations, we also apply the NPS method to reconstruct f σ{sub 8}( z ). For this case, we find a ∼ 3σ tension (good agreement) with the standard relativistic cosmology when the Planck (WMAP-9) priors are used.
Future cosmological sensitivity for hot dark matter axions
Archidiacono, Maria; Hamann, Jan; Hannestad, Steen; Raffelt, Georg; Wong, Yvonne Y Y
2015-01-01
We study the potential of a future, large-volume photometric survey to constrain the axion mass $m_a$ in the hot dark matter limit. Future surveys such as Euclid will have significantly more constraining power than current observations for hot dark matter. Nonetheless, the lowest accessible axion masses are limited by the fact that axions lighter than $\\sim 0.15$ eV decouple before the QCD epoch, assumed here to occur at a temperature $T_{\\rm QCD} \\sim 170$ MeV; this leaves an axion population of such low density that its late-time cosmological impact is negligible. For larger axion masses, $m_a \\gtrsim 0.15$ eV, where axions remain in equilibrium until after the QCD phase transition, we find that a Euclid-like survey combined with Planck CMB data can detect $m_a$ at very high significance. Our conclusions are robust against assumptions about prior knowledge of the neutrino mass. Given that the proposed IAXO solar axion search is sensitive to $m_a\\lesssim 0.2$ eV, the axion mass range probed by cosmology is n...
Smoothing expansion rate data to reconstruct cosmological matter perturbations
International Nuclear Information System (INIS)
Gonzalez, J.E.; Alcaniz, J.S.; Carvalho, J.C.
2017-01-01
The existing degeneracy between different dark energy and modified gravity cosmologies at the background level may be broken by analyzing quantities at the perturbative level. In this work, we apply a non-parametric smoothing (NPS) method to reconstruct the expansion history of the Universe ( H ( z )) from model-independent cosmic chronometers and high- z quasar data. Assuming a homogeneous and isotropic flat universe and general relativity (GR) as the gravity theory, we calculate the non-relativistic matter perturbations in the linear regime using the H ( z ) reconstruction and realistic values of Ω m 0 and σ 8 from Planck and WMAP-9 collaborations. We find a good agreement between the measurements of the growth rate and f σ 8 ( z ) from current large-scale structure observations and the estimates obtained from the reconstruction of the cosmic expansion history. Considering a recently proposed null test for GR using matter perturbations, we also apply the NPS method to reconstruct f σ 8 ( z ). For this case, we find a ∼ 3σ tension (good agreement) with the standard relativistic cosmology when the Planck (WMAP-9) priors are used.
FRW-type cosmologies with adiabatic matter creation
International Nuclear Information System (INIS)
Lima, J.A.; Germano, A.S.; Abramo, L.R.
1996-01-01
Some properties of cosmological models with matter creation are investigated in the framework of the Friedmann-Robertson-Walker line element. For adiabatic matter creation, as developed by Prigogine and co-workers, we derive a simple expression relating the particle number density n and energy density ρ which holds regardless of the matter creation rate. The conditions to generate inflation are discussed and by considering the natural phenomenological matter creation rate ψ=3βnH, where β is a pure number of the order of unity and H is the Hubble parameter, a minimally modified hot big-bang model is proposed. The dynamic properties of such models can be deduced from the standard ones simply by replacing the adiabatic index γ of the equation of state by an effective parameter γ * =γ(1-β). The thermodynamic behavior is determined and it is also shown that ages large enough to agree with observations are obtained even given the high values of H suggested by recent measurements. copyright 1996 The American Physical Society
Cosmological constraints on the gravitational interactions of matter and dark matter
International Nuclear Information System (INIS)
Bai, Yang; Salvado, Jordi; Stefanek, Ben A.
2015-01-01
Although there is overwhelming evidence of dark matter from its gravitational interaction, we still do not know its precise gravitational interaction strength or whether it obeys the equivalence principle. Using the latest available cosmological data and working within the framework of ΛCDM, we first update the measurement of the multiplicative factor of cosmology-relevant Newton’s constant over the standard laboratory-based value and find that it is consistent with one. In general relativity, dark matter equivalence principle breaking can be mimicked by a long-range dark matter force mediated by an ultra light scalar field. Using the Planck three year data, we find that the dark matter “fifth-force” strength is constrained to be weaker than 10 −4 of the gravitational force. We also introduce a phenomenological, post-Newtonian two-fluid description to explicitly break the equivalence principle by introducing a difference between dark matter inertial and gravitational masses. Depending on the decoupling time of the dark matter and ordinary matter fluids, the ratio of the dark matter gravitational mass to inertial mass is constrained to be unity at the 10 −6 level
Nonlinear viscosity in brane-world cosmology with a Gauss–Bonnet term
Debnath, P. S.; Beesham, A.; Paul, B. C.
2018-06-01
Cosmological solutions are obtained with nonlinear bulk viscous cosmological fluid in the Randall–Sundrum type II (RS) brane-world model with or without Gauss–Bonnet (GB) terms. To describe such a viscous fluid, we consider the nonlinear transport equation which may be used far from equilibrium during inflation or reheating. Cosmological models are explored for both (i) power law and (ii) exponential evolution of the early universe in the presence of an imperfect fluid described by the non-linear Israel and Stewart theory (nIS). We obtain analytic solutions and the complex field equations are also analyzed numerically to study the evolution of the universe. The stability analysis of the equilibrium points of the dynamical system associated with the evolution of the nonlinear bulk viscous fluid in the RS Brane in the presence (or absence) of a GB term are also studied.
Anomaly mediated SUSY breaking scenarios in the light of cosmology and in the dark (matter)
Arbey, A; Tarhini, A
2011-01-01
Anomaly mediation is a popular and well motivated supersymmetry breaking scenario. Different possible detailed realisations of this set-up are studied and actively searched for at colliders. Apart from limits coming from flavour, low energy physics and direct collider searches, these models are usually constrained by the requirement of reproducing the observations on dark matter density in the universe. We reanalyse these bounds and in particular we focus on the dark matter bounds both considering the standard cosmological model and alternative cosmological scenarios. These scenarios do not change the observable cosmology but relic dark matter density bounds strongly depend on them. We consider few benchmark points excluded by standard cosmology dark matter bounds and suggest that loosening the dark matter constraints is necessary in order to avoid a too strong (cosmological) model dependence in the limits that are obtained for these models. We also discuss briefly the implications for phenomenology and in pa...
Cosmological tests on Visser's massive graviton dark matter cosmology
Energy Technology Data Exchange (ETDEWEB)
Hu, Xin-Yun; Liu, Xian-Ming [Hubei University for Nationalities, Department of Physics, Enshi, Hubei (China); Zeng, Xiao-Xiong [Chongqing Jiaotong University, School of Science, Nanan (China)
2013-06-15
We present the constraints on the Massive Graviton Dark Matter scenario (MGCDM) using the cosmological observations, including type Ia supernovae (SNe Ia), Gamma Ray Bursts (GRB), Observational Hubble Parameter Data (OHD), Cosmic Microwave Background shift parameter, and the Radial Baryon Acoustic Oscillation. In order to compare the goodness of the data samples and their combinations, we adopt the Fisher matrix analysis and the figure of merit (FoM) diagnostic. Based on the constraint results, we further discuss the cosmic age problem in MGCDM. The calculation shows that the universe in MGCDM frame is older than that in standard {Lambda}CDM model, but the cosmic age crisis is still unresolved with just an alleviation. (orig.)
Light neutrinos as cosmological dark matter and the next supernova
International Nuclear Information System (INIS)
Minakata, H.; Nunokawa, H.
1990-01-01
We point out that the light-neutrino hypothesis for cosmological dark matter can be tested by observing a neutrino burst from a type-II supernova. With the luck of a nearby (∼10 kpc) event watched by enlarged water Cherenkov detectors, such as the proposed super-Kamiokande, it might be possible to measure the tau- (heaviest-)neutrino mass. In such a case the statistically significant (4000--6000) bar ν e absorption events would allow the precise determination of the neutrino flux and the temperature. By using a simple model of neutrino emission based on the simulation by Mayle, Wilson, and Schramm, we show that the existence of the neutrino mixing can be signaled by 20--30 % excess of the scattering events in the water Cherenkov detector, and by factor ∼3 larger rate in Davis's 37 Cl detector. The effect on the recoil electron energy spectrum is also analyzed
Gravitational, shear and matter waves in Kantowski-Sachs cosmologies
Energy Technology Data Exchange (ETDEWEB)
Keresztes, Zoltán; Gergely, László Á. [Department of Theoretical Physics, University of Szeged, Tisza Lajos krt 84-86, Szeged 6720 (Hungary); Forsberg, Mats; Bradley, Michael [Department of Physics, UmeåUniversity (Sweden); Dunsby, Peter K.S., E-mail: zkeresztes@titan.physx.u-szeged.hu, E-mail: forsberg.mats.a.b@gmail.com, E-mail: michael.bradley@physics.umu.se, E-mail: peter.dunsby@uct.ac.za, E-mail: gergely@physx.u-szeged.hu [Astrophysics, Cosmology and Gravity Centre (ACGC), University of Cape Town, Rondebosch 7701, Cape Town (South Africa)
2015-11-01
A general treatment of vorticity-free, perfect fluid perturbations of Kantowski-Sachs models with a positive cosmological constant are considered within the framework of the 1+1+2 covariant decomposition of spacetime. The dynamics is encompassed in six evolution equations for six harmonic coefficients, describing gravito-magnetic, kinematic and matter perturbations, while a set of algebraic expressions determine the rest of the variables. The six equations further decouple into a set of four equations sourced by the perfect fluid, representing forced oscillations and two uncoupled damped oscillator equations. The two gravitational degrees of freedom are represented by pairs of gravito-magnetic perturbations. In contrast with the Friedmann case one of them is coupled to the matter density perturbations, becoming decoupled only in the geometrical optics limit. In this approximation, the even and odd tensorial perturbations of the Weyl tensor evolve as gravitational waves on the anisotropic Kantowski-Sachs background, while the modes describing the shear and the matter density gradient are out of phase dephased by π /2 and share the same speed of sound.
Cosmological axion and a quark nugget dark matter model
Ge, Shuailiang; Liang, Xunyu; Zhitnitsky, Ariel
2018-02-01
We study a dark matter (DM) model offering a very natural explanation of two (naively unrelated) problems in cosmology: the observed relation ΩDM˜Ωvisible and the observed asymmetry between matter and antimatter in the Universe, known as the "baryogenesis" problem. In this framework, both types of matter (dark and visible) have the same QCD origin, form at the same QCD epoch, and are proportional to one and the same dimensional parameter of the system, ΛQCD, which explains how these two naively distinct problems could be intimately related, and could be solved simultaneously within the same framework. More specifically, the DM in this model is composed by two different ingredients: the (well-studied) DM axions and the (less-studied) quark nuggets made of matter or antimatter. We focus on the quantitative analysis of the relation between these two distinct components contributing to the dark sector of the theory determined by ΩDM≡[ΩDM(nuggets)+ΩDM(axion)] . We argue that the nuggets' DM component always traces the visible matter density, i.e., ΩDM(nuggets)˜Ωvisible , and this feature is not sensitive to the parameters of the system such as the axion mass ma or the misalignment angle θ0. It should be contrasted with conventional axion production mechanisms due to the misalignment when ΩDM(axion) is highly sensitive to the axion mass ma and the initial misalignment angle θ0. We also discuss the constraints on this model related to the inflationary scale HI, nonobservation of the isocurvature perturbations and the tensor modes. We also comment on some constraints related to various axion search experiments.
Cen, R. Y.; Ostriker, J. P.; Spergel, D. N.; Turok, N.
1991-01-01
Hydrodynamical simulations of galaxy formation in a texture-seeded cosmology are presented, with attention given to Omega = 1 galaxies dominated by both hot dark matter (HDM) and cold dark matter (CDM). The simulations include both gravitational and hydrodynamical physics with a detailed treatment of collisional and radiative thermal processes, and use a cooling criterion to estimate galaxy formation. Background radiation fields and Zel'dovich-Sunyaev fluctuations are explicitly computed. The derived galaxy mass function is well fitted by the observed Schechter luminosity function for a baryonic M/L of 3 and total M/L of 60 in galaxies. In both HDM and CDM texture scenarios, the 'galaxies' and 'clusters' are significantly more strongly correlated than the dark matter due to physical bias processes. The slope of the correlation function in both cases is consistent with observations. In contrast to Gaussian models, peaks in the dark matter density distributrion are less correlated than average.
International Nuclear Information System (INIS)
Contopoulos, G.; Kotsakis, D.
1987-01-01
An extensive first part on a wealth of observational results relevant to cosmology lays the foundation for the second and central part of the book; the chapters on general relativity, the various cosmological theories, and the early universe. The authors present in a complete and almost non-mathematical way the ideas and theoretical concepts of modern cosmology including the exciting impact of high-energy particle physics, e.g. in the concept of the ''inflationary universe''. The final part addresses the deeper implications of cosmology, the arrow of time, the universality of physical laws, inflation and causality, and the anthropic principle
arXiv Falsifying cosmological models based on a non-linear electrodynamics
Övgün, Ali; Magaña, Juan; Jusufi, Kimet
Recently, the nonlinear electrodynamics (NED) has been gaining attention to generate primordial magnetic fields in the Universe and also to resolve singularity problems. Moreover, recent works have shown the crucial role of the NED on the inflation. This paper provides a new approach based on a new model of NED as a source of gravitation to remove the cosmic singularity at the big bang and explain the cosmic acceleration during the inflation era on the background of stochastic magnetic field. Also, we found a realization of a cyclic Universe, free of initial singularity, due to the proposed NED energy density. In addition, we explore whether a NED field without or with matter can be the origin of the late-time acceleration. Observations imply that NED cosmologies could not be suitable to explain the Universe late-time dynamics. However, the current data is able to falsify the scenario at late times. Indeed, one is able to reconstruct the deceleration parameter $q(z)$ using the best fit values of the parameter...
Dark clouds in particle physics and cosmology: the issues of dark matter and dark energy
International Nuclear Information System (INIS)
Zhang Xinmin
2011-01-01
Unveiling the nature of dark matter and dark energy is one of the main tasks of particle physics and cosmology in the 21st century. We first present an overview of the history and current status of research in cosmology, at the same time emphasizing the new challenges in particle physics. Then we focus on the scientific issues of dark energy, dark matter and anti-matter, and review the recent progress made in these fields. Finally, we discuss the prospects for future research on the experimental probing of dark matter and dark energy in China. (authors)
Shapiro, Paul R; Mao, Yi; Iliev, Ilian T; Mellema, Garrelt; Datta, Kanan K; Ahn, Kyungjin; Koda, Jun
2013-04-12
The 21 cm background from the epoch of reionization is a promising cosmological probe: line-of-sight velocity fluctuations distort redshift, so brightness fluctuations in Fourier space depend upon angle, which linear theory shows can separate cosmological from astrophysical information. Nonlinear fluctuations in ionization, density, and velocity change this, however. The validity and accuracy of the separation scheme are tested here for the first time, by detailed reionization simulations. The scheme works reasonably well early in reionization (≲40% ionized), but not late (≳80% ionized).
AX-GADGET: a new code for cosmological simulations of Fuzzy Dark Matter and Axion models
Nori, Matteo; Baldi, Marco
2018-05-01
We present a new module of the parallel N-Body code P-GADGET3 for cosmological simulations of light bosonic non-thermal dark matter, often referred as Fuzzy Dark Matter (FDM). The dynamics of the FDM features a highly non-linear Quantum Potential (QP) that suppresses the growth of structures at small scales. Most of the previous attempts of FDM simulations either evolved suppressed initial conditions, completely neglecting the dynamical effects of QP throughout cosmic evolution, or resorted to numerically challenging full-wave solvers. The code provides an interesting alternative, following the FDM evolution without impairing the overall performance. This is done by computing the QP acceleration through the Smoothed Particle Hydrodynamics (SPH) routines, with improved schemes to ensure precise and stable derivatives. As an extension of the P-GADGET3 code, it inherits all the additional physics modules implemented up to date, opening a wide range of possibilities to constrain FDM models and explore its degeneracies with other physical phenomena. Simulations are compared with analytical predictions and results of other codes, validating the QP as a crucial player in structure formation at small scales.
García-Bellido, J
2015-01-01
In these lectures I review the present status of the so-called Standard Cosmological Model, based on the hot Big Bang Theory and the Inflationary Paradigm. I will make special emphasis on the recent developments in observational cosmology, mainly the acceleration of the universe, the precise measurements of the microwave background anisotropies, and the formation of structure like galaxies and clusters of galaxies from tiny primordial fluctuations generated during inflation.
Statistics of peaks in cosmological nonlinear density fields
International Nuclear Information System (INIS)
Suginohara, Tatsushi; Suto, Yasushi.
1990-06-01
Distribution of the high-density peaks in the universe is examined using N-body simulations. Nonlinear evolution of the underlying density field significantly changes the statistical properties of the peaks, compared with the analytic results valid for the random Gaussian field. In particular, the abundances and correlations of the initial density peaks are discussed in the context of biased galaxy formation theory. (author)
Cosmological anisotropy from non-comoving dark matter and dark energy
International Nuclear Information System (INIS)
Harko, Tiberiu; Lobo, Francisco S. N.
2013-01-01
We consider a cosmological model in which the two major fluid components of the Universe, dark energy and dark matter, flow with distinct four-velocities. This cosmological configuration is equivalent to a single anisotropic fluid, expanding with a four-velocity that is an appropriate combination of the two fluid four-velocities. The energy density of the single cosmological fluid is larger than the sum of the energy densities of the two perfect fluids, i.e., dark energy and dark matter, respectively, and contains a correction term due to the anisotropy generated by the differences in the four-velocities. Furthermore, the gravitational field equations of the two-fluid anisotropic cosmological model are obtained for a Bianchi type I geometry. By assuming that the non-comoving motion of the dark energy and dark matter induces small perturbations in the homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker type cosmological background, and that the anisotropy parameter is small, the equations of the cosmological perturbations due to the non-comoving nature of the two major components are obtained. The time evolution of the metric perturbations is explicitly obtained for the cases of the exponential and power law background cosmological expansion. The imprints of a non-comoving dark energy - dark matter on the Cosmic Microwave Background and on the luminosity distance are briefly discussed, and the temperature anisotropies and the quadrupole are explicitly obtained in terms of the metric perturbations of the flat background metric. Therefore, if there is a slight difference between the four-velocities of the dark energy and dark matter, the Universe would acquire some anisotropic characteristics, and its geometry will deviate from the standard FLRW one. In fact, the recent Planck results show that the presence of an intrinsic large scale anisotropy in the Universe cannot be excluded a priori, so that the model presented in this work can be considered as a
Asymmetric dark matter annihilation as a test of non-standard cosmologies
International Nuclear Information System (INIS)
Gelmini, Graciela B.; Huh, Ji-Haeng; Rehagen, Thomas
2013-01-01
We show that the relic abundance of the minority component of asymmetric dark matter can be very sensitive to the expansion rate of the Universe and the temperature of transition between a non-standard pre-Big Bang Nucleosynthesis cosmological phase and the standard radiation dominated phase, if chemical decoupling happens before this transition. In particular, because the annihilation cross section of asymmetric dark matter is typically larger than that of symmetric dark matter in the standard cosmology, the decrease in relic density of the minority component in non-standard cosmologies with respect to the majority component may be compensated by the increase in annihilation cross section, so that the annihilation rate at present of asymmetric dark matter, contrary to general belief, could be larger than that of symmetric dark matter in the standard cosmology. Thus, if the annihilation cross section of the asymmetric dark matter candidate is known, the annihilation rate at present, if detectable, could be used to test the Universe before Big Bang Nucleosynthesis, an epoch from which we do not yet have any data
Testing approximate predictions of displacements of cosmological dark matter halos
Energy Technology Data Exchange (ETDEWEB)
Munari, Emiliano; Monaco, Pierluigi; Borgani, Stefano [Department of Physics, Astronomy Unit, University of Trieste, via Tiepolo 11, I-34143 Trieste (Italy); Koda, Jun [INAF – Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807 Merate (Italy); Kitaura, Francisco-Shu [Instituto de Astrofísica de Canarias, 38205 San Cristóbal de La Laguna, Santa Cruz de Tenerife (Spain); Sefusatti, Emiliano, E-mail: munari@oats.inaf.it, E-mail: monaco@oats.inaf.it, E-mail: jun.koda@brera.inaf.it, E-mail: fkitaura@iac.es, E-mail: sefusatti@oats.inaf.it, E-mail: borgani@oats.inaf.it [INAF – Osservatorio Astronomico di Trieste, via Tiepolo 11, I-34143 Trieste (Italy)
2017-07-01
We present a test to quantify how well some approximate methods, designed to reproduce the mildly non-linear evolution of perturbations, are able to reproduce the clustering of DM halos once the grouping of particles into halos is defined and kept fixed. The following methods have been considered: Lagrangian Perturbation Theory (LPT) up to third order, Truncated LPT, Augmented LPT, MUSCLE and COLA. The test runs as follows: halos are defined by applying a friends-of-friends (FoF) halo finder to the output of an N-body simulation. The approximate methods are then applied to the same initial conditions of the simulation, producing for all particles displacements from their starting position and velocities. The position and velocity of each halo are computed by averaging over the particles that belong to that halo, according to the FoF halo finder. This procedure allows us to perform a well-posed test of how clustering of the matter density and halo density fields are recovered, without asking to the approximate method an accurate reconstruction of halos. We have considered the results at z =0,0.5,1, and we have analysed power spectrum in real and redshift space, object-by-object difference in position and velocity, density Probability Distribution Function (PDF) and its moments, phase difference of Fourier modes. We find that higher LPT orders are generally able to better reproduce the clustering of halos, while little or no improvement is found for the matter density field when going to 2LPT and 3LPT. Augmentation provides some improvement when coupled with 2LPT, while its effect is limited when coupled with 3LPT. Little improvement is brought by MUSCLE with respect to Augmentation. The more expensive particle-mesh code COLA outperforms all LPT methods, and this is true even for mesh sizes as large as the inter-particle distance. This test sets an upper limit on the ability of these methods to reproduce the clustering of halos, for the cases when these objects are
Testing approximate predictions of displacements of cosmological dark matter halos
Munari, Emiliano; Monaco, Pierluigi; Koda, Jun; Kitaura, Francisco-Shu; Sefusatti, Emiliano; Borgani, Stefano
2017-07-01
We present a test to quantify how well some approximate methods, designed to reproduce the mildly non-linear evolution of perturbations, are able to reproduce the clustering of DM halos once the grouping of particles into halos is defined and kept fixed. The following methods have been considered: Lagrangian Perturbation Theory (LPT) up to third order, Truncated LPT, Augmented LPT, MUSCLE and COLA. The test runs as follows: halos are defined by applying a friends-of-friends (FoF) halo finder to the output of an N-body simulation. The approximate methods are then applied to the same initial conditions of the simulation, producing for all particles displacements from their starting position and velocities. The position and velocity of each halo are computed by averaging over the particles that belong to that halo, according to the FoF halo finder. This procedure allows us to perform a well-posed test of how clustering of the matter density and halo density fields are recovered, without asking to the approximate method an accurate reconstruction of halos. We have considered the results at z=0,0.5,1, and we have analysed power spectrum in real and redshift space, object-by-object difference in position and velocity, density Probability Distribution Function (PDF) and its moments, phase difference of Fourier modes. We find that higher LPT orders are generally able to better reproduce the clustering of halos, while little or no improvement is found for the matter density field when going to 2LPT and 3LPT. Augmentation provides some improvement when coupled with 2LPT, while its effect is limited when coupled with 3LPT. Little improvement is brought by MUSCLE with respect to Augmentation. The more expensive particle-mesh code COLA outperforms all LPT methods, and this is true even for mesh sizes as large as the inter-particle distance. This test sets an upper limit on the ability of these methods to reproduce the clustering of halos, for the cases when these objects are
Cosmological perturbations in theories with non-minimal coupling between curvature and matter
International Nuclear Information System (INIS)
Bertolami, Orfeu; Frazão, Pedro; Páramos, Jorge
2013-01-01
In this work, we examine how the presence of a non-minimal coupling between spacetime curvature and matter affects the evolution of cosmological perturbations on a homogeneous and isotropic Universe, and hence the formation of large-scale structure. This framework places constraints on the terms which arise due to the coupling with matter and, in particular, on the modified growth of matter density perturbations. We derive approximate analytical solutions for the evolution of matter overdensities during the matter dominated era and discuss the compatibility of the obtained results with the hypothesis that the late time acceleration of the Universe is driven by a non-minimal coupling
Dark matter as the Bose-Einstein condensation in loop quantum cosmology
International Nuclear Information System (INIS)
Atazadeh, K.; Mousavi, M.; Darabi, F.
2016-01-01
We consider the FLRW universe in a loop quantum cosmological model filled with radiation, baryonic matter (with negligible pressure), dark energy, and dark matter. The dark matter sector is supposed to be of Bose-Einstein condensate type. The Bose-Einstein condensation process in a cosmological context by supposing it as an approximate first-order phase transition, has already been studied in the literature. Here, we study the evolution of the physical quantities related to the early universe description such as the energy density, temperature, and scale factor of the universe, before, during, and after the condensation process. We also consider in detail the evolution era of the universe in a mixed normal-condensate dark matter phase. The behavior and time evolution of the condensate dark matter fraction is also analyzed. (orig.)
Angulo, Raul E.; Hilbert, Stefan
2015-03-01
We explore the cosmological constraints from cosmic shear using a new way of modelling the non-linear matter correlation functions. The new formalism extends the method of Angulo & White, which manipulates outputs of N-body simulations to represent the 3D non-linear mass distribution in different cosmological scenarios. We show that predictions from our approach for shear two-point correlations at 1-300 arcmin separations are accurate at the ˜10 per cent level, even for extreme changes in cosmology. For moderate changes, with target cosmologies similar to that preferred by analyses of recent Planck data, the accuracy is close to ˜5 per cent. We combine this approach with a Monte Carlo Markov chain sampler to explore constraints on a Λ cold dark matter model from the shear correlation functions measured in the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). We obtain constraints on the parameter combination σ8(Ωm/0.27)0.6 = 0.801 ± 0.028. Combined with results from cosmic microwave background data, we obtain marginalized constraints on σ8 = 0.81 ± 0.01 and Ωm = 0.29 ± 0.01. These results are statistically compatible with previous analyses, which supports the validity of our approach. We discuss the advantages of our method and the potential it offers, including a path to model in detail (i) the effects of baryons, (ii) high-order shear correlation functions, and (iii) galaxy-galaxy lensing, among others, in future high-precision cosmological analyses.
EFFECTS OF THE NEUTRINO MASS SPLITTING ON THE NONLINEAR MATTER POWER SPECTRUM
International Nuclear Information System (INIS)
Wagner, Christian; Verde, Licia; Jimenez, Raul
2012-01-01
We have performed cosmological N-body simulations which include the effect of the masses of the individual neutrino species. The simulations were aimed at studying the effect of different neutrino hierarchies on the matter power spectrum. Compared to the linear theory predictions, we find that nonlinearities enhance the effect of hierarchy on the matter power spectrum at mildly nonlinear scales. The maximum difference between the different hierarchies is about 0.5% for a sum of neutrino masses of 0.1 eV. Albeit this is a small effect, it is potentially measurable from upcoming surveys. In combination with neutrinoless double-β decay experiments, this opens up the possibility of using the sky to determine if neutrinos are Majorana or Dirac fermions.
Disappearing dark matter in brane world cosmology: New limits on noncompact extra dimensions
International Nuclear Information System (INIS)
Ichiki, K.; Garnavich, P.M.; Mathews, G.J.; Kajino, T.; Yahiro, M.
2003-01-01
We explore cosmological implications of dark matter as massive particles trapped on a brane embedded in a Randall-Sundrum noncompact higher dimension AdS 5 space. It is an unavoidable consequence of this cosmology that massive particles are metastable and can disappear into the bulk dimension. Here, we show that a massive dark matter particle (e.g. the lightest supersymmetric particle) is likely to have the shortest lifetime for disappearing into the bulk. We examine cosmological constraints on this new paradigm and show that disappearing dark matter is consistent (at the 95% confidence level) with all cosmological constraints, i.e., present observations of type Ia supernovae at the highest redshift, trends in the mass-to-light ratios of galaxy clusters with redshift, the fraction of x-ray emitting gas in rich clusters, and the spectrum of power fluctuations in the cosmic microwave background. A best 2σ concordance region is identified corresponding to a mean lifetime for dark matter disappearance of 15≤Γ -1 ≤80 Gyr. The implication of these results for brane-world physics is discussed
Espinosa, J R; Racco, D; Riotto, A
2018-03-23
For the current central values of the Higgs boson and top quark masses, the standard model Higgs potential develops an instability at a scale of the order of 10^{11} GeV. We show that a cosmological signature of such instability could be dark matter in the form of primordial black holes seeded by Higgs fluctuations during inflation. The existence of dark matter might not require physics beyond the standard model.
Espinosa, J. R.; Racco, D.; Riotto, A.
2018-03-01
For the current central values of the Higgs boson and top quark masses, the standard model Higgs potential develops an instability at a scale of the order of 1 011 GeV . We show that a cosmological signature of such instability could be dark matter in the form of primordial black holes seeded by Higgs fluctuations during inflation. The existence of dark matter might not require physics beyond the standard model.
Baryon symmetric big-bang cosmology. [matter-antimatter symmetry
Stecker, F. W.
1978-01-01
The framework of baryon-symmetric big-bang cosmology offers the greatest potential for deducing the evolution of the universe as a consequence of physical laws and processes with the minimum number of arbitrary assumptions as to initial conditions in the big-bang. In addition, it offers the possibility of explaining the photon-baryon ratio in the universe and how galaxies and galaxy clusters are formed, and also provides the only acceptable explanation at present for the origin of the cosmic gamma ray background radiation.
``All that Matter ... in One Big Bang ...'', &Other Cosmological Singularities
Elizalde, Emilio
2018-02-01
The first part of this paper contains a brief description of the beginnings of modern cosmology, which, the author will argue, was most likely born in the Year 1912. Some of the pieces of evidence presented here have emerged from recent research in the history of science, and are not usually shared with the general audiences in popular science books. In special, the issue of the correct formulation of the original Big Bang concept, according to the precise words of Fred Hoyle, is discussed. Too often, this point is very deficiently explained (when not just misleadingly) in most of the available generalist literature. Other frequent uses of the same words, Big Bang, as to name the initial singularity of the cosmos, and also whole cosmological models, are then addressed, as evolutions of its original meaning. Quantum and inflationary additions to the celebrated singularity theorems by Penrose, Geroch, Hawking and others led to subsequent results by Borde, Guth and Vilenkin. And corresponding corrections to the Einstein field equations have originated, in particular, $R^2$, $f(R)$, and scalar-tensor gravities, giving rise to a plethora of new singularities. For completeness, an updated table with a classification of the same is given.
The Galactic Halo in Mixed Dark Matter Cosmologies
Anderhalden, D.; Diemand, J.; Bertone, G.; Macciò, A.V.; Schneider, A.
2012-01-01
A possible solution to the small scale problems of the cold dark matter (CDM) scenario is that the dark matter consists of two components, a cold and a warm one. We perform a set of high resolution simulations of the Milky Way halo varying the mass of the WDM particle (mWDM) and the cosmic dark
Cosmological radio emission induced by WIMP Dark Matter
International Nuclear Information System (INIS)
Fornengo, N.; Regis, M.; Lineros, R.; Taoso, M.
2012-01-01
We present a detailed analysis of the radio synchrotron emission induced by WIMP dark matter annihilations and decays in extragalactic halos. We compute intensity, angular correlation, and source counts and discuss the impact on the expected signals of dark matter clustering, as well as of other astrophysical uncertainties as magnetic fields and spatial diffusion. Bounds on dark matter microscopic properties are then derived, and, depending on the specific set of assumptions, they are competitive with constraints from other indirect dark matter searches. At GHz frequencies, dark matter sources can become a significant fraction of the total number of sources with brightness below the microJansky level. We show that, at this level of fluxes (which are within the reach of the next-generation radio surveys), properties of the faint edge of differential source counts, as well as angular correlation data, can become an important probe for WIMPs
Cosmological radio emission induced by WIMP Dark Matter
Energy Technology Data Exchange (ETDEWEB)
Fornengo, N.; Regis, M. [Dipartimento di Fisica Teorica, Università di Torino, via P. Giuria 1, I-10125 Torino (Italy); Lineros, R.; Taoso, M., E-mail: fornengo@to.infn.it, E-mail: rlineros@ific.uv.es, E-mail: regis@to.infn.it, E-mail: mtaoso@phas.ubc.ca [IFIC, CSIC-Universidad de Valencia, Ed. Institutos, Apdo. Correos 22085, E-46071 Valencia (Spain)
2012-03-01
We present a detailed analysis of the radio synchrotron emission induced by WIMP dark matter annihilations and decays in extragalactic halos. We compute intensity, angular correlation, and source counts and discuss the impact on the expected signals of dark matter clustering, as well as of other astrophysical uncertainties as magnetic fields and spatial diffusion. Bounds on dark matter microscopic properties are then derived, and, depending on the specific set of assumptions, they are competitive with constraints from other indirect dark matter searches. At GHz frequencies, dark matter sources can become a significant fraction of the total number of sources with brightness below the microJansky level. We show that, at this level of fluxes (which are within the reach of the next-generation radio surveys), properties of the faint edge of differential source counts, as well as angular correlation data, can become an important probe for WIMPs.
Colliders as a simultaneous probe of supersymmetric dark matter and Terascale cosmology
Energy Technology Data Exchange (ETDEWEB)
Barenboim, Gabriela; /Valencia U.; Lykken, Joseph D.; /Fermilab
2006-08-01
Terascale supersymmetry has the potential to provide a natural explanation of the dominant dark matter component of the standard {Lambda}CDM cosmology. However once we impose the constraints on minimal supersymmetry parameters from current particle physics data, a satisfactory dark matter abundance is no longer prima facie natural. This Neutralino Tuning Problem could be a hint of nonstandard cosmology during and/or after the Terascale era. To quantify this possibility, we introduce an alternative cosmological benchmark based upon a simple model of quintessential inflation. This benchmark has no free parameters, so for a given supersymmetry model it allows an unambiguous prediction of the dark matter relic density. As a example, we scan over the parameter space of the CMSSM, comparing the neutralino relic density predictions with the bounds from WMAP. We find that the WMAP-allowed regions of the CMSSM are an order of magnitude larger if we use the alternative cosmological benchmark, as opposed to {Lambda}CDM. Initial results from the CERN Large Hadron Collider will distinguish between the two allowed regions.
Colliders as a simultaneous probe of supersymmetric dark matter and Terascale cosmology
International Nuclear Information System (INIS)
Barenboim, Gabriela; Valencia U.; Lykken, Joseph D.; Fermilab
2006-01-01
Terascale supersymmetry has the potential to provide a natural explanation of the dominant dark matter component of the standard ΛCDM cosmology. However once we impose the constraints on minimal supersymmetry parameters from current particle physics data, a satisfactory dark matter abundance is no longer prima facie natural. This Neutralino Tuning Problem could be a hint of nonstandard cosmology during and/or after the Terascale era. To quantify this possibility, we introduce an alternative cosmological benchmark based upon a simple model of quintessential inflation. This benchmark has no free parameters, so for a given supersymmetry model it allows an unambiguous prediction of the dark matter relic density. As a example, we scan over the parameter space of the CMSSM, comparing the neutralino relic density predictions with the bounds from WMAP. We find that the WMAP-allowed regions of the CMSSM are an order of magnitude larger if we use the alternative cosmological benchmark, as opposed to ΛCDM. Initial results from the CERN Large Hadron Collider will distinguish between the two allowed regions
Colliders as a simultaneous probe of supersymmetric dark matter and Terascale cosmology
Energy Technology Data Exchange (ETDEWEB)
Barenboim, Gabriela [Departament de Fisica Teorica, Universitat de Valencia, Carrer Dr. Moliner 50, E-46100 Burjassot (Valencia) (Spain); Lykken, Joseph D. [Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States)
2006-12-15
Terascale supersymmetry has the potential to provide a natural explanation of the dominant dark matter component of the standard {lambda}CDM cosmology. However once we impose the constraints on minimal supersymmetry parameters from current particle physics data, a satisfactory dark matter abundance is no longer prima facie natural. This Neutralino Tuning Problem could be a hint of nonstandard cosmology during and/or after the Terascale era. To quantify this possibility, we introduce an alternative cosmological benchmark based upon a simple model of quintessential inflation. This benchmark has no free parameters, so for a given supersymmetry model it allows an unambiguous prediction of the dark matter relic density. As a example, we scan over the parameter space of the CMSSM, comparing the neutralino relic density predictions with the bounds from WMAP. We find that the WMAP-allowed regions of the CMSSM are an order of magnitude larger if we use the alternative cosmological benchmark, as opposed to {lambda}CDM. Initial results from the CERN Large Hadron Collider will distinguish between the two allowed regions.
Healthy imperfect dark matter from effective theory of mimetic cosmological perturbations
International Nuclear Information System (INIS)
Hirano, Shin'ichi; Nishi, Sakine; Kobayashi, Tsutomu
2017-01-01
We study the stability of a recently proposed model of scalar-field matter called mimetic dark matter or imperfect dark matter. It has been known that mimetic matter with higher derivative terms suffers from gradient instabilities in scalar perturbations. To seek for an instability-free extension of imperfect dark matter, we develop an effective theory of cosmological perturbations subject to the constraint on the scalar field's kinetic term. This is done by using the unifying framework of general scalar-tensor theories based on the ADM formalism. We demonstrate that it is indeed possible to construct a model of imperfect dark matter which is free from ghost and gradient instabilities. As a side remark, we also show that mimetic F (R) theory is plagued with the Ostrogradsky instability.
Robustness of discrete flows and caustics in cold dark matter cosmology
International Nuclear Information System (INIS)
Natarajan, Aravind; Sikivie, Pierre
2005-01-01
Although a simple argument implies that the distribution of dark matter in galactic halos is characterized by discrete flows and caustics, their presence is often ignored in discussions of galactic dynamics and of dark matter detection strategies. Discrete flows and caustics can in fact be irrelevant if the number of flows is very large. We estimate the number of dark matter flows as a function of galactocentric distance and consider the various ways in which that number can be increased, in particular, by the presence of structure on small scales (dark matter clumps) and the scattering of the flows by inhomogeneities in the matter distribution. We find that, when all complicating factors are taken into account, discrete flows and caustics in galactic halos remain a robust prediction of cold dark matter cosmology with extensive implications for observation and experiment
Healthy imperfect dark matter from effective theory of mimetic cosmological perturbations
Energy Technology Data Exchange (ETDEWEB)
Hirano, Shin' ichi; Nishi, Sakine; Kobayashi, Tsutomu, E-mail: s.hirano@rikkyo.ac.jp, E-mail: sakine@rikkyo.ac.jp, E-mail: tsutomu@rikkyo.ac.jp [Department of Physics, Rikkyo University, Toshima, Tokyo 171-8501 (Japan)
2017-07-01
We study the stability of a recently proposed model of scalar-field matter called mimetic dark matter or imperfect dark matter. It has been known that mimetic matter with higher derivative terms suffers from gradient instabilities in scalar perturbations. To seek for an instability-free extension of imperfect dark matter, we develop an effective theory of cosmological perturbations subject to the constraint on the scalar field's kinetic term. This is done by using the unifying framework of general scalar-tensor theories based on the ADM formalism. We demonstrate that it is indeed possible to construct a model of imperfect dark matter which is free from ghost and gradient instabilities. As a side remark, we also show that mimetic F (R) theory is plagued with the Ostrogradsky instability.
Value of H, space-time patterns, vacuum, matter, expansion of the Universe, alternative cosmologies
Directory of Open Access Journals (Sweden)
Gonzalez-Mestres Luis
2017-01-01
Full Text Available To the experimental uncertainties on the present value H0 of the Lundmark - Lemaître-Hubble constant, fundamental theoretical uncertainties of several kinds should also be added. In standard Cosmology, consistency problems are really serious. The cosmological constant is a source of well-known diffculties while the associated dark energy is assumed to be at the origin of the observed acceleration of the expansion of the Universe. But in alternative cosmologies, possible approaches without these problems exist. An example is the pattern based on the spinorial space-time (SST we introduced in 1996-97 where the H t = 1 relation (t = cosmic time = age of the Universe is automatically generated by a pre-existing cosmic geometry before standard matter and conventional forces, including gravitation and relativity, are introduced. We analyse present theoretical, experimental and observational uncertainties, focusing also on the possible sources of the acceleration of the expansion of the Universe as well as on the structure of the physical vacuum and its potential cosmological role. Particular attention is given to alternative approaches to both Particle Physics and Cosmology including possible preonic constituents of the physical vacuum and associated pre-Big Bang patterns. A significant example is provided by the cosmic SST geometry together with the possibility that the expanding cosmological vacuum releases energy in the form of standard matter and dark matter, thus modifying the dependence of the matter energy density with respect to the age and size of our Universe. The SST naturally generates a new leading contribution to the value of H. If the matter energy density decreases more slowly than in standard patterns, it can naturally be at the origin of the observed acceleration of the expansion of the Universe. The mathematical and dynamical structure of standard Physics at very short distances can also be modified by an underlying preonic
Value of H, space-time patterns, vacuum, matter, expansion of the Universe, alternative cosmologies
Gonzalez-Mestres, Luis
2017-12-01
To the experimental uncertainties on the present value H0 of the Lundmark - Lemaître-Hubble constant, fundamental theoretical uncertainties of several kinds should also be added. In standard Cosmology, consistency problems are really serious. The cosmological constant is a source of well-known diffculties while the associated dark energy is assumed to be at the origin of the observed acceleration of the expansion of the Universe. But in alternative cosmologies, possible approaches without these problems exist. An example is the pattern based on the spinorial space-time (SST) we introduced in 1996-97 where the H t = 1 relation (t = cosmic time = age of the Universe) is automatically generated by a pre-existing cosmic geometry before standard matter and conventional forces, including gravitation and relativity, are introduced. We analyse present theoretical, experimental and observational uncertainties, focusing also on the possible sources of the acceleration of the expansion of the Universe as well as on the structure of the physical vacuum and its potential cosmological role. Particular attention is given to alternative approaches to both Particle Physics and Cosmology including possible preonic constituents of the physical vacuum and associated pre-Big Bang patterns. A significant example is provided by the cosmic SST geometry together with the possibility that the expanding cosmological vacuum releases energy in the form of standard matter and dark matter, thus modifying the dependence of the matter energy density with respect to the age and size of our Universe. The SST naturally generates a new leading contribution to the value of H. If the matter energy density decreases more slowly than in standard patterns, it can naturally be at the origin of the observed acceleration of the expansion of the Universe. The mathematical and dynamical structure of standard Physics at very short distances can also be modified by an underlying preonic structure. If preons are
Is the continuous matter creation cosmology an alternative to ΛCDM?
International Nuclear Information System (INIS)
Fabris, J.C.; Pacheco, J.A. de Freitas; Piattella, O.F.
2014-01-01
The matter creation cosmology is revisited, including the evolution of baryons and dark matter particles. The creation process affects only dark matter and not baryons. The dynamics of the ΛCDM model can be reproduced only if two conditions are satisfied: 1) the entropy density production rate and the particle density variation rate are equal and 2) the (negative) pressure associated to the creation process is constant. However, the matter creation model predicts a present dark matter-to-baryon ratio much larger than that observed in massive X-ray clusters of galaxies, representing a potential difficulty for the model. In the linear regime, a fully relativistic treatment indicates that baryons are not affected by the creation process but this is not the case for dark matter. Both components evolve together at early phases but lately the dark matter density contrast decreases since the background tends to a constant value. This behaviour produces a negative growth factor, in disagreement with observations, being a further problem for this cosmology
A hydrodynamic approach to cosmology: The mixed dark matter cosmological scenario
Cen, Renyue; Ostriker, Jeremiah P.
1994-01-01
We compute the evolution of spatially flat, mixed cold and hot dark matter models containing both baryonic matter and two kinds of dark matter. Hydrodynamics is treated with a highly developed Eulerian hydrodynamic code (see Cen 1992). A standard particle-mesh (PM) code is also used in parallel to calculate the motion of the dark matter components. We adopt the following parameters: h equivalent to (sub 0)/100 km/s Mpc(exp -1) = 0.5, OMEGA(sub C) = 0.3, and OMEGA(sub B) = 0.06, with amplitude of the perturbation spectrum fixed by the Cosmic Background Explorer Satellite (COBE) Dark Matter Radiation (DMR) measurements (Smoot et al. 1992) being sigma (sub 8) = 0.67. Four different boxes are simulated with box sizes of L = (64, 16, 4, 1) h(exp -1) Mpc, respectively, the two small boxes providing good resolution but little valid information due to absence of large-scale power. We use 128(exp 3) approximate 10(exp 6.3) baryonic cells, 128(exp .3) cold dark matter particles, and 2 x 128(exp 3) hot dark matter particles. In addition to the dark matter we follow separately six baryonic species (H, H(+), He, He(+), He(++), e(-)) with allowance for both (nonequilibrium) collisional and radiative ionization in every cell. The background radiation field is also followed in detail with allowance made for both continuum and line processes, to allow nonequilibrium heating and cooling processes to be followed in detail. The mean final Zeldovich-Sunyaev y parameter is estimated to be y Bar = (5.4 + or - 2.7) x 10(exp -7) below currently attainable observations, with a rms fluctuation of approximately delta bar y = (0.6 + or - 3.0) x 10(exp -7) on arcminute scales. The rate of galaxy formation peaks at an even later epoch (z approximate 0.3) than in the standard (OMEGA = 1, sigma sub 8 = 0.67) cold dark matter (CDM) model (z approximate 0.5) and, at a redshift of z = 4, is nearly a factor of 100 lower than for the CDM model with the same value of sigma sub 8. With regard to mass
Global effects of scalar matter production in quantum cosmology
International Nuclear Information System (INIS)
Barvinskij, A.O.; Ponomarev, V.N.
1978-01-01
Within the framework of the geometrodynamical approach global effects of the production of scalar matter filling the closed uniform Friedman Universe are considered. The physical situation is discussed, which corresponds to such a scale of space-time intervals and energies, at which the matter is essentially quantum and the quantized gravitational field is within the quasi-classical limits when its spatial inhomogeneities are small and only global quantum effects are considerable. The only dynamic variable of the gravitational field is the Friedman Universe radius. The main principles of the formalism of the canonical superspace quantization of gravitational and material fields are considered. The method shows the applicability limits of the field theory on the background of classical geometry and leads to the principally new types of interaction
Primordial nucleosynthesis in inhomogeneous cosmologies: Ω = 1 with baryonic dark matter
International Nuclear Information System (INIS)
Mathews, G.J.; Sale, K.E.
1986-09-01
We consider the constraints on Ω from primordial nucleosynthesis in inhomogeneous cosmologies. We find that allowance for isothermal fluctuations significantly weakens the upper bound on the average value of Ω derived from the standard big bang. Under the plausible additional assumption that regions of high baryon density are preferentially absorbed into cold dark matter, the constraints from primordial nucleosynthesis can be satisfied for large values of Ω, including Ω = 1. 22 refs., 2 figs
Quantum cosmology on the worldsheet
International Nuclear Information System (INIS)
Cooper, A.R.; Susskind, L.; Thorlacius, L.
1991-08-01
Two-dimensional quantum gravity coupled to conformally invariant matter central c > 25 provides a toy model for quantum gravity in four dimensions. Two-dimensional quantum cosmology can thus be studied in terms of string theory in background fields. The large scale cosmological constant depends on non-linear dynamics in the string theory target space and does not appear to be suppressed by wormhole effects. 13 refs
Cosmological implications of a dark matter self-interaction energy density
International Nuclear Information System (INIS)
Stiele, Rainer; Boeckel, Tillmann; Schaffner-Bielich, Juergen
2010-01-01
We investigate cosmological constraints on an energy density contribution of elastic dark matter self-interactions characterized by the mass of the exchange particle m SI and coupling constant α SI . Because of the expansion behavior in a Robertson-Walker metric we investigate self-interacting dark matter that is warm in the case of thermal relics. The scaling behavior of dark matter self-interaction energy density (ρ SI ∝a -6 ) shows that it can be the dominant contribution (only) in the very early universe. Thus its impact on primordial nucleosynthesis is used to restrict the interaction strength m SI /√(α SI ), which we find to be at least as strong as the strong interaction. Furthermore we explore dark matter decoupling in a self-interaction dominated universe, which is done for the self-interacting warm dark matter as well as for collisionless cold dark matter in a two component scenario. We find that strong dark matter self-interactions do not contradict superweak inelastic interactions between self-interacting dark matter and baryonic matter (σ A SIDM weak ) and that the natural scale of collisionless cold dark matter decoupling exceeds the weak scale (σ A CDM >σ weak ) and depends linearly on the particle mass. Finally structure formation analysis reveals a linear growing solution during self-interaction domination (δ∝a); however, only noncosmological scales are enhanced.
Effects of the interaction between dark energy and dark matter on cosmological parameters
International Nuclear Information System (INIS)
He, Jian-Hua; Wang, Bin
2008-01-01
We examine the effects of possible phenomenological interactions between dark energy and dark matter on cosmological parameters and their efficiency in solving the coincidence problem. We work with two simple parameterizations of the dynamical dark energy equation of state and the constant dark energy equation of state. Using observational data coming from the new 182 Gold type Ia supernova samples, the shift parameter of the Cosmic Microwave Background given by the three-year Wilkinson Microwave Anisotropy Probe observations and the baryon acoustic oscillation measurement from the Sloan Digital Sky Survey, we perform a statistical joint analysis of different forms of phenomenological interaction between dark energy and dark matter
Secular evolution of galaxies and galaxy clusters in decaying dark matter cosmology
International Nuclear Information System (INIS)
Ferrer, Francesc; Nipoti, Carlo; Ettori, Stefano
2009-01-01
If the dark matter sector in the Universe is composed by metastable particles, galaxies and galaxy clusters are expected to undergo significant secular evolution from high to low redshift. We show that the decay of dark matter, with a lifetime compatible with cosmological constraints, can be at the origin of the observed evolution of the Tully-Fisher relation of disk galaxies and alleviate the problem of the size evolution of elliptical galaxies, while being consistent with the current observational constraints on the gas fraction of clusters of galaxies.
Dutta, Jibitesh; Khyllep, Wompherdeiki; Tamanini, Nicola
2018-01-01
We consider scalar field models of dark energy interacting with dark matter through a coupling proportional to the contraction of the four-derivative of the scalar field with the four-velocity of the dark matter fluid. The coupling is realized at the Lagrangian level employing the formalism of Scalar-Fluid theories, which use a consistent Lagrangian approach for relativistic fluid to describe dark matter. This framework produces fully covariant field equations, from which we can derive unequivocal cosmological equations at both background and linear perturbations levels. The background evolution is analyzed in detail applying dynamical systems techniques, which allow us to find the complete asymptotic behavior of the universe given any set of model parameters and initial conditions. Furthermore we study linear cosmological perturbations investigating the growth of cosmic structures within the quasi-static approximation. We find that these interacting dark energy models give rise to interesting phenomenological dynamics, including late-time transitions from dark matter to dark energy domination, matter and accelerated scaling solutions and dynamical crossing of the phantom barrier. Moreover we obtain possible deviations from standard ΛCDM behavior at the linear perturbations level, which have an impact on the dynamics of structure formation and might provide characteristic observational signatures.
Cosmological N-body simulations with a tree code - Fluctuations in the linear and nonlinear regimes
International Nuclear Information System (INIS)
Suginohara, Tatsushi; Suto, Yasushi; Bouchet, F.R.; Hernquist, L.
1991-01-01
The evolution of gravitational systems is studied numerically in a cosmological context using a hierarchical tree algorithm with fully periodic boundary conditions. The simulations employ 262,144 particles, which are initially distributed according to scale-free power spectra. The subsequent evolution is followed in both flat and open universes. With this large number of particles, the discretized system can accurately model the linear phase. It is shown that the dynamics in the nonlinear regime depends on both the spectral index n and the density parameter Omega. In Omega = 1 universes, the evolution of the two-point correlation function Xi agrees well with similarity solutions for Xi greater than about 100 but its slope is steeper in open models with the same n. 28 refs
Probing sub-GeV dark matter-baryon scattering with cosmological observables
Xu, Weishuang Linda; Dvorkin, Cora; Chael, Andrew
2018-05-01
We derive new limits on the elastic scattering cross section between baryons and dark matter using cosmic microwave background data from the Planck satellite and measurements of the Lyman-alpha forest flux power spectrum from the Sloan Digital Sky Survey. Our analysis addresses generic cross sections of the form σ ∝vn , where v is the dark matter-baryon relative velocity, allowing for constraints on the cross section independent of specific particle physics models. We include high-ℓ polarization data from Planck in our analysis, improving over previous constraints. We apply a more careful treatment of dark matter thermal evolution than previously done, allowing us to extend our constraints down to dark matter masses of ˜MeV . We show in this work that cosmological probes are complementary to current direct detection and astrophysical searches.
Non-linear Matter Spectra in Coupled Quintessence
Saracco, F; Tetradis, N; Pettorino, V; Robbers, G
2010-01-01
We consider cosmologies in which a dark-energy scalar field interacts with cold dark matter. The growth of perturbations is followed beyond the linear level by means of the time-renormalization-group method, which is extended to describe a multi-component matter sector. Even in the absence of the extra interaction, a scale-dependent bias is generated as a consequence of the different initial conditions for baryons and dark matter after decoupling. The effect is greatly enhanced by the extra coupling and can be at the percent level in the range of scales of baryonic acoustic oscillations. We compare our results with N-body simulations, finding very good agreement.
The simplest non-minimal matter-geometry coupling in the f(R, T) cosmology
Energy Technology Data Exchange (ETDEWEB)
Moraes, P.H.R.S. [ITA - Instituto Tecnologico de Aeronautica, Departamento de Fisica, Sao Paulo (Brazil); Sahoo, P.K. [Birla Institute of Technology and Science-Pilani, Department of Mathematics, Hyderabad (India)
2017-07-15
f(R, T) gravity is an extended theory of gravity in which the gravitational action contains general terms of both the Ricci scalar R and the trace of the energy-momentum tensor T. In this way, f(R, T) models are capable of describing a non-minimal coupling between geometry (through terms in R) and matter (through terms in T). In this article we construct a cosmological model from the simplest non-minimal matter-geometry coupling within the f(R, T) gravity formalism, by means of an effective energy-momentum tensor, given by the sum of the usual matter energy-momentum tensor with a dark energy contribution, with the latter coming from the matter-geometry coupling terms. We apply the energy conditions to our solutions in order to obtain a range of values for the free parameters of the model which yield a healthy and well-behaved scenario. For some values of the free parameters which are submissive to the energy conditions application, it is possible to predict a transition from a decelerated period of the expansion of the universe to a period of acceleration (dark energy era). We also propose further applications of this particular case of the f(R, T) formalism in order to check its reliability in other fields, rather than cosmology. (orig.)
The simplest non-minimal matter-geometry coupling in the f(R, T) cosmology
International Nuclear Information System (INIS)
Moraes, P.H.R.S.; Sahoo, P.K.
2017-01-01
f(R, T) gravity is an extended theory of gravity in which the gravitational action contains general terms of both the Ricci scalar R and the trace of the energy-momentum tensor T. In this way, f(R, T) models are capable of describing a non-minimal coupling between geometry (through terms in R) and matter (through terms in T). In this article we construct a cosmological model from the simplest non-minimal matter-geometry coupling within the f(R, T) gravity formalism, by means of an effective energy-momentum tensor, given by the sum of the usual matter energy-momentum tensor with a dark energy contribution, with the latter coming from the matter-geometry coupling terms. We apply the energy conditions to our solutions in order to obtain a range of values for the free parameters of the model which yield a healthy and well-behaved scenario. For some values of the free parameters which are submissive to the energy conditions application, it is possible to predict a transition from a decelerated period of the expansion of the universe to a period of acceleration (dark energy era). We also propose further applications of this particular case of the f(R, T) formalism in order to check its reliability in other fields, rather than cosmology. (orig.)
Direct dark matter searches—Test of the Big Bounce Cosmology
International Nuclear Information System (INIS)
Cheung, Yeuk-Kwan E.; Vergados, J.D.
2015-01-01
We consider the possibility of using dark matter particle's mass and its interaction cross section as a smoking gun signal of the existence of a Big Bounce at the early stage in the evolution of our currently observed universe. A study of dark matter production in the pre-bounce contraction and the post bounce expansion epochs of this universe reveals a new venue for achieving the observed relic abundance of our present universe. Specifically, it predicts a characteristic relation governing a dark matter mass and interaction cross section and a factor of 1/2 in thermally averaged cross section, as compared to the non-thermal production in standard cosmology, is needed for creating enough dark matter particle to satisfy the currently observed relic abundance because dark matter is being created during the pre-bounce contraction, in addition to the post-bounce expansion. As the production rate is lower than the Hubble expansion rate information of the bounce universe evolution is preserved. Therefore once the value of dark matter mass and interaction cross section are obtained by direct detection in laboratories, this alternative route becomes a signature prediction of the bounce universe scenario. This leads us to consider a scalar dark matter candidate, which if it is light, has important implications on dark matter searches
Reconstructing matter profiles of spherically compensated cosmic regions in ΛCDM cosmology
de Fromont, Paul; Alimi, Jean-Michel
2018-02-01
The absence of a physically motivated model for large-scale profiles of cosmic voids limits our ability to extract valuable cosmological information from their study. In this paper, we address this problem by introducing the spherically compensated cosmic regions, named CoSpheres. Such cosmic regions are identified around local extrema in the density field and admit a unique compensation radius R1 where the internal spherical mass is exactly compensated. Their origin is studied by extending the standard peak model and implementing the compensation condition. Since the compensation radius evolves as the Universe itself, R1(t) ∝ a(t), CoSpheres behave as bubble Universes with fixed comoving volume. Using the spherical collapse model, we reconstruct their profiles with a very high accuracy until z = 0 in N-body simulations. CoSpheres are symmetrically defined and reconstructed for both central maximum (seeding haloes and galaxies) and minimum (identified with cosmic voids). We show that the full non-linear dynamics can be solved analytically around this particular compensation radius, providing useful predictions for cosmology. This formalism highlights original correlations between local extremum and their large-scale cosmic environment. The statistical properties of these spherically compensated cosmic regions and the possibilities to constrain efficiently both cosmology and gravity will be investigated in companion papers.
International Nuclear Information System (INIS)
Hwang, Jai-chan; Noh, Hyerim
2005-01-01
We consider a general relativistic zero-pressure irrotational cosmological medium perturbed to the third order. We assume a flat Friedmann background but include the cosmological constant. We ignore the rotational perturbation which decays in expanding phase. In our previous studies we discovered that, to the second-order perturbation, except for the gravitational wave contributions, the relativistic equations coincide exactly with the previously known Newtonian ones. Since the Newtonian second-order equations are fully nonlinear, any nonvanishing third- and higher-order terms in the relativistic analyses are supposed to be pure relativistic corrections. In this work, we derive such correction terms appearing in the third order. Continuing our success in the second-order perturbations, we take the comoving gauge. We discover that the third-order correction terms are of φ v order higher than the second-order terms where φ v is a gauge-invariant combination related to the three-space curvature perturbation in the comoving gauge; compared with the Newtonian potential, we have δΦ∼(3/5)φ v to the linear order. Therefore, the pure general relativistic effects are of φ v order higher than the Newtonian ones. The corrections terms are independent of the horizon scale and depend only on the linear-order gravitational potential (curvature) perturbation strength. From the temperature anisotropy of cosmic microwave background, we have (δT/T)∼(1/3)δΦ∼(1/5)φ v ∼10 -5 . Therefore, our present result reinforces our previous important practical implication that near the current era one can use the large-scale Newtonian numerical simulation more reliably even as the simulation scale approaches near (and goes beyond) the horizon
How robust are inflation model and dark matter constraints from cosmological data?
International Nuclear Information System (INIS)
Hamann, J.; Hannestad, S.; Sloth, M.S.; Wong, Y.Y.Y.
2006-11-01
High-precision data from observation of the cosmic microwave background and the large scale structure of the universe provide very tight constraints on the effective parameters that describe cosmological inflation. Indeed, within a constrained class of ΛCDM models, the simple λφ 4 chaotic inflation model already appears to be ruled out by cosmological data. In this paper, we compute constraints on inflationary parameters within a more general framework that includes other physically motivated parameters such as a nonzero neutrino mass. We find that a strong degeneracy between the tensor-to-scalar ratio τ and the neutrino mass prevents λφ 4 from being excluded by present data. Reversing the argument, if λφ 4 is the correct model of inflation, it predicts a sum of neutrino masses at 0.3→0.5 eV, a range compatible with present experimental limits and within the reach of the next generation of neutrino mass measurements. We also discuss the associated constraints on the dark matter density, the dark energy equation of state, and spatial curvature, and show that the allowed regions are significantly altered. Importantly, we find an allowed range of 0.094 c h 2 <0.136 for the dark matter density, a factor of two larger than that reported in previous studies. This expanded parameter space may have implications for constraints on SUSY dark matter models. (orig.)
Nonlinear light-matter interactions in engineered optical media
Litchinitser, Natalia
In this talk, we consider fundamental optical phenomena at the interface of nonlinear and singular optics in artificial media, including theoretical and experimental studies of linear and nonlinear light-matter interactions of vector and singular optical beams in metamaterials. We show that unique optical properties of metamaterials open unlimited prospects to ``engineer'' light itself. Thanks to their ability to manipulate both electric and magnetic field components, metamaterials open new degrees of freedom for tailoring complex polarization states and orbital angular momentum (OAM) of light. We will discuss several approaches to structured light manipulation on the nanoscale using metal-dielectric, all-dielectric and hyperbolic metamaterials. These new functionalities, including polarization and OAM conversion, beam magnification and de-magnification, and sub-wavelength imaging using novel non-resonant hyperlens are likely to enable a new generation of on-chip or all-fiber structured light applications. The emergence of metamaterials also has a strong potential to enable a plethora of novel nonlinear light-matter interactions and even new nonlinear materials. In particular, nonlinear focusing and defocusing effects are of paramount importance for manipulation of the minimum focusing spot size of structured light beams necessary for nanoscale trapping, manipulation, and fundamental spectroscopic studies. Colloidal suspensions offer as a promising platform for engineering polarizibilities and realization of large and tunable nonlinearities. We will present our recent studies of the phenomenon of spatial modulational instability leading to laser beam filamentation in an engineered soft-matter nonlinear medium. Finally, we introduce so-called virtual hyperbolic metamaterials formed by an array of plasma channels in air as a result of self-focusing of an intense laser pulse, and show that such structure can be used to manipulate microwave beams in a free space. This
Wang, B; Abdalla, E; Atrio-Barandela, F; Pavón, D
2016-09-01
Models where dark matter and dark energy interact with each other have been proposed to solve the coincidence problem. We review the motivations underlying the need to introduce such interaction, its influence on the background dynamics and how it modifies the evolution of linear perturbations. We test models using the most recent observational data and we find that the interaction is compatible with the current astronomical and cosmological data. Finally, we describe the forthcoming data sets from current and future facilities that are being constructed or designed that will allow a clearer understanding of the physics of the dark sector.
Zhang Yuan Zhong
2002-01-01
This book is one of a series in the areas of high-energy physics, cosmology and gravitation published by the Institute of Physics. It includes courses given at a doctoral school on 'Relativistic Cosmology: Theory and Observation' held in Spring 2000 at the Centre for Scientific Culture 'Alessandro Volta', Italy, sponsored by SIGRAV-Societa Italiana di Relativita e Gravitazione (Italian Society of Relativity and Gravitation) and the University of Insubria. This book collects 15 review reports given by a number of outstanding scientists. They touch upon the main aspects of modern cosmology from observational matters to theoretical models, such as cosmological models, the early universe, dark matter and dark energy, modern observational cosmology, cosmic microwave background, gravitational lensing, and numerical simulations in cosmology. In particular, the introduction to the basics of cosmology includes the basic equations, covariant and tetrad descriptions, Friedmann models, observation and horizons, etc. The ...
PeV IceCube signals and Dark Matter relic abundance in modified cosmologies
Lambiase, G.; Mohanty, S.; Stabile, An.
2018-04-01
The discovery by the IceCube experiment of a high-energy astrophysical neutrino flux with energies of the order of PeV, has opened new scenarios in astroparticles physics. A possibility to explain this phenomenon is to consider the minimal models of Dark Matter (DM) decay, the 4-dimensional operator ˜ y_{α χ }\\overline{{L_{L_{α }}}} H χ , which is also able to generate the correct abundance of DM in the Universe. Assuming that the cosmological background evolves according to the standard cosmological model, it follows that the rate of DM decay Γ _χ ˜ |y_{α χ }|^2 needed to get the correct DM relic abundance (Γ _χ ˜ 10^{-58}) differs by many orders of magnitude with respect that one needed to explain the IceCube data (Γ _χ ˜ 10^{-25}), making the four-dimensional operator unsuitable. In this paper we show that assuming that the early Universe evolution is governed by a modified cosmology, the discrepancy between the two the DM decay rates can be reconciled, and both the IceCube neutrino rate and relic density can be explained in a minimal model.
Numerical Convergence in the Dark Matter Halos Properties Using Cosmological Simulations
Mosquera-Escobar, X. E.; Muñoz-Cuartas, J. C.
2017-07-01
Nowadays, the accepted cosmological model is the so called -Cold Dark Matter (CDM). In such model, the universe is considered to be homogeneous and isotropic, composed of diverse components as the dark matter and dark energy, where the latter is the most abundant one. Dark matter plays an important role because it is responsible for the generation of gravitational potential wells, commonly called dark matter halos. At the end, dark matter halos are characterized by a set of parameters (mass, radius, concentration, spin parameter), these parameters provide valuable information for different studies, such as galaxy formation, gravitational lensing, etc. In this work we use the publicly available code Gadget2 to perform cosmological simulations to find to what extent the numerical parameters of the simu- lations, such as gravitational softening, integration time step and force calculation accuracy affect the physical properties of the dark matter halos. We ran a suite of simulations where these parameters were varied in a systematic way in order to explore accurately their impact on the structural parameters of dark matter halos. We show that the variations on the numerical parameters affect the structural pa- rameters of dark matter halos, such as concentration, virial radius, and concentration. We show that these modifications emerged when structures become non- linear (at redshift 2) for the scale of our simulations, such that these variations affected the formation and evolution structure of halos mainly at later cosmic times. As a quantitative result, we propose which would be the most appropriate values for the numerical parameters of the simulations, such that they do not affect the halo properties that are formed. For force calculation accuracy we suggest values smaller or equal to 0.0001, integration time step smaller o equal to 0.005 and for gravitational softening we propose equal to 1/60th of the mean interparticle distance, these values, correspond to the
An effective description of dark matter and dark energy in the mildly non-linear regime
Energy Technology Data Exchange (ETDEWEB)
Lewandowski, Matthew; Senatore, Leonardo [Stanford Institute for Theoretical Physics, Stanford University, Stanford, CA 94306 (United States); Maleknejad, Azadeh, E-mail: matthew.lewandowski@cea.fr, E-mail: azade@ipm.ir, E-mail: senatore@stanford.edu [School of Physics, Institute for Research in Fundamental Sciences (IPM), P. Code. 19538-33511, Tehran (Iran, Islamic Republic of)
2017-05-01
In the next few years, we are going to probe the low-redshift universe with unprecedented accuracy. Among the various fruits that this will bear, it will greatly improve our knowledge of the dynamics of dark energy, though for this there is a strong theoretical preference for a cosmological constant. We assume that dark energy is described by the so-called Effective Field Theory of Dark Energy, which assumes that dark energy is the Goldstone boson of time translations. Such a formalism makes it easy to ensure that our signatures are consistent with well-established principles of physics. Since most of the information resides at high wavenumbers, it is important to be able to make predictions at the highest wavenumber that is possible. The Effective Field Theory of Large-Scale Structure (EFTofLSS) is a theoretical framework that has allowed us to make accurate predictions in the mildly non-linear regime. In this paper, we derive the non-linear equations that extend the EFTofLSS to include the effect of dark energy both on the matter fields and on the biased tracers. For the specific case of clustering quintessence, we then perturbatively solve to cubic order the resulting non-linear equations and construct the one-loop power spectrum of the total density contrast.
Relation Between Initial Cosmological Conditions and the Properties of Dark Matter Haloes
International Nuclear Information System (INIS)
Semenov, Vadim
2013-01-01
The core-cusp problem is one of the essential issues in modern cosmology. The Entropy Theory of haloes Evolution recently suggested by Lukash, Doroshkevich and Mikheeva is one of the possible solutions to this problem. This work compares some results of numerical simulation of Large-Scale Structure with the conclusions of the Entropy Theory in order to verify this theory. The numerical simulation was performed in a volume 100 Mpc/h in a side using ∼ 17 million particles. Dark matter particles, which then form virialized haloes, were found in the initial perturbation field. This work investigates the distribution of these dark matter particles and measures the velocity dispersion profiles. It also traces evolution of haloes entropy profiles. On the whole, simulation results correspond to Entropy Theory of haloes evolution
Brane-world and loop cosmology from a gravity–matter coupling perspective
Energy Technology Data Exchange (ETDEWEB)
Olmo, Gonzalo J., E-mail: gonzalo.olmo@csic.es [Departamento de Física Teórica and IFIC, Centro Mixto Universidad de Valencia – CSIC, Universidad de Valencia, Burjassot-46100, Valencia (Spain); Departamento de Física, Universidade Federal da Paraíba, 58051-900 João Pessoa, Paraíba (Brazil); Rubiera-Garcia, D., E-mail: drubiera@fisica.ufpb.br [Departamento de Física, Universidade Federal da Paraíba, 58051-900 João Pessoa, Paraíba (Brazil)
2015-01-05
We show that the effective brane-world and the loop quantum cosmology background expansion histories can be reproduced from a modified gravity perspective in terms of an f(R) gravity action plus a g(R) term non-minimally coupled with the matter Lagrangian. The reconstruction algorithm that we provide depends on a free function of the matter density that must be specified in each case and allows to obtain analytical solutions always. In the simplest cases, the function f(R) is quadratic in the Ricci scalar, R, whereas g(R) is linear. Our approach is compared with recent results in the literature. We show that working in the Palatini formalism there is no need to impose any constraint that keeps the equations second-order, which is a key requirement for the successful implementation of the reconstruction algorithm.
Cornering pseudoscalar-mediated dark matter with the LHC and cosmology
Banerjee, Shankha; Barducci, Daniele; Bélanger, Geneviève; Fuks, Benjamin; Goudelis, Andreas; Zaldivar, Bryan
2017-07-01
Models in which dark matter particles communicate with the visible sector through a pseudoscalar mediator are well-motivated both from a theoretical and from a phenomenological standpoint. With direct detection bounds being typically subleading in such scenarios, the main constraints stem either from collider searches for dark matter, or from indirect detection experiments. However, LHC searches for the mediator particles themselves can not only compete with — or even supersede — the reach of direct collider dark matter probes, but they can also test scenarios in which traditional monojet searches become irrelevant, especially when the mediator cannot decay on-shell into dark matter particles or its decay is suppressed. In this work we perform a detailed analysis of a pseudoscalar-mediated dark matter simplified model, taking into account a large set of collider constraints and concentrating on the parameter space regions favoured by cos-mological and astrophysical data. We find that mediator masses above 100-200 GeV are essentially excluded by LHC searches in the case of large couplings to the top quark, while forthcoming collider and astrophysical measurements will further constrain the available parameter space.
Baker, Michael J.; Breitbach, Moritz; Kopp, Joachim; Mittnacht, Lukas
2018-03-01
The cosmological abundance of dark matter can be significantly influenced by the temperature dependence of particle masses and vacuum expectation values. We illustrate this point in three simple freeze-in models. The first one, which we call kinematically induced freeze-in, is based on the observation that the effective mass of a scalar temporarily becomes very small as the scalar potential undergoes a second order phase transition. This opens dark matter production channels that are otherwise forbidden. The second model we consider, dubbed vev-induced freeze-in, is a fermionic Higgs portal scenario. Its scalar sector is augmented compared to the Standard Model by an additional scalar singlet, S, which couples to dark matter and temporarily acquires a vacuum expectation value (a two-step phase transition or "vev flip-flop"). While ≠ 0, the modified coupling structure in the scalar sector implies that dark matter production is significantly enhanced compared to the = 0 phases realised at very early times and again today. The third model, which we call mixing-induced freeze-in, is similar in spirit, but here it is the mixing of dark sector fermions, induced by non-zero , that temporarily boosts the dark matter production rate. For all three scenarios, we carefully dissect the evolution of the dark sector in the early Universe. We compute the DM relic abundance as a function of the model parameters, emphasising the importance of thermal corrections and the proper treatment of phase transitions in the calculation.
Comparing AMR and SPH Cosmological Simulations. I. Dark Matter and Adiabatic Simulations
O'Shea, Brian W.; Nagamine, Kentaro; Springel, Volker; Hernquist, Lars; Norman, Michael L.
2005-09-01
We compare two cosmological hydrodynamic simulation codes in the context of hierarchical galaxy formation: the Lagrangian smoothed particle hydrodynamics (SPH) code GADGET, and the Eulerian adaptive mesh refinement (AMR) code Enzo. Both codes represent dark matter with the N-body method but use different gravity solvers and fundamentally different approaches for baryonic hydrodynamics. The SPH method in GADGET uses a recently developed ``entropy conserving'' formulation of SPH, while for the mesh-based Enzo two different formulations of Eulerian hydrodynamics are employed: the piecewise parabolic method (PPM) extended with a dual energy formulation for cosmology, and the artificial viscosity-based scheme used in the magnetohydrodynamics code ZEUS. In this paper we focus on a comparison of cosmological simulations that follow either only dark matter, or also a nonradiative (``adiabatic'') hydrodynamic gaseous component. We perform multiple simulations using both codes with varying spatial and mass resolution with identical initial conditions. The dark matter-only runs agree generally quite well provided Enzo is run with a comparatively fine root grid and a low overdensity threshold for mesh refinement, otherwise the abundance of low-mass halos is suppressed. This can be readily understood as a consequence of the hierarchical particle-mesh algorithm used by Enzo to compute gravitational forces, which tends to deliver lower force resolution than the tree-algorithm of GADGET at early times before any adaptive mesh refinement takes place. At comparable force resolution we find that the latter offers substantially better performance and lower memory consumption than the present gravity solver in Enzo. In simulations that include adiabatic gasdynamics we find general agreement in the distribution functions of temperature, entropy, and density for gas of moderate to high overdensity, as found inside dark matter halos. However, there are also some significant differences in
Too hot to handle? Analytic solutions for massive neutrino or warm dark matter cosmologies
Slepian, Zachary; Portillo, Stephen K. N.
2018-05-01
We obtain novel closed-form solutions to the Friedmann equation for cosmological models containing a component whose equation of state is that of radiation (w = 1/3) at early times and that of cold pressureless matter (w = 0) at late times. The equation of state smoothly transitions from the early to late-time behavior and exactly describes the evolution of a species with a Dirac Delta function distribution in momentum magnitudes |p_0| (i.e. all particles have the same |p_0|). Such a component, here termed "hot matter", is an approximate model for both neutrinos and warm dark matter. We consider it alone and in combination with cold matter and with radiation, also obtaining closed-form solutions for the growth of super-horizon perturbations in each case. The idealized model recovers t(a) to better than 1.5% accuracy for all a relative to a Fermi-Dirac distribution (as describes neutrinos). We conclude by adding the second moment of the distribution to our exact solution and then generalizing to include all moments of an arbitrary momentum distribution in a closed-form solution.
Mass quantization in quantum and susy cosmological models with matter content
International Nuclear Information System (INIS)
Ortiz, C; Socorro, J; Tkach, V I; Torres, J; Rosales, J
2005-01-01
We present the study of the quantum closed Friedmann-Robertson-Walker (FRW) cosmological model with a matter content given by a perfect fluid with barotropic state equation p = γρ The Wheeler-DeWitt equation is viewed as the Schroedinger equation for the linear harmonic oscillator with energy E. Such type of Universe has quantized masses of the order of the Planck mass and harmonic oscillator wave functions. Then, we consider the n = 2 supersymmetric superfield approach for the same model and obtain a normalizable wave function (at zero energy) of the universe. Besides, the mass parameter spectrum is found in the Schroedinger picture, being similar to those obtained by other methods, using a black hole system
SECOND-ORDER SOLUTIONS OF COSMOLOGICAL PERTURBATION IN THE MATTER-DOMINATED ERA
International Nuclear Information System (INIS)
Hwang, Jai-chan; Noh, Hyerim; Gong, Jinn-Ouk
2012-01-01
We present the growing mode solutions of cosmological perturbations to the second order in the matter-dominated era. We also present several gauge-invariant combinations of perturbation variables to the second order in the most general fluid context. Based on these solutions, we study the Newtonian correspondence of relativistic perturbations to the second order. In addition to the previously known exact relativistic/Newtonian correspondence of density and velocity perturbations to the second order in the comoving gauge, here we show that in the sub-horizon limit we have the correspondences for density, velocity, and potential perturbations in the zero-shear gauge and in the uniform-expansion gauge to the second order. Density perturbation in the uniform-curvature gauge also shows the correspondence to the second order in the sub-horizon scale. We also identify the relativistic gravitational potential that shows exact correspondence to the Newtonian one to the second order.
Limits on cold dark matter cosmologies from new anisotropy bounds on the cosmic microwave background
International Nuclear Information System (INIS)
Vittorio, N.; Meinhold, P.; Lubin, P.; Muciaccia, P.F.; Silk, J.
1991-01-01
A self-consistent method is presented for comparing theoretical predictions of and observational upper limits on CMB anisotropy. New bounds on CDM cosmologies set by the UCSB South Pole experiment on the 1 deg angular scale are presented. An upper limit of 4.0 x 10 to the -5th is placed on the rms differential temperature anisotropy to a 95 percent confidence level and a power of the test beta = 55 percent. A lower limit of about 0.6/b is placed on the density parameter of cold dark matter universes with greater than about 3 percent baryon abundance and a Hubble constant of 50 km/s/Mpc, where b is the bias factor, equal to unity only if light traces mass. 22 refs
Off-shell dark matter: A cosmological relic of quantum gravity
Saravani, Mehdi; Afshordi, Niayesh
2017-02-01
We study a novel proposal for the origin of cosmological cold dark matter (CDM) which is rooted in the quantum nature of spacetime. In this model, off-shell modes of quantum fields can exist in asymptotic states as a result of spacetime nonlocality (expected in generic theories of quantum gravity) and play the role of CDM, which we dub off-shell dark matter (O f DM ). However, their rate of production is suppressed by the scale of nonlocality (e.g. Planck length). As a result, we show that O f DM is only produced in the first moments of big bang, and then effectively decouples (except through its gravitational interactions). We examine the observational predictions of this model: In the context of cosmic inflation, we show that this proposal relates the reheating temperature to the inflaton mass, which narrows down the uncertainty in the number of e -foldings of specific inflationary scenarios. We also demonstrate that O f DM is indeed cold, and discuss potentially observable signatures on small scale matter power spectrum.
Dark matter as a non-linear effect of gravitation
International Nuclear Information System (INIS)
Maia, M.D.; Capistrano, A.J.S.
2006-01-01
The rotation curves of stars in disk galaxies are calculated with the Newtonian law of motion applied to a scalar potential derived from the geodesic equation, only, under the slow motion condition, the so-called Nearly Newtonian Gravity (NNG). A nearly Newtonian gravitational potential, Φ NN = -1/2 c 2 (1+g 44 ), is obtained, characterized by an exact solution of Einsteins equations, with the non-linear effects present in the component g 44 . This gravitational field lies somewhere between General Relativity and Newtonian Gravity. Therefore, Einsteins equations and the equivalence principle are preserved, but the general covariance is broken. The resulting curves are remarkably close to the observed rotation curves in spiral galaxies, suggesting that a substantial component of dark matter may be explained by the non-linearity of Einsteins equations. (author)
THE INNER STRUCTURE OF DWARF-SIZED HALOS IN WARM AND COLD DARK MATTER COSMOLOGIES
Energy Technology Data Exchange (ETDEWEB)
González-Samaniego, A.; Avila-Reese, V. [Instituto de Astronomía, Universidad Nacional Autónoma de México, A.P. 70-264, 04510, México, D.F., México (Mexico); Colín, P. [Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, A.P. 72-3 (Xangari), Morelia, Michoacán 58089, México (Mexico)
2016-03-10
By means of N-body + hydrodynamic zoom-in simulations we study the evolution of the inner dark matter and stellar mass distributions of central dwarf galaxies formed in halos of virial masses M{sub v} = (2–3) × 10{sup 10} h{sup −1} M{sub ⊙} at z = 0, both in a warm dark matter (WDM) and cold dark matter (CDM) cosmology. The half-mode mass in the WDM power spectrum of our simulations is M{sub f} = 2 × 10{sup 10} h{sup −1} M{sub ⊙}. In the dark matter (DM) only simulations halo density profiles are well described by the Navarro–Frenk–White parametric fit in both cosmologies, though the WDM halos have concentrations lower by factors of 1.5–2.0 than their CDM counterparts. In the hydrodynamic simulations, the effects of baryons significantly flatten the inner density, velocity dispersion, and pseudo phase space density profiles of the WDM halos but not of the CDM ones. The density slope, measured at ≈0.02R{sub v}, α{sub 0.02}, becomes shallow in periods of 2–5 Gyr in the WDM runs. We explore whether this flattening process correlates with the global star formation (SF), M{sub s}/M{sub v} ratio, gas outflow, and internal specific angular momentum histories. We do not find any clear trends, but when α{sub 0.02} is shallower than −0.5, M{sub s}/M{sub v} is always between 0.25% and 1%. We conclude that the main reason for the formation of the shallow core is the presence of strong gas mass fluctuations inside the inner halo, which are a consequence of the feedback driven by a very bursty and sustained SF history in shallow gravitational potentials. Our WDM halos, which assemble late and are less concentrated than the CDM ones, obey these conditions. There are also (rare) CDM systems with extended mass assembly histories that obey these conditions and form shallow cores. The dynamical heating and expansion processes behind the DM core flattening apply also to the stars in such a way that the stellar age and metallicity gradients of the
Particle physics and cosmology beyond the Standard Model: inflation, dark matter and flavour
International Nuclear Information System (INIS)
Heurtier, L.
2015-01-01
This thesis has been focusing on beyond the Standard Model aspects of particle physics and their implication in cosmology. We have gone through this work along the timeline of the Universe History focusing on three major topics that are the inflationary period, the dark matter relic density production and detection, and finally the question of flavor changing constraints on low energy supersymmetric theories. In the first part of this thesis, after reviewing the theoretical and phenomenological aspects of both the Big Bang theory and the theory of Inflation we will study in detail how describing Inflation in a high energy supersymmetric theory. The second part of this thesis is dedicated to dark matter. We have studied phenomenological aspects of simple models, extending the present Standard Model with simple abelian symmetries, by assuming that the constituent of dark matter would be able to exchange information with the visible sector by the help of a mediator particle. We have studied in particular possible interactions of heavy or light dark matter with respectively the strong and the electroweak sectors of the Standard Model. Our models are strongly constrained of course by experiments. The third part of this work will be dedicated to a different aspect of beyond Standard Model theories, that is the treatment of the flavour changing processes of particle physics. The Minimal Supersymmetric Standard Model (MSSM), as one of these possible enlargement of the Standard Model, introduces new processes of flavour changing that are highly constrained by experiment. We present some works in which we consider the possibility of adding so called Dirac Gauginos to the MSSM to render flavour changing weaker in the theory, and propose different flavour patterns theories
Nonlinear mean field theory for nuclear matter and surface properties
International Nuclear Information System (INIS)
Boguta, J.; Moszkowski, S.A.
1983-01-01
Nuclear matter properties are studied in a nonlinear relativistic mean field theory. We determine the parameters of the model from bulk properties of symmetric nuclear matter and a reasonable value of the effective mass. In this work, we stress the nonrelativistic limit of the theory which is essentially equivalent to a Skyrme hamiltonian, and we show that most of the results can be obtained, to a good approximation, analytically. The strength of the required parameters is determined from the binding energy and density of nuclear matter and the effective nucleon mass. For realistic values of the parameters, the nonrelativistic approximation turns out to be quite satisfactory. Using reasonable values of the parameters, we can account for other key properties of nuclei, such as the spin-orbit coupling, surface energy, and diffuseness of the nuclear surface. Also the energy dependence of the nucleon-nucleus optical model is accounted for reasonably well except near the Fermi surface. It is found, in agreement with empirical results, that the Landau parameter F 0 is quite small in normal nuclear matter. Both density dependence and momentum dependence of the NN interaction, but especially the former, are important for nuclear saturation. The required scalar and vector coupling constants agree fairly well with those obtained from analyses of NN scattering phase shifts with one-boson-exchange models. The mean field theory provides a semiquantitative justification for the weak Skyrme interaction in odd states. The strength of the required nonlinear term is roughly consistent with that derived using a new version of the chiral mean field theory in which the vector mass as well as the nucleon mass is generated by the sigma-field. (orig.)
Unification of inflation, dark energy, and dark matter within the Salam-Sezgin cosmological model
International Nuclear Information System (INIS)
Henriques, Alfredo B.; Potting, Robertus; Sa, Paulo M.
2009-01-01
We investigate a cosmological model, based on the Salam-Sezgin six-dimensional supergravity theory and on previous work by Anchordoqui, Goldberg, Nawata, and Nunez. Assuming a period of warm inflation, we show that it is possible to extend the evolution of the model back in time, to include the inflationary period, thus unifying inflation, dark matter, and dark energy within a single framework. Like the previous authors, we were not able to obtain the full dark matter content of the universe from the Salam-Sezgin scalar fields. However, even if only partially successful, this work shows that present-day theories, based on superstrings and supergravity, may eventually lead to a comprehensive modeling of the evolution of the universe. We find that the gravitational-wave spectrum of the model has a nonconstant negative slope in the frequency range (10 -15 -10 6 ) rad/s, and that, unlike standard (cold) inflation models, it shows no structure in the MHz/GHz range of frequencies.
Modeling the Gravitational Potential of a Cosmological Dark Matter Halo with Stellar Streams
Energy Technology Data Exchange (ETDEWEB)
Sanderson, Robyn E. [Department of Astronomy, Columbia University, 550 W 120th St, New York, NY 10027 (United States); Hartke, Johanna; Helmi, Amina, E-mail: robyn@astro.columbia.edu [Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen (Netherlands)
2017-02-20
Stellar streams result from the tidal disruption of satellites and star clusters as they orbit a host galaxy, and can be very sensitive probes of the gravitational potential of the host system. We select and study narrow stellar streams formed in a Milky-Way-like dark matter halo of the Aquarius suite of cosmological simulations, to determine if these streams can be used to constrain the present day characteristic parameters of the halo’s gravitational potential. We find that orbits integrated in both spherical and triaxial static Navarro–Frenk–White potentials reproduce the locations and kinematics of the various streams reasonably well. To quantify this further, we determine the best-fit potential parameters by maximizing the amount of clustering of the stream stars in the space of their actions. We show that using our set of Aquarius streams, we recover a mass profile that is consistent with the spherically averaged dark matter profile of the host halo, although we ignored both triaxiality and time evolution in the fit. This gives us confidence that such methods can be applied to the many streams that will be discovered by the Gaia mission to determine the gravitational potential of our Galaxy.
Energy Technology Data Exchange (ETDEWEB)
Li, Yu-Bin; Cai, Yi-Fu [CAS Key Laboratory for Researches in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026 (China); Quintin, Jerome [Department of Physics, McGill University, 3600 rue University, Montréal, QC, H3A 2T8 (Canada); Wang, Dong-Gang, E-mail: lyb2166@mail.ustc.edu.cn, E-mail: jquintin@physics.mcgill.ca, E-mail: wdgang@strw.leidenuniv.nl, E-mail: yifucai@ustc.edu.cn [Leiden Observatory, Leiden University, 2300 RA Leiden (Netherlands)
2017-03-01
We extend the matter bounce scenario to a more general theory in which the background dynamics and cosmological perturbations are generated by a k -essence scalar field with an arbitrary sound speed. When the sound speed is small, the curvature perturbation is enhanced, and the tensor-to-scalar ratio, which is excessively large in the original model, can be sufficiently suppressed to be consistent with observational bounds. Then, we study the primordial three-point correlation function generated during the matter-dominated contraction stage and find that it only depends on the sound speed parameter. Similar to the canonical case, the shape of the bispectrum is mainly dominated by a local form, though for some specific sound speed values a new shape emerges and the scaling behaviour changes. Meanwhile, a small sound speed also results in a large amplitude of non-Gaussianities, which is disfavored by current observations. As a result, it does not seem possible to suppress the tensor-to-scalar ratio without amplifying the production of non-Gaussianities beyond current observational constraints (and vice versa). This suggests an extension of the previously conjectured no-go theorem in single field nonsingular matter bounce cosmologies, which rules out a large class of models. However, the non-Gaussianity results remain as a distinguishable signature of matter bounce cosmology and have the potential to be detected by observations in the near future.
arXiv Falsifying cosmological models based on a non-linear electrodynamics
Övgün, Ali; Magaña, Juan; Jusufi, Kimet
Recently, the nonlinear electrodynamics (NED) has been gaining attention to generate primordial magnetic fields in the Universe and also to resolve singularity problems. Moreover, recent works have shown the crucial role of the NED on the inflation. This paper provides a new approach based on a new model of NED as a source of gravitation to remove the cosmic singularity at the big bang and explain the cosmic acceleration during the inflation era on the background of stochastic magnetic field. Also, we found a realization of a cyclic Universe, free of initial singularity, due to the proposed NED energy density. In addition, we explore whether a NED field without or with matter can be the origin of the late-time acceleration. For this we obtain explicit equations for $H(z)$ and perform a MCMC analysis to constrain the NED parameters by using $31$ observational Hubble data (OHD) obtained from cosmic chronometers covering the redshift range $0 < z < 1.97$; and with the joint-light-analysis (JLA) SNIa compil...
Jones, Bernard J. T.
2017-04-01
Preface; Notation and conventions; Part I. 100 Years of Cosmology: 1. Emerging cosmology; 2. The cosmic expansion; 3. The cosmic microwave background; 4. Recent cosmology; Part II. Newtonian Cosmology: 5. Newtonian cosmology; 6. Dark energy cosmological models; 7. The early universe; 8. The inhomogeneous universe; 9. The inflationary universe; Part III. Relativistic Cosmology: 10. Minkowski space; 11. The energy momentum tensor; 12. General relativity; 13. Space-time geometry and calculus; 14. The Einstein field equations; 15. Solutions of the Einstein equations; 16. The Robertson-Walker solution; 17. Congruences, curvature and Raychaudhuri; 18. Observing and measuring the universe; Part IV. The Physics of Matter and Radiation: 19. Physics of the CMB radiation; 20. Recombination of the primeval plasma; 21. CMB polarisation; 22. CMB anisotropy; Part V. Precision Tools for Precision Cosmology: 23. Likelihood; 24. Frequentist hypothesis testing; 25. Statistical inference: Bayesian; 26. CMB data processing; 27. Parametrising the universe; 28. Precision cosmology; 29. Epilogue; Appendix A. SI, CGS and Planck units; Appendix B. Magnitudes and distances; Appendix C. Representing vectors and tensors; Appendix D. The electromagnetic field; Appendix E. Statistical distributions; Appendix F. Functions on a sphere; Appendix G. Acknowledgements; References; Index.
Exact Solution and Exotic Fluid in Cosmology
Directory of Open Access Journals (Sweden)
Phillial Oh
2012-09-01
Full Text Available We investigate cosmological consequences of nonlinear sigma model coupled with a cosmological fluid which satisfies the continuity equation. The target space action is of the de Sitter type and is composed of four scalar fields. The potential which is a function of only one of the scalar fields is also introduced. We perform a general analysis of the ensuing cosmological equations and give various critical points and their properties. Then, we show that the model exhibits an exact cosmological solution which yields a transition from matter domination into dark energy epoch and compare it with the Λ-CDM behavior. Especially, we calculate the age of the Universe and show that it is consistent with the observational value if the equation of the state ωf of the cosmological fluid is within the range of 0.13 < ωf < 0.22. Some implication of this result is also discussed.
Weak lensing cosmology beyond ΛCDM
International Nuclear Information System (INIS)
Das, Sudeep; Linder, Eric V.; Nakajima, Reiko; Putter, Roland de
2012-01-01
Weak gravitational lensing is one of the key probes of the cosmological model, dark energy, and dark matter, providing insight into both the cosmic expansion history and large scale structure growth history. Taking into account a broad spectrum of physics affecting growth — dynamical dark energy, extended gravity, neutrino masses, and spatial curvature — we analyze the cosmological constraints. Similarly we consider the effects of a range of systematic uncertainties, in shear measurement, photometric redshifts, intrinsic alignments, and the nonlinear power spectrum, on cosmological parameter extraction. We also investigate, and provide fitting formulas for, the influence of survey parameters such as redshift depth, galaxy number densities, and sky area on the cosmological constraints in the beyond-ΛCDM parameter space. Finally, we examine the robustness of results for different fiducial cosmologies
Energy Technology Data Exchange (ETDEWEB)
Zhang Yuanzhong
2002-06-21
This book is one of a series in the areas of high-energy physics, cosmology and gravitation published by the Institute of Physics. It includes courses given at a doctoral school on 'Relativistic Cosmology: Theory and Observation' held in Spring 2000 at the Centre for Scientific Culture 'Alessandro Volta', Italy, sponsored by SIGRAV-Societa Italiana di Relativita e Gravitazione (Italian Society of Relativity and Gravitation) and the University of Insubria. This book collects 15 review reports given by a number of outstanding scientists. They touch upon the main aspects of modern cosmology from observational matters to theoretical models, such as cosmological models, the early universe, dark matter and dark energy, modern observational cosmology, cosmic microwave background, gravitational lensing, and numerical simulations in cosmology. In particular, the introduction to the basics of cosmology includes the basic equations, covariant and tetrad descriptions, Friedmann models, observation and horizons, etc. The chapters on the early universe involve inflationary theories, particle physics in the early universe, and the creation of matter in the universe. The chapters on dark matter (DM) deal with experimental evidence of DM, neutrino oscillations, DM candidates in supersymmetry models and supergravity, structure formation in the universe, dark-matter search with innovative techniques, and dark energy (cosmological constant), etc. The chapters about structure in the universe consist of the basis for structure formation, quantifying large-scale structure, cosmic background fluctuation, galaxy space distribution, and the clustering of galaxies. In the field of modern observational cosmology, galaxy surveys and cluster surveys are given. The chapter on gravitational lensing describes the lens basics and models, galactic microlensing and galaxy clusters as lenses. The last chapter, 'Numerical simulations in cosmology', deals with spatial and
Directory of Open Access Journals (Sweden)
Pierluigi Monaco
2016-10-01
Full Text Available Precision cosmology has recently triggered new attention on the topic of approximate methods for the clustering of matter on large scales, whose foundations date back to the period from the late 1960s to early 1990s. Indeed, although the prospect of reaching sub-percent accuracy in the measurement of clustering poses a challenge even to full N-body simulations, an accurate estimation of the covariance matrix of clustering statistics, not to mention the sampling of parameter space, requires usage of a large number (hundreds in the most favourable cases of simulated (mock galaxy catalogs. Combination of few N-body simulations with a large number of realizations performed with approximate methods gives the most promising approach to solve these problems with a reasonable amount of resources. In this paper I review this topic, starting from the foundations of the methods, then going through the pioneering efforts of the 1990s, and finally presenting the latest extensions and a few codes that are now being used in present-generation surveys and thoroughly tested to assess their performance in the context of future surveys.
Dark matter direct detection signals inferred from a cosmological N-body simulation with baryons
International Nuclear Information System (INIS)
Ling, F.-S.; Nezri, E.; Athanassoula, E.; Teyssier, R.
2010-01-01
We extract at redshift z = 0 a Milky Way sized object including gas, stars and dark matter (DM) from a recent, high-resolution cosmological N-body simulation with baryons. Its resolution is sufficient to witness the formation of a rotating disk and bulge at the center of the halo potential, therefore providing a realistic description of the birth and the evolution of galactic structures in the ΛCDM cosmology paradigm. The phase-space structure of the central galaxy reveals that, throughout a thick region, the dark halo is co-rotating on average with the stellar disk. At the Earth's location, the rotating component, sometimes called dark disk in the literature, is characterized by a minimum lag velocity v lag ≅ 75 km/s, in which case it contributes to around 25% of the total DM local density, whose value is ρ DM ≅ 0.37GeV/cm 3 . The velocity distributions also show strong deviations from pure Gaussian and Maxwellian distributions, with a sharper drop of the high velocity tail. We give a detailed study of the impact of these features on the predictions for DM signals in direct detection experiments. In particular, the question of whether the modulation signal observed by DAMA is or is not excluded by limits set by other experiments (CDMS, XENON and CRESST...) is re-analyzed and compared to the case of a standard Maxwellian halo. We consider spin-independent interactions for both the elastic and the inelastic scattering scenarios. For the first time, we calculate the allowed regions for DAMA and the exclusion limits of other null experiments directly from the velocity distributions found in the simulation. We then compare these results with the predictions of various analytical distributions. We find that the compatibility between DAMA and the other experiments is improved. In the elastic scenario, the DAMA modulation signal is slightly enhanced in the so-called channeling region, as a result of several effects that include a departure from a Maxwellian
Matter and spirit in the universe scientific and religious preludes to modern cosmology
Kragh, Helge
2004-01-01
Cosmology is an unusual science with an unusual history. This bookexamines the formative years of modern cosmology from the perspectiveof its interaction with religious thought. As the first study of itskind, it reveals how closely associated the development of cosmologyhas been with considerations of a philosophical and religiousnature.
Stompor, Radoslaw; Gorski, Krzysztof M.
1994-01-01
We obtain predictions for cosmic microwave background anisotropies at angular scales near 1 deg in the context of cold dark matter models with a nonzero cosmological constant, normalized to the Cosmic Background Explorer (COBE) Differential Microwave Radiometer (DMR) detection. The results are compared to those computed in the matter-dominated models. We show that the coherence length of the Cosmic Microwave Background (CMB) anisotropy is almost insensitive to cosmological parameters, and the rms amplitude of the anisotropy increases moderately with decreasing total matter density, while being most sensitive to the baryon abundance. We apply these results in the statistical analysis of the published data from the UCSB South Pole (SP) experiment (Gaier et al. 1992; Schuster et al. 1993). We reject most of the Cold Dark Matter (CDM)-Lambda models at the 95% confidence level when both SP scans are simulated together (although the combined data set renders less stringent limits than the Gaier et al. data alone). However, the Schuster et al. data considered alone as well as the results of some other recent experiments (MAX, MSAM, Saskatoon), suggest that typical temperature fluctuations on degree scales may be larger than is indicated by the Gaier et al. scan. If so, CDM-Lambda models may indeed provide, from a point of view of CMB anisotropies, an acceptable alternative to flat CDM models.
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Niedermann, Florian; Schneider, Robert
2015-01-01
We derive the modified Friedmann equations for a generalization of the Dvali-Gabadadze-Porrati (DGP) model in which the brane has one additional compact dimension. The main new feature is the emission of gravitational waves into the bulk. We study two classes of solutions: first, if the compact dimension is stabilized, the waves vanish and one exactly recovers DGP cosmology. However, a stabilization by means of physical matter is not possible for a tension-dominated brane, thus implying a late time modification of 4D cosmology different from DGP. Second, for a freely expanding compact direction, we find exact attractor solutions with zero 4D Hubble parameter despite the presence of a 4D cosmological constant. The model hence constitutes an explicit example of dynamical degravitation at the full nonlinear level. Without stabilization, however, there is no 4D regime and the model is ruled out observationally, as we demonstrate explicitly by comparing to supernova data
A fresh look at linear cosmological constraints on a decaying Dark Matter component
Energy Technology Data Exchange (ETDEWEB)
Poulin, Vivian; Serpico, Pasquale D. [LAPTh, Université Savoie Mont Blanc and CNRS, BP 110, Annecy-le-Vieux Cedex, F-74941 France (France); Lesgourgues, Julien, E-mail: Vivian.Poulin@lapth.cnrs.fr, E-mail: Pasquale.Serpico@lapth.cnrs.fr, E-mail: Julien.Lesgourgues@physik.rwth-aachen.de [Institute for Theoretical Particle Physics and Cosmology (TTK), RWTH Aachen University, Sommerfeld str. 16, Aachen, D-52056 Germany (Germany)
2016-08-01
We consider a cosmological model in which a fraction f {sub dcdm} of the Dark Matter (DM) is allowed to decay in an invisible relativistic component, and compute the resulting constraints on both the decay width (or inverse lifetime) Γ{sub dcdm} and f {sub dcdm} from purely gravitational arguments. We report a full derivation of the Boltzmann hierarchy, correcting a mistake in previous literature, and compute the impact of the decay—as a function of the lifetime—on the CMB and matter power spectra. From CMB only, we obtain that no more than 3.8% of the DM could have decayed in the time between recombination and today (all bounds quoted at 95% CL). We also comment on the important application of this bound to the case where primordial black holes constitute DM, a scenario notoriously difficult to constrain. For lifetimes longer than the age of the Universe, the bounds can be cast as f {sub dcdm}Γ{sub dcdm} < 6.3×10{sup -3} Gyr{sup -1}. For the first time, we also checked that degeneracies with massive neutrinos are broken when information from the large scale structure is used. Even secondary effects like CMB lensing suffice to this purpose. Decaying DM models have been invoked to solve a possible tension between low redshift astronomical measurements of σ{sub 8} and Ω{sub m} and the ones inferred by Planck. We reassess this claim finding that with the most recent BAO, HST and σ{sub 8} data extracted from the CFHT survey, the tension is only slightly reduced despite the two additional free parameters. Nonetheless, the existing tension explains why the bound on f {sub dcdm}Γ{sub dcdm} loosens to f {sub dcdm}Γ{sub dcdm} < 15.9×10{sup -3} Gyr{sup -1} when including such additional data. The bound however improves to f {sub dcdm}Γ{sub dcdm} < 5.9 ×10{sup -3} Gyr{sup -1} if only data consistent with the CMB are included. This highlights the importance of establishing whether the tension is due to real physical effects or unaccounted systematics, for
International Nuclear Information System (INIS)
Kajino, T.; Ichiki, F.K.; Garnavich, P.M.; Mathews, G.J.; Yahiro, M.
2005-01-01
A massive cold dark matter particle is likely to disappear when it is quantized in a Randall-Sundrum noncompact higher dimensional AdS 5 spacetime. To distinguish disappearance of our dark matter particle from the previous decaying particles, we refer to it as disappearing cold dark matter (DCDM). We look for cosmological evidence for this new paradigm and show that this new model is consistent with all data at the 95% C.L., satisfying all sorts of presently available observational constraints from the redshift-luminosity relation of Type Ia supernovae, the mass-to-light ratios of galaxy clusters, and the power spectrum of cosmic microwave background [Phys. Rev. D 68 (2003) 083518
International Nuclear Information System (INIS)
Khalatnikov, I.M.; Belinskij, V.A.
1984-01-01
Application of the qualitative theory of dynamic systems to analysis of homogeneous cosmological models is described. Together with the well-known cases, requiring ideal liquid, the properties of cosmological evolution of matter with dissipative processes due to viscosity are considered. New cosmological effects occur, when viscosity terms being one and the same order with the rest terms in the equations of gravitation or even exceeding them. In these cases the description of the dissipative process by means of only two viscosity coefficients (volume and shift) may become inapplicable because all the rest decomposition terms of dissipative addition to the energy-momentum in velocity gradient can be large application of equations with hydrodynamic viscosty should be considered as a model of dissipative effects in cosmology
Scalar-tensor cosmology with cosmological constant
International Nuclear Information System (INIS)
Maslanka, K.
1983-01-01
The equations of scalar-tensor theory of gravitation with cosmological constant in the case of homogeneous and isotropic cosmological model can be reduced to dynamical system of three differential equations with unknown functions H=R/R, THETA=phi/phi, S=e/phi. When new variables are introduced the system becomes more symmetrical and cosmological solutions R(t), phi(t), e(t) are found. It is shown that when cosmological constant is introduced large class of solutions which depend also on Dicke-Brans parameter can be obtained. Investigations of these solutions give general limits for cosmological constant and mean density of matter in plane model. (author)
Cosmology and particle physics
International Nuclear Information System (INIS)
Turner, M.S.
1985-01-01
The author reviews the standard cosmology, focusing on primordial nucleosynthesis, and discusses how the standard cosmology has been used to place constraints on the properties of various particles. Baryogenesis is examined in which the B, C, CP violating interactions in GUTs provide a dynamical explanation for the predominance of matter over antimatter and the present baryon-to-baryon ratio. Monoposes, cosmology and astrophysics are reviewed. The author also discusses supersymmetry/supergravity and cosmology, superstrings and cosmology in extra dimensions, and axions, astrophics, and cosmology
A whirling plane of satellite galaxies around Centaurus A challenges cold dark matter cosmology.
Müller, Oliver; Pawlowski, Marcel S; Jerjen, Helmut; Lelli, Federico
2018-02-02
The Milky Way and Andromeda galaxies are each surrounded by a thin plane of satellite dwarf galaxies that may be corotating. Cosmological simulations predict that most satellite galaxy systems are close to isotropic with random motions, so those two well-studied systems are often interpreted as rare statistical outliers. We test this assumption using the kinematics of satellite galaxies around the Centaurus A galaxy. Our statistical analysis reveals evidence for corotation in a narrow plane: Of the 16 Centaurus A satellites with kinematic data, 14 follow a coherent velocity pattern aligned with the long axis of their spatial distribution. In standard cosmological simulations, cosmological paradigm. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.
Sanders, Robert H
2016-01-01
The advent of sensitive high-resolution observations of the cosmic microwave background radiation and their successful interpretation in terms of the standard cosmological model has led to great confidence in this model's reality. The prevailing attitude is that we now understand the Universe and need only work out the details. In this book, Sanders traces the development and successes of Lambda-CDM, and argues that this triumphalism may be premature. The model's two major components, dark energy and dark matter, have the character of the pre-twentieth-century luminiferous aether. While there is astronomical evidence for these hypothetical fluids, their enigmatic properties call into question our assumptions of the universality of locally determined physical law. Sanders explains how modified Newtonian dynamics (MOND) is a significant challenge for cold dark matter. Overall, the message is hopeful: the field of cosmology has not become frozen, and there is much fundamental work ahead for tomorrow's cosmologis...
Lucio Rapoport, Diego
2013-04-01
We present a unified principle for science that surmounts dualism, in terms of torsion fields and the non-orientable surfaces, notably the Klein Bottle and its logic, the Möbius strip and the projective plane. We apply it to the complex numbers and cosmology, to non-linear systems integrating the issue of hyperbolic divergences with the change of orientability, to the biomechanics of vision and the mammal heart, to the morphogenesis of crustal shapes on Earth in connection to the wavefronts of gravitation, elasticity and electromagnetism, to pattern recognition of artificial images and visual recognition, to neurology and the topographic maps of the sensorium, to perception, in particular of music. We develop it in terms of the fundamental 2:1 resonance inherent to the Möbius strip and the Klein Bottle, the minimal surfaces representation of the wavefronts, and the non-dual Klein Bottle logic inherent to pattern recognition, to the harmonic functions and vector fields that lay at the basis of geophysics and physics at large. We discuss the relation between the topographic maps of the sensorium, and the issue of turning inside-out of the visual world as a general principle for cognition, topological chemistry, cell biology and biological morphogenesis in particular in embryology
International Nuclear Information System (INIS)
Rapoport, Diego Lucio
2013-01-01
We present a unified principle for science that surmounts dualism, in terms of torsion fields and the non-orientable surfaces, notably the Klein Bottle and its logic, the Möbius strip and the projective plane. We apply it to the complex numbers and cosmology, to non-linear systems integrating the issue of hyperbolic divergences with the change of orientability, to the biomechanics of vision and the mammal heart, to the morphogenesis of crustal shapes on Earth in connection to the wavefronts of gravitation, elasticity and electromagnetism, to pattern recognition of artificial images and visual recognition, to neurology and the topographic maps of the sensorium, to perception, in particular of music. We develop it in terms of the fundamental 2:1 resonance inherent to the Möbius strip and the Klein Bottle, the minimal surfaces representation of the wavefronts, and the non-dual Klein Bottle logic inherent to pattern recognition, to the harmonic functions and vector fields that lay at the basis of geophysics and physics at large. We discuss the relation between the topographic maps of the sensorium, and the issue of turning inside-out of the visual world as a general principle for cognition, topological chemistry, cell biology and biological morphogenesis in particular in embryology
International Nuclear Information System (INIS)
Stecker, F.W.
1989-01-01
This paper discusses two aspects of antimatter and cosmology: 1. the fundamental cosmological question as to whether antimatter plays an equally important role as matter in the universe (overall baryon symmetry), and 2. cosmic-ray antimatter tests for the nature of the dark matter in the universe. (orig.)
How robust are inflation model and dark matter constraints from cosmological data?
DEFF Research Database (Denmark)
Hamann, Jan; Hannestad, Steen; Sloth, Martin Snoager
2006-01-01
the tensor-to-scalar ratio r and the neutrino mass prevents lambda phi^4 from being excluded by present data. Reversing the argument, if lambda phi^4 is the correct model of inflation, it predicts a sum of neutrino masses at 0.3-0.5 eV, a range compatible with present experimental limits and within the reach......High-precision data from observation of the cosmic microwave background and the large scale structure of the universe provide very tight constraints on the effective parameters that describe cosmological inflation. Indeed, within a constrained class of LambdaCDM models, the simple lambda phi^4...... chaotic inflation model already appears to be ruled out by cosmological data. In this paper, we compute constraints on inflationary parameters within a more general framework that includes other physically motivated parameters such as a nonzero neutrino mass. We find that a strong degeneracy between...
Testing dark energy and dark matter cosmological models with clusters of galaxies
Energy Technology Data Exchange (ETDEWEB)
Boehringer, Hans [Max-Planck-Institut fuer Extraterrestrische Physik, Garching (Germany)
2008-07-01
Galaxy clusters are, as the largest building blocks of our Universe, ideal probes to study the large-scale structure and to test cosmological models. The principle approach und the status of this research is reviewed. Clusters lend themselves for tests in serveral ways: the cluster mass function, the spatial clustering, the evolution of both functions with reshift, and the internal composition can be used to constrain cosmological parameters. X-ray observations are currently the best means of obtaining the relevant data on the galaxy cluster population. We illustrate in particular all the above mentioned methods with our ROSAT based cluster surveys. The mass calibration of clusters is an important issue, that is currently solved with XMM-Newton and Chandra studies. Based on the current experience we provide an outlook for future research, especially with eROSITA.
Linear and non-linear optics of condensed matter
International Nuclear Information System (INIS)
McLean, T.P.
1977-01-01
Part I - Linear optics: 1. General introduction. 2. Frequency dependence of epsilon(ω, k vector). 3. Wave-vector dependence of epsilon(ω, k vector). 4. Tensor character of epsilon(ω, k vector). Part II - Non-linear optics: 5. Introduction. 6. A classical theory of non-linear response in one dimension. 7. The generalization to three dimensions. 8. General properties of the polarizability tensors. 9. The phase-matching condition. 10. Propagation in a non-linear dielectric. 11. Second harmonic generation. 12. Coupling of three waves. 13. Materials and their non-linearities. 14. Processes involving energy exchange with the medium. 15. Two-photon absorption. 16. Stimulated Raman effect. 17. Electro-optic effects. 18. Limitations of the approach presented here. (author)
Ageing of the nonlinear optical susceptibility in soft matter
International Nuclear Information System (INIS)
Ghofraniha, N; Conti, C; Leonardo, R Di; Ruzicka, B; Ruocco, G
2007-01-01
We investigate the nonlinear optics response of a colloidal dispersion undergoing dynamics slowing down with age, by using Z-scan and dynamic light scattering measurements. We study the high optical nonlinearity of an organic dye (rhodamine B) dispersed in a water-clay (laponite) suspension. We consider different clay concentrations (2.0-2.6 wt%) experiencing dynamics arrest. We find that (i) the concentration dependent exponential growth of both mean relaxation time and nonlinear absorption coefficient can be individually scaled to a master curve and (ii) the scaling times are the same for the two physical quantities. These findings indicate that the optical nonlinear susceptibility exhibits the same ageing universal scaling behaviour, typical of disordered out of equilibrium systems
Rajantie, Arttu
2018-03-06
The discovery of the Higgs boson in 2012 and other results from the Large Hadron Collider have confirmed the standard model of particle physics as the correct theory of elementary particles and their interactions up to energies of several TeV. Remarkably, the theory may even remain valid all the way to the Planck scale of quantum gravity, and therefore it provides a solid theoretical basis for describing the early Universe. Furthermore, the Higgs field itself has unique properties that may have allowed it to play a central role in the evolution of the Universe, from inflation to cosmological phase transitions and the origin of both baryonic and dark matter, and possibly to determine its ultimate fate through the electroweak vacuum instability. These connections between particle physics and cosmology have given rise to a new and growing field of Higgs cosmology, which promises to shed new light on some of the most puzzling questions about the Universe as new data from particle physics experiments and cosmological observations become available.This article is part of the Theo Murphy meeting issue 'Higgs cosmology'. © 2018 The Author(s).
International Nuclear Information System (INIS)
Wesson, P.S.
1979-01-01
The Cosmological Principle states: the universe looks the same to all observers regardless of where they are located. To most astronomers today the Cosmological Principle means the universe looks the same to all observers because density of the galaxies is the same in all places. A new Cosmological Principle is proposed. It is called the Dimensional Cosmological Principle. It uses the properties of matter in the universe: density (rho), pressure (p), and mass (m) within some region of space of length (l). The laws of physics require incorporation of constants for gravity (G) and the speed of light (C). After combining the six parameters into dimensionless numbers, the best choices are: 8πGl 2 rho/c 2 , 8πGl 2 rho/c 4 , and 2 Gm/c 2 l (the Schwarzchild factor). The Dimensional Cosmological Principal came about because old ideas conflicted with the rapidly-growing body of observational evidence indicating that galaxies in the universe have a clumpy rather than uniform distribution
Rajantie, Arttu
2018-01-01
The discovery of the Higgs boson in 2012 and other results from the Large Hadron Collider have confirmed the standard model of particle physics as the correct theory of elementary particles and their interactions up to energies of several TeV. Remarkably, the theory may even remain valid all the way to the Planck scale of quantum gravity, and therefore it provides a solid theoretical basis for describing the early Universe. Furthermore, the Higgs field itself has unique properties that may have allowed it to play a central role in the evolution of the Universe, from inflation to cosmological phase transitions and the origin of both baryonic and dark matter, and possibly to determine its ultimate fate through the electroweak vacuum instability. These connections between particle physics and cosmology have given rise to a new and growing field of Higgs cosmology, which promises to shed new light on some of the most puzzling questions about the Universe as new data from particle physics experiments and cosmological observations become available. This article is part of the Theo Murphy meeting issue `Higgs cosmology'.
Martins, C J A P
2016-01-01
This book sheds new light on topological defects in widely differing systems, using the Velocity-Dependent One-Scale Model to better understand their evolution. Topological defects – cosmic strings, monopoles, domain walls or others - necessarily form at cosmological (and condensed matter) phase transitions. If they are stable and long-lived they will be fossil relics of higher-energy physics. Understanding their behaviour and consequences is a key part of any serious attempt to understand the universe, and this requires modelling their evolution. The velocity-dependent one-scale model is the only fully quantitative model of defect network evolution, and the canonical model in the field. This book provides a review of the model, explaining its physical content and describing its broad range of applicability.
International Nuclear Information System (INIS)
Chow, Nathan; Khoury, Justin
2009-01-01
We study the cosmology of a galileon scalar-tensor theory, obtained by covariantizing the decoupling Lagrangian of the Dvali-Gabadadze-Poratti (DGP) model. Despite being local in 3+1 dimensions, the resulting cosmological evolution is remarkably similar to that of the full 4+1-dimensional DGP framework, both for the expansion history and the evolution of density perturbations. As in the DGP model, the covariant galileon theory yields two branches of solutions, depending on the sign of the galileon velocity. Perturbations are stable on one branch and ghostlike on the other. An interesting effect uncovered in our analysis is a cosmological version of the Vainshtein screening mechanism: at early times, the galileon dynamics are dominated by self-interaction terms, resulting in its energy density being suppressed compared to matter or radiation; once the matter density has redshifted sufficiently, the galileon becomes an important component of the energy density and contributes to dark energy. We estimate conservatively that the resulting expansion history is consistent with the observed late-time cosmology, provided that the scale of modification satisfies r c > or approx. 15 Gpc.
International Nuclear Information System (INIS)
Feng, Jonathan L.
2005-01-01
Cosmology now provides unambiguous, quantitative evidence for new particle physics. I discuss the implications of cosmology for supersymmetry and vice versa. Topics include: motivations for supersymmetry; supersymmetry breaking; dark energy; freeze out and WIMPs; neutralino dark matter; cosmologically preferred regions of minimal supergravity; direct and indirect detection of neutralinos; the DAMA and HEAT signals; inflation and reheating; gravitino dark matter; Big Bang nucleosynthesis; and the cosmic microwave background. I conclude with speculations about the prospects for a microscopic description of the dark universe, stressing the necessity of diverse experiments on both sides of the particle physics/cosmology interface
Small scale structure formation in chameleon cosmology
International Nuclear Information System (INIS)
Brax, Ph.; Bruck, C. van de; Davis, A.C.; Green, A.M.
2006-01-01
Chameleon fields are scalar fields whose mass depends on the ambient matter density. We investigate the effects of these fields on the growth of density perturbations on sub-galactic scales and the formation of the first dark matter halos. Density perturbations on comoving scales R<1 pc go non-linear and collapse to form structure much earlier than in standard ΛCDM cosmology. The resulting mini-halos are hence more dense and resilient to disruption. We therefore expect (provided that the density perturbations on these scales have not been erased by damping processes) that the dark matter distribution on small scales would be more clumpy in chameleon cosmology than in the ΛCDM model
Weak nonlinear matter waves in a trapped two-component Bose-Einstein condensates
International Nuclear Information System (INIS)
Yong Wenmei; Xue Jukui
2008-01-01
The dynamics of the weak nonlinear matter solitary waves in two-component Bose-Einstein condensates (BEC) with cigar-shaped external potential are investigated analytically by a perturbation method. In the small amplitude limit, the two-components can be decoupled and the dynamics of solitary waves are governed by a variable-coefficient Korteweg-de Vries (KdV) equation. The reduction to the KdV equation may be useful to understand the dynamics of nonlinear matter waves in two-component BEC. The analytical expressions for the evolution of soliton, emitted radiation profiles and soliton oscillation frequency are also obtained
Relativistic nonlinear electrodynamics the QED vacuum and matter in super-strong radiation fields
Avetissian, Hamlet K
2016-01-01
This revised edition of the author’s classic 2006 text offers a comprehensively updated review of the field of relativistic nonlinear electrodynamics. It explores the interaction of strong and super-strong electromagnetic/laser radiation with the electromagnetic quantum vacuum and diverse types of matter – including free charged particles and antiparticles, acceleration beams, plasma and plasmous media. The appearance of laser sources of relativistic and ultra-relativistic intensities over the last decade has stimulated investigation of a large class of processes under such super-strong radiation fields. Revisions for this second edition reflect these developments and the book includes new chapters on Bremsstrahlung and nonlinear absorption of superintense radiation in plasmas, the nonlinear interaction of relativistic atoms with intense laser radiation, nonlinear interaction of strong laser radiation with Graphene, and relativistic nonlinear phenomena in solid-plasma targets under supershort laser pul...
Bardeen, J. M.
The last several years have seen a tremendous ferment of activity in astrophysical cosmology. Much of the theoretical impetus has come from particle physics theories of the early universe and candidates for dark matter, but what promise to be even more significant are improved direct observations of high z galaxies and intergalactic matter, deeper and more comprehensive redshift surveys, and the increasing power of computer simulations of the dynamical evolution of large scale structure. Upper limits on the anisotropy of the microwave background radiation are gradually getting tighter and constraining more severely theoretical scenarios for the evolution of the universe.
International Nuclear Information System (INIS)
Bardeen, J.M.
1986-01-01
The last several years have seen a tremendous ferment of activity in astrophysical cosmology. Much of the theoretical impetus has come from particle physics theories of the early universe and candidates for dark matter, but what promise to be even more significant are improved direct observations of high z galaxies and intergalactic matter, deeper and more comprehensive redshift surveys, and the increasing power of computer simulations of the dynamical evolution of large scale structure. Upper limits on the anisotropy of the microwave background radiation are gradually getting tighter and constraining more severely theoretical scenarios for the evolution of the universe. 47 refs
Boeyens, Jan CA
2010-01-01
The composition of the most remote objects brought into view by the Hubble telescope can no longer be reconciled with the nucleogenesis of standard cosmology and the alternative explanation, in terms of the LAMBDA-Cold-Dark-Matter model, has no recognizable chemical basis. A more rational scheme, based on the chemistry and periodicity of atomic matter, opens up an exciting new interpretation of the cosmos in terms of projective geometry and general relativity. The response of atomic structure to environmental pressure predicts non-Doppler cosmical redshifts and equilibrium nucleogenesis by alp
A three-dimensional hydrodynamic treatment of the hot dark matter cosmological scenario
Cen, Renyue; Ostriker, Jeremiah P.
1992-01-01
The study computes the evolution of the hot dark matter (HDM) model containing both baryonic matter and dark matter for a post recombination Friedmann-Robertson-Walker universe. A locally valid Newtonian approximation is used to model a representative piece of the universe with size much less than the horizon. For the HDM model with the present chosen normalization, the hard X-ray (1-10 keV) radiation intensity is less than that in the observations (Wu et al., 1991) by a factor of 30. In agreement with other work, it is found that baryonic matter is slightly antibiased over dark matter on the cell scale, 0.5/h Mpc = 667 kpc. The HDM model with the present chosen parameters does not overproduce X-ray-luminous clusters, and there is a negative evolution in the late epochs in the sense that the number density of X-ray clusters was higher at 0.5 redshift than at 0 redshift at the brightest end.
International Nuclear Information System (INIS)
Ellis, Richard S.
2008-01-01
This program is concerned with developing and verifying the validity of observational methods for constraining the properties of dark matter and dark energy in the universe. Excellent progress has been made in comparing observational projects involving weak gravitational lensing using both ground and space-based instruments, in further constraining the nature of dark matter via precise measures of its distribution in clusters of galaxies using strong gravitational lensing, in demonstrating the possible limitations of using distant supernovae in future dark energy missions, and in investigating the requirement for ground-based surveys of baryonic acoustic oscillations.
Elements of a dialogue between nonlinear models in condensed matter and biophysics
International Nuclear Information System (INIS)
Bishop, A.R.; Lomdahl, P.S.; Kerr, W.C.
1985-01-01
We indicate some of the emerging thematic connections between strongly nonlinear effects in condensed matter and biological materials. These are illustrated with model studies of: (1) structural phase transitions in anisotropic lattices; and (2) finite temperature effects on self-trapped states in vibron-phonon models of α-helix proteins. 13 refs., 8 figs
Ground State of the Universe and the Cosmological Constant. A Nonperturbative Analysis.
Husain, Viqar; Qureshi, Babar
2016-02-12
The physical Hamiltonian of a gravity-matter system depends on the choice of time, with the vacuum naturally identified as its ground state. We study the expanding Universe with scalar field in the volume time gauge. We show that the vacuum energy density computed from the resulting Hamiltonian is a nonlinear function of the cosmological constant and time. This result provides a new perspective on the relation between time, the cosmological constant, and vacuum energy.
Non-linear diffusion and pattern formation in vortex matter
Wijngaarden, Rinke J.; Surdeanu, R.; Huijbregtse, J. M.; Rector, J. H.; Dam, B.; Griessen, R.; Einfeld, J.; Woerdenweber, R.
2000-03-01
Penetration of magnetic flux in YBa_2Cu_3O7 superconducting thin films and crystals in externally applied magnetic fields is visualized with a magneto-optical technique. A variety of flux patterns due to non-linear vortex behavior is observed: 1. Roughening of the flux front^1 with scaling exponents identical to those observed in burning paper^2. Two regimes are found where respectively spatial disorder and temporal disorder dominate. In the latter regime Kardar-Parisi-Zhang behavior is found. 2. Roughening of the flux profile similar to the Oslo model for rice-piles. 3. Fractal penetration of flux^3 with Hausdorff dimension depending on the critical current anisotropy. 4. Penetration as 'flux-rivers'. 5. The occurrence of commensurate and incommensurate channels in films with anti-dots as predicted in numerical simulations by Reichhardt, Olson and Nori^4. By comparison with numerical simulations, it is shown that most of the observed behavior can be explained in terms of non-linear diffusion of vortices. ^1R. Surdeanu, R.J. Wijngaarden, E. Visser, J.M. Huijbregtse, J.H. Rector, B. Dam and R. Griessen, Phys.Rev. Lett. 83 (1999) 2054 ^2J. Maunuksela, M. Myllys, O.-P. Kähkönen, J. Timonen, N. Provatas, M.J. Alava, T. Ala-Nissila, Phys. Rev. Lett. 79, 1515 (1997) ^3R. Surdeanu, R.J. Wijngaarden, B. Dam, J. Rector, R. Griessen, C. Rossel, Z.F. Ren and J.H. Wang, Phys Rev B 58 (1998) 12467 ^4C. Reichhardt, C.J. Olson and F. Nori, Phys. Rev. B 58, 6534 (1998)
Dissipative N-body simulations of the formation of single galaxies in a cold dark-matter cosmology
International Nuclear Information System (INIS)
Ewell, M.W. Jr.
1988-01-01
The details of an N-body code designed specifically to study the collapse of a single protogalaxy are presented. This code uses a spherical harmonic expansion to model the gravity and a sticky-particle algorithm to model the gas physics. It includes external tides and cosmologically realistic boundary conditions. The results of twelve simulations using this code are given. The initial conditions for these runs use mean-density profiles and r.m.s. quadrupoles and tides taken from the CDM power spectrum. The simulations start when the center of the perturbation first goes nonlinear, and continue until a redshift Z ∼ 1-2. The resulting rotation curves are approximately flat out to 100 kpc, but do show some structure. The circular velocity is 200 km/sec around a 3σ peak. The final systems have λ approx-equal .03. The angular momentum per unit mass of the baryons implies disk scale lengths of 1-3 kpc. The tidal forces are strong enough to profoundly influence the collapse geometry. In particular, the usual assumption, that tidal torques produce a system approximately in solid-body rotation, is shown to be seriously in error
Cosmological and astrophysical signatures of dark matter annihilations into pseudo-Goldstone bosons
Energy Technology Data Exchange (ETDEWEB)
Garcia-Cely, Camilo; Ibarra, Alejandro; Molinaro, Emiliano, E-mail: camilo.garcia@tum.de, E-mail: alejandro.ibarra@ph.tum.de, E-mail: emiliano.molinaro@tum.de [Physik-Department T30d, Technische Universität München, James-Franck-Straße, Garching, 85748 (Germany)
2014-02-01
We investigate a model where the dark matter particle is a chiral fermion field charged under a global U(1) symmetry which is assumed to be spontaneously broken, leading to a pseudo-Goldstone boson (PGB). We argue that the dark matter annihilation into PGBs determine the dark matter relic abundance. Besides, we also note that experimental searches for PGBs allow either for a very long lived PGB, with a lifetime much longer than the age of the Universe, or a relatively short lived PGB, with a lifetime shorter than one minute. Hence, two different scenarios arise, producing very different signatures. In the long lived PGB scenario, the PGB might contribute significantly to the radiation energy density of the Universe. On the other hand, in the short lived PGB scenario, and since the decay length is shorter than one parsec, the s-wave annihilation into a PGB and a CP even dark scalar in the Galactic center might lead to an intense box feature in the gamma-ray energy spectrum, provided the PGB decay branching ratio into two photons is sizable. We also analyze the constraints on these two scenarios from thermal production, the Higgs invisible decay width and direct dark matter searches.
Astroparticle physics and cosmology
International Nuclear Information System (INIS)
Senjanovic, G.; Smirnov, A.Yu.; Thompson, G.
2001-01-01
In this volume a wide spectrum of topics of modern astroparticle physics, such as neutrino astrophysics, dark matter of the universe, high energy cosmic rays, topological defects in cosmology, γ-ray bursts, phase transitions at high temperatures, is covered. The articles written by top level experts in the field give a comprehensive view of the state-of-the-art of modern cosmology
Astroparticle physics and cosmology
Energy Technology Data Exchange (ETDEWEB)
Senjanovic, G; Smirnov, A Yu; Thompson, G [eds.
2001-11-15
In this volume a wide spectrum of topics of modern astroparticle physics, such as neutrino astrophysics, dark matter of the universe, high energy cosmic rays, topological defects in cosmology, {gamma}-ray bursts, phase transitions at high temperatures, is covered. The articles written by top level experts in the field give a comprehensive view of the state-of-the-art of modern cosmology.
International Nuclear Information System (INIS)
Somogyi, Gabor; Smith, Robert E.
2010-01-01
We generalize the renormalized perturbation theory (RPT) formalism of Crocce and Scoccimarro [M. Crocce and R. Scoccimarro, Phys. Rev. D 73, 063519 (2006)] to deal with multiple fluids in the Universe and here we present the complete calculations up to the one-loop level in the RPT. We apply this approach to the problem of following the nonlinear evolution of baryon and cold dark matter (CDM) perturbations, evolving from the distinct sets of initial conditions, from the high redshift post-recombination Universe right through to the present day. In current theoretical and numerical models of structure formation, it is standard practice to treat baryons and CDM as an effective single matter fluid--the so-called dark matter only modeling. In this approximation, one uses a weighed sum of late-time baryon and CDM transfer functions to set initial mass fluctuations. In this paper we explore whether this approach can be employed for high precision modeling of structure formation. We show that, even if we only follow the linear evolution, there is a large-scale scale-dependent bias between baryons and CDM for the currently favored WMAP5 ΛCDM model. This time evolving bias is significant (>1%) until the present day, when it is driven towards unity through gravitational relaxation processes. Using the RPT formalism we test this approximation in the nonlinear regime. We show that the nonlinear CDM power spectrum in the two-component fluid differs from that obtained from an effective mean-mass one-component fluid by ∼3% on scales of order k∼0.05h Mpc -1 at z=10, and by ∼0.5% at z=0. However, for the case of the nonlinear evolution of the baryons the situation is worse and we find that the power spectrum is suppressed, relative to the total matter, by ∼15% on scales k∼0.05h Mpc -1 at z=10, and by ∼3%-5% at z=0. Importantly, besides the suppression of the spectrum, the baryonic acoustic oscillation (BAO) features are amplified for baryon and slightly damped for CDM
Somogyi, Gábor; Smith, Robert E.
2010-01-01
We generalize the renormalized perturbation theory (RPT) formalism of Crocce and Scoccimarro [M. Crocce and R. Scoccimarro, Phys. Rev. DPRVDAQ1550-7998 73, 063519 (2006)10.1103/PhysRevD.73.063519] to deal with multiple fluids in the Universe and here we present the complete calculations up to the one-loop level in the RPT. We apply this approach to the problem of following the nonlinear evolution of baryon and cold dark matter (CDM) perturbations, evolving from the distinct sets of initial conditions, from the high redshift post-recombination Universe right through to the present day. In current theoretical and numerical models of structure formation, it is standard practice to treat baryons and CDM as an effective single matter fluid—the so-called dark matter only modeling. In this approximation, one uses a weighed sum of late-time baryon and CDM transfer functions to set initial mass fluctuations. In this paper we explore whether this approach can be employed for high precision modeling of structure formation. We show that, even if we only follow the linear evolution, there is a large-scale scale-dependent bias between baryons and CDM for the currently favored WMAP5 ΛCDM model. This time evolving bias is significant (>1%) until the present day, when it is driven towards unity through gravitational relaxation processes. Using the RPT formalism we test this approximation in the nonlinear regime. We show that the nonlinear CDM power spectrum in the two-component fluid differs from that obtained from an effective mean-mass one-component fluid by ˜3% on scales of order k˜0.05hMpc-1 at z=10, and by ˜0.5% at z=0. However, for the case of the nonlinear evolution of the baryons the situation is worse and we find that the power spectrum is suppressed, relative to the total matter, by ˜15% on scales k˜0.05hMpc-1 at z=10, and by ˜3%-5% at z=0. Importantly, besides the suppression of the spectrum, the baryonic acoustic oscillation (BAO) features are amplified for
Energy Technology Data Exchange (ETDEWEB)
Somogyi, Gabor [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Zurich Univ. (Switzerland). Inst. for Theoretical Physics; Smith, Robert E. [Zurich Univ. (Switzerland). Inst. for Theoretical Physics
2009-10-15
We generalize the ''renormalized'' perturbation theory (RPT) formalism of M. Crocce and R. Scoccimarro (2006) to deal with multiple fluids in the Universe and here we present the complete calculations up to the one-loop level in the RPT. We apply this approach to the problem of following the nonlinear evolution of baryon and cold dark matter (CDM) perturbations, evolving from the distinct sets of initial conditions, from the high redshift post-recombination Universe right through to the present day. In current theoretical and numerical models of structure formation, it is standard practice to treat baryons and CDM as an effective single matter fluid - the so called dark matter only modeling. In this approximation, one uses a weighed sum of late time baryon and CDM transfer functions to set initial mass fluctuations. In this paper we explore whether this approach can be employed for high precision modeling of structure formation. We show that, even if we only follow the linear evolution, there is a large-scale scale-dependent bias between baryons and CDM for the currently favored WMAP5 {lambda}CDM model. This time evolving bias is significant (> 1%) until the present day, when it is driven towards unity through gravitational relaxation processes. Using the RPT formalism we test this approximation in the non-linear regime. We show that the non-linear CDM power spectrum in the 2-component fluid differs from that obtained from an effective mean-mass 1-component fluid by {proportional_to} 3% on scales of order k {proportional_to} 0.05 h Mpc{sup -1} at z = 10, and by {proportional_to} 0.5% at z = 0. However, for the case of the non-linear evolution of the baryons the situation is worse and we find that the power spectrum is suppressed, relative to the total matter, by {proportional_to} 15% on scales k {proportional_to} 0.05 hMpc{sup -1} at z = 10, and by {proportional_to} 3 - 5% at z = 0. Importantly, besides the suppression of the spectrum, the
International Nuclear Information System (INIS)
Ko, P.; Tang, Yong
2014-01-01
We propose an ultraviolet complete theory for cold dark matter (CDM) and sterile neutrinos that can accommodate both cosmological data and neutrino oscillation experiments within 1σ level. We assume a new U(1) X dark gauge symmetry which is broken at ∼O(MeV) scale resulting light dark photon. Such a light mediator for DM's self-scattering and scattering-off sterile neutrinos can resolve three controversies for cold DM on small cosmological scales: cusp vs. core, too-big-to-fail and missing satellites. We can also accommodate ∼O(1) eV scale sterile neutrinos as the hot dark matter (HDM) and can fit some neutrino anomalies from neutrino oscillation experiments within 1σ. Finally, the right amount of HDM can make a sizable contribution to dark radiation, and also helps to reconcile the tension between the data on the tensor-to-scalar ratio reported by Planck and BICEP2 Collaborations
On the behaviour of test matter in the neighbourhood of caustics of homogeneous cosmological models
International Nuclear Information System (INIS)
Paul, H.G.
1983-01-01
Using power asymptotes for the metric of the BIANCHI types I, V, VII 0 , VIII and IX the intensity of geodesic focused scalar test matter is calculated in the neighbourhood of the caustic singularity of these space-time models. In all considered BIANCHI types there is a caustic diffraction with a diffraction field bounded by regions of extinction depending on the structure of the gravitational lense. (author)
A hydrodynamic treatment of the tilted cold dark matter cosmological scenario
Cen, Renyue; Ostriker, Jeremiah P.
1993-01-01
A standard hydrodynamic code coupled with a particle-mesh code is used to compute the evolution of a tilted cold dark matter (TCDM) model containing both baryonic matter and dark matter. Six baryonic species are followed, with allowance for both collisional and radiative ionization in every cell. The mean final Zel'dovich-Sunyaev y parameter is estimated to be (5.4 +/- 2.7) x 10 exp -7, below currently attainable observations, with an rms fluctuation of about (6.0 +/- 3.0) x 10 exp -7 on arcmin scales. The rate of galaxy formation peaks at a relatively late epoch (z is about 0.5). In the case of mass function, the smallest objects are stabilized against collapse by thermal energy: the mass-weighted mass spectrum peaks in the vicinity of 10 exp 9.1 solar masses, with a reasonable fit to the Schechter luminosity function if the baryon mass to blue light ratio is about 4. It is shown that a bias factor of 2 required for the model to be consistent with COBE DMR signals is probably a natural outcome in the present multiple component simulations.
International Nuclear Information System (INIS)
Zavarygin, E O; Ivanchik, A V
2015-01-01
An influence of annihilation and decay of the dark matter particles on the baryon-to-photon ratio has been studied for different cosmological epochs. We consider the different parameter values of the dark matter particles such as mass, annihilation cross section, lifetime and so on. The obtained results are compared with the data which come from the Big Bang nucleosynthesis calculation and from the analysis of the anisotropy of the cosmic microwave background radiation. It has been shown that the modern value of the dark matter density Ω CDM = 0.26 is enough to provide the variation of the baryon-to-photon ratio up to Δη/η ∼ 0.01÷1 for decay of the dark matter particles, but it also leads to an excess of the diffuse gamma ray background. We use the observational data on the diffuse gamma ray background in order to determine our constraints on the model of the dark matter particle decay and on the corresponding variation of the baryon-to-photon ratio: Δη/η ≲ 10 -5 . It has been shown that the variation of the baryon-to-photon ratio caused by the annihilation of the dark matter particles is negligible during the cosmological epochs from Big Bang nucleosynthesis to the present epoch. (paper)
Time in contemporary cosmology
International Nuclear Information System (INIS)
Mavrides, Stamatia
1980-01-01
Cosmological time is defined, as is coordinated universal time against local times of special relativity. The problems of time and matter, age of the universe, Goedel models, arrow of time, are also discussed [fr
International Nuclear Information System (INIS)
Novikov, I.D.
1999-01-01
In this talk a brief survey has been carried out on the development of cosmology from the days Leopold Infeld was active in the field up to the present. Attention in particular is paid to the history of our knowledge of Hubble's expansion, of the cosmological constant, of the average density of matter and its distribution, and of the related issue of possible types of matter in the Universe. (author)
International Nuclear Information System (INIS)
Chimento, L P; Forte, M; Devecchi, F P; Kremer, G M; Ribas, M O; Samojeden, L L
2011-01-01
In this work we review if fermionic sources could be responsible for accelerated periods during the evolution of a FRW universe. In a first attempt, besides the fermionic source, a matter constituent would answer for the decelerated periods. The coupled differential equations that emerge from the field equations are integrated numerically. The self-interaction potential of the fermionic field is considered as a function of the scalar and pseudo-scalar invariants. It is shown that the fermionic field could behave like an inflaton field in the early universe, giving place to a transition to a matter dominated (decelerated) period. In a second formulation we turn our attention to analytical results, specifically using the idea of form-invariance transformations. These transformations can be used for obtaining accelerated cosmologies starting with conventional cosmological models. Here we reconsider the scalar field case and extend the discussion to fermionic fields. Finally we investigate the role of a Dirac field in a Brans-Dicke (BD) context. The results show that this source, in combination with the BD scalar, promote a final eternal accelerated era, after a matter dominated period.
Principles of space-time-matter cosmology, particles and waves in five dimensions
Overduin, James
2018-01-01
This book is a summing up of the prospects for unification between relativity and particle physics based on the extension of Einstein's theory of General Relativity to five dimensions. This subject was first established by Paul Wesson in his previous best-seller, Space-Time-Matter, and discussed from a different perspective in Five-Dimensional Physics, both published by World Scientific in 1999 and 2006 respectively. This third book brings the field up to date and details many new developments and connections to particle theory and wave mechanics in particular. It was in largely finished form at the time of Paul Wesson's untimely death in 2015, and has been completed and expanded by his former student and longtime collaborator, James Overduin.
Cosmological perturbations in the ΛCDM-like limit of a polytropic dark matter model
Kleidis, K.; Spyrou, N. K.
2017-10-01
It has recently been proposed that both dark matter (DM) and dark energy (DE) can be treated as a single component when they are considered in the context of a polytropic DM fluid with thermodynamical content. Depending on only one free parameter, that is, the polytropic exponent, - 0.103 law of conventional statistical physics. As a consequence, peculiar velocities in this model slightly increase instead of being redshifted away by cosmic expansion. This result might comprise a convenient probe of the polytropic DM model with Γ = 0. Even more importantly, however, upon consideration of scale-invariant metric perturbations, the spectrum of their rest-mass density counterparts exhibits an effective power-law dependence on the (physical) wavenumber, kph, of the form kph3+nseff, with the associated scalar spectral index, nseff, being equal to nseff = 0.970. This theoretical value reproduces the corresponding observational Planck result, that is, nsobs = 0.968 ± 0.006.
Exact braneworld cosmology induced from bulk black holes
International Nuclear Information System (INIS)
Gregory, James P; Padilla, Antonio
2002-01-01
We use a new, exact approach in calculating the energy density measured by an observer living on a brane embedded in a charged black-hole spacetime. We find that the bulk Weyl tensor gives rise to nonlinear terms in the energy density and pressure in the FRW equations for the brane. Remarkably, these take exactly the same form as the 'unconventional' terms found in the cosmology of branes embedded in pure AdS, with extra matter living on the brane. Black-hole-driven cosmologies have the benefit that there is no ambiguity in splitting the braneworld energy momentum into tension and additional matter. We propose a new, enlarged relationship between the two descriptions of braneworld cosmology. We also study the exact thermodynamics of the field theory and present a generalized Cardy-Verlinde formula in this set-up
Page, Don N.
2006-01-01
A complete model of the universe needs at least three parts: (1) a complete set of physical variables and dynamical laws for them, (2) the correct solution of the dynamical laws, and (3) the connection with conscious experience. In quantum cosmology, item (2) is the quantum state of the cosmos. Hartle and Hawking have made the `no-boundary' proposal, that the wavefunction of the universe is given by a path integral over all compact Euclidean 4-dimensional geometries and matter fields that hav...
International Nuclear Information System (INIS)
Benisti, D.
2011-01-01
This manuscript provides a theoretical description, sometimes illustrated by experimental results, of several examples of field-matter interaction in various domains of physics, showing how the same basic concepts and theoretical methods may be used in very different physics situations. The issues addressed here are nonlinear field-matter interaction in plasma physics within the framework of classical mechanics (with a particular emphasis on wave-particle interaction), the linear analysis of beam-plasma instabilities in the relativistic regime, and the quantum description of laser-atom interaction, including quantum electrodynamics. Novel methods are systematically introduced in order to solve some very old problems, like the nonlinear counterpart of the Landau damping rate in plasma physics, for example. Moreover, our results directly apply to inertial confinement fusion, laser propagation in an atomic vapor, ion acceleration in a magnetized plasma and the physics of the Reversed Field Pinch for magnetic fusion. (author)
Quantum propagation across cosmological singularities
Gielen, Steffen; Turok, Neil
2017-05-01
The initial singularity is the most troubling feature of the standard cosmology, which quantum effects are hoped to resolve. In this paper, we study quantum cosmology with conformal (Weyl) invariant matter. We show that it is natural to extend the scale factor to negative values, allowing a large, collapsing universe to evolve across a quantum "bounce" into an expanding universe like ours. We compute the Feynman propagator for Friedmann-Robertson-Walker backgrounds exactly, identifying curious pathologies in the case of curved (open or closed) universes. We then include anisotropies, fixing the operator ordering of the quantum Hamiltonian by imposing covariance under field redefinitions and again finding exact solutions. We show how complex classical solutions allow one to circumvent the singularity while maintaining the validity of the semiclassical approximation. The simplest isotropic universes sit on a critical boundary, beyond which there is qualitatively different behavior, with potential for instability. Additional scalars improve the theory's stability. Finally, we study the semiclassical propagation of inhomogeneous perturbations about the flat, isotropic case, at linear and nonlinear order, showing that, at least at this level, there is no particle production across the bounce. These results form the basis for a promising new approach to quantum cosmology and the resolution of the big bang singularity.
High energy physics and cosmology
International Nuclear Information System (INIS)
Silk, J.I.
1991-01-01
This research will focus on the implications of recent theories and experiments in high energy physics of the evolution of the early universe, and on the constraints that cosmological considerations can place on such theories. Several problems are under investigation, including studies of the nature of dark matter and the signature of annihilations in the galactic halo, where the resulting γ-ray fluxes are potentially observable, and in stars, where stellar evolution may be affects. We will develop constraints on the inflationary predictions of scale-free primordial fluctuations in a universe at critical closure density by studying their linear and non-linear evolution after they re-enter the particle horizon, examining the observable imprint of primordial density fluctuations on the cosmic microwave background radiation in both flat and curved cosmological models, and implications for observations of large-scale galaxy clustering and structure formation theories. We will also study spectral distortions in the microwave background radiation that are produced by exotic particle decays in the very early universe. We expect such astrophysical considerations to provide fruitful insights both into high-energy particle physics and into possible cosmological for the early universe
Efficient exploration of cosmology dependence in the EFT of LSS
Energy Technology Data Exchange (ETDEWEB)
Cataneo, Matteo [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen (Denmark); Foreman, Simon; Senatore, Leonardo, E-mail: matteoc@dark-cosmology.dk, E-mail: sfore@stanford.edu, E-mail: senatore@stanford.edu [Stanford Institute for Theoretical Physics and Department of Physics, Stanford University, 382 Via Pueblo Mall, Stanford, CA 94306 (United States)
2017-04-01
The most effective use of data from current and upcoming large scale structure (LSS) and CMB observations requires the ability to predict the clustering of LSS with very high precision. The Effective Field Theory of Large Scale Structure (EFTofLSS) provides an instrument for performing analytical computations of LSS observables with the required precision in the mildly nonlinear regime. In this paper, we develop efficient implementations of these computations that allow for an exploration of their dependence on cosmological parameters. They are based on two ideas. First, once an observable has been computed with high precision for a reference cosmology, for a new cosmology the same can be easily obtained with comparable precision just by adding the difference in that observable, evaluated with much less precision. Second, most cosmologies of interest are sufficiently close to the Planck best-fit cosmology that observables can be obtained from a Taylor expansion around the reference cosmology. These ideas are implemented for the matter power spectrum at two loops and are released as public codes. When applied to cosmologies that are within 3σ of the Planck best-fit model, the first method evaluates the power spectrum in a few minutes on a laptop, with results that have 1% or better precision, while with the Taylor expansion the same quantity is instantly generated with similar precision. The ideas and codes we present may easily be extended for other applications or higher-precision results.
Modified General Relativity and Cosmology
Abdel-Rahman, A.-M. M.
1997-10-01
Aspects of the modified general relativity theory of Rastall, Al-Rawaf and Taha are discussed in both the radiation- and matter-dominated flat cosmological models. A nucleosynthesis constraint on the theory's free parameter is obtained and the implication for the age of the Universe is discussed. The consistency of the modified matter- dominated model with the neoclassical cosmological tests is demonstrated.
Neutrino properties from cosmology
CERN. Geneva
2013-01-01
Future, massive large-scale structure survey have been presented and approved.On the theory side, a significant effort has bene devoted to achieve better modeling of small scale clustering that is of cosmological non-linearities. As a result it has become clear that forthcoming cosmological data have enough statitsical power to detect the effect of non-zero neutrino mass (even at the lower mass scale limit imposed by oscillations) and to constrain the absolute neutrino mass scale.Cosmological data can also constrain the numb...
Nonlinear evolution of the matter power spectrum in modified theories of gravity
International Nuclear Information System (INIS)
Koyama, Kazuya; Taruya, Atsushi; Hiramatsu, Takashi
2009-01-01
We present a formalism to calculate the nonlinear matter power spectrum in modified gravity models that explain the late-time acceleration of the Universe without dark energy. Any successful modified gravity models should contain a mechanism to recover general relativity (GR) on small scales in order to avoid the stringent constrains on deviations from GR at solar system scales. Based on our formalism, the quasi-nonlinear power spectrum in the Dvali-Gabadadze-Porratti braneworld models and f(R) gravity models are derived by taking into account the mechanism to recover GR properly. We also extrapolate our predictions to fully nonlinear scales using the parametrized post-Friedmann framework. In the Dvali-Gabadadze-Porratti and f(R) gravity models, the predicted nonlinear power spectrum is shown to reproduce N-body results. We find that the mechanism to recover GR suppresses the difference between the modified gravity models and dark energy models with the same expansion history, but the difference remains large at the weakly nonlinear regime in these models. Our formalism is applicable to a wide variety of modified gravity models and it is ready to use once consistent models for modified gravity are developed.
Cosmology with weak lensing surveys
International Nuclear Information System (INIS)
Munshi, Dipak; Valageas, Patrick; Waerbeke, Ludovic van; Heavens, Alan
2008-01-01
Weak gravitational lensing is responsible for the shearing and magnification of the images of high-redshift sources due to the presence of intervening matter. The distortions are due to fluctuations in the gravitational potential, and are directly related to the distribution of matter and to the geometry and dynamics of the Universe. As a consequence, weak gravitational lensing offers unique possibilities for probing the Dark Matter and Dark Energy in the Universe. In this review, we summarise the theoretical and observational state of the subject, focussing on the statistical aspects of weak lensing, and consider the prospects for weak lensing surveys in the future. Weak gravitational lensing surveys are complementary to both galaxy surveys and cosmic microwave background (CMB) observations as they probe the unbiased non-linear matter power spectrum at modest redshifts. Most of the cosmological parameters are accurately estimated from CMB and large-scale galaxy surveys, so the focus of attention is shifting to understanding the nature of Dark Matter and Dark Energy. On the theoretical side, recent advances in the use of 3D information of the sources from photometric redshifts promise greater statistical power, and these are further enhanced by the use of statistics beyond two-point quantities such as the power spectrum. The use of 3D information also alleviates difficulties arising from physical effects such as the intrinsic alignment of galaxies, which can mimic weak lensing to some extent. On the observational side, in the next few years weak lensing surveys such as CFHTLS, VST-KIDS and Pan-STARRS, and the planned Dark Energy Survey, will provide the first weak lensing surveys covering very large sky areas and depth. In the long run even more ambitious programmes such as DUNE, the Supernova Anisotropy Probe (SNAP) and Large-aperture Synoptic Survey Telescope (LSST) are planned. Weak lensing of diffuse components such as the CMB and 21 cm emission can also
Cosmology with weak lensing surveys
Energy Technology Data Exchange (ETDEWEB)
Munshi, Dipak [Institute of Astronomy, Madingley Road, Cambridge, CB3 OHA (United Kingdom); Astrophysics Group, Cavendish Laboratory, Madingley Road, Cambridge CB3 OHE (United Kingdom)], E-mail: munshi@ast.cam.ac.uk; Valageas, Patrick [Service de Physique Theorique, CEA Saclay, 91191 Gif-sur-Yvette (France); Waerbeke, Ludovic van [University of British Columbia, Department of Physics and Astronomy, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada); Heavens, Alan [SUPA - Scottish Universities Physics Alliance, Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom)
2008-06-15
Weak gravitational lensing is responsible for the shearing and magnification of the images of high-redshift sources due to the presence of intervening matter. The distortions are due to fluctuations in the gravitational potential, and are directly related to the distribution of matter and to the geometry and dynamics of the Universe. As a consequence, weak gravitational lensing offers unique possibilities for probing the Dark Matter and Dark Energy in the Universe. In this review, we summarise the theoretical and observational state of the subject, focussing on the statistical aspects of weak lensing, and consider the prospects for weak lensing surveys in the future. Weak gravitational lensing surveys are complementary to both galaxy surveys and cosmic microwave background (CMB) observations as they probe the unbiased non-linear matter power spectrum at modest redshifts. Most of the cosmological parameters are accurately estimated from CMB and large-scale galaxy surveys, so the focus of attention is shifting to understanding the nature of Dark Matter and Dark Energy. On the theoretical side, recent advances in the use of 3D information of the sources from photometric redshifts promise greater statistical power, and these are further enhanced by the use of statistics beyond two-point quantities such as the power spectrum. The use of 3D information also alleviates difficulties arising from physical effects such as the intrinsic alignment of galaxies, which can mimic weak lensing to some extent. On the observational side, in the next few years weak lensing surveys such as CFHTLS, VST-KIDS and Pan-STARRS, and the planned Dark Energy Survey, will provide the first weak lensing surveys covering very large sky areas and depth. In the long run even more ambitious programmes such as DUNE, the Supernova Anisotropy Probe (SNAP) and Large-aperture Synoptic Survey Telescope (LSST) are planned. Weak lensing of diffuse components such as the CMB and 21 cm emission can also
A Review on the Cosmology of the de Sitter Horndeski Models
Directory of Open Access Journals (Sweden)
Nelson J. Nunes
2017-03-01
Full Text Available We review the most general scalar-tensor cosmological models with up to second-order derivatives in the field equations that have a fixed spatially flat de Sitter critical point independent of the material content or vacuum energy. This subclass of the Horndeski Lagrangian is capable of dynamically adjusting any value of the vacuum energy of the matter fields at the critical point. We present the cosmological evolution of the linear models and the non-linear models with shift symmetry. We come to the conclusion that the shift symmetric non-linear models can deliver a viable background compatible with current observations.
International Nuclear Information System (INIS)
Miyazaki, A.
1979-01-01
The perturbation by a spherical rotating shell is investigated in a closed homogeneous and isotropic cosmological model of the Brans-Dicke theory to first order in an angular velocity of the shell. This model has a negative coupling parameter of the scalar field and satisfies the relation G (t) M/c 2 a (t) = π. The inertial frame at the origin is dragged completely with the same angular velocity when the rotating shell covers the whole universe. By a similar perturbation method, the distance dependence of the contribution from matter to the scalar field at the origin is obtained in this model. The contribution from nearby matter is negative because of the negative coupling constant, but the contribution from the whole universe is positive. The gravitational ''constant'' is almost determined by matter in the distant region
Dark matter reflection of particle symmetry
Khlopov, Maxim Yu.
2017-05-01
In the context of the relationship between physics of cosmological dark matter and symmetry of elementary particles, a wide list of dark matter candidates is possible. New symmetries provide stability of different new particles and their combination can lead to a multicomponent dark matter. The pattern of symmetry breaking involves phase transitions in the very early Universe, extending the list of candidates by topological defects and even primordial nonlinear structures.
Primack, Joel R.
2000-01-01
The cosmological parameters that I emphasize are the age of the universe $t_0$, the Hubble parameter $H_0 \\equiv 100 h$ km s$^{-1}$ Mpc$^{-1}$, the average matter density $\\Omega_m$, the baryonic matter density $\\Omega_b$, the neutrino density $\\Omega_\
Kevane, C J
1961-02-24
A cosmological model based on a gravitational plasma of matter and antimatter is discussed. The antigravitational interaction of matter and antimatter leads to segregation and an expansion of the plasma universe. The expansion time scale is controlled by the aggregation time scale.
International Nuclear Information System (INIS)
Wainwright, J.
1990-01-01
The workshop on mathematical cosmology was devoted to four topics of current interest. This report contains a brief discussion of the historical background of each topic and a concise summary of the content of each talk. The topics were; the observational cosmology program, the cosmological perturbation program, isotropic singularities, and the evolution of Bianchi cosmologies. (author)
International Nuclear Information System (INIS)
Turner, Michael S.
1999-01-01
For two decades the hot big-bang model as been referred to as the standard cosmology - and for good reason. For just as long cosmologists have known that there are fundamental questions that are not answered by the standard cosmology and point to a grander theory. The best candidate for that grander theory is inflation + cold dark matter. It holds that the Universe is flat, that slowly moving elementary particles left over from the earliest moments provide the cosmic infrastructure, and that the primeval density inhomogeneities that seed all the structure arose from quantum fluctuations. There is now prima facie evidence that supports two basic tenets of this paradigm. An avalanche of high-quality cosmological observations will soon make this case stronger or will break it. Key questions remain to be answered; foremost among them are: identification and detection of the cold dark matter particles and elucidation of the dark-energy component. These are exciting times in cosmology!
International Nuclear Information System (INIS)
Raychaudhuri, A.K.
1979-01-01
The subject is covered in chapters, entitled; introduction; Newtonian gravitation and cosmology; general relativity and relativistic cosmology; analysis of observational data; relativistic models not obeying the cosmological principle; microwave radiation background; thermal history of the universe and nucleosynthesis; singularity of cosmological models; gravitational constant as a field variable; cosmological models based on Einstein-Cartan theory; cosmological singularity in two recent theories; fate of perturbations of isotropic universes; formation of galaxies; baryon symmetric cosmology; assorted topics (including extragalactic radio sources; Mach principle). (U.K.)
Second-order Cosmological Perturbations Engendered by Point-like Masses
Energy Technology Data Exchange (ETDEWEB)
Brilenkov, Ruslan [Institute for Astro- and Particle Physics, University of Innsbruck, Technikerstrasse 25/8, A‐6020 Innsbruck (Austria); Eingorn, Maxim, E-mail: ruslan.brilenkov@gmail.com, E-mail: maxim.eingorn@gmail.com [North Carolina Central University, CREST and NASA Research Centers, 1801 Fayetteville St., Durham, NC 27707 (United States)
2017-08-20
In the ΛCDM framework, presenting nonrelativistic matter inhomogeneities as discrete massive particles, we develop the second‐order cosmological perturbation theory. Our approach relies on the weak gravitational field limit. The derived equations for the second‐order scalar, vector, and tensor metric corrections are suitable at arbitrary distances, including regions with nonlinear contrasts of the matter density. We thoroughly verify fulfillment of all Einstein equations, as well as self‐consistency of order assignments. In addition, we achieve logical positive results in the Minkowski background limit. Feasible investigations of the cosmological back-reaction manifestations by means of relativistic simulations are also outlined.
International Nuclear Information System (INIS)
Nojiri, S; Odintsov, S D; Oikonomou, V K
2016-01-01
We combine the unimodular gravity and mimetic gravity theories into a unified theoretical framework, which is proposed to provide a suggestive proposal for a framework that may assist in the discussion and search for a solution to the cosmological constant problem and the dark matter issue. After providing the formulation of the unimodular mimetic gravity and investigating all the new features that the vacuum unimodular gravity implies, by using the underlying reconstruction method, we realize some well known cosmological evolutions, with some of these being exotic for the ordinary Einstein–Hilbert gravity. Specifically we provide the vacuum unimodular mimetic gravity description of the de Sitter cosmology and of the perfect fluid with constant equation of state cosmology. As we demonstrate, these cosmologies can be realized by vacuum mimetic unimodular gravity, without the existence of any matter fluid source. Moreover, we investigate how cosmologically viable cosmologies, which are compatible with the recent observational data, can be realized by the vacuum unimodular mimetic gravity. Since in some cases, a graceful exit from inflation problem might exist, we provide a qualitative description of the mechanism that can potentially generate the graceful exit from inflation in these theories, by searching for the unstable de Sitter solutions in the context of unimodular mimetic theories of gravity. (paper)
Cosmology and particle physics
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Barrow, J.D.
1982-01-01
A brief overview is given of recent work that integrates cosmology and particle physics. The observational data regarding the abundance of matter and radiation in the Universe is described. The manner in which the cosmological survival density of stable massive particles can be calculated is discussed along with the process of cosmological nucleosynthesis. Several applications of these general arguments are given with reference to the survival density of nucleons, neutrinos and unconfined fractionally charge particles. The use of nucleosynthesis to limit the number of lepton generations is described together with the implications of a small neutrino mass for the origin of galaxies and clusters. (Auth.)
AIC and BIC for cosmological interacting scenarios
Energy Technology Data Exchange (ETDEWEB)
Arevalo, Fabiola [Universidad de La Frontera, Departamento de Ciencias Fisicas, Facultad de Ingenieria y Ciencias, Temuco (Chile); Cid, Antonella [Universidad del Bio-Bio, Departamento de Fisica and Grupo de Cosmologia y Gravitacion GCG-UBB, Concepcion (Chile); Moya, Jorge [Universidad de Concepcion, Departamento de Fisica, Concepcion (Chile)
2017-08-15
In this work we study linear and nonlinear cosmological interactions, which depend on dark matter and dark energy densities in the framework of general relativity. By using the Akaike information criterion (AIC) and the bayesian information criterion (BIC) with data from SnIa (Union 2.1 and binned JLA), H(z), BAO and CMB we compare the interacting models among themselves and analyze whether more complex interacting models are favored by these criteria. In this context, we find some suitable interactions that alleviate the coincidence problem. (orig.)
Cosmology and particle physics
International Nuclear Information System (INIS)
Turner, M.S.
1986-01-01
Progress in cosmology has become linked to progress in elementary particle physics. In these six lectures, the author illustrates the two-way nature of the interplay between these fields by focusing on a few selected topics. In the next section the author reviews the standard cosmology, especially concentrating on primordial nucleosynthesis and discusses how the standard cosmology has been used to place constraints on the properties of various particles. Grand Unification makes two striking predictions: (i) B non-conservation; (ii) the existence of stable, superheavy magnetic monopoles. Both have had great cosmological impact. In the following section the author discusses baryogenesis, the very attractive scenario in which the B,C,CP violating interactions in GUTs provide a dynamical explanation for the predominance of matter over antimatter and the present baryon-to-photon ratio. Monopoles are a cosmological disaster and an astrophysicist's delight. In Section 4 discusses monopoles, cosmology, and astrophysics. In the fourth lecture the author discusses how a very early (t≤10/sup -34/ sec) phase transition associated with spontaneous symmetry breaking (SSB) has the potential to explain a handful of very fundamental cosmological facts, facts which can be accommodated by the standard cosmology, but which are not ''explained'' by it. The fifth lecture is devoted to a discussion of structure formation in the universe
Sierra, Carlos; Müller, Markus
2016-04-01
SoilR is an R package for implementing diverse models representing soil organic matter dynamics. In previous releases of this package, we presented the implementation of linear first-order models with any number of pools as well as radiocarbon dynamics. We present here new improvements of the package regarding the possibility to implement models with nonlinear interactions among state variables and the possibility to calculate ages and transit times for nonlinear models with time dependencies. We show here examples on how to implement model structures with Michaelis-Menten terms for explicit microbial growth and resource use efficiency, and Langmuir isotherms for representing adsorption of organic matter to mineral surfaces. These nonlinear terms can be implemented for any number of organic matter pools, microbial functional groups, or mineralogy, depending on user's requirements. Through a simple example, we also show how transit times of organic matter in soils are controlled by the time-dependencies of the input terms.
Benoit-Lévy, Aurélien; Chardin, Gabriel
2014-05-01
We study an unconventional cosmology, in which we investigate the consequences that antigravity would pose to cosmology. We present the main characteristics of the Dirac-Milne Universe, a cosmological model where antimatter has a negative active gravitational mass. In this non-standard Universe, separate domains of matter and antimatter coexist at our epoch without annihilation, separated by a gravitationally induced depletion zone. We show that this cosmology does not require a priori the Dark Matter and Dark Energy components of the standard model of cosmology. Additionally, inflation becomes an unnecessary ingredient. Investigating this model, we show that the classical cosmological tests such as primordial nucleosynthesis, Type Ia supernovæ and Cosmic Microwave Background are surprisingly concordant.
International Nuclear Information System (INIS)
Hawking, S.W.
1984-01-01
The subject of these lectures is quantum effects in cosmology. The author deals first with situations in which the gravitational field can be treated as a classical, unquantized background on which the quantum matter fields propagate. This is the case with inflation at the GUT era. Nevertheless the curvature of spacetime can have important effects on the behaviour of the quantum fields and on the development of long-range correlations. He then turns to the question of the quantization of the gravitational field itself. The plan of these lectures is as follows: Euclidean approach to quantum field theory in flat space; the extension of techniques to quantum fields on a curved background with the four-sphere, the Euclidean version of De Sitter space as a particular example; the GUT era; quantization of the gravitational field by Euclidean path integrals; mini superspace model. (Auth.)
Axion as a Cold Dark Matter Candidate: Proof to Fully Nonlinear Order
Energy Technology Data Exchange (ETDEWEB)
Noh, Hyerim [Center for Large Telescope, Korea Astronomy and Space Science Institute, Daejon (Korea, Republic of); Hwang, Jai-chan [Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu (Korea, Republic of); Park, Chan-Gyung [Division of Science Education and Institute of Fusion Science, Chonbuk National University, Jeonju (Korea, Republic of)
2017-09-01
We present proof of the axion as a cold dark matter (CDM) candidate to the fully nonlinear order perturbations based on Einstein’s gravity. We consider the axion as a coherently oscillating massive classical scalar field without interaction. We present the fully nonlinear and exact, except for ignoring the transverse-tracefree tensor-type perturbation, hydrodynamic equations for an axion fluid in Einstein’s gravity. We show that the axion has the characteristic pressure and anisotropic stress; the latter starts to appear from the second-order perturbation. But these terms do not directly affect the hydrodynamic equations in our axion treatment. Instead, what behaves as the effective pressure term in relativistic hydrodynamic equations is the perturbed lapse function and the relativistic result coincides exactly with the one known in the previous non-relativistic studies. The effective pressure term leads to a Jeans scale that is of the solar-system scale for conventional axion mass. As the fully nonlinear and relativistic hydrodynamic equations for an axion fluid coincide exactly with the ones of a zero-pressure fluid in the super-Jeans scale, we have proved the CDM nature of such an axion in that scale.
Bubuianu, Laurenţiu; Vacaru, Sergiu I.
2018-05-01
We elaborate on the anholonomic frame deformation method, AFDM, for constructing exact solutions with quasiperiodic structure in modified gravity theories, MGTs, and general relativity, GR. Such solutions are described by generic off-diagonal metrics, nonlinear and linear connections and (effective) matter sources with coefficients depending on all spacetime coordinates via corresponding classes of generation and integration functions and (effective) matter sources. There are studied effective free energy functionals and nonlinear evolution equations for generating off-diagonal quasiperiodic deformations of black hole and/or homogeneous cosmological metrics. The physical data for such functionals are stated by different values of constants and prescribed symmetries for defining quasiperiodic structures at cosmological scales, or astrophysical objects in nontrivial gravitational backgrounds some similar forms as in condensed matter physics. It is shown how quasiperiodic structures determined by general nonlinear, or additive, functionals for generating functions and (effective) sources may transform black hole like configurations into cosmological metrics and inversely. We speculate on possible implications of quasiperiodic solutions in dark energy and dark matter physics. Finally, it is concluded that geometric methods for constructing exact solutions consist an important alternative tool to numerical relativity for investigating nonlinear effects in astrophysics and cosmology.
Dark matter-baryon segregation in the nonlinear evolution of coupled dark energy models
International Nuclear Information System (INIS)
Mainini, Roberto
2005-01-01
The growth and virialization of spherical top-hat fluctuations, in coupled dark energy models, causes segregation between dark matter (DM) and baryons, as the gravitational infall into the potential well proceeds more slowly for the baryons than for DM. As a consequence, after attaining their turnaround and before full virialization, halos have outer layers rich of baryons. Accordingly, a natural ambiguity exists on the definition of the virial density contrast. In fact, when the outer baryon layers infall onto the DM-richer core, they carry with them DM materials outside the original fluctuation; hence, no time exists when all materials originally belonging to the fluctuation--and only they--have virialized. Baryon-DM segregation can have various astrophysical consequences on different length scales. The smallest halos may loose up to 50% of the original baryonic contents and become hardly visible. Subhalos in cluster-size halos may loose much baryonic materials, which could then be observed as intracluster light. Isolated halos, in general, can be expected to have a baryon component richer than the cosmological proportions, due to the cosmic enrichement of baryons lost in small halo encounters
International Nuclear Information System (INIS)
Kehagias, A.; Riotto, A.
2016-01-01
Symmetries play an interesting role in cosmology. They are useful in characterizing the cosmological perturbations generated during inflation and lead to consistency relations involving the soft limit of the statistical correlators of large-scale structure dark matter and galaxies overdensities. On the other hand, in observational cosmology the carriers of the information about these large-scale statistical distributions are light rays traveling on null geodesics. Motivated by this simple consideration, we study the structure of null infinity and the associated BMS symmetry in a cosmological setting. For decelerating Friedmann-Robertson-Walker backgrounds, for which future null infinity exists, we find that the BMS transformations which leaves the asymptotic metric invariant to leading order. Contrary to the asymptotic flat case, the BMS transformations in cosmology generate Goldstone modes corresponding to scalar, vector and tensor degrees of freedom which may exist at null infinity and perturb the asymptotic data. Therefore, BMS transformations generate physically inequivalent vacua as they populate the universe at null infinity with these physical degrees of freedom. We also discuss the gravitational memory effect when cosmological expansion is taken into account. In this case, there are extra contribution to the gravitational memory due to the tail of the retarded Green functions which are supported not only on the light-cone, but also in its interior. The gravitational memory effect can be understood also from an asymptotic point of view as a transition among cosmological BMS-related vacua.
Energy Technology Data Exchange (ETDEWEB)
Kehagias, A. [Physics Division, National Technical University of Athens, 15780 Zografou Campus, Athens (Greece); Riotto, A. [Department of Theoretical Physics,24 quai E. Ansermet, CH-1211 Geneva 4 (Switzerland); Center for Astroparticle Physics (CAP),24 quai E. Ansermet, CH-1211 Geneva 4 (Switzerland)
2016-05-25
Symmetries play an interesting role in cosmology. They are useful in characterizing the cosmological perturbations generated during inflation and lead to consistency relations involving the soft limit of the statistical correlators of large-scale structure dark matter and galaxies overdensities. On the other hand, in observational cosmology the carriers of the information about these large-scale statistical distributions are light rays traveling on null geodesics. Motivated by this simple consideration, we study the structure of null infinity and the associated BMS symmetry in a cosmological setting. For decelerating Friedmann-Robertson-Walker backgrounds, for which future null infinity exists, we find that the BMS transformations which leaves the asymptotic metric invariant to leading order. Contrary to the asymptotic flat case, the BMS transformations in cosmology generate Goldstone modes corresponding to scalar, vector and tensor degrees of freedom which may exist at null infinity and perturb the asymptotic data. Therefore, BMS transformations generate physically inequivalent vacua as they populate the universe at null infinity with these physical degrees of freedom. We also discuss the gravitational memory effect when cosmological expansion is taken into account. In this case, there are extra contribution to the gravitational memory due to the tail of the retarded Green functions which are supported not only on the light-cone, but also in its interior. The gravitational memory effect can be understood also from an asymptotic point of view as a transition among cosmological BMS-related vacua.
Cosmology with exponential potentials
International Nuclear Information System (INIS)
Kehagias, Alex; Kofinas, Georgios
2004-01-01
We examine in the context of general relativity the dynamics of a spatially flat Robertson-Walker universe filled with a classical minimally coupled scalar field φ of exponential potential V(φ) ∼ exp(-μφ) plus pressureless baryonic matter. This system is reduced to a first-order ordinary differential equation for Ω φ (w φ ) or q(w φ ), providing direct evidence on the acceleration/deceleration properties of the system. As a consequence, for positive potentials, passage into acceleration not at late times is generically a feature of the system for any value of μ, even when the late-times attractors are decelerating. Furthermore, the structure formation bound, together with the constraints Ω m0 ∼ 0.25 - 0.3, -1 ≤ w φ0 ≤ -0.6, provides, independently of initial conditions and other parameters, the necessary condition 0 N , while the less conservative constraint -1 ≤ w φ ≤ -0.93 gives 0 N . Special solutions are found to possess intervals of acceleration. For the almost cosmological constant case w φ ∼ -1, the general relation Ω φ (w φ ) is obtained. The generic (nonlinearized) late-times solution of the system in the plane (w φ , Ω φ ) or (w φ , q) is also derived
Cosmological Probes for Supersymmetry
Directory of Open Access Journals (Sweden)
Maxim Khlopov
2015-05-01
Full Text Available The multi-parameter character of supersymmetric dark-matter models implies the combination of their experimental studies with astrophysical and cosmological probes. The physics of the early Universe provides nontrivial effects of non-equilibrium particles and primordial cosmological structures. Primordial black holes (PBHs are a profound signature of such structures that may arise as a cosmological consequence of supersymmetric (SUSY models. SUSY-based mechanisms of baryosynthesis can lead to the possibility of antimatter domains in a baryon asymmetric Universe. In the context of cosmoparticle physics, which studies the fundamental relationship of the micro- and macro-worlds, the development of SUSY illustrates the main principles of this approach, as the physical basis of the modern cosmology provides cross-disciplinary tests in physical and astronomical studies.
Ryden, Barbara
2017-01-01
This second edition of Introduction to Cosmology is an exciting update of an award-winning textbook. It is aimed primarily at advanced undergraduate students in physics and astronomy, but is also useful as a supplementary text at higher levels. It explains modern cosmological concepts, such as dark energy, in the context of the Big Bang theory. Its clear, lucid writing style, with a wealth of useful everyday analogies, makes it exceptionally engaging. Emphasis is placed on the links between theoretical concepts of cosmology and the observable properties of the universe, building deeper physical insights in the reader. The second edition includes recent observational results, fuller descriptions of special and general relativity, expanded discussions of dark energy, and a new chapter on baryonic matter that makes up stars and galaxies. It is an ideal textbook for the era of precision cosmology in the accelerating universe.
International Nuclear Information System (INIS)
Landsberg, P.T.; Evans, D.A.
1977-01-01
The subject is dealt with in chapters, entitled: cosmology -some fundamentals; Newtonian gravitation - some fundamentals; the cosmological differential equation - the particle model and the continuum model; some simple Friedmann models; the classification of the Friedmann models; the steady-state model; universe with pressure; optical effects of the expansion according to various theories of light; optical observations and cosmological models. (U.K.)
High energy physics and cosmology
International Nuclear Information System (INIS)
Silk, J.I.; Davis, M.
1989-01-01
This research will focus on the implications of recent theories and experiments in high energy physics for the evolution of the early Universe, and on the constraints that cosmological considerations can place on such theories. Several problems are under investigation, including the development of constraints on the inflationary predictions of scale--free primordial fluctuations in a universe at critical closure density by studying their linear and non-linear evolution after they re-enter the particle horizon. We will examine the observable imprint of primordial density fluctuations on the cosmic microwave background radiation curved cosmological models. Most astronomical evidence points to an open universe: one of our goals is to reconcile this conclusion with the particle physics input. We will investigate the response of the matter distribution to a network of cosmic strings produced during an early symmetry-breaking transition, and compute the resulting cosmic microwave background anisotropies. We will simulate the formation of large-scale structures whose dynamics are dominated by weakly interacting particles such as axions, massive neutrinos or photinos in order to model the formation of galaxies, galaxy clusters and superclusters. We will study of the distortions in the microwave background radiation, both spectral and angular, that are produced by ionized gas associated with forming clusters and groups of galaxies. We will also study constraints on exotic cooling mechanisms involving axions and majorons set by stellar evolution and the energy input into low mass stars by cold dark matter annihilation galactic nuclei. We will compute the detailed gamma ray spectrum predicted by various cold dark matter candidates undergoing annihilation in the galactic halo and bulge
[High energy physics and cosmology
International Nuclear Information System (INIS)
Silk, J.I.; Davis, M.
1988-01-01
This research will focus on the implications of recent theories and experiments in high energy physics for the evolution of the early Universe, and on the constraints that cosmological considerations can place on such theories. Several problems are under investigation, including the development of constraints on the inflationary predictions of scale-free primordial fluctuations in a universe at critical closure density by studying their linear and non-linear evolution after they re-enter the particle horizon. We will examine the observable imprint of primordial density fluctuations on the cosmic microwave background radiation in curved cosmological models. Most astronomical evidence points to an open universe: one of our goals is to reconcile this conclusion with the particle physics input. We will investigate the response of the matter distribution to a network of cosmic strings produced during an early symmetry--breaking transition, and compute the resulting cosmic microwave background anisotropies. We will simulate the formation of large--scale structures whose dynamics are dominated by weakly interacting particles such as axions massive neutrinos or photinos in order to model the formation of galaxies, galaxy clusters and superclusters. We will study the distortions in the microwave background radiation, both spectral and angular, that are produced by ionized gas associated with forming clusters and groups of galaxies. We will also study constraints on exotic cooling mechanisms involving axions and majorons set by stellar evolution and the energy input into low mass stars by cold dark matter annihilation in galactic nuclei. We will compute the detailed gamma ray spectrum predicted by various cold dark matter candidates undergoing annihilation in the galactic halo and bulge
Energy Technology Data Exchange (ETDEWEB)
Shirasaki, Masato [National Astronomical Observatory of Japan, Mitaka, Tokyo (Japan); Macias, Oscar; Horiuchi, Shunsaku [Virginia Tech, Blacksburg, VA (United States). Center for Neutrino Physics; Shirai, Satoshi [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Yoshida, Naoki [Tokyo Univ. (Japan). Dept. of Physics; Tokyo Univ., Chiba (Japan). Kavli Inst. for the Physics and Mathematics of the Universe (WPI); Japan Science and Technology Agency, Saitama (Japan). CREST
2016-07-15
We derive constraints on dark matter (DM) annihilation cross section and decay lifetime from cross-correlation analyses of the data from Fermi-LAT and weak lensing surveys that cover a wide area of ∝660 squared degrees in total. We improve upon our previous analyses by using an updated extragalactic γ-ray background data reprocessed with the Fermi Pass 8 pipeline, and by using well-calibrated shape measurements of about twelve million galaxies in the Canada-France-Hawaii Lensing Survey (CFHTLenS) and Red-Cluster-Sequence Lensing Survey (RCSLenS). We generate a large set of full-sky mock catalogs from cosmological N-body simulations and use them to estimate statistical errors accurately. The measured cross correlation is consistent with null detection, which is then used to place strong cosmological constraints on annihilating and decaying DM. For leptophilic DM, the constraints are improved by a factor of ∝ 100 in the mass range of O(1) TeV when including contributions from secondary γ rays due to the inverse-Compton upscattering of background photons. Annihilation cross-sections of left angle σν right angle ∝ 10{sup -23} cm{sup 3}/s are excluded for TeV-scale DM depending on channel. Lifetimes of ∝10{sup 25} sec are also excluded for the decaying TeV-scale DM. Finally, we apply this analysis to wino DM and exclude the wino mass around 200 GeV. These constraints will be further tightened, and all the interesting wino DM parameter region can be tested, by using data from future wide-field cosmology surveys.
International Nuclear Information System (INIS)
Shirasaki, Masato; Macias, Oscar; Horiuchi, Shunsaku; Yoshida, Naoki; Tokyo Univ., Chiba; Japan Science and Technology Agency, Saitama
2016-07-01
We derive constraints on dark matter (DM) annihilation cross section and decay lifetime from cross-correlation analyses of the data from Fermi-LAT and weak lensing surveys that cover a wide area of ∝660 squared degrees in total. We improve upon our previous analyses by using an updated extragalactic γ-ray background data reprocessed with the Fermi Pass 8 pipeline, and by using well-calibrated shape measurements of about twelve million galaxies in the Canada-France-Hawaii Lensing Survey (CFHTLenS) and Red-Cluster-Sequence Lensing Survey (RCSLenS). We generate a large set of full-sky mock catalogs from cosmological N-body simulations and use them to estimate statistical errors accurately. The measured cross correlation is consistent with null detection, which is then used to place strong cosmological constraints on annihilating and decaying DM. For leptophilic DM, the constraints are improved by a factor of ∝ 100 in the mass range of O(1) TeV when including contributions from secondary γ rays due to the inverse-Compton upscattering of background photons. Annihilation cross-sections of left angle σν right angle ∝ 10"-"2"3 cm"3/s are excluded for TeV-scale DM depending on channel. Lifetimes of ∝10"2"5 sec are also excluded for the decaying TeV-scale DM. Finally, we apply this analysis to wino DM and exclude the wino mass around 200 GeV. These constraints will be further tightened, and all the interesting wino DM parameter region can be tested, by using data from future wide-field cosmology surveys.
Cosmological Reflection of Particle Symmetry
Directory of Open Access Journals (Sweden)
Maxim Khlopov
2016-08-01
Full Text Available The standard model involves particle symmetry and the mechanism of its breaking. Modern cosmology is based on inflationary models with baryosynthesis and dark matter/energy, which involves physics beyond the standard model. Studies of the physical basis of modern cosmology combine direct searches for new physics at accelerators with its indirect non-accelerator probes, in which cosmological consequences of particle models play an important role. The cosmological reflection of particle symmetry and the mechanisms of its breaking are the subject of the present review.
Observable cosmology and cosmological models
International Nuclear Information System (INIS)
Kardashev, N.S.; Lukash, V.N.; Novikov, I.D.
1987-01-01
Modern state of observation cosmology is briefly discussed. Among other things, a problem, related to Hibble constant and slowdown constant determining is considered. Within ''pancake'' theory hot (neutrino) cosmological model explains well the large-scale structure of the Universe, but does not explain the galaxy formation. A cold cosmological model explains well light object formation, but contradicts data on large-scale structure
Belinski, Vladimir
2018-01-01
Written for researchers focusing on general relativity, supergravity, and cosmology, this is a self-contained exposition of the structure of the cosmological singularity in generic solutions of the Einstein equations, and an up-to-date mathematical derivation of the theory underlying the Belinski–Khalatnikov–Lifshitz (BKL) conjecture on this field. Part I provides a comprehensive review of the theory underlying the BKL conjecture. The generic asymptotic behavior near the cosmological singularity of the gravitational field, and fields describing other kinds of matter, is explained in detail. Part II focuses on the billiard reformulation of the BKL behavior. Taking a general approach, this section does not assume any simplifying symmetry conditions and applies to theories involving a range of matter fields and space-time dimensions, including supergravities. Overall, this book will equip theoretical and mathematical physicists with the theoretical fundamentals of the Big Bang, Big Crunch, Black Hole singula...
Matter-wave two-dimensional solitons in crossed linear and nonlinear optical lattices
International Nuclear Information System (INIS)
Luz, H. L. F. da; Gammal, A.; Abdullaev, F. Kh.; Salerno, M.; Tomio, Lauro
2010-01-01
The existence of multidimensional matter-wave solitons in a crossed optical lattice (OL) with a linear optical lattice (LOL) in the x direction and a nonlinear optical lattice (NOL) in the y direction, where the NOL can be generated by a periodic spatial modulation of the scattering length using an optically induced Feshbach resonance is demonstrated. In particular, we show that such crossed LOLs and NOLs allow for stabilizing two-dimensional solitons against decay or collapse for both attractive and repulsive interactions. The solutions for the soliton stability are investigated analytically, by using a multi-Gaussian variational approach, with the Vakhitov-Kolokolov necessary criterion for stability; and numerically, by using the relaxation method and direct numerical time integrations of the Gross-Pitaevskii equation. Very good agreement of the results corresponding to both treatments is observed.
Matter-wave two-dimensional solitons in crossed linear and nonlinear optical lattices
da Luz, H. L. F.; Abdullaev, F. Kh.; Gammal, A.; Salerno, M.; Tomio, Lauro
2010-10-01
The existence of multidimensional matter-wave solitons in a crossed optical lattice (OL) with a linear optical lattice (LOL) in the x direction and a nonlinear optical lattice (NOL) in the y direction, where the NOL can be generated by a periodic spatial modulation of the scattering length using an optically induced Feshbach resonance is demonstrated. In particular, we show that such crossed LOLs and NOLs allow for stabilizing two-dimensional solitons against decay or collapse for both attractive and repulsive interactions. The solutions for the soliton stability are investigated analytically, by using a multi-Gaussian variational approach, with the Vakhitov-Kolokolov necessary criterion for stability; and numerically, by using the relaxation method and direct numerical time integrations of the Gross-Pitaevskii equation. Very good agreement of the results corresponding to both treatments is observed.
Interactions between dark energy and dark matter
Energy Technology Data Exchange (ETDEWEB)
Baldi, Marco
2009-03-20
We have investigated interacting dark energy cosmologies both concerning their impact on the background evolution of the Universe and their effects on cosmological structure growth. For the former aspect, we have developed a cosmological model featuring a matter species consisting of particles with a mass that increases with time. In such model the appearance of a Growing Matter component, which is negligible in early cosmology, dramatically slows down the evolution of the dark energy scalar field at a redshift around six, and triggers the onset of the accelerated expansion of the Universe, therefore addressing the Coincidence Problem. We propose to identify this Growing Matter component with cosmic neutrinos, in which case the present dark energy density can be related to the measured average mass of neutrinos. For the latter aspect, we have implemented the new physical features of interacting dark energy models into the cosmological N-body code GADGET-2, and we present the results of a series of high-resolution simulations for a simple realization of dark energy interaction. As a consequence of the new physics, cold dark matter and baryon distributions evolve differently both in the linear and in the non-linear regime of structure formation. Already on large scales, a linear bias develops between these two components, which is further enhanced by the non-linear evolution. We also find, in contrast with previous work, that the density profiles of cold dark matter halos are less concentrated in coupled dark energy cosmologies compared with {lambda}{sub CDM}. Also, the baryon fraction in halos in the coupled models is significantly reduced below the universal baryon fraction. These features alleviate tensions between observations and the {lambda}{sub CDM} model on small scales. Our methodology is ideally suited to explore the predictions of coupled dark energy models in the fully non-linear regime, which can provide powerful constraints for the viable parameter
Interactions between dark energy and dark matter
International Nuclear Information System (INIS)
Baldi, Marco
2009-01-01
We have investigated interacting dark energy cosmologies both concerning their impact on the background evolution of the Universe and their effects on cosmological structure growth. For the former aspect, we have developed a cosmological model featuring a matter species consisting of particles with a mass that increases with time. In such model the appearance of a Growing Matter component, which is negligible in early cosmology, dramatically slows down the evolution of the dark energy scalar field at a redshift around six, and triggers the onset of the accelerated expansion of the Universe, therefore addressing the Coincidence Problem. We propose to identify this Growing Matter component with cosmic neutrinos, in which case the present dark energy density can be related to the measured average mass of neutrinos. For the latter aspect, we have implemented the new physical features of interacting dark energy models into the cosmological N-body code GADGET-2, and we present the results of a series of high-resolution simulations for a simple realization of dark energy interaction. As a consequence of the new physics, cold dark matter and baryon distributions evolve differently both in the linear and in the non-linear regime of structure formation. Already on large scales, a linear bias develops between these two components, which is further enhanced by the non-linear evolution. We also find, in contrast with previous work, that the density profiles of cold dark matter halos are less concentrated in coupled dark energy cosmologies compared with Λ CDM . Also, the baryon fraction in halos in the coupled models is significantly reduced below the universal baryon fraction. These features alleviate tensions between observations and the Λ CDM model on small scales. Our methodology is ideally suited to explore the predictions of coupled dark energy models in the fully non-linear regime, which can provide powerful constraints for the viable parameter space of such scenarios
On Semi-classical Degravitation and the Cosmological Constant Problems
Patil, Subodh P
2010-01-01
In this report, we discuss a candidate mechanism through which one might address the various cosmological constant problems. We first observe that the renormalization of gravitational couplings (induced by integrating out various matter fields) manifests non-local modifications to Einstein's equations as quantum corrected equations of motion. That is, at the loop level, matter sources curvature through a gravitational coupling that is a non-local function of the covariant d'Alembertian. If the functional form of the resulting Newton's `constant' is such that it annihilates very long wavelength sources, but reduces to $1/M^2_{pl}$ ($M_{pl}$ being the 4d Planck mass) for all sources with cosmologically observable wavelengths, we would have a complimentary realization of the degravitation paradigm-- a realization through which its non-linear completion and the corresponding modified Bianchi identities are readily understood. We proceed to consider various theories whose coupling to gravity may a priori induce no...
Coupled DM Heating in SCDEW Cosmologies
Directory of Open Access Journals (Sweden)
Silvio Bonometto
2017-08-01
Full Text Available Strongly-Coupled Dark Energy plus Warm dark matter (SCDEW cosmologies admit the stationary presence of ∼1% of coupled-DM and DE, since inflationary reheating. Coupled-DM fluctuations therefore grow up to non-linearity even in the early radiative expansion. Such early non-linear stages are modelized here through the evolution of a top-hat density enhancement, reaching an early virial balance when the coupled-DM density contrast is just 25–26, and the DM density enhancement is ∼10 % of the total density. During the time needed to settle in virial equilibrium, the virial balance conditions, however, continue to modify, so that “virialized” lumps undergo a complete evaporation. Here, we outline that DM particles processed by overdensities preserve a fraction of their virial momentum. Although fully non-relativistic, the resulting velocities (moderately affect the fluctuation dynamics over greater scales, entering the horizon later on.
Indian Academy of Sciences (India)
This report is based on a recent work in collaboration with Bagla and Padmanabhan. [1]. In this paper, we construct cosmological models with homogeneous tachyon matter [2] to provide the dark energy component which drives acceleration of the universe (for a recent review of dark energy models, see [3]). We assume that.
Nonlinear dynamics and damage induced properties of soft matter with application in oncology
Naimark, O.
2017-09-01
Molecular-morphological signs of oncogenesis could be linked to multiscale collective effects in molecular, cell and tissue related to defects (damage) dynamics. It was shown that nonlinear behavior of biological systems can be linked to the existence of characteristic collective open state modes providing the coherent expression dynamics. New type of criticality in nonequilibrium systems with defects—structural-scaling transition allows the definition of the `driving force' for a biological soft matter related to consolidated open states. The set of collective open states (breathers, autosolitons and blow-up modes) in the molecular ensembles provides the collective expression dynamics to attract the entire system (cell, tissue) toward a few preferred global states. The co-existence of three types of collective modes determines the multifractal scenario of biological soft matter dynamics. The appearance of `globally convergent' dynamics corresponding to the coherent behavior of multiscale blow-up open states (blow-up gene expression) leads to anomalous localized softening (blow-up localized damage) and the subjection of the cells (or tissue) to monofractal dynamics. This dynamics can be associated with cancer progression.
Cosmology and the weak interaction
Energy Technology Data Exchange (ETDEWEB)
Schramm, D.N. (Fermi National Accelerator Lab., Batavia, IL (USA)):(Chicago Univ., IL (USA))
1989-12-01
The weak interaction plays a critical role in modern Big Bang cosmology. This review will emphasize two of its most publicized cosmological connections: Big Bang nucleosynthesis and Dark Matter. The first of these is connected to the cosmological prediction of Neutrino Flavours, N{sub {nu}} {approximately} 3 which is now being confirmed at SLC and LEP. The second is interrelated to the whole problem of galaxy and structure formation in the universe. This review will demonstrate the role of the weak interaction both for dark matter candidates and for the problem of generating seeds to form structure. 87 refs., 3 figs., 5 tabs.
Cosmology and the weak interaction
International Nuclear Information System (INIS)
Schramm, D.N.
1989-12-01
The weak interaction plays a critical role in modern Big Bang cosmology. This review will emphasize two of its most publicized cosmological connections: Big Bang nucleosynthesis and Dark Matter. The first of these is connected to the cosmological prediction of Neutrino Flavours, N ν ∼ 3 which is now being confirmed at SLC and LEP. The second is interrelated to the whole problem of galaxy and structure formation in the universe. This review will demonstrate the role of the weak interaction both for dark matter candidates and for the problem of generating seeds to form structure. 87 refs., 3 figs., 5 tabs
International Nuclear Information System (INIS)
Amendola, Luca; Campos, Gabriela Camargo; Rosenfeld, Rogerio
2007-01-01
Models where the dark matter component of the Universe interacts with the dark energy field have been proposed as a solution to the cosmic coincidence problem, since in the attractor regime both dark energy and dark matter scale in the same way. In these models the mass of the cold dark matter particles is a function of the dark energy field responsible for the present acceleration of the Universe, and different scenarios can be parametrized by how the mass of the cold dark matter particles evolves with time. In this article we study the impact of a constant coupling δ between dark energy and dark matter on the determination of a redshift dependent dark energy equation of state w DE (z) and on the dark matter density today from SNIa data. We derive an analytical expression for the luminosity distance in this case. In particular, we show that the presence of such a coupling increases the tension between the cosmic microwave background data from the analysis of the shift parameter in models with constant w DE and SNIa data for realistic values of the present dark matter density fraction. Thus, an independent measurement of the present dark matter density can place constraints on models with interacting dark energy
Li, Bohua; Shapiro, Paul R.; Rindler-Daller, Tanja
2017-09-01
We consider an alternative to weakly interacting massive particle (WIMP) cold dark matter (CDM)—ultralight bosonic dark matter (m ≳10-22 eV /c2) described by a complex scalar field (SFDM) with a global U (1 ) symmetry—for which the comoving particle number density or charge density is conserved after particle production during standard reheating. We allow for a repulsive self-interaction. In a Λ SFDM universe, SFDM starts out relativistic, evolving from stiff (w =1 ) to radiation-like (w =1 /3 ), before becoming nonrelativistic at late times (w =0 ). Thus, before the familiar radiation-dominated era, there is an earlier era of stiff-SFDM domination. During both the stiff-SFDM-dominated and radiation-dominated eras, the expansion rate is higher than in Λ CDM . The SFDM particle mass m and quartic self-interaction coupling strength λ are therefore constrained by cosmological observables, particularly Neff, the effective number of neutrino species during big bang nucleosynthesis, and zeq, the redshift of matter-radiation equality. Furthermore, since the stochastic gravitational-wave background (SGWB) from inflation is amplified during the stiff-SFDM-dominated era, it can contribute a radiation-like component large enough to affect these observables by further boosting the expansion rate after the stiff era ends. Remarkably, this same amplification makes detection of the SGWB possible at high frequencies by current laser interferometer experiments, e.g., aLIGO/Virgo and LISA. For SFDM particle parameters that satisfy these cosmological constraints, the amplified SGWB is detectable by LIGO for a broad range of reheat temperatures Treheat, for values of the tensor-to-scalar ratio r currently allowed by cosmic microwave background polarization measurements. For a given r and λ /(m c2)2, the marginally allowed Λ SFDM model for each Treheat has the smallest m that satisfies the cosmological constraints, and maximizes the present SGWB energy density for that
Low-redshift formula for the luminosity distance in a LTB model with cosmological constant
Energy Technology Data Exchange (ETDEWEB)
Romano, Antonio Enea [National Taiwan University, Leung Center for Cosmology and Particle Astrophysics, Taipei (China); Kyoto University, Yukawa Institute for Theoretical Physics, Kyoto (Japan); Universidad de Antioquia, Instituto de Fisica, Medellin (Colombia); Chen, Pisin [National Taiwan University, Leung Center for Cosmology and Particle Astrophysics, Taipei (China); SLAC National Accelerator Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Menlo Park, CA (United States)
2014-04-15
We calculate the low-redshift Taylor expansion for the luminosity distance for an observer at the center of a spherically symmetric matter inhomogeneity with a non-vanishing cosmological constant. We then test the accuracy of the formulas comparing them to the numerical calculation for different cases for both the luminosity distance and the radial coordinate. The formulas can be used as a starting point to understand the general non-linear effects of a local inhomogeneity in the presence of a cosmological constant, without making any special assumption as regards the inhomogeneity profile. (orig.)
2012-01-01
This volume tells of the quest for cosmology as seen by some of the finest cosmologists in the world. It starts with "Galaxy Formation from Start to Finish" and ends with "The First Supermassive Black Holes in the Universe," exploring in between the grand themes of galaxies, the early universe, expansion of the universe, dark matter and dark energy. This up-to-date collection of review articles offers a general introduction to cosmology and is intended for all probing into the profound questions on where we came from and where we are going.
Cosmological models without singularities
International Nuclear Information System (INIS)
Petry, W.
1981-01-01
A previously studied theory of gravitation in flat space-time is applied to homogeneous and isotropic cosmological models. There exist two different classes of models without singularities: (i) ever-expanding models, (ii) oscillating models. The first class contains models with hot big bang. For these models there exist at the beginning of the universe-in contrast to Einstein's theory-very high but finite densities of matter and radiation with a big bang of very short duration. After short time these models pass into the homogeneous and isotropic models of Einstein's theory with spatial curvature equal to zero and cosmological constant ALPHA >= O. (author)
International Nuclear Information System (INIS)
Desert, F.-Xavier
2004-01-01
After an introduction comprising some definitions, an historical overview, and a discussion of the paradoxical Universe, this course proposes a presentation of fundamental notions and theories, i.e. the restrained relativity and the universal gravitation. The next part addresses the general relativity with the following notions: space-time metrics and principle of generalised covariance, basics of tensor analysis, geodesics, energy-pulse tensor, curvature, Einstein equations, Newtonian limit, Schwarzschild metrics, gravitational waves, gravitational redshift. The next part addresses the standard cosmology with the Friedmann-Robertson-Walker metrics and the Friedmann-Lemaitre equations of the evolution of the Universe. The Universe expansion is then addressed: distances and horizons, Hubble law, determination of the Hubble constant. The next chapter deals with the constituents of the Universe: light matter, baryonic dark matter, black matter, supernovae, Universe acceleration and black energy. Then comes the nuclear evolution of the Universe: thermodynamics of the primordial Universe, the matter-antimatter asymmetry, from quarks to atoms, cosmic abundance, neutron cosmological background, matter-radiation equality, cosmo-chronology or the age of the Universe. The next chapter addresses the cosmological background at 3 K: sky electromagnetic spectrum, measurement of CMB anisotropies, interpretation of anisotropies, growth of perturbations. The last chapter addresses the quantum field theory and inflation: paradoxes of the standard Big Bang, the simple inflation, noticeable consequences
Sanders, RH; Papantonopoulos, E
2005-01-01
I discuss the classical cosmological tests, i.e., angular size-redshift, flux-redshift, and galaxy number counts, in the light of the cosmology prescribed by the interpretation of the CMB anisotropies. The discussion is somewhat of a primer for physicists, with emphasis upon the possible systematic
Testing universal relations of neutron stars with a nonlinear matter-gravity coupling theory
International Nuclear Information System (INIS)
Sham, Y.-H.; Lin, L.-M.; Leung, P. T.
2014-01-01
Due to our ignorance of the equation of state (EOS) beyond nuclear density, there is still no unique theoretical model for neutron stars (NSs). It is therefore surprising that universal EOS-independent relations connecting different physical quantities of NSs can exist. Lau et al. found that the frequency of the f-mode oscillation, the mass, and the moment of inertia are connected by universal relations. More recently, Yagi and Yunes discovered the I-Love-Q universal relations among the mass, the moment of inertia, the Love number, and the quadrupole moment. In this paper, we study these universal relations in the Eddington-inspired Born-Infeld (EiBI) gravity. This theory differs from general relativity (GR) significantly only at high densities due to the nonlinear coupling between matter and gravity. It thus provides us an ideal case to test how robust the universal relations of NSs are with respect to the change of the gravity theory. Due to the apparent EOS formulation of EiBI gravity developed recently by Delsate and Steinhoff, we are able to study the universal relations in EiBI gravity using the same techniques as those in GR. We find that the universal relations in EiBI gravity are essentially the same as those in GR. Our work shows that, within the currently viable coupling constant, there exists at least one modified gravity theory that is indistinguishable from GR in view of the unexpected universal relations.
Testing Universal Relations of Neutron Stars with a Nonlinear Matter-Gravity Coupling Theory
Sham, Y.-H.; Lin, L.-M.; Leung, P. T.
2014-02-01
Due to our ignorance of the equation of state (EOS) beyond nuclear density, there is still no unique theoretical model for neutron stars (NSs). It is therefore surprising that universal EOS-independent relations connecting different physical quantities of NSs can exist. Lau et al. found that the frequency of the f-mode oscillation, the mass, and the moment of inertia are connected by universal relations. More recently, Yagi and Yunes discovered the I-Love-Q universal relations among the mass, the moment of inertia, the Love number, and the quadrupole moment. In this paper, we study these universal relations in the Eddington-inspired Born-Infeld (EiBI) gravity. This theory differs from general relativity (GR) significantly only at high densities due to the nonlinear coupling between matter and gravity. It thus provides us an ideal case to test how robust the universal relations of NSs are with respect to the change of the gravity theory. Due to the apparent EOS formulation of EiBI gravity developed recently by Delsate and Steinhoff, we are able to study the universal relations in EiBI gravity using the same techniques as those in GR. We find that the universal relations in EiBI gravity are essentially the same as those in GR. Our work shows that, within the currently viable coupling constant, there exists at least one modified gravity theory that is indistinguishable from GR in view of the unexpected universal relations.
Energy Technology Data Exchange (ETDEWEB)
Shabani, Hamid [University of Sistan and Baluchestan, Physics Department, Faculty of Sciences, Zahedan (Iran, Islamic Republic of); Ziaie, Amir Hadi [Islamic Azad University, Department of Physics, Kahnooj Branch, Kerman (Iran, Islamic Republic of)
2017-08-15
In this work, we study the late-time cosmological solutions of f(R, T) = g(R) + h(-T) models assuming that the conservation of the energy-momentum tensor (EMT) is violated. We perform our analysis through constructing an autonomous dynamical system for the equations of motion. We study the stability properties of solutions via considering linear perturbations about the related equilibrium points. Moreover, we parameterize the Lagrangian by introducing the parameters m(r) and n(s). These parameters which are constructed out of the functions g(R) and h(-T) play the main role in finding the late-time behavior of the solutions. We find that there exist, in general, three classes of solutions; all models with n > 0 include a proper transition from a prolonged matter era to a de Sitter solution. Models with -0.5 < n < 0 and n{sup '} > 1, for at least a root of equation n(s) = s - 1, include an unphysical dark energy solution preceding an improper matter era. Finally, for n < -1/2 there is a transient accelerated expansion era with -1/2 < w{sup (eff)} < -1/3 before a de Sitter phase. For all cases, in order to have a long enough matter dominated epoch, the condition m{sup '} → 0{sup +} for r
Nonsingular electrovacuum solutions with dynamically generated cosmological constant
Energy Technology Data Exchange (ETDEWEB)
Guendelman, E.I., E-mail: guendel@bgumail.bgu.ac.il [Physics Department, Ben Gurion University of the Negev, Beer Sheva 84105 (Israel); Olmo, Gonzalo J., E-mail: gonzalo.olmo@csic.es [Departamento de Física Teórica and IFIC, Centro Mixto Universidad de Valencia – CSIC, Universidad de Valencia, Burjassot 46100, Valencia (Spain); Rubiera-Garcia, D., E-mail: drubiera@fisica.ufpb.br [Departamento de Física, Universidade Federal da Paraíba, 58051-900 João Pessoa, Paraíba (Brazil); Vasihoun, M., E-mail: maharyw@gmail.com [Physics Department, Ben Gurion University of the Negev, Beer Sheva 84105 (Israel)
2013-11-04
We consider static spherically symmetric configurations in a Palatini extension of General Relativity including R{sup 2} and Ricci-squared terms, which is known to replace the central singularity by a wormhole in the electrovacuum case. We modify the matter sector of the theory by adding to the usual Maxwell term a nonlinear electromagnetic extension which is known to implement a confinement mechanism in flat space. One feature of the resulting theory is that the nonlinear electric field leads to a dynamically generated cosmological constant. We show that with this matter source the solutions of the model are asymptotically de Sitter and possess a wormhole topology. We discuss in some detail the conditions that guarantee the absence of singularities and of traversable wormholes.
Evidence for cosmological particle creation?
Energy Technology Data Exchange (ETDEWEB)
Pigozzo, C. [Imperial Centre for Inference and Cosmology, Imperial College, Prince Consort Road, London, SW7 2AZ (United Kingdom); Carneiro, S.; Borges, H.A. [Instituto de Física, Universidade Federal da Bahia, Rua Barão de Geremoabo, Salvador, 40210-340, BA (Brazil); Alcaniz, J.S. [Departamento de Astronomia, Observatório Nacional, Rua General José Cristino 77, Rio de Janeiro, 20921-400, RJ (Brazil); Fabris, J.C., E-mail: cpigozzo@ufba.br, E-mail: saulo.carneiro@pq.cnpq.br, E-mail: alcaniz@on.br, E-mail: humberto@ufba.br, E-mail: fabris@pq.cnpq.br [Departamento de Física, Universidade Federal do Espírito Santo, Av. Fernando Ferrari 514, Vitória, 29075-910, ES (Brazil)
2016-05-01
A joint analysis of the linear matter power spectrum, distance measurements from type Ia supernovae and the position of the first peak in the anisotropy spectrum of the cosmic microwave background indicates a cosmological, late-time dark matter creation at 95% confidence level.
International Nuclear Information System (INIS)
Schramm, D.N.
1995-01-01
Primordial nucleosynthesis has established itself as one of the three pillars of Big Bang cosmology. Many of the Big Bang Nucleosynthesis reactions involve unstable nuclei. Hence there is a tight relationship hetween the subject of this conference and cosmology. The prime role of unstable nuclei in cosmology is related to lithium synthesis and the lack of cosmological synthesis of Be and B. These nuclei will thus be focused upon. Nucleosynthesis involves comparing calculated abundances with observed abundances. In general, abundance determinations are dominated by systematic rather than statistical errors, and work on bounding systematics is crucial. The quark-hadron inspired inhomogeneous calculations now unanimously agree that only relatively small variations in Ω b are possible vis-a-vis the homogeneous model; hence the robustness of Ω b ∼0.05 is now apparent. (These calculations depend critically on unstable nuclei.) The above argues that the bulk of the baryons in the universe are not producing visible light. A comparison with the ROSAT cluster data is also shown to be consistent with the standard BBN model. Ω b ∼1 seems to be definitely excluded, so if Ω TOTAL =1, as some recent observations may hint, then non-baryonic dark matter is required. The implications of the recently reported halo microlensing events are discussed. In summary, it is argued that the physics of unstable nuclei affects the fundamental dark matter argument. ((orig.))
Energy Technology Data Exchange (ETDEWEB)
Turner, Michael S
1999-03-01
For two decades the hot big-bang model as been referred to as the standard cosmology - and for good reason. For just as long cosmologists have known that there are fundamental questions that are not answered by the standard cosmology and point to a grander theory. The best candidate for that grander theory is inflation + cold dark matter. It holds that the Universe is flat, that slowly moving elementary particles left over from the earliest moments provide the cosmic infrastructure, and that the primeval density inhomogeneities that seed all the structure arose from quantum fluctuations. There is now prima facie evidence that supports two basic tenets of this paradigm. An avalanche of high-quality cosmological observations will soon make this case stronger or will break it. Key questions remain to be answered; foremost among them are: identification and detection of the cold dark matter particles and elucidation of the dark-energy component. These are exciting times in cosmology{exclamation_point}.
International Nuclear Information System (INIS)
Leibundgut, B.
2005-01-01
Supernovae have developed into a versatile tool for cosmology. Their impact on the cosmological model has been profound and led to the discovery of the accelerated expansion. The current status of the cosmological model as perceived through supernova observations will be presented. Supernovae are currently the only astrophysical objects that can measure the dynamics of the cosmic expansion during the past eight billion years. Ongoing experiments are trying to determine the characteristics of the accelerated expansion and give insight into what might be the physical explanation for the acceleration. (author)
van den Aarssen, Laura G; Bringmann, Torsten; Pfrommer, Christoph
2012-12-07
The cold dark matter paradigm describes the large-scale structure of the Universe remarkably well. However, there exists some tension with the observed abundances and internal density structures of both field dwarf galaxies and galactic satellites. Here, we demonstrate that a simple class of dark matter models may offer a viable solution to all of these problems simultaneously. Their key phenomenological properties are velocity-dependent self-interactions mediated by a light vector messenger and thermal production with much later kinetic decoupling than in the standard case.
International Nuclear Information System (INIS)
Seljak, U.
2001-01-01
These lectures concentrate on evolution and generation of dark matter perturbations. The purpose of the lectures is to present, in a systematic way, a comprehensive review of the cosmological parameters that can lead to observable effects in the dark matter clustering properties. We begin by reviewing the relativistic linear perturbation theory formalism. We discuss the gauge issue and derive Einstein's and continuity equations for several popular gauge choices. We continue by developing fluid equations for cold dark matter and baryons and Boltzmann equations for photons, massive and massless neutrinos. We then discuss the generation of initial perturbations by the process of inflation and the parameters of that process that can be extracted from the observations. Finally we discuss evolution of perturbations in various regimes and the imprint of the evolution on the dark matter power spectrum both in the linear and in the nonlinear regime. (author)
Energy Technology Data Exchange (ETDEWEB)
Seljak, U [Department of Physics, Princeton University, Princeton, NJ (United States)
2001-11-15
These lectures concentrate on evolution and generation of dark matter perturbations. The purpose of the lectures is to present, in a systematic way, a comprehensive review of the cosmological parameters that can lead to observable effects in the dark matter clustering properties. We begin by reviewing the relativistic linear perturbation theory formalism. We discuss the gauge issue and derive Einstein's and continuity equations for several popular gauge choices. We continue by developing fluid equations for cold dark matter and baryons and Boltzmann equations for photons, massive and massless neutrinos. We then discuss the generation of initial perturbations by the process of inflation and the parameters of that process that can be extracted from the observations. Finally we discuss evolution of perturbations in various regimes and the imprint of the evolution on the dark matter power spectrum both in the linear and in the nonlinear regime. (author)
Statefinder diagnostic for cosmology with the abnormally weighting energy hypothesis
International Nuclear Information System (INIS)
Liu Daojun; Liu Weizhong
2008-01-01
In this paper, we apply the statefinder diagnostic to the cosmology with the abnormally weighting energy hypothesis (AWE cosmology), in which dark energy in the observational (ordinary matter) frame results from the violation of the weak equivalence principle by pressureless matter. It is found that there exist closed loops in the statefinder plane, which is an interesting characteristic of the evolution trajectories of statefinder parameters and can be used to distinguish AWE cosmology from other cosmological models
Merritt, David
2017-02-01
I argue that some important elements of the current cosmological model are 'conventionalist' in the sense defined by Karl Popper. These elements include dark matter and dark energy; both are auxiliary hypotheses that were invoked in response to observations that falsified the standard model as it existed at the time. The use of conventionalist stratagems in response to unexpected observations implies that the field of cosmology is in a state of 'degenerating problemshift' in the language of Imre Lakatos. I show that the 'concordance' argument, often put forward by cosmologists in support of the current paradigm, is weaker than the convergence arguments that were made in the past in support of the atomic theory of matter or the quantization of energy.
International Nuclear Information System (INIS)
Berstein, J.
1984-01-01
These lectures offer a self-contained review of the role of neutrinos in cosmology. The first part deals with the question 'What is a neutrino.' and describes in a historical context the theoretical ideas and experimental discoveries related to the different types of neutrinos and their properties. The basic differences between the Dirac neutrino and the Majorana neutrino are pointed out and the evidence for different neutrino 'flavours', neutrino mass, and neutrino oscillations is discussed. The second part summarizes current views on cosmology, particularly as they are affected by recent theoretical and experimental advances in high-energy particle physics. Finally, the close relationship between neutrino physics and cosmology is brought out in more detail, to show how cosmological constraints can limit the various theoretical possibilities for neutrinos and, more particularly, how increasing knowledge of neutrino properties can contribute to our understanding of the origin, history, and future of the Universe. The level is that of the beginning graduate student. (orig.)
Lesgourgues, Julien; Miele, Gennaro; Pastor, Sergio
2013-01-01
The role that neutrinos have played in the evolution of the Universe is the focus of one of the most fascinating research areas that has stemmed from the interplay between cosmology, astrophysics and particle physics. In this self-contained book, the authors bring together all aspects of the role of neutrinos in cosmology, spanning from leptogenesis to primordial nucleosynthesis, their role in CMB and structure formation, to the problem of their direct detection. The book starts by guiding the reader through aspects of fundamental neutrino physics, such as the standard cosmological model and the statistical mechanics in the expanding Universe, before discussing the history of neutrinos in chronological order from the very early stages until today. This timely book will interest graduate students and researchers in astrophysics, cosmology and particle physics, who work with either a theoretical or experimental focus.
International Nuclear Information System (INIS)
Zeldovich, Y.B.
1983-01-01
This paper fives a general review of modern cosmology. The following subjects are discussed: hot big bang and periodization of the evolution; Hubble expansion; the structure of the universe (pancake theory); baryon asymmetry; inflatory universe. (Auth.)
International Nuclear Information System (INIS)
Zeldovich, Ya.
1984-01-01
The knowledge is summed up of contemporary cosmology on the universe and its development resulting from a great number of highly sensitive observations and the application of contemporary physical theories to the entire universe. The questions are assessed of mass density in the universe, the structure and origin of the universe, its baryon asymmetry and the quantum explanation of the origin of the universe. Physical problems are presented which should be resolved for the future development of cosmology. (Ha)
CERN. Geneva
2007-01-01
The understanding of the Universe at the largest and smallest scales traditionally has been the subject of cosmology and particle physics, respectively. Studying the evolution of the Universe connects today's large scales with the tiny scales in the very early Universe and provides the link between the physics of particles and of the cosmos. This series of five lectures aims at a modern and critical presentation of the basic ideas, methods, models and observations in today's particle cosmology.
The cosmology/particle physics interface
International Nuclear Information System (INIS)
Olive, K.A.; Schramm, D.N.
1985-01-01
The paper reviews the interface between elementary particle physics and cosmology; and concentrates on inflation and the dark matter problem. Inflationary models of the Universe are examined, including phase transitions and supergravity. The three classes of dark matter problems discussed are: dynamical halos, galaxy formation and clustering, and the Ω=1 of inflation. Possible solutions to the cosmological dark matter problems are considered. (U.K.)
Cosmology [2011 European School of High-Energy Physics
Energy Technology Data Exchange (ETDEWEB)
Rubakov, V A [Moscow, INR (Russian Federation)
2014-07-01
In these lectures we first concentrate on the cosmological problems which, hopefully, have to do with the new physics to be probed at the LHC: the nature and origin of dark matter and generation of matter-antimatter asymmetry. We give several examples showing the LHC cosmological potential. These are WIMPs as cold dark matter, gravitinos as warm dark matter, and electroweak baryogenesis as a mechanism for generating matter-antimatter asymmetry. In the remaining part of the lectures we discuss the cosmological perturbations as a tool for studying the epoch preceeding the conventional hot stage of the cosmological evolution.
International Nuclear Information System (INIS)
Gelmini, G.B.
1996-01-01
These lectures are devoted to elementary particle physicists and assume the reader has very little or no knowledge of cosmology and astrophysics. After a brief historical introduction to the development of modern cosmology and astro-particles in which the Hot Big Bang model is defined, the Robertson-Walker metric and the dynamics of the Friedmann-Robertson-Walker cosmology are discussed in section 2. In section 3 the main observational features of the Universe are reviewed, including a description of our neighborhood, homogeneity and isotropy, the cosmic background radiation, the expansion, the age and the matter content of the Universe. A brief account of the thermal history of the Universe follows in section 4, and relic abundances are discussed in section 5. Section 6 is devoted to primordial nucleosynthesis, section 7 to structure formation in the Universe and section 8 to the possibility of detection of the dark matter in the halo of our galaxy. In the relevant sections recent developments are included, such as several so called open-quote open-quote crisis close-quote close-quote (the age crisis, the cluster baryon crisis and the nucleosynthesis crisis), and the MACHO events that may constitute the first detection of dark matter in the halo of our galaxy. copyright 1996 American Institute of Physics
International Nuclear Information System (INIS)
Gelmini, Graciela B.
1996-01-01
These lectures are devoted to elementary particle physicists and assume the reader has very little or no knowledge of cosmology and astrophysics. After a brief historical introduction to the development of modern cosmology and astro-particles in which the Hot Big Bang model is defined, the Robertson-Walker metric and the dynamics of the Friedmann-Robertson-Walker cosmology are discussed in section 2. In section 3 the main observational features of the Universe are reviewed, including a description of our neighborhood, homogeneity and isotropy, the cosmic background radiation, the expansion, the age and the matter content of the Universe. A brief account of the thermal history of the Universe follows in section 4, and relic abundances are discussed in section 5. Section 6 is devoted to primordial nucleosynthesis, section 7 to structure formation in the Universe and section 8 to the possibility of detection of the dark matter in the halo of our galaxy. In the relevant sections recent developments are included, such as several so called ''crisis'' (the age crisis, the cluster baryon crisis and the nucleosynthesis crisis), and the MACHO events that may constitute the first detection of dark matter in the halo of our galaxy
International Nuclear Information System (INIS)
Anchordoqui, Luis; Nawata, Satoshi; Goldberg, Haim; Nunez, Carlos
2007-01-01
We explore the cosmological content of Salam-Sezgin six-dimensional supergravity, and find a solution to the field equations in qualitative agreement with observation of distant supernovae, primordial nucleosynthesis abundances, and recent measurements of the cosmic microwave background. The carrier of the acceleration in the present de Sitter epoch is a quintessence field slowly rolling down its exponential potential. Intrinsic to this model is a second modulus which is automatically stabilized and acts as a source of cold dark matter, with a mass proportional to an exponential function of the quintessence field (hence realizing varying mass particle models within a string context). However, any attempt to saturate the present cold dark matter component in this manner leads to unacceptable deviations from cosmological data--a numerical study reveals that this source can account for up to about 7% of the total cold dark matter budget. We also show that (1) the model will support a de Sitter energy in agreement with observation at the expense of a miniscule breaking of supersymmetry in the compact space; (2) variations in the fine structure constant are controlled by the stabilized modulus and are negligible; (3) ''fifth'' forces are carried by the stabilized modulus and are short range; (4) the long time behavior of the model in four dimensions is that of a Robertson-Walker universe with a constant expansion rate (w=-1/3). Finally, we present a string theory background by lifting our six-dimensional cosmological solution to ten dimensions
Disformal theories of gravity: from the solar system to cosmology
Energy Technology Data Exchange (ETDEWEB)
Sakstein, Jeremy, E-mail: j.a.sakstein@damtp.cam.ac.uk [DAMTP, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)
2014-12-01
This paper is concerned with theories of gravity that contain a scalar coupled both conformally and disformally to matter through the metric. By systematically deriving the non-relativistic limit, it is shown that no new non-linear screening mechanisms are present beyond the Vainshtein mechanism and chameleon-like screening. If one includes the cosmological expansion of the universe, disformal effects that are usually taken to be absent can be present in the solar system. When the conformal factor is absent, fifth-forces can be screened on all scales when the cosmological field is slowly-rolling. We investigate the cosmology of these models and use local tests of gravity to place new constraints on the disformal coupling and find M ∼> O(eV), which is not competitive with laboratory tests. Finally, we discuss the future prospects for testing these theories and the implications for other theories of modified gravity. In particular, the Vainshtein radius of solar system objects can be altered from the static prediction when cosmological time-derivatives are non-negligible.
Disformal theories of gravity: from the solar system to cosmology
International Nuclear Information System (INIS)
Sakstein, Jeremy
2014-01-01
This paper is concerned with theories of gravity that contain a scalar coupled both conformally and disformally to matter through the metric. By systematically deriving the non-relativistic limit, it is shown that no new non-linear screening mechanisms are present beyond the Vainshtein mechanism and chameleon-like screening. If one includes the cosmological expansion of the universe, disformal effects that are usually taken to be absent can be present in the solar system. When the conformal factor is absent, fifth-forces can be screened on all scales when the cosmological field is slowly-rolling. We investigate the cosmology of these models and use local tests of gravity to place new constraints on the disformal coupling and find M ∼> O(eV), which is not competitive with laboratory tests. Finally, we discuss the future prospects for testing these theories and the implications for other theories of modified gravity. In particular, the Vainshtein radius of solar system objects can be altered from the static prediction when cosmological time-derivatives are non-negligible
International Nuclear Information System (INIS)
2006-01-01
This year's Nobel prize is welcome recognition for cosmology. Back in the 1960s, according to Paul Davies' new book The Goldilocks Enigma (see 'Seeking anthropic answers' in this issue), cynics used to quip that there is 'speculation, speculation squared - and cosmology'. Anyone trying to understand the origin and fate of the universe was, in other words, dealing with questions that were simply impractical - or even impossible - to answer. But that has all changed with the development of new telescopes, satellites and data-processing techniques - to the extent that cosmology is now generally viewed as a perfectly acceptable branch of science. If anyone was in any doubt of cosmology's new status, the Royal Swedish Academy of Sciences last month gave the subject welcome recognition with the award of this year's Nobel prize to John Mather and George Smoot (see pp6-7; print version only). The pair were the driving force behind the COBE satellite that in 1992 produced the now famous image of the cosmic microwave background. The mission's data almost certainly proved that the universe started with a Big Bang, while tiny fluctuations in the temperature signal between different parts of the sky were shown to be the seeds of the stars and galaxies we see today. These results are regarded by many as the start of a new era of 'precision cosmology'. But for cosmologists, the job is far from over. There are still massive holes in our understanding of the cosmos, notably the nature of dark matter and dark energy, which together account for over 95% of the total universe. Indeed, some regard dark energy and matter as just ad hoc assumptions needed to fit the data. (Hypothetical particles called 'axions' are one possible contender for dark matter (see pp20-23; print version only), but don't bet your house on it.) Some physicists even think it makes more sense to adjust Newtonian gravity rather than invoke dark matter. But the notion that cosmology is in crisis, as argued by some
Tunable rotary orbits of matter-wave nonlinear modes in attractive Bose-Einstein condensates
International Nuclear Information System (INIS)
He, Y J; Wang, H Z; Malomed, Boris A; Mihalache, Dumitru
2008-01-01
We demonstrate that by spatially modulating the Bessel optical lattice where a Bose-Einstein condensate is loaded, we get tunable rotary orbits of nonlinear lattice modes. We show that the radially expanding or shrinking Bessel lattice can drag the nonlinear localized modes to orbits of either larger or smaller radii and the rotary velocity of nonlinear modes can be changed accordingly. The localized modes can even be transferred to the Bessel lattice core when the localized modes' rotations are stopped. Effects beyond the quasi-particle approximation such as destruction of the nonlinear modes by nonadiabatic dragging are also explored
On estimating cosmology-dependent covariance matrices
International Nuclear Information System (INIS)
Morrison, Christopher B.; Schneider, Michael D.
2013-01-01
We describe a statistical model to estimate the covariance matrix of matter tracer two-point correlation functions with cosmological simulations. Assuming a fixed number of cosmological simulation runs, we describe how to build a 'statistical emulator' of the two-point function covariance over a specified range of input cosmological parameters. Because the simulation runs with different cosmological models help to constrain the form of the covariance, we predict that the cosmology-dependent covariance may be estimated with a comparable number of simulations as would be needed to estimate the covariance for fixed cosmology. Our framework is a necessary first step in planning a simulations campaign for analyzing the next generation of cosmological surveys
Backreaction mechanism in multifluid and extended cosmologies
Energy Technology Data Exchange (ETDEWEB)
Jiménez, Jose Beltrán [Centre for Cosmology, Particle Physics and Phenomenology, Institute of Mathematics and Physics, Louvain University, 2 Chemin du Cyclotron, 1348 Louvain-la-Neuve (Belgium); Cruz-Dombriz, Álvaro de la [Departamento de Física Teórica I, Ciudad Universitaria, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Dunsby, Peter K.S.; Sáez-Gómez, Diego, E-mail: jose.beltran@uclouvain.be, E-mail: dombriz@fis.ucm.es, E-mail: peter.dunsby@uct.ac.za, E-mail: diego.saezgomez@uct.ac.za [Astrophysics, Cosmology and Gravity Centre (ACGC), University of Cape Town, Rondebosch 7701, Cape Town (South Africa)
2014-05-01
One possible explanation for the present observed acceleration of the Universe is the breakdown of homogeneity and isotropy due to the formation of non-linear structures. How inhomogeneities affect the averaged cosmological expansion rate and lead to late-time acceleration is generally considered to be due to some backreaction mechanism. In the recent literature most averaging calculations have focused their attention on General Relativity together with pressure-free matter. In this communication we focus our attention on more general scenarios, including imperfect fluids as well as alternative theories of gravity, and apply an averaging procedure to them in order to determine possible backreaction effects. For illustrative purposes, we present our results for dark energy models, quintessence and Brans-Dicke theories. We also provide a discussion about the limitations of frame choices in the averaging procedure.
Particle physics and cosmology
International Nuclear Information System (INIS)
Srednicki, M.
1990-01-01
At least eighty percent of the mass of the universe consists of some material which, unlike ordinary matter, neither emits nor absorbs light. This book collects key papers related to the discovery of this astonishing fact and its profound implications for astrophysics, cosmology, and the physics of elementary particles. The book focusses on the likely possibility that the dark matter is composed of an as yet undiscovered elementary particle, and examines the boundaries of our present knowledge of the properties such a particle must possess. (author). refs.; figs.; tabs
Cosmological tests of coupled Galileons
International Nuclear Information System (INIS)
Brax, Philippe; Burrage, Clare; Davis, Anne-Christine; Gubitosi, Giulia
2015-01-01
We investigate the cosmological properties of Galileon models which admit Minkowski space as a stable solution in vacuum. This is motivated by stable, positive tension brane world constructions that give rise to Galileons. We include both conformal and disformal couplings to matter and focus on constraints on the theory that arise because of these couplings. The disformal coupling to baryonic matter is extremely constrained by astrophysical and particle physics effects. The disformal coupling to photons induces a cosmological variation of the speed of light and therefore distorsions of the Cosmic Microwave Background spectrum which are known to be very small. The conformal coupling to baryons leads to a variation of particle masses since Big Bang Nucleosynthesis which is also tightly constrained. We consider the background cosmology of Galileon models coupled to Cold Dark Matter (CDM), photons and baryons and impose that the speed of light and particle masses respect the observational bounds on cosmological time scales. We find that requiring that the equation of state for the Galileon models must be close to -1 now restricts severely their parameter space and can only be achieved with a combination of the conformal and disformal couplings. This leads to large variations of particle masses and the speed of light which are not compatible with observations. As a result, we find that cosmological Galileon models are viable dark energy theories coupled to dark matter but their couplings, both disformal and conformal, to baryons and photons must be heavily suppressed making them only sensitive to CDM
International Nuclear Information System (INIS)
Li, Z.; Zhuo, Y.; Li, Z.; Mao, G.; Zhuo, Y.; Mao, G.; Greiner, W.
1997-01-01
An investigation of the transition to Δ matter is performed based on a relativistic mean field formulation of the nonlinear σ and ω model. We demonstrate that in addition to the Δ-meson coupling, the occurrence of the baryon resonance isomer also depends on the nucleon-meson coupling. Our results show that for the favored phenomenological value of m * and K, the Δ isomer exists at baryon density ∼2 3ρ 0 if β=1.31 is adopted. For universal coupling of the nucleon and Δ, the Δ density at baryon density ∼2 3ρ 0 and temperature ∼0.4 0.5 fm -1 is about normal nuclear matter density, which is in accord with a recent experimental finding. copyright 1997 The American Physical Society
Particle physics and cosmology, Task C
International Nuclear Information System (INIS)
Turner, M.S.
1993-05-01
The research has spanned many topics at the boundary of particle physics and cosmology. The major focus has been in the general areas of inflationary cosmology, cosmological phase transitions, astrophysical constraints to particle physics theories, and dark matter/structure formation as it relates to particle physics. Some attention is given to axion physics. Narrative summaries of the research of the individual group members are given, followed by a list of publications
International Nuclear Information System (INIS)
Tkachev, Igor
1993-01-01
When the common ground between particle physics, astrophysics and cosmology started to become a developing area, the Institute for Nuclear Research (INR) of the Russian Academy of Sciences had the foresight in 1981 to institute the Baksan Schools on Particles and Cosmology. This now traditional event, held biannually in the Baksan Valley, has gone on to attract international participation. The site is close to the INR Baksan Neutrino Observatory with its underground and surface installations, including the SAGE gallium solar neutrino detector, the Underground Scintillation Telescope, and the 'Carpet' extensive air shower array. Participation is mainly from experimentalists working in non accelerator particle physics and particle astrophysics. The most recent School, held from April 21 to 28, began with an opening address by INR Director V. A. Matveev. J.Frieman reviewed standard big bang cosmology, emphasizing how the recent COBE results and the observations of large scale galaxy clustering fit into a standard cosmology framework. For inflationary cosmology, he showed how different models may be tested through their predictions for large-scale galactic structure and for cosmic microwave background anisotropy. A.Stebbins presented details of the large scale distribution of galaxies which, combined with velocity information and microwave background anisotropy data, provide strong constraints on theories of the origin of primordial inhomogeneities. Inflation requires, and theories of the large scale structure strongly favour the critical value for the cosmic mass density, while, as D.Seckel explained in his lecture on nucleosynthesis and abundances of the light elements, the baryon contribution to this density has to be tens of times smaller. A general review on the observational evidence for dark matter, dark matter particle candidates and the strategy of dark matter searches was given by I. Tkachev, who stressed the gravitational microlensing MACHO
Modified geodetic brane cosmology
International Nuclear Information System (INIS)
Cordero, Rubén; Cruz, Miguel; Molgado, Alberto; Rojas, Efraín
2012-01-01
We explore the cosmological implications provided by the geodetic brane gravity action corrected by an extrinsic curvature brane term, describing a codimension-1 brane embedded in a 5D fixed Minkowski spacetime. In the geodetic brane gravity action, we accommodate the correction term through a linear term in the extrinsic curvature swept out by the brane. We study the resulting geodetic-type equation of motion. Within a Friedmann–Robertson–Walker metric, we obtain a generalized Friedmann equation describing the associated cosmological evolution. We observe that, when the radiation-like energy contribution from the extra dimension is vanishing, this effective model leads to a self-(non-self)-accelerated expansion of the brane-like universe in dependence on the nature of the concomitant parameter β associated with the correction, which resembles an analogous behaviour in the DGP brane cosmology. Several possibilities in the description for the cosmic evolution of this model are embodied and characterized by the involved density parameters related in turn to the cosmological constant, the geometry characterizing the model, the introduced β parameter as well as the dark-like energy and the matter content on the brane. (paper)
On the cosmology of scalar-tensor-vector gravity theory
Jamali, Sara; Roshan, Mahmood; Amendola, Luca
2018-01-01
We consider the cosmological consequences of a special scalar-tensor-vector theory of gravity, known as MOG (for MOdified Gravity), proposed to address the dark matter problem. This theory introduces two scalar fields G(x) and μ(x), and one vector field phiα(x), in addition to the metric tensor. We set the corresponding self-interaction potentials to zero, as in the standard form of MOG. Then using the phase space analysis in the flat Friedmann-Robertson-Walker background, we show that the theory possesses a viable sequence of cosmological epochs with acceptable time dependency for the cosmic scale factor. We also investigate MOG's potential as a dark energy model and show that extra fields in MOG cannot provide a late time accelerated expansion. Furthermore, using a dynamical system approach to solve the non-linear field equations numerically, we calculate the angular size of the sound horizon, i.e. θs, in MOG. We find that 8× 10‑3rad<θs<8.2× 10‑3 rad which is way outside the current observational bounds. Finally, we generalize MOG to a modified form called mMOG, and we find that mMOG passes the sound-horizon constraint. However, mMOG also cannot be considered as a dark energy model unless one adds a cosmological constant, and more importantly, the matter dominated era is still slightly different from the standard case.
The Higgs Portal and Cosmology
Energy Technology Data Exchange (ETDEWEB)
Assamagan, Ketevi [Brookhaven National Lab. (BNL), Upton, NY (United States); Chen, Chien-Yi [Perimeter Inst. for Theoretical Physics, Waterloo, ON (Canada); Univ. of Victoria, BC (Canada); Chou, John Paul [Rutgers Univ., Piscataway, NJ (United States); Curtin, David [Univ. of Maryland, College Park, MD (United States); Fedderke, Michael A. [Univ. of Chicago, IL (United States); Gershtein, Yuri [Rutgers Univ., Piscataway, NJ (United States); He, Xiao-Gang [Shanghai Jiao Tong Univ. (China); Klute, Markus [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Kozaczuk, Jonathon [TRIUMF, Vancouver, BC (Canada); Kotwal, Ashutosh [Duke Univ., Durham, NC (United States); Lowette, Steven [Vrije Univ., Brussels (Belgium); No, Jose Miguel [Univ. of Sussex, Brighton (United Kingdom); Plehn, Tilman [Heidelberg Univ. (Germany); Qian, Jianming [Univ. of Michigan, Ann Arbor, MI (United States); Ramsey-Musolf, Michael [Univ. of Massachusetts, Amherst, MA (United States); Safonov, Alexei [Texas A & M Univ., College Station, TX (United States); Shelton, Jessie [Univ. of Illinois, Urbana-Champaign, IL (United States); Spannowsky, Michael [Durham Univ. (United Kingdom); Su, Shufang [Univ. of Arizona, Tucson, AZ (United States); Walker, Devin G. E. [Univ. of Washington, Seattle, WA (United States); Willocq, Stephane [Univ. of Massachusetts, Amherst, MA (United States); Winslow, Peter [Univ. of Massachusetts, Amherst, MA (United States)
2016-04-18
Higgs portal interactions provide a simple mechanism for addressing two open problems in cosmology: dark matter and the baryon asymmetry. In the latter instance, Higgs portal interactions may contain the ingredients for a strong first-order electroweak phase transition as well as new CP-violating interactions as needed for electroweak baryogenesis. These interactions may also allow for a viable dark matter candidate. We survey the opportunities for probing the Higgs portal as it relates to these questions in cosmology at the LHC and possible future colliders.
Lucchin, Francesco; Matarrese, Sabino; Melott, Adrian L.; Moscardini, Lauro
1994-01-01
We calculate reduced moments (xi bar)(sub q) of the matter density fluctuations, up to order q = 5, from counts in cells produced by particle-mesh numerical simulations with scale-free Gaussian initial conditions. We use power-law spectra P(k) proportional to k(exp n) with indices n = -3, -2, -1, 0, 1. Due to the supposed absence of characteristic times or scales in our models, all quantities are expected to depend on a single scaling variable. For each model, the moments at all times can be expressed in terms of the variance (xi bar)(sub 2), alone. We look for agreement with the hierarchical scaling ansatz, according to which ((xi bar)(sub q)) proportional to ((xi bar)(sub 2))(exp (q - 1)). For n less than or equal to -2 models, we find strong deviations from the hierarchy, which are mostly due to the presence of boundary problems in the simulations. A small, residual signal of deviation from the hierarchical scaling is however also found in n greater than or equal to -1 models. The wide range of spectra considered and the large dynamic range, with careful checks of scaling and shot-noise effects, allows us to reliably detect evolution away from the perturbation theory result.
FRW Cosmological Perturbations in Massive Bigravity
Comelli, D; Pilo, L
2014-01-01
Cosmological perturbations of FRW solutions in ghost free massive bigravity, including also a second matter sector, are studied in detail. At early time, we find that sub horizon exponential instabilities are unavoidable and they lead to a premature departure from the perturbative regime of cosmological perturbations.
iCosmo: an interactive cosmology package
Refregier, A.; Amara, A.; Kitching, T. D.; Rassat, A.
2011-04-01
Aims: The interactive software package iCosmo, designed to perform cosmological calculations is described. Methods: iCosmo is a software package to perfom interactive cosmological calculations for the low-redshift universe. Computing distance measures, the matter power spectrum, and the growth factor is supported for any values of the cosmological parameters. It also computes derived observed quantities for several cosmological probes such as cosmic shear, baryon acoustic oscillations, and type Ia supernovae. The associated errors for these observable quantities can be derived for customised surveys, or for pre-set values corresponding to current or planned instruments. The code also allows for calculation of cosmological forecasts with Fisher matrices, which can be manipulated to combine different surveys and cosmological probes. The code is written in the IDL language and thus benefits from the convenient interactive features and scientific libraries available in this language. iCosmo can also be used as an engine to perform cosmological calculations in batch mode, and forms a convenient adaptive platform for the development of further cosmological modules. With its extensive documentation, it may also serve as a useful resource for teaching and for newcomers to the field of cosmology. Results: The iCosmo package is described with a number of examples and command sequences. The code is freely available with documentation at http://www.icosmo.org, along with an interactive web interface and is part of the Initiative for Cosmology, a common archive for cosmological resources.
International Nuclear Information System (INIS)
Dickau, Jonathan J.
2009-01-01
The use of fractals and fractal-like forms to describe or model the universe has had a long and varied history, which begins long before the word fractal was actually coined. Since the introduction of mathematical rigor to the subject of fractals, by Mandelbrot and others, there have been numerous cosmological theories and analyses of astronomical observations which suggest that the universe exhibits fractality or is by nature fractal. In recent years, the term fractal cosmology has come into usage, as a description for those theories and methods of analysis whereby a fractal nature of the cosmos is shown.
Disformal transformation of cosmological perturbations
Directory of Open Access Journals (Sweden)
Masato Minamitsuji
2014-10-01
Full Text Available We investigate the gauge-invariant cosmological perturbations in the gravity and matter frames in the general scalar–tensor theory where two frames are related by the disformal transformation. The gravity and matter frames are the extensions of the Einstein and Jordan frames in the scalar–tensor theory where two frames are related by the conformal transformation, respectively. First, it is shown that the curvature perturbation in the comoving gauge to the scalar field is disformally invariant as well as conformally invariant, which gives the predictions from the cosmological model where the scalar field is responsible both for inflation and cosmological perturbations. Second, in case that the disformally coupled matter sector also contributes to curvature perturbations, we derive the evolution equations of the curvature perturbation in the uniform matter energy density gauge from the energy (nonconservation in the matter sector, which are independent of the choice of the gravity sector. While in the matter frame the curvature perturbation in the uniform matter energy density gauge is conserved on superhorizon scales for the vanishing nonadiabatic pressure, in the gravity frame it is not conserved even if the nonadiabatic pressure vanishes. The formula relating two frames gives the amplitude of the curvature perturbation in the matter frame, once it is evaluated in the gravity frame.
Disformal transformation of cosmological perturbations
International Nuclear Information System (INIS)
Minamitsuji, Masato
2014-01-01
We investigate the gauge-invariant cosmological perturbations in the gravity and matter frames in the general scalar–tensor theory where two frames are related by the disformal transformation. The gravity and matter frames are the extensions of the Einstein and Jordan frames in the scalar–tensor theory where two frames are related by the conformal transformation, respectively. First, it is shown that the curvature perturbation in the comoving gauge to the scalar field is disformally invariant as well as conformally invariant, which gives the predictions from the cosmological model where the scalar field is responsible both for inflation and cosmological perturbations. Second, in case that the disformally coupled matter sector also contributes to curvature perturbations, we derive the evolution equations of the curvature perturbation in the uniform matter energy density gauge from the energy (non)conservation in the matter sector, which are independent of the choice of the gravity sector. While in the matter frame the curvature perturbation in the uniform matter energy density gauge is conserved on superhorizon scales for the vanishing nonadiabatic pressure, in the gravity frame it is not conserved even if the nonadiabatic pressure vanishes. The formula relating two frames gives the amplitude of the curvature perturbation in the matter frame, once it is evaluated in the gravity frame
Heavy ion collisions and cosmology
Energy Technology Data Exchange (ETDEWEB)
Floerchinger, Stefan
2016-12-15
There are interesting parallels between the physics of heavy ion collisions and cosmology. Both systems are out-of-equilibrium and relativistic fluid dynamics plays an important role for their theoretical description. From a comparison one can draw interesting conclusions for both sides. For heavy ion physics it could be rewarding to attempt a theoretical description of fluid perturbations similar to cosmological perturbation theory. In the context of late time cosmology, it could be interesting to study dissipative properties such as shear and bulk viscosity and corresponding relaxation times in more detail. Knowledge and experience from heavy ion physics could help to constrain the microscopic properties of dark matter from observational knowledge of the cosmological fluid properties.
Newtonian cosmology Newton would understand
International Nuclear Information System (INIS)
Lemons, D.S.
1988-01-01
Isaac Newton envisioned a static, infinite, and initially uniform, zero field universe that was gravitationally unstable to local condensations of matter. By postulating the existence of such a universe and using it as a boundary condition on Newtonian gravity, a new field equation for gravity is derived, which differs from the classical one by a time-dependent cosmological term proportional to the average mass density of the universe. The new field equation not only makes Jeans' analysis of the gravitational instability of a Newtonian universe consistent, but also gives rise to a family of Newtonian evolutionary cosmologies parametrized by a time-invariant expansion velocity. This Newtonian cosmology contrasts with both 19th-century ones and with post general relativity Newtonian cosmology
Physical and Relativistic Numerical Cosmology.
Anninos, Peter
1998-01-01
In order to account for the observable Universe, any comprehensive theory or model of cosmology must draw from many disciplines of physics, including gauge theories of strong and weak interactions, the hydrodynamics and microphysics of baryonic matter, electromagnetic fields, and spacetime curvature, for example. Although it is difficult to incorporate all these physical elements into a single complete model of our Universe, advances in computing methods and technologies have contributed significantly towards our understanding of cosmological models, the Universe, and astrophysical processes within them. A sample of numerical calculations addressing specific issues in cosmology are reviewed in this article: from the Big Bang singularity dynamics to the fundamental interactions of gravitational waves; from the quark-hadron phase transition to the large scale structure of the Universe. The emphasis, although not exclusively, is on those calculations designed to test different models of cosmology against the observed Universe.
Physical and Relativistic Numerical Cosmology
Directory of Open Access Journals (Sweden)
Peter Anninos
1998-01-01
Full Text Available In order to account for the observable Universe, any comprehensive theory or model of cosmology must draw from many disciplines of physics, including gauge theories of strong and weak interactions, the hydrodynamics and microphysics of baryonic matter, electromagnetic fields, and spacetime curvature, for example. Although it is difficult to incorporate all these physical elements into a single complete model of our Universe, advances in computing methods and technologies have contributed significantly towards our understanding of cosmological models, the Universe, and astrophysical processes within them. A sample of numerical calculations addressing specific issues in cosmology are reviewed in this article: from the Big Bang singularity dynamics to the fundamental interactions of gravitational waves; from the quark--hadron phase transition to the large scale structure of the Universe. The emphasis, although not exclusively, is on those calculations designed to test different models of cosmology against the observed Universe.
Self-accelerating universe in Galileon cosmology
International Nuclear Information System (INIS)
Silva, Fabio P.; Koyama, Kazuya
2009-01-01
We present a cosmological model with a solution that self-accelerates at late times without signs of ghost instabilities on small scales. The model is a natural extension of the Brans-Dicke (BD) theory including a nonlinear derivative interaction, which appears in a theory with the Galilean shift symmetry. The existence of the self-accelerating universe requires a negative BD parameter but, thanks to the nonlinear term, small fluctuations around the solution are stable on small scales. General relativity is recovered at early times and on small scales by this nonlinear interaction via the Vainshtein mechanism. At late time, gravity is strongly modified and the background cosmology shows a phantomlike behavior and the growth rate of structure formation is enhanced. Thus this model leaves distinct signatures in cosmological observations and it can be distinguished from standard LCDM cosmology.
Neutrino mass constraints from joint cosmological probes.
Kwan, Juliana
2018-01-01
One of the most promising avenues to come from precision cosmology is the measurement of the sum of neutrino masses in the next 5-10 years. Ongoing imaging surveys, such as the Dark Energy Survey and the Hyper Suprime Cam survey, will cover a substantial volume of the sky and when combined with existing spectroscopic data, are expected to deliver a definitive measurement in the near future. But it is important that the accuracy of theoretical predictions matches the precision of the observational data so that the neutrino mass signal can be properly detected without systematic error. To this end, we have run a suite of high precision, large volume cosmological N-body simulations containing massive neutrinos to quantify their effect on probes of large scale structure such as weak lensing and galaxy clustering. In this talk, I will describe the analytical tools that we have developed to extract the neutrino mass that are capable of fully utilizing the non-linear regime of structure formation. These include predictions for the bias in the clustering of dark matter halos (one of the fundamental ingredients of the halo model) with an error of only a few percent.
Bojowald, Martin
2015-02-01
In quantum cosmology, one applies quantum physics to the whole universe. While no unique version and no completely well-defined theory is available yet, the framework gives rise to interesting conceptual, mathematical and physical questions. This review presents quantum cosmology in a new picture that tries to incorporate the importance of inhomogeneity. De-emphasizing the traditional minisuperspace view, the dynamics is rather formulated in terms of the interplay of many interacting 'microscopic' degrees of freedom that describe the space-time geometry. There is thus a close relationship with more-established systems in condensed-matter and particle physics even while the large set of space-time symmetries (general covariance) requires some adaptations and new developments. These extensions of standard methods are needed both at the fundamental level and at the stage of evaluating the theory by effective descriptions.
Massive neutrinos and cosmology
International Nuclear Information System (INIS)
Shandarin, S.F.
1991-01-01
This paper discussed the importance of the consequences of a nonzero neutrino rest mass on cosmology, perhaps, first recognized by Gershtein and Zeldovich, after the discover of the 3-K microwave background radiation MBR. Since the first works on the primordial synthesis of 4 He, it has been known that additional neutrino species increase the rate of expansion of the universe during the epoch of the primordial nucleosynthesis, which increases the yield of 4 He. Combining the results of the theory with astronomical measurements of the 4 He abundance and the estimate of the mass density of MBR, Shvartsman suggested the upper limit on the mass density of all relativistic matter at that epoch: ρ rel ≤ 5ρ MBR which eventually became the upper limit for the number of neutrino species: N ν ≤ 7. At that time, the constraints based on cosmological arguments were much stronger than one based on laboratory experiments
Cosmology, inflation, and supersymmetry
International Nuclear Information System (INIS)
Albrecht, A.; Dimopoulos, S.; Fischler, W.; Kolb, E.W.; Raby, S.; Steinhardt, P.J.
1982-01-01
Cosmological consequences of supersymmetric grand unified models based on the Witten-O'Raifeartaigh potential are discussed. In particular we study the development of the phase transition in the spontaneous breaking of supersymmetry. We find that in realistic models where light fields feel supersymmetry breaking only through coupling to massive fields, e.g., the Geometric Hierarchy model, the universe does not inflate or reheat. Thus, the standard cosmological flatness, monopole, and horizon problems remain. In addition, we find that the transition is never completed, in the sense that the universe remains dominated by coherent Higgs field energy, resulting in an apparent matter dominated universe with Ω greater than or equal to 10 30
Enqvist, K
2012-01-01
The very basics of cosmological inflation are discussed. We derive the equations of motion for the inflaton field, introduce the slow-roll parameters, and present the computation of the inflationary perturbations and their connection to the temperature fluctuations of the cosmic microwave background.
Ellis, G F R
1993-01-01
Many topics were covered in the submitted papers, showing much life in this subject at present. They ranged from conventional calculations in specific cosmological models to provocatively speculative work. Space and time restrictions required selecting from them, for summarisation here; the book of Abstracts should be consulted for a full overview.
N-body simulations for coupled scalar-field cosmology
International Nuclear Information System (INIS)
Li Baojiu; Barrow, John D.
2011-01-01
We describe in detail the general methodology and numerical implementation of consistent N-body simulations for coupled-scalar-field models, including background cosmology and the generation of initial conditions (with the different couplings to different matter species taken into account). We perform fully consistent simulations for a class of coupled-scalar-field models with an inverse power-law potential and negative coupling constant, for which the chameleon mechanism does not work. We find that in such cosmological models the scalar-field potential plays a negligible role except in the background expansion, and the fifth force that is produced is proportional to gravity in magnitude, justifying the use of a rescaled gravitational constant G in some earlier N-body simulation works for similar models. We then study the effects of the scalar coupling on the nonlinear matter power spectra and compare with linear perturbation calculations to see the agreement and places where the nonlinear treatment deviates from the linear approximation. We also propose an algorithm to identify gravitationally virialized matter halos, trying to take account of the fact that the virialization itself is also modified by the scalar-field coupling. We use the algorithm to measure the mass function and study the properties of dark-matter halos. We find that the net effect of the scalar coupling helps produce more heavy halos in our simulation boxes and suppresses the inner (but not the outer) density profile of halos compared with the ΛCDM prediction, while the suppression weakens as the coupling between the scalar field and dark-matter particles increases in strength.
Some aspects of symmetrical relativistic cosmology
International Nuclear Information System (INIS)
Goto, M.
1977-01-01
A qualitative study of the cosmological model of Omnes is presented, as well as some numerical results. Studies are made in a chronological or historical way involving several subjects like matter and anti-matter emulsions, density of galactic clusters, the annihilation problem, quasars, etc. One solution for the matter diffusion equation is presented
Ultracompact Minihalos as Probes of Inflationary Cosmology.
Aslanyan, Grigor; Price, Layne C; Adams, Jenni; Bringmann, Torsten; Clark, Hamish A; Easther, Richard; Lewis, Geraint F; Scott, Pat
2016-09-30
Cosmological inflation generates primordial density perturbations on all scales, including those far too small to contribute to the cosmic microwave background. At these scales, isolated ultracompact minihalos of dark matter can form well before standard structure formation, if the perturbations have sufficient amplitude. Minihalos affect pulsar timing data and are potentially bright sources of gamma rays. The resulting constraints significantly extend the observable window of inflation in the presence of cold dark matter, coupling two of the key problems in modern cosmology.
Brane cosmology in teleparallel and f (T ) gravity
International Nuclear Information System (INIS)
Atazadeh, K; Eghbali, A
2015-01-01
We consider the cosmology of a brane-world scenario in the framework of teleparallel and f(T) gravity in a way that matter is localized on the brane. We show that the cosmology of such branes is different from the standard cosmology in teleparallelism. In particular, we obtain a class of new solutions with a constant five-dimensional radius and cosmologically evolving brane in the context of constant torsion f(T) gravity. (paper)
The Higgs boson and cosmology.
Shaposhnikov, Mikhail
2015-01-13
I will discuss how the Higgs field of the Standard Model may have played an important role in cosmology, leading to the homogeneity, isotropy and flatness of the Universe; producing the quantum fluctuations that seed structure formation; triggering the radiation-dominated era of the hot Big Bang; and contributing to the processes of baryogenesis and dark matter production.
Shaposhnikov, Mikhail
2015-01-01
I will discuss how the Higgs field of the Standard Model may have played an important role in cosmology, leading to the homogeneity, isotropy and flatness of the Universe; producing the quantum fluctuations that seed structure formation; triggering the radiation-dominated era of the hot Big Bang; and contributing to the processes of baryogenesis and dark matter production.
A natural cosmological constant from chameleons
International Nuclear Information System (INIS)
Nastase, Horatiu; Weltman, Amanda
2015-01-01
We present a simple model where the effective cosmological constant appears from chameleon scalar fields. For a Kachru–Kallosh–Linde–Trivedi (KKLT)-inspired form of the potential and a particular chameleon coupling to the local density, patches of approximately constant scalar field potential cluster around regions of matter with density above a certain value, generating the effect of a cosmological constant on large scales. This construction addresses both the cosmological constant problem (why Λ is so small, yet nonzero) and the coincidence problem (why Λ is comparable to the matter density now)
A natural cosmological constant from chameleons
Directory of Open Access Journals (Sweden)
Horatiu Nastase
2015-07-01
Full Text Available We present a simple model where the effective cosmological constant appears from chameleon scalar fields. For a Kachru–Kallosh–Linde–Trivedi (KKLT-inspired form of the potential and a particular chameleon coupling to the local density, patches of approximately constant scalar field potential cluster around regions of matter with density above a certain value, generating the effect of a cosmological constant on large scales. This construction addresses both the cosmological constant problem (why Λ is so small, yet nonzero and the coincidence problem (why Λ is comparable to the matter density now.
A natural cosmological constant from chameleons
Energy Technology Data Exchange (ETDEWEB)
Nastase, Horatiu, E-mail: nastase@ift.unesp.br [Instituto de Física Teórica, UNESP-Universidade Estadual Paulista, R. Dr. Bento T. Ferraz 271, Bl. II, Sao Paulo 01140-070, SP (Brazil); Weltman, Amanda, E-mail: amanda.weltman@uct.ac.za [Astrophysics, Cosmology & Gravity Center, Department of Mathematics and Applied Mathematics, University of Cape Town, Private Bag, Rondebosch 7700 (South Africa)
2015-07-30
We present a simple model where the effective cosmological constant appears from chameleon scalar fields. For a Kachru–Kallosh–Linde–Trivedi (KKLT)-inspired form of the potential and a particular chameleon coupling to the local density, patches of approximately constant scalar field potential cluster around regions of matter with density above a certain value, generating the effect of a cosmological constant on large scales. This construction addresses both the cosmological constant problem (why Λ is so small, yet nonzero) and the coincidence problem (why Λ is comparable to the matter density now)
Laudyn, Urszula A; Jung, Paweł S; Zegadło, Krzysztof B; Karpierz, Miroslaw A; Assanto, Gaetano
2014-11-15
We demonstrate the evolution of higher order one-dimensional guided modes into two-dimensional solitary waves in a reorientational medium. The observations, carried out at two different wavelengths in chiral nematic liquid crystals, are in good agreement with a simple nonlocal nonlinear model.
International Nuclear Information System (INIS)
Boyd, R.W.
1992-01-01
Nonlinear optics is the study of the interaction of intense laser light with matter. This book is a textbook on nonlinear optics at the level of a beginning graduate student. The intent of the book is to provide an introduction to the field of nonlinear optics that stresses fundamental concepts and that enables the student to go on to perform independent research in this field. This book covers the areas of nonlinear optics, quantum optics, quantum electronics, laser physics, electrooptics, and modern optics
Grant, E.; Murdin, P.
2000-11-01
During the early Middle Ages (ca 500 to ca 1130) scholars with an interest in cosmology had little useful and dependable literature. They relied heavily on a partial Latin translation of PLATO's Timaeus by Chalcidius (4th century AD), and on a series of encyclopedic treatises associated with the names of Pliny the Elder (ca AD 23-79), Seneca (4 BC-AD 65), Macrobius (fl 5th century AD), Martianus ...
International Nuclear Information System (INIS)
Partridge, R.B.
1977-01-01
Some sixty years after the development of relativistic cosmology by Einstein and his colleagues, observations are finally beginning to have an important impact on our views of the Universe. The available evidence seems to support one of the simplest cosmological models, the hot Big Bang model. The aim of this paper is to assess the observational support for certain assumptions underlying the hot Big Bang model. These are that the Universe is isobaric and homogeneous on a large scale; that it is expanding from an initial state of high density and temperature; and that the proper theory to describe the dynamics of the Universe is unmodified General Relativity. The properties of the cosmic microwave background radiation and recent observations of the abundance of light elements, in particular, support these assumptions. Also examined here are the data bearing on the related questions of the geometry and the future of the Universe (is it ever-expanding, or fated to recollapse). Finally, some difficulties and faults of the standard model are discussed, particularly various aspects of the 'initial condition' problem. It appears that the simplest Big Bang cosmological model calls for a highly specific set of initial conditions to produce the presently observed properties of the Universe. (Auth.)
the Universe About Cosmology Planck Satellite Launched Cosmology Videos Professor George Smoot's group conducts research on the early universe (cosmology) using the Cosmic Microwave Background radiation (CMB science goals regarding cosmology. George Smoot named Director of Korean Cosmology Institute The GRB
International Nuclear Information System (INIS)
Wang Xiaomin; Tegmark, Max; Zaldarriaga, Matias
2002-01-01
We perform a detailed analysis of the latest cosmic microwave background (CMB) measurements (including BOOMERaNG, DASI, Maxima and CBI), both alone and jointly with other cosmological data sets involving, e.g., galaxy clustering and the Lyman Alpha Forest. We first address the question of whether the CMB data are internally consistent once calibration and beam uncertainties are taken into account, performing a series of statistical tests. With a few minor caveats, our answer is yes, and we compress all data into a single set of 24 bandpowers with associated covariance matrix and window functions. We then compute joint constraints on the 11 parameters of the 'standard' adiabatic inflationary cosmological model. Our best fit model passes a series of physical consistency checks and agrees with essentially all currently available cosmological data. In addition to sharp constraints on the cosmic matter budget in good agreement with those of the BOOMERaNG, DASI and Maxima teams, we obtain a heaviest neutrino mass range 0.04-4.2 eV and the sharpest constraints to date on gravity waves which (together with preference for a slight red-tilt) favor 'small-field' inflation models
International Nuclear Information System (INIS)
Fliche, H.-H.; Souriau, J.-M.
1978-03-01
On the basis of colorimetric data a composite spectrum of quasars is established from the visible to the Lyman's limit. Its agreement with the spectrum of the quasar 3C273, obtained directly, confirms the homogeneity of these objects. The compatibility of the following hypotheses: negligible evolution of quasars, Friedmann type model of the universe with cosmological constant, is studied by means of two tests: a non-correlation test adopted to the observation conditions and the construction of diagrams (absolute magnitude, volume) using the K-correction deduced from the composite spectrum. This procedure happens to give relatively well-defined values of the parameters; the central values of the density parameter, the reduced curvature and the reduced cosmological constant are: Ω 0 =0.053, k 0 =0.245, lambda-zero=1.19, which correspond to a big bang model, eternally expanding, spatially finite, in which Hubble's parameter H is presently increasing. This model responds well to different cosmological tests: density of matter, diameter of radio sources, age of the universe. Its characteristics suggest various cosmogonic mechanisms, espacially mass formation by growth of empty spherical bubbles [fr
Cosmological dark matter and ensoulment
M. Kemal Irmak
2013-01-01
Allocortical structures such as hippocampal formation and amygdala are involved in the emotions and memory, and regarded as the seat of personhood. Human body is a composite of a biological organism and an intellective soul. It was suggested that cerebral allocortex is the main region harboring the soul and the beginning of a human person as an individual living organism is at the 13th week of development when an adult type allocortex is already formed. No experimental data can be suffici...
Nonsingular bouncing cosmologies in light of BICEP2
International Nuclear Information System (INIS)
Cai, Yi-Fu; Quintin, Jerome; Saridakis, Emmanuel N.; Wilson-Ewing, Edward
2014-01-01
We confront various nonsingular bouncing cosmologies with the recently released BICEP2 data and investigate the observational constraints on their parameter space. In particular, within the context of the effective field approach, we analyze the constraints on the matter bounce curvaton scenario with a light scalar field, and the new matter bounce cosmology model in which the universe successively experiences a period of matter contraction and an ekpyrotic phase. Additionally, we consider three nonsingular bouncing cosmologies obtained in the framework of modified gravity theories, namely the Hořava-Lifshitz bounce model, the f(T) bounce model, and loop quantum cosmology
Combination and interpretation of observables in Cosmology
Directory of Open Access Journals (Sweden)
Virey Jean-Marc
2010-04-01
Full Text Available The standard cosmological model has deep theoretical foundations but need the introduction of two major unknown components, dark matter and dark energy, to be in agreement with various observations. Dark matter describes a non-relativistic collisionless fluid of (non baryonic matter which amount to 25% of the total density of the universe. Dark energy is a new kind of fluid not of matter type, representing 70% of the total density which should explain the recent acceleration of the expansion of the universe. Alternatively, one can reject this idea of adding one or two new components but argue that the equations used to make the interpretation should be modified consmological scales. Instead of dark matter one can invoke a failure of Newton's laws. Instead of dark energy, two approaches are proposed : general relativity (in term of the Einstein equation should be modified, or the cosmological principle which fixes the metric used for cosmology should be abandonned. One of the main objective of the community is to find the path of the relevant interpretations thanks to the next generation of experiments which should provide large statistics of observationnal data. Unfortunately, cosmological in formations are difficult to pin down directly fromt he measurements, and it is mandatory to combine the various observables to get the cosmological parameters. This is not problematic from the statistical point of view, but assumptions and approximations made for the analysis may bias our interprettion of the data. Consequently, a strong attention should be paied to the statistical methods used to make parameters estimation and for model testing. After a review of the basics of cosmology where the cosmological parameters are introduced, we discuss the various cosmological probes and their associated observables used to extract cosmological informations. We present the results obtained from several statistical analyses combining data of diferent nature but
Constraints on small-scale cosmological fluctuations from SNe lensing dispersion
International Nuclear Information System (INIS)
Ben-Dayan, Ido; Takahashi, Ryuichi
2015-04-01
We provide predictions on small-scale cosmological density power spectrum from supernova lensing dispersion. Parameterizing the primordial power spectrum with running α and running of running β of the spectral index, we exclude large positive α and β parameters which induce too large lensing dispersions over current observational upper bound. We ran cosmological N-body simulations of collisionless dark matter particles to investigate non-linear evolution of the primordial power spectrum with positive running parameters. The initial small-scale enhancement of the power spectrum is largely erased when entering into the non-linear regime. For example, even if the linear power spectrum at k>10 hMpc -1 is enhanced by 1-2 orders of magnitude, the enhancement much decreases to a factor of 2-3 at late time (z≤1.5). Therefore, the lensing dispersion induced by the dark matter fluctuations weakly constrains the running parameters. When including baryon-cooling effects (which strongly enhance the small-scale clustering), the constraint is comparable or tighter than the PLANCK constraint, depending on the UV cut-off. Further investigations of the non-linear matter spectrum with baryonic processes is needed to reach a firm constraint.
Friedmann cosmology with a cosmological 'constant' in the scale covariant theory
International Nuclear Information System (INIS)
Beesham, A.
1986-01-01
Homogeneous isotropic cosmologies in the presence of a cosmological 'constant' are studied in the scale covariant theory. A class of solutions is obtained for kappa = 0 for models filled with dust, radiation or stiff matter. For kappa not= 0, solutions are presented for the radiation models. (author)
Complete elimination of nonlinear light-matter interactions with broadband ultrafast laser pulses
DEFF Research Database (Denmark)
Shu, Chuan-Cun; Dong, Daoyi; Petersen, Ian R.
2017-01-01
optical effects, however, the probability of pure single-photon absorption is usually very low, which is particularly pertinent in the case of strong ultrafast laser pulses with broad bandwidth. Here we demonstrate theoretically a counterintuitive coherent single-photon absorption scheme by eliminating...... nonlinear interactions of ultrafast laser pulses with quantum systems. That is, a completely linear response of the system with respect to the spectral energy density of the incident light at the transition frequency can be obtained for all transition probabilities between 0 and 100% in multilevel quantum...... systems. To that end, a multiobjective optimization algorithm is developed to find an optimal spectral phase of an ultrafast laser pulse, which is capable of eliminating all possible nonlinear optical responses while maximizing the probability of single-photon absorption between quantum states. This work...
A new nonlinear mean-field model of neutron star matter
Miyazaki, K
2005-01-01
A new relativistic mean-field model of neutron star matter is developed. It is a generalization of the Zimanyi-Moszkowski (ZM) model based on the constituent quark picture of baryons. The renormalized meson-hyperon coupling constants in medium are uniquely determined in contrast to the naive extention of ZM model and so the application of the model to high-density neutron star (NS) matter is possible. Our results of the particle composition and the mass-radius relation of NSs agree well with those obtained from the phenomenologically-determined realistic equation-of-state.
Cosmological dynamics of extended chameleons
International Nuclear Information System (INIS)
Tamanini, Nicola; Wright, Matthew
2016-01-01
We investigate the cosmological dynamics of the recently proposed extended chameleon models at both background and linear perturbation levels. Dynamical systems techniques are employed to fully characterize the evolution of the universe at the largest distances, while structure formation is analysed at sub-horizon scales within the quasi-static approximation. The late time dynamical transition from dark matter to dark energy domination can be well described by almost all extended chameleon models considered, with no deviations from ΛCDM results at both background and perturbation levels. The results obtained in this work confirm the cosmological viability of extended chameleons as alternative dark energy models.
Cosmological dynamics of extended chameleons
Energy Technology Data Exchange (ETDEWEB)
Tamanini, Nicola [Institut de Physique Théorique, CEA-Saclay, CNRS UMR 3681, Université Paris-Saclay, F-91191 Gif-sur-Yvette (France); Wright, Matthew, E-mail: nicola.tamanini@cea.fr, E-mail: matthew.wright.13@ucl.ac.uk [Department of Mathematics, University College London, Gower Street, London, WC1E 6BT (United Kingdom)
2016-04-01
We investigate the cosmological dynamics of the recently proposed extended chameleon models at both background and linear perturbation levels. Dynamical systems techniques are employed to fully characterize the evolution of the universe at the largest distances, while structure formation is analysed at sub-horizon scales within the quasi-static approximation. The late time dynamical transition from dark matter to dark energy domination can be well described by almost all extended chameleon models considered, with no deviations from ΛCDM results at both background and perturbation levels. The results obtained in this work confirm the cosmological viability of extended chameleons as alternative dark energy models.
Cosmological tests of modified gravity.
Koyama, Kazuya
2016-04-01
We review recent progress in the construction of modified gravity models as alternatives to dark energy as well as the development of cosmological tests of gravity. Einstein's theory of general relativity (GR) has been tested accurately within the local universe i.e. the Solar System, but this leaves the possibility open that it is not a good description of gravity at the largest scales in the Universe. This being said, the standard model of cosmology assumes GR on all scales. In 1998, astronomers made the surprising discovery that the expansion of the Universe is accelerating, not slowing down. This late-time acceleration of the Universe has become the most challenging problem in theoretical physics. Within the framework of GR, the acceleration would originate from an unknown dark energy. Alternatively, it could be that there is no dark energy and GR itself is in error on cosmological scales. In this review, we first give an overview of recent developments in modified gravity theories including f(R) gravity, braneworld gravity, Horndeski theory and massive/bigravity theory. We then focus on common properties these models share, such as screening mechanisms they use to evade the stringent Solar System tests. Once armed with a theoretical knowledge of modified gravity models, we move on to discuss how we can test modifications of gravity on cosmological scales. We present tests of gravity using linear cosmological perturbations and review the latest constraints on deviations from the standard [Formula: see text]CDM model. Since screening mechanisms leave distinct signatures in the non-linear structure formation, we also review novel astrophysical tests of gravity using clusters, dwarf galaxies and stars. The last decade has seen a number of new constraints placed on gravity from astrophysical to cosmological scales. Thanks to on-going and future surveys, cosmological tests of gravity will enjoy another, possibly even more, exciting ten years.
Brandenberger, Robert H.
2008-01-01
String gas cosmology is a string theory-based approach to early universe cosmology which is based on making use of robust features of string theory such as the existence of new states and new symmetries. A first goal of string gas cosmology is to understand how string theory can effect the earliest moments of cosmology before the effective field theory approach which underlies standard and inflationary cosmology becomes valid. String gas cosmology may also provide an alternative to the curren...
Partial rip scenario - a cosmology with a growing cosmological term
International Nuclear Information System (INIS)
Stefancic, H.
2004-01-01
A cosmology with the growing cosmological term is considered. If there is no exchange of energy between vacuum and matter components, the requirement of general covariance implies the time dependence of the gravitational constant G. Irrespectively of the exact functional form of the cosmological term growth, the universe ends in a de Sitter regime with a constant asymptotic Λ, but vanishing G. Although there is no divergence of the scale factor in finite time, such as in the 'Big Rip' scenario, gravitationally bound systems eventually become unbound. In the case of systems bound by non-gravitational forces, there is no unbounding effect, as the asymptotic Λ is insufficiently large to disturb these systems
Magnetohydrodynamic cosmologies
International Nuclear Information System (INIS)
Portugal, R.; Soares, I.D.
1991-01-01
We analyse a class of cosmological models in magnetohydrodynamic regime extending and completing the results of a previous paper. The material content of the models is a perfect fluid plus electromagnetic fields. The fluid is neutral in average but admits an electrical current which satisfies Ohm's law. All models fulfil the physical requirements of near equilibrium thermodynamics and can be favourably used as a more realistic description of the interior of a collapsing star in a magnetohydrodynamic regime with or without a magnetic field. (author)
Religion, theology and cosmology
Directory of Open Access Journals (Sweden)
John T. Fitzgerald
2013-10-01
Full Text Available Cosmology is one of the predominant research areas of the contemporary world. Advances in modern cosmology have prompted renewed interest in the intersections between religion, theology and cosmology. This article, which is intended as a brief introduction to the series of studies on theological cosmology in this journal, identifies three general areas of theological interest stemming from the modern scientific study of cosmology: contemporary theology and ethics; cosmology and world religions; and ancient cosmologies. These intersections raise important questions about the relationship of religion and cosmology, which has recently been addressed by William Scott Green and is the focus of the final portion of the article.
Quantum gravity and quantum cosmology
Papantonopoulos, Lefteris; Siopsis, George; Tsamis, Nikos
2013-01-01
Quantum gravity has developed into a fast-growing subject in physics and it is expected that probing the high-energy and high-curvature regimes of gravitating systems will shed some light on how to eventually achieve an ultraviolet complete quantum theory of gravity. Such a theory would provide the much needed information about fundamental problems of classical gravity, such as the initial big-bang singularity, the cosmological constant problem, Planck scale physics and the early-time inflationary evolution of our Universe. While in the first part of this book concepts of quantum gravity are introduced and approached from different angles, the second part discusses these theories in connection with cosmological models and observations, thereby exploring which types of signatures of modern and mathematically rigorous frameworks can be detected by experiments. The third and final part briefly reviews the observational status of dark matter and dark energy, and introduces alternative cosmological models. ...
Role of baryons in unified dark matter models
International Nuclear Information System (INIS)
Beca, L.M.G.; Avelino, P.P.; Carvalho, J.P. de M.; Martins, C.J.A.P.
2003-01-01
We discuss the importance of including baryons in analyses of unified dark matter scenarios, focusing on toy models involving a generalized Chaplygin gas. We determine observational constraints on this unified dark matter scenario coming from large-scale structure, type Ia supernovae and CMB data showing how this component can bring about a different behavior from the classical cold dark matter model with a cosmological constant and thus motivate further studies of this type of models. We also speculate on interesting new features which are likely to be important on nonlinear scales in this context
Advantage of nonlinear relativistic mean-field model in studying neutron star matter
Miyazaki, K
2006-01-01
We test the extended Zimanyi-Moszkowski model of relativistic nuclear matter for reproducing the density dependence of the symmetry energy, the direct URCA constraint M_{G}^{DU} \\geq 1.5M_{\\odot} on the gravitational mass of neutron star (NS), the large radii of NSs in RX J1856.5-3754 and qLMXB X7, the massive NSs in PSR J0751+1807 and 4U1700-37, and the baryonic mass of J0737-3039B. The two sets of NN\\rho coupling constant are considered. The first (EZM1) is the same as the Bonn A potential. The second (EZM2) is chosen so as to reproduce the symmetry energy E_s=32MeV of nuclear matter. The EZM1 can pass 6 tests among 7, while the EZM2 passes 5 tests. We can therefore conclude that the EZM model has unique and excellent features and is the most prospective one for studying the dense baryonic matter.
Minimal scalar-less matter-coupled supergravity
Energy Technology Data Exchange (ETDEWEB)
Dall' Agata, Gianguido, E-mail: dallagat@pd.infn.it [Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università di Padova, Via Marzolo 8, I-35131 Padova (Italy); INFN, Sezione di Padova, Via Marzolo 8, I-35131 Padova (Italy); Centre de Physique Théorique, École Polytechnique, CNRS, Université Paris-Saclay, F-91128 Palaiseau (France); Ferrara, Sergio [Theory Unit, Physics Department, CERN, CH-1211 Geneva 23 (Switzerland); INFN, Laboratori Nazionali di Frascati, Via Enrico Fermi 40, I-00044 Frascati (Italy); Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1547 (United States); Zwirner, Fabio [Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università di Padova, Via Marzolo 8, I-35131 Padova (Italy); INFN, Sezione di Padova, Via Marzolo 8, I-35131 Padova (Italy); Theory Unit, Physics Department, CERN, CH-1211 Geneva 23 (Switzerland)
2016-01-10
We build the minimal supergravity model where the nilpotent chiral goldstino superfield is coupled to a chiral matter superfield, realising a different non-linear representation through a mixed nilpotency constraint. The model describes the spontaneous breaking of local supersymmetry in the presence of a generically massive Majorana fermion, but in the absence of elementary scalars. The sign and the size of the cosmological constant, the spectrum and the four-fermion interactions are controlled by suitable parameters.
Minimal scalar-less matter-coupled supergravity
Dall'Agata, Gianguido; Zwirner, Fabio
2016-01-01
We build the minimal supergravity model where the nilpotent chiral goldstino superfield is coupled to a chiral matter superfield, realising a different non-linear representation through a mixed nilpotency constraint. The model describes the spontaneous breaking of local supersymmetry in the presence of a generically massive Majorana fermion, but in the absence of elementary scalars. The sign and the size of the cosmological constant, the spectrum and the four-fermion interactions are controlled by suitable parameters.
Growth and dissolution of spherical density enhancements in SCDEW cosmologies
Energy Technology Data Exchange (ETDEWEB)
Bonometto, Silvio A. [INAF, Trieste Observatory and Trieste University, Physics Dep., Astronomy Unit, Via Tiepolo 11, 34143 Trieste (Italy); Mainini, Roberto, E-mail: bonometto@oats.inaf.it, E-mail: roberto.mainini@mib.infn.it [Physics Department ' G. Occhialini' , Milano-Bicocca University, Piazza della Scienza 3, 20126 Milano (Italy)
2017-06-01
Strongly Coupled Dark Energy plus Warm dark matter (SCDEW) cosmologies are based on the finding of a conformally invariant (CI) attractor solution during the early radiative expansion, requiring then the stationary presence of ∼ 1 % of coupled-DM and DE, since inflationary reheating. In these models, coupled-DM fluctuations, even in the early radiative expansion, grow up to non-linearity, as shown in a previous associated paper. Such early non-linear stages are modelized here through the evolution of a top-hat density enhancement. As expected, its radius R increases up to a maximum and then starts to decrease. Virial balance is reached when the coupled-DM density contrast is just 25–26 and DM density enhancement is O(10 %) of total density. Moreover, we find that this is not an equilibrium configuration as, afterwards, coupling causes DM particle velocities to increase, so that the fluctuation gradually dissolves. We estimate the duration of the whole process, from horizon crossing to dissolution, and find z {sub horizon}/ z {sub erasing} ∼ 3 × 10{sup 4}. Therefore, only fluctuations entering the horizon at z ∼< 10{sup 9}–10{sup 10} are able to accrete WDM with mass ∼ 100 eV—as soon as it becomes non-relativistic—so avoiding full disruption. Accordingly, SCDEW cosmologies, whose WDM has mass ∼ 100 eV, can preserve primeval fluctuations down to stellar mass scale.
Averaging in spherically symmetric cosmology
International Nuclear Information System (INIS)
Coley, A. A.; Pelavas, N.
2007-01-01
The averaging problem in cosmology is of fundamental importance. When applied to study cosmological evolution, the theory of macroscopic gravity (MG) can be regarded as a long-distance modification of general relativity. In the MG approach to the averaging problem in cosmology, the Einstein field equations on cosmological scales are modified by appropriate gravitational correlation terms. We study the averaging problem within the class of spherically symmetric cosmological models. That is, we shall take the microscopic equations and effect the averaging procedure to determine the precise form of the correlation tensor in this case. In particular, by working in volume-preserving coordinates, we calculate the form of the correlation tensor under some reasonable assumptions on the form for the inhomogeneous gravitational field and matter distribution. We find that the correlation tensor in a Friedmann-Lemaitre-Robertson-Walker (FLRW) background must be of the form of a spatial curvature. Inhomogeneities and spatial averaging, through this spatial curvature correction term, can have a very significant dynamical effect on the dynamics of the Universe and cosmological observations; in particular, we discuss whether spatial averaging might lead to a more conservative explanation of the observed acceleration of the Universe (without the introduction of exotic dark matter fields). We also find that the correlation tensor for a non-FLRW background can be interpreted as the sum of a spatial curvature and an anisotropic fluid. This may lead to interesting effects of averaging on astrophysical scales. We also discuss the results of averaging an inhomogeneous Lemaitre-Tolman-Bondi solution as well as calculations of linear perturbations (that is, the backreaction) in an FLRW background, which support the main conclusions of the analysis
Particle accelerators test cosmological theory
International Nuclear Information System (INIS)
Schramm, D.N.; Steigman, G.
1988-01-01
Over the past decade two subfields of science, cosmology and elementary-particle physics, have become married in a symbiotic relationship that has produced a number of exciting offspring. These offspring are beginning to yield insights on the creation of spacetime and matter at epochs as early as 10 to the minus 43 to 10 to the minus 35 second after the birth of the universe in the primordial explosion known as the big bang. Important clues to the nature of the big bang itself may even come from a theory currently under development, known as the ultimate theory of everything (T.E.O.). A T.E.O. would describe all the interactions among the fundamental particles in a single bold stroke. Now that cosmology ahs begun to make predictions about elementary-particle physics, it has become conceivable that those cosmological predictions could be checked with carefully controlled accelerator experiments. It has taken more than 10 years for accelerators to reach the point where they can do the appropriate experiments, but the experiments are now in fact in progress. The preliminary results confirm the predictions of cosmology. The cosmological prediction the authors have been concerned with pertains to setting limits on the number of fundamental particles of matter. It appears that there are 12 fundamental particles, as well as their corresponding antiparticles. Six of the fundamental particles are quarks. The other six are leptons. The 12 particles are grouped in three families, each family consisting of four members. Cosmology suggests there must be a finite number of families and, further limits the possible range of to small values: only three or at most four families exist. 7 figs
Silk, Joseph
1994-01-01
In the first two of these lectures, I present the evidence for baryonic dark matter and describe possible forms that it may take. The final lecture discusses formation of baryonic dark matter, and sets the cosmological context.
International Nuclear Information System (INIS)
Copeland, Edmund J.; Padilla, Antonio; Saffin, Paul M.
2012-01-01
We have recently proposed a novel self tuning mechanism to alleviate the famous cosmological constant problem, based on the general scalar tensor theory proposed by Horndeski. The self-tuning model ends up consisting of four geometric terms in the action, with each term containing a free potential function of the scalar field; the four together being labeled as the Fab-Four. In this paper we begin the important task of deriving the cosmology associated with the Fab-Four Lagrangian. Performing a phase plane analysis of the system we are able to obtain a number of fixed points for the system, with some remarkable new solutions emerging from the trade-off between the various potentials. As well as obtaining inflationary solutions we also find conventional radiation/matter-like solutions, but in regimes where the energy density is dominated by a cosmological constant, and where we do not have any explicit forms of radiation or matter. Stability conditions for matter solutions are obtained and we show how it is possible for there to exist an extended period of 'matter domination' opening up the possibility that we can generate cosmological structures, and recover a consistent cosmology even in the presence of a large cosmological constant
International Nuclear Information System (INIS)
Cruz, Norman; Palma, Guillermo; Zambrano, David; Avelino, Arturo
2013-01-01
We explore a cosmological model composed by a dark matter fluid interacting with a dark energy fluid. The interaction term has the non-linear λρ m α ρ e β form, where ρ m and ρ e are the energy densities of the dark matter and dark energy, respectively. The parameters α and β are in principle not constrained to take any particular values, and were estimated from observations. We perform an analytical study of the evolution equations, finding the fixed points and their stability properties in order to characterize suitable physical regions in the phase space of the dark matter and dark energy densities. The constants (λ,α,β) as well as w m and w e of the EoS of dark matter and dark energy respectively, were estimated using the cosmological observations of the type Ia supernovae and the Hubble expansion rate H(z) data sets. We find that the best estimated values for the free parameters of the model correspond to a warm dark matter interacting with a phantom dark energy component, with a well goodness-of-fit to data. However, using the Bayesian Information Criterion (BIC) we find that this model is overcame by a warm dark matter – phantom dark energy model without interaction, as well as by the ΛCDM model. We find also a large dispersion on the best estimated values of the (λ,α,β) parameters, so even if we are not able to set strong constraints on their values, given the goodness-of-fit to data of the model, we find that a large variety of theirs values are well compatible with the observational data used
Relic gravitons and viscous cosmologies
International Nuclear Information System (INIS)
Cataldo, Mauricio; Mella, Patricio
2006-01-01
Previously it was shown that there exists a class of viscous cosmological models which violate the dominant energy condition for a limited amount of time after which they are smoothly connected to the ordinary radiation era (which preserves the dominant energy conditions). This violation of the dominant energy condition at an early cosmological epoch may influence the slopes of energy spectra of relic gravitons that might be of experimental relevance. However, the bulk viscosity coefficient of these cosmologies became negative during the ordinary radiation era, and then the entropy of the sources driving the geometry decreases with time. We show that in the presence of viscous sources with a linear barotropic equation of state p=γρ we get viscous cosmological models with positive bulk viscous stress during all their evolution, and hence the matter entropy increases with the expansion time. In other words, in the framework of viscous cosmologies, there exist isotropic models compatible with the standard second law of thermodynamics which also may influence the slopes of energy spectra of relic gravitons
Cosmic curvature from de Sitter equilibrium cosmology.
Albrecht, Andreas
2011-10-07
I show that the de Sitter equilibrium cosmology generically predicts observable levels of curvature in the Universe today. The predicted value of the curvature, Ω(k), depends only on the ratio of the density of nonrelativistic matter to cosmological constant density ρ(m)(0)/ρ(Λ) and the value of the curvature from the initial bubble that starts the inflation, Ω(k)(B). The result is independent of the scale of inflation, the shape of the potential during inflation, and many other details of the cosmology. Future cosmological measurements of ρ(m)(0)/ρ(Λ) and Ω(k) will open up a window on the very beginning of our Universe and offer an opportunity to support or falsify the de Sitter equilibrium cosmology.
FAST-PT: a novel algorithm to calculate convolution integrals in cosmological perturbation theory
Energy Technology Data Exchange (ETDEWEB)
McEwen, Joseph E.; Fang, Xiao; Hirata, Christopher M.; Blazek, Jonathan A., E-mail: mcewen.24@osu.edu, E-mail: fang.307@osu.edu, E-mail: hirata.10@osu.edu, E-mail: blazek@berkeley.edu [Center for Cosmology and AstroParticle Physics, Department of Physics, The Ohio State University, 191 W Woodruff Ave, Columbus OH 43210 (United States)
2016-09-01
We present a novel algorithm, FAST-PT, for performing convolution or mode-coupling integrals that appear in nonlinear cosmological perturbation theory. The algorithm uses several properties of gravitational structure formation—the locality of the dark matter equations and the scale invariance of the problem—as well as Fast Fourier Transforms to describe the input power spectrum as a superposition of power laws. This yields extremely fast performance, enabling mode-coupling integral computations fast enough to embed in Monte Carlo Markov Chain parameter estimation. We describe the algorithm and demonstrate its application to calculating nonlinear corrections to the matter power spectrum, including one-loop standard perturbation theory and the renormalization group approach. We also describe our public code (in Python) to implement this algorithm. The code, along with a user manual and example implementations, is available at https://github.com/JoeMcEwen/FAST-PT.
MassiveNuS: cosmological massive neutrino simulations
Liu, Jia; Bird, Simeon; Zorrilla Matilla, José Manuel; Hill, J. Colin; Haiman, Zoltán; Madhavacheril, Mathew S.; Petri, Andrea; Spergel, David N.
2018-03-01
The non-zero mass of neutrinos suppresses the growth of cosmic structure on small scales. Since the level of suppression depends on the sum of the masses of the three active neutrino species, the evolution of large-scale structure is a promising tool to constrain the total mass of neutrinos and possibly shed light on the mass hierarchy. In this work, we investigate these effects via a large suite of N-body simulations that include massive neutrinos using an analytic linear-response approximation: the Cosmological Massive Neutrino Simulations (MassiveNuS). The simulations include the effects of radiation on the background expansion, as well as the clustering of neutrinos in response to the nonlinear dark matter evolution. We allow three cosmological parameters to vary: the neutrino mass sum Mν in the range of 0–0.6 eV, the total matter density Ωm, and the primordial power spectrum amplitude As. The rms density fluctuation in spheres of 8 comoving Mpc/h (σ8) is a derived parameter as a result. Our data products include N-body snapshots, halo catalogues, merger trees, ray-traced galaxy lensing convergence maps for four source redshift planes between zs=1–2.5, and ray-traced cosmic microwave background lensing convergence maps. We describe the simulation procedures and code validation in this paper. The data are publicly available at http://columbialensing.org.
Krioukov, Dmitri; Kitsak, Maksim; Sinkovits, Robert S; Rideout, David; Meyer, David; Boguñá, Marián
2012-01-01
Prediction and control of the dynamics of complex networks is a central problem in network science. Structural and dynamical similarities of different real networks suggest that some universal laws might accurately describe the dynamics of these networks, albeit the nature and common origin of such laws remain elusive. Here we show that the causal network representing the large-scale structure of spacetime in our accelerating universe is a power-law graph with strong clustering, similar to many complex networks such as the Internet, social, or biological networks. We prove that this structural similarity is a consequence of the asymptotic equivalence between the large-scale growth dynamics of complex networks and causal networks. This equivalence suggests that unexpectedly similar laws govern the dynamics of complex networks and spacetime in the universe, with implications to network science and cosmology.
Vacuum solutions of Bianchi cosmologies in quadratic gravity
International Nuclear Information System (INIS)
Deus, Juliano Alves de; Muller, Daniel
2011-01-01
Full text: In this work we solve numerically the vacuum solutions of field equations of Bianchi homogeneous universes in the context of Semiclassical theory. Our interest is to study the quadratic theory of gravity with regard in the cosmological description of our universe in periods of intense fields. Bianchi cosmologies are anisotropic homogeneous cosmological models, but can include the isotropic models as particular cases (Bianchi I, VII and IX include homogeneous and isotropic Friedmann models plane, hyperbolic and spherical, respectively). Homogeneous models are good cosmological representations of our universe. With focus in solutions for intense fields, like the early universe, where isotropy is not necessarily required, the adopted scenario is the vacuum solutions, where the geometry is dominant in determining the gravitation. Still following in this way, the Semiclassical theory, which considers quantum matter fields propagating in classical geometrical background, is addressed to give the field equations. This formalism leads to fourth-order ordinary differential equations, in contrast to second-order equations from General Relativity. The Lagrangian of the theory is quadratic in the Ricci scalar and in the Ricci tensor. The equations system is highly non-linear and can be only numerically solved, except perhaps for few particular cases. We obtained numerical solutions for Bianchi V II A evolving to Minkowski and to de Sitter solutions, and also to singularities. The both first and second solutions were obtained choosing initial conditions near from respective exact vacuum solutions from Einstein theory, which are also exact solutions of the quadratic theory. Other Bianchi types are still under study. (author)
Narlikar, Jayant Vishnu
2002-01-01
The third edition of this successful textbook is fully updated and includes important recent developments in cosmology. It begins with an introduction to cosmology and general relativity, and goes on to cover the mathematical models of standard cosmology. The physical aspects of cosmology, including primordial nucleosynthesis, the astroparticle physics of inflation, and the current ideas on structure formation are discussed. Alternative models of cosmology are reviewed, including the model of Quasi-Steady State Cosmology, which has recently been proposed as an alternative to Big Bang Cosmology.
Cosmological and supernova neutrinos
Kajino, T.; Aoki, W.; Balantekin, A. B.; Cheoun, M.-K.; Hayakawa, T.; Hidaka, J.; Hirai, Y.; Kusakabe, M.; Mathews, G. J.; Nakamura, K.; Pehlivan, Y.; Shibagaki, S.; Suzuki, T.
2014-06-01
The Big Bang nucleosynthesis (BBN) and the cosmic microwave background (CMB) anisotropies are the pillars of modern cosmology. It has recently been suggested that axion which is a dark matter candidate in the framework of the standard model could condensate in the early universe and induce photon cooling before the epoch of the photon last scattering. Although this may render a solution to the overproduction problem of primordial 7Li abundance, there arises another serious difficulty of overproducing D abundance. We propose a hybrid dark matter model with both axions and relic supersymmetric (SUSY) particles to solve both overproduction problems of the primordial D and 7Li abundances simultaneously. The BBN also serves to constrain the nature of neutrinos. Considering non-thermal photons produced in the decay of the heavy sterile neutrinos due to the magnetic moment, we explore the cosmological constraint on the strength of neutrino magnetic moment consistent with the observed light element abundances. Core-collapse supernovae eject huge flux of energetic neutrinos which affect explosive nucleosynthesis of rare isotopes like 7Li, 11B, 92Nb, 138La and 180Ta and r-process elements. Several isotopes depend strongly on the neutrino flavor oscillation due to the Mikheyev-Smirnov-Wolfenstein (MSW) effect. Combining the recent experimental constraints on θ13 with predicted and observed supernova-produced abundance ratio 11B/7Li encapsulated in the presolar grains from the Murchison meteorite, we show a marginal preference for an inverted neutrino mass hierarchy. We also discuss supernova relic neutrinos (SRN) that may indicate the softness of the equation of state (EoS) of nuclear matter and adiabatic conditions of the neutrino oscillation.
Cosmological and supernova neutrinos
Energy Technology Data Exchange (ETDEWEB)
Kajino, T. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan Department of Astronomy, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033 (Japan); Aoki, W. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Balantekin, A. B. [Department of Physics, University of Wisconsin - Madison, Wisconsin 53706 (United States); Cheoun, M.-K. [Department of Physics, Soongsil University, Seoul 156-743 (Korea, Republic of); Hayakawa, T. [Japan Atomic Energy Agency, Shirakara-Shirane 2-4, Tokai-mura, Ibaraki 319-1195 (Japan); Hidaka, J. [National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Hirai, Y.; Shibagaki, S. [National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan and Department of Astronomy, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033 (Japan); Kusakabe, M. [School of Liberal Arts and Science, Korea Aerospace University, Goyang 412-791 (Korea, Republic of); Mathews, G. J. [Department of Physics, University of Notre Dame, IN 46556 (United States); Nakamura, K. [Waseda University, Ohkubo 3-4-1, Shinjuku, Tokyo 169-8555 (Japan); Pehlivan, Y. [Mimar Sinan GSÜ, Department of Physics, Şişli, İstanbul 34380 (Turkey); Suzuki, T. [Nihon University, Sakurajosui 3-25-40, Setagaya-ku, Tokyo 156-8550 (Japan)
2014-06-24
The Big Bang nucleosynthesis (BBN) and the cosmic microwave background (CMB) anisotropies are the pillars of modern cosmology. It has recently been suggested that axion which is a dark matter candidate in the framework of the standard model could condensate in the early universe and induce photon cooling before the epoch of the photon last scattering. Although this may render a solution to the overproduction problem of primordial {sup 7}Li abundance, there arises another serious difficulty of overproducing D abundance. We propose a hybrid dark matter model with both axions and relic supersymmetric (SUSY) particles to solve both overproduction problems of the primordial D and {sup 7}Li abundances simultaneously. The BBN also serves to constrain the nature of neutrinos. Considering non-thermal photons produced in the decay of the heavy sterile neutrinos due to the magnetic moment, we explore the cosmological constraint on the strength of neutrino magnetic moment consistent with the observed light element abundances. Core-collapse supernovae eject huge flux of energetic neutrinos which affect explosive nucleosynthesis of rare isotopes like {sup 7}Li, {sup 11}B, {sup 92}Nb, {sup 138}La and {sup 180}Ta and r-process elements. Several isotopes depend strongly on the neutrino flavor oscillation due to the Mikheyev-Smirnov-Wolfenstein (MSW) effect. Combining the recent experimental constraints on θ{sub 13} with predicted and observed supernova-produced abundance ratio {sup 11}B/{sup 7}Li encapsulated in the presolar grains from the Murchison meteorite, we show a marginal preference for an inverted neutrino mass hierarchy. We also discuss supernova relic neutrinos (SRN) that may indicate the softness of the equation of state (EoS) of nuclear matter and adiabatic conditions of the neutrino oscillation.
Cosmological observables in the quasi-spherical Szekeres model
Buckley, Robert G.
2014-10-01
The standard model of cosmology presents a homogeneous universe, and we interpret cosmological data through this framework. However, structure growth creates nonlinear inhomogeneities that may affect observations, and even larger structures may be hidden by our limited vantage point and small number of independent observations. As we determine the universe's parameters with increasing precision, the accuracy is contingent on our understanding of the effects of such structures. For instance, giant void models can explain some observations without dark energy. Because perturbation theory cannot adequately describe nonlinear inhomogeneities, exact solutions to the equations of general relativity are important for these questions. The most general known solution capable of describing inhomogeneous matter distributions is the Szekeres class of models. In this work, we study the quasi-spherical subclass of these models, using numerical simulations to calculate the inhomogeneities' effects on observations. We calculate the large-angle CMB in giant void models and compare with simpler, symmetric void models that have previously been found inadequate to matchobservations. We extend this by considering models with early-time inhomogeneities as well. Then, we study distance observations, including selection effects, in models which are homogeneous on scales around 100 Mpc---consistent with standard cosmology---but inhomogeneous on smaller scales. Finally, we consider photon polarizations, and show that they are not directly affected by inhomogeneities. Overall, we find that while Szekeres models have some advantages over simpler models, they are still seriously limited in their ability to alter our parameter estimation while remaining within the bounds of current observations.
Cosmology understanding the evolution of the universe
2015-01-01
Bridging astronomy and physics, cosmology seeks to examine the nature of the universe as a whole. Scientific investigation of cosmology began in ancient times and progressed rapidly after the Scientific Revolution, which produced the discovery of gravity and the heliocentric model of Copernicus. This volume examines the historical developments in the field of cosmology, the evidence supporting the Big Bang theory, and the future implications of dark matter and an expanding universe. Readers will also be introduced to the various thinkers who helped advance study of this endlessly fascinating f
Fourier imaging of non-linear structure formation
International Nuclear Information System (INIS)
Brandbyge, Jacob; Hannestad, Steen
2017-01-01
We perform a Fourier space decomposition of the dynamics of non-linear cosmological structure formation in ΛCDM models. From N -body simulations involving only cold dark matter we calculate 3-dimensional non-linear density, velocity divergence and vorticity Fourier realizations, and use these to calculate the fully non-linear mode coupling integrals in the corresponding fluid equations. Our approach allows for a reconstruction of the amount of mode coupling between any two wavenumbers as a function of redshift. With our Fourier decomposition method we identify the transfer of power from larger to smaller scales, the stable clustering regime, the scale where vorticity becomes important, and the suppression of the non-linear divergence power spectrum as compared to linear theory. Our results can be used to improve and calibrate semi-analytical structure formation models.
Fourier imaging of non-linear structure formation
Energy Technology Data Exchange (ETDEWEB)
Brandbyge, Jacob; Hannestad, Steen, E-mail: jacobb@phys.au.dk, E-mail: sth@phys.au.dk [Department of Physics and Astronomy, University of Aarhus, Ny Munkegade 120, DK-8000 Aarhus C (Denmark)
2017-04-01
We perform a Fourier space decomposition of the dynamics of non-linear cosmological structure formation in ΛCDM models. From N -body simulations involving only cold dark matter we calculate 3-dimensional non-linear density, velocity divergence and vorticity Fourier realizations, and use these to calculate the fully non-linear mode coupling integrals in the corresponding fluid equations. Our approach allows for a reconstruction of the amount of mode coupling between any two wavenumbers as a function of redshift. With our Fourier decomposition method we identify the transfer of power from larger to smaller scales, the stable clustering regime, the scale where vorticity becomes important, and the suppression of the non-linear divergence power spectrum as compared to linear theory. Our results can be used to improve and calibrate semi-analytical structure formation models.
Emergence of complex space-temporal order in nonlinear field theories
International Nuclear Information System (INIS)
Gleiser, Marcelo
2006-01-01
We investigate the emergence of time-dependent nonperturbative configurations during the evolution of nonlinear scalar field models with symmetric and asymmetric double-well potentials. Complex space-temporal behavior emerges as the system seeks to establish equipartition after a fast quench. We show that fast quenches may dramatically modify the decay rate of metastable states in first order phase transitions. We discuss possible applications in condensed matter systems and in inflationary cosmology. (author)
Emergence of Complex Spatio-Temporal Behavior in Nonlinear Field Theories
International Nuclear Information System (INIS)
Gleiser, Marcelo; Howell, Rafael C.
2006-01-01
We investigate the emergence of time-dependent nonperturbative configurations during the evolution of nonlinear scalar field models with symmetric and asymmetric double-well potentials. Complex spatio-temporal behavior emerges as the system seeks to establish equipartition after a fast quench. We show that fast quenches may dramatically modify the decay rate of metastable states in first order phase transitions. We discuss possible applications in condensed matter systems and early universe cosmology
International Nuclear Information System (INIS)
Lachieze-Rey, Marc
2005-01-01
After having recalled that the Platonist and Aristotelian views were the basis of cosmology during the Antiquity and the Middle-Age, the author indicates that these views have been put into question again by Copernicus, Giordano Bruno, Kepler, Galileo and others whose works resulted in Newton physics. The author then follows and comments this history with the emergence of contemporary physics (relativistic and quantum physics) and new concepts for matter, space and time, light, energy, and the Universe with a relativistic cosmology. After having commented these last issues, the author evokes how new results confirmed big-bang models. He also outlines problems to be solved or addressed: observations related to the hidden mass, issue of unification, technological issues to obtain information about what went on more than 13 billions years ago. The author comments the issue of other universes, and issues regarding science, metaphysics and religion raised by these theoretical developments. He also comments the emergence of new physics (supersymmetry, quantum gravity)
Green, Dan
2016-01-01
This volume makes explicit use of the synergy between cosmology and high energy physics, for example, supersymmetry and dark matter, or nucleosynthesis and the baryon-to-photon ratio. In particular the exciting possible connection between the recently discovered Higgs scalar and the scalar field responsible for inflation is explored.The recent great advances in the accuracy of the basic cosmological parameters is exploited in that no free scale parameters such as h appear, rather the basic calculations are done numerically using all sources of energy density simultaneously. Scripts are provided that allow the reader to calculate exact results for the basic parameters. Throughout MATLAB tools such as symbolic math, numerical solutions, plots and 'movies' of the dynamical evolution of systems are used. The GUI package is also shown as an example of the real time manipulation of parameters which is available to the reader.All the MATLAB scripts are made available to the reader to explore examples of the uses of ...
Nonlinear Dynamics of the Cosmic Neutrino Background
Inman, Derek
At least two of the three neutrino species are known to be massive, but their exact masses are currently unknown. Cosmic neutrinos decoupled from the rest of the primordial plasma early on when the Universe was over a billion times hotter than it is today. These relic particles, which have cooled and are now non-relativistic, constitute the Cosmic Neutrino Background and permeate the Universe. While they are not observable directly, their presence can be inferred by measuring the suppression of the matter power spectrum. This suppression is a linear effect caused by the large thermal velocities of neutrinos, which prevent them from collapsing gravitationally on small scales. Unfortunately, it is difficult to measure because of degeneracies with other cosmological parameters and biases arising from the fact that we typically observe point-like galaxies rather than a continous matter field. It is therefore important to look for new effects beyond linear suppression that may be more sensitive to neutrinos. This thesis contributes to the understanding of the nonlinear dynamics of the cosmological neutrino background in the following ways: (i) the development of a new injection scheme for neutrinos in cosmological N-body simulations which circumvents many issues associated with simulating neutrinos at large redshifts, (ii) the numerical study of the relative velocity field between cold dark matter and neutrinos including its reconstruction from density fields, (iii) the theoretical description of neutrinos as a dispersive fluid and its use in modelling the nonlinear evolution of the neutrino density power spectrum, (iv) the derivation of the dipole correlation function using linear response which allows for the Fermi-Dirac velocity distribution to be properly included, and (v) the numerical study and detection of the dipole correlation function in the TianNu simulation. In totality, this thesis is a comprehensive study of neutrino density and velocity fields that may
Cosmological models in energy-momentum-squared gravity
Board, Charles V. R.; Barrow, John D.
2017-12-01
We study the cosmological effects of adding terms of higher order in the usual energy-momentum tensor to the matter Lagrangian of general relativity. This is in contrast to most studies of higher-order gravity which focus on generalizing the Einstein-Hilbert curvature contribution to the Lagrangian. The resulting cosmological theories give rise to field equations of similar form to several particular theories with different fundamental bases, including bulk viscous cosmology, loop quantum gravity, k -essence, and brane-world cosmologies. We find a range of exact solutions for isotropic universes, discuss their behaviors with reference to the early- and late-time evolution, accelerated expansion, and the occurrence or avoidance of singularities. We briefly discuss extensions to anisotropic cosmologies and delineate the situations where the higher-order matter terms will dominate over anisotropies on approach to cosmological singularities.
Energy Technology Data Exchange (ETDEWEB)
Goernitz, T. [Inst. fuer Didaktik der Physik, J.W.Goethe-Univ., Frankfurt/Main (Germany)
2007-07-01
It is common sense between physicists that in the beginning the cosmos is in a narrow relationship to quantum phenomena. Because of the universal validity of quantum theory this relation remains significant in the whole cosmic evolution. Whereas a classical approach is sufficient for the description of many phenomena it is no more useful at last for the case of the ground state of a system. This holds also for the cosmos. The black holes are that part of physics where quantum theory and gravitational theory come into close contact. There a Gedankenexperiment becomes possible that clarifies the fundamental role of abstract quantum information. We give it a new name (Protyposis) because it must be imagined without emitter, receiver and moreover without any concrete meaning. This meaning-free abstract quantum information is defined by means of black holes and cosmology. Protyposis enables a new conception for ''matter'' and makes possible to overcome the problems of the ''Lego-world-view'', which result from the attempt to find the ''simple and therefore basic concepts'' in the range of spatial smallness. Matter can be understood now as ''formed and condensed quantum information''. But on a first view it is nothing to see from its character of being information, as like matter does not appear as ''pure motion'', what it is also because of E=mc{sup 2}. (orig.)
BMSSM implications for cosmology
International Nuclear Information System (INIS)
Bernal, Nicolas; Blum, Kfir; Nir, Yosef; Losada, Marta
2009-01-01
The addition of non-renormalizable terms involving the Higgs fields to the MSSM (BMSSM) ameliorates the little hierarchy problem of the MSSM. We analyze in detail the two main cosmological issues affected by the BMSSM: dark matter and baryogenesis. The regions for which the relic abundance of the LSP is consistent with WMAP and collider constraints are identified, showing that the bulk region and other previously excluded regions are now permitted. Requiring vacuum stability limits the allowed regions. Based on a two-loop finite temperature effective potential analysis, we show that the electroweak phase transition can be sufficiently first order in regions that for the MSSM are incompatible with the LEP Higgs mass bound, including parameter values of tan β∼ t -tilde 1 >m t , m Q < < TeV.
Cosmological disformal invariance
Energy Technology Data Exchange (ETDEWEB)
Domènech, Guillem; Sasaki, Misao [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan); Naruko, Atsushi, E-mail: guillem.domenech@yukawa.kyoto-u.ac.jp, E-mail: naruko@th.phys.titech.ac.jp, E-mail: misao@yukawa.kyoto-u.ac.jp [Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)
2015-10-01
The invariance of physical observables under disformal transformations is considered. It is known that conformal transformations leave physical observables invariant. However, whether it is true for disformal transformations is still an open question. In this paper, it is shown that a pure disformal transformation without any conformal factor is equivalent to rescaling the time coordinate. Since this rescaling applies equally to all the physical quantities, physics must be invariant under a disformal transformation, that is, neither causal structure, propagation speed nor any other property of the fields are affected by a disformal transformation itself. This fact is presented at the action level for gravitational and matter fields and it is illustrated with some examples of observable quantities. We also find the physical invariance for cosmological perturbations at linear and high orders in perturbation, extending previous studies. Finally, a comparison with Horndeski and beyond Horndeski theories under a disformal transformation is made.
LHC, Astrophysics and Cosmology
Directory of Open Access Journals (Sweden)
Giulio Auriemma
2014-12-01
Full Text Available In this paper we discuss the impact on cosmology of recent results obtained by the LHC (Large Hadron Collider experiments in the 2011-2012 runs, respectively at √s = 7 and 8 TeV. The capital achievement of LHC in this period has been the discovery of a spin-0 particle with mass 126 GeV/c2, very similar to the Higgs boson of the Standard Model of Particle Physics. Less exciting, but not less important, negative results of searches for Supersymmetric particles or other exotica in direct production or rare decays are discussed in connection with particles and V.H.E. astronomy searches for Dark Matter.
International Nuclear Information System (INIS)
Tayler, R.J.
1983-01-01
The standard model of the hot big bang cosmological theory, which appears to be in agreement, at least qualitatively, with the observed properties of the Universe, assumes that the early Universe was homogeneous and isotropic and that it has been continuously expanding from a state characterized by very high temperature and density, where matter and radiation were to a good approximation in a state of thermodynamic equilibrium. In this standard model, it is assumed that baryon number, charge number and the various lepton numbers are all conserved. Only the baryon number is non-zero and this, expressed as the ratio of the net number of baryons (baryons minus antibaryons) to the number of photons per unit volume is the undefined parameter in the model. The author discusses the importance of knowing how many types of neutrinos there are with regard to the He 4 abundance, and the implication of a small, non-zero neutrino mass. (Auth.)
White, S
1994-01-01
Galaxy clusters are the largest coherent objects in Universe. It has been known since 1933 that their dynamical properties require either a modification of the theory of gravity, or the presence of a dominant component of unseen material of unknown nature. Clusters still provide the best laboratories for studying the amount and distribution of this dark matter relative to the material which can be observed directly -- the galaxies themselves and the hot,X-ray-emitting gas which lies between them.Imaging and spectroscopy of clusters by satellite-borne X -ray telescopes has greatly improved our knowledge of the structure and composition of this intergalactic medium. The results permit a number of new approaches to some fundamental cosmological questions,but current indications from the data are contradictory. The observed irregularity of real clusters seems to imply recent formation epochs which would require a universe with approximately the critical density. On the other hand, the large baryon fraction observ...
A cosmological model with particle creation
International Nuclear Information System (INIS)
Chatterjee, Sujit
2001-01-01
A higher dimensional cosmological model is proposed where an expanding universe evolves from the vacuum fluctuation and matter creation takes place out of the gravitational energy. Choosing a particular form of the matter creation function N(t) as an initial conditions it can be shown that starting from an inflationary era the cosmos enters the higher dimensional Friedmann-like phase after a time scale when the matter creation stops
Cosmological forecasts from photometric measurements of the angular correlation function
International Nuclear Information System (INIS)
Sobreira, F.; Rosenfeld, R.; Simoni, F. de; Costa, L. A. N. da; Maia, M. A. G.; Makler, M.
2011-01-01
We study forecasts for the accuracy of the determination of cosmological parameters from future large-scale photometric surveys obtained using the full shape of the 2-point galaxy angular correlation function. The effects of linear redshift-space distortion, photometric redshift Gaussian errors, galaxy bias and nonlinearities in the power spectrum are included on our analysis. The Fisher information matrix is constructed with the full covariance matrix, including the correlation between nearby redshift shells arising from the photometric redshift error. We show that under some reasonable assumptions, a survey such as the imminent Dark Energy Survey should be able to constrain the dark energy equation of state parameter w and the cold dark matter density Ω cdm with a precision of the order of 20% and 13%, respectively, from the full shape of the angular correlation function alone. When combined with priors from other observations the precision in the determination of these parameters improve to 8% and 4%, respectively.
CHAM: a fast algorithm of modelling non-linear matter power spectrum in the sCreened HAlo Model
Hu, Bin; Liu, Xue-Wen; Cai, Rong-Gen
2018-05-01
We present a fast numerical screened halo model algorithm (CHAM, which stands for the sCreened HAlo Model) for modelling non-linear power spectrum for the alternative models to Λ cold dark matter. This method has three obvious advantages. First of all, it is not being restricted to a specific dark energy/modified gravity model. In principle, all of the screened scalar-tensor theories can be applied. Secondly, the least assumptions are made in the calculation. Hence, the physical picture is very easily understandable. Thirdly, it is very predictable and does not rely on the calibration from N-body simulation. As an example, we show the case of the Hu-Sawicki f(R) gravity. In this case, the typical CPU time with the current parallel PYTHON script (eight threads) is roughly within 10 min. The resulting spectra are in a good agreement with N-body data within a few percentage accuracy up to k ˜ 1 h Mpc-1.
Cosmological perturbations beyond linear order
CERN. Geneva
2013-01-01
Cosmological perturbation theory is the standard tool to understand the formation of the large scale structure in the Universe. However, its degree of applicability is limited by the growth of the amplitude of the matter perturbations with time. This problem can be tackled with by using N-body simulations or analytical techniques that go beyond the linear calculation. In my talk, I'll summarise some recent efforts in the latter that ameliorate the bad convergence of the standard perturbative expansion. The new techniques allow better analytical control on observables (as the matter power spectrum) over scales very relevant to understand the expansion history and formation of structure in the Universe.
Dimensional cosmological principles
International Nuclear Information System (INIS)
Chi, L.K.
1985-01-01
The dimensional cosmological principles proposed by Wesson require that the density, pressure, and mass of cosmological models be functions of the dimensionless variables which are themselves combinations of the gravitational constant, the speed of light, and the spacetime coordinates. The space coordinate is not the comoving coordinate. In this paper, the dimensional cosmological principle and the dimensional perfect cosmological principle are reformulated by using the comoving coordinate. The dimensional perfect cosmological principle is further modified to allow the possibility that mass creation may occur. Self-similar spacetimes are found to be models obeying the new dimensional cosmological principle
Palmero, Faustino; Lemos, M; Sánchez-Rey, Bernardo; Casado-Pascual, Jesús
2018-01-01
This book presents an overview of the most recent advances in nonlinear science. It provides a unified view of nonlinear properties in many different systems and highlights many new developments. While volume 1 concentrates on mathematical theory and computational techniques and challenges, which are essential for the study of nonlinear science, this second volume deals with nonlinear excitations in several fields. These excitations can be localized and transport energy and matter in the form of breathers, solitons, kinks or quodons with very different characteristics, which are discussed in the book. They can also transport electric charge, in which case they are known as polarobreathers or solectrons. Nonlinear excitations can influence function and structure in biology, as for example, protein folding. In crystals and other condensed matter, they can modify transport properties, reaction kinetics and interact with defects. There are also engineering applications in electric lattices, Josephson junction a...
Fitting and forecasting coupled dark energy in the non-linear regime
Energy Technology Data Exchange (ETDEWEB)
Casas, Santiago; Amendola, Luca; Pettorino, Valeria; Vollmer, Adrian [Institut für Theoretische Physik, Ruprecht-Karls-Universität Heidelberg, Philosophenweg 16, Heidelberg, 69120 Germany (Germany); Baldi, Marco, E-mail: casas@thphys.uni-heidelberg.de, E-mail: l.amendola@thphys.uni-heidelberg.de, E-mail: mail@marcobaldi.it, E-mail: v.pettorino@thphys.uni-heidelberg.de, E-mail: vollmer@thphys.uni-heidelberg.de [Dipartimento di Fisica e Astronomia, Alma Mater Studiorum Università di Bologna, viale Berti Pichat, 6/2, Bologna, I-40127 Italy (Italy)
2016-01-01
We consider cosmological models in which dark matter feels a fifth force mediated by the dark energy scalar field, also known as coupled dark energy. Our interest resides in estimating forecasts for future surveys like Euclid when we take into account non-linear effects, relying on new fitting functions that reproduce the non-linear matter power spectrum obtained from N-body simulations. We obtain fitting functions for models in which the dark matter-dark energy coupling is constant. Their validity is demonstrated for all available simulations in the redshift range 0z=–1.6 and wave modes below 0k=1 h/Mpc. These fitting formulas can be used to test the predictions of the model in the non-linear regime without the need for additional computing-intensive N-body simulations. We then use these fitting functions to perform forecasts on the constraining power that future galaxy-redshift surveys like Euclid will have on the coupling parameter, using the Fisher matrix method for galaxy clustering (GC) and weak lensing (WL). We find that by using information in the non-linear power spectrum, and combining the GC and WL probes, we can constrain the dark matter-dark energy coupling constant squared, β{sup 2}, with precision smaller than 4% and all other cosmological parameters better than 1%, which is a considerable improvement of more than an order of magnitude compared to corresponding linear power spectrum forecasts with the same survey specifications.
Fitting and forecasting coupled dark energy in the non-linear regime
International Nuclear Information System (INIS)
Casas, Santiago; Amendola, Luca; Pettorino, Valeria; Vollmer, Adrian; Baldi, Marco
2016-01-01
We consider cosmological models in which dark matter feels a fifth force mediated by the dark energy scalar field, also known as coupled dark energy. Our interest resides in estimating forecasts for future surveys like Euclid when we take into account non-linear effects, relying on new fitting functions that reproduce the non-linear matter power spectrum obtained from N-body simulations. We obtain fitting functions for models in which the dark matter-dark energy coupling is constant. Their validity is demonstrated for all available simulations in the redshift range 0z=–1.6 and wave modes below 0k=1 h/Mpc. These fitting formulas can be used to test the predictions of the model in the non-linear regime without the need for additional computing-intensive N-body simulations. We then use these fitting functions to perform forecasts on the constraining power that future galaxy-redshift surveys like Euclid will have on the coupling parameter, using the Fisher matrix method for galaxy clustering (GC) and weak lensing (WL). We find that by using information in the non-linear power spectrum, and combining the GC and WL probes, we can constrain the dark matter-dark energy coupling constant squared, β 2 , with precision smaller than 4% and all other cosmological parameters better than 1%, which is a considerable improvement of more than an order of magnitude compared to corresponding linear power spectrum forecasts with the same survey specifications
Directory of Open Access Journals (Sweden)
Gennadii Aliaiev
2018-02-01
Full Text Available The paper focuses on cosmological ideas of a twentieth-century Russian philosopher Nikolay Lossky (1870-1965. It specifies the place of these ideas within the entire framework of his philosophical views, as well as in the context of his topology of philosophical systems, in particular ― the discrimination between organic and non-organic worldview. A historico-philosophical analysis of Lossky’s cosmology allows revealing the interaction of gnoseological and ontological principles of his system, e.g. explicating the difference of Lossky’s intuitionism from the one of Bergson. The key section of the organic worldview is the doctrine of the hierarchy of substantival agents: the hierarchical personalism, as well as the notions of transcreation, dynamic understanding of matter, and the doctrine of free will closely related to it. The paper specifies the peculiarities of Lossky’s interpretations of panvitalism and panpsychism, as well as the doctrine of reincarnation, which has a particular place in his system. The final stage of Lossky’s cosmological ideas development is his ontological aesthetics: on this stage he understands the world as an embodiment of beauty. The conclusion is drawn that Lossky’s cosmological doctrine is Christian and metaphysical in its nature.
Particle cosmology comes of age
International Nuclear Information System (INIS)
Turner, M.S.
1988-01-01
The application of modern ideas in particle physics to astrophysical and cosmological settings is a continuation of a fruitful tradition in astrophysics which began with the application of atomic physics, and then nuclear physics. In the past decade particle cosmology and particle astrophysics have been recognized as 'legitimate activities' by both particle physicists and astrophysicists and astronomers. During this time there has been a high level of theoretical activity producing much speculation about the earliest history of the Universe, as well as important and interesting astrophysical and cosmological constraints to particle physics theories. This period of intense theoretical activity has produced a number of ideas most worthy of careful consideration and scrutiny, and even more importantly, amenable to experimental/observational test. Among the ideas which are likely to be tested in the next decade are: the cosmological bound to the number of neutrino flavors, inflation, relic WIMPs as the dark matter, and MSW neutrino oscillations as a solution to the solar neutrino problems. (orig.)
Particle cosmology comes of age
International Nuclear Information System (INIS)
Turner, M.S.
1987-12-01
The application of modern ideas in particle physics to astrophysical and cosmological settings is a continuation of a fruitful tradition in astrophysics which began with the application of atomic physics, and then nuclear physics. In the past decade particle cosmology and particle astrophysics have been recognized as 'legitimate activities' by both particle physicists and astrophysicists and astronomers. During this time there has been a high level of theoretical activity producing much speculation about the earliest history of the Universe, as well as important and interesting astrophysical and cosmological constraints to particle physics theories. This period of intense theoretical activity has produced a number of ideas most worthy of careful consideration and scrutiny, and even more importantly, amenable to experimental/observational test. Among the ideas which are likely to be tested in the next decade are: the cosmological bound to the number of neutrino flavors, inflation, relic WIMPs as the dark matter, and MSW neutrino oscillations as a solution to the solar neutrino problems. 94 refs
Cosmological N -body simulations including radiation perturbations
DEFF Research Database (Denmark)
Brandbyge, Jacob; Rampf, Cornelius; Tram, Thomas
2017-01-01
CosmologicalN-body simulations are the standard tools to study the emergence of the observed large-scale structure of the Universe. Such simulations usually solve for the gravitational dynamics of matter within the Newtonian approximation, thus discarding general relativistic effects such as the ......CosmologicalN-body simulations are the standard tools to study the emergence of the observed large-scale structure of the Universe. Such simulations usually solve for the gravitational dynamics of matter within the Newtonian approximation, thus discarding general relativistic effects...
Cosmological Hubble constant and nuclear Hubble constant
International Nuclear Information System (INIS)
Horbuniev, Amelia; Besliu, Calin; Jipa, Alexandru
2005-01-01
The evolution of the Universe after the Big Bang and the evolution of the dense and highly excited nuclear matter formed by relativistic nuclear collisions are investigated and compared. Values of the Hubble constants for cosmological and nuclear processes are obtained. For nucleus-nucleus collisions at high energies the nuclear Hubble constant is obtained in the frame of different models involving the hydrodynamic flow of the nuclear matter. Significant difference in the values of the two Hubble constant - cosmological and nuclear - is observed
Conformal cosmological model and SNe Ia data
International Nuclear Information System (INIS)
Zakharov, A. F.; Pervushin, V. N.
2012-01-01
Now there is a huge scientific activity in astrophysical studies and cosmological ones in particular. Cosmology transforms from a pure theoretical branch of science into an observational one. All the cosmological models have to pass observational tests. The supernovae type Ia (SNe Ia) test is among the most important ones. If one applies the test to determine parameters of the standard Friedmann-Robertson-Walker cosmological model one can conclude that observations lead to the discovery of the dominance of the Λ term and as a result to an acceleration of the Universe. However, there are big mysteries connected with an origin and an essence of dark matter (DM) and the Λ term or dark energy (DE). Alternative theories of gravitation are treated as a possible solution of DM and DE puzzles. The conformal cosmological approach is one of possible alternatives to the standard ΛCDM model. As it was noted several years ago, in the framework of the conformal cosmological approach an introduction of a rigid matter can explain observational data without Λ term (or dark energy). We confirm the claim with much larger set of observational data.
International Nuclear Information System (INIS)
Gaisser, T.K.; Shafi, Q.; Barr, S.M.; Seckel, D.; Rusjan, E.; Fletcher, R.S.
1991-01-01
This report discusses research of professor at Bartol research institute in the following general areas: particle phenomenology and non-accelerator physics; particle physics and cosmology; theories with higher symmetry; and particle astrophysics and cosmology
International Nuclear Information System (INIS)
Heller, M.
1985-01-01
Two Friedman's cosmological papers (1922, 1924) and his own interpretation of the obtained results are briefly reviewed. Discussion follows of Friedman's role in the early development of relativistic cosmology. 18 refs. (author)
Kunze, Kerstin E.
2016-12-20
Cosmology is becoming an important tool to test particle physics models. We provide an overview of the standard model of cosmology with an emphasis on the observations relevant for testing fundamental physics.
International Nuclear Information System (INIS)
Liu Wenxin; Xu, Shanshan; Xing, Baoshan; Pan, Bo; Tao, Shu
2010-01-01
Fractions of soil organic matter in a natural soil were extracted and sorption (or binding) characteristics of phenanthrene on each fraction and to the whole sample were investigated. The organic carbon normalized single point sorption (or binding) coefficient followed lipid > humin (HM) > humic acid (HA) > fulvic acid (FA) > whole soil sample, while the nonlinear exponent exhibited lipid > FA > HA > whole soil sample > HM. FA showed nonlinear binding of phenanthrene as it often does with other fractions. HM and HA contributed the majority of organic carbon in the soil. The calculated sorption coefficients of the whole soil were about two times greater than the measured values at different equilibrium phenanthrene concentrations. As for phenanthrene, the sorption capacity and nonlinearity of the physically mixed HA-HM mixtures were stronger as compared to the chemically reconstituted HA-HM composite. This was attributed to (besides the conditioning effect of the organic solvents) interactions between HA and HM and acid-base additions during fractionation. - Nonlinear binding of phenanthrene to fulvic acid extracted from soil organic matter was found.
Roos, Matts
2015-01-01
The Fourth Edition of Introduction to Cosmology provides a concise, authoritative study of cosmology at an introductory level. Starting from elementary principles and the early history of cosmology, the text carefully guides the student on to curved spacetimes, special and general relativity, gravitational lensing, the thermal history of the Universe, and cosmological models, including extended gravity models, black holes and Hawking's recent conjectures on the not-so-black holes.
Particle physics and cosmology
International Nuclear Information System (INIS)
Turner, M.S.; Schramm, D.N.
1985-01-01
During the past year, the research of the members of our group has spanned virtually all the topics at the interface of cosmology and particle physics: inflationary Universe scenarios, astrophysical and cosmological constraints on particle properties, ultra-high energy cosmic ray physics, quantum field theory in curved space-time, cosmology with extra dimensions, superstring cosmology, neutrino astronomy with large, underground detectors, and the formation of structure in the Universe
The cosmological aspects of food in the material world | Hegarty ...
African Journals Online (AJOL)
There is a general tendency today to believe that all truth worth knowing is to be found in the various branches of the physical sciences. If this were so, there could be no place for a philosophy of matter, or by extension the cosmological aspects of food. In order to vindicate cosmology and its extension from the charge of ...
Variable generalized Chaplygin gas in a 5D cosmology
Salti, Mustafa; Aydogdu, Oktay; Yanar, Hilmi; Sogut, Kenan
2018-03-01
We construct the variable generalized Chaplygin gas (VGCG) defining a unified dark matter-energy scenario and investigate its essential cosmological properties in a universe governed by the Kaluza-Klein (KK) theory. A possible theoretical basis for the VGCG in the KK cosmology is argued. Also, we check the validity of thermodynamical laws and reimplement dynamics of tachyons in the KK universe.
Questions of Modern Cosmology Galileo's Legacy
D'Onofrio, Mauro
2009-01-01
Are we living in the "golden age" of cosmology? Are we close to understanding the nature of the unknown ingredients of the currently most accepted cosmological model and the physics of the early Universe? Or are we instead approaching a paradigm shift? What is dark matter and does it exist? How is it distributed around galaxies and clusters? Is the scientific community open to alternative ideas that may prompt a new scientific revolution - as the Copernican revolution did in Galileo's time? Do other types of supernovae exist that can be of interest for cosmology? Why have quasars never been effectively used as standard candles? Can you tell us about the scientific adventure of COBE? How does the extraction of the Cosmic Microwave Background anisotropy depend on the subtraction of the various astrophysical foregrounds? These, among many others, are the astrophysical, philosophical and sociological questions surrounding modern cosmology and the scientific community that Mauro D'Onofrio and Carlo Burigana pose t...
Improved standard cosmology: Comparison with observation
International Nuclear Information System (INIS)
Wesson, P.S.
1982-01-01
A cosmological model describing inhomogeneous clusters of galaxies embedded in a homogeneous background is compared to observation. In this model, a cluster is described as a spherically symmetric distribution of matter with an inverse-square density law and an isothermal equation of state, while the background universe is essentially the Einstein/de Sitter one of standard cosmology, but with a small pressure. The model is found to be in overall good agreement with observation, and its adjustable parameters are assigned numerical values. The equation of state for a cluster and the finite cosmological pressure are properties of the model which can in principle be investigated by carrying out observations. Subject headings: cosmology: galaxies: clusters of: relativity
Revolutions in astronomy, physics and cosmology
International Nuclear Information System (INIS)
Idlis, G.M.
1985-01-01
As consecutive turning-points in the development of natural science four global natural science revolutions (Aristotelian, Newton, Einstein and post-Einstein) are marked out and briefly outlined. Each of them simultaneously occurred in astronomy, physics and cosmology and was accompanied by radical changes of cosmological representations. These changes had quite a regular consecutive character and represented necessary steps in turn along the natural way of further elimination of ego centrism from cosmology. The first (Aristotelian) revolution turnes out a peculiar prototype of all three subsequent revolutions in astronomy, physics and cosmology. The special more detailed analysis of this revolution in this monograph allows one to tie together antique and modern phases of the science development including corresponding representations on fundamental structural elements of the matter. Besides the review of literature data the monograph comprises a series of author's scientific results
Primordial nucleosynthesis: A cosmological point of view
International Nuclear Information System (INIS)
Mathews, G. J.; Kajino, T.; Yamazaki, D.; Kusakabe, M.; Cheoun, M.-K.
2014-01-01
Primordial nucleosynthesis remains as one of the pillars of modern cosmology. It is the test-ing ground upon which all cosmological models must ultimately rest. It is our only probe of the universe during the first few minutes of cosmic expansion and in particular during the important radiation-dominated epoch. These lectures review the basic equations of space-time, cosmology, and big bang nucleosynthesis. We will then review the current state of observational constraints on primordial abundances along with the key nuclear reactions and their uncertainties. We summarize which nuclear measure-ments are most crucial during the big bang. We also review various cosmological models and their constraints. In particular, we summarize the constraints that big bang nucleosynthesis places upon the possible time variation of fundamental constants, along with constraints on the nature and origin of dark matter and dark energy, long-lived supersymmetric particles, gravity waves, and the primordial magnetic field
Cosmology with primordial black holes
International Nuclear Information System (INIS)
Lindley, D.
1981-09-01
Cosmologies containing a substantial amount of matter in the form of evaporating primordial black holes are investigated. A review of constraints on the numbers of such black holes, including an analysis of a new limit found by looking at the destruction of deuterium by high energy photons, shows that there must be a negligible population of small black holes from the era of cosmological nucleosynthesis onwards, but that there are no strong constraints before this time. The major part of the work is based on the construction of detailed, self-consistent cosmological models in which black holes are continually forming and evaporating The interest in these models centres on the question of baryon generation, which occurs via the asymmetric decay of a new type of particle which appears as a consequence of the recently developed Grand Unified Theories of elementary particles. Unfortunately, there is so much uncertainty in the models that firm conclusions are difficult to reach; however, it seems feasible in principle that primordial black holes could be responsible for a significant part of the present matter density of the Universe. (author)
The Age of Precision Cosmology
Chuss, David T.
2012-01-01
In the past two decades, our understanding of the evolution and fate of the universe has increased dramatically. This "Age of Precision Cosmology" has been ushered in by measurements that have both elucidated the details of the Big Bang cosmology and set the direction for future lines of inquiry. Our universe appears to consist of 5% baryonic matter; 23% of the universe's energy content is dark matter which is responsible for the observed structure in the universe; and 72% of the energy density is so-called "dark energy" that is currently accelerating the expansion of the universe. In addition, our universe has been measured to be geometrically flat to 1 %. These observations and related details of the Big Bang paradigm have hinted that the universe underwent an epoch of accelerated expansion known as Uinflation" early in its history. In this talk, I will review the highlights of modern cosmology, focusing on the contributions made by measurements of the cosmic microwave background, the faint afterglow of the Big Bang. I will also describe new instruments designed to measure the polarization of the cosmic microwave background in order to search for evidence of cosmic inflation.
Phantom cosmologies and fermions
International Nuclear Information System (INIS)
Chimento, Luis P; Forte, Monica; Devecchi, Fernando P; Kremer, Gilberto M
2008-01-01
Form invariance transformations can be used for constructing phantom cosmologies starting with conventional cosmological models. In this work we reconsider the scalar field case and extend the discussion to fermionic fields, where the 'phantomization' process exhibits a new class of possible accelerated regimes. As an application we analyze the cosmological constant group for a fermionic seed fluid
Particle physics and cosmology
International Nuclear Information System (INIS)
Schramm, D.N.; Turner, M.S.
1982-06-01
work is described in these areas: cosmological baryon production; cosmological production of free quarks and other exotic particle species; the quark-hadron transition in the early universe; astrophysical and cosmological constraints on particle properties; massive neutrinos; phase transitions in the early universe; and astrophysical implications of an axion-like particle
International Nuclear Information System (INIS)
Weinberg, S.
1989-01-01
Cosmological constant problem is discussed. History of the problem is briefly considered. Five different approaches to solution of the problem are described: supersymmetry, supergravity, superstring; anthropic approach; mechamism of lagrangian alignment; modification of gravitation theory and quantum cosmology. It is noted that approach, based on quantum cosmology is the most promising one
. ______________________________________________________________________________________ Nobelist George Smoot to Direct Korean Cosmology Institute Nobel Laureate George Smoot has been appointed director of a new cosmology institute in South Korea that will work closely with the year-old Berkeley the Early Universe (IEU) at EWHA Womans University in Seoul, Korea will provide cosmology education
International Nuclear Information System (INIS)
Davies, P.
1991-01-01
The main concepts of cosmology are discussed, and some of the misconceptions are clarified. The features of big bang cosmology are examined, and it is noted that the existence of the cosmic background radiation provides welcome confirmation of the big bang theory. Calculations of relative abundances of the elements conform with observations, further strengthening the confidence in the basic ideas of big bang cosmology
CERN. Geneva. Audiovisual Unit
2001-01-01
Cosmology and particle physics have enjoyed a useful relationship over the entire histories of both subjects. Today, ideas and techniques in cosmology are frequently used to elucidate and constrain theories of elementary particles. These lectures give an elementary overview of the essential elements of cosmology, which is necessary to understand this relationship.
CERN. Geneva
1999-01-01
Cosmology and particle physics have enjoyed a useful relationship over the entire histories of both subjects. Today, ideas and techniques in cosmology are frequently used to elucidate and constrain theories of elementary particles. These lectures give an elementary overview of the essential elements of cosmology, which is necessary to understand this relationship.
International Nuclear Information System (INIS)
Langer, M.
2007-01-01
This is a very concise introductory lecture to Cosmology. We start by reviewing the basics of homogeneous and isotropic cosmology. We then spend some time on the description of the Cosmic Microwave Background. Finally, a small section is devoted to the discussion of the cosmological constant and of some of the related problems
Chamcham, Khalil; Silk, Joseph; Barrow, John D.; Saunders, Simon
2017-04-01
Part I. Issues in the Philosophy of Cosmology: 1. Cosmology, cosmologia and the testing of cosmological theories George F. R. Ellis; 2. Black holes, cosmology and the passage of time: three problems at the limits of science Bernard Carr; 3. Moving boundaries? - comments on the relationship between philosophy and cosmology Claus Beisbart; 4. On the question why there exists something rather than nothing Roderich Tumulka; Part II. Structures in the Universe and the Structure of Modern Cosmology: 5. Some generalities about generality John D. Barrow; 6. Emergent structures of effective field theories Jean-Philippe Uzan; 7. Cosmological structure formation Joel R. Primack; 8. Formation of galaxies Joseph Silk; Part III. Foundations of Cosmology: Gravity and the Quantum: 9. The observer strikes back James Hartle and Thomas Hertog; 10. Testing inflation Chris Smeenk; 11. Why Boltzmann brains do not fluctuate into existence from the de Sitter vacuum Kimberly K. Boddy, Sean M. Carroll and Jason Pollack; 12. Holographic inflation revised Tom Banks; 13. Progress and gravity: overcoming divisions between general relativity and particle physics and between physics and HPS J. Brian Pitts; Part IV. Quantum Foundations and Quantum Gravity: 14. Is time's arrow perspectival? Carlo Rovelli; 15. Relational quantum cosmology Francesca Vidotto; 16. Cosmological ontology and epistemology Don N. Page; 17. Quantum origin of cosmological structure and dynamical reduction theories Daniel Sudarsky; 18. Towards a novel approach to semi-classical gravity Ward Struyve; Part V. Methodological and Philosophical Issues: 19. Limits of time in cosmology Svend E. Rugh and Henrik Zinkernagel; 20. Self-locating priors and cosmological measures Cian Dorr and Frank Arntzenius; 21. On probability and cosmology: inference beyond data? Martin Sahlén; 22. Testing the multiverse: Bayes, fine-tuning and typicality Luke A. Barnes; 23. A new perspective on Einstein's philosophy of cosmology Cormac O
Axions in astrophysics and cosmology
International Nuclear Information System (INIS)
Sikivie, P.
1984-07-01
Axion models often have a spontaneously broken exact discrete symmetry. In that case, they have discretely degenerate vacua and hence domain walls. The properties of the domain walls, the cosmological catastrophe they produce and the ways in which this catastrophe may be avoided are explained. Cosmology and astrophysics provide arguments that imply the axion decay constant should lie in the range 10 8 GeV less than or equal to f/sub a/ less than or equal to 10 12 GeV. Reasons are given why axions are an excellent candidate to constitute the dark matter of galactic halos. Using the coupling of the axions to the electromagnetic field, detectors are described to look for axions floating about in the halo of our galaxy and for axions emitted by the sun
Philosophical Roots of Cosmology
Ivanovic, M.
2008-10-01
We shall consider the philosophical roots of cosmology in the earlier Greek philosophy. Our goal is to answer the question: Are earlier Greek theories of pure philosophical-mythological character, as often philosophers cited it, or they have scientific character. On the bases of methodological criteria, we shall contend that the latter is the case. In order to answer the question about contemporary situation of the relation philosophy-cosmology, we shall consider the next question: Is contemporary cosmology completely independent of philosophical conjectures? The answer demands consideration of methodological character about scientific status of contemporary cosmology. We also consider some aspects of the relation contemporary philosophy-cosmology.
Repulsive and attractive timelike singularities in vacuum cosmologies
International Nuclear Information System (INIS)
Miller, B.D.
1979-01-01
Spherically symmetric cosmologies whose big bang is partially spacelike and partially timelike are constrained to occur only in the presence of certain types of matter, and in such cosmologies the timelike part of the big bang is a negative-mass singularity. In this paper examples are given of cylindrically symmetric cosmologies whose big bang is partially spacelike and partially timelike. These cosmologies are vacuum. In some of them, the timelike part of the big bang is clearly a (generalized) negative-mass singularity, while in others it is a (generalized) positive-mass singularity
Observational and theoretical aspects of relativistic astrophysics and cosmology
International Nuclear Information System (INIS)
Sanz, J.L.; Goicoechea, L.J.
1985-01-01
The studies of relativistic astrophysics and cosmology in these proceedings include primordial nucleosynthesis, nonluminous matter, star and galaxy evolution, cosmic microwave background, and general relativistic models of the universe
A numerical relativity scheme for cosmological simulations
Daverio, David; Dirian, Yves; Mitsou, Ermis
2017-12-01
Cosmological simulations involving the fully covariant gravitational dynamics may prove relevant in understanding relativistic/non-linear features and, therefore, in taking better advantage of the upcoming large scale structure survey data. We propose a new 3 + 1 integration scheme for general relativity in the case where the matter sector contains a minimally-coupled perfect fluid field. The original feature is that we completely eliminate the fluid components through the constraint equations, thus remaining with a set of unconstrained evolution equations for the rest of the fields. This procedure does not constrain the lapse function and shift vector, so it holds in arbitrary gauge and also works for arbitrary equation of state. An important advantage of this scheme is that it allows one to define and pass an adaptation of the robustness test to the cosmological context, at least in the case of pressureless perfect fluid matter, which is the relevant one for late-time cosmology.
García, José De La Luz Montero
2008-01-01
In a concise and simplified way, It was verified with the experimental dates of the Solar System and the 55 Cangri Extrasolar System, that the factor and the constant of planeticity, and the rotational geometric factor are nonlinear, volumetric a constant accelerations universal; it allow to enunciate the Kepler´s Fourth Law and its relation with the Fourth Principle of Thermodynamics. An understanding of the Equivalence Principle is exposed and it proves that the Universal Gravitation is an inverse quadratic function of the energetic-longitudinal constant where all the fundamental interactions converge and universal rotation of the motion of matter.
Cosmological tests of general relativity
International Nuclear Information System (INIS)
Hut, P.
1977-01-01
It is stated that the general relativity theory could be tested on a cosmological scale by measuring the Hubble constant and the deceleration parameter, if, in addition, everything could be known about the matter filling the universe. If, on the other hand, nothing could be presupposed about the matter content of the universe general relativity could not be tested by measuring any number of time derivatives of the scale factor. But upon making the assumption of a universe filled with non-interacting mixture of non-relativistic matter and radiation general relativity can in principle be tested by measuring the first five derivatives of the scale factor. Some general relations are here presented using this assumption. (author)
Modelling non-dust fluids in cosmology
International Nuclear Information System (INIS)
Christopherson, Adam J.; Hidalgo, Juan Carlos; Malik, Karim A.
2013-01-01
Currently, most of the numerical simulations of structure formation use Newtonian gravity. When modelling pressureless dark matter, or 'dust', this approach gives the correct results for scales much smaller than the cosmological horizon, but for scenarios in which the fluid has pressure this is no longer the case. In this article, we present the correspondence of perturbations in Newtonian and cosmological perturbation theory, showing exact mathematical equivalence for pressureless matter, and giving the relativistic corrections for matter with pressure. As an example, we study the case of scalar field dark matter which features non-zero pressure perturbations. We discuss some problems which may arise when evolving the perturbations in this model with Newtonian numerical simulations and with CMB Boltzmann codes
Back Reaction And Local Cosmological Expansion Rate
Geshnizjani, G; Geshnizjani, Ghazal; Brandenberger, Robert
2002-01-01
We calculate the back reaction of cosmological perturbations on a general relativistic variable which measures the local expansion rate of the Universe. Specifically, we consider a cosmological model in which matter is described by a single field. We analyze back reaction both in a matter dominated Universe and in a phase of scalar field-driven chaotic inflation. In both cases, we find that the leading infrared terms contributing to the back reaction vanish when the local expansion rate is measured at a fixed value of the matter field which is used as a clock, whereas they do not appear to vanish if the expansion rate is evaluated at a fixed value of the background time. We discuss possible implications for more realistic models with a more complicated matter sector.
Bianchi type II brane-world cosmologies (U≥0)
International Nuclear Information System (INIS)
Hoogen, R.J. van den; Ibanez, J.
2003-01-01
The asymptotic properties of the Bianchi type II cosmological model in the brane-world scenario are investigated. The matter content is assumed to be a combination of a perfect fluid and a minimally coupled scalar field that is restricted to the brane. The isotropic brane-world solution is determined to represent the initial singularity in all brane-world cosmologies. Additionally, it is shown that it is the kinetic energy of the scalar field which dominates the initial dynamics in these brane-world cosmologies. It is important to note that the dynamics of these brane-world cosmologies is not necessarily asymptotic to general relativistic cosmologies to the future in the case of a zero four-dimensional cosmological constant
Baryon symmetric big bang cosmology
Stecker, F. W.
1978-01-01
Both the quantum theory and Einsteins theory of special relativity lead to the supposition that matter and antimatter were produced in equal quantities during the big bang. It is noted that local matter/antimatter asymmetries may be reconciled with universal symmetry by assuming (1) a slight imbalance of matter over antimatter in the early universe, annihilation, and a subsequent remainder of matter; (2) localized regions of excess for one or the other type of matter as an initial condition; and (3) an extremely dense, high temperature state with zero net baryon number; i.e., matter/antimatter symmetry. Attention is given to the third assumption, which is the simplest and the most in keeping with current knowledge of the cosmos, especially as pertains the universality of 3 K background radiation. Mechanisms of galaxy formation are discussed, whereby matter and antimatter might have collided and annihilated each other, or have coexisted (and continue to coexist) at vast distances. It is pointed out that baryon symmetric big bang cosmology could probably be proved if an antinucleus could be detected in cosmic radiation.
Gauge Invariance and Frame Independence in Cosmology
Weenink, J.G.
2013-01-01
In this thesis the mathematical formulation of cosmological perturbations is studied. First we discuss the gauge problem of general relativity: perturbations of the metric and matter fields in an expanding universe are dependent on the choice of coordinate system, i.e. gauge dependent, even though
Statistical issues in galaxy cluster cosmology
DEFF Research Database (Denmark)
Mantz, Adam; Allen, Steven W.; Rapetti Serra, David Angelo
2013-01-01
The number and growth of massive galaxy clusters is a sensitive probe of cosmological structure formation and dark energy. Surveys at various wavelengths can detect clusters to high redshift, but the fact that cluster mass is not directly observable complicates matters, requiring us to simultaneo...
Supersymmetric Q-balls theory and cosmology
Kusenko, A
1999-01-01
MSSM predicts the existence of Q-balls, some of which can be entirely stable. Both stable and unstable Q-balls can play an important role in cosmology. In particular, Affleck-Dine baryogenesis can result in a copious production of stable baryonic Q-balls, which can presently exist as a form of dark matter.
Cosmology and cluster halo scaling relations
Araya-Melo, Pablo A.; van de Weygaert, Rien; Jones, Bernard J. T.
2009-01-01
We explore the effects of dark matter and dark energy on the dynamical scaling properties of galaxy clusters. We investigate the cluster Faber-Jackson (FJ), Kormendy and Fundamental Plane (FP) relations between the mass, radius and velocity dispersion of cluster-sized haloes in cosmological N-body
Cosmological dynamics of a hybrid chameleon scenario
Nozari, Kourosh; Rashidi, N.
2013-01-01
We consider a hybrid scalar field which is non-minimally coupled to the matter and models a chameleon cosmology. By introducing an effective potential, we study the dependence of the effective potential's minimum and hybrid chameleon field's masses to the local matter density. In a dynamical system technique, we analyze the phase space of this two-field chameleon model, find its fixed points and study their stability. We show that the hybrid chameleon domination solution is a stable attractor...
Cosmology and the expanding Earth hypothesis
International Nuclear Information System (INIS)
Tryon, E.P.
1983-01-01
The standard model of cosmology is briefly presented, together with a recent conjecture that the initial matter in the universe might have been spontaneously created from nothing as a result of relativistic quantum physics. The possibility of Earth expansion from a continuing creation of matter is then considered. A critique is presented of efforts to relate Earth expansion to the Hubble expansion of the universe. Possible changes in Earth radius as a result of diminishing gravity are also discussed
Cosmological production of noncommutative black holes
International Nuclear Information System (INIS)
Mann, Robert B.; Nicolini, Piero
2011-01-01
We investigate the pair creation of noncommutative black holes in a background with a positive cosmological constant. As a first step we derive the noncommutative geometry inspired Schwarzschild-de Sitter solution. By varying the mass and the cosmological constant parameters, we find several spacetimes compatible with the new solution: positive-mass spacetimes admit one cosmological horizon and two, one, or no black hole horizons, while negative-mass spacetimes have just a cosmological horizon. These new black holes share the properties of the corresponding asymptotically flat solutions, including the nonsingular core and thermodynamic stability in the final phase of the evaporation. As a second step we determine the action which generates the matter sector of gravitational field equations and we construct instantons describing the pair production of black holes and the other admissible topologies. As a result we find that for current values of the cosmological constant the de Sitter background is quantum mechanically stable according to experience. However, positive-mass noncommutative black holes and solitons would have plentifully been produced during inflationary times for Planckian values of the cosmological constant. As a special result we find that, in these early epochs of the Universe, Planck size black holes production would have been largely disfavored. We also find a potential instability for production of negative-mass solitons.
Cosmological acceleration. Dark energy or modified gravity?
International Nuclear Information System (INIS)
Bludman, S.
2006-05-01
We review the evidence for recently accelerating cosmological expansion or ''dark energy'', either a negative pressure constituent in General Relativity (Dark Energy) or modified gravity (Dark Gravity), without any constituent Dark Energy. If constituent Dark Energy does not exist, so that our universe is now dominated by pressure-free matter, Einstein gravity must be modified at low curvature. The vacuum symmetry of any Robertson-Walker universe then characterizes Dark Gravity as low- or high-curvature modifications of Einstein gravity. The dynamics of either kind of ''dark energy'' cannot be derived from the homogeneous expansion history alone, but requires also observing the growth of inhomogeneities. Present and projected observations are all consistent with a small fine tuned cosmological constant, but also allow nearly static Dark Energy or gravity modified at cosmological scales. The growth of cosmological fluctuations will potentially distinguish between static and ''dynamic'' ''dark energy''. But, cosmologically distinguishing the Concordance Model ΛCDM from modified gravity will require a weak lensing shear survey more ambitious than any now projected. Dvali-Gabadadze-Porrati low-curvature modifications of Einstein gravity may also be detected in refined observations in the solar system (Lue and Starkman) or at the intermediate Vainstein scale (Iorio) in isolated galaxy clusters. Dark Energy's epicyclic character, failure to explain the original Cosmic Coincidence (''Why so small now?'') without fine tuning, inaccessibility to laboratory or solar system tests, along with braneworld theories, now motivate future precision solar system, Vainstein-scale and cosmological-scale studies of Dark Gravity. (Orig.)
Cosmological acceleration. Dark energy or modified gravity?
Energy Technology Data Exchange (ETDEWEB)
Bludman, S
2006-05-15
We review the evidence for recently accelerating cosmological expansion or ''dark energy'', either a negative pressure constituent in General Relativity (Dark Energy) or modified gravity (Dark Gravity), without any constituent Dark Energy. If constituent Dark Energy does not exist, so that our universe is now dominated by pressure-free matter, Einstein gravity must be modified at low curvature. The vacuum symmetry of any Robertson-Walker universe then characterizes Dark Gravity as low- or high-curvature modifications of Einstein gravity. The dynamics of either kind of ''dark energy'' cannot be derived from the homogeneous expansion history alone, but requires also observing the growth of inhomogeneities. Present and projected observations are all consistent with a small fine tuned cosmological constant, but also allow nearly static Dark Energy or gravity modified at cosmological scales. The growth of cosmological fluctuations will potentially distinguish between static and ''dynamic'' ''dark energy''. But, cosmologically distinguishing the Concordance Model {lambda}CDM from modified gravity will require a weak lensing shear survey more ambitious than any now projected. Dvali-Gabadadze-Porrati low-curvature modifications of Einstein gravity may also be detected in refined observations in the solar system (Lue and Starkman) or at the intermediate Vainstein scale (Iorio) in isolated galaxy clusters. Dark Energy's epicyclic character, failure to explain the original Cosmic Coincidence (''Why so small now?'') without fine tuning, inaccessibility to laboratory or solar system tests, along with braneworld theories, now motivate future precision solar system, Vainstein-scale and cosmological-scale studies of Dark Gravity. (Orig.)
Physically self-consistent basis for modern cosmology
International Nuclear Information System (INIS)
Khlopov, M.Yu.
2000-01-01
Cosmoparticle physics appeared as a natural result of internal development of cosmology seeking physical grounds for inflation, baryosynthesis, and nonbaryonic dark matter and of particle physics going outside the Standard Model of particle interactions. Its aim is to study the foundations of particle physics and cosmology and their fundamental relationship in the combination of respective indirect cosmological, astrophysical, and physical effects. The ideas on new particles and fields predicted by particle theory and on their cosmological impact are discussed, as well as the methods of cosmoparticle physics to probe these ideas, are considered with special analysis of physical mechanisms for inflation, baryosynthesis, and nonbaryonic dark matter. These mechanisms are shown to reflect the main principle of modern cosmology, putting, instead of formal parameters of cosmological models, physical processes governing the evolution of the big-bang universe. Their realization on the basis of particle theory induces additional model-dependent predictions, accessible to various methods of nonaccelerator particle physics. Probes for such predictions, with the use of astrophysical data, are the aim of cosmoarcheology studying astrophysical effects of new physics. The possibility of finding quantitatively definite relationships between cosmological and laboratory effects on the basis of cosmoparticle approach, as well as of obtaining a unique solution to the problem of physical candidates for inflation, mechanisms of baryogenesis, and multicomponent dark matter, is exemplified in terms of gauge model with broken family symmetry, underlying horizontal unification and possessing quantitatively definite physical grounds for inflation, baryosynthesis, and effectively multicomponent dark-matter scenarios
Extending cosmology: the metric approach
Mendoza, S.
2012-01-01
Comment: 2012, Extending Cosmology: The Metric Approach, Open Questions in Cosmology; Review article for an Intech "Open questions in cosmology" book chapter (19 pages, 3 figures). Available from: http://www.intechopen.com/books/open-questions-in-cosmology/extending-cosmology-the-metric-approach
Fast Generation of Ensembles of Cosmological N-Body Simulations via Mode-Resampling
Energy Technology Data Exchange (ETDEWEB)
Schneider, M D; Cole, S; Frenk, C S; Szapudi, I
2011-02-14
We present an algorithm for quickly generating multiple realizations of N-body simulations to be used, for example, for cosmological parameter estimation from surveys of large-scale structure. Our algorithm uses a new method to resample the large-scale (Gaussian-distributed) Fourier modes in a periodic N-body simulation box in a manner that properly accounts for the nonlinear mode-coupling between large and small scales. We find that our method for adding new large-scale mode realizations recovers the nonlinear power spectrum to sub-percent accuracy on scales larger than about half the Nyquist frequency of the simulation box. Using 20 N-body simulations, we obtain a power spectrum covariance matrix estimate that matches the estimator from Takahashi et al. (from 5000 simulations) with < 20% errors in all matrix elements. Comparing the rates of convergence, we determine that our algorithm requires {approx}8 times fewer simulations to achieve a given error tolerance in estimates of the power spectrum covariance matrix. The degree of success of our algorithm indicates that we understand the main physical processes that give rise to the correlations in the matter power spectrum. Namely, the large-scale Fourier modes modulate both the degree of structure growth through the variation in the effective local matter density and also the spatial frequency of small-scale perturbations through large-scale displacements. We expect our algorithm to be useful for noise modeling when constraining cosmological parameters from weak lensing (cosmic shear) and galaxy surveys, rescaling summary statistics of N-body simulations for new cosmological parameter values, and any applications where the influence of Fourier modes larger than the simulation size must be accounted for.
Lam, Chi-Sing
2008-01-01
According to Modern Cosmology, our Universe came from a primordial state 13.7 billion years ago, with no matter and very little energy. In other words, it was almost empty. Where do the stars and galaxies, and everything else in the present universe come from then?. This captivating book provides an answer to this question, and explains the observations and evidence behind the assertion of an almost empty primordial universe. Aimed at a general audience, it assumes no prior knowledge of astronomy or physics. The emptiness of the primordial universe is reminiscent of the emptiness in Zen Buddhi
Energy Technology Data Exchange (ETDEWEB)
Magro, Lluís Martí, E-mail: martillu@suketto.icrr.u-tokyo.ac.jp [Kavli IPMU (WPI), UTIAS, The University of Tokyo, Kashiwa, Chiba 277-8583 (Japan)
2016-06-21
The Super-Kamiokande experiment performs a large variety of studies, many of them in the neutrino sector. The archetypes are atmospheric neutrino (recently awarded with the Nobel prize for Mr. T. Kajita) and the solar neutrinos analyses. In these proceedings we report our latest results and present updates to indirect dark matter searches, our solar neutrino analysis and discuss the future upgrade of Super-Kamiokande by loading gadolinium into our ultra-pure water.
Averaging Robertson-Walker cosmologies
International Nuclear Information System (INIS)
Brown, Iain A.; Robbers, Georg; Behrend, Juliane
2009-01-01
The cosmological backreaction arises when one directly averages the Einstein equations to recover an effective Robertson-Walker cosmology, rather than assuming a background a priori. While usually discussed in the context of dark energy, strictly speaking any cosmological model should be recovered from such a procedure. We apply the scalar spatial averaging formalism for the first time to linear Robertson-Walker universes containing matter, radiation and dark energy. The formalism employed is general and incorporates systems of multiple fluids with ease, allowing us to consider quantitatively the universe from deep radiation domination up to the present day in a natural, unified manner. Employing modified Boltzmann codes we evaluate numerically the discrepancies between the assumed and the averaged behaviour arising from the quadratic terms, finding the largest deviations for an Einstein-de Sitter universe, increasing rapidly with Hubble rate to a 0.01% effect for h = 0.701. For the ΛCDM concordance model, the backreaction is of the order of Ω eff 0 ≈ 4 × 10 −6 , with those for dark energy models being within a factor of two or three. The impacts at recombination are of the order of 10 −8 and those in deep radiation domination asymptote to a constant value. While the effective equations of state of the backreactions in Einstein-de Sitter, concordance and quintessence models are generally dust-like, a backreaction with an equation of state w eff < −1/3 can be found for strongly phantom models
Multiverse understanding of cosmological coincidences
International Nuclear Information System (INIS)
Bousso, Raphael; Hall, Lawrence J.; Nomura, Yasunori
2009-01-01
There is a deep cosmological mystery: although dependent on very different underlying physics, the time scales of structure formation, of galaxy cooling (both radiatively and against the CMB), and of vacuum domination do not differ by many orders of magnitude, but are all comparable to the present age of the universe. By scanning four landscape parameters simultaneously, we show that this quadruple coincidence is resolved. We assume only that the statistical distribution of parameter values in the multiverse grows towards certain catastrophic boundaries we identify, across which there are drastic regime changes. We find order-of-magnitude predictions for the cosmological constant, the primordial density contrast, the temperature at matter-radiation equality, the typical galaxy mass, and the age of the universe, in terms of the fine structure constant and the electron, proton and Planck masses. Our approach permits a systematic evaluation of measure proposals; with the causal patch measure, we find no runaway of the primordial density contrast and the cosmological constant to large values.
Cosmological aspects of spontaneous baryogenesis
Energy Technology Data Exchange (ETDEWEB)
Simone, Andrea De; Kobayashi, Takeshi [SISSA,Via Bonomea 265, 34136 Trieste (Italy); INFN, Sezione di Trieste,Via Bonomea 265, 34136 Trieste (Italy)
2016-08-24
We investigate cosmological aspects of spontaneous baryogenesis driven by a scalar field, and present general constraints that are independent of the particle physics model. The relevant constraints are obtained by studying the backreaction of the produced baryons on the scalar field, the cosmological expansion history after baryogenesis, and the baryon isocurvature perturbations. We show that cosmological considerations alone provide powerful constraints, especially for the minimal scenario with a quadratic scalar potential. Intriguingly, we find that for a given inflation scale, the other parameters including the reheat temperature, decoupling temperature of the baryon violating interactions, and the mass and decay constant of the scalar are restricted to lie within ranges of at most a few orders of magnitude. We also discuss possible extensions to the minimal setup, and propose two ideas for evading constraints on isocurvature perturbations: one is to suppress the baryon isocurvature with nonquadratic scalar potentials, another is to compensate the baryon isocurvature with cold dark matter isocurvature by making the scalar survive until the present.
One dark matter mystery: halos in the cosmic web
Gaite, Jose
2015-01-01
The current cold dark matter cosmological model explains the large scale cosmic web structure but is challenged by the observation of a relatively smooth distribution of matter in galactic clusters. We consider various aspects of modeling the dark matter around galaxies as distributed in smooth halos and, especially, the smoothness of the dark matter halos seen in N-body cosmological simulations. We conclude that the problems of the cold dark matter cosmology on small scales are more serious than normally admitted.
One dark matter mystery: halos in the cosmic web
International Nuclear Information System (INIS)
Gaite, Jose
2015-01-01
The current cold dark matter cosmological model explains the large scale cosmic web structure but is challenged by the observation of a relatively smooth distribution of matter in galactic clusters. We consider various aspects of modeling the dark matter around galaxies as distributed in smooth halos and, especially, the smoothness of the dark matter halos seen in N-body cosmological simulations. We conclude that the problems of the cold dark matter cosmology on small scales are more serious than normally admitted
Nonthermal Supermassive Dark Matter
Chung, Daniel J. H.; Kolb, Edward W.; Riotto, Antonio
1999-01-01
We discuss several cosmological production mechanisms for nonthermal supermassive dark matter and argue that dark matter may he elementary particles of mass much greater than the weak scale. Searches for dark matter should ma be limited to weakly interacting particles with mass of the order of the weak scale, but should extend into the supermassive range as well.
Nonthermal Supermassive Dark Matter
International Nuclear Information System (INIS)
Chung, D.J.; Chung, D.J.; Kolb, E.W.; Kolb, E.W.; Riotto, A.
1998-01-01
We discuss several cosmological production mechanisms for nonthermal supermassive dark matter and argue that dark matter may be elementary particles of mass much greater than the weak scale. Searches for dark matter should not be limited to weakly interacting particles with mass of the order of the weak scale, but should extend into the supermassive range as well. copyright 1998 The American Physical Society
Nonthermal Supermassive Dark Matter
Chung, Daniel J. H.; Kolb, Edward W.; Riotto, Antonio
1998-01-01
We discuss several cosmological production mechanisms for nonthermal supermassive dark matter and argue that dark matter may be elementary particles of mass much greater than the weak scale. Searches for dark matter should not be limited to weakly interacting particles with mass of the order of the weak scale, but should extend into the supermassive range as well.
Directory of Open Access Journals (Sweden)
Balbi Amedeo
2013-09-01
Full Text Available Time has always played a crucial role in cosmology. I review some of the aspects of the present cosmological model which are more directly related to time, such as: the definition of a cosmic time; the existence of typical timescales and epochs in an expanding universe; the problem of the initial singularity and the origin of time; the cosmological arrow of time.
Inflation and quantum cosmology
International Nuclear Information System (INIS)
Linde, A.
1991-01-01
In this article a review of the present status of inflationary cosmology is given. We start with a discussion of the simplest version of the chaotic inflation scenario. Then we discuss some recent develoments in the inflationary cosmology, including the theory of a self-reproducing inflationary universe (eternal chaotic inflation). We do it with the help of stochastic approach to inflation. The results obtained within this approach are compared with the results obtained in the context of Euclidean quantum cosmology. (WL)
International Nuclear Information System (INIS)
Surdin, M.
1980-01-01
It is shown that viewed from the 'outside', our universe is a black hole. Hence the 'inside' cosmology considered is termed as the Bright Universe Cosmology. The model proposed avoids the singularities of cosmologies of the Big Bang variety, it gives a good account of the redshifts, the cosmic background radiation, the number counts; it also gives a satisfactory explanation of the 'large numbers coincidence' and of the variation in time of fundamental constants. (Auth.)
Zhang, Jie-Fang; Li, Yi-Shen; Meng, Jianping; Wu, Lei; Malomed, Boris A.
2010-01-01
We investigate solitons and nonlinear Bloch waves in Bose-Einstein condensates trapped in optical lattices. By introducing specially designed localized profiles of the spatial modulation of the attractive nonlinearity, we construct an infinite number of exact soliton solutions in terms of the Mathieu and elliptic functions, with the chemical potential belonging to the semi-infinite bandgap of the optical-lattice-induced spectrum. Starting from the exact solutions, we employ the relaxation met...
Introduction to particle cosmology the standard model of cosmology and its open problems
Bambi, Cosimo
2016-01-01
This book introduces the basic concepts of particle cosmology and covers all the main aspects of the Big Bang Model (expansion of the Universe, Big Bang Nucleosynthesis, Cosmic Microwave Background, large scale structures) and the search for new physics (inflation, baryogenesis, dark matter, dark energy). It also includes the majority of recent discoveries, such as the precise determination of cosmological parameters using experiments like WMAP and Planck, the discovery of the Higgs boson at LHC, the non-discovery to date of supersymmetric particles, and the search for the imprint of gravitational waves on the CMB polarization by Planck and BICEP. This textbook is based on the authors’ courses on Cosmology, and aims at introducing Particle Cosmology to senior undergraduate and graduate students. It has been especially written to be accessible even for those students who do not have a strong background in General Relativity and quantum field theory. The content of this book is organized in an easy-to-use ...
International Nuclear Information System (INIS)
Sasaki, Misao
1983-01-01
We review the recent status of the inflationary cosmology. After exhibiting the essence of difficulties associated with the horizon, flatness and baryon number problems in the standard big-bang cosmology, we discuss that the inflationary universe scenario is one of the most plausible solutions to these fundamental cosmological problems. Since there are two qualitatively different versions of the inflationary universe scenario, we review each of them separately and discuss merits and demerits of each version. The Hawking radiation in de Sitter space is also reviewed since it may play an essential role in the inflationary cosmology. (author)
Roos, Matts
2003-01-01
The Third Edition of the hugely successful Introduction to Cosmology provides a concise, authoritative study of cosmology at an introductory level. Starting from elementary principles and the history of cosmology, the text carefully guides the student on to curved spacetimes, general relativity, black holes, cosmological models, particles and symmetries, and phase transitions. Extensively revised, this latest edition includes broader and updated coverage of distance measures, gravitational lensing and waves, dark energy and quintessence, the thermal history of the Universe, inflation,
Axions in inflationary cosmology
International Nuclear Information System (INIS)
Linde, A.
1991-01-01
The problem of the cosmological constraints on the axion mass is re-examined. It is argued that in the context of inflationary cosmology the constraint m a > or approx.10 -5 eV can be avoided even when the axion perturbations produced during inflation are taken into account. It is shown also that in most axion models the effective parameter f a rapidly changes during inflation. This modifies some earlier statements concerning isothermal perturbations in the axion cosmology. A hybrid inflation scenario is proposed which combines some advantages of chaotic inflation with specific features of new and/or extended inflation. Its implications for the axion cosmology are discussed. (orig.)
Xenopoulos, M. A.; Vogt, R. J.
2014-12-01
There is now increasing evidence that non-linearity is a common response in ecological systems to pressures caused by human activities. There is also increasing evidence that exogenous environmental drivers, such as climate, induce spatial and temporal synchrony in a wide range of ecological variables. Using Moran's I and Pearson's correlation, we quantified the synchrony of dissolved organic carbon concentration (DOC) and quality (DOM; e.g., specific UV absorbance, Fluorescence Index, PARAFAC), nutrients, discharge and temperature in 40 streams that span an agriculture gradient (0 to >70% cropland), over 10 years. We then used breakpoint regression, 2D-Kolmogorov-Smirnov test and significant zero crossings (SiZer) analyses to quantify the prevalence of nonlinearity and ecological thresholds (breakpoints) where applicable. There was a high degree of synchrony in DOM quality (r > 0.7) but not DOC (r < 0.4). The degree of synchrony was driven in part by the catchment's land use. With respect to the nonlinear analyses we found non-linearity in ~50% of bivariate datasets analyzed. Non-linearity was also driven in part by the catchment's land use. Breakpoints defined different DOM properties. Nonlinearity and synchronous behaviour in DOM are intimately linked to land use.
International Nuclear Information System (INIS)
Schramm, D.N.
1989-12-01
Nuclear physics has provided one of the 2 critical observational tests of all Big Bang cosmology, namely Big Bang Nucleosynthesis. Furthermore, this same nuclear physics input enables a prediction to be made about one of the most fundamental physics questions of all, the number of elementary particle families. This paper reviews the standard Big Bang Nucleosynthesis arguments. The primordial He abundance is inferred from He--C and He--N and He--O correlations. The strengthened Li constraint as well as 2 D plus 3 He are used to limit the baryon density. This limit is the key argument behind the need for non-baryonic dark matter. The allowed number of neutrino families, N ν , is delineated using the new neutron lifetime value of τ n = 890 ± 4s (τ 1/2 = 10.3 min). The formal statistical result is N ν = 2.6 ± 0.3 (1σ) providing a reasonable fit (1.3σ) to 3 families but making a fourth light (m ν approx-lt 10 MeV) neutrino family exceedingly unlikely (approx-gt 4.7σ) (barring significant systematic errors either in D + 3 He, and Li and/or 4 He and/or τ n ). It is also shown that uncertainties induced by postulating a first-order quark-hadron phase transition do not seriously affect the conclusions. 21 refs., 3 figs
Schramm, David N.
1989-01-01
Nuclear physics has provided one of two critical observational tests of all Big Bang cosmology, namely Big Bang Nucleosynthesis. Furthermore, this same nuclear physics input enables a prediction to be made about one of the most fundamental physics questions of all, the number of elementary particle families. The standard Big Bang Nucleosynthesis arguments are reviewed. The primordial He abundance is inferred from He-C and He-N and He-O correlations. The strengthened Li constraint as well as D-2 plus He-3 are used to limit the baryon density. This limit is the key argument behind the need for non-baryonic dark matter. The allowed number of neutrino families, N(nu), is delineated using the new neutron lifetime value of tau(n) = 890 + or - 4s (tau(1/2) = 10.3 min). The formal statistical result is N(nu) = 2.6 + or - 0.3 (1 sigma), providing a reasonable fit (1.3 sigma) to three families but making a fourth light (m(nu) less than or equal to 10 MeV) neutrino family exceedly unlikely (approx. greater than 4.7 sigma). It is also shown that uncertainties induced by postulating a first-order quark-baryon phase transition do not seriously affect the conclusions.
International Nuclear Information System (INIS)
Buchbinder, Evgeny I.; Khoury, Justin; Ovrut, Burt A.
2007-01-01
In this paper, we present a new scenario of the early universe that contains a pre-big bang ekpyrotic phase. By combining this with a ghost condensate, the theory explicitly violates the null energy condition without developing any ghostlike instabilities. Thus the contracting universe goes through a nonsingular bounce and evolves smoothly into the expanding post-big bang phase. The curvature perturbation acquires a scale-invariant spectrum well before the bounce in this scenario. It is sourced by the scale-invariant entropy perturbation engendered by two ekpyrotic scalar fields, a mechanism recently proposed by Lehners et al. Since the background geometry is nonsingular at all times, the curvature perturbation remains nearly constant on superhorizon scales. It emerges from the bounce unscathed and imprints a scale-invariant spectrum of density fluctuations in the matter-radiation fluid at the onset of the hot big bang phase. The ekpyrotic potential can be chosen so that the spectrum has a red tilt, in accordance with the recent data from WMAP. As in the original ekpyrotic scenario, the model predicts a negligible gravity wave signal on all observable scales. As such ''new ekpyrotic cosmology'' provides a consistent and distinguishable alternative to inflation to account for the origin of the seeds of large-scale structure
Superstring thermodynamics and its application to cosmology
International Nuclear Information System (INIS)
Matsuo, N.
1987-01-01
The thermodynamics of superstring theories (SST-I, SST-II) and heterotic string theory and its application to the cosmology are studied. The free energy of superstring gas is calculated in the one-loop approximation and the stability of the extra torus dimensions is discussed. Assuming that the Einstein equation dictates the evolution of the universe, we show that matter dominated universe filled with massive particles would never be realized at the beginning of the universe, contrary to the naive expectation in the superstring cosmology. (orig.)
Cosmology of a covariant Galilean field.
De Felice, Antonio; Tsujikawa, Shinji
2010-09-10
We study the cosmology of a covariant scalar field respecting a Galilean symmetry in flat space-time. We show the existence of a tracker solution that finally approaches a de Sitter fixed point responsible for cosmic acceleration today. The viable region of model parameters is clarified by deriving conditions under which ghosts and Laplacian instabilities of scalar and tensor perturbations are absent. The field equation of state exhibits a peculiar phantomlike behavior along the tracker, which allows a possibility to observationally distinguish the Galileon gravity from the cold dark matter model with a cosmological constant.
Cosmological implications of primordial black holes
Energy Technology Data Exchange (ETDEWEB)
Luis Bernal, José; Bellomo, Nicola; Raccanelli, Alvise; Verde, Licia, E-mail: joseluis.bernal@icc.ub.edu, E-mail: nicola.bellomo@icc.ub.edu, E-mail: alvise@icc.ub.edu, E-mail: liciaverde@icc.ub.edu [ICC, University of Barcelona, IEEC-UB, Martí i Franquès, 1, E08028 Barcelona (Spain)
2017-10-01
The possibility that a relevant fraction of the dark matter might be comprised of Primordial Black Holes (PBHs) has been seriously reconsidered after LIGO's detection of a ∼ 30 M {sub ⊙} binary black holes merger. Despite the strong interest in the model, there is a lack of studies on possible cosmological implications and effects on cosmological parameters inference. We investigate correlations with the other standard cosmological parameters using cosmic microwave background observations, finding significant degeneracies, especially with the tilt of the primordial power spectrum and the sound horizon at radiation drag. However, these degeneracies can be greatly reduced with the inclusion of small scale polarization data. We also explore if PBHs as dark matter in simple extensions of the standard ΛCDM cosmological model induces extra degeneracies, especially between the additional parameters and the PBH's ones. Finally, we present cosmic microwave background constraints on the fraction of dark matter in PBHs, not only for monochromatic PBH mass distributions but also for popular extended mass distributions. Our results show that extended mass distribution's constraints are tighter, but also that a considerable amount of constraining power comes from the high-ℓ polarization data. Moreover, we constrain the shape of such mass distributions in terms of the correspondent constraints on the PBH mass fraction.
Ermakov-Pinney equation in scalar field cosmologies
International Nuclear Information System (INIS)
Hawkins, Rachael M.; Lidsey, James E.
2002-01-01
It is shown that the dynamics of cosmologies sourced by a mixture of perfect fluids and self-interacting scalar fields are described by the nonlinear, Ermakov-Pinney equation. The general solution of this equation can be expressed in terms of particular solutions to a related, linear differential equation. This characteristic is employed to derive exact cosmologies in the inflationary and quintessential scenarios. The relevance of the Ermakov-Pinney equation to the braneworld scenario is discussed
Barotropic FRW cosmologies with Chiellini damping
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Rosu, Haret C., E-mail: hcr@ipicyt.edu.mx [IPICyT, Instituto Potosino de Investigacion Cientifica y Tecnologica, Camino a la presa San José 2055, Col. Lomas 4a Sección, 78216 San Luis Potosí, SLP (Mexico); Mancas, Stefan C., E-mail: stefan.mancas@erau.edu [Department of Mathematics, Embry–Riddle Aeronautical University, Daytona Beach, FL 32114-3900 (United States); Chen, Pisin, E-mail: pisinchen@phys.ntu.edu.tw [Leung Center for Cosmology and Particle Astrophysics (LeCosPA) and Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China)
2015-05-08
It is known that barotropic FRW equations written in the conformal time variable can be reduced to simple linear equations for an exponential function involving the conformal Hubble rate. Here, we show that an interesting class of barotropic universes can be obtained in the linear limit of a special type of nonlinear dissipative Ermakov–Pinney equations with the nonlinear dissipation built from Chiellini's integrability condition. These cosmologies, which evolutionary are similar to the standard ones, correspond to barotropic fluids with adiabatic indices rescaled by a particular factor and have amplitudes of the scale factors inverse proportional to the adiabatic index. - Highlights: • Chiellini-damped Ermakov–Pinney equations are used in barotropic FRW cosmological context. • Chiellini-damped scale factors of the barotropic FRW universes are introduced. • These scale factors are similar to the undamped ones.
Nonlinear spherical perturbations in quintessence models of dark energy
Pratap Rajvanshi, Manvendra; Bagla, J. S.
2018-06-01
Observations have confirmed the accelerated expansion of the universe. The accelerated expansion can be modelled by invoking a cosmological constant or a dynamical model of dark energy. A key difference between these models is that the equation of state parameter w for dark energy differs from ‑1 in dynamical dark energy (DDE) models. Further, the equation of state parameter is not constant for a general DDE model. Such differences can be probed using the variation of scale factor with time by measuring distances. Another significant difference between the cosmological constant and DDE models is that the latter must cluster. Linear perturbation analysis indicates that perturbations in quintessence models of dark energy do not grow to have a significant amplitude at small length scales. In this paper we study the response of quintessence dark energy to non-linear perturbations in dark matter. We use a fully relativistic model for spherically symmetric perturbations. In this study we focus on thawing models. We find that in response to non-linear perturbations in dark matter, dark energy perturbations grow at a faster rate than expected in linear perturbation theory. We find that dark energy perturbation remains localised and does not diffuse out to larger scales. The dominant drivers of the evolution of dark energy perturbations are the local Hubble flow and a supression of gradients of the scalar field. We also find that the equation of state parameter w changes in response to perturbations in dark matter such that it also becomes a function of position. The variation of w in space is correlated with density contrast for matter. Variation of w and perturbations in dark energy are more pronounced in response to large scale perturbations in matter while the dependence on the amplitude of matter perturbations is much weaker.
The cosmological principle is not in the sky
Park, Chan-Gyung; Hyun, Hwasu; Noh, Hyerim; Hwang, Jai-chan
2017-08-01
The homogeneity of matter distribution at large scales, known as the cosmological principle, is a central assumption in the standard cosmological model. The case is testable though, thus no longer needs to be a principle. Here we perform a test for spatial homogeneity using the Sloan Digital Sky Survey Luminous Red Galaxies (LRG) sample by counting galaxies within a specified volume with the radius scale varying up to 300 h-1 Mpc. We directly confront the large-scale structure data with the definition of spatial homogeneity by comparing the averages and dispersions of galaxy number counts with allowed ranges of the random distribution with homogeneity. The LRG sample shows significantly larger dispersions of number counts than the random catalogues up to 300 h-1 Mpc scale, and even the average is located far outside the range allowed in the random distribution; the deviations are statistically impossible to be realized in the random distribution. This implies that the cosmological principle does not hold even at such large scales. The same analysis of mock galaxies derived from the N-body simulation, however, suggests that the LRG sample is consistent with the current paradigm of cosmology, thus the simulation is also not homogeneous in that scale. We conclude that the cosmological principle is neither in the observed sky nor demanded to be there by the standard cosmological world model. This reveals the nature of the cosmological principle adopted in the modern cosmology paradigm, and opens a new field of research in theoretical cosmology.
Zhang, Jie-Fang; Li, Yi-Shen; Meng, Jianping; Wu, Lei; Malomed, Boris A.
2010-09-01
We investigate solitons and nonlinear Bloch waves in Bose-Einstein condensates trapped in optical lattices (OLs). By introducing specially designed localized profiles of the spatial modulation of the attractive nonlinearity, we construct an infinite set of exact soliton solutions in terms of Mathieu and elliptic functions, with the chemical potential belonging to the semi-infinite gap of the OL-induced spectrum. Starting from the particular exact solutions, we employ the relaxation method to construct generic families of soliton solutions in a numerical form. The stability of the solitons is investigated through the computation of the eigenvalues for small perturbations, and also by direct simulations. Finally, we demonstrate a virtually exact (in the numerical sense) composition relation between nonlinear Bloch waves and solitons.
International Nuclear Information System (INIS)
Zhang Jiefang; Meng Jianping; Wu Lei; Li Yishen; Malomed, Boris A.
2010-01-01
We investigate solitons and nonlinear Bloch waves in Bose-Einstein condensates trapped in optical lattices (OLs). By introducing specially designed localized profiles of the spatial modulation of the attractive nonlinearity, we construct an infinite set of exact soliton solutions in terms of Mathieu and elliptic functions, with the chemical potential belonging to the semi-infinite gap of the OL-induced spectrum. Starting from the particular exact solutions, we employ the relaxation method to construct generic families of soliton solutions in a numerical form. The stability of the solitons is investigated through the computation of the eigenvalues for small perturbations, and also by direct simulations. Finally, we demonstrate a virtually exact (in the numerical sense) composition relation between nonlinear Bloch waves and solitons.
International Nuclear Information System (INIS)
Klebanov, I.; Susskind, L.
1988-10-01
We review Coleman's wormhole mechanism for the vanishing of the cosmological constant. We find a discouraging result that wormholes much bigger than the Planck size are generated. We also consider the implications of the wormhole theory for cosmology. 7 refs., 2 figs
Particle physics and cosmology
International Nuclear Information System (INIS)
Ellis, J.; Nanopoulos, D.
1983-01-01
The authors describe the connection between cosmology and particle physics in an introductory way. In this connection the big bang theory and unified gauge models of strong, electromagnetic, and weak interactions are considered. Furthermore cosmological nucleosynthesis is discussed in this framework, and the problem of cosmic neutrinos is considered with special regards to its rest mass. (HSI).
van de Weygaert, Rien; van Albada, Tjeerd S.
1996-01-01
A detailed account of the ways in which a square kilometer array could further cosmological research. Observational and theoretical studies of the large scale structure and morphology of the local universe are reviewed against the potential capabilities of a new generation telescope. Cosmological
Barkana, Rennan; Tsujikawa, Shinji; Kim, Jihn E; Nagamine, Kentaro
2018-01-01
The Encyclopedia of Cosmology, in four volumes, is a major, long-lasting, seminal reference at the graduate student level, laid out by the most prominent, respected researchers in the general field of Cosmology. These volumes will be a comprehensive review of the most important concepts and current status in the field, covering both theory and observation.
Energy Technology Data Exchange (ETDEWEB)
Vilenkin, Alexander, E-mail: vilenkin@cosmos.phy.tufts.ed [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States)
2010-01-01
The 'new standard cosmology', based on the theory of inflation, has very impressive observational support. I review some outstanding problems of the new cosmology and the global view of the universe - the multiverse - that it suggests. I focus in particular on prospects for further observational tests of inflation and of the multiverse.
International Nuclear Information System (INIS)
Vilenkin, Alexander
2010-01-01
The n ew standard cosmology , based on the theory of inflation, has very impressive observational support. I review some outstanding problems of the new cosmology and the global view of the universe - the multiverse - that it suggests. I focus in particular on prospects for further observational tests of inflation and of the multiverse.
Cosmology, cosmogony and theogony in Parmenides’ poem
Directory of Open Access Journals (Sweden)
Luis Andrés Bredlow
2010-12-01
Full Text Available The aim of this paper is to offer a fresh reconstruction of Parmenides’ system of the physical world, duly distinguishing the cosmological, cosmogonic and theogonic moments of the theory, whose confusion has been a main source of misunderstanding in earlier interpretations. In particular, the system of wreaths or bands of B 12 and A 37 does not represent the present order of the universe, but the general structure of matter, as well as the initial stage of the cosmogony (section 1, as can be substantiated also from Simplicius’ reading of the fragments (section 2. This distinction will allow a tentative reconstruction of Parmenides’ cosmogony (section 3 and cosmology, whose most striking feature is the position of the fixed stars below the sun and the moon, paralleled in Anaximander and —as I will try to show— in the cosmology of the orphic Derveni Papyrus (section 4.
Inflation after COBE: Lectures on inflationary cosmology
International Nuclear Information System (INIS)
Turner, M.S.
1992-01-01
In these lectures I review the standard hot big-bang cosmology, emphasizing its successes, its shortcomings, and its major challenge-a detailed understanding of the formation of structure in the Universe. I then discuss the motivations for and the fundamentals of inflationary cosmology, particularly emphasizing the quantum origin of metric (density and gravity-wave) perturbations. Inflation addresses the shortcomings of the standard cosmology and provides the ''initial data'' for structure formation. I conclude by addressing the implications of inflation for structure formation, evaluating the various cold dark matter models in the light of the recent detection of temperature anisotropies in the cosmic background radiation by COBE. In the near term, the study of structure formation offers a powerful probe of inflation, as well as specific inflationary models
Inflation after COBE: Lectures on inflationary cosmology
Energy Technology Data Exchange (ETDEWEB)
Turner, M.S. [Chicago Univ., IL (United States). Enrico Fermi Inst.]|[Fermi National Accelerator Lab., Batavia, IL (United States)
1992-12-31
In these lectures I review the standard hot big-bang cosmology, emphasizing its successes, its shortcomings, and its major challenge-a detailed understanding of the formation of structure in the Universe. I then discuss the motivations for and the fundamentals of inflationary cosmology, particularly emphasizing the quantum origin of metric (density and gravity-wave) perturbations. Inflation addresses the shortcomings of the standard cosmology and provides the ``initial data`` for structure formation. I conclude by addressing the implications of inflation for structure formation, evaluating the various cold dark matter models in the light of the recent detection of temperature anisotropies in the cosmic background radiation by COBE. In the near term, the study of structure formation offers a powerful probe of inflation, as well as specific inflationary models.
Cosmology in Poincaré gauge gravity with a pseudoscalar torsion
Energy Technology Data Exchange (ETDEWEB)
Lu, Jianbo; Chee, Guoying [Department of Physics, Liaoning Normal University,Dalian 116029 (China)
2016-05-04
A cosmology of Poincare{sup ´} gauge theory is developed, where several properties of universe corresponding to the cosmological equations with the pseudoscalar torsion function are investigated. The cosmological constant is found to be the intrinsic torsion and curvature of the vacuum universe and is derived from the theory naturally rather than added artificially, i.e. the dark energy originates from geometry and includes the cosmological constant but differs from it. The cosmological constant puzzle, the coincidence and fine tuning problem are relieved naturally at the same time. By solving the cosmological equations, the analytic cosmological solution is obtained and can be compared with the ΛCDM model. In addition, the expressions of density parameters of the matter and the geometric dark energy are derived, and it is shown that the evolution of state equations for the geometric dark energy agrees with the current observational data. At last, the full equations of linear cosmological perturbations and the solutions are obtained.
Lesgourgues, Julien
2012-01-01
Neutrinos can play an important role in the evolution of the Universe, modifying some of the cosmological observables. In this contribution we summarize the main aspects of cosmological relic neutrinos and we describe how the precision of present cosmological data can be used to learn about neutrino properties, in particular their mass, providing complementary information to beta decay and neutrinoless double-beta decay experiments. We show how the analysis of current cosmological observations, such as the anisotropies of the cosmic microwave background or the distribution of large-scale structure, provides an upper bound on the sum of neutrino masses of order 1 eV or less, with very good perspectives from future cosmological measurements which are expected to be sensitive to neutrino masses well into the sub-eV range.
International Nuclear Information System (INIS)
Verde, L.
2011-01-01
This is the summary of two lectures that aim to give an overview of cosmology. I will not try to be toa rigorous in derivations, nor to give a full historical overview. The idea is to provide a 'taste' of cosmology and some of the interesting topics it covers. The standard cosmological model is presented and I highlight the successes of cosmology over the past decade or so. Keys to the development of the standard cosmological model are observations of the cosmic microwave background and of large-scale structure, which are introduced. Inflation and dark energy and the outlook for the future are also discussed. Slides from the lectures are available from the school web site: physicschool.web.cern.ch/PhysicSchool/CLASHEP/CLASHEP2011/. (author)
Classical and quantum cosmology
Calcagni, Gianluca
2017-01-01
This comprehensive textbook is devoted to classical and quantum cosmology, with particular emphasis on modern approaches to quantum gravity and string theory and on their observational imprint. It covers major challenges in theoretical physics such as the big bang and the cosmological constant problem. An extensive review of standard cosmology, the cosmic microwave background, inflation and dark energy sets the scene for the phenomenological application of all the main quantum-gravity and string-theory models of cosmology. Born of the author's teaching experience and commitment to bridging the gap between cosmologists and theoreticians working beyond the established laws of particle physics and general relativity, this is a unique text where quantum-gravity approaches and string theory are treated on an equal footing. As well as introducing cosmology to undergraduate and graduate students with its pedagogical presentation and the help of 45 solved exercises, this book, which includes an ambitious bibliography...
Verde, L.
2013-06-27
This is the summary of two lectures that aim to give an overview of cosmology. I will not try to be too rigorous in derivations, nor to give a full historical overview. The idea is to provide a "taste" of cosmology and some of the interesting topics it covers. The standard cosmological model is presented and I highlight the successes of cosmology over the past decade or so. Keys to the development of the standard cosmological model are observations of the cosmic microwave background and of large-scale structure, which are introduced. Inflation and dark energy and the outlook for the future are also discussed. Slides from the lectures are available from the school website: physicschool.web.cern.ch/PhysicSchool/CLASHEP/CLASHEP2011/.
International Nuclear Information System (INIS)
Gekman, O.
1982-01-01
The brief essay of the development of the main ideas of relativistic cosmology is presented. The Einstein's cosmological work about the Universe - ''Cosmological considerations in connection with the general relativity theory'' - gave the basis to all further treatments in this field. In 1922 A. Friedman's work appeared, in which the first expanding Universe model was proposed as a solution of the Einstein field equations. The model was spherically closed, but its curvature radius was a function of time. About 1955 the searches for anisotropic homogeneous solutions to Einstein field equation began. It turned out that isotropic cosmological models are unstable in general. The predominant part of them transform to anisotropic at insignificant breaking of isotropy. The discovery of isotropic background cosmic radiation in 1965, along with the Hubble low of the Universe expansion, served as the direct confirmation of cosmology based on the Einstein theory
Chen, Xianfeng; Zeng, Heping; Guo, Qi; She, Weilong
2015-01-01
This book presents an overview of the state of the art of nonlinear optics from weak light nonlinear optics, ultrafast nonlinear optics to electro-optical theory and applications. Topics range from the fundamental studies of the interaction between matter and radiation to the development of devices, components, and systems of tremendous commercial interest for widespread applications in optical telecommunications, medicine, and biotechnology.
Roberts, Alex
2016-08-01
Recently, a new framework for describing the multiverse has been proposed which is based on the principles of quantum mechanics. The framework allows for well-defined predictions, both regarding global properties of the universe and outcomes of particular experiments, according to a single probability formula. This provides complete unification of the eternally inflating multiverse and many worlds in quantum mechanics. We elucidate how cosmological parameters can be calculated in this framework, and study the probability distribution for the value of the cosmological constant. We consider both positive and negative values, and find that the observed value is consistent with the calculated distribution at an order of magnitude level. In particular, in contrast to the case of earlier measure proposals, our framework prefers a positive cosmological constant over a negative one. These results depend only moderately on how we model galaxy formation and life evolution therein. We explore supersymmetric theories in which the Higgs mass is boosted by the non-decoupling D-terms of an extended U(1) X gauge symmetry, defined here to be a general linear combination of hypercharge, baryon number, and lepton number. Crucially, the gauge coupling, gX, is bounded from below to accommodate the Higgs mass, while the quarks and leptons are required by gauge invariance to carry non-zero charge under U(1)X. This induces an irreducible rate, sigmaBR, for pp → X → ll relevant to existing and future resonance searches, and gives rise to higher dimension operators that are stringently constrained by precision electroweak measurements. Combined, these bounds define a maximally allowed region in the space of observables, (sigmaBR, mX), outside of which is excluded by naturalness and experimental limits. If natural supersymmetry utilizes non-decoupling D-terms, then the associated X boson can only be observed within this window, providing a model independent 'litmus test' for this broad
Energy Technology Data Exchange (ETDEWEB)
Sobreira, F.; Rosenfeld, R. [Universidade Estadual Paulista Julio de Mesquita Filho (IFT/UNESP), Sao Paulo, SP (Brazil). Inst. Fisica Teorica; Simoni, F. de; Costa, L.A.N. da; Gaia, M.A.G.; Ramos, B.; Ogando, R.; Makler, M. [Laboratorio Interinstitucional de e-Astronomia (LIneA), Rio de Janeiro, RJ (Brazil)
2011-07-01
Full text: We study the cosmological constraints expected for the upcoming project Dark Energy Survey (DES) with the full functional form of the 2-point angular correlation function. The angular correlation function model applied in this work includes the effects of linear redshift-space distortion, photometric redshift errors (assumed to be Gaussian) and non-linearities prevenient from gravitational infall. The Fisher information matrix is constructed with the full covariance matrix, which takes the correlation between nearby redshift shells in a proper manner. The survey was sliced into 20 redshift shells in the range 0:4 {<=} z {<=} 1:40 with a variable angular scale in order to search only the scale around the signal from the baryon acoustic oscillation, therefore well within the validity of the non-linear model employed. We found that under those assumptions and with a flat {Lambda}CDM WMAP7 fiducial model, the DES will be able to constrain the dark energy equation of state parameter w with a precision of {approx} 20% and the cold dark matter with {approx} 11% when marginalizing over the other 25 parameters (bias is treated as a free parameter for each shell). When applying WMAP7 priors on {Omega}{sub baryon}, {Omega} c{sub dm}, n{sub s}, and HST priors on the Hubble parameter, w is constrained with {approx} 9% precision. This shows that the full shape of the angular correlation function with DES data will be a powerful probe to constrain cosmological parameters. (author)
Observational constraints on electromagnetic Born-Infeld cosmology
Energy Technology Data Exchange (ETDEWEB)
Bretón, Nora; Montiel, Ariadna [Dpto. de Física, Centro de Investigación y de Estudios Avanzados del I.P.N., Apdo. 14–740, D.F. (Mexico); Lazkoz, Ruth, E-mail: nora@fis.cinvestav.mx, E-mail: amontiel@fis.cinvestav.mx [Dpto. de Física Teórica, Universidad del País Vasco, Apdo. 644, E-48080, Bilbao (Spain)
2012-10-01
The cosmological model consisting of an electromagnetic Born-Infeld (BI) field coupled to a Robertson-Walker geometry is tested with the standard probes of SNIa, GRBs and direct Hubble parameter. The analysis shows that the inclusion of the nonlinear electromagnetic component does not contribute in a significative way to the observed expansion. The BI electromagnetic matter is considered with an abundance of Ω{sub BI}, that our best fit leads to Ω{sub BI} = 0.037 when tested with SNIa and the Hubble parameter data (0.1 < z < 1.75); while when tested with GRBs the result is of Ω{sub BI} = 0.304, which may indicate that this electrodynamics was important at epochs close to the appearance of large structure (z ≈ 7), although this late result has not as much reliability as that corresponding to the first two probes, since we know that the dispersion in GRBs data is still considerable. In view of these results we can rule out the electromagnetic Born-Infeld matter as the origin of the present accelerated expansion, this conclusion concerns exclusively the Born-Infeld theory.
Observational constraints on electromagnetic Born-Infeld cosmology
International Nuclear Information System (INIS)
Bretón, Nora; Montiel, Ariadna; Lazkoz, Ruth
2012-01-01
The cosmological model consisting of an electromagnetic Born-Infeld (BI) field coupled to a Robertson-Walker geometry is tested with the standard probes of SNIa, GRBs and direct Hubble parameter. The analysis shows that the inclusion of the nonlinear electromagnetic component does not contribute in a significative way to the observed expansion. The BI electromagnetic matter is considered with an abundance of Ω BI , that our best fit leads to Ω BI = 0.037 when tested with SNIa and the Hubble parameter data (0.1 BI = 0.304, which may indicate that this electrodynamics was important at epochs close to the appearance of large structure (z ≈ 7), although this late result has not as much reliability as that corresponding to the first two probes, since we know that the dispersion in GRBs data is still considerable. In view of these results we can rule out the electromagnetic Born-Infeld matter as the origin of the present accelerated expansion, this conclusion concerns exclusively the Born-Infeld theory
Stability of a Noncanonical Scalar Field Model during Cosmological Date
Directory of Open Access Journals (Sweden)
Z. Ossoulian
2016-01-01
Full Text Available Using the noncanonical model of scalar field, the cosmological consequences of a pervasive, self-interacting, homogeneous, and rolling scalar field are studied. In this model, the scalar field potential is “nonlinear” and decreases in magnitude with increasing the value of the scalar field. A special solution of the nonlinear field equations of ϕ that has time dependency as fixed point is obtained. The fixed point relies on the noncanonical term of action and γ-parameter; this parameter appeared in energy density of scalar field redshift. By means of such fixed point the different eigenvalues of the equation of motion will be obtained. In different epochs in the evolution of the Universe for different values of q and n, the potentials as a function of scalar field are attained. The behavior of baryonic perturbations in linear perturbation scenario as a considerable amount of energy density of scalar field at low redshifts prevents the growth of perturbations in the ordinary matter fluid. The energy density in the scalar field is not appreciably perturbed by nonrelativistic gravitational fields, in either the radiation or matter dominant or scalar field dominated epoch.