Exploring non-linear cosmological matter diffusion coefficients
Velten, Hermano
2014-01-01
Since microscopic velocity diffusion can be incorporated into general relativity in a consistent way, we study cosmological background solutions when the diffusion phenomena takes place in an expanding universe. Our focus here relies on the nature of the diffusion coefficient $\\sigma$ which measures the magnitude of such transport phenomena. We test dynamics where $\\sigma$ has a phenomenological dependence on the scale factor, the matter density, the dark energy and the expansion rate.
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
Energy Technology Data Exchange (ETDEWEB)
Ballesteros, Guillermo [Museo Storico della Fisica e Centro Studi e Ricerche ' ' Enrico Fermi' ' , Piazza del Viminale 1, I-00184 Rome (Italy); Hollenstein, Lukas; Jain, Rajeev Kumar; Kunz, Martin, E-mail: guillermo.ballesteros@pd.infn.it, E-mail: lukas.hollenstein@unige.ch, E-mail: rajeev.jain@unige.ch, E-mail: martin.kunz@unige.ch [Département de Physique Théorique and Center for Astroparticle Physics, Université de Genève, Quai E. Ansermet 24, CH-1211 Genève 4 (Switzerland)
2012-05-01
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.
The Nonlinear cosmological matter power spectrum with massive neutrinos. 1. The Halo model
Energy Technology Data Exchange (ETDEWEB)
Abazajian, Kevork; /Los Alamos; Switzer, Eric R.; /Princeton U.; Dodelson, Scott; /Fermilab /Chicago U., Astron. Astrophys. Ctr.; Heitmann, Katrin; Habib, Salman; /Los
2004-11-01
Measurements of the linear power spectrum of galaxies have placed tight constraints on neutrino masses. We extend the framework of the halo model of cosmological nonlinear matter clustering to include the effect of massive neutrino infall into cold dark matter (CDM) halos. The magnitude of the effect of neutrino clustering for three degenerate mass neutrinos with m{sub v{sub 1}} = 0.9 eV is of order {approx}1%, within the potential sensitivity of upcoming weak lensing surveys. In order to use these measurements to further constrain--or eventually detect--neutrino masses, accurate theoretical predictions of the nonlinear power spectrum in the presence of massive neutrinos will be needed, likely only possible through high-resolution multiple particle (neutrino, CDM and baryon) simulations.
Nonlinear field space cosmology
Mielczarek, Jakub; Trześniewski, Tomasz
2017-08-01
We consider the FRW cosmological model in which the matter content of the Universe (playing the role of an inflaton or quintessence) is given by a novel generalization of the massive scalar field. The latter is a scalar version of the recently introduced nonlinear field space theory, where the physical phase space of a given field is assumed to be compactified at large energies. For our analysis, we choose the simple case of a field with the spherical phase space and endow it with the generalized Hamiltonian analogous to the XXZ Heisenberg model, normally describing a system of spins in condensed matter physics. Subsequently, we study both the homogenous cosmological sector and linear perturbations of such a test field. In the homogenous sector, we find that nonlinearity of the field phase space is becoming relevant for large volumes of the Universe and can lead to a recollapse, and possibly also at very high energies, leading to the phase of a bounce. Quantization of the field is performed in the limit where the nontrivial nature of its phase space can be neglected, while there is a nonvanishing contribution from the Lorentz symmetry breaking term of the Hamiltonian. As a result, in the leading order of the XXZ anisotropy parameter, we find that the inflationary spectral index remains unmodified with respect to the standard case but the total amplitude of perturbations is subject to a correction. The Bunch-Davies vacuum state also becomes appropriately corrected. The proposed new approach is bringing cosmology and condensed matter physics closer together, which may turn out to be beneficial for both disciplines.
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.
Cosmological effects of nonlinear electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Novello, M [Instituto de Cosmologia Relatividade Astrofisica (ICRA-Brasil/CBPF), Rua Dr Xavier Sigaud, 150, CEP 22290-180, Rio de Janeiro (Brazil); Goulart, E [Instituto de Cosmologia Relatividade Astrofisica (ICRA-Brasil/CBPF), Rua Dr Xavier Sigaud, 150, CEP 22290-180, Rio de Janeiro (Brazil); Salim, J M [Instituto de Cosmologia Relatividade Astrofisica (ICRA-Brasil/CBPF), Rua Dr Xavier Sigaud, 150, CEP 22290-180, Rio de Janeiro (Brazil); Bergliaffa, S E Perez [Departamento de Fisica Teorica, Universidade do Estado do Rio de Janeiro, R. Sao Francisco Xavier, 524, Maracana, CEP 20559-900, Rio de Janeiro (Brazil)
2007-06-07
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.
Cosmology with matter diffusion
Calogero, Simone
2013-01-01
We construct a viable cosmological model based on velocity diffusion of matter particles. In order to ensure the conservation of the total energy-momentum tensor in the presence of diffusion, we include a cosmological scalar field $\\phi$ which we identify with the dark energy component of the Universe. The model is characterized by only one new degree of freedom, the diffusion parameter $\\sigma$. The standard $\\Lambda$CDM model can be recovered by setting $\\sigma=0$. If diffusion takes place ($\\sigma >0$) the dynamics of the matter and of the dark energy fields are coupled. We argue that the existence of a diffusion mechanism in the Universe can serve as a theoretical motivation for interacting models. We constrain the background dynamics of the diffusion model with Supernovae, H(z) and BAO data. We also perform a perturbative analysis of this model in order to understand structure formation in the Universe. We calculate the impact of diffusion both on the CMB spectrum, with particular attention to the integr...
Dark matter and cosmological nucleosynthesis
Schramm, D. N.
1986-01-01
Existing dark matter problems, i.e., dynamics, galaxy formation and inflation, are considered, along with a model which proposes dark baryons as the bulk of missing matter in a fractal universe. It is shown that no combination of dark, nonbaryonic matter can either provide a cosmological density parameter value near unity or, as in the case of high energy neutrinos, allow formation of condensed matter at epochs when quasars already existed. The possibility that correlations among galactic clusters are scale-free is discussed. Such a distribution of matter would yield a fractal of 1.2, close to a one-dimensional universe. Biasing, cosmic superstrings, and percolated explosions and hot dark matter are theoretical approaches that would satisfy the D = 1.2 fractal model of the large-scale structure of the universe and which would also allow sufficient dark matter in halos to close the universe.
Dipolar Dark Matter and Cosmology
Blanchet, Luc; Tiec, Alexandre Le; Marsat, Sylvain
2013-01-01
The phenomenology of the modified Newtonian dynamics (MOND) can be recovered from a mechanism of "gravitational polarization" of some dipolar medium playing the role of dark matter. We review a relativistic model of dipolar dark matter (DDM) within standard general relativity to describe, at some effective level, a fluid polarizable in a gravitational field. At first order in cosmological perturbation theory, this model is equivalent to the concordance cosmological scenario, or Lambda-cold dark matter (CDM) model. At second order, however, the internal energy of DDM modifies the curvature perturbation generated by CDM. This correction, which depends quadratically on the dipole, induces a new type of non-Gaussianity in the bispectrum of the curvature perturbation with respect to standard CDM. Recent observations by the Planck satellite impose stringent constraints on the primordial value of the dipole field.
Fundamental Particle Structure in the Cosmological Dark Matter
Khlopov, Maxim Yu
2013-01-01
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 non-interacting 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 super-high energy physics in the early Universe. Evaporating PBHs turn to be a source of even superweakly interacting particles, while...
What's the Matter in Cosmology?
Clifton, Timothy
2015-01-01
Almost all models of the universe start by assuming that matter fields can be modelled as dust. In the real universe, however, matter is clumped into dense objects that are separated by regions of space that are almost empty. If we are to treat such a distribution of matter as being modelled as a fluid, in some average or coarse-grained sense, then there a number of questions that must be answered. One of the most fundamental of these is whether or not the interaction energy between masses should gravitate. If it does, then a dust-like description may not be sufficient. We would then need to ask how interaction energies should be calculated in cosmology, and how they should appear in the Friedmann-like equations that govern the large-scale behaviour of the universe. I will discuss some recent results that may shed light on these questions.
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
Isotropic cosmological singularities other matter models
Tod, K P
2003-01-01
Isotropic cosmological singularities are singularities which can be removed by rescaling the metric. In some cases already studied (gr-qc/9903008, gr-qc/9903009, gr-qc/9903018) existence and uniqueness of cosmological models with data at the singularity has been established. These were cosmologies with, as source, either perfect fluids with linear equations of state or massless, collisionless particles. In this article we consider how to extend these results to a variety of other matter models. These are scalar fields, massive collisionless matter, the Yang-Mills plasma of Choquet-Bruhat, or matter satisfying the Einstein-Boltzmann equation.
Cosmological perturbations in mimetic matter model
Matsumoto, Jiro; Sushkov, Sergey V
2015-01-01
We investigate the cosmological evolution of mimetic matter model with arbitrary scalar potential. The cosmological reconstruction is explicitly done for different choices of potential. The cases that mimetic matter model shows the evolution as Cold Dark Matter(CDM), wCDM model, dark matter and dark energy with dynamical $Om(z)$ or phantom dark energy with phantom-non-phantom crossing are presented in detail. The cosmological perturbations for such evolution are studied in mimetic matter model. For instance, the evolution behavior of the matter density contrast which is different from usual one, i.e. $\\ddot \\delta + 2 H \\dot \\delta - \\kappa ^2 \\rho \\delta /2 = 0$ is investigated. The possibility of peculiar evolution of $\\delta$ in the model under consideration is shown. Special attention is paid to the behavior of matter density contrast near to future singularity where decay of perturbations may occur much earlier the singularity.
Dimensionless constants, cosmology and other dark matters
Tegmark, M; Rees, M; Wilczek, F; Tegmark, Max; Aguirre, Anthony; Rees, Martin; Wilczek, Frank
2006-01-01
We identify 31 dimensionless physical constants required by particle physics and cosmology, and emphasize that both microphysical constraints and selection effects might help elucidate their origin. Axion cosmology provides an instructive example, in which these two kinds of arguments must both be taken into account, and work well together. If a Peccei-Quinn phase transition occurred before or during inflation, then the axion dark matter density will vary from place to place with a probability distribution. By calculating the net dark matter halo formation rate as a function of all four relevant cosmological parameters and assessing other constraints, we find that this probability distribution, computed at stable solar systems, is arguably peaked near the observed dark matter density. If cosmologically relevant WIMP dark matter is discovered, then one naturally expects comparable densities of WIMPs and axions, making it important to follow up with precision measurements to determine whether WIMPs account for ...
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
The cosmological origins of nonlinear Electrodynamics
Novello, M
2016-01-01
We present a mechanism that allows to describe any nonlinear theory of Electrodynamics as a consequence of the coupling of the electromagnetic field to gravity in the presence of a vacuum represented by the cosmological constant. We emphasize gravity\\rq s exclusive role of catalysis.
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.
Non-linear (loop) quantum cosmology
Bojowald, Martin; Dantas, Christine C; Jaffe, Matthew; Simpson, David
2012-01-01
Inhomogeneous quantum cosmology is modeled as a dynamical system of discrete patches, whose interacting many-body equations can be mapped to a non-linear minisuperspace equation by methods analogous to Bose-Einstein condensation. Complicated gravitational dynamics can therefore be described by more-manageable equations for finitely many degrees of freedom, for which powerful solution procedures are available, including effective equations. The specific form of non-linear and non-local equations suggests new questions for mathematical and computational investigations, and general properties of non-linear wave equations lead to several new options for physical effects and tests of the consistency of loop quantum gravity. In particular, our quantum cosmological methods show how sizeable quantum corrections in a low-curvature universe can arise from tiny local contributions adding up coherently in large regions.
Cosmology with higher-derivative matter fields
Harko, Tiberiu; Saridakis, Emmanuel N
2014-01-01
We investigate the cosmological implications of a new class of modified gravity, where the field equations generically include higher-order derivatives of the matter fields, arising from the introduction of non-dynamical auxiliary fields in the action. Imposing a flat, homogeneous and isotropic geometry we extract the Friedmann equations, obtaining an effective dark-energy sector containing higher derivatives of the matter energy density and pressure. For the cases of dust, radiation, and stiff matter we analyze the cosmological behavior, finding accelerating, de Sitter, and non-accelerating phases, dominated by matter or dark energy. Additionally, the effective dark-energy equation-of-state parameter can be quintessence-like, cosmological-constant-like, or even phantom-like. The detailed study of these scenarios may provide signatures that could distinguish them from other candidates of modified gravity.
Flowing with Time: a New Approach to Nonlinear Cosmological Perturbations
Pietroni, Massimo
2008-01-01
Nonlinear effects are crucial in order to compute the cosmological matter power spectrum to the accuracy required by future generation surveys. Here, a new approach is presented, in which the power spectrum and the bispectrum are obtained -at any redshift and for any momentum scale- by integrating a coupled system of differential equations. The solution of the equations corresponds, in perturbation theory, to the summation of an infinite class of corrections. Compared to other resummation frameworks, the scheme discussed here is particularly suited to cosmologies other than LambdaCDM, such as those based on modifications of gravity and those containing massive neutrinos. As a first application, we compute the Baryonic Acoustic Oscillation feature of the power spectrum, and compare the results with perturbation theory, the halo model, and N-body simulations. The density-velocity and velocity-velocity power spectra are also computed, showing that they are much less contaminated by nonlinearities than the densit...
A look to nonlinear interacting Ghost dark energy cosmology
Khurshudyan, Martiros
2016-07-01
In this paper, we organize a look to nonlinear interacting Ghost dark energy cosmology involving a discussion on the thermodynamics of the Ghost dark energy, when the universe is bounded via the Hubble horizon. One of the ways to study a dark energy model, is to reconstruct thermodynamics of it. Ghost dark energy is one of the models of the dark energy which has an explicitly given energy density as a function of the Hubble parameter. There is an active discussion towards various cosmological scenarios, where the Ghost dark energy interacts with the pressureless cold dark matter (CDM). Recently, various models of the varying Ghost dark energy has been suggested, too. To have a comprehensive understanding of suggested models, we will discuss behavior of the cosmological parameters on parameter-redshift z plane. Some discussion on Om and statefinder hierarchy analysis of these models is presented. Moreover, up to our knowledge, suggested forms of interaction between the Ghost dark energy and cold dark matter (CDM) are new, therefore, within obtained results, we provide new contribution to previously discussed models available in the literature. Our study demonstrates that the forms of the interactions considered in the Ghost dark energy cosmology are not exotic and the justification of this is due to the recent observational data.
Cosmological models with running cosmological term and decaying dark matter
Szydłowski, Marek; Stachowski, Aleksander
2017-03-01
We investigate the dynamics of the generalized ΛCDM model, which the Λ term is running with the cosmological time. On the example of the model Λ(t) =Λbare + α2/t2 we show the existence of a mechanism of the modification of the scaling law for energy density of dark matter: ρdm ∝a - 3 + λ(t). We use an approach developed by Urbanowski in which properties of unstable vacuum states are analyzed from the point of view of the quantum theory of unstable states. We discuss the evolution of Λ(t) term and pointed out that during the cosmic evolution there is a long phase in which this term is approximately constant. We also present the statistical analysis of both the Λ(t) CDM model with dark energy and decaying dark matter and the ΛCDM standard cosmological model. We use data such as Planck, SNIa, BAO, H(z) and AP test. While for the former we find the best fit value of the parameter Ωα2,0 is negative (energy transfer is from the dark matter to dark energy sector) and the parameter Ωα2,0 belongs to the interval (- 0 . 000040 , - 0 . 000383) at 2- σ level. The decaying dark matter causes to lowering a mass of dark matter particles which are lighter than CDM particles and remain relativistic. The rate of the process of decaying matter is estimated. Our model is consistent with the decaying mechanism producing unstable particles (e.g. sterile neutrinos) for which α2 is negative.
Inhomogenous loop quantum cosmology with matter
Blas, Daniel Martín-de; Marugán, Guillermo A Mena; 10.1088/1742-6596/360/1/012032
2013-01-01
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.
Cosmology with a stiff matter era
Chavanis, Pierre-Henri
2015-11-01
We consider the possibility that the Universe is made of a dark fluid described by a quadratic equation of state P =K ρ2 , where ρ is the rest-mass density and K is a constant. The energy density ɛ =ρ c2+K ρ2 is the sum of two terms: a rest-mass term ρ c2 that mimics "dark matter" (P =0 ) and an internal energy term u =K ρ2=P that mimics a "stiff fluid" (P =ɛ ) in which the speed of sound is equal to the speed of light. In the early universe, the internal energy dominates and the dark fluid behaves as a stiff fluid (P ˜ɛ , ɛ ∝a-6). In the late universe, the rest-mass energy dominates and the dark fluid behaves as pressureless dark matter (P ≃0 , ɛ ∝a-3). We provide a simple analytical solution of the Friedmann equations for a universe undergoing a stiff matter era, a dark matter era, and a dark energy era due to the cosmological constant. This analytical solution generalizes the Einstein-de Sitter solution describing the dark matter era, and the Λ CDM model describing the dark matter era and the dark energy era. Historically, the possibility of a primordial stiff matter era first appeared in the cosmological model of Zel'dovich where the primordial universe is assumed to be made of a cold gas of baryons. A primordial stiff matter era also occurs in recent cosmological models where dark matter is made of relativistic self-gravitating Bose-Einstein condensates (BECs). When the internal energy of the dark fluid mimicking stiff matter is positive, the primordial universe is singular like in the standard big bang theory. It expands from an initial state with a vanishing scale factor and an infinite density. We consider the possibility that the internal energy of the dark fluid is negative (while, of course, its total energy density is positive), so that it mimics anti-stiff matter. This happens, for example, when the BECs have an attractive self-interaction with a negative scattering length. In that case, the primordial universe is nonsingular and
Cosmological Structure Formation in Decaying Dark Matter Models
Cheng, Dalong; Tang, Jiayu
2015-01-01
The standard cold dark matter (CDM) model predicts too many and too dense small structures. We consider an alternative model that the dark matter undergoes two-body decays with cosmological lifetime $\\tau$ into only one type of massive daughters with non-relativistic recoil velocity $V_k$. This decaying dark matter model (DDM) can suppress the structure formation below its free-streaming scale at time scale comparable to $\\tau$. Comparing with warm dark matter (WDM), DDM can better reduce the small structures while being consistent with high redshfit observations. We study the cosmological structure formation in DDM by performing self-consistent N-body simulations and point out that cosmological simulations are necessary to understand the DDM structures especially on non-linear scales. We propose empirical fitting functions for the DDM suppression of the mass function and the mass-concentration relation, which depend on the decay parameters lifetime $\\tau$ and recoil velocity $V_k$, and redshift. The fitting ...
A cosmological solution to mimetic dark matter
Energy Technology Data Exchange (ETDEWEB)
Saadi, Hassan, E-mail: hls01@mail.aub.edu [Physics Department, American University of Beirut, Beirut (Lebanon)
2016-01-11
In this paper, a cosmological solution to Mimetic Dark Matter (MDM) for an exponential potential is provided. Then a solution for the 0-i perturbed Einstein differential equation of MDM is obtained based on an exponential potential that satisfies inflation for some initial conditions. Another general potential is suggested that incorporates inflation too. Then quantum perturbations are included. The constants in the model can be tuned to be in agreement with the fluctuation amplitude of the cosmic microwave background (CMB) radiation. Finally, the spectral index is calculated for the suggested potentials. Moreover, MDM is shown to be a viable model to produce dark matter, inflation, and CMB’s fluctuation.
A cosmological solution to mimetic dark matter
Energy Technology Data Exchange (ETDEWEB)
Saadi, Hassan [American University of Beirut, Physics Department, Beirut (Lebanon)
2016-01-15
In this paper, a cosmological solution to Mimetic Dark Matter (MDM) for an exponential potential is provided. Then a solution for the 0 - i perturbed Einstein differential equation of MDM is obtained based on an exponential potential that satisfies inflation for some initial conditions. Another general potential is suggested that incorporates inflation too. Then quantum perturbations are included. The constants in the model can be tuned to be in agreement with the fluctuation amplitude of the cosmic microwave background (CMB) radiation. Finally, the spectral index is calculated for the suggested potentials. Moreover, MDM is shown to be a viable model to produce dark matter, inflation, and CMB's fluctuation. (orig.)
Cosmological effects of coupled dark matter
Morris, Sophie C F; Padilla, Antonio; Tarrant, Ewan R M
2013-01-01
Many models have been studied that contain more than one species of dark matter and some of these couple the Cold Dark Matter (CDM) to a light scalar field. In doing this we introduce additional long range forces, which in turn can significantly affect our estimates of cosmological parameters if not properly accounted for. It is, therefore, important to study these models and their resulting cosmological implications. We present a model in which a fraction of the total cold dark matter density is coupled to a scalar field. We study the background and perturbation evolution and calculate the resulting Cosmic Microwave Background anisotropy spectra. The greater the fraction of dark matter coupled to the scalar field and the stronger the coupling strength, the greater the deviation of the background evolution from LCDM. Previous work, with a single coupled dark matter species, has found an upper limit on the coupling strength of order O(0.1). We find that with a coupling of this magnitude more than half the dark...
Nonlinear Effects in the Amplitude of Cosmological Density Fluctuations
Juszkiewicz, Roman; Fry, J N; Jaffe, Andrew H
2009-01-01
The amplitude of cosmological density fluctuations, $\\sigma_8$, has been studied and estimated by analysing many cosmological observations. The values of the estimates vary considerably between the various probes. However, different estimators probe the value of $\\sigma_8$ in different cosmological scales and do not take into account the nonlinear evolution of the parameter at late times. We show that estimates of the amplitude of cosmological density fluctuations derived from cosmic flows are systematically higher than those inferred at early epochs because of nonlinear evolution at later times. Here we derive corrections to the value of $\\sigma_8$ and compare amplitudes after accounting for this effect.
Cosmology of bigravity with doubly coupled matter
Comelli, Denis; Koyama, Kazuya; Pilo, Luigi; Tasinato, Gianmassimo
2015-01-01
We study cosmological aspects of a bigravity dRGT model where matter couples to both metrics. At linear order in perturbations two mass scales emerge: an hard one from the dRGT potential, and an environmental dependent one from the coupling of bigravity with matter. During early times the dynamics is dictated by the second mass scale, of order of Hubble scale. Perturbations can be classified according to two different combinations. The first is coupled to matter and follows closely the behavior of GR. The second combination of fluctuations shows no issues in the scalar sector, while problems arise in the tensor and vector sectors. During radiation domination, the tensor mode grows with a power law at super-horizon scales. More dangerously, the propagating vector mode features an exponential instability on sub-horizon scales. We discuss the consequences of such instabilities and speculate on possible ways to deal with them.
Cosmology of bigravity with doubly coupled matter
Energy Technology Data Exchange (ETDEWEB)
Comelli, D. [INFN, Sezione di Ferrara, Via Saragat 1, 44122 Ferrara (Italy); Crisostomi, M.; Koyama, K. [Institute of Cosmology and Gravitation, University of Portsmouth, Burnaby Road, PO1 3FX, Portsmouth (United Kingdom); Pilo, L. [Dipartimento di Fisica, Università di L’Aquila, Via Vetoio, 67010 L’Aquila (Italy); INFN, Laboratori Nazionali del Gran Sasso, Via G. Acitelli 22, 67100 Assergi (Italy); Tasinato, G. [Department of Physics, Swansea University, Singleton Park, SA2 8PP, Swansea (United Kingdom)
2015-04-20
We study cosmology in the bigravity formulation of the dRGT model where matter couples to both metrics. At linear order in perturbation theory two mass scales emerge: an hard one from the dRGT potential, and an environmental dependent one from the coupling of bigravity with matter. At early time, the dynamics is dictated by the second mass scale which is of order of the Hubble scale. The set of gauge invariant perturbations that couples to matter follow closely the same behaviour as in GR. The remaining perturbations show no issue in the scalar sector, while problems arise in the tensor and vector sectors. During radiation domination, a tensor mode grows power-like at super-horizon scales. More dangerously, the only propagating vector mode features an exponential instability on sub-horizon scales. We discuss the consequences of such instabilities and speculate on possible ways to deal with them.
Visualising Matter and Cosmologies: A Transhistorical Example
Ayala, Lucia
2011-01-01
We propose a connection between the visualisation of cosmic matter and structure formation in the Cartesian tradition and that used by contemporary astrophysics. More precisely, we identify cosmological simulations of large scale structure in the Universe with the system of vortices in Descartes physics. This connection operates at different levels of the images: their representational purpose; the theoretical systems behind their use; and, finally, their function and materiality as visual productions. A skilled use of image analysis is necessary to stress the continuities and peculiarities between different epochs and disciplines.
Rubakov, V A
2014-01-01
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.
Non-linear dark matter collapse under diffusion
Velten, Hermano E S
2014-01-01
Diffusion is one of the physical processes allowed for describing the large scale dark matter dynamics. At the same time, it can be seen as a possible mechanism behind the interacting cosmologies. We study the non-linear spherical "top-hat" collapse of dark matter which undergoes velocity diffusion into a solvent dark energy field. We show constraints on the maximum magnitude allowed for the dark matter diffusion. Our results reinforce previous analysis concerning the linear perturbation theory.
Cosmological Evolution With Interaction Between Dark Energy And Dark Matter
Bolotin, Yu L; Lemets, O A; Yerokhin, D A
2013-01-01
In this review we consider in detail different theoretical topics associated with interaction in the dark sector. We study linear and nonlinear interactions which depend on the dark matter and dark energy densities. We consider a number of different models (including the holographic dark energy and dark energy in a fractal universe) with interacting dark energy (DE) and dark matter (DM), have done a thorough analysis of these models. The main task of this review was not only to give an idea about the modern set of different models of dark energy, but to show how much can be diverse dynamics of the universe in these models. We find that the dynamics of a Universe that contains interaction in the dark sector can differ significantly from the Standard Cosmological Model (SCM).
Cosmological consequences of an adiabatic matter creation process
Nunes, Rafael C
2016-01-01
In this paper we investigate the cosmological consequences of a continuous matter creation associated with the production of particles by the gravitational field acting on the quantum vacuum. To illustrate this, three phenomenological models are considered. An equivalent scalar field description is presented for each models. The effects on the cosmic microwave background power spectrum are analyzed for the first time in the context of adiabatic matter creation cosmology. Further, we introduce a model independent treatment, $Om$, which depends only on the Hubble expansion rate and the cosmological redshift to distinguish any cosmological model from $\\Lambda$CDM by providing a null test for the cosmological constant, meaning that, for any two redshifts $z_1$, $z_2$, $Om (z)$ is same, i.e. $Om (z_1)- Om (z_2)= 0$. Also, this diagnostic can differentiate between several cosmological models by indicating their quintessential/ phantom behavior without knowing the accurate value of the matter density, and the presen...
Cosmological perturbations in massive gravity with doubly coupled matter
Gümrükçüoğlu, A Emir; Mukohyama, Shinji
2014-01-01
We investigate the cosmological perturbations around FLRW solutions to non- linear massive gravity with a new effective coupling to matter proposed recently. Unlike the case with minimal matter coupling, all five degrees of freedom in the gravity sector propagate on generic self-accelerating FLRW backgrounds. We study the stability of the cosmological solutions and put constraints on the parameters of the theory by demanding the correct sign for the kinetic terms for scalar, vector and tensor perturbations.
Cosmological perturbations in massive gravity with doubly coupled matter
Gümrükçüoğlu, A. Emir; Heisenberg, Lavinia; Mukohyama, Shinji
2015-02-01
We investigate the cosmological perturbations around FLRW solutions to non- linear massive gravity with a new effective coupling to matter proposed recently. Unlike the case with minimal matter coupling, all five degrees of freedom in the gravity sector propagate on generic self-accelerating FLRW backgrounds. We study the stability of the cosmological solutions and put constraints on the parameters of the theory by demanding the correct sign for the kinetic terms for scalar, vector and tensor perturbations.
Higher dimensional strange quark matter solutions in self creation cosmology
Şen, R.; Aygün, S.
2016-03-01
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.
Cosmological nonlinear structure formation in full general relativity
Torres, Jose M; Diez-Tejedor, Alberto; Nunez, Dario
2014-01-01
We perform numerical evolutions of cosmological scenarios using a standard general relativistic code in spherical symmetry. We concentrate on two different situations: initial matter distributions that are homogeneous and isotropic, and perturbations to those that respect the spherical symmetry. As matter models we consider the case of a pressureless perfect fluid, i.e. dust, and the case of a real massive scalar field oscillating around the minimum of the potential. Both types of matter have been considered as possible dark matter candidates in the cosmology literature, dust being closely related to the standard cold dark matter paradigm. We confirm that in the linear regime the perturbations associated with these types of matter grow in essentially the same way, the main difference being that in the case of a scalar field the dynamics introduce a cut-off in the power spectrum of the density perturbations at scales comparable with the Compton wavelength of the field. We also follow the evolutions well beyond...
A curiosity about the dust matter in the cosmological context
Ghalee, Amir
2013-01-01
We propose a model for the dust matter in the cosmological context. The model contains a scalar field with a kinetic term non-minimally coupled to gravity. By investigating the background and perturbative equations, it is demonstrated that the scalar field has the same dynamics as the dust matter. We have also considered the cosmological constant in the model. It turns out that the model has not exotic behaviour. Thus, a universe including the scalar field and the cosmological constant, evolves just as the our universe. Moreover, we have added the quadratic term in the action. It is shown that the quadratic term can be ruled out by its consequences.
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.
Bouncing Cosmologies with Dark Matter and Dark Energy
Cai, Yi-Fu; Marcianò, Antonino; Wang, Dong-Gang; Wilson-Ewing, Edward
2017-01-01
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.
Bouncing cosmologies with dark matter and dark energy
Cai, Yi-Fu; Wang, Dong-Gang; Wilson-Ewing, Edward
2016-01-01
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.
Nonlinear stability of cosmological solutions in massive gravity
De Felice, Antonio; Lin, Chunshan; Mukohyama, Shinji
2013-01-01
We investigate nonlinear stability of two classes of cosmological solutions in massive gravity: isotropic Friedmann-Lemaitre-Robertson-Walker (FLRW) solutions and anisotropic FLRW solutions. For this purpose we construct the linear cosmological perturbation theory around axisymmetric Bianchi type--I backgrounds. We then expand the background around the two classes of solutions, which are fixed points of the background evolution equation, and analyze linear perturbations on top of it. This provides a consistent truncation of nonlinear perturbations around these fixed point solutions and allows us to analyze nonlinear stability in a simple way. In particular, it is shown that isotropic FLRW solutions exhibit nonlinear ghost instability. On the other hand, anisotropic FLRW solutions are shown to be ghost-free for a range of parameters and initial conditions.
Parameter information from nonlinear cosmological fields
Watts, A T P
2000-01-01
We develop a general formalism for analysing parameter information from non-Gaussian cosmic fields. The method can be adapted to include the nonlinear effects in galaxy redshift surveys, weak lensing surveys and cosmic velocity field surveys as part of parameter estimation. It can also be used as a test of non-Gaussianity of the Cosmic Microwave Background. Generalising Maximum Likelihood analysis to second-order, we calculate the nonlinear Fisher Information matrix and likelihood surfaces in parameter space. To this order we find that the information content is always increased by including nonlinearity. Our methods are applied to a realistic model of a galaxy redshift survey, including nonlinear evolution, galaxy bias, shot-noise and redshift-space distortions to second-order. We find that including nonlinearities allows all of the degeneracies between parameters to be lifted. Marginalised parameter uncertainties of a few percent will then be obtainable using forthcoming galaxy redshift surveys.
Abundance of Asymmetric Dark Matter in Brane World Cosmology
Abdusattar, Haximjan; Iminniyaz, Hoernisa
2016-09-01
Relic abundance of asymmetric Dark Matter particles in brane world cosmological scenario is investigated in this article. Hubble expansion rate is enhanced in brane world cosmology and it affects the relic abundance of asymmetric Dark Matter particles. We analyze how the relic abundance of asymmetric Dark Matter is changed in this model. We show that in such kind of nonstandard cosmological scenario, indirect detection of asymmetric Dark Matter is possible if the cross section is small enough which let the anti-particle abundance kept in the same amount with the particle. We show the indirect detection signal constraints can be used to such model only when the cross section and the 5-dimensional Planck mass scale are in appropriate values. Supported by the National Natural Science Foundation of China under Grant No. 11365022
Born-Infeld cosmology with scalar Born-Infeld matter
Jana, Soumya
2016-01-01
Cosmology in Eddington-inspired Born-Infeld gravity is investigated using a scalar Born-Infeld field (eg. tachyon condensate) as matter. In this way, both in the gravity and matter sectors we have Born-Infeld-like structures characterised by their actions and via two separate constants, $\\kappa$ and $\\alpha_T^2$ respectively. With a particular choice of the form of $\\dot{\\phi}$ (time derivative of the Born-Infeld scalar), analytical cosmological solutions are found. Thereafter, we explore some of the unique features of the corresponding cosmological spacetimes. For $\\kappa>0$, our solution has a de Sitter-like expansion both at early and late times, with an intermediate deceleration sandwiched between the accelerating phases. On the other hand, when $\\kappa0$ solution, are as good as in $\\Lambda$CDM cosmology. However, the $\\kappa<0$ solution has to be discarded due to the occurrence of a bounce at an unacceptably low redshift.
Born-Infeld cosmology with scalar Born-Infeld matter
Jana, Soumya; Kar, Sayan
2016-09-01
Cosmology in Eddington-inspired Born-Infeld gravity is investigated using a scalar Born-Infeld field (e.g. tachyon condensate) as matter. In this way, both in the gravity and matter sectors we have Born-Infeld-like structures characterized by their actions and via two separate constants, κ and αT2 , respectively. With a particular choice of the form of ϕ ˙ (the time derivative of the Born-Infeld scalar), analytical cosmological solutions are found. Thereafter, we explore some of the unique features of the corresponding cosmological spacetimes. For κ >0 , our solution has a de Sitter-like expansion both at early and late times, with an intermediate deceleration sandwiched between the accelerating phases. On the other hand, when κ 0 solution are as good as in Λ CDM cosmology. However, the κ <0 solution has to be discarded due to the occurrence of a bounce at an unacceptably low redshift.
Of Matter Less Repulsive than a Cosmological Constant
Cornish, N J; Cornish, Neil J.; Starkman, Glenn D.
1998-01-01
The case grows ever stronger that the average density of matter, ordinary and dark, is less than the critical density required for a flat universe. However, most of determinations of the mass density have been dynamical, hence sensitive only to matter which is clustered at or below the scale of the observed dynamical systems. The density may still be critical if there is a dark matter component which is relatively smooth on the scales of galaxies or clusters. Thoughts on this matter have focused on the possibility of an effective cosmological constant or vacuum energy. In this letter we examine an alternative possibility - that there is a second component to the dark matter which has a repulsive self-interaction. We show that given even very weak self-repulsion, this dark matter would remain unclustered. While this repulsive alternative is perhaps aptly named, it is arguably at least as palatable as a cosmological constant.
Cosmological particle-in-cell simulations with ultra-light axion dark matter
Veltmaat, Jan
2016-01-01
We study cosmological structure formation with ultra-light axion dark matter (or "fuzzy dark matter", FDM) using a particle-mesh scheme to account for the quantum pressure arising in the Madelung formulation of the Schr\\"odinger-Poisson equations. Sub-percent level energy conservation and correct linear behavior are demonstrated. Whereas the code gives rise to the same core-halo profiles as direct simulations of the Schr\\"odinger equation, it does not reproduce the detailed interference patterns at the resolution used here. In cosmological simulations with FDM inital conditions, we find a maximum relative difference of O($10\\%$) in the power spectrum near the quantum Jeans length compared to using a standard N-body code with identical initial conditions. This shows that the effect of quantum pressure during nonlinear structure formation cannot be neglected for precision constraints on a dark matter component consisting of ultra-light axions.
Cosmological particle-in-cell simulations with ultralight axion dark matter
Veltmaat, Jan; Niemeyer, Jens C.
2016-12-01
We study cosmological structure formation with ultralight axion dark matter, or "fuzzy dark matter" (FDM), using a particle-mesh scheme to account for the quantum pressure arising in the Madelung formulation of the Schrödinger-Poisson equations. Subpercent-level energy conservation and correct linear behavior are demonstrated. Whereas the code gives rise to the same core-halo profiles as direct simulations of the Schrödinger equation, it does not reproduce the detailed interference patterns. In cosmological simulations with FDM initial conditions, we find a maximum relative difference of O(10%) in the power spectrum near the quantum Jeans length compared to using a standard N -body code with identical initial conditions. This shows that the effect of quantum pressure during nonlinear structure formation cannot be neglected for precision constraints on a dark matter component consisting of ultralight axions.
Cosmology in nonlinear multidimensional gravity and the Casimir effect
Bolokhov, S. V.; Bronnikov, K. A.
2017-01-01
We study the possible cosmological models in Kaluza-Klein-type multidimensional gravity with a curvature-nonlinear Lagrangian and a spherical extra space, taking into account the Casimir energy. First, we find a minimum of the effective potential of extra dimensions, leading to a physically reasonable value of the effective cosmological constant in our 4D space-time. In this model, the huge Casimir energy density is compensated by a fine-tuned contribution of the curvature-nonlinear terms in the original action. Second, we present a viable model with slowly evolving extra dimensions and power-law inflation in our space-time. In both models, the results formulated in Einstein and Jordan frames are compared.
Nungesser, Ernesto
2014-01-01
We show future global non-linear stability of surface symmetric solutions of the Einstein-Vlasov system with a positive cosmological constant. Estimates of higher derivatives of the metric and the matter terms are obtained using an inductive argument. In a recent research monograph Ringstr\\"{o}m shows future non-linear stability of (not necessarily symmetric) solutions of the Einstein-Vlasov system with a non-linear scalar field if certain local estimates on the geometry and the matter terms are fulfilled. We show that these assumptions are satisfied at late times for the case under consideration here which together with Cauchy stability leads to our main conclusion.
A parametrisation of modified gravity on nonlinear cosmological scales
Lombriser, Lucas
2016-11-01
Viable modifications of gravity on cosmological scales predominantly rely on screening mechanisms to recover Einstein's Theory of General Relativity in the Solar System, where it has been well tested. A parametrisation of the effects of such modifications in the spherical collapse model is presented here for the use of modelling the modified nonlinear cosmological structure. The formalism allows an embedding of the different screening mechanisms operating in scalar-tensor theories through large values of the gravitational potential or its first or second derivatives as well as of linear suppression effects or more general transitions between modified and Einstein gravity limits. Each screening or suppression mechanism is parametrised by a time, mass, and environment dependent screening scale, an effective modified gravitational coupling in the fully unscreened limit that can be matched to linear theory, the exponent of a power-law radial profile of the screened coupling, determined by derivatives, symmetries, and potentials in the scalar field equation, and an interpolation rate between the screened and unscreened limits. Along with generalised perturbative methods, the parametrisation may be used to formulate a nonlinear extension to the linear parametrised post-Friedmannian framework to enable generalised tests of gravity with the wealth of observations from the nonlinear cosmological regime.
Non-baryonic dark matter in cosmology
Del Popolo, A.
2013-07-01
This paper is based on lectures given at the IX Mexican School on Gravitation and Mathematical Physics. The lectures (as the paper) were a broad-band review of the current status of non-baryonic dark matter research. I start with a historical overview of the evidences of dark matter existence, then I discuss how dark matter is distributed from small scale to large scale, and I then verge the attention to dark matter nature: dark matter candidates and their detection. I finally discuss some of the limits of the ΛCDM model, with particular emphasis on the small scale problems of the paradigm.
Non-Baryonic Dark Matter in Cosmology
Del Popolo, A
2014-01-01
This paper is a broad-band review of the current status of non-baryonic dark matter research. I start with a historical overview of the evidences of dark matter existence, then I discuss how dark matter is distributed from small scale to large scale, and I then verge the attention to dark matter nature: dark matter candidates and their detection. I finally discuss some of the limits of the $\\Lambda$CDM model, with particular emphasis on the small scale problems of the paradigm.
Quantum Vacuum and a Matter - Antimatter Cosmology
Rothwarf, F; Rothwarf, Frederick; Roy, Sisir
2007-01-01
A model of the universe as proposed by Allen Rothwarf based upon a degenerate Fermion fluid composed of polarizable particle-antiparticle pairs leads to a big bang model of the universe where the velocity of light varies inversely with the square root of cosmological time, t. This model is here extended to predict a decelerating expansion of the universe and to derive the Tully-Fisher law describing the flat rotation curves of spiral galaxies. The estimated critical acceleration parameter, aoR, is compared to the experimental, critical modified Newtonian Dynamics (MOND) cosmological acceleration constant, obtained by fitting a large number of rotation curves. The present estimated value is much closer to the experimental value than that obtained with the other models. This model for aR(t) allows the derivation of the time dependent radius of the universe as a function of red shift Other cosmological parameters such as the velocity of light, Hubble's constant, the Tully-Fisher relation, and the index of refrac...
Evidence for Matter Bounce Cosmology in Low Redshift Observations
Cai, Yi-Fu; Easson, Damien A; Wang, Dong-Gang
2015-01-01
The Matter Bounce scenario allows for a sizable parameter space where cosmological fluctuations originally exit the Hubble radius when the background energy density was small. In this scenario and its extended versions, the low energy degrees of freedom are likely responsible for the statistical properties of the cosmic microwave background (CMB) power spectrum at large length scales. An interesting consequence is that these modes might be observable only at relatively late times. Therefore low redshift observations could provide evidence for, or even falsify, various bouncing models. We provide an example where a recently hinted potential deviation from $\\Lambda$-Cold-Dark-Matter ($\\Lambda$CDM) cosmology results from a dark matter (DM) and dark energy (DE) interaction. The same interaction allows Matter Bounce models to generate a red tilt for the primordial curvature perturbations in corroboration with CMB experiments.
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.
Inflationary cosmology with nonlinear dispersion relations
Zhu, Tao; Cleaver, Gerald; Kirsten, Klaus; Sheng, Qin
2013-01-01
We present a technique, {\\em the uniform asymptotic approximation}, to construct accurate analytical solutions of the linear perturbations of inflation after quantum effects of the early universe are taken into account, for which the dispersion relations generically become nonlinear. We construct explicitly the error bounds associated with the approximations and then study them in detail. With the understanding of the errors and the proper choice of the Liouville transformations of the differential equations of the perturbations, we show that the analytical solutions describe the exact evolution of the linear perturbations extremely well even only to the first-order approximations. As a simple application of the approximate analytical solutions, we calculate the power spectra and indices of scalar and tensor perturbations in the de Sitter background, and find that the amplitudes of the power spectra get modified due to the quantum effects, while the power spectrum indices remain the same as in the linear case...
Flat FRW Cosmologies with Adiabatic Matter Creation Kinematic tests
Lima, J A S
1999-01-01
Some observational consequences of a cosmological scenario driven by adiabatic matter creation are investigated. Exact expressions for the lookback time, age of the universe, luminosity distance, angular diameter, and galaxy number counts redshift relations are derived and their meaning discussed in detail. The expressions of the conventional FRW models are significantly modified and provide a powerful method to limit the parameters of the models.
Bimetric gravity doubly coupled to matter: theory and cosmological implications
Energy Technology Data Exchange (ETDEWEB)
Akrami, Yashar; Koivisto, Tomi S.; Mota, David F.; Sandstad, Marit, E-mail: yashar.akrami@astro.uio.no, E-mail: t.s.koivisto@astro.uio.no, E-mail: d.f.mota@astro.uio.no, E-mail: marit.sandstad@astro.uio.no [Institute of Theoretical Astrophysics, University of Oslo P.O. Box 1029 Blindern, N-0315 Oslo (Norway)
2013-10-01
A ghost-free theory of gravity with two dynamical metrics both coupled to matter is shown to be consistent and viable. Its cosmological implications are studied, and the models, in particular in the context of partially massless gravity, are found to explain the cosmic acceleration without resorting to dark energy.
Interactive Exploration of Cosmological Dark-Matter Simulation Data.
Scherzinger, Aaron; Brix, Tobias; Drees, Dominik; Volker, Andreas; Radkov, Kiril; Santalidis, Niko; Fieguth, Alexander; Hinrichs, Klaus H
2017-01-01
The winning entry of the 2015 IEEE Scientific Visualization Contest, this article describes a visualization tool for cosmological data resulting from dark-matter simulations. The proposed system helps users explore all aspects of the data at once and receive more detailed information about structures of interest at any time. Moreover, novel methods for visualizing and interactively exploring dark-matter halo substructures are proposed.
Non-linear cosmological collapse of quintessence
Rekier, Jeremy; Cordero-Carrion, Isabel
2015-01-01
We present a study of the fully relativistic spherical collapse in presence of quintessence using on Numerical Relativity, following the method proposed by the authors in a previous article [arXiv:1409.3476]. We ascertain the validity of the method by studying the evolution of a spherically symmetric quintessence inhomogeneity on a de Sitter background and we find that it has an impact on the local expansion around the centre of coordinates. We then proceed to compare the results of our method to those of the more largely adopted top-hat model. We find that quintessence inhomogeneities do build up under the effect that matter inhomogeneities have on the local space-time yet remain very small due to the presence of momentum transfer from the over-dense to the background regions. We expect that these might have an even more important role in modified theories of gravitation.
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.
Cosmological perturbations of self-accelerating universe in nonlinear massive gravity
Gumrukcuoglu, A Emir; Mukohyama, Shinji
2011-01-01
We study cosmological perturbations of self-accelerating universe solutions in the recently proposed nonlinear theory of massive gravity, with general matter content. While the broken diffeomorphism invariance implies that there generically are 2 tensor, 2 vector and 2 scalar degrees of freedom in the gravity sector, we find that the scalar and vector degrees have vanishing kinetic terms and nonzero mass terms. Depending on their nonlinear behavior, this indicates either nondynamical nature of these degrees or strong couplings. Assuming the former, we integrate out the 2 vector and 2 scalar degrees of freedom. We then find that in the scalar and vector sectors, gauge-invariant variables constructed from metric and matter perturbations have exactly the same quadratic action as in general relativity. The difference from general relativity arises only in the tensor sector, where the graviton mass modifies the dispersion relation of gravitational waves, with a time-dependent effective mass. This may lead to modif...
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.
Current Status of cosmological models with mixed dark matter
Mikheeva, E V
2000-01-01
An analysis of cosmological mixed dark matter models in spatially flat Friedmann Universe with zero $\\Lambda$-term is presented. We argue that the introduction of cosmic gravity waves helps to satisfy observational constraints. The analysis of models is based on the confrontation with the mass function of clusters of galaxies and the CMB anisotropy. The implication of Press-Schechter formalism allowed to constrain $\\sigma_8=0.52 \\pm 0.01$. This normalisation of the spectrum of density perturbations has been used to calculate numerically the value of the large scale CMB anisotropy and the relative contribution of cosmological gravitational waves, T/S. We found that increasing $\\Omega_\
A parametrisation of modified gravity on nonlinear cosmological scales
Lombriser, Lucas
2016-01-01
Viable modifications of gravity on cosmological scales predominantly rely on screening mechanisms to recover Einstein's Theory of General Relativity in the Solar System, where it has been well tested. A parametrisation of the effects of such modifications in the spherical collapse model is presented here for the use of modelling the modified nonlinear cosmological structure. The formalism allows an embedding of the different screening mechanisms operating in scalar-tensor theories through large values of the gravitational potential or its first or second derivatives as well as of linear suppression effects or more general transitions between modified and Einstein gravity limits. Each screening or suppression mechanism is parametrised by a time, mass, and environment dependent screening scale, an effective modified gravitational coupling in the fully unscreened limit that can be matched to linear theory, the exponent of a power-law radial profile of the screened coupling, determined by derivatives, symmetries,...
Non-Gaussianity vs. non-linearity of cosmological perturbations
Verde, L
2001-01-01
Following the discovery of the CMB, 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 towards 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, non-linear 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 these might not be faithful tr...
Matter power spectra in dynamical-Dark Energy cosmologies
Fedeli, C; Moscardini, L
2011-01-01
(abridged) We used a suite of numerical cosmological simulations in order to investigate the effect of gas cooling and star formation on the large scale matter distribution. The simulations follow the formation of cosmic structures in five different Dark Energy models: the fiducial $\\Lambda$CDM cosmology and four models where the Dark Energy density is allowed to have a non-trivial redshift evolution. For each cosmology we have a control run with dark matter only, in order to allow a direct assessment of the impact of baryonic processes. We found that the power spectra of gas and stars, as well as the total matter power spectrum, are in qualitative agreement with the results of previous works in the framework of the fiducial model, although several quantitative differences exist. We used the halo model in order to investigate the backreaction of gas and stars on the dark matter distribution, finding that it is very well reproduced by increasing the average dark matter halo concentration by 17%, irrespective o...
Covariance and Quantum Cosmology: A Comparison of Two Matter Clocks
Halnon, Theodore; Bojowald, Martin
2017-01-01
In relativity, time is relative between reference frames. However, quantum mechanics requires a specific time coordinate in order to write an evolution equation for wave functions. This difference between the two theories leads to the problem of time in quantum gravity. One method to study quantum relativity is to interpret the dynamics of a matter field as a clock. In order to test the relationship between different reference frames, an isotropic cosmological model with two matter ingredients is introduced. One is given by a scalar field and one by vacuum energy or a cosmological constant. There are two matter fields, and thus two different Hamiltonians are derived from the respective clock rates. Semi-classical solutions are found for these equations and a comparison is made of the physical predictions that they imply. Partial funding from the Ronald E. McNair Postbaccalaureate Achievement Program.
Higgsino Dark Matter and the Cosmological Gravitino Problem
Sinha, Kuver
2012-01-01
We motivate Higgsino dark matter from a solution to the cosmological moduli/gravitino problem. Cosmological moduli/gravitino should be heavy enough to decay before the onset of Big Bang Nucleosynthesis, and this requirement typically forces gauginos to have masses above a TeV in Type IIB compactifications. Higgsinos emerge as the viable sub-TeV dark matter candidates if anomaly and modulus mediated contributions to supersymmetry breaking are both competitive. Obtaining the correct relic density in this mass range forces Higgsinos to be produced non-thermally from the decay of a modulus. We outline constraints arising from indirect and direct detection experiments in this context, as well as theoretical constraints such as the overproduction of dark matter from gravitino decay.
Asymmetric dark matter in braneworld cosmology
Energy Technology Data Exchange (ETDEWEB)
Meehan, Michael T.; Whittingham, Ian B., E-mail: Michael.Meehan@my.jcu.edu.au, E-mail: Ian.Whittingham@jcu.edu.au [School of Engineering and Physical Sciences, James Cook University, Townsville, 4811 Australia (Australia)
2014-06-01
We investigate the effect of a braneworld expansion era on the relic density of asymmetric dark matter. We find that the enhanced expansion rate in the early universe predicted by the Randall-Sundrum II (RSII) model leads to earlier particle freeze-out and an enhanced relic density. This effect has been observed previously by Okada and Seto (2004) for symmetric dark matter models and here we extend their results to the case of asymmetric dark matter. We also discuss the enhanced asymmetric annihilation rate in the braneworld scenario and its implications for indirect detection experiments.
Light Higgsino Dark Matter from Non-thermal Cosmology
Aparicio, Luis; Cicoli, Michele; Muia, Francesco; Quevedo, Fernando
2016-01-01
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 rules out non-thermal higgsinos with masses below 300 GeV. Future indirect dark matter searches from Fermi-LAT and CTA would 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. In the second part of the paper we discuss the motivation of such non-thermal cosmology from the perspe...
Non-linear structure formation in the `Running FLRW' cosmological model
Bibiano, Antonio; Croton, Darren J.
2016-07-01
We present a suite of cosmological N-body simulations describing the `Running Friedmann-Lemaïtre-Robertson-Walker' (R-FLRW) cosmological model. This model is based on quantum field theory in a curved space-time and extends Lambda cold dark matter (ΛCDM) with a time-evolving vacuum density, Λ(z), and time-evolving gravitational Newton's coupling, G(z). In this paper, we review the model and introduce the necessary analytical treatment needed to adapt a reference N-body code. Our resulting simulations represent the first realization of the full growth history of structure in the R-FLRW cosmology into the non-linear regime, and our normalization choice makes them fully consistent with the latest cosmic microwave background data. The post-processing data products also allow, for the first time, an analysis of the properties of the halo and sub-halo populations. We explore the degeneracies of many statistical observables and discuss the steps needed to break them. Furthermore, we provide a quantitative description of the deviations of R-FLRW from ΛCDM, which could be readily exploited by future cosmological observations to test and further constrain the model.
On the non-linear scale of cosmological perturbation theory
Energy Technology Data Exchange (ETDEWEB)
Blas, Diego [Theory Division, CERN, 1211 Geneva (Switzerland); Garny, Mathias; Konstandin, Thomas, E-mail: diego.blas@cern.ch, E-mail: mathias.garny@desy.de, E-mail: Thomas.Konstandin@desy.de [DESY, Notkestr. 85, 22607 Hamburg (Germany)
2013-09-01
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 at any order in perturbation theory. 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.
Cosmological Implications of Trace-Charged Dark Matter
Morgan, Jason P
2016-01-01
Trace charge imbalances can explain puzzling cosmological observations such as the large `missing' fraction of electrons in cosmic rays and their contrast to the charge-neutral solar wind, the extreme energy sources that sustain quasars, galactic jets, and active galactic nuclei, the origin and nature of `dark matter' galaxy haloes, and the apparent acceleration of the expansion of the Universe, obviating $\\Lambda$CDM. When there are $\\sim \
Tachyonic matter cosmology with exponential and hyperbolic potentials
Pourhassan, B.; Naji, J.
In this paper, we consider tachyonic matter in spatially flat Friedmann-Robertson-Walker (FRW) universe, and obtain behavior of some important cosmological parameters for two special cases of potentials. First, we assume the exponential potential and then consider hyperbolic cosine type potential. In both cases, we obtain behavior of the Hubble, deceleration and EoS parameters. Comparison with observational data suggest the model with hyperbolic cosine type scalar field potentials has good model to describe universe.
Wave functions in SUSY cosmological models with matter
Energy Technology Data Exchange (ETDEWEB)
Ortiz, C. [Instituto de Fisica de la Universidad de Guanajuato, A.P. E-143, C.P. 37150, Leon, Guanajuato (Mexico); Rosales, J.J. [Facultad de Ingenieria Mecanica Electrica y Electronica, Universidad de Guanajuato, Prolongacion Tampico 912, Bellavista, Salamanca, Guanajuato (Mexico); Socorro, J. [Instituto de Fisica de la Universidad de Guanajuato, A.P. E-143, C.P. 37150, Leon, Guanajuato (Mexico)]. E-mail: socorro@fisica.ugto.mx; Torres, J. [Instituto de Fisica de la Universidad de Guanajuato, A.P. E-143, C.P. 37150, Leon, Guanajuato (Mexico); Tkach, V.I. [Instituto de Fisica de la Universidad de Guanajuato, A.P. E-143, C.P. 37150, Leon, Guanajuato (Mexico)
2005-06-06
In this work we consider the n=2 supersymmetric superfield approach for the FRW cosmological model and the corresponding term of matter content, perfect fluid with barotropic state equation p={gamma}{rho}. We are able to obtain a normalizable wave function (at zero energy) of the universe. Besides, the mass parameter spectrum is found for the closed FRW case in the Schrodinger picture, being similar to those obtained by other methods, using a black hole system.
Cold Dark Matter Cosmology Conflicts with Fluid Mechanics and Observations
Directory of Open Access Journals (Sweden)
Carl H. Gibson
2008-01-01
Full Text Available Cold dark matter (CDM cosmology based on the Jeans 1902 criterion for gravitational instability gives predictions about the early universe contrary to fluid mechanics and observations. Jeans neglected viscosity, diffusivity, and turbulence: factors that determine gravitational structure formation and contradict small structures (CDM halos forming from non-baryonic dark matter particle candidates. From hydro-gravitational-dynamics (HGD cosmology, viscous-gravitational fragmentation produced supercluster (10^46 kg, cluster, and galaxy-mass (10^42 kg clouds in the primordial plasma with the large fossil density turbulence (3 ×10 ^ -17 kg m ^ -3 of the first fragmentation at 10^12 s, and a protogalaxy linear morphology reflecting maximum stretching on vortex lines of the plasma turbulence at plasma-gas transition at 10^13 s. Gas protogalaxies fragmented into proto-globular-star-cluster mass (10 ^36 kg clumps of protoplanet gas clouds that are now frozen as earth-mass (10^ 24-25 kg Jovian planets of the baryonic dark matter, about 30,000,000 rogue planets per star. Observations contradict the prediction of CDM hierarchical clustering cosmology that massive Population III first stars at 10^16 s existed but support the HGD prediction of gentle formation of small first stars in globular-star-clusters soon after 10^13 s.
Axion dark matter and cosmological parameters.
Erken, O; Sikivie, P; Tam, H; Yang, Q
2012-02-10
We observe that photon cooling after big bang nucleosynthesis but before recombination can remove the conflict between the observed and theoretically predicted value of the primordial abundance of ^{7}Li. Such cooling is ordinarily difficult to achieve. However, the recent realization that dark matter axions form a Bose-Einstein condensate provides a possible mechanism because the much colder axions may reach thermal contact with the photons. This proposal predicts a high effective number of neutrinos as measured by the cosmic microwave anisotropy spectrum.
Doroshkevich, A G; Mikheeva, E V; 10.3367/UFNr.0182.201201a.0003
2012-01-01
We discuss various aspects of the inner structure formation in virialized dark matter (DM) halos that form as primordial density inhomogeneities evolve in the cosmological standard model. The main focus is on the study of central cusps/cores and of the profiles of DM halo rotation curves, problems that reveal disagreements among the theory, numerical simulations, and observations. A method that was developed by the authors to describe equilibrium DM systems is presented, which allows investigating these complex nonlinear structures analytically and relating density distribution profiles within a halo both to the parameters of the initial small-scale inhomogeneity field and to the nonlinear relaxation characteristics of gravitationally compressed matter. It is shown that cosmological random motions of matter `heat up' the DM particles in collapsing halos, suppressing cusp-like density profiles within developing halos, facilitating the formation of DM cores in galaxies, and providing an explanation for the diff...
A survey of dark matter and related topics in cosmology
Young, Bing-Lin
2017-04-01
This article presents an extensive review of the status of the search of the dark matter. The first eight sections are devoted to topics in dark matter and its experimental searches, and the rest to selected topics in astrophysics and cosmology, which are intended to supply some of the needed background for students in particle physics. Sections 9 and 13 are introductory cosmology. The three astrophysical topics, Big Bang nucleosynthesis Section 10, Boltzmann transport equation and freeze out of massive particles Section 11, and CMB anisotropy Section 12 can all be studied in analytical approaches when reasonable approximations are made. Their original analytically forms, to which this article follows very closely, were given by particle physicists. Dark matter is an evolving subject requiring timely update to stay current. Hence a review of such a subject matter would undoubtedly have something wanting when it appears in print. It is hoped that this review can form a humble basis for those graduate students who would like to pursue the subject of dark matter. The reader can use the extensive table of contents to see in some details the materials covered in the article.
Vittorio, Nicola
2017-01-01
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.
Simulating nonlinear cosmological structure formation with massive neutrinos
Banerjee, Arka
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.
Dark matter relic density in Gauss-Bonnet braneworld cosmology
Meehan, Michael T
2014-01-01
The relic density of symmetric and asymmetric dark matter in the Gauss-Bonnet braneworld cosmology is investigated. The reduced expansion rate in this scenario delays particle freeze-out, leading to relic abundances which are suppressed by up to $\\mathcal{O}(10^{-3})$. In this case the annihilation cross section must be reduced by up to two orders of magnitude below the canonical value $\\langle\\sigma v\\rangle \\approx 2\\times 10^{-26}$ cm$^3$s$^{-1}$ to reconcile the predicted dark matter density with observation. We use the latest observational bound $\\Omega_{DM}h^2 = 0.1187 \\pm 0.0017$ to constrain the various model parameters and discuss the implications for direct/indirect dark matter detection experiments as well as dark matter particle models.
Interacting Scalar Radiation and Dark Matter in Cosmology
Tang, Yong
2016-01-01
We investigate possible cosmological effects of interacting scalar radiation and dark matter. After its decoupling, scalar radiation can stream freely as neutrinos or self-interact strongly as perfect fluid, highly depending on the magnitude of its self-couplings. We obtain the general and novel structure for self-scattering rate and compare it with the expansion rate of our Universe. If its trilinear/cubic coupling is non-zero, scalar radiation can be eventually treated as perfect fluid. Possible effects on CMB are also discussed. When this scalar also mediates interaction among dark matter particles, the linear matter power spectrum for large scale structure can be modified differently from other models. We propose to use Debye shielding to avoid the singularity appearing in the scattering between scalar radiation and dark matter.
Thermal Fluctuations of Dark Matter in Bouncing Cosmology
Li, Changhong
2015-01-01
We investigate the statistical nature of the dark matter particles produced in bouncing cosmology, including its total energy and the evolution of its sub-horizon and super-horizon thermal fluctuations. We find that the super-horizon modes of the dark matter thermal perturbations are developing during the generic bouncing universe scenario--in contrast to the case that no significant super-horizon thermal perturbations of dark matter appear in the inflation scenario such as WIMP(-less) miracles. By explicitly deriving and solving the equation of motion of super-horizon mode, we fully determine the evolution of thermal perturbation of dark matter in a generic bouncing background. And we also prove that the evolution of super-horizon modes is stable and will not ruin out the background evolution till the Planck scale.
Interacting scalar radiation and dark matter in cosmology
Energy Technology Data Exchange (ETDEWEB)
Tang, Yong, E-mail: ytang@kias.re.kr
2016-06-10
We investigate possible cosmological effects of interacting scalar radiation and dark matter. After its decoupling, scalar radiation can stream freely as neutrinos or self-interact strongly as perfect fluid, highly depending on the magnitude of its self-couplings. We obtain the general and novel structure for self-scattering rate and compare it with the expansion rate of our Universe. If its trilinear/cubic coupling is non-zero, scalar radiation can be eventually treated as perfect fluid. Possible effects on CMB are also discussed. When this scalar also mediates interaction among dark matter particles, the linear matter power spectrum for large scale structure can be modified differently from other models. We propose to use Debye shielding to avoid the singularity appearing in the scattering between scalar radiation and dark matter.
Thermal fluctuations of dark matter in bouncing cosmology
Li, Changhong
2016-09-01
We investigate the statistical nature of the dark matter particles produced in bouncing cosmology, especially, the evolution of its thermal fluctuations. By explicitly deriving and solving the equation of motion of super-horizon mode, we fully determine the evolution of thermal perturbation of dark matter in a generic bouncing background. And we also show that the evolution of super-horizon modes is stable and will not ruin the background evolution of a generic bouncing universe till the Planck scale. Given no super-horizon thermal perturbation of dark matter appears in standard inflation scenario such as WIMP(-less) miracles, such super-horizon thermal perturbation of dark matter generated during the generic bouncing universe scenario may be significant for testing and distinguishing these two scenario in near future.
PkANN I: Non-Linear Matter Power Spectrum Estimation through Artificial Neural Networks
Agarwal, Shankar; Feldman, Hume A; Lahav, Ofer; Thomas, Shaun A
2012-01-01
We investigate a new approach to confront small-scale non-linearities in the power spectrum of matter fluctuations. This ever-present and pernicious uncertainty is often the Achilles' heel in cosmological studies and must be reduced if we are to see the advent of precision cosmology in the late-time Universe. We show that an optimally trained Artificial Neural Network (ANN), when presented with a set of cosmological parameters ($\\Omega_{\\rm m} h^2, \\Omega_{\\rm b} h^2, n_s, w_0, \\sigma_8, \\sum m_\
Cosmology and Dark Matter at the LHC
Arnowitt, Richard; Aurisano, Adam; Dutta, Bhaskar; Kamon, Teruki; Kolev, Nikolay; Simeon, Paul; Toback, David; Wagner, Peter
2007-08-01
We examine the question of whether neutralinos produced at the LHC can be shown to be the particles making up the astronomically observed dark matter. If the WIMP alllowed region lies in the SUGRA coannihilation region, then a strong signal for this would be the unexpected near degeneracy of the stau and neutralino i.e., a mass difference ΔM ≃ (5 - 15) GeV. For the mSUGRA model we show such a small mass difference can be measured at the LHC using the signal 3τ + jet + E^miss_{T}. Two observables, opposite sign minus like sign pairs and the peak of the ττ mass distribution allows the simultaneous determination of ΔM to 15% and the gluino mass M_{tilde {g}} to be 6% at the benchmark point of M_{tilde{g}} = 850 GeV, A0 = 0, μ > 0 with 30 fb-1. With 10 fb-1, ΔM can be determined to 22% and one can probe the parameter space up to m1/2 = 700 GeV with 100 fb-1.
Cosmology and Dark Matter at the LHC
Arnowitt, R; Dutta, B; Kamon, T; Kolev, N; Simeon, P; Toback, D; Wagner, P; Arnowitt, Richard; Aurisano, Adam; Dutta, Bhaskar; Kamon, Teruki; Kolev, Nikolay; Simeon, Paul; Toback, David; Wagner, Peter
2007-01-01
We examine the question of whether neutralinos produced at the LHC can be shown to be the particles making up the astronomically observed dark matter. If the WIMP alllowed region lies in the SUGRA coannihilation region, then a strong signal for this would be the unexpected near degeneracy of the stau and neutralino i.e., a mass difference \\Delta M\\simeq (5-15) GeV. For the mSUGRA model we show such a small mass difference can be measured at the LHC using the signal 3\\tau+jet+E_T^{\\rm miss}. Two observables, opposite sign minus like sign pairs and the peak of the \\tau\\tau mass distribution allows the simultaneous determination of \\Delta M to 15% and the gluino mass M_{\\tilde g} to be 6% at the benchmark point of M_{\\tilde g}=850 GeV, A_0=0, \\mu>0 with 30 fb^{-1}. With 10 fb^{-1}, \\Delta M can be determined to 22% and one can probe the parameter space up to m_{1/2}=700 GeV with 100 fb^{-1}.
A Solvable Model in Two-Dimensional Gravity Coupled to a Nonlinear Matter Field
Institute of Scientific and Technical Information of China (English)
YAN Jun; WANG Shun-Jin; TAO Bi-You
2001-01-01
The two-dimensional gravity model with a coupling constant k = 4 and a vanishing cosmological constant coupled to a nonlinear matter field is investigated. We found that the classical equations of motion are exactly solvable and the static solutions of the induced metric and scalar curvature can be obtained analytically. These solutions may be used to describe the naked singularity at the origin.``
Fluid Mechanics Explains Cosmology, Dark Matter, Dark Energy, and Life
Gibson, Carl H
2012-01-01
Observations of the interstellar medium by the Herschel, Planck etc. infrared satellites throw doubt on standard {\\Lambda}CDMHC cosmological processes to form gravitational structures. According to the Hydro-Gravitational-Dynamics (HGD) cosmology of Gibson (1996), and the quasar microlensing observations of Schild (1996), the dark matter of galaxies consists of Proto-Globular-star-Cluster (PGC) clumps of Earth-mass primordial gas planets in metastable equilibrium since PGCs began star production at 0.3 Myr by planet mergers. Dark energy and the accelerating expansion of the universe inferred from SuperNovae Ia are systematic dimming errors produced as frozen gas dark matter planets evaporate to form stars. Collisionless cold dark matter that clumps and hierarchically clusters does not exist. Clumps of PGCs began diffusion from the Milky Way Proto-Galaxy upon freezing at 14 Myr to give the Magellanic Clouds and the faint dwarf galaxies of the 10^22 m diameter baryonic dark matter Galaxy halo. The first stars p...
Inclusion of matter in inhomogeneous loop quantum cosmology
Blas, Daniel Martín-de; Marugán, Guillermo A Mena; 10.1063/1.4734461
2013-01-01
We study the hybrid quantization of the linearly polarized Gowdy $T^3$ model with a massless scalar field with the same symmetries as the metric. For simplicity, we quantize its restriction to the model with local rotational symmetry. Using this hybrid approach, the homogeneous degrees of freedom of the geometry are quantized \\`a la loop, leading to the resolution of the cosmological singularity. A Fock quantization is employed both for the matter and the 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, providing a perfect scenario to study the quantum back-reaction of the inhomogeneities on the polymeric homogeneous and isotropic background.
Cosmological Consequences of Dark Matter Interactions and Vacuum Fluctuations
Boddy, Kimberly K.
This thesis is divided into two parts: interacting dark matter and fluctuations in cosmology. There is an incongruence between the properties that dark matter is expected to possess between the early universe and the late universe. Weakly-interacting dark matter yields the observed dark matter relic density and is consistent with large-scale structure formation; however, there is strong astrophysical evidence in favor of the idea that dark matter has large self-interactions. The first part of this thesis presents two models in which the nature of dark matter fundamentally changes as the universe evolves. In the first model, the dark matter mass and couplings depend on the value of a chameleonic scalar field that changes as the universe expands. In the second model, dark matter is charged under a hidden SU(N) gauge group and eventually undergoes confinement. These models introduce very different mechanisms to explain the separation between the physics relevant for freezeout and for small-scale dynamics. As the universe continues to evolve, it will asymptote to a de Sitter vacuum phase. Since there is a finite temperature associated with de Sitter space, the universe is typically treated as a thermal system, subject to rare thermal fluctuations, such as Boltzmann brains. The second part of this thesis begins by attempting to escape this unacceptable situation within the context of known physics: vacuum instability induced by the Higgs field. The vacuum decay rate competes with the production rate of Boltzmann brains, and the cosmological measures that have a sufficiently low occurrence of Boltzmann brains are given more credence. Upon further investigation, however, there are certain situations in which de Sitter space settles into a quiescent vacuum with no fluctuations. This reasoning not only provides an escape from the Boltzmann brain problem, but it also implies that vacuum states do not uptunnel to higher-energy vacua and that perturbations do not decohere
The effects of galaxy formation on the matter power spectrum: A challenge for precision cosmology
van Daalen, Marcel P; Booth, C M; Vecchia, Claudio Dalla
2011-01-01
Upcoming weak lensing surveys, such as LSST, EUCLID, and WFIRST, aim to measure the matter power spectrum with unprecedented accuracy. In order to fully exploit these observations, models are needed that, given a set of cosmological parameters, can predict the non-linear matter power spectrum at the level of 1% or better for scales corresponding to comoving wave numbers 0.170 h/Mpc. Therefore, baryons, and particularly AGN feedback, cannot be ignored in theoretical power spectra for k>0.3 h/Mpc. It will thus be necessary to improve our understanding of feedback processes in galaxy formation, or at least to constrain them through auxiliary observations, before we can fulfil the goals of upcoming weak lensing surveys.
Investigation of dark matter-dark energy interaction cosmological model
Wang, J S
2014-01-01
In this paper, we test the dark matter-dark energy interacting cosmological model with a dynamic equation of state $w_{DE}(z)=w_{0}+w_{1}z/(1+z)$, using type Ia supernovae (SNe Ia), Hubble parameter data, baryonic acoustic oscillation (BAO) measurements, and the cosmic microwave background (CMB) observation. This interacting cosmological model has not been studied before. The best-fitted parameters with $1 \\sigma$ uncertainties are $\\delta=-0.022 \\pm 0.006$, $\\Omega_{DM}^{0}=0.213 \\pm 0.008$, $w_0 =-1.210 \\pm 0.033$ and $w_1=0.872 \\pm 0.072$ with $\\chi^2_{min}/dof = 0.990$. At the $1 \\sigma$ confidence level, we find $\\delta<0$, which means that the energy transfer prefers from dark matter to dark energy. We also find that the SNe Ia are in tension with the combination of CMB, BAO and Hubble parameter data. The evolution of $\\rho_{DM}/\\rho_{DE}$ indicates that this interacting model is a good approach to solve the coincidence problem, because the $\\rho_{DE}$ decrease with scale factor $a$. The transition r...
Challenges in Cosmology from the Big Bang to Dark Energy, Dark Matter and Galaxy Formation
Silk, Joseph
2016-01-01
I review the current status of Big Bang Cosmology, with emphasis on current issues in dark matter, dark energy, and galaxy formation. These topics motivate many of the current goals of experimental cosmology which range from targeting the nature of dark energy and dark matter to probing the epoch of the first stars and galaxies.
What does the N-point function hierarchy of the cosmological matter density field really measure?
Carron, J.; Szapudi, I.
2017-08-01
The cosmological dark matter field is not completely described by its hierarchy of N-point functions, a non-perturbative effect with the consequence that only part of the theory can be probed with the hierarchy. We give here an exact characterization of the joint information of the hierarchy within the lognormal field. The lognormal field is the archetypal example of a field where this effect occurs, and, at the same time, one of the few tractable and insightful available models to specify fully the statistical properties of the evolved matter density field beyond the perturbative regime. Non-linear growth in the Universe in that model is set letting the log-density field probability density functional evolve keeping its Gaussian shape, according to the diffusion equation in Euclidean space. We show that the hierarchy probes a different evolution equation, the diffusion equation defined not in Euclidean space but on the compact torus, with uniformity as the long-term solution. The extraction of the hierarchy of correlators can be recast in the form of a non-linear transformation applied to the field, 'wrapping', undergoing a sharp transition towards complete disorder in the deeply non-linear regime, where all memory of the initial conditions is lost.
Quantum cosmology with matter in scalar-tensor theory
Lee, S.; Lim, H.
2016-11-01
The cosmological application of the low energy effective action of string theory with perfect fluid type matter (satisfying p=γ ρ ) is reconsidered. First, its isotropic and anisotropic spacetime cosmological solutions are obtained for general γ . The scale factor duality is applied and checked for our model as well as in the presence of γ of which possible extension to nonvanishing γ is pioneered before. The asymptotic behavior of the solutions is investigated because of the complexity of the solutions. Second, as a quantization, we apply the canonical quantization and the corresponding Wheeler-De Witt equation is constructed for this scalar-tensor theory. By solving the Wheeler-De Witt equation the wave function is found for general value of γ . On the basis of its wave function, the tunneling rate turns out to be just the ratio of norms of the wave function for pre- and post-big-bang phases. This result shows that the rate grows as γ gets value close to a specific value. This resolves the undetermined value for the behavior of the scale factors.
Nonlinear Light-Matter Interactions in Metamaterials
O'Brien, Kevin Patrick
Metamaterials possess extraordinary linear optical properties never observed in natural materials such as a negative refractive index, enabling exciting applications such as super resolution imaging and cloaking. In this thesis, we explore the equally extraordinary nonlinear properties of metamaterials. Nonlinear optics, the study of light-matter interactions where the optical fields are strong enough to change material properties, has fundamental importance to physics, chemistry, and material science as a non-destructive probe of material properties and has important technological applications such as entangled photon generation and frequency conversion. Due to their ability to manipulate both linear and nonlinear light matter interactions through sub-wavelength structuring, metamaterials are a promising direction for both fundamental and applied nonlinear optics research. We perform the first experiments on nonlinear propagation in bulk zero and negative index optical metamaterials and demonstrate that a zero index material can phase match four wave mixing processes in ways not possible in finite index materials. In addition, we demonstrate the ability of nonlinear scattering theory to describe the geometry dependence of second and third harmonic generation in plasmonic nanostructures. As an application of nonlinear metamaterials, we propose a phase matching technique called "resonant phase matching" to increase the gain and bandwidth of Josephson junction traveling wave parametric amplifiers. With collaborators, we demonstrate a best in class amplifier for superconducting qubit readout--over 20 dB gain with near quantum limited noise performance with a bandwidth and dynamic range an order of magnitude larger than alternative devices. In conclusion, we have demonstrated several ways in which nonlinear metamaterials surpass their natural counterparts. We look forward to the future of the field where nonlinear and quantum metamaterials will enable further new
Spherical collapse, formation hysteresis and the deeply non-linear cosmological power spectrum
Mead, A. J.
2016-09-01
I examine differences in non-linear structure formation between cosmological models that share a z = 0 linear power spectrum in both shape and amplitude, but that differ via their growth history. N-body simulations of these models display an approximately identical large-scale-structure skeleton, but reveal deeply non-linear differences in the demographics and properties of haloes. I investigate to what extent the spherical-collapse model can help in understanding these differences, in both real and redshift space. I discuss how this is difficult to do if one attempts to identify haloes directly, because in that case one is subject to the vagaries of halo finding algorithms. However, I demonstrate that the halo model of structure formation provides an accurate non-linear response in the power spectrum, but only if results from spherical collapse that include formation hysteresis are properly incorporated. I comment on how this fact can be used to provide per cent level accurate matter power spectrum predictions for dark energy models for k ≤ 5 hMpc-1 by using the halo model as a correction to accurate ΛCDM simulations. In the appendix I provide some fitting functions for the linear-collapse threshold (δc) and virialized overdensity (Δv) that are valid for a wide range of dark energy models. I also make my spherical-collapse code available at https://github.com/alexander-mead/collapse.
Spherical collapse, formation hysteresis and the deeply non-linear cosmological power spectrum
Mead, Alexander
2016-01-01
I examine differences in non-linear structure formation between cosmological models that share a $z=0$ linear power spectrum in both shape and amplitude, but that differ via their growth history. $N$-body simulations of these models display an approximately identical large-scale-structure skeleton, but reveal deeply non-linear differences in the demographics and properties of haloes. I investigate to what extent the spherical-collapse model can help in understanding these differences, in both real and redshift space. I discuss how this is difficult to do if one attempts to identify haloes directly, because in that case one is subject to the vagaries of halo finding algorithms. However, I demonstrate that the halo model of structure formation provides an accurate non-linear response in the power spectrum, but only if results from spherical collapse that include formation hysteresis are properly incorporated. I comment on how this fact can be used to provide per cent level accurate matter power spectrum predict...
Spherical collapse, formation hysteresis and the deeply non-linear cosmological power spectrum
Mead, A. J.
2017-01-01
I examine differences in non-linear structure formation between cosmological models that share a z = 0 linear power spectrum in both shape and amplitude, but that differ via their growth history. N-body simulations of these models display an approximately identical large-scale-structure skeleton, but reveal deeply non-linear differences in the demographics and properties of haloes. I investigate to what extent the spherical-collapse model can help in understanding these differences, in both real and redshift space. I discuss how this is difficult to do if one attempts to identify haloes directly, because in that case one is subject to the vagaries of halo-finding algorithms. However, I demonstrate that the halo model of structure formation provides an accurate non-linear response in the power spectrum, but only if results from spherical collapse that include formation hysteresis are properly incorporated. I comment on how this fact can be used to provide per cent level accurate matter power-spectrum predictions for dark energy models for k ≤ 5 h Mpc-1 by using the halo model as a correction to accurate ΛCDM simulations. In the Appendix, I provide some fitting functions for the linear-collapse threshold (δc) and virialized overdensity (Δv) that are valid for a wide range of dark energy models. I also make my spherical-collapse code available at https://github.com/alexander-mead/collapse.
Reionizing the Universe in Warm Dark Matter cosmologies
Dayal, Pratika; Bromm, Volker; Pacucci, Fabio
2015-01-01
We compare model results from our semi-analytic merger tree based framework for high-redshift ($z \\simeq 5-20$) galaxy formation against reionization indicators including the Planck electron scattering optical depth ($\\tau_{es}$) and the ionizing photon emissivity ($\\dot n_{ion}$) to constrain the particle mass of Warm Dark Matter (WDM). Our framework traces the Dark Matter (DM) and baryonic assembly of galaxies in 4 DM cosmologies: Cold Dark Matter (CDM) and WDM with a particle mass of $m_x = 2.25,3$ and 5 keV. It includes all the key processes of star formation, supernova feedback, the merger/accretion/ejection driven evolution of gas and stellar mass, and the effect of the ultra-violet background (UVB) created during reionization in photo-evaporating the gas content of galaxies in halos with $M_h \\leq 10^9 M_\\odot$. We show that current Planck $\\tau_{es}$ values rule out $m_x \\leq 2.5$ keV WDM, even in the physically unlikely scenario that all ionizing photons produced by these galaxies escape and contribu...
Spectral Gamma-ray Signatures of Cosmological Dark Matter Annihilation
Bergström, L; Ullio, P; Bergstrom, Lars; Edsjo, Joakim; Ullio, Piero
2001-01-01
We propose a new signature for weakly interacting massive particle (WIMP) dark matter, a spectral feature in the diffuse extragalactic gamma-ray radiation. This feature, a sudden drop of the gamma-ray intensity at an energy corresponding to the WIMP mass, comes from the asymmetric distortion of the line due to WIMP annihilation into two gamma-rays caused by the cosmological redshift. Unlike other proposed searches for a line signal, this method is not very sensitive to the exact dark matter density distribution in halos and subhalos. The only requirement is that the mass distribution of substructure on small scales follows approximately the Press-Schechter law, and that smaller halos are on the average denser than large halos, which is a generic outcome of N-body simulations of Cold Dark Matter, and which has observational support. The upcoming Gamma-ray Large Area Space Telescope (GLAST) will be eminently suited to search for these spectral features. For numerical examples, we use rates computed for supersym...
Nonlinear clustering during the BEC dark matter phase transition
Energy Technology Data Exchange (ETDEWEB)
Freitas, Rodolfo C. de, E-mail: rodolfo.camargo@pq.cnpq.br [Universidade Federal do Espírito Santo, Av. Fernando Ferrari, Goiabeiras, Vitória (Brazil); Instituto Federal de Educação, Ciência e Tecnologia do Espírito Santo, Avenida Vitória 1729, Jucutuquara, Vitória (Brazil); Velten, Hermano, E-mail: velten@pq.cnpq.br [Universidade Federal do Espírito Santo, Av. Fernando Ferrari, Goiabeiras, Vitória (Brazil); UMR 7332, CPT, Aix Marseille Université, 13288, Marseille (France)
2015-12-16
Spherical collapse of the Bose–Einstein condensate (BEC) dark matter model is studied in the Thomas–Fermi approximation. The evolution of the overdensity of the collapsed region and its expansion rate are calculated for two scenarios. We consider the case of a sharp phase transition (which happens when the critical temperature is reached) from the normal dark matter state to the condensate one and the case of a smooth first order phase transition where there is a continuous conversion of “normal” dark matter to the BEC phase. We present numerical results for the physics of the collapse for a wide range of the model’s space parameter, i.e. the mass of the scalar particle m{sub χ} and the scattering length l{sub s}. We show the dependence of the transition redshift on m{sub χ} and l{sub s}. Since small scales collapse earlier and eventually before the BEC phase transition, the evolution of collapsing halos in this limit is indeed the same in both the CDM and the BEC models. Differences are expected to appear only on the largest astrophysical scales. However, we argue that the BEC model is almost indistinguishable from the usual dark matter scenario concerning the evolution of nonlinear perturbations above typical clusters scales, i.e., ≳10{sup 14}M{sub ⊙}. This provides an analytical confirmation for recent results from cosmological numerical simulations (Schive et al., Nat Phys 10:496, 2014)
Cosmological aspects of a unified dark energy and dust dark matter mode
Staicova, Denitsa
2016-01-01
Recently, a model of modified gravity plus single scalar field model was proposed, in which the scalar couples both to the standard Riemannian volume form given by the square root of the determinant of the Riemannian metric, as well as to another non-Riemannian volume form given in terms of an auxiliary maximal rank antisymmetric tensor gauge field. This model provides an exact unified description of both dark energy (via dynamically generated cosmological constant) and dark matter (as a "dust" fluid due to a hidden nonlinear Noether symmetry). In this paper we test the model against Supernovae type Ia experimental data and investigate the future Universe evolution which follows from it. Our results show that this model has very interesting features allowing various scenarios of Universe evolution and in the same time perfectly fits contemporary observational data. It can describe exponentially expanding or finite expanding Universe and moreover, a Universe with phase transition of first kind. The phase trans...
Redshift remapping and cosmic acceleration in dark-matter-dominated cosmological models
Wojtak, Radosław
2016-01-01
The standard relation between the cosmological redshift and cosmic scale factor underlies cosmological inference from virtually all kinds of cosmological observations, leading to the emergence of the LambdaCDM cosmological model. This relation is not a fundamental theory and thus observational determination of this function (redshift remapping) should be regarded as an insightful alternative to holding its standard form in analyses of cosmological data. Here we present non-parametric reconstructions of redshift remapping in dark-matter-dominated models and constraints on cosmological parameters from a joint analysis of all primary cosmological probes including the local measurement of the Hubble constant, Type Ia supernovae, baryonic acoustic oscillations (BAO), Planck observations of the cosmic microwave background (CMB) radiation (temperature power spectrum) and cosmic chronometers. The reconstructed redshift remapping points to an additional boost of redshift operating in late epoch of cosmic evolution, bu...
Reionization and Galaxy Formation in Warm Dark Matter Cosmologies
Dayal, Pratika; Choudhury, Tirthankar Roy; Bromm, Volker; Pacucci, Fabio
2017-02-01
We compare model results from a semi-analytic (merger-tree based) framework for high-redshift (z ≃ 5-20) galaxy formation against reionization indicators, including the Planck electron scattering optical depth (τ es) and the ionizing photon emissivity ({\\dot{n}}{ion}), to shed light on the reionization history and sources in Cold (CDM) and Warm Dark Matter (WDM; particle masses of {m}x = 1.5, 3, and 5 keV) cosmologies. This model includes all of the key processes of star formation, supernova feedback, the merger/accretion/ejection driven evolution of gas and stellar mass and the effect of the ultra-violet background (UVB), created during reionization, in photo-evaporating the gas content of galaxies in halos with M h ≲ 109 {M}⊙ . We find that the delay in the start of reionization in light (1.5 keV) WDM models can be compensated by a steeper redshift evolution of the ionizing photon escape fraction and a faster mass assembly, resulting in reionization ending at comparable redshifts (z ≃ 5.5) in all the dark matter models considered. We find that the bulk of the reionization photons come from galaxies with a halo mass of M h ≲ 109 {M}⊙ and a UV magnitude of -15 ≲ M UV ≲ -10 in CDM. The progressive suppression of low-mass halos with decreasing {m}x leads to a shift in the “reionization” population to larger halo masses of M h ≳ 109 {M}⊙ and -17 ≲ M UV ≲ -13 for 1.5 keV WDM. We find that current observations of τ es and the ultra violet luminosity function are equally compatible with all the (cold and warm) dark matter models considered in this work. Quantifying the impact of the UVB on galaxy observables (luminosity functions, stellar mass densities, and stellar to halo mass ratios) for different DM models, we propose that global indicators including the redshift evolution of the stellar mass density and the stellar mass-halo mass relation, observable with the James Webb Space Telescope, can be used to distinguish between CDM and WDM (1
Anisotropic Open Cosmological Models of Spin Matter with Magnetic Moment
Institute of Scientific and Technical Information of China (English)
SHENLi－ming; SUNNai－jiang; 等
2001-01-01
We have derived a set of field equations for a Weyssenhoff spin fluid including magnetic interacton among the spinning particles prevailling in spatially homogeneous,but anisotropically cosmological models of Bianchi type V based on Einstein-Cartan theory.We analyze the field equations in three different equations of states specified by p=1(1/3)ρand p=0,The analytical solutions found are non-singular provided that the combined energy arising from matter spin and magnetic interaction among particles overcomes the anisotropy energy in the Universe,We have also deduced that the minimum particle numers for the radiation(p=(1/3)ρ) and matter(p=0) epochs are 1088 and 10108 respectively.the minimum particle number for the state p=ρ is 1096,leading to the conclusion that we must consider the existence of neutrinos and other creation of particles and anti-particles under torsion and strong gravitational field in the early Universe.
Strong cosmic censorship for T^2-symmetric cosmological spacetimes with collisionless matter
Dafermos, M; Dafermos, Mihalis; Rendall, Alan D.
2006-01-01
We prove strong cosmic censorship for T^2-symmetric cosmological spacetimes (with spatial topology T^3 and vanishing cosmological constant Lambda) with collisionless matter. Gowdy symmetric spacetimes constitute a special case. The formulation of the conjecture is in terms of generic C^2-inextendibility of the metric. Our argument exploits a rigidity property of Cauchy horizons, inherited from Killing fields.
Shapiro, Paul R.; Mao, Yi; Iliev, Ilian T.; Mellema, Garrelt; Datta, Kanan K.; Ahn, Kyungjin; Koda, Jun
2012-01-01
The 21cm 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 ...
The universe dynamics in the tachyon cosmology with non-minimal coupling to matter
Farajollahi, H; Fadakar, G F
2011-01-01
Recently, the tachyon cosmology has been represented as dark energy model to support the current acceleration of the universe without phantom crossing. In this paper, we study the dynamics of the tachyon cosmology in which the field plays the role of tachyon field and also non--minimally coupled to the matter lagrangian. The model shows current universe acceleration and also phantom crossing in the future. Two cosmological tests are also performed to validate the model; the difference in the distance modulus and the model independent Cosmological Redshift Drift (CRD) test.
String Cosmological Solutions with O(d, d) Duality Symmetry and Matter Coupling
Institute of Scientific and Technical Information of China (English)
LI Bao-Lin; YAN Jun
2013-01-01
The duality properties of string cosmology model with negative energy matter are investigated by means of renormalization group equation,the cosmological solutions with exotic matter coupling are obtained in D =d + 1dimensional space-time.These inflation-power solutions can describe accelerated and decelerated process in the early universe,and the duality solutions can be generated through O(d,d) transformations.
Dark matter relic density in Gauss-Bonnet braneworld cosmology
Energy Technology Data Exchange (ETDEWEB)
Meehan, Michael T.; Whittingham, Ian B., E-mail: Michael.Meehan@my.jcu.edu.au, E-mail: Ian.Whittingham@jcu.edu.au [College of Science, Technology and Engineering, James Cook University, 1 James Cook Dr., Townsville 4811 (Australia)
2014-12-01
The relic density of symmetric and asymmetric dark matter in a Gauss-Bonnet (GB) modified Randall-Sundrum (RS) type II braneworld cosmology is investigated. The existing study of symmetric dark matter in a GB braneworld (Okada and Okada, 2009) found that the expansion rate was reduced compared to that in standard General Relativity (GR), thereby delaying particle freeze-out and resulting in relic abundances which are suppressed by up to O(10{sup −2}). This is in direct contrast to the behaviour observed in RS braneworlds where the expansion rate is enhanced and the final relic abundance boosted. However, this finding that relic abundances are suppressed in a GB braneworld is based upon a highly contrived situation in which the GB era evolves directly into a standard GR era, rather than passing through a RS era as is the general situation. This collapse of the RS era requires equating the mass scale m{sub α} of the GB modification and the mass scale m{sub σ} of the brane tension. However, if the GB contribution is to be considered as the lowest order correction from string theory to the RS action, we would expect m{sub α} > m{sub σ}. We investigate the effect upon the relic abundance of choosing more realistic values for the ratio R{sub m} ≡ m{sub α}/m{sub σ} and find that the relic abundance can be either enhanced or suppressed by more than two orders of magnitude. However, suppression only occurs for a small range of parameter choices and, overwhelmingly, the predominant situation is that of enhancement as we recover the usual Randall-Sundrum type behaviour in the limit R{sub m} >> 1. We use the latest observational bound Ω{sub DM}h{sup 2} = 0.1187 ± 0.0017 to constrain the various model parameters and briefly discuss the implications for direct/indirect dark matter detection experiments as well as dark matter particle models.
Erasing Dark Matter Cusps in Cosmological Galactic Halos with Baryons
Romano-Diaz, Emilio; Hoffman, Yehuda; Heller, Clayton
2008-01-01
We study the central dark matter (DM) cusp evolution in cosmological galactic halos. Models with and without baryons (baryons+DM, hereafter BDM model, and pure DM, PDM model, respectively) are advanced from identical initial conditions. The DM cusp properties are contrasted by a direct comparison of pure DM and baryonic models. We find a divergent evolution between the PDM and BDM models within the inner ~10 kpc region. The PDM model forms a R^{-1} cusp as expected, while the DM in the BDM model forms a larger isothermal cusp R^{-2} instead. The isothermal cusp is stable until z~1 when it gradually levels off. This leveling proceeds from inside out and the final density slope is shallower than -1 within the central 3 kpc (i.e., expected size of the R^{-1} cusp), tending to a flat core within ~2 kpc. This effect cannot be explained by a finite resolution of our code which produces only a 5% difference between the gravitationally softened force and the exact Newtonian force of point masses at 1 kpc from the cen...
Agarwal, Shankar; Feldman, Hume A; Lahav, Ofer; Thomas, Shaun A
2013-01-01
In this paper we introduce PkANN, a freely available software package for interpolating the non-linear matter power spectrum, constructed using Artificial Neural Networks (ANNs). Previously, using Halofit to calculate matter power spectrum, we demonstrated that ANNs can make extremely quick and accurate predictions of the power spectrum. Now, using a suite of 6380 N-body simulations spanning 580 cosmologies, we train ANNs to predict the power spectrum over the cosmological parameter space spanning $3\\sigma$ confidence level (CL) around the concordance cosmology. When presented with a set of cosmological parameters ($\\Omega_{\\rm m} h^2, \\Omega_{\\rm b} h^2, n_s, w, \\sigma_8, \\sum m_\
Doroshkevich, Andrei G.; Lukash, Vladimir N.; Mikheeva, Elena V.
2012-01-01
We discuss various aspects of the inner structure formation in virialized dark matter (DM) halos that form as primordial density inhomogeneities evolve in the cosmological standard model. The main focus is on the study of central cusps/cores and of the profiles of DM halo rotation curves, problems that reveal disagreements among the theory, numerical simulations, and observations. A method that was developed by the authors to describe equilibrium DM systems is presented, which allows investigating these complex nonlinear structures analytically and relating density distribution profiles within a halo both to the parameters of the initial small-scale inhomogeneity field and to the nonlinear relaxation characteristics of gravitationally compressed matter. It is shown that cosmological random motions of matter 'heat up' the DM particles in collapsing halos, suppressing cusp-like density profiles within developing halos, facilitating the formation of DM cores in galaxies, and providing an explanation for the difference between observed and simulated galactic rotation curves. The analytic conclusions obtained within this approach can be confirmed by the N-body model simulation once improved spatial resolution is achieved for central halo regions.
Cosmology in bimetric theory with an effective composite coupling to matter
Gümrükçüoğlu, A. Emir; Heisenberg, Lavinia; Mukohyama, Shinji; Tanahashi, Norihiro
2015-04-01
We study the cosmology of bimetric theory with a composite matter coupling. We find two possible branches of background evolution. We investigate the question of stability of cosmological perturbations. For the tensor and vector perturbations, we derive conditions on the absence of ghost and gradient instabilities. For the scalar modes, we obtain conditions for avoiding ghost degrees. In the first branch, we find that one of the scalar modes becomes a ghost at the late stages of the evolution. Conversely, this problem can be avoided in the second branch. However, we also find that the constraint for the second branch prevents the doubly coupled matter fields from being the standard ingredients of cosmology. We thus conclude that a realistic and stable cosmological model requires additional minimally coupled matter fields.
Cosmology in bimetric theory with an effective composite coupling to matter
Gumrukcuoglu, A Emir; Mukohyama, Shinji; Tanahashi, Norihiro
2015-01-01
We study the cosmology of bimetric theory with a composite matter coupling. We find two possible branches of background evolution. We investigate the question of stability of cosmological perturbations. For the tensor and vector perturbations, we derive conditions on the absence of ghost and gradient instabilities. For the scalar modes, we obtain conditions for avoiding ghost degrees. In the first branch, we find that one of the scalar modes becomes a ghost at the late stages of the evolution. Conversely, this problem can be avoided in the second branch. However, we also find that the constraint for the second branch prevents the doubly coupled matter fields from being the standard ingredients of cosmology. We thus conclude that a realistic and stable cosmological model requires additional minimally coupled matter fields.
Nonlinear clustering during the BEC dark matter phase transition
Energy Technology Data Exchange (ETDEWEB)
Freitas, Rodolfo C. de [Universidade Federal do Espirito Santo, Vitoria (Brazil); Ciencia e Tecnologia do Espirito Santo, Instituto Federal de Educacao, Vitoria (Brazil); Velten, Hermano [Universidade Federal do Espirito Santo, Vitoria (Brazil); Aix Marseille Universite, UMR 7332, CPT, Marseille (France)
2015-12-15
Spherical collapse of the Bose-Einstein condensate (BEC) dark matter model is studied in the Thomas-Fermi approximation. The evolution of the overdensity of the collapsed region and its expansion rate are calculated for two scenarios. We consider the case of a sharp phase transition (which happens when the critical temperature is reached) from the normal dark matter state to the condensate one and the case of a smooth first order phase transition where there is a continuous conversion of ''normal'' dark matter to the BEC phase. We present numerical results for the physics of the collapse for a wide range of the model's space parameter, i.e. the mass of the scalar particle m{sub χ} and the scattering length l{sub s}. We show the dependence of the transition redshift on m{sub χ} and l{sub s}. Since small scales collapse earlier and eventually before the BEC phase transition, the evolution of collapsing halos in this limit is indeed the same in both the CDM and the BEC models. Differences are expected to appear only on the largest astrophysical scales. However, we argue that the BEC model is almost indistinguishable from the usual dark matter scenario concerning the evolution of nonlinear perturbations above typical clusters scales, i.e., >or similar 10{sup 14}M{sub s}un. This provides an analytical confirmation for recent results from cosmological numerical simulations (Schive et al., Nat Phys 10:496, 2014). (orig.)
Origin and Destiny of Dark Matter Halos Cosmological Matter Exchange and Metal Enrichment
Kolatt, T S; Dekel, A; Primack, Joel R; Sigad, Y; Kravtsov, A V; Klypin, A A; Kolatt, Tsafrir S.; Bullock, James S.; Dekel, Avishai; Primack, Joel R.; Sigad, Yair; Kravtsov, Andrey V.; Klypin, Anatoly A.
2000-01-01
[Abridged] We analyze the exchange of dark matter between halos, subhalos, and their environments in a high-resolution cosmological N-body simulation of a Lambda CDM cosmology. At each analyzed redshift z we divide the dark matter particles into 4 components: (i) isolated galactic halos, (ii) subhalos, (iii) the diffuse medium of group and cluster halos, and (iv) the background outside of virialized halos. We follow the time evolution of the mass distribution and flows between these components and provide fitting functions for the exchange rates. We use our derived exchange rates to gauge the importance of metal redistribution in the universe due solely to gravity-induced interactions. The diffuse metallicity in clusters is predicted to be ~40% that in isolated galaxies (~55% of groups) at z=0, and should be lower only slightly by z=1, consistent with observations. The metallicity of the diffuse media in poor groups is expected to be lower by a factor of 5 by z~2, in agreement with the observed metallicity of...
Effective equations for isotropic quantum cosmology including matter
Bojowald, Martin; Skirzewski, Aureliano
2007-01-01
Effective equations often provide powerful tools to develop a systematic understanding of detailed properties of a quantum system. This is especially helpful in quantum cosmology where several conceptual and technical difficulties associated with the full quantum equations can be avoided in this way. Here, effective equations for Wheeler-DeWitt and loop quantizations of spatially flat, isotropic cosmological models sourced by a massive or interacting scalar are derived and studied. The resulting systems are remarkably different from that given for a free, massless scalar. This has implications for the coherence of evolving states and the realization of a bounce in loop quantum cosmology.
Randall-Sundrum brane cosmology: modification of late-time cosmic dynamics by exotic matter
Energy Technology Data Exchange (ETDEWEB)
Garcia-Salcedo, Ricardo [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada Legaria del IPN, Mexico DF (Mexico); Gonzalez, Tame [Departamento de Fisica, Centro de Investigacion y de Estudios Avanzadas del IPN, A.P.14-740, 07000, Mexico DF (Mexico); Moreno, Claudia [Departamento de Fisica y Matematicas, Centro Universitario de Ciencias Exactas e Ingenierias, Corregidora 500 SR, Universidad de Guadalajara, 44420 Guadalajara, Jalisco (Mexico); Quiros, Israel, E-mail: rigarcias@ipn.mx, E-mail: tamegc72@gmail.com, E-mail: claudia.moreno@cucei.udg.mx, E-mail: iquiros@fisica.ugto.mx [Division de Ciencias e IngenierIa de la Universidad de Guanajuato, AP 150, 37150, Leon, Guanajuato (Mexico)
2011-05-21
In this paper we show, through the study of concrete examples, that depending on the cosmic dynamics of the energy density of matter degrees of freedom living in the brane, Randall-Sundrum (RS) brane effects can be important not only at short distances (UV regime), but also at large cosmological scales (IR regime). Our first example relies on the study, by means of the dynamical system tools, of a toy model based in a nonlinear electrodynamics (NLED) Lagrangian. Then we show that other, less elaborated models, such as the inclusion of a scalar phantom field, and of a tachyon phantom field-trapped in the brane-produce similar results. The form of the RS correction seems to convert what would have been future attractors in general relativity into saddle points. The above 'mixing of scales' effect is distinctive only of theories that modify the right-hand side (matter part) of the Friedmann equation, so that, for instance, Dvali-Gabadadze-Porrati-brane models do not show this feature.
What does the N-point function hierarchy of the cosmological matter density field really measure ?
Carron, Julien
2015-01-01
The cosmological dark matter field is not completely described by its hierarchy of $N$-point functions, a non-perturbative effect with the consequence that only part of the theory can be probed with the hierarchy. We give here an exact characterization of the joint information of the full set of $N$-point correlators of the lognormal field. The lognormal field is the archetypal example of a field where this effect occurs, and, at the same time, one of the few tractable and insightful available models to specify fully the statistical properties of the evolved matter density field beyond the perturbative regime. Nonlinear growth in the Universe in that model is set letting the log-density field probability density functional evolve keeping its Gaussian shape, according to the diffusion equation in Euclidean space. We show that the hierarchy probes a different evolution equation, the diffusion equation defined not in Euclidean space but on the compact torus, with uniformity as the long-term solution. The extract...
Mead, Alexander; Heymans, Catherine; Joudaki, Shahab; Heavens, Alan
2015-01-01
We present an optimised variant of the halo model, designed to produce accurate matter power spectra well into the non-linear regime for a wide range of cosmological models. To do this, we introduce physically-motivated free parameters into the halo-model formalism and fit these to data from high-resolution N-body simulations. For a variety of $\\Lambda$CDM and $w$CDM models the halo-model power is accurate to $\\simeq 5$ per cent for $k\\leq 10h\\,\\mathrm{Mpc}^{-1}$ and $z\\leq 2$. We compare our results with recent revisions of the popular HALOFIT model and show that our predictions are more accurate. An advantage of our new halo model is that it can be adapted to account for the effects of baryonic feedback on the power spectrum. We demonstrate this by fitting the halo model to power spectra from the OWLS hydrodynamical simulation suite via parameters that govern halo internal structure. We are able to fit all feedback models investigated at the 5 per cent level using only two free parameters, and we place limi...
Quantized cosmological constant in 1+1 dimensional quantum gravity with coupled scalar matter
Energy Technology Data Exchange (ETDEWEB)
Govaerts, Jan; Zonetti, Simone, E-mail: Jan.Govaerts@uclouvain.be, E-mail: Simone.Zonetti@uclouvain.be [Centre for Cosmology, Particle Physics and Phenomenology (CP3), Institut de Recherche en Mathematique et Physique (IRMP), Universite catholique de Louvain, Chemin du Cyclotron 2, B-1348 Louvain-la Neuve (Belgium)
2011-09-21
A two-dimensional matter-coupled model of quantum gravity is studied in the Dirac approach to constrained dynamics in the presence of a cosmological constant. It is shown that after partial fixing to the conformal gauge, the requirement of a quantum realization of the conformal algebra for physical quantum states of the fields naturally constrains the cosmological constant to take values in a well-determined and mostly discrete spectrum. Furthermore, the contribution of the quantum fluctuations of the single dynamical degree of freedom in the gravitational sector, namely the conformal mode, to the cosmological constant is negative, in contrast to the positive contributions of the quantum fluctuations of the matter fields, possibly opening an avenue towards addressing the cosmological constant problem in a more general context.
Cosmological-constant cold dark matter models and the cobe two-year Sky maps
Bunn, E F; Emory F Bunn; Naoshi Sugiyama
1994-01-01
Abstract. We compare the two-year COBE DMR sky maps with the predictions of cosmological-constant cold dark matter models. Using a Bayesian analysis, we find that the most likely value of the cosmological constant in such a model is Lambda = 0. The data set an upper limit on Lambda of 0.71 (0.78) at 90% confidence, and 0.78 (0.86) at 95% confidence with (without) the quadrupole anisotropy.
On the non-linear stability of scalar field cosmologies
Energy Technology Data Exchange (ETDEWEB)
Alho, Artur; Mena, Filipe C [Centro de Matematica, Universidade do Minho, 4710-057 Braga (Portugal); Kroon, Juan A Valiente, E-mail: aalho@math.uminho.pt, E-mail: fmena@math.uminho.pt, E-mail: jav@maths.qmul.ac.uk [School of Mathematical Sciences, Queen Mary, University of London, London E1 4NS (United Kingdom)
2011-09-22
We review recent work on the stability of flat spatially homogeneous and isotropic backgrounds with a self-interacting scalar field. We derive a first order quasi-linear symmetric hyperbolic system for the Einstein-nonlinear-scalar field system. Then, using the linearized system, we show how to obtain necessary and sufficient conditions which ensure the exponential decay to zero of small non-linear perturbations.
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).
Asymmetric dark matter annihilation as a test of non-standard cosmologies
Energy Technology Data Exchange (ETDEWEB)
Gelmini, Graciela B.; Huh, Ji-Haeng; Rehagen, Thomas, E-mail: gelmini@physics.ucla.edu, E-mail: jhhuh@physics.ucla.edu, E-mail: trehagen@physics.ucla.edu [Department of Physics and Astronomy, University of California, Los Angeles (UCLA), 475 Portola Plaza, Los Angeles, CA 90095 (United States)
2013-08-01
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.
Cosmological perturbations in theories with non-minimal coupling between curvature and matter
Bertolami, Orfeu; Páramos, Jorge
2013-01-01
In this work, one examines how the presence of a non-minimal coupling between the spacetime curvature and matter affects the evolution of cosmological perturbations around 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 modification in the growth of matter density perturbations. One obtains approximate analytical solutions for the evolution of matter overdensities during the matter dominated era and shows that these favor the presence of a coupling function that is compatible with the late-time cosmic acceleration.
Dark matter as the Bose-Einstein condensation in loop quantum cosmology
Energy Technology Data Exchange (ETDEWEB)
Atazadeh, K.; Mousavi, M. [Azarbaijan Shahid Madani University, Department of Physics, Tabriz (Iran, Islamic Republic of); Darabi, F. [Azarbaijan Shahid Madani University, Department of Physics, Tabriz (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran, Islamic Republic of)
2016-06-15
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.)
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
Non-linear interactions in a cosmological background in the DGP braneworld
Koyama, K; Koyama, Kazuya; Silva, Fabio P
2007-01-01
We study quasi-static perturbations in a cosmological background in the Dvali-Gabadadze-Porrati (DGP) braneworld model. We identify the Vainshtein radius at which the non-linear interactions of the brane bending mode become important in a cosmological background. The Vainshtein radius in the early universe is much smaller than the one in the Minkowski background, but in a self-accelerating universe it is the same as the Minkowski background. Our result shows that the perturbative approach is applicable beyond the Vainshtein radius for weak gravity by taking into account the second order effects of the brane bending mode. The linearised cosmological perturbations are shown to be smoothly matched to the solutions inside the Vainshtein radius. We emphasize the importance of imposing a regularity condition in the bulk by solving the 5D perturbations and we highlight the problem of ad hoc assumptions on the bulk gravity that lead to different conclusions.
Garcia-Salcedo, Ricardo; Quiros, Israel
2013-01-01
Here we investigate the cosmic dynamics of Friedmann-Robertson-Walker universes -- flat spatial sections -- which are driven by nonlinear electrodynamics (NLED) Lagrangians. We pay special attention to the check of the sign of the square sound speed since, whenever the latter quantity is negative, the corresponding cosmological model is classically unstable against small perturbations of the background energy density. Besides, based on causality arguments, one has to require that the mentioned small perturbations of the background should propagate at most at the local speed of light. We also look for the occurrence of curvature singularities. Our results indicate that several cosmological models which are based in known NLED Lagrangians, either are plagued by curvature singularities of the sudden and/or big rip type, or are violently unstable against small perturbations of the cosmological background -- due to negative sign of the square sound speed -- or both. In addition, causality issues associated with su...
Cosmological aspects of a unified dark energy and dust dark matter model
Staicova, Denitsa; Stoilov, Michail
2017-01-01
Recently, a model of modified gravity plus single scalar field was proposed, in which the scalar couples both to the standard Riemannian volume form given by the square root of the determinant of the Riemannian metric, as well as to another non-Riemannian volume form given in terms of an auxiliary maximal rank antisymmetric tensor gauge field. This model provides an exact unified description of both dark energy (via dynamically generated cosmological constant) and dark matter (as a “dust” fluid due to a hidden nonlinear Noether symmetry). In this paper, we test the model against Supernovae type Ia experimental data and investigate the future Universe evolution which follows from it. Our results show that this model has very interesting features allowing various scenarios of Universe evolution and in the same time perfectly fits contemporary observational data. It can describe exponentially expanding or finite expanding Universe and moreover, a Universe with phase transition of first kind. The phase transition occurs to a new, emerging at some time ground state with lower energy density, which affects significantly the Universe evolution.
Early Structure Formation and Reionization in a Warm Dark Matter Cosmology
Yoshida, N; Hernquist, L; Springel, V; Yoshida, Naoki; Sokasian, Aaron; Hernquist, Lars; Springel, Volker
2003-01-01
We study first structure formation in Lambda-dominated universes using large cosmological N-body/SPH simulations. We consider a standard LCDM model and a LWDM model in which the mass of the dark matter particles is taken to be m_X=10 keV. The linear power spectrum for the LWDM model has a characteristic cut-off at a wavenumber k=200 /Mpc, suppressing the formation of low mass (< 10^6 Msun) nonlinear objects early on. The absence of low mass halos in the WDM model makes the formation of primordial gas clouds with molecular hydrogen very inefficient at high redshifts. The first star-forming gas clouds form at z~21 in the WDM model, considerably later than in the CDM counterpart, and the abundance of these gas clouds differs by an order of magnitude between the two models. We carry out radiative transfer calculations by embedding massive Population III stars in the gas clouds. We show that the volume fraction of ionized gas rises up close to 100% by z=18 in the CDM case, whereas that of the WDM model remains ...
Energy Technology Data Exchange (ETDEWEB)
Villaescusa-Navarro, Francisco; Viel, Matteo [INAF - Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34143, Trieste (Italy); Marulli, Federico [Dipartimento di Fisica e Astronomia - Università di Bologna, viale Berti Pichat 6/2, I-40127 Bologna (Italy); Branchini, Enzo [Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma (Italy); Castorina, Emanuele [SISSA - International School For Advanced Studies, Via Bonomea, 265 34136 Trieste (Italy); Sefusatti, Emiliano [The Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, 34151, Trieste (Italy); Saito, Shun, E-mail: villaescusa@oats.inaf.it, E-mail: federico.marulli3@unibo.it, E-mail: viel@oats.inaf.it, E-mail: branchin@fis.uniroma3.it, E-mail: ecastori@sissa.it, E-mail: esefusat@ictp.it, E-mail: shun.saito@ipmu.jp [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, The University of Tokyo, Chiba 277-8582 (Japan)
2014-03-01
By using a suite of large box-size N-body simulations that incorporate massive neutrinos as an extra set of particles, with total masses of 0.15, 0.30, and 0.60 eV, we investigate the impact of neutrino masses on the spatial distribution of dark matter haloes and on the distribution of galaxies within the haloes. We compute the bias between the spatial distribution of dark matter haloes and the overall matter and cold dark matter distributions using statistical tools such as the power spectrum and the two-point correlation function. Overall we find a scale-dependent bias on large scales for the cosmologies with massive neutrinos. In particular, we find that the bias decreases with the scale, being this effect more important for higher neutrino masses and at high redshift. However, our results indicate that the scale-dependence in the bias is reduced if the latter is computed with respect to the cold dark matter distribution only. We find that the value of the bias on large scales is reasonably well reproduced by the Tinker fitting formula once the linear cold dark matter power spectrum is used, instead of the total matter power spectrum. We also investigate whether scale-dependent bias really comes from purely neutrino's effect or from nonlinear gravitational collapse of haloes. For this purpose, we address the Ω{sub ν}-σ{sub 8} degeneracy and find that such degeneracy is not perfect, implying that neutrinos imprint a slight scale dependence on the large-scale bias. Finally, by using a simple halo occupation distribution (HOD) model, we investigate the impact of massive neutrinos on the distribution of galaxies within dark matter haloes. We use the main galaxy sample in the Sloan Digital Sky Survey (SDSS) II Data Release 7 to investigate if the small-scale galaxy clustering alone can be used to discriminate among different cosmological models with different neutrino masses. Our results suggest that different choices of the HOD parameters can reproduce the
Testing the EoS of dark matter with cosmological observations
Avelino, Arturo; Nucamendi, Ulises
2012-01-01
We explore the cosmological constraints on the parameter w_dm of the dark matter barotropic equation of state (EoS) to investigate the "warmness" of the dark matter fluid. The model is composed by the dark matter and dark energy fluids in addition to the radiation and baryon components. We constrain the values of w_dm using the latest cosmological observations that measure the expansion history of the Universe. When w_dm is estimated together with the parameter w_de of the barotropic EoS of dark energy we found that the cosmological data favor a value of w_dm = 0.006 +- 0.001, suggesting a -warm- dark matter, and w_de= -1.11 +- 0.03$ that corresponds to a phantom dark energy, instead of favoring a cold dark matter and a cosmological constant (w_dm = 0, w_de = -1). When w_dm is estimated alone but assuming w_de = -1, -1.1, -0.9, we found w_dm = 0.009 +- 0.002, 0.006 +- 0.002, 0.012 +- 0.002 respectively, where the errors are at 3 sigma (99.73%), i.e., w_dm > 0 with at least 99.73% of confidence level. When (w_...
Fully non-linear cosmological perturbations of multicomponent fluid and field systems
Hwang, Jai-chan; Noh, Hyerim; Park, Chan-Gyung
2016-09-01
We present fully non-linear and exact cosmological perturbation equations in the presence of multiple components of fluids and minimally coupled scalar fields. We ignore the tensor-type perturbation. The equations are presented without taking the temporal gauge condition in the Friedmann background with general curvature and the cosmological constant. We include the anisotropic stress. Even in the absence of anisotropic stress of individual component, the multiple component nature introduces the anisotropic stress in the collective fluid quantities. We prove the Newtonian limit of multiple fluids in the zero-shear gauge and the uniform-expansion gauge conditions, present the Newtonian hydrodynamic equations in the presence of general relativistic pressure in the zero-shear gauge, and present the fully non-linear equations and the third-order perturbation equations of the non-relativistic pressure fluids in the CDM-comoving gauge.
A conformal approach for the analysis of the non-linear stability of radiation cosmologies
Energy Technology Data Exchange (ETDEWEB)
Luebbe, Christian, E-mail: c.luebbe@ucl.ac.uk [Department of Mathematics, University College London, Gower Street, London, WC1E 6BT (United Kingdom); Department of Mathematics, University of Leicester, University Road, LE1 8RH (United Kingdom); Valiente Kroon, Juan Antonio, E-mail: j.a.valiente-kroon@qmul.ac.uk [School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS (United Kingdom)
2013-01-15
The conformal Einstein equations for a trace-free (radiation) perfect fluid are derived in terms of the Levi-Civita connection of a conformally rescaled metric. These equations are used to provide a non-linear stability result for de Sitter-like trace-free (radiation) perfect fluid Friedman-Lemaitre-Robertson-Walker cosmological models. The solutions thus obtained exist globally towards the future and are future geodesically complete. - Highlights: Black-Right-Pointing-Pointer We study the Einstein-Euler system in General Relativity using conformal methods. Black-Right-Pointing-Pointer We analyze the structural properties of the associated evolution equations. Black-Right-Pointing-Pointer We establish the non-linear stability of pure radiation cosmological models.
Can dark matter induce cosmological evolution of the fundamental constants of Nature?
Stadnik, Y V
2015-01-01
Traditional theories, which predict the cosmological evolution of the fundamental constants of Nature, assume that the underlying fields, which give rise to this evolution, are unnaturally light. We demonstrate that massive fields, such as dark matter, also directly produce a cosmological evolution of the fundamental constants. We consider the specific model of a scalar dark matter field $\\phi$, which interacts with Standard Model particles via quadratic couplings in $\\phi$. In this particular model, cosmological evolution of the fundamental constants arises due to changes in $\\left$ in time and space. The most stringent constraints on the physical parameters of the present model come from measurements of the neutron-proton mass difference at the time of the weak interaction freeze-out.
Cosmological Evolution in f(R,T) theory with Collisional Matter
Baffou, E H; Kpadonou, A V; Rodrigues, M E; Tossa, J
2015-01-01
We study the evolution of the cosmological parameters, namely, the deceleration parameter $q(z)$ and the parameter of effective equation of state in a universe contains, besides the ordinary matter and dark energy, a self-interacting (collisional matter), in the generalized $f(R,T)$ theory of gravity, where $R$ and $T$ are the curvature scalar and the trace of the energy-momentum tensor, respectively. We use the generalized FRW equations the equation of continuity and obtain a differential equation of second order in $H(z)$, and solve it numerically for studying the evolution of the cosmological parameters. Two $f(R,T)$ models are considered and the results with collisional matter are compared with the ones of the $\\Lambda$CDM model, and also with the model where there exists only non-collisional matter. The curves show that the models are acceptable because the values found for $w_{eff}$ are consistent with the observational data.
Dark energy and dust matter phases from an exact f(R)-cosmology model
Energy Technology Data Exchange (ETDEWEB)
Capozziello, S. [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' and INFN Sezioze di Napoli, Complesso Universitario di Monte S. Angelo, Ed. N, Via Cinthia, I-80126 Napoli (Italy)], E-mail: capozziello@na.infn.it; Martin-Moruno, P. [Colina de los Chopos, Instituto de Matematicas y Fisica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 121, 28006 Madrid (Spain); Rubano, C. [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' and INFN Sezioze di Napoli, Complesso Universitario di Monte S. Angelo, Ed. N, Via Cinthia, I-80126 Napoli (Italy)
2008-06-12
We show that dust matter-dark energy combined phases can be achieved by the exact solution derived from a power law f(R) cosmological model. This example answers the query by which a dust-dominated decelerated phase, before dark-energy accelerated phase, is needed in order to form large scale structures.
Is the continuous matter creation cosmology an alternative to $\\Lambda$CDM?
Fabris, J C; 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 $\\Lambda$CDM 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 observati...
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.
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
A supervised machine learning estimator for the non-linear matter power spectrum - SEMPS
Mohammed, Irshad
2015-01-01
In this article, we argue that models based on machine learning (ML) can be very effective in estimating the non-linear matter power spectrum ($P(k)$). We employ the prediction ability of the supervised ML algorithms to build an estimator for the $P(k)$. The estimator is trained on a set of cosmological models, and redshifts for which the $P(k)$ is known, and it learns to predict $P(k)$ for any other set. We review three ML algorithms -- Random Forest, Gradient Boosting Machines, and K-Nearest Neighbours -- and investigate their prime parameters to optimize the prediction accuracy of the estimator. We also compute an optimal size of the training set, which is realistic enough, and still yields high accuracy. We find that, employing the optimal values of the internal parameters, a set of $50-100$ cosmological models is enough to train the estimator that can predict the $P(k)$ for a wide range of cosmological models, and redshifts. Using this configuration, we build a blackbox -- Supervised Estimator for Matter...
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.
Exponents of non-linear clustering in scale-free one dimensional cosmological simulations
Benhaiem, David; Sicard, François
2012-01-01
One dimensional versions of cosmological N-body simulations have been shown to share many qualitative behaviours of the three dimensional problem. They can resolve a large range of time and length scales, and admit exact numerical integration. We use such models to study how non-linear clustering depends on initial conditions and cosmology. More specifically, we consider a family of models which, like the 3D EdS model, lead for power-law initial conditions to self-similar clustering characterized in the strongly non-linear regime by power-law behaviour of the two point correlation function. We study how the corresponding exponent \\gamma depends on the initial conditions, characterized by the exponent n of the power spectrum of initial fluctuations, and on a single parameter \\kappa controlling the rate of expansion. The space of initial conditions/cosmology divides very clearly into two parts: (1) a region in which \\gamma depends strongly on both n and \\kappa and where it agrees very well with a simple general...
Preons, Dark Matter and the Production of Early Cosmological Structures
Burdyuzha, V; Ponomarev, Yu; Vereshkov, G M; Ponomarev, Yu.
1999-01-01
If the preon structure of quarks, leptons and gauge bosons will be proved then in the Universe during relativistic phase transition the production of nonperturbative preon condensates has been occured collective excitations of which are perceived as pseudogoldstone bosons. Dark matter consisting of pseudogoldstone bosons of familon type contains a "hot" component from massless particles and a "cold" (nonrelativistic) component from massive particles. It is shown that such dark matter was undergone to two relativistic phase transitions temperatures of which were different. In the result of these phase transitions the structurization of dark matter and therefore the baryon subsystem has taken place. Besides, the role of particle generations in the Universe become more evident. For the possibility of structurization of matter as minimum three generations of particles are necessary.
The generation model of particle physics and the cosmological matter-antimatter asymmetry problem
Robson, B A
2016-01-01
The matter-antimatter asymmetry problem, corresponding to the virtual nonexistence of antimatter in the universe, is one of the greatest mysteries of cosmology. Within the framework of the Generation Model (GM) of particle physics, it is demonstrated that the matter-antimatter asymmetry problem may be understood in terms of the composite leptons and quarks of the GM. It is concluded that there is essentially no matter-antimatter asymmetry in the present universe and that the observed hydrogen-antihydrogen asymmetry may be understood in terms of statistical fluctuations associated with the complex many-body processes involved in the formation of either a hydrogen atom or an antihydrogen atom.
Galaxy clusters as probes for cosmology and dark matter
Battistelli, Elia S; de Bernardis, Paolo; Kirillov, Alexander A; Neto, Gastao B Lima; Masi, Silvia; Norgaard-Nielsen, Hans U; Ostermann, Peter; Roman, Matthieu; Rosati, Piero; Rossetti, Mariachiara
2016-01-01
In recent years, significant progress has been made in building new galaxy clusters samples, at low and high redshifts, from wide-area surveys, particularly exploiting the Sunyaev--Zel'dovich (SZ) effect. A large effort is underway to identify and characterize these new systems with optical/NIR and X-ray facilities, thus opening new avenues to constraint cosmological models using structure growth and geometrical tests. A census of galaxy clusters sets constraints on reionization mechanisms and epochs, which need to be reconciled with recent limits on the reionization optical depth from cosmic microwave background (CMB) experiments. Future advances in SZ effect measurements will include the possibility to (unambiguously) measure directly the kinematic SZ effect, to build an even larger catalogue of galaxy clusters able to study the high redshift universe, and to make (spatially-)resolved galaxy cluster maps with even spectral capability to (spectrally-)resolve the relativistic corrections of the SZ effect.
Thermodynamics properties of tachyon cosmology with non-minimal coupling to matter
Farajollahi, H; Abolghasemi, M
2016-01-01
Recently, we have investigated the dynamics of the universe in tachyon cosmology with non-minimal coupling to matter \\cite{faraj}-\\cite{faraj3}. In particular, for the interacting holographic dark energy (IHDE), the model is studied in \\cite{Ravanpak}. In the current work, a significant observational program has been conducted to unveil the model's thermodynamic properties. Our result shows that the IHDE version of our model better fits the observational data than $\\Lambda$CDM model. The first and generalized second thermodynamics laws for the universe enveloped by cosmological apparent and event horizon are revisited. From the results, both first and generalized second laws, constrained by the observational data, are satisfied on cosmological apparent horizon.In addition, the total entropy is verified with the observation only if the horizon of the universe is taken as apparent horizon. Then, due to validity of generalized second law, the current cosmic acceleration is also predicted.
Nonlinear optical spectroscopy of soft matter interfaces.
Roke, Sylvie
2009-07-13
Soft matter consists of complex molecules that can undergo drastic structural transformations under mild changes of chemical and physical conditions. Since a wide variety of chemical, physical and biological processes occur at soft matter interfaces, they can exhibit complex behavior. This is even more so for interfaces of colloidal soft matter since the relative amount of interface material increases by orders of magnitude. Herein, we focus on new developments that enable us to obtain detailed molecular structural changes in the topmost molecular layers of soft matter interfaces composed of complex bio-molecules. In particular, the possibilities to probe interfaces of colloidal soft matter systems are discussed.
Ordinary matter in nonlinear affine gauge theories of gravitation
Tiemblo, A; Tiemblo, A; Tresguerres, R
1994-01-01
We present a general framework to include ordinary fermionic matter in the metric--affine gauge theories of gravity. It is based on a nonlinear gauge realization of the affine group, with the Lorentz group as the classification subgroup of the matter and gravitational fields.
The Cosmological Consequences of the Preon Structure of Matter
Burdyuzha, V; Lalakulich, O; Ponomarev, Yu; Burdyuzha, Vladimir; Vereshkov, Grigory; Lalakulich, Olga; Ponomarev, Yuri
1999-01-01
If the preon structure of quarks, leptons and gauge bosons will be provedthen in the Universe during a relativistic phase transition the production ofnonperturbative preon condensates has occured. Familons are collectiveexcitations of these condensates. It is shown that the dark matter consisting of familon type pseudogoldstonebosons was undergone to two relativistic phase transitions temperatures ofwhich were different. In the result of these phase transitions thestructurization of dark matter and therefore the baryon subsystem has takenplace. In the Universe two characteristic scales which have printed thisphenomenon arise naturally.
The cosmological consequences of the preon structure of matter
Burdyuzha, Vladimir V.; Vereshkov, Grigory M.; Lalakulich, Olga D.; Ponomarev, Yuri N.
1999-07-01
If the preon structure of quarks, leptons and gauge bosons will be proved then in the Universe during a relativistic phase transition the production of nonperturbative preon condensates has occurred. Familons are collective excitations of these condensates. It is shown that the dark matter consisting of familon type pseudogoldstone bosons was undergone to two relativistic phase transitions temperatures of which were different. In the result of these phase transitions the structurization of dark matter and therefore the baryon subsystem had taken place. In the Universe two characteristic scales which have printed this phenomenon arise naturally.
Does the diffusion dark matter-dark energy interaction model solve cosmological puzzles?
Szydłowski, Marek; Stachowski, Aleksander
2016-08-01
We study dynamics of cosmological models with diffusion effects modeling dark matter and dark energy interactions. We show the simple model with diffusion between the cosmological constant sector and dark matter, where the canonical scaling law of dark matter (ρd m ,0a-3(t )) is modified by an additive ɛ (t )=γ t a-3(t ) to the form ρd m=ρd m ,0a-3(t )+ɛ (t ). We reduced this model to the autonomous dynamical system and investigate it using dynamical system methods. This system possesses a two-dimensional invariant submanifold on which the dark matter-dark energy (DM-DE) interaction can be analyzed on the phase plane. The state variables are density parameter for matter (dark and visible) and parameter δ characterizing the rate of growth of energy transfer between the dark sectors. A corresponding dynamical system belongs to a general class of jungle type of cosmologies represented by coupled cosmological models in a Lotka-Volterra framework. We demonstrate that the de Sitter solution is a global attractor for all trajectories in the phase space and there are two repellers: the Einstein-de Sitter universe and the de Sitter universe state dominating by the diffusion effects. We distinguish in the phase space trajectories, which become in good agreement with the data. They should intersect a rectangle with sides of Ωm ,0∈[0.2724 ,0.3624 ] , δ ∈[0.0000 ,0.0364 ] at the 95% CL. Our model could solve some of the puzzles of the Λ CDM model, such as the coincidence and fine-tuning problems. In the context of the coincidence problem, our model can explain the present ratio of ρm to ρd e, which is equal 0.457 6-0.0831+0.1109 at a 2 σ confidence level.
Non-linear Higgs portal to Dark Matter
Bajo, Rocío del Rey
2016-01-01
The Higgs portal to scalar Dark Matter is considered in the context of non-linearly realised electroweak symmetry breaking. We determine the interactions of gauge bosons and the physical Higgs particle $h$ to a scalar singlet Dark Matter candidate $S$ in an effective description. The main phenomenological differences with respect to the standard scenario can be seen in the Dark Matter relic abundance, in direct/indirect searches and in signals at colliders.
Glueball dark matter in non-standard cosmologies
Acharya, Bobby S.; Fairbairn, Malcolm; Hardy, Edward
2017-07-01
Hidden sector glueball dark matter is well motivated by string theory, compactifications of which often have extra gauge groups uncoupled to the visible sector. We study the dynamics of glueballs in theories with a period of late time primordial matter domination followed by a low final reheating temperature due to a gravitationally coupled modulus. Compared to scenarios with a high reheating temperature, the required relic abundance is possible with higher hidden sector confinement scales, and less extreme differences in the entropy densities of the hidden and visible sectors. Both of these can occur in string derived models, and relatively light moduli are helpful for obtaining viable phenomenology. We also study the effects of hidden sector gluinos. In some parts of parameter space these can be the dominant dark matter component, while in others their abundance is much smaller than that of glueballs. Finally, we show that heavy glueballs produced from energy in the hidden sector prior to matter domination can have the correct relic abundance if they are sufficiently long lived.
Constraining Dark Matter-Baryon Scattering with Linear Cosmology
Dvorkin, Cora; Kamionkowski, Marc
2013-01-01
We derive constraints on elastic scattering between baryons and dark matter using the cosmic microwave background (CMB) data from the Planck satellite and the Lyman-alpha forest data from the Sloan Digital Sky Survey. Elastic scattering allows baryons and dark matter to exchange momentum, affecting the dynamics of linear density perturbations in the early Universe. We derive constraints to scattering cross sections of the form sigma \\propto v^n, allowing for a wide range of velocity dependencies with n between -4 and 2. We improve and correct previous estimates where they exist, including velocity-independent cross section as well as dark matter millicharge and electromagnetic dipole moments. Lyman-alpha forest data dominates the constraints for n>-3, where the improvement over CMB data alone can be several orders of magnitude. Dark matter-baryon scattering cannot affect the halo mass function on mass scales M>10^{12} M_{solar}. Our results imply, model-independently, that a baryon in the halo of a galaxy lik...
Cosmology with self-interacting sterile neutrinos and dark matter - A pseudoscalar model
Archidiacono, Maria; Hansen, Rasmus Sloth; Tram, Thomas
2014-01-01
Short baseline neutrino oscillation experiments have shown hints of the existence of additional sterile neutrinos in the eV mass range. Such sterile neutrinos are incompatible with cosmology because they suppress structure formation unless they can be prevented from thermalising in the early Universe. Here we present a novel scenario in which both sterile neutrinos and dark matter are coupled to a new, light pseudoscalar. This can prevent thermalisation of sterile neutrinos and make dark matter sufficiently self-interacting to have an impact on galactic dynamics and possibly resolve some of the known problems with the standard cold dark matter scenario. Our model singles out a dimensionless coupling strength for both sterile neutrinos and dark matter in the range $g_s \\sim g_d \\sim 10^{-5}$ and predicts a dark matter particle mass in the MeV range.
Intragroup dark matter distribution in small galaxy group-like systems in a LCDM cosmology
Aceves, Hector; Altamirano-Devora, L; Ramon-Fox, F G; Cañas, R
2013-01-01
In this paper we study the distribution of dark matter in small galaxy groups, in a LCDM cosmology, identified using a physical criterion. We quantify the amount of intra-group dark matter and characterize its distribution. We find that compact associations of galaxies, as well as those intermediate and loose groups, have a rather flat profiles with a logarithmic slope of gamma =-0.2. Hence, the intra-group dark matter does not follow the same cuspy tendency that haloes of galaxies have. In intermediate and loose galaxy associations the intragroup matter tends to be <50% that of the total mass of the group, and in compact associations is <20% within their group radius. So, in general, common dark matter haloes of small galaxy groups are not cuspy nor massive.
Can Dark Matter Induce Cosmological Evolution of the Fundamental Constants of Nature?
Stadnik, Y V; Flambaum, V V
2015-11-13
We demonstrate that massive fields, such as dark matter, can directly produce a cosmological evolution of the fundamental constants of nature. We show that a scalar or pseudoscalar (axionlike) dark matter field ϕ, which forms a coherently oscillating classical field and interacts with standard model particles via quadratic couplings in ϕ, produces "slow" cosmological evolution and oscillating variations of the fundamental constants. We derive limits on the quadratic interactions of ϕ with the photon, electron, and light quarks from measurements of the primordial (4)He abundance produced during big bang nucleosynthesis and recent atomic dysprosium spectroscopy measurements. These limits improve on existing constraints by up to 15 orders of magnitude. We also derive limits on the previously unconstrained linear and quadratic interactions of ϕ with the massive vector bosons from measurements of the primordial (4)He abundance.
Phantom expansion with non-linear Schr\\"{o}dinger-type formulation of scalar field cosmology
Phetnora, Theerakarn; Gumjudpai, Burin
2008-01-01
We describe non-flat standard Friedmann cosmology of canonical scalar field with barotropic fluid in form of non-linear Schr\\"{o}dinger-type (NLS) formulation in which all cosmological dynamical quantities are expressed in term of Schr\\"{o}dinger quantities as similar to those in time-independent quantum mechanics. We assume the expansion to be superfast, i.e. phantom expansion. We report all Schr\\"{o}dinger-analogous quantities to scalar field cosmology. Effective equation of state coefficient is analyzed and illustrated. We show that in a non-flat universe, there is no fixed $w_{\\rm eff}$ value for the phantom divide. In a non-flat universe, even $w_{\\rm eff} > -1$, the expansion can be phantom. Moreover, in open universe, phantom expansion can happen even with $w_{\\rm eff} > 0$. We also report scalar field exact solutions within frameworks of the Friedmann formulation and the NLS formulation in non-flat universe cases.
Simulating the Effect of Non-Linear Mode-Coupling in Cosmological Parameter Estimation
Kiessling, A; Heavens, A F
2011-01-01
Fisher Information Matrix methods are commonly used in cosmology to estimate the accuracy that cosmological parameters can be measured with a given experiment, and to optimise the design of experiments. However, the standard approach usually assumes both data and parameter estimates are Gaussian-distributed. Further, for survey forecasts and optimisation it is usually assumed the power-spectra covariance matrix is diagonal in Fourier-space. But in the low-redshift Universe, non-linear mode-coupling will tend to correlate small-scale power, moving information from lower to higher-order moments of the field. This movement of information will change the predictions of cosmological parameter accuracy. In this paper we quantify this loss of information by comparing naive Gaussian Fisher matrix forecasts with a Maximum Likelihood parameter estimation analysis of a suite of mock weak lensing catalogues derived from N-body simulations, based on the SUNGLASS pipeline, for a 2-D and tomographic shear analysis of a Eucl...
Non-linear structure formation in the "Running FLRW" cosmological model
Bibiano, Antonio
2016-01-01
We present a suite of cosmological N-body simulations describing the "Running Friedmann-Lema{\\"i}tre-Robertson-Walker" (R-FLRW) cosmological model. This model is based on quantum field theory in a curved space-time and extends {\\Lambda}CDM with a time-evolving vacuum density, {\\Lambda}(z), and time-evolving gravitational Newton's coupling, G(z). In this paper we review the model and introduce the necessary analytical treatment needed to adapt a reference N-body code. Our resulting simulations represent the first realisation of the full growth history of structure in the R-FLRW cosmology into the non-linear regime, and our normalisation choice makes them fully consistent with the latest cosmic microwave background data. The post-processing data products also allow, for the first time, an analysis of the properties of the halo and sub-halo populations. We explore the degeneracies of many statistical observables and discuss the steps needed to break them. Furthermore, we provide a quantitative description of the...
Geometric nonlinearities in field theory, condensed matter and analytical mechanics
Directory of Open Access Journals (Sweden)
J.J. Sławianowski
2010-01-01
Full Text Available There are two very important subjects in physics: Symmetry of dynamical models and nonlinearity. All really fundamental models are invariant under some particular symmetry groups. There is also no true physics, no our Universe and life at all, without nonlinearity. Particularly interesting are essential, non-perturbative nonlinearities which are not described by correction terms imposed on some well-defined linear background. Our idea in this paper is that there exists some mysterious, still incomprehensible link between essential, physically relevant nonlinearity and dynamical symmetry, first of all, of large symmetry groups. In some sense the problem is known even in soliton theory, where the essential nonlinearity is often accompanied by the infinite system of integrals of motion, thus, by infinite-dimensional symmetry groups. Here we discuss some more familiar problems from the realm of field theory, condensed matter physics, and analytical mechanics, where the link between essential nonlinearity and high symmetry is obvious, although not fully understandable.
Unified dark matter and dark energy description in a chiral cosmological model
Abbyazov, Renat R
2014-01-01
We show the way of dark matter and dark energy presentation via ansatzs on the kinetic energies of the fields in the two-component chiral cosmological model. To connect a kinetic interaction of dark matter and dark energy with observational data the reconstruction procedure for the chiral metric component $h_{22}$ and the potential of (self)interaction $V$ has been developed. The reconstruction of $h_{22}$ and $V$ for the early and later inflation have been performed. The proposed model is confronted to $\\Lambda CDM$ model as well.
Minimal inflationary cosmologies and production of heavy dark matter
Maity, Debaprasad
2016-01-01
Generalizing one of the author's recent paper on minimal Higgs inflation, we proposed and analyzed a large class of inflationary models with non-polynomial modification of the potential. The modification is done by introducing a single scale creating an infinite plateau for large inflaton field value. One can identify those class of potentials as a small dip at the origin of a constant one dimensional field space. Because of this large flat plateau, we find all the predictions are fitting extremely well with the recent observations made by PLANCK. We have extensively studied perturbative reheating phenomena specifically focusing on the production of dark matter heavier than the reheating temperature. We generalize the well known analysis of heavy dark matter production for general equation of state $w$ of the oscillating inflaton field. However, at the end we consider effective equation of state $w = (n-2)/(n+2)$ emerging form our model. Where, $n$ is the index of the power law potential during late time osci...
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.
Cosmological Density and Power Spectrum from Peculiar Velocities Nonlinear Corrections and PCA
Silberman, L; Eldar, A; Zehavi, I
2001-01-01
we allow for nonlinear effects in the likelihood analysis of galaxy peculiar velocities, and obtain ~35%-lower values for the cosmological density parameter and for the amplitude of mass-density fluctuations. The power spectrum in the linear regime is assumed to be a flat LCDM model (h=0.65, n=1, COBE) with only Om_m as a free parameter. Since the likelihood is driven by the nonlinear regime, we "break" the power spectrum at k_b=0.2 h/Mpc and fit a power law at k>k_b. This allows for independent matching of the nonlinear behavior and an unbiased fit in the linear regime. The analysis assumes Gaussian fluctuations and errors, and a linear relation between velocity and density. Tests using mock catalogs that properly simulate nonlinear effects demonstrate that this procedure results in a reduced bias and a better fit. We find for the Mark3 and SFI data Om_m=0.32+-0.06 and 0.37+-0.09 respectively, with sigma_8*Om_m^0.6 =0.49+-0.06 and 0.63+-0.08, in agreement with constraints from other data. The quoted 90% erro...
Numerical Simulations in Cosmology; 3, Dark Matter Halos
Klypin, A A
2000-01-01
Properties of dark matter halos are reviewed. Taken from different publications, we present results on (1) the mass and velocity functions, (2) density and velocity profiles, and (3) concentration of halos. In the range of radii r=(0.005-1)rvir the density profile for a quiet isolated halo is very accurately approximated by a fit suggested by Moore etal (1997): rho=1/x^1.5(1+x^1.5), where x=r/rs and rs is a characteristic radius. The fit suggested by Navarro et al (1995) rho= 1/x(1+x)^2, also gives a very satisfactory approximation with relative errors of about 10% for radii not smaller than 1% of the virial radius. The mass function of z=0 halos with mass below 10^{13}Msun/h is approximated by a power law with slope alpha =-1.85. The slope increases with the redshift. The velocity function of halos with Vmax< 500km/s is also a power law with the slope beta= -3.8-4. The power-law extends to halos at least down to 10km/s. It is also valid for halos inside larger virialized halos. The concentration of halos ...
Towards accurate cosmological predictions for rapidly oscillating scalar fields as dark matter
Ureña-López, L Arturo
2015-01-01
As we are entering the era of precision cosmology, it is necessary to count on accurate cosmological predictions from any proposed model of dark matter. In this paper we present a novel approach to the cosmological evolution of scalar fields that eases their analytic and numerical analysis at the background and at the linear order of perturbations. We apply the method to a scalar field endowed with a quadratic potential and revisit its properties as dark matter. Some of the results known in the literature are recovered, and a better understanding of the physical properties of the model is provided. It is shown that the Jeans wavenumber defined as $k_J = a \\sqrt{mH}$ is directly related to the suppression of linear perturbations at wavenumbers $k>k_J$. We also discuss some semi-analytical results that are well satisfied by the full numerical solutions obtained from an amended version of the CMB code CLASS. Finally we draw some of the implications that this new treatment of the equations of motion may have in t...
Massive Neutrinos and the Non-linear Matter Power Spectrum
Bird, Simeon; Haehnelt, Martin G
2011-01-01
We perform an extensive suite of N-body simulations of the matter power spectrum, incorporating massive neutrinos in the range M = 0.15-0.6 eV, probing the non-linear regime at scales k < 10 hMpc-1 at z < 3. We extend the widely used HALOFIT approximation (Smith et al. 2003) to account for the effect of massive neutrinos on the power spectrum. In the strongly non-linear regime HALOFIT systematically over-predicts the suppression due to the free-streaming of the neutrinos. The maximal discrepancy occurs at k \\sim 1hMpc-1, and is at the level of 10% of the total suppression. Most published constraints on neutrino masses based on HALOFIT are not affected, as they rely on data probing the matter power spectrum in the linear or mildly non-linear regime. However, predictions for future galaxy, Lyman-alpha forest and weak lensing surveys extending to more non-linear scales will benefit from the improved approximation to the non-linear matter power spectrum we provide. Our approximation reproduces the induced n...
Abate, Alexandra; Teodoro, Luis F A; Warren, Michael S; Hendry, Martin
2008-01-01
We investigate methods to best estimate the normalisation of the mass density fluctuation power spectrum (sigma_8) using peculiar velocity data from a survey like the Six degree Field Galaxy Velocity Survey (6dFGSv). We focus on two potential problems (i) biases from nonlinear growth of structure and (ii) the large number of velocities in the survey. Simulations of LambdaCDM-like models are used to test the methods. We calculate the likelihood from a full covariance matrix of velocities averaged in grid cells. This simultaneously reduces the number of data points and smooths out nonlinearities which tend to dominate on small scales. We show how the averaging can be taken into account in the predictions in a practical way, and show the effect of the choice of cell size. We find that a cell size can be chosen that significantly reduces the nonlinearities without significantly increasing the error bars on cosmological parameters. We compare our results with those from a principal components analysis following Wa...
Dark matter production mechanisms with a nonthermal cosmological history: A classification
Kane, Gordon L.; Kumar, Piyush; Nelson, Brent D.; Zheng, Bob
2016-03-01
We perform a comprehensive study of models of dark matter (DM) in a Universe with a nonthermal cosmological history, i.e. with a phase of pressureless matter domination before the onset of big-bang nucleosynthesis (BBN). Such cosmological histories are generically predicted by UV completions that contain gravitationally coupled scalar fields (moduli). We classify the different production mechanisms for DM in this framework, generalizing previous works by considering a wide range of DM masses/couplings and allowing for DM to be in equilibrium with a "dark" sector. We identify four distinct parametric regimes for the production of relic DM, and derive accurate semianalytic approximations for the DM relic abundance. Our results are particularly relevant for supersymmetric theories, in which the standard nonthermally produced DM candidates are disfavored by indirect-detection constraints. We also comment on experimental signals in this framework, focusing on novel effects involving the power spectrum of DM density perturbations. In particular, we identify a class of models where the spectrum of DM density perturbations is sensitive to the pressureless matter-dominated era before BBN, giving rise to interesting astrophysical signatures to be looked for in the future. A worthwhile future direction would be to study well-motivated theoretical models within this framework and carry out detailed studies of the pattern of expected experimental signals.
How robust are inflation model and dark matter constraints from cosmological data?
Energy Technology Data Exchange (ETDEWEB)
Hamann, J. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Hannestad, S.; Sloth, M.S. [Aarhus Univ. (Denmark). Dept. of Physics and Astronomy; Wong, Y.Y.Y. [Max-Planck-Institut fuer Physik, Muenchen (Germany). Werner-Heisenberg-Institut
2006-11-15
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 {lambda}CDM models, the simple {lambda}{phi}{sup 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 {tau} and the neutrino mass prevents {lambda}{phi}{sup 4} from being excluded by present data. Reversing the argument, if {lambda}{phi}{sup 4} is the correct model of inflation, it predicts a sum of neutrino masses at 0.3{yields}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<{omega}{sub c}h{sup 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.)
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.
Wang, B; Atrio-Barandela, F; Pavon, D
2016-01-01
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.
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.
The Hubble parameter in the early universe with viscous QCD matter and finite cosmological constant
Tawfik, A
2011-01-01
The evolution of a flat, isotropic and homogeneous universe is studied. The background geometry in the early phases of the universe is conjectured to be filled with causal bulk viscous cosmological fluid and dark energy. The energy density relations obtained from the assumption of covariant conservation of energy-momentum tensor of the background matter in the early universe are used to derive the basic equation for the Hubble parameter $H$. The viscous properties described by ultra-relativistic equations of state and bulk viscosity taken from recent heavy-ion collisions and lattice QCD calculations have been utilized to give an approximate solution of the field equations. The cosmological constant is conjectured to be related to the energy density of the vacuum. In this treatment, there is a clear evidence for singularity at vanishing cosmic time $t$ indicating the dominant contribution from the dark energy. The time evolution of $H$ seems to last for much longer time than the ideal case, where both cosmolog...
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
Cosmology in ghost-free bigravity theory with twin matter fluids: The origin of "dark matter"
Aoki, Katsuki
2013-01-01
We study dynamics of Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime based on the ghost-free bigravity theory. Assuming the coupling parameters guaranteeing the existence of de Sitter space as well as Minkowski spacetime, we find two stable attractors for spacetime with "twin" dust matter fields: One is de Sitter accelerating universe and the other is matter dominated universe. Although a considerable number of initial data leads to de Sitter universe, we also find matter dominated universe or spacetime with a future singularity for some initial data. The cosmic no-hair conjecture does not exactly hold, but the accelerating expansion can be found naturally. The $\\Lambda$-CDM model is obtained as an attractor. We also show that the dark matter component in the Friedmann equation, which originates from another twin matter, can be about 5 times larger than the baryonic matter, by choosing the appropriate coupling constants.
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.
The inner structure of dwarf sized halos in Warm and Cold Dark Matter cosmologies
Gonzalez-Samaniego, Alejandro; Colin, Pedro
2015-01-01
By means of N-body+Hydrodynamics 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 mh=2-3x10^10 Msun at z=0, both in a WDM and CDM cosmology. The half-mode mass in the WDM power spectrum of our simulations is Mv= 2x 10^10 Msun. In the dark matter only simulations halo density profiles are well described by the NFW parametric fit in both cosmologies, though the WDM halos have concentrations lower by factors 1.5--2.0 than their CDM counterparts. In the hydrodynamical 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 ~ 0.02xRv, alpha, becomes shallow in periods of 2 to 5 Gyr in the WDM runs. We explore whether this flattening process correlates with the global SF, Ms/Mv ratio, gas outflow, and internal specific angular momentum histories. We do not ...
Weak Nonlinear Matter Waves in a Trapped Spin-1 Condensates
Institute of Scientific and Technical Information of China (English)
CAI Hong-Qiang; YANG Shu-Rong; XUE Ju-Kui
2011-01-01
The dynamics of the weak nonlinear matter solitary waves in a spin-1 condensates with harmonic external potential are investigated analytically by a perturbation method. It is shown that, in the small amplitude limit, the dynamics of the 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 spinor BEGs. The analytical expressions for the evolution of soliton show that the small-amplitude vector solitons of the mixed types perform harmonic oscillations in the presence of the trap. Furthermore, the emitted radiation profiles and the soliton oscillation freauencv are also obtained.
Charged anisotropic matter with linear or nonlinear equation of state
Varela, Victor; Ray, Saibal; Chakraborty, Kaushik; Kalam, Mehedi
2010-01-01
Ivanov pointed out substantial analytical difficulties associated with self-gravitating, static, isotropic fluid spheres when pressure explicitly depends on matter density. Simplification achieved with the introduction of electric charge were noticed as well. We deal with self-gravitating, charged, anisotropic fluids and get even more flexibility in solving the Einstein-Maxwell equations. In order to discuss analytical solutions we extend Krori and Barua's method to include pressure anisotropy and linear or non-linear equations of state. The field equations are reduced to a system of three algebraic equations for the anisotropic pressures as well as matter and electrostatic energy densities. Attention is paid to compact sources characterized by positive matter density and positive radial pressure. Arising solutions satisfy the energy conditions of general relativity. Spheres with vanishing net charge contain fluid elements with unbounded proper charge density located at the fluid-vacuum interface. Notably the...
The Hubble parameter in the early universe with viscous QCD matter and finite cosmological constant
Energy Technology Data Exchange (ETDEWEB)
Tawfik, A. [Egyptian Center for Theoretical Physics (ECTP), MTI University, Cairo (Egypt)
2011-05-15
The evolution of a flat, isotropic and homogeneous universe is studied. The background geometry in the early phases of the universe is conjectured to be filled with causal bulk viscous fluid and dark energy. The energy density relations obtained from the assumption of covariant conservation of energy-momentum tensor of the background matter in the early universe are used to derive the basic equation for the Hubble parameter H. The viscous properties described by ultra-relativistic equations of state and bulk viscosity taken from recent heavy-ion collisions and lattice QCD calculations have been utilized to give an approximate solution of the field equations. The cosmological constant is conjectured to be related to the energy density of the vacuum. In this treatment, there is a clear evidence for singularity at vanishing cosmic time t indicating the dominant contribution from the dark energy. The time evolution of H seems to last for much longer time than the ideal case, where both cosmological constant and viscosity coefficient are entirely vanishing. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
The dark matter crisis: falsification of the current standard model of cosmology
Kroupa, Pavel
2012-01-01
The current standard model of cosmology (SMoC) requires The Dual Dwarf Galaxy Theorem to be true. According to this theorem two types of dwarf galaxies must exist: primordial dark-matter (DM) dominated (type A) dwarf galaxies, and tidal-dwarf and ram-pressure-dwarf (type B) galaxies void of DM. In the model, type A dwarfs are distributed approximately spherically following the shape of the host galaxy DM halo, while type B dwarfs are typically correlated in phase-space. Type B dwarfs must exist in any cosmological theory in which galaxies interact. Only one type of dwarf galaxy is observed to exist on the baryonic Tully-Fisher plot and in the radius-mass plane. The Milky Way satellite system forms a vast phase-space-correlated structure that includes globular clusters and stellar and gaseous streams. Similar arguments apply to Andromeda. Other galaxies also have phase-space correlated satellite systems. Therefore, The Dual Galaxy Theorem is falsified by observation and dynamically relevant cold or warm DM on ...
How robust are inflation model and dark matter constraints from cosmological data?
Hamann, J; Sloth, M S; Wong, Y Y Y; Hamann, Jan; Hannestad, Steen; Sloth, Martin S.; Wong, Yvonne Y.Y.
2006-01-01
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 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 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 of the next generation of neutrino mass measurements. We also discuss the associated constraints on the dark matter de...
Mantz, Adam B; Morris, R Glenn
2016-01-01
This is the fifth in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Our sample comprises 40 clusters identified as being dynamically relaxed and hot in Papers I and II of this series. Here we use constraints on cluster mass profiles from X-ray data to test some of the basic predictions of cosmological structure formation in the Cold Dark Matter (CDM) paradigm. We present constraints on the concentration--mass relation for massive clusters, finding a power-law mass dependence with a slope of $\\kappa_m=-0.16\\pm0.07$, in agreement with CDM predictions. For this relaxed sample, the relation is consistent with a constant as a function of redshift (power-law slope with $1+z$ of $\\kappa_\\zeta=-0.17\\pm0.26$), with an intrinsic scatter of $\\sigma_{\\ln c}=0.16\\pm0.03$. We investigate the shape of cluster mass profiles over the radial range probed by the data (typically $\\sim50$kpc--1Mpc), and test for departures from the simple Navarro, Frenk & White (NFW...
Odintsov, S D
2016-01-01
We present some cosmological models which unify the late and early-time acceleration eras with the radiation and the matter domination era, and we realize the cosmological models by using the theoretical framework of $F(R)$ gravity. Particularly, the first model unifies the late and early-time acceleration with the matter domination era, and the second model unifies all the evolution eras of our Universe. The two models are described in the same way at early and late times, and only the intermediate stages of the evolution have some differences. Each cosmological model contains two Type IV singularities which are chosen to occur one at the end of the inflationary era and one at the end of the matter domination era. The cosmological models at early times are approximately identical to the $R^2$ inflation model, so these describe a slow-roll inflationary era which ends when the slow-roll parameters become of order one. The inflationary era is followed by the radiation era and after that the matter domination er...
Marsh, David J. E.
2016-07-01
Axions comprise a broad class of particles that can play a major role in explaining the unknown aspects of cosmology. They are also well-motivated within high energy physics, appearing in theories related to CP-violation in the standard model, supersymmetric theories, and theories with extra-dimensions, including string theory, and so axion cosmology offers us a unique view onto these theories. I review the motivation and models for axions in particle physics and string theory. I then present a comprehensive and pedagogical view on the cosmology and astrophysics of axion-like particles, starting from inflation and progressing via BBN, the CMB, reionization and structure formation, up to the present-day Universe. Topics covered include: axion dark matter (DM); direct and indirect detection of axions, reviewing existing and future experiments; axions as dark radiation; axions and the cosmological constant problem; decays of heavy axions; axions and stellar astrophysics; black hole superradiance; axions and astrophysical magnetic fields; axion inflation, and axion DM as an indirect probe of inflation. A major focus is on the population of ultralight axions created via vacuum realignment, and its role as a DM candidate with distinctive phenomenology. Cosmological observations place robust constraints on the axion mass and relic density in this scenario, and I review where such constraints come from. I next cover aspects of galaxy formation with axion DM, and ways this can be used to further search for evidence of axions. An absolute lower bound on DM particle mass is established. It is ma > 10-24eV from linear observables, extending to ma ≳ 10-22eV from non-linear observables, and has the potential to reach ma ≳ 10-18eV in the future. These bounds are weaker if the axion is not all of the DM, giving rise to limits on the relic density at low mass. This leads to the exciting possibility that the effects of axion DM on structure formation could one day be detected
Lovell, Mark R; Boyarsky, Alexey; Crain, Robert A; Frenk, Carlos S; Hellwing, Wojciech A; Ludlow, Aaron D; Navarro, Julio F; Ruchayskiy, Oleg; Sawala, Till; Schaller, Matthieu; Schaye, Joop; Theuns, Tom
2016-01-01
We study galaxy formation in sterile neutrino dark matter models that differ significantly from both cold and from `warm thermal relic' models. We use the EAGLE code to carry out hydrodynamic simulations of the evolution of pairs of galaxies chosen to resemble the Local Group, as part of the APOSTLE simulations project. We compare cold dark matter (CDM) with two sterile neutrino models with 7 keV mass: one, the warmest among all models of this mass (LA120) and the other, a relatively cold case (LA10). We show that the lower concentration of sterile neutrino subhalos compared to their CDM counterparts makes the inferred inner dark matter content of galaxies like Fornax (or Magellanic Clouds) less of an outlier in the sterile neutrino cosmologies. In terms of the galaxy number counts the LA10 simulations are \\emph{indistinguishable} from CDM when one takes into account halo-to-halo (or `simulation-to-simulation') scatter. In order for the LA120 model to match the number of Local Group dwarf galaxies, a higher f...
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.
Baryonic and dark matter distribution in cosmological simulations of spiral galaxies
Mollitor, Pol; Teyssier, Romain
2014-01-01
We study three high resolution cosmological hydrodynamical simulations of Milky Way-sized halos including a comparison with the corresponding DM-only counterparts performed with the adaptive mesh refinement code RAMSES. We analyse the stellar and the gas distribution and find one of our simulated galaxies with interesting Milky Way-like features with regard to several observational tests. Thanks to consistently tuned star formation rate and supernovae feedback, we manage to obtain an extended disk and a flat rotation curve with a circular velocity and a dark matter density in the solar neighbourhood in agreement with observations. With a careful look at the derivation of the stellar-to-halo mass ratio, we also obtain competitive values for this criterion. Concerning the dark matter distribution, we explicitly show the interaction with the baryons and show how the dark matter is first contracted by star formation and then cored by feedback processes. Analysing the clump spectrum, we find a shift in mass with r...
Off-shell Dark Matter: A Cosmological relic of Quantum Gravity
Saravani, Mehdi
2016-01-01
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 (OfDM). However, their rate of production is suppressed by the scale of non-locality (e.g. Planck length). As a result, we show that OfDM 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 OfDM is indeed cold, and discuss potentially observable signatures on small scale matter power ...
Sussman, R A; Sussman, Roberto A.; Pavon, Diego
1999-01-01
We derive a new class of exact solutions of Einstein's equations providing a physically plausible hydrodynamical description of cosmological matter in the radiative era ($10^6 K > T > 10^3 K$), between nucleosynthesis and decoupling. The solutions are characterized by the Lemaître-Tolman -Bondi metric with a viscous fluid source, subjected to the following conditions: (a) the equilibrium state variables satisfy the equation of state of a mixture of an ultra-relativistic and a non-relativistic ideal gases, where the internal energy of the latter has been neglected, (b) the particle numbers of the mixture components are independently conserved, (c) the viscous stress is consistent with the transport equation and entropy balance law of Extended Irreversible Thermodynamics, with the coefficient of shear viscosity provided by Kinetic Theory for the `radiative gas' model. The fulfilment of (a), (b) and (c) restricts initial conditions in terms of an initial value function, fluctuations of photon entropy per baryon...
Interacting agegraphic dark energy model in tachyon cosmology coupled to matter
Energy Technology Data Exchange (ETDEWEB)
Farajollahi, H., E-mail: hosseinf@guilan.ac.ir [Department of Physics, University of Guilan, Rasht (Iran, Islamic Republic of); School of Physics, University of New South Wales, Sydney, NSW, 2052 (Australia); Ravanpak, A., E-mail: aravanpak@guilan.ac.ir [Department of Physics, University of Guilan, Rasht (Iran, Islamic Republic of); Fadakar, G.F., E-mail: gfadakar@guilan.ac.ir [Department of Physics, University of Guilan, Rasht (Iran, Islamic Republic of)
2012-05-15
Scalar-field dark energy models for tachyon fields are often regarded as an effective description of an underlying theory of dark energy. In this Letter, we propose the agegraphic dark energy model in tachyon cosmology by interaction between the components of the dark sectors. In the formalism, the interaction term emerges from the tachyon field nonminimally coupled to the matter Lagrangian in the model rather than being inserted into the formalism as an external source. The model is constrained by the observational data. Based on the best fitted parameters in both original and new agegraphic dark energy scenarios, the model is tested by Sne Ia data. The tachyon potential and tachyon field are reconstructed and coincidence problem is revisited.
Modified Brans-Dicke cosmology with matter-scalar field interaction
Kofinas, Georgios; Saridakis, Emmanuel N
2016-01-01
We discuss the cosmological implications of an extended Brans-Dicke theory presented recently, in which there is an energy exchange between the scalar field and ordinary matter, determined by the theory. A new mass scale is generated in the theory which modifies the Friedmann equations with field-dependent corrected kinetic terms. In a radiation universe the general solutions are found and there are branches with complete removal of the initial singularity, while at the same time a transient accelerating period can occur within deceleration. Entropy production is also possible in the early universe. In the dust era, late-times acceleration has been found numerically in agreement with the correct behaviour of the density parameters and the dark energy equation of state, while the gravitational constant has only a slight variation over a large redshift interval in agreement with observational bounds.
Observational Aspects of an Inhomogeneous Cosmology
Saulder, Christoph; Zeilinger, Werner W
2012-01-01
One of the biggest mysteries in cosmology is Dark Energy, which is required to explain the accelerated expansion of the universe within the standard model. But maybe one can explain the observations without introducing new physics, by simply taking one step back and re-examining one of the basic concepts of cosmology, homogeneity. In standard cosmology, it is assumed that the universe is homogeneous, but this is not true at small scales (<200 Mpc). Since general relativity, which is the basis of modern cosmology, is a non-linear theory, one can expect some backreactions in the case of an inhomogeneous matter distribution. Estimates of the magnitude of these backreactions (feedback) range from insignificant to being perfectly able to explain the accelerated expansion of the universe. In the end, the only way to be sure is to test predictions of inhomogeneous cosmological theories, such as timescape cosmology, against observational data. If these theories provide a valid description of the universe, one expe...
Photonics linear and nonlinear interactions of laser light and matter
Menzel, R
2007-01-01
This book covers the fundamental properties and the description of single photons and light beams, experimentally and theoretically. It explains the essentials of linear interactions and most nonlinear interactions between light and matter in both the transparent and absorbing cases. It also provides a basic understanding of modern quantum optics and lasers, as well as the principles of nonlinear optical spectroscopy. It is self-consistent and enriched by a large number of calculated illustrations, examples, and descriptive tables. Graduate students in physics and electrical engineering, as well as other sciences, will find this book a thorough introduction to the field, while for lecturers and scientists it is a rich source of useful information and a ready-to-hand reference. The new edition has been thoroughly expanded and revised in all sections
The Inner Structure of Dwarf-sized Halos in Warm and Cold Dark Matter Cosmologies
González-Samaniego, A.; Avila-Reese, V.; Colín, P.
2016-03-01
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 Mv = (2-3) × 1010 h-1 M⊙ 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 Mf = 2 × 1010 h-1 M⊙. 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 ≈0.02Rv, α0.02, 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), Ms/Mv ratio, gas outflow, and internal specific angular momentum histories. We do not find any clear trends, but when α0.02 is shallower than -0.5, Ms/Mv 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 dwarfs are softened, their stellar half-mass radii strongly grow with time, and their central surface densities
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
Characterization of the cosmological nonlinear path of single galaxies in N-body Simulations
Stalder Díaz, Diego Herbin; Rosa, Reinaldo; Clua, Esteban; Campanharo, Andriana
Turbulent-like behaviour is an important and recent ingredient in the investigation of large scale structure formation in the observable universe [1,2]. Recently, an established statistical method was used to demonstrate the importance of considering chaotic advection (or Lagrange turbulence) in combination with gravitational instabilities in the LambdaCDM simulations performed from the Virgo Consortium (VC). However, the Hubble volumes simulated from GADGET-VC algoritm have some limitations for direct lagrangian data analysis due to the large amount of data and no real time computation for particle kinetic velocity along the dark matter structure evolution. We use our COsmic LAgrangian TUrbulence Simulator (COLATUS) [3], based on GPU/CUDA technology, to perform gravitational Cosmological N-body simulations and tracking the particles paths. In this work we discuss the chaotic advection behavior of tracers galaxies based on the angular velocity fluctuation analysis of single particles during its trajectory to the gravitational collapse of super clusters at low redshifts. [1] Caretta et al., A&A doi:10.1051/0004-6361:20079105 [2] Rosa et al., CCP doi: 10.1016/j.cpc.2008.11.018 [3] Stalder et al., AIP doi: 10.1063/1.4756992
Ishikawa, Takashi; Nishimichi, Takahiro; Takahashi, Ryuichi; Yoshida, Naoki; Tonegawa, Motonari
2013-01-01
Redshift space distortion (RSD) observed in galaxy redshift surveys is a powerful tool to test gravity theories on cosmological scales, but the systematic uncertainties must carefully be examined for future surveys with large statistics. Here we employ various analytic models of RSD and estimate the systematic errors on measurements of the structure growth-rate parameter, f\\sigma_8, induced by non-linear effects and the halo bias with respect to the dark matter distribution, by using halo catalogues from 40 realisations of 3.4 \\times 10^8 comoving h^{-3}Mpc^3 cosmological N-body simulations. We consider hypothetical redshift surveys at redshifts z=0.5, 1.35 and 2, and different minimum halo mass thresholds in the range of 5.0 \\times 10^{11} -- 2.0 \\times 10^{13} h^{-1} M_\\odot. We find that the systematic error of f\\sigma_8 is greatly reduced to ~4 per cent level, when a recently proposed analytical formula of RSD that takes into account the higher-order coupling between the density and velocity fields is ado...
Ishikawa, Takashi; Totani, Tomonori; Nishimichi, Takahiro; Takahashi, Ryuichi; Yoshida, Naoki; Tonegawa, Motonari
2014-10-01
Redshift-space distortion (RSD) observed in galaxy redshift surveys is a powerful tool to test gravity theories on cosmological scales, but the systematic uncertainties must carefully be examined for future surveys with large statistics. Here we employ various analytic models of RSD and estimate the systematic errors on measurements of the structure growth-rate parameter, fσ8, induced by non-linear effects and the halo bias with respect to the dark matter distribution, by using halo catalogues from 40 realizations of 3.4 × 108 comoving h-3 Mpc3 cosmological N-body simulations. We consider hypothetical redshift surveys at redshifts z = 0.5, 1.35 and 2, and different minimum halo mass thresholds in the range of 5.0 × 1011-2.0 × 1013 h-1 M⊙. We find that the systematic error of fσ8 is greatly reduced to ˜5 per cent level, when a recently proposed analytical formula of RSD that takes into account the higher order coupling between the density and velocity fields is adopted, with a scale-dependent parametric bias model. Dependence of the systematic error on the halo mass, the redshift and the maximum wavenumber used in the analysis is discussed. We also find that the Wilson-Hilferty transformation is useful to improve the accuracy of likelihood analysis when only a small number of modes are available in power spectrum measurements.
Quintin, Jerome; Sherkatghanad, Zeinab; Cai, Yi-Fu; Brandenberger, Robert H.
2015-09-01
Assuming that curvature perturbations and gravitational waves originally arise from vacuum fluctuations in a matter-dominated phase of contraction, we study the dynamics of the cosmological perturbations evolving through a nonsingular bouncing phase described by a generic single scalar field Lagrangian minimally coupled to Einstein gravity. In order for such a model to be consistent with the current upper limits on the tensor-to-scalar ratio, there must be an enhancement of the curvature fluctuations during the bounce phase. We show that, while it remains possible to enlarge the amplitude of curvature perturbations due to the nontrivial background evolution, this growth is very limited because of the conservation of curvature perturbations on super-Hubble scales. We further perform a general analysis of the evolution of primordial non-Gaussianities through the bounce phase. By studying the general form of the bispectrum we show that the non-Gaussianity parameter fNL (which is of order unity before the bounce phase) is enhanced during the bounce phase if the curvature fluctuations grow. Hence, in such nonsingular bounce models with matter given by a single scalar field, there appears to be a tension between obtaining a small enough tensor-to-scalar ratio and not obtaining a value of fNL in excess of the current upper bounds. This conclusion may be considered as a "no-go" theorem that rules out any single field matter bounce cosmology starting with vacuum initial conditions for the fluctuations.
A fresh look at linear cosmological constraints on a decaying dark matter component
Poulin, Vivian; Lesgourgues, Julien
2016-01-01
We consider a cosmological model in which a fraction $f$ 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) $\\Gamma$ and $f$ 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 $f\\Gamma < 6.3\\times10^{-3}$ Gyr$^{-1}$. For the first time, we also checked that degeneracies with massive neutrinos are broken when informa...
Buchert, Thomas
2010-01-01
We outline the key-steps towards the construction of a physical, fully relativistic cosmology, in which we aim to trace Dark Energy and Dark Matter back to physical properties of space. The influence of inhomogeneities on the effective evolution history of the Universe is encoded in backreaction terms and expressed through spatially averaged geometrical invariants. These are absent and interpreted as missing dark fundamental sources in the standard model. In the inhomogeneous case they can be interpreted as energies of an emerging scalar field (the morphon). These averaged invariants vanish for a homogeneous geometry, where the morphon is in an unstable equilibrium state. If this state is perturbed, the morphon can act as a classical inflaton in the Early Universe and its de-balanced energies can mimic the dark sources in the Late Universe, depending on spatial scale as Dark Energy or as Dark Matter, respectively. We lay down a line of arguments that is qualitatively conclusive, and we outline open problems o...
Modeling the gravitational potential of a cosmological dark matter halo with stellar streams
Sanderson, Robyn E; Helmi, Amina
2016-01-01
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 static spherical and triaxial NFW potentials both 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. T...
Modeling the Gravitational Potential of a Cosmological Dark Matter Halo with Stellar Streams
Sanderson, Robyn E.; Hartke, Johanna; Helmi, Amina
2017-02-01
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)
Mantz, A.B.; /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Allen, S.W.; /KIPAC, Menlo Park /Stanford U., Phys. Dept. /SLAC; Morris, R.Glenn; /KIPAC, Menlo Park /SLAC
2016-07-15
This is the fifth in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Our sample comprises 40 clusters identified as being dynamically relaxed and hot in Papers I and II of this series. Here we use constraints on cluster mass profiles from X-ray data to test some of the basic predictions of cosmological structure formation in the cold dark matter (CDM) paradigm. We present constraints on the concentration–mass relation for massive clusters, finding a power-law mass dependence with a slope of κm = -0.16 ± 0.07, in agreement with CDM predictions. For this relaxed sample, the relation is consistent with a constant as a function of redshift (power-law slope with 1 + z of κζ = -0.17 ± 0.26), with an intrinsic scatter of σln c = 0.16 ± 0.03. We investigate the shape of cluster mass profiles over the radial range probed by the data (typically ~50 kpc–1 Mpc), and test for departures from the simple Navarro–Frenk–White (NFW) form, for which the logarithmic slope of the density profile tends to -1 at small radii. Specifically, we consider as alternatives the generalized NFW (GNFW) and Einasto parametrizations. For the GNFW model, we find an average value of (minus) the logarithmic inner slope of β = 1.02 ± 0.08, with an intrinsic scatter of σβ = 0.22 ± 0.07, while in the Einasto case we constrain the average shape parameter to be α = 0.29 ± 0.04 with an intrinsic scatter of σα = 0.12 ± 0.04. Our results are thus consistent with the simple NFW model on average, but we clearly detect the presence of intrinsic, cluster-to-cluster scatter about the average.
Mantz, A. B.; Allen, S. W.; Morris, R. G.
2016-10-01
This is the fifth in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Our sample comprises 40 clusters identified as being dynamically relaxed and hot in Papers I and II of this series. Here we use constraints on cluster mass profiles from X-ray data to test some of the basic predictions of cosmological structure formation in the cold dark matter (CDM) paradigm. We present constraints on the concentration-mass relation for massive clusters, finding a power-law mass dependence with a slope of κm = -0.16 ± 0.07, in agreement with CDM predictions. For this relaxed sample, the relation is consistent with a constant as a function of redshift (power-law slope with 1 + z of κζ = -0.17 ± 0.26), with an intrinsic scatter of σln c = 0.16 ± 0.03. We investigate the shape of cluster mass profiles over the radial range probed by the data (typically ˜50 kpc-1 Mpc), and test for departures from the simple Navarro-Frenk-White (NFW) form, for which the logarithmic slope of the density profile tends to -1 at small radii. Specifically, we consider as alternatives the generalized NFW (GNFW) and Einasto parametrizations. For the GNFW model, we find an average value of (minus) the logarithmic inner slope of β = 1.02 ± 0.08, with an intrinsic scatter of σβ = 0.22 ± 0.07, while in the Einasto case we constrain the average shape parameter to be α = 0.29 ± 0.04 with an intrinsic scatter of σα = 0.12 ± 0.04. Our results are thus consistent with the simple NFW model on average, but we clearly detect the presence of intrinsic, cluster-to-cluster scatter about the average.
Neyrinck, Mark C
2014-01-01
In the current cosmological paradigm, an initially flat three-dimensional manifold that pervades space (the `dark-matter sheet') folds up to build concentrations of mass (galaxies), and a cosmic web between them. Galaxies are nodes, connected by a network of filaments and walls. The folding is in six-dimensional (3D position, plus 3D velocity) phase space. The positions of creases, or caustics, mark the edges of structures. Here, I introduce an origami approximation to cosmological structure formation, in which the dark-matter sheet is not allowed to stretch. But it still produces an idealized cosmic web, with nodes, filaments, walls and voids. In 2D, nodes form in `polygonal collapse' (a twist-fold in origami), necessarily generating filaments simultaneously. In 3D, nodes form in `polyhedral collapse,' simultaneously generating filaments and walls. The masses, spatial arrangement, and angular momenta of nodes and filaments are related in the model. I describe some `tetrahedral collapse', or tetrahedral twist...
Doroshkevich, A. G.; Lukash, V. N.; Mikheeva, E. V.
2012-01-01
We discuss various aspects of the inner structure formation in virialized dark matter (DM) halos that form as primordial density inhomogeneities evolve in the cosmological standard model. The main focus is on the study of central cusps/cores and of the profiles of DM halo rotation curves, problems that reveal disagreements among the theory, numerical simulations, and observations. A method that was developed by the authors to describe equilibrium DM systems is presented, which allows investig...
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.
CMB-galaxy correlation in Unified Dark Matter scalar field cosmologies
Energy Technology Data Exchange (ETDEWEB)
Bertacca, Daniele; Bartolo, Nicola; Matarrese, Sabino [Dipartimento di Fisica Galileo Galilei Università di Padova, via F. Marzolo 8, I-35131 Padova (Italy); Raccanelli, Alvise [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Portsmouth, PO1 3FX (United Kingdom); Piattella, Oliver F. [Departamento de Física, Universidade Federal do Espírito Santo, avenida Ferrari 514, 29075-910 Vitória, ES (Brazil); Pietrobon, Davide [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, 91109 Pasadena CA U.S.A. (United States); Giannantonio, Tommaso, E-mail: daniele.bertacca@pd.infn.it, E-mail: alvise.raccanelli@port.ac.uk, E-mail: oliver.piattella@gmail.com, E-mail: davide.pietrobon@jpl.nasa.gov, E-mail: nicola.bartolo@pd.infn.it, E-mail: sabino.matarrese@pd.infn.it, E-mail: tommaso.giannantonio@Universe-cluster.de [Excellence Cluster Universe, Technical University Munich, Boltzmannstraße 2, D-85748 Garching bei München (Germany)
2011-03-01
We present an analysis of the cross-correlation between the CMB and the large-scale structure (LSS) of the Universe in Unified Dark Matter (UDM) scalar field cosmologies. We work out the predicted cross-correlation function in UDM models, which depends on the speed of sound of the unified component, and compare it with observations from six galaxy catalogues (NVSS, HEAO, 2MASS, and SDSS main galaxies, luminous red galaxies, and quasars). We sample the value of the speed of sound and perform a likelihood analysis, finding that the UDM model is as likely as the ΛCDM, and is compatible with observations for a range of values of c{sub ∞} (the value of the sound speed at late times) on which structure formation depends. In particular, we obtain an upper bound of c{sub ∞}{sup 2} ≤ 0.009 at 95% confidence level, meaning that the ΛCDM model, for which c{sub ∞}{sup 2} = 0, is a good fit to the data, while the posterior probability distribution peaks at the value c{sub ∞}{sup 2} = 10{sup −4} . Finally, we study the time dependence of the deviation from ΛCDM via a tomographic analysis using a mock redshift distribution and we find that the largest deviation is for low-redshift sources, suggesting that future low-z surveys will be best suited to constrain UDM models.
Neyrinck, Mark C
2012-01-01
Tessellations are valuable both conceptually and for analysis in the study of the large-scale structure of the universe. They provide a conceptual model for the 'cosmic web,' and are of great use to analyze cosmological data. Here we describe tessellations in another set of coordinates, of the initially flat sheet of dark matter that gravity folds up in rough analogy to origami. The folds that develop are called caustics, and they tessellate space into stream regions. Tessellations of the dark-matter sheet are also useful in simulation analysis, for instance for density measurement, and to identify structures where streams overlap.
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.
Kroupa, Pavel
2016-01-01
The spatial arrangement of galaxies (of satellites on a scale of 100kpc) as well as their three-dimensional distribution in galaxy groups such as the Local Group (on a scale of 1Mpc), the distribution of galaxies in the nearby volume of galaxies (on a scale of 8Mpc) and in the nearby Universe (on a scale of 1Gpc) is considered. There is further evidence that the CMB shows irregularities and for anisotropic cosmic expansion. The overall impression one obtains, given the best data we have, is matter to be arranged as not expected in the dark-matter based standard model of cosmology (SMoC). There appears to be too much structure, regularity and organisation. Dynamical friction on the dark matter halos is a strong direct test for the presence of dark matter particles, but this process does not appear to be operative in the real Universe. This evidence suggests strongly that dynamically relevant dark matter does not exist and therefore cosmology remains largely not understood theoretically. More-accepted awareness...
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.
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.
Energy Technology Data Exchange (ETDEWEB)
Alexander, Stephon
2003-07-15
We give an overview of the current issues in early universe cosmology and consider the potential resolution of these issues in an as yet nascent spin foam cosmology. The model is the Barrett-Crane Model for quantum gravity along with a generalization of manifold complexes to complexes including conical singularities.
Vankov, A
1998-01-01
The suggested alternative cosmology is based on the idea of barion symmetric universe, in which our home universe is a representative of multitude of typical matter and antimatter universes. This alternative concept gives a physically reasonable explanation of all major problems of the Standard Cosmological Model. Classification Code MSC: Cosmology 524.8 Key words: standard cosmological model, alternative cosmology, barionic symmetry, typical universe, quasars, cosmic rays.
Coasting cosmologies with time dependent cosmological constant
Pimentel, L O; Pimentel, Luis O.
1999-01-01
The effect of a time dependent cosmological constant is considered in a family of scalar tensor theories. Friedmann-Robertson-Walker cosmological models for vacumm and perfect fluid matter are found. They have a linear expansion factor, the so called coasting cosmology, the gravitational "constant" decreace inversely with time; this model satisfy the Dirac hipotesis. The cosmological "constant" decreace inversely with the square of time, therefore we can have a very small value for it at present time.
Amin, Mustafa A; Blandford, Roger D
2007-01-01
The relationship between the metric and nonrelativistic matter distribution depends on the theory of gravity and additional fields, hence providing a possible way of distinguishing competing theories. With the assumption that the geometry and kinematics of the homogeneous universe have been measured, we present a procedure for understanding and testing the relationship between the cosmological matter distribution and metric perturbations (along with their respective evolution) using the ratio of the physical size of the perturbation to the size of the horizon as our small expansion parameter. We expand around Newtonian gravity on linear, sub-horizon scales with coefficient functions in front of the expansion parameter. Our framework relies on an ansatz which ensures that (i) the Poisson equation is recovered on small scales (ii) the metric variables (and any additional fields) are generated and supported by the nonrelativistic matter overdensity. The scales for which our framework is intended are small enough...
Group field cosmology: a cosmological field theory of quantum geometry
Calcagni, Gianluca; Oriti, Daniele
2012-01-01
Following the idea of a field quantization of gravity as realized in group field theory, we construct a minisuperspace model where the wavefunction of canonical quantum cosmology (either Wheeler-DeWitt or loop quantum cosmology) is promoted to a field, the coordinates are minisuperspace variables, the kinetic operator is the Hamiltonian constraint operator, and the action features a nonlinear and possibly nonlocal interaction term. We discuss free-field classical solutions, the quantum propagator, and a mean-field approximation linearizing the equation of motion and augmenting the Hamiltonian constraint by an effective term mixing gravitational and matter variables. Depending on the choice of interaction, this can reproduce, for example, a cosmological constant, a scalar-field potential, or a curvature contribution.
Dynamics of gravitating hadron matter in Bianchi-IX cosmological model
Pavluchenko, Sergey A
2016-01-01
We perform an analysis of the Einstein-Skyrme cosmological model in Bianchi-IX background. We analytically describe asymptotic regimes and semi-analytically -- generic regimes. It appears that depending on the product of Newtonian constant $\\kappa$ with Skyrme coupling $K$, in absence of the cosmological term there are three regimes possible -- recollapse with $\\kK 2$. In presence of the positive cosmological term, power-law regimes turn to exponential (de Sitter) ones while recollapse regime turn to exponential if the value for $\\Lambda$-term is sufficiently large, otherwise the regime remains recollapse. Negative cosmological term leads to the recollapse regardless of $\\kK$. All nonsingular regimes have the squashing coefficient $a(t) \\to 1$ at late times, which is associated with restoring symmetry dynamics. Also all nonsingular regimes appear to be linearly stable -- exponential solutions always while power-law for an open region of initial conditions.
Abate, Alexandra; Bridle, Sarah; Teodoro, Luis F. A.; Warren, Michael S.; Hendry, Martin
2008-10-01
We investigate methods to best estimate the normalization of the mass density fluctuation power spectrum (σ8) using peculiar velocity data from a survey like the six-degree Field Galaxy Velocity Survey (6dFGSv). We focus on two potential problems: (i) biases from non-linear growth of structure and (ii) the large number of velocities in the survey. Simulations of ΛCDM-like models are used to test the methods. We calculate the likelihood from a full covariance matrix of velocities averaged in grid cells. This simultaneously reduces the number of data points and smoothes out non-linearities which tend to dominate on small scales. We show how the averaging can be taken into account in the predictions in a practical way, and show the effect of the choice of cell size. We find that a cell size can be chosen that significantly reduces the non-linearities without significantly increasing the error bars on cosmological parameters. We compare our results with those from a principal components analysis following Watkins et al. and Feldman et al. to select a set of optimal moments constructed from linear combinations of the peculiar velocities that are least sensitive to the non-linear scales. We conclude that averaging in grid cells performs equally well. We find that for a survey such as 6dFGSv we can estimate σ8 with less than 3 per cent bias from non-linearities. The expected error on σ8 after marginalizing over Ωm is approximately 16 per cent.
Initial conditions, Discreteness and non-linear structure formation in cosmology
Sylos-Labini, F; Gabrielli, A; Joyce, M; Labini, Francesco Sylos; Baertschiger, Thierry; Gabrielli, Andrea; Joyce, Michael
2002-01-01
In this lecture we address three different but related aspects of the initial continuous fluctuation field in standard cosmological models. Firstly we discuss the properties of the so-called Harrison-Zeldovich like spectra. This power spectrum is a fundamental feature of all current standard cosmological models. In a simple classification of all stationary stochastic processes into three categories, we highlight with the name ``super-homogeneous'' the properties of the class to which models like this, with $P(0)=0$, belong. In statistical physics language they are well described as glass-like. Secondly, the initial continuous density field with such small amplitude correlated Gaussian fluctuations must be discretised in order to set up the initial particle distribution used in gravitational N-body simulations. We discuss the main issues related to the effects of discretisation, particularly concerning the effect of particle induced fluctuations on the statistical properties of the initial conditions and on th...
Nonlinear description of Yang-Mills cosmology: cosmic inflation and the accompanying Hannay’s angle
Bouguerra, Yacine; Maamache, Mustapha; Ryeol Choi, Jeong
2017-06-01
Hannay’s angle is a classical analogue of the “geometrical phase factor” found by Berry in his research on the quantum adiabatic theorem. This classical analogue is defined if closed curves of constant action variables return to the same curves in phase space after an adaibatic evolution. Adiabatic evolution of Yang-Mills cosmology, which is described by a time-dependent quartic oscillator, is investigated. Phase properties of the Yang-Mills fields are analyzed and the corresponding Hannay’s angle is derived from a rigorous evaluation. The obtained Hannay’s angle shift is represented in terms of several observable parameters associated with such an angle shift. The time evolution of Hannay’s angle in Yang-Mills cosmology is examined from an illustration plotted on the basis of numerical evaluation, and its physical nature is addressed. Hannay’s angle, together with its quantum counterpart Berry’s phase, plays a pivotal role in conceptual understanding of several cosmological problems and indeed can be used as a supplementary probe for cosmic inflation. Supported by Basic Science Research Program through National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2016R1D1A1A09919503)
Indian Academy of Sciences (India)
P. K. AGRAWAL; D. D. PAWAR
2017-03-01
We studied plane symmetric cosmological model in the presence of quark and strange quark matter with the help of ${f(R, T)}$ theory. To decipher solutions of plane symmetric space-time, we used power law relation between scale factor and deceleration parameter. We considered the special law of variation of Hubble’s parameter proposed by Berman (Nuovo Cimento B74, 182, 1983) which yields constant deceleration parameter. We also discussed the physical behavior of the solutions by using some physical parameters.
Negative Energy Cosmology and the Cosmological Constant
Prokopec, Tomislav
2011-01-01
It is well known that string theories naturally compactify on anti-de Sitter spaces, and yet cosmological observations show no evidence of a negative cosmological constant in the early Universe's evolution. In this letter we present two simple nonlocal modifications of the standard Friedmann cosmology that can lead to observationally viable cosmologies with an initial (negative) cosmological constant. The nonlocal operators we include are toy models for the quantum cosmological backreaction. In Model I an initial quasiperiodic oscillatory epoch is followed by inflation and a late time matter era, representing a dark matter candidate. The backreaction in Model II quickly compensates the negative cosmological term such that the Ricci curvature scalar rapidly approaches zero, and the Universe ends up in a late time radiation era.
Li, Bohua; Shapiro, Paul R.; Rindler-Daller, Tanja
2017-01-01
We consider an alternative to WIMP cold dark matter (CDM), ultralight bosonic dark matter (m≥10-22 eV) described by a complex scalar field (SFDM), of which the comoving particle number density is conserved after particle production during standard reheating (w=p/ρ=0). In a ΛSFDM universe, SFDM starts 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 phase, there is an even earlier phase of stiff-SFDM-domination, during which the expansion rate is higher than in ΛCDM. The transitions between these phases, determined by SFDM particle mass m, and coupling strength λ, of a quartic self-interaction, are therefore constrained by cosmological observables, particularly Neff, the effective number of neutrino species during BBN, and zeq, the redshift of matter-radiation equality. Furthermore, since the homogeneous energy density contributed by the stochastic gravitational wave background (SGWB) from inflation is amplified during the stiff phase, relative to the other components, the SGWB can contribute a radiation-like component large enough to affect these observables. This same amplification makes possible detection of this SGWB at high frequencies by current laser interferometer experiments, e.g., aLIGO/Virgo, eLISA. For SFDM particle parameters that satisfy these cosmological constraints, the amplified SGWB is detectable by aLIGO, for values of tensor-to-scalar ratio r currently allowed by CMB polarization measurements, for a broad range of possible reheat temperatures Tre. For a given r, if SFDM parameters marginally satisfy cosmological constraints (maximizing total SGWB energy density), the SGWB is maximally detectable when modes that reenter the horizon when reheating ends have frequencies in the 10-50 Hz aLIGO band today. For example, if r=0.01, the maximally detectable model for (λ/(mc2)2, m)=(10-18 eV-1cm3, 8×10-20 eV) has Tre=104 GeV, for
General Relativity, Cosmological Constant and Modular Forms
Kraniotis, G V
2001-01-01
Strong field (exact) solutions of the gravitational field equations of General Relativity in the presence of a Cosmological Constant are investigated. In particular, a full exact solution is derived within the inhomogeneous Szekeres-Szafron family of space-time line element with a nonzero Cosmological Constant. The resulting solution connects, in an intrinsic way, General Relativity with the theory of modular forms and elliptic curves and thus to the theory of Taniyama-Shimura.The homogeneous FLRW limit of the above space-time elements is recovered and we solve exactly the resulting Friedmann Robertson field equation with the appropriate matter density for generic values of the Cosmological Constant $ \\Lambda $ and curvature constant $K$. A formal expression for the Hubble constant is derived. The cosmological implications of the resulting non-linear solutions are systematically investigated. Two particularly interesting solutions i) the case of a flat universe $K=0,\\Lambda \
Sanders, Robert H
2016-01-01
The advent of sensitive high-resolution observations of the cosmic microwave background radiation and their successful interpretation in terms of the standard cosmological model has led to great confidence in this model's reality. The prevailing attitude is that we now understand the Universe and need only work out the details. In this book, Sanders traces the development and successes of Lambda-CDM, and argues that this triumphalism may be premature. The model's two major components, dark energy and dark matter, have the character of the pre-twentieth-century luminiferous aether. While there is astronomical evidence for these hypothetical fluids, their enigmatic properties call into question our assumptions of the universality of locally determined physical law. Sanders explains how modified Newtonian dynamics (MOND) is a significant challenge for cold dark matter. Overall, the message is hopeful: the field of cosmology has not become frozen, and there is much fundamental work ahead for tomorrow's cosmologis...
Non-Linearly Interacting Ghost Dark Energy in Brans-Dicke Cosmology
Ebrahimi, E
2016-01-01
In this paper we extend the form of interaction term into the non-linear regime in the ghost dark energy model. A general form of non-linear interaction term is presented and cosmic dynamic equations are obtained. Next, the model is detailed for two special choice of the non-linear interaction term. According to this the universe transits at suitable time ($z\\sim 0.8$) from deceleration to acceleration phase which alleviate the coincidence problem. Squared sound speed analysis revealed that for one class of non-linear interaction term $v_s^2$ can gets positive. This point is an impact of the non-linear interaction term and we never find such behavior in non interacting and linearly interacting ghost dark energy models. Also statefinder parameters are introduced for this model and we found that for one class the model meets the $\\Lambda CDM$ while in the second choice although the model approaches the $\\Lambda CDM$ but never touch that.
Cosmology emerging as the gauge structure of a nonlinear quantum system
Kam, Chon-Fai
2016-01-01
Berry phases and gauge structures in parameter spaces of quantum systems are the foundation of a broad range of quantum effects such as quantum Hall effects and topological insulators. The gauge structures of interacting many-body systems, which often present exotic features, are particularly interesting. While quantum systems are intrinsically linear due to the superposition principle, nonlinear quantum mechanics can arise as an effective theory for interacting systems (such as condensates of interacting bosons). Here we show that gauge structures similar to curved spacetime can arise in nonlinear quantum systems where the superposition principle breaks down. In the canonical formalism of the nonlinear quantum mechanics, the geometric phases of quantum evolutions can be formulated as the classical geometric phases of a harmonic oscillator that represents the Bogoliubov excitations. We find that the classical geometric phase can be described by a de Sitter universe. The fundamental frequency of the harmonic o...
Ageing of the nonlinear optical susceptibility in soft matter
Energy Technology Data Exchange (ETDEWEB)
Ghofraniha, N [SMC-INFM-CNR, c/o Universita di Roma ' La Sapienza' , Piazzale Aldo Moro 2, 00185, Rome (Italy); Conti, C [Research Centre ' Enrico Fermi' , Via Panisperna 89/A, 00184 Rome (Italy); Leonardo, R Di [SOFT-INFM-CNR, c/o Universita di Roma ' La Sapienza' , Piazzale Aldo Moro 2, 00185, Rome (Italy); Ruzicka, B [SOFT-INFM-CNR, c/o Universita di Roma ' La Sapienza' , Piazzale Aldo Moro 2, 00185, Rome (Italy); Ruocco, G [SOFT-INFM-CNR, c/o Universita di Roma ' La Sapienza' , Piazzale Aldo Moro 2, 00185, Rome (Italy)
2007-05-23
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.
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
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...... 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...
Constraining a bulk viscous matter-dominated cosmological model using SNe Ia, CMB and LSS
Avelino, Arturo; Guzmán, F S
2008-01-01
We present and constrain a cosmological model which component is a pressureless fluid with bulk viscosity as an explanation for the present accelerated expansion of the universe. We study the particular model of a constant bulk viscosity coefficient \\zeta_m. The possible values of \\zeta_m are constrained using the cosmological tests of SNe Ia Gold 2006 sample, the CMB shift parameter R from the three-year WMAP observations, the Baryon Acoustic Oscillation (BAO) peak A from the Sloan Digital Sky Survey (SDSS) and the Second Law of Thermodynamics (SLT). It was found that this model is in agreement with the SLT using only the SNe Ia test. However when the model is submitted to the three cosmological tests together (SNe+CMB+BAO) the results are: 1.- the model violates the SLT, 2.- predicts a value of H_0 \\approx 53 km sec^{-1} Mpc^{-1} for the Hubble constant, and 3.- we obtain a bad fit to data with a \\chi^2_{min} \\approx 400 (\\chi^2_{d.o.f.} \\approx 2.2). These results indicate that this model is ruled out by t...
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.
Indian Academy of Sciences (India)
A. Izadi; A. Shojai; M. Nouradini
2013-03-01
We consider tensor–vector theories by varying the space-time–matter coupling constant (varying Einstein velocity) in a spatially flat FRW universe.We examine the dynamics of this model by dynamical system method assuming a CDM background and we find some exact solutions by considering the character of critical points of the theory and their stability conditions. Then we reconstruct the potential (2) and the coupling (2) by demanding a background CDM cosmology. Also we set restrictions on the varying Einstein velocity to solve the horizon problem. This gives a selection rule for choosing the appropriate stable solution. We will see that it is possible to produce the background expansion history () indicated by observations. Finally we will discuss the behavior of the speed of light (E) for those solutions.
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
The HAWC Gamma-Ray Observatory: Dark Matter, Cosmology, and Fundamental Physics
Abeysekara, A U; Alvarez, C; Álvarez, J D; Arceo, R; Arteaga-Velázquez, J C; Solares, H A Ayala; Barber, A S; Baughman, B M; Bautista-Elivar, N; Belmont, E; BenZvi, S Y; Berley, D; Rosales, M Bonilla; Braun, J; Caballero-Lopez, R A; Caballero-Mora, K S; Carramiñana, A; Castillo, M; Cotti, U; Cotzomi, J; de la Fuente, E; De León, C; DeYoung, T; Hernandez, R Diaz; Díaz-Vélez, J C; Dingus, B L; DuVernois, M A; Ellsworth, R W; Fernandez, A; Fiorino, D W; Fraija, N; Galindo, A; Garfias, F; González, L X; González, M M; Goodman, J A; Grabski, V; Gussert, M; Hampel-Arias, Z; Hui, C M; Hüntemeyer, P; Imran, A; Iriarte, A; Karn, P; Kieda, D; Kunde, G J; Lara, A; Lauer, R J; Lee, W H; Lennarz, D; Vargas, H León; Linares, E C; Linnemann, J T; Longo, M; Luna-GarcIa, R; Marinelli, A; Martinez, H; Martinez, O; Martínez-Castro, J; Matthews, J A J; Miranda-Romagnoli, P; Moreno, E; Mostafá, M; Nava, J; Nellen, L; Newbold, M; Noriega-Papaqui, R; Oceguera-Becerra, T; Patricelli, B; Pelayo, R; Pérez-Pérez, E G; Pretz, J; Rivière, C; Rosa-González, D; Salazar, H; Salesa, F; Sanchez, F E; Sandoval, A; Santos, E; Schneider, M; Silich, S; Sinnis, G; Smith, A J; Sparks, K; Springer, R W; Taboada, I; Toale, P A; Tollefson, K; Torres, I; Ukwatta, T N; Villaseñor, L; Weisgarber, T; Westerhoff, S; Wisher, I G; Wood, J; Yodh, G B; Younk, P W; Zaborov, D; Zepeda, A; Zhou, H
2013-01-01
The High-Altitude Water Cherenkov Gamma Ray Observatory (HAWC) is designed to perform a synoptic survey of the TeV sky. The high energy coverage of the experiment will enable studies of fundamental physics beyond the Standard Model, and the large field of view of the detector will enable detailed studies of cosmologically significant backgrounds and magnetic fields. We describe the sensitivity of the full HAWC array to these phenomena in five contributions shown at the 33rd International Cosmic Ray Conference in Rio de Janeiro, Brazil (July 2013).
Nojiri, S; Oikonomou, V K
2016-01-01
We combine the unimodular gravity and mimetic gravity theories into a unified theoretical framework, which is proposed to solve 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, of the perfect fluid with constant equation of state cosmology, of the Type IV singular cosmology and of the $R^2$ inflation cosmology. 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, the graceful exit from inflation problem might exist, we provide a qualita...
CMB and matter power spectra with non-linear dark-sector interactions
vom Marttens, R. F.; Casarini, L.; Hipólito-Ricaldi, W. S.; Zimdahl, W.
2017-01-01
An interaction between dark matter and dark energy, proportional to the product of their energy densities, results in a scaling behavior of the ratio of these densities with respect to the scale factor of the Robertson-Walker metric. This gives rise to a class of cosmological models which deviate from the standard model in an analytically tractable way. In particular, it becomes possible to quantify the role of potential dark-energy perturbations. We investigate the impact of this interaction on the structure formation process. Using the (modified) CAMB code we obtain the CMB spectrum as well as the linear matter power spectrum. It is shown that the strong degeneracy in the parameter space present in the background analysis is considerably reduced by considering Planck data. Our analysis is compatible with the ΛCDM model at the 2σ confidence level with a slightly preferred direction of the energy flow from dark matter to dark energy.
CMB and matter power spectra with non-linear dark-sector interactions
Marttens, R F vom; Hipólito-Ricaldi, W S; Zimdahl, W
2016-01-01
An interaction between dark matter and dark energy, proportional to the product of their energy densities, results in a scaling behavior of the ratio of these densities with respect to the scale factor of the Robertson-Walker metric. This gives rise to a class of cosmological models which deviate from the standard model in an analytically tractable way. In particular, it becomes possible to quantify the role of potential dark-energy perturbations. We investigate the impact of this interaction on the structure formation process. Using the (modified) CAMB code we obtain the CMB spectrum as well as the linear matter power spectrum. It is shown that the strong degeneracy in the parameter space present in the background analysis is considerably reduced by considering \\textit{Planck} data. Our analysis is compatible with the $\\Lambda$CDM model at the $2\\sigma$ confidence level with a slightly preferred direction of the energy flow from dark matter to dark energy.
Axions : Theory and Cosmological Role
Kawasaki, Masahiro; Nakayama, Kazunori
2013-01-01
We review recent developments on axion cosmology. Topics include : axion cold dark matter, axions from topological defects, axion isocurvature perturbation and its non-Gaussianity and axino/saxion cosmology in supersymmetric axion model.
Avelino, Arturo
2008-01-01
We present and constrain a cosmological model where the only component is a pressureless fluid with bulk viscosity as an explanation for the present accelerated expansion of the universe. We study the particular model of a bulk viscosity coefficient proportional to the Hubble parameter. The model is constrained using the SNe Ia Gold 2006 sample, the Cosmic Microwave Background (CMB) shift parameter R, the Baryon Acoustic Oscillation (BAO) peak A and the Second Law of Thermodynamics (SLT). It was found that this model is in agreement with the SLT using only the SNe Ia test. However when the model is constrained using the three cosmological tests together (SNe+CMB+BAO) we found: 1.- The model violates the SLT, 2.- It predicts a value of H_0 \\approx 53 km sec^{-1} Mpc^{-1} for the Hubble constant, and 3.- We obtain a bad fit to data with a \\chi^2_{min} \\approx 532. These results indicate that this model is viable just if the bulk viscosity is triggered in recent times.
The Low Redshift Lyman $\\alpha$ Forest in Cold Dark Matter Cosmologies
Davé, R; Katz, N; Weinberg, D H; Davé, Romeel; Hernquist, Lars; Katz, Neal; Weinberg, David
1999-01-01
We study the physical origin of the low-redshift Lyman alpha forest in hydrodynamic simulations of four CDM cosmologies. Our main conclusions are insensitive to the cosmological model but depend on our assumption that the UV background declines at low redshift. We find that the expansion of the universe drives rapid evolution of dN/dz (the number of absorbers per unit z) at z > 1.7, but that at lower redshift the fading of the UV background counters the influence of expansion, leading to slow evolution. At every redshift, weaker lines come primarily from moderate fluctuations of the diffuse, unshocked IGM, and stronger lines originate in shocked or radiatively cooled gas of higher overdensity. However, the neutral hydrogen column density associated with structures of fixed overdensity drops as the universe expands, so an absorber at z = 0 is dynamically analogous to an absorber with neutral hydrogen column density 10 to 50 times higher at z = 2-3. We find no clear distinction between lines arising in "galaxy ...
Bothun, Greg
2011-10-01
Ever since Aristotle placed us, with certainty, in the Center of the Cosmos, Cosmological models have more or less operated from a position of known truths for some time. As early as 1963, for instance, it was ``known'' that the Universe had to be 15-17 billion years old due to the suspected ages of globular clusters. For many years, attempts to determine the expansion age of the Universe (the inverse of the Hubble constant) were done against this preconceived and biased notion. Not surprisingly when more precise observations indicated a Hubble expansion age of 11-13 billion years, stellar models suddenly changed to produce a new age for globular cluster stars, consistent with 11-13 billion years. Then in 1980, to solve a variety of standard big bang problems, inflation was introduced in a fairly ad hoc manner. Inflation makes the simple prediction that the net curvature of spacetime is zero (i.e. spacetime is flat). The consequence of introducing inflation is now the necessary existence of a dark matter dominated Universe since the known baryonic material could comprise no more than 1% of the necessary energy density to make spacetime flat. As a result of this new cosmological ``truth'' a significant world wide effort was launched to detect the dark matter (which obviously also has particle physics implications). To date, no such cosmological component has been detected. Moreover, all available dynamical inferences of the mass density of the Universe showed in to be about 20% of that required for closure. This again was inconsistent with the truth that the real density of the Universe was the closure density (e.g. Omega = 1), that the observations were biased, and that 99% of the mass density had to be in the form of dark matter. That is, we know the universe is two component -- baryons and dark matter. Another prevailing cosmological truth during this time was that all the baryonic matter was known to be in galaxies that populated our galaxy catalogs. Subsequent
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Wesson, P.S.
1979-10-01
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: 8..pi..Gl/sup 2/ rho/c/sup 2/, 8..pi..Gl/sup 2/ rho/c/sup 4/, and 2 Gm/c/sup 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. (SC)
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...
Inhomogeneous Big Bang Cosmology
Wagh, S M
2002-01-01
In this letter, we outline an inhomogeneous model of the Big Bang cosmology. For the inhomogeneous spacetime used here, the universe originates in the infinite past as the one dominated by vacuum energy and ends in the infinite future as the one consisting of "hot and relativistic" matter. The spatial distribution of matter in the considered inhomogeneous spacetime is {\\em arbitrary}. Hence, observed structures can arise in this cosmology from suitable "initial" density contrast. Different problems of the standard model of Big Bang cosmology are also resolved in the present inhomogeneous model. This inhomogeneous model of the Big Bang Cosmology predicts "hot death" for the universe.
Institute of Scientific and Technical Information of China (English)
Prashant Singh Baghel; Jagdish Prasad Singh
2012-01-01
We consider spatially homogeneous and anisotropic Bianchi type Ⅴ space-time with a bulk viscous fluid source,and time varying gravitational constant G and cosmological term A.The coefficient of bulk viscosity ζ is assumed to be a simple linear function of the Hubble parameter H (i.e.ζ=ζ0 + ζ1H,where ζ0 and ζ1 are constants).The Einstein field equations are solved explicitly by using a law of variation for the Hubble parameter,which yields a constant value of the deceleration parameter.Physical and kinematical parameters of the models are discussed.The models are found to be compatible with the results of astronomical observations.
Lin, David; Rocha, Miguel E.; Primack, Joel R.
2015-01-01
Dark matter halos existing around visible galaxies are important for studies of galaxy formation and evolution. Since dark matter does not interact with light and cannot be observed directly, studies of dark matter halos are advanced by computer simulations. Normally, halos are defined by their virialized regions; however, regions that are non-virialized can still be gravitationally bound, like the collision-bound Milky Way and Andromeda galaxies. Our project is the first comprehensive characterization of gravitationally bound halo structures, their properties, and their evolution. This study found the bound regions surrounding every dark matter halo from a 100 Mpc cube of the Bolshoi Simulation at redshifts 0, 1, and 2. We optimized computation by removing subhalos, implementing a search radius, and parallelizing code across 160 supercomputer cores. Then, we created a mass function, circular velocity function, and correlation function to describe these regions. The evolution of these properties was consistent with predictions from a ΛCDM universe model. We characterized the sizes and shapes of these bound regions across different mass intervals and redshifts. Most bound regions are elongated, although they become more spheroidal with time. The results enable astronomers to predict how dark matter halos behave in non-virialized regions of space and deepen our understanding of galaxy formation.
Constraints on small-scale cosmological perturbations from gamma-ray searches for dark matter
Scott, Pat; Akrami, Yashar
2012-01-01
Events like inflation or phase transitions can produce large density perturbations on very small scales in the early Universe. Probes of small scales are therefore useful for e.g. discriminating between inflationary models. Until recently, the only such constraint came from non-observation of primordial black holes (PBHs), associated with the largest perturbations. Moderate-amplitude perturbations can collapse shortly after matter-radiation equality to form ultracompact minihalos (UCMHs) of dark matter, in far greater abundance than PBHs. If dark matter self-annihilates, UCMHs become excellent targets for indirect detection. Here we discuss the gamma-ray fluxes expected from UCMHs, the prospects of observing them with gamma-ray telescopes, and limits upon the primordial power spectrum derived from their non-observation by the Fermi Large Area Space Telescope.
Cosmological phase transition, baryon asymmetry and dark matter Q-balls
Krylov, E; Rubakov, V
2013-01-01
We consider a mechanism of dark matter production in the course of first order phase transition. We assume that there is an asymmetry between X- and anti-X-particles of dark sector. In particular, it may be related to the baryon asymmetry. We also assume that the phase transition is so strongly first order, that X-particles do not permeate into the new phase. In this case, as the bubbles of old phase collapse, X-particles are packed into Q-balls with huge mass defect. These Q-balls compose the present dark matter. We find that the required present dark matter density is obtained for the energy scale of the theory in the ballpark of 1-10 TeV. As an example we consider a theory with effective potential of one-loop motivated form.
Structure formation in warm dark matter cosmologies: Top-Bottom Upside-Down
Paduroiu, Sinziana; Pfenniger, Daniel
2015-01-01
The damping on the fluctuation spectrum and the presence of thermal velocities as properties of warm dark matter particles like sterile neutrinos imprint a distinct signature found from the structure formation mechanisms to the internal structures of halos. Using warm dark matter simulations we explore these effects on the structure formation for different particle energies and we find that the formation of structure is more complex than originally assumed, a combination of top-down collapse and hierarchical (bottom-up) clustering on multiple scales. The degree on which one scenario is more prominent with respect to the other depends globally on the energy of the particle and locally on the morphology and architecture of the analyzed region. The presence of shells and caustics in warm dark matter haloes is another important effect seen in simulations. Furthermore, we discuss the impact of thermal velocities on the structure formation from theoretical considerations as well as from the analysis of the simulati...
Interaction between Dark Matter and Dark Energy and the Cosmological Coincidence Problem
Directory of Open Access Journals (Sweden)
Kourosh Nozari
2014-01-01
Full Text Available We consider a quintessence model of dark energy inspired by scalar-tensor theories of gravity where the scalar field is nonminimally coupled to gravity and dark matter. By considering exponential potential as self-interaction potential, the stability and existence of the critical points are discussed in details. With nonminimally coupled dark sector with gravity, we obtain scaling solutions to address the coincidence problem by considering complex velocity for dark matter. The statefinder diagnostic shows that the equation of state reaches ΛCDM model in the future.
Concordance cosmology without dark energy
Rácz, Gábor; Dobos, László; Beck, Róbert; Szapudi, István; Csabai, István
2017-07-01
According to the separate universe conjecture, spherically symmetric sub-regions in an isotropic universe behave like mini-universes with their own cosmological parameters. This is an excellent approximation in both Newtonian and general relativistic theories. We estimate local expansion rates for a large number of such regions, and use a scale parameter calculated from the volume-averaged increments of local scale parameters at each time step in an otherwise standard cosmological N-body simulation. The particle mass, corresponding to a coarse graining scale, is an adjustable parameter. This mean field approximation neglects tidal forces and boundary effects, but it is the first step towards a non-perturbative statistical estimation of the effect of non-linear evolution of structure on the expansion rate. Using our algorithm, a simulation with an initial Ωm = 1 Einstein-de Sitter setting closely tracks the expansion and structure growth history of the Λ cold dark matter (ΛCDM) cosmology. Due to small but characteristic differences, our model can be distinguished from the ΛCDM model by future precision observations. Moreover, our model can resolve the emerging tension between local Hubble constant measurements and the Planck best-fitting cosmology. Further improvements to the simulation are necessary to investigate light propagation and confirm full consistency with cosmic microwave background observations.
Bartelmann, Matthias; Berg, Daniel; Kozlikin, Elena; Lilow, Robert; Viermann, Celia
2014-01-01
We use the non-equlibrium statistical field theory for classical particles, recently developed by Mazenko and Das and Mazenko, together with the free generating functional we have previously derived for point sets initially correlated in phase space, to calculate the time evolution of power spectra in the free theory, i.e. neglecting particle interactions. We provide expressions taking linear and quadratic momentum correlations into account. Up to this point, the expressions are general with respect to the free propagator of the microscopic degrees of freedom. We then specialise the propagator to that expected for particles in cosmology treated within the Zel'dovich approximation and show that, to linear order in the momentum correlations, the linear growth of the cosmological power spectrum is reproduced. Quadratic momentum correlations return a first contribution to the non-linear evolution of the power spectrum, for which we derive a simple closed expression valid for arbitrary wave numbers. This expressio...
Classical and quantum cosmology with two perfect fluids: stiff matter and radiation
Alvarenga, F G; Freitas, R C; Gonçalves, S V B
2016-01-01
In this work the homogeneous and isotropic Universe of Friedmann-Robertson-Walker is studied in the presence of two fluids: stiff matter and radiation described by the Schutz's formalism. We obtain to the classic case the behaviour of the scale factor of the universe. For the quantum case the wave packets are constructed and the wave function of the universe is found.
Cosmological and astrophysical signatures of dark matter annihilations into pseudo-Goldstone bosons
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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.
Cosmology beyond the standard model: Multi-component dark matter model
Demiański, M.; Doroshkevich, A. G.
2015-06-01
We show that both the mass and composition of dark matter (DM) particles strongly influence the formation of low mass DM halos. Comparison of theoretical predictions with observations allows us to select the more promising DM models. More details can be found in our paper arXiv:1404.3362.
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
Cosmological solutions with massive gravitons
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Chamseddine, Ali H. [Physics Department, American University of Beirut (Lebanon); Laboratoire de Mathematiques et Physique Theorique CNRS-UMR 6083, Universite de Tours, Parc de Grandmont, 37200 Tours (France); LE STUDIUM, Loire Valley Institute for Advanced Studies, Tours and Orleans (France); I.H.E.S., F-91440 Bures-sur-Yvette (France); Volkov, Mikhail S., E-mail: volkov@lmpt.univ-tours.fr [Laboratoire de Mathematiques et Physique Theorique CNRS-UMR 6083, Universite de Tours, Parc de Grandmont, 37200 Tours (France)
2011-10-25
We present solutions describing spatially closed, open, or flat cosmologies in the massive gravity theory within the recently proposed tetrad formulation. We find that the effect of the graviton mass is equivalent to introducing to the Einstein equations a matter source that can consist of several different matter types - a cosmological term, quintessence, gas of cosmic strings, and non-relativistic cold matter.
INTRAGROUP DARK MATTER DISTRIBUTION IN SMALL GROUPS OF HALOS IN A ACDM COSMOLOGY
Directory of Open Access Journals (Sweden)
H. Aceves
2015-01-01
Full Text Available Se estudia la distribución de materia oscura intragrupal en pequeños grupos de halos oscuros de tamaño galáctico en una cosmología ACDM. Estos grupos oscuros son identificados utilizando un criterio físico, y pueden ser representativos de pequeños grupos de galaxias. Cuantificamos la cantidad de materia oscura intragrupal y caracterizamos su distribución. Encontramos que las asociaciones compactas de halos, y las intermedias y mucho menos compactas, tienen perfiles de masa oscura algo planos, con pendientes logarítmicas de γ ≈ 0 y ≈ —0.2, respectivamente. Concluimos entonces que la materia oscura intragrupo en estos sistemas no sigue la misma distribución que la de los halos galácticos. En grupos intermedios u holgados de halos la materia intragrupal es ≲ 50%, mientras que en los compactos es ≲ 20% dentro del radio del grupo.
INTRAGROUP DARK MATTER DISTRIBUTION IN SMALL GROUPS OF HALOS IN A ΛCDM COSMOLOGY
Directory of Open Access Journals (Sweden)
H. Aceves
2015-01-01
Full Text Available Se estudia la distribución de materia oscura intragrupal en pequeños grupos de halos oscuros de tamaño galáctico en una cosmología ACDM. Estos grupos oscuros son identificados utilizando un criterio físico, y pueden ser representativos de pequeños grupos de galaxias. Cuantificamos la cantidad de materia oscura intragrupal y caracterizamos su distribución. Encontramos que las asociaciones compactas de halos, y las intermedias y mucho menos compactas, tienen perfiles de masa oscura algo planos, con pendientes logarítmicas de γ ≈ 0 y ≈ —0.2, respectivamente. Concluimos entonces que la materia oscura intragrupo en estos sistemas no sigue la misma distribución que la de los halos galácticos. En grupos intermedios u holgados de halos la materia intragrupal es ≲ 50%, mientras que en los compactos es ≲ 20% dentro del radio del grupo.
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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
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.
Energy Technology Data Exchange (ETDEWEB)
Ferrantelli, Andrea [University of Helsinki and Helsinki Institute of Physics, P.O.Box 64, FIN-00014 University of Helsinki (Finland); McDonald, John, E-mail: andrea.ferrantelli@helsinki.fi, E-mail: j.mcdonald@lancaster.ac.uk [Cosmology and Astroparticle Physics Group, University of Lancaster, Lancaster LA1 4YB (United Kingdom)
2010-02-01
We consider the dynamics of the supersymmetry-breaking scalar field and the production of dark matter gravitinos via its decay in a gauge-mediated supersymmetry breaking model with metastable vacuum. We find that the scalar field amplitude and gravitino density are extremely sensitive to the parameters of the hidden sector. For the case of an O'Raifeartaigh sector, we show that the observed dark matter density can be explained by gravitinos even for low reheating temperatures T{sub R}∼<10GeV. Such low reheating temperatures may be implied by detection of the NLSP at the LHC if its thermal freeze-out density is in conflict with BBN.
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Faraggi, A.E.
1996-08-01
Superstring phenomenology aims at achieving two goals. The first is to reproduce the observed physics of the Standard Model. The second is to identify experimental signatures of superstring unification which, if observed, will provide further evidence for the validity of superstring theory. I discuss such potential signatures of superstring unification. I propose that proton lifetime constraints imply that the Standard Model gauge group must be obtained directly at the string level. In this case the unifying gauge group, for example SO(10), is broken to the Standard Model gauge group by ``Wilson lines``. The symmetry breaking by ``Wilson line`` has important implications. It gives rise to exotic massless states which cannot fit into multiplets of the original unifying gauge group. This is an important feature because it results in conservation laws which forbid the interaction of the exotic ``Wilsonian`` states with the Standard Model states. The ``Wilsonian`` matter states then have important phenomenological implications. I discuss two such implications: exotic ``Wilsonian`` states as dark matter candidates and ``Wilsonian`` matter as the messenger sector in gauge mediated dynamical SUSY breaking scenarios.
On the hypothesis that cosmological dark matter is composed of ultra-light bosons
Hui, Lam; Tremaine, Scott; Witten, Edward
2016-01-01
An intriguing alternative to cold dark matter (CDM) is that the dark matter is a light ( $m \\sim 10^{-22}$ eV) boson having a de Broglie wavelength $\\lambda \\sim 1$ kpc, often called fuzzy dark matter (FDM). We describe the arguments from particle physics that motivate FDM, review previous work on its astrophysical signatures, and analyze several unexplored aspects of its behavior. In particular, (i) FDM halos smaller than about $10^7 (m/10^{-22} {\\rm eV})^{-3/2} M_\\odot$ do not form. (ii) FDM halos are comprised of a core that is a stationary, minimum-energy configuration called a "soliton", surrounded by an envelope that resembles a CDM halo. (iii) The transition between soliton and envelope is determined by a relaxation process analogous to two-body relaxation in gravitating systems, which proceeds as if the halo were composed of particles with mass $\\sim \\rho\\lambda^3$ where $\\rho$ is the halo density. (iv) Relaxation may have substantial effects on the stellar disk and bulge in the inner parts of disk ga...
Marsh, David J E
2015-01-01
Axions comprise a broad class of particles that can play a major role in explaining the unknown aspects of cosmology. They are also extraordinarily well-motivated within high energy physics, and so axion cosmology offers us a unique view onto these theories. I present a comprehensive and pedagogical view on the cosmology and astrophysics of axion-like particles, starting from inflation and progressing via the CMB and structure formation up to the present-day Universe. I briefly review the motivation and models for axions in particle physics and string theory. The primary focus is on the population of ultralight axions created via vacuum realignment, and its role as a dark matter (DM) candidate with distinctive phenomenology. Cosmological observations place robust constraints on the axion mass and relic density in this scenario, and I review where such constraints come from. I next cover aspects of galaxy formation with axion DM, and ways this can be used to further search for evidence of axions. An absolute l...
Cosmological implications of Geometrothermodynamics
Luongo, Orlando
2013-01-01
We use the formalism of Geometrothermodynamics to derive a series of fundamental equations for thermodynamic systems. It is shown that all these fundamental equations can be used in the context of relativistic cosmology to derive diverse scenarios which include the standard cosmological model, a unified model for dark energy and dark matter, and an effective inflationary model.
Cosmological Implications of Geometrothermodynamics
Luongo, O.; Quevedo, H.
2015-01-01
We use the formalism of Geometrothermodynamics to derive a series of fundamental equations for thermodynamic systems. It is shown that all these fundamental equations can be used in the context of relativistic cosmology to derive diverse scenarios which include the standard cosmological model, a unified model for dark energy and dark matter, and an effective inflationary model.
Helbig, Phillip
2015-01-01
The $m$-$z$ relation for type Ia supernovae is one of the key pieces of evidence supporting the cosmological `concordance model' with $\\lambda_0 \\approx 0.7$ and $\\Omega_0 \\approx 0.3$. However, it is well known that the $m$-$z$ relation depends not only on $\\lambda_0$ and $\\Omega_0$ (with $H_0$ as a scale factor) but also on the density of matter along the line of sight, which is not necessarily the same as the large-scale density. I investigate to what extent the measurement of $\\lambda_0$ and $\\Omega_0$ depends on this density when it is characterized by the parameter $\\eta$ ($0 \\le \\eta \\le 1$), which describes the ratio of density along the line of sight to the overall density. I also discuss what constraints can be placed on $\\eta$, both with and without constraints on $\\lambda_0$ and $\\Omega_0$ in addition to those from the $m$-$z$ relation for type~Ia supernovae.
Ahn, Kyungjin
2016-01-01
We study the dynamical effect of relative velocities between dark matter and baryonic fluids, which remained supersonic after the epoch of recombination. The impact of this supersonic motion on the formation of cosmological structures was first formulated by Tseliakhovich & Hirata (2010), in terms of the linear theory of small-scale fluctuations coupled to large-scale, relative velocities in mean-density regions. In their formalism, they limited the large-scale density environment to be those of the global mean density. We improve on their formulation by allowing variation in the density environment as well as the relative velocities. This leads to a new type of coupling between large-scale and small-scale modes. We find that the small-scale fluctuation grows in a biased way: faster in the overdense environment and slower in the underdense environment. We also find that the net effect on the global power spectrum of the density fluctuation is to boost its overall amplitude from the prediction by Tseliakho...
Verma, Murli Manohar
2012-01-01
We propose a model of the evolution of the tachyonic scalar field over two phases in the universe. The field components do not interact in phase I, while in the subsequent phase II, they change flavours due to relative suppression of the radiation contribution. In phase II, we allow them to interact mutually with time-independent perturbation in their equations of state, as Shifted Cosmological Parameter (SCP) and Shifted Dust Matter (SDM). We determine the solutions of their scaling with the cosmic redshift in both phases. We further suggest the normalized Hubble function diagnostic, which, together with the low- and high-redshift $H(z)$ data and the concordance values of the present density parameters from the CMBR, BAO statistics etc., constrains the strength of interaction, by imposing the viable conditions to break degeneracy in 3-parameter $(\\gamma, \\varepsilon, \\dot{\\phi}^2)$ space. The range of redshifts $(z=0.1$ to $z=1.75)$ is chosen to highlight the role of interaction during structure formation, a...
Sussman, R A; Sussman, Roberto A.; Hernandez, Xavier
2003-01-01
We examine isothermal dark matter halos in hydrostatic equilibrium with a cosmological constant Lambda =Omega_\\Lambda rho_{crit}c^2, where Omega_\\Lambda=0.7, and rho_{crit} is the present value of the critical density with h=0.65. The Newtonian limit of General Relativity yields equilibrium equations that are different from those arising by merely coupling an ``isothermal sphere'' to the Lambda-field within a Newtonian framework. The conditions for the existence and stability of circular geodesic orbits show the existence of (I) an ``isothermal region'' (0r_1) dominated by the Lambda-field, where the Newtonian potential oscillates and circular orbits exist in disconnected patches of the domain of r; (III) a ``transition region'' (r_20.008 M_\\odot {pc}^3, in agreement with rotation curve studies of dwarf galaxies. Since r_2 marks the largest radius of a stable circular orbit, it provides a ``cut off'' radius. For current estimates of rho_c and velocity dispersion of galactic structures, this is around five tim...
Keung Chan, Tsang; Keres, Dusan; Oñorbe, Jose; Hopkins, Philip F.; Muratov, Alexander; Faucher-Giguere, Claude-Andre; Quataert, Eliot
2016-06-01
We study the distribution of cold dark matter (CDM) in cosmological simulations from the FIRE (Feedback In Realistic Environments) project, which incorporates explicit stellar feedback in the multi-phase ISM, with energetics from stellar population models. We find that stellar feedback, without ``fine-tuned'' parameters, greatly alleviates small-scale problems in CDM. Feedback causes bursts of star formation and outflows, altering the DM distribution. As a result, the inner slope of the DM halo profile (α) shows a strong mass dependence: profiles are shallow at Mh ˜ 1010-1011 M⊙ and steepen at higher/lower masses. The resulting core sizes and slopes are consistent with observations. Because the star formation efficiency, Ms/Mh is strongly halo mass dependent, a rapid change in α occurs around Mh ˜1010M⊙, (Ms˜106-107M⊙) as sufficient feedback energy becomes available to perturb the DM. Large cores are not established during the period of rapid growth of halos because of ongoing DM mass accumulation. Instead, cores require several bursts of star formation after the rapid buildup has completed. Stellar feedback dramatically reduces circular velocities in the inner kpc of massive dwarfs; this could be sufficient to explain the ``Too Big To Fail'' problem without invoking non-standard DM. Finally, feedback and baryonic contraction in Milky Way-mass halos produce DM profiles slightly shallower than the Navarro-Frenk-White profile, consistent with the normalization of the observed Tully-Fisher relation.
Energy Technology Data Exchange (ETDEWEB)
Haro, Jaume; Amorós, Jaume, E-mail: jaime.haro@upc.edu, E-mail: jaume.amoros@upc.edu [Departament de Matemàtica Aplicada I, Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain)
2014-12-01
We consider the matter bounce scenario in F(T) gravity and Loop Quantum Cosmology (LQC) for phenomenological potentials that at early times provide a nearly matter dominated Universe in the contracting phase, having a reheating mechanism in the expanding or contracting phase, i.e., being able to release the energy of the scalar field creating particles that thermalize in order to match with the hot Friedmann Universe, and finally at late times leading to the current cosmic acceleration. For these potentials, numerically solving the dynamical perturbation equations we have seen that, for the particular F(T) model that we will name teleparallel version of LQC, and whose modified Friedmann equation coincides with the corresponding one in holonomy corrected LQC when one deals with the flat Friedmann-Lemaître-Robertson-Walker (FLRW) geometry, the corresponding equations obtained from the well-know perturbed equations in F(T) gravity lead to theoretical results that fit well with current observational data. More precisely, in this teleparallel version of LQC there is a set of solutions which leads to theoretical results that match correctly with last BICEP2 data, and there is another set whose theoretical results fit well with Planck's experimental data. On the other hand, in the standard holonomy corrected LQC, using the perturbed equations obtained replacing the Ashtekar connection by a suitable sinus function and inserting some counter-terms in order to preserve the algebra of constrains, the theoretical value of the tensor/scalar ratio is smaller than in the teleparallel version, which means that there is always a set of solutions that matches with Planck's data, but for some potentials BICEP2 experimental results disfavours holonomy corrected LQC.
Beyond the $\\Lambda$CDM cosmology: complex composition of dark matter
Demianski, M.; Doroshkevich, A.
2014-01-01
The mass and composition of dark matter (DM) particles and the shape and damping scales of the power spectrum of density perturbations can be estimated from recent observations of the DM dominated relaxed objects -- dwarf galaxies and clusters of galaxies. We confirm that the observed velocity dispersion of dSph galaxies agrees with the possible existence of DM particles with mass $m_w\\sim 15 - 20keV$. More complex analysis utilizes the well known semi analytical model of formation of DM halo...
Evolutions of matter-wave bright soliton with spatially modulated nonlinearity
Institute of Scientific and Technical Information of China (English)
Yongshan Cheng; Fei Liu
2009-01-01
The evolution characteristics of a matter-wave bright soliton are investigated by means of the variational approach in the presence of spatially varying nonlinearity.It is found that the atom density envelope of the soliton is changed as a result of the spatial variation of the s-wave scattering length.The stable soliton can exist in appropriate initial conditions.The movement of the soliton depends on the sign and value of the coefficient of spatially modulated nonlinearity.These theoretical predictions are confirmed by the full numerical simulations of the one-dimensional Gross-Pitaevskii equation.
Non-linear clustering during the BEC dark matter phase transition
de Freitas, Rodolfo C
2015-01-01
Spherical collapse of the Bose-Einstein Condensate (BEC) dark matter model is studied. The evolution of perturbed quantities like the density of the collapsed region and its expansion rate are calculated for two scenarios. Firstly, we consider the case of a sharp phase transition (which happens when the critical temperature is reached) from the normal dark matter state to the condensate one. In the second case studied we consider a smooth first order phase transition where there is a continuous conversion of "normal" dark matter to the BEC phase. We calculate in detail the perturbative quantities at nonlinear level presenting numerical results for the physics of the collapse for a wide range of the model's space parameter. The model is properly compared to the standard dark matter scenario.
Brax, Philippe
2016-01-01
We investigate scalar-tensor theories where matter couples to the scalar field via a kinetically dependent conformal coupling. These models can be seen as the low-energy description of invariant field theories under a global Abelian symmetry. The scalar field is then identified with the Goldstone mode of the broken symmetry. It turns out that the properties of these models are very similar to the ones of ultralocal theories where the scalar-field value is directly determined by the local matter density. This leads to a complete screening of the fifth force in the Solar System and between compact objects, through the ultralocal screening mechanism. On the other hand, the fifth force can have large effects in extended structures with large-scale density gradients, such as galactic halos. Interestingly, it can either amplify or damp Newtonian gravity, depending on the model parameters. We also study the background cosmology and the linear cosmological perturbations. The background cosmology is hardly different f...
Holland, Jonathan
2014-01-01
A new approach to cosmology and space-time is developed, which emphasizes the description of the matter degrees of freedom of Einstein's theory of gravity by a family of K\\"ahler-Einstein Fano manifolds.
Non-linear power spectra of dark and luminous matter in halo model of structure formation
Kulinich, Yurij; Apunevych, Stepan
2012-01-01
The paper represents a comprehensive treatment of late stages of large-scale structure evolution within the framework of halo model. A number of modifications to basic theory are suggested. We have engineered simple yet accurate approximation to relate the amplitude of non-linear spherical density perturbation to the one of the linear. The theory for final stages of spherical overdensity evolution is revised in order to re-evaluate the dependences of collapse and critical overdensity parameters, $\\delta_{col}$, $\\delta_{ta}$ and $\\delta_{min}$, on redshift and other cosmological parameters. A new technique is proposed for straightforward computation of halo concentration parameter, $c$, without need to evaluate the $z_{col}$. Validity of the technique is proved for a number of $\\Lambda$CDM and $\\Lambda$WDM cosmologies. The parameters for Sheth-Tormen mass function are estimated, as well as new approximation is constructed for the dependence of subhalo mass function on initial power spectrum. The modified and ...
Coherent combs of anti-matter from nonlinear electron-positron pair creation
Krajewska, K
2014-01-01
Electron-positron pair creation in collisions of a modulated laser pulse with a high-energy photon (nonlinear Breit-Wheeler process) is studied by means of strong-field quantum electrodynamics. It is shown that the driving pulse modulations lead to appearance of comb structures in the energy spectra of produced positrons (electrons). It is demonstrated that these combs result from a coherent enhancement of probability amplitudes of pair creation from different modulations of the laser pulse. Thus, resembling the Young-double slit experiment for anti-matter (matter) waves.
Simulations of solitonic core mergers in ultra-light axion dark matter cosmologies
Schwabe, Bodo; Engels, Jan F
2016-01-01
Using three-dimensional simulations, we study the dynamics and final structure of merging solitonic cores predicted to form in ultra-light axion dark matter halos. The classical, Newtonian equations of motion of a self-gravitating scalar field are described by the Schr\\"odinger-Poisson equations. We investigate mergers of ground state (boson star) configurations with varying mass ratios, relative phases, orbital angular momenta and initial separation with the primary goal to understand the mass loss of the emerging core by gravitational cooling. Previous results showing that the final density profiles have solitonic cores and NFW-like tails are confirmed. In binary mergers, the final core mass does not depend on initial phase difference or angular momentum and only depends on mass ratio, total initial mass, and total energy of the system. For non-zero angular momenta, the otherwise spherical cores become rotating ellipsoids. The results for mergers of multiple cores are qualitatively identical.
Simulations of solitonic core mergers in ultralight axion dark matter cosmologies
Schwabe, Bodo; Niemeyer, Jens C.; Engels, Jan F.
2016-08-01
Using three-dimensional simulations, we study the dynamics and final structure of merging solitonic cores predicted to form in ultralight axion dark matter halos. The classical, Newtonian equations of motion of a self-gravitating scalar field are described by the Schrödinger-Poisson equations. We investigate mergers of ground state (boson star) configurations with varying mass ratios, relative phases, orbital angular momenta and initial separation with the primary goal to understand the mass loss of the emerging core by gravitational cooling. Previous results showing that the final density profiles have solitonic cores and Navarro-Frenk-White-like tails are confirmed. In binary mergers, the final core mass does not depend on initial phase difference or angular momentum and only depends on mass ratio, total initial mass, and total energy of the system. For nonzero angular momenta, the otherwise spherical cores become rotating ellipsoids. The results for mergers of multiple cores are qualitatively identical.
Nonlinear quantum optics in the (ultra)strong light-matter coupling
Sánchez-Burillo, Eduardo; García-Ripoll, Juan José; Martín-Moreno, Luis; Zueco, David
2014-01-01
The propagation of $N$ photons in one dimensional waveguides coupled to $M$ qubits is discussed, both in the strong and ultrastrong qubit-waveguide coupling. Special emphasis is placed on the characterisation of the nonlinear response and its linear limit for the scattered photons as a function of $N$, $M$, qubit inter distance and light-matter coupling. The quantum evolution is numerically solved via the Matrix Product States technique. Both the time evolution for the field and qubits is com...
Fardad, Shima; Mills, Matthew S; Zhang, Peng; Man, Weining; Chen, Zhigang; Christodoulides, D N
2013-09-15
We demonstrate optical interactions between stable self-trapped optical beams in soft-matter systems with pre-engineered saturable self-focusing optical nonlinearities. Our experiments, carried out in dilute suspensions of particles with negative polarizabilities, show that optical beam interactions can vary from attractive to repulsive, or can display an energy exchange depending on the initial relative phases. The corresponding observations are in good agreement with theoretical predictions.
Cosmological Reflection of Particle Symmetry
Maxim Khlopov
2016-01-01
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 symmetr...
Brane cosmology in teleparallel gravity
Atazadeh, K
2014-01-01
We consider cosmology of brane-world scenario in the frame work of teleparallel gravity in that way 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.
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.
Lagrangian perturbations and the matter bispectrum I: fourth-order model for non-linear clustering
Energy Technology Data Exchange (ETDEWEB)
Rampf, Cornelius [Institut für Theoretische Teilchenphysik und Kosmologie, RWTH Aachen, Physikzentrum RWTH-Melaten, D-52056 Aachen (Germany); Buchert, Thomas, E-mail: rampf@physik.rwth-aachen.de, E-mail: buchert@obs.univ-lyon1.fr [Université de Lyon, Observatoire de Lyon, Centre de Recherche Astrophysique de Lyon, CNRS UMR 5574: Université Lyon 1 and École Normale Supérieure de Lyon, 9 avenue Charles André, F-69230 Saint-Genis-Laval (France)
2012-06-01
We investigate the Lagrangian perturbation theory of a homogeneous and isotropic universe in the non-relativistic limit, and derive the solutions up to the fourth order. These solutions are needed for example for the next-to-leading order correction of the (resummed) Lagrangian matter bispectrum, which we study in an accompanying paper. We focus on flat cosmologies with a vanishing cosmological constant, and provide an in-depth description of two complementary approaches used in the current literature. Both approaches are solved with two different sets of initial conditions — both appropriate for modelling the large-scale structure. Afterwards we consider only the fastest growing mode solution, which is not affected by either of these choices of initial conditions. Under the reasonable approximation that the linear density contrast is evaluated at the initial Lagrangian position of the fluid particle, we obtain the nth-order displacement field in the so-called initial position limit: the nth order displacement field consists of 3(n-1) integrals over n linear density contrasts, and obeys self-similarity. Then, we find exact relations between the series in Lagrangian and Eulerian perturbation theory, leading to identical predictions for the density contrast and the peculiar-velocity divergence up to the fourth order.
Beyond the $\\Lambda$CDM cosmology: complex composition of dark matter
Demianski, M
2014-01-01
The mass and composition of dark matter (DM) particles and the shape and damping scales of the power spectrum of density perturbations can be estimated from recent observations of the DM dominated relaxed objects -- dwarf galaxies and clusters of galaxies. We confirm that the observed velocity dispersion of dSph galaxies agrees with the possible existence of DM particles with mass $m_w\\sim 15 - 20keV$. More complex analysis utilizes the well known semi analytical model of formation of DM halos in order to describe the basic properties of corresponding objects and to estimate their redshifts of formation. For the DM halos this redshift is determined by their masses and the initial power spectrum of density perturbations. This correlation allows us to partly reconstruct the small scale spectrum of perturbations. We consider the available sample of suitable observed objects that includes $\\sim 40$ DM dominated galaxies and $\\sim 40$ clusters of galaxies and we show that the observed characteristics of these obje...
MOND cosmology from holographic principle
Zhang, Hongsheng
2011-01-01
We derive the MOND cosmology which is uniquely corresponding to the original MOND in galaxies via holographic approach of gravity. It inherits the key merit of MOND, that is, it reduces the byronic matter and mysterious non-byronic dark matter (dark matter for short) in the standard cosmology into byronic matter only. For the first time we derive the critical parameter in MOND, i.e., the transition acceleration $a_c$ on cosmological scale. We thus solve the long-standing coincidence problem $a_c\\sim cH_{0}$. More interestingly, a term like age-graphic dark energy emerges naturally. In the frame of this MOND cosmology, we only need byronic matter to describe both dark matter and dark energy in standard cosmology.
THE CONVERGENCE OF PARTICLE-IN-CELL SCHEMES FOR COSMOLOGICAL DARK MATTER SIMULATIONS
Energy Technology Data Exchange (ETDEWEB)
Myers, Andrew; Colella, Phillip; Van Straalen, Brian, E-mail: ATMyers@lbl.gov [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States)
2016-01-10
Particle methods are a ubiquitous tool for solving the Vlasov–Poisson equation in comoving coordinates, which is used to model the gravitational evolution of dark matter (DM) in an expanding universe. However, these methods are known to produce poor results on idealized test problems, particularly at late times, after the particle trajectories have crossed. To investigate this, we have performed a series of one- and two-dimensional “Zel’dovich pancake” calculations using the popular particle-in-cell (PIC) method. We find that PIC can indeed converge on these problems provided that the following modifications are made. The first modification is to regularize the singular initial distribution function by introducing a small but finite artificial velocity dispersion. This process is analogous to artificial viscosity in compressible gas dynamics, and, as with artificial viscosity, the amount of regularization can be tailored so that its effect outside of a well-defined region—in this case, the high-density caustics—is small. The second modification is the introduction of a particle remapping procedure that periodically reexpresses the DM distribution function using a new set of particles. We describe a remapping algorithm that is third-order accurate and adaptive in phase space. This procedure prevents the accumulation of numerical errors in integrating the particle trajectories from growing large enough to significantly degrade the solution. Once both of these changes are made, PIC converges at second order on the Zel’dovich pancake problem, even at late times, after many caustics have formed. Furthermore, the resulting scheme does not suffer from the unphysical, small-scale “clumping” phenomenon known to occur on the pancake problem when the perturbation wavevector is not aligned with one of the Cartesian coordinate axes.
Hinterbichler, Kurt; Levy, Aaron; Matas, Andrew
2011-01-01
The symmetron is a scalar field associated with the dark sector whose coupling to matter depends on the ambient matter density. The symmetron is decoupled and screened in regions of high density, thereby satisfying local constraints from tests of gravity, but couples with gravitational strength in regions of low density, such as the cosmos. In this paper we derive the cosmological expansion history in the presence of a symmetron field, tracking the evolution through the inflationary, radiation- and matter-dominated epochs, using a combination of analytical approximations and numerical integration. For a broad range of initial conditions at the onset of inflation, the scalar field reaches its symmetry-breaking vacuum by the present epoch, as assumed in the local analysis of spherically-symmetric solutions and tests of gravity. For the simplest form of the potential, the energy scale is too small for the symmetron to act as dark energy, hence we must add a cosmological constant to drive late-time cosmic acceler...
Energy Technology Data Exchange (ETDEWEB)
Chimento, L P; Forte, M [Physics Department, UBA, 1428 Buenos Aires (Argentina); Devecchi, F P; Kremer, G M; Ribas, M O; Samojeden, L L, E-mail: kremer@fisica.ufpr.br, E-mail: devecchi@fisica.ufpr.br, E-mail: chimento@df.uba.ar [Physics Department, UFPR, 81531-990 Curitiba (Brazil)
2011-07-08
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.
Vacaru, Sergiu I
2015-01-01
We re-investigate how generic off-diagonal cosmological solutions depending, in general, on all spacetime coordinates can be constructed in massive and f-modified gravity using the anholonomic frame deformation method. There are constructed new classes of locally anisotropic and (in) homogeneous cosmological metrics with open and closed spatial geometries. By resorting such solutions, we show that they describe the late time acceleration due to effective cosmological terms induced by nonlinear off-diagonal interactions, possible modifications of the gravitational action and graviton mass. The cosmological metrics and related St\\" uckelberg fields are constructed in explicit form up to nonholonomic frame transforms of the Friedmann-Lama\\^{\\i}tre-Robertson-Walker (FLRW) coordinates. The solutions include matter, graviton mass and other effective sources modelling nonlinear gravitational and matter fields interactions with polarization of physical constants and deformations of metrics, which may explain dark ene...
Bojowald, Martin
1999-01-01
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...
Fabris, J C; Rodrigues, D C; Batista, C E M; Daouda, M H
2012-01-01
We review the difficulties of the generalized Chaplygin gas model to fit observational data, due to the tension between background and perturbative tests. We argue that such issues may be circumvented by means of a self-interacting scalar field representation of the model. However, this proposal seems to be successful only if the self-interacting scalar field has a non-canonical form. The latter can be implemented in Rastall's theory of gravity, which is based on a modification of the usual matter conservation law. We show that, besides its application to the generalized Chaplygin gas model, other cosmological models based on Rastall's theory have many interesting and unexpected new features.
An effective description of dark matter and dark energy in the mildly non-linear regime
Lewandowski, Matthew; Senatore, Leonardo
2016-01-01
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 en...
Post-Newtonian cosmological models
Sanghai, Viraj A A
2015-01-01
We construct a framework to probe the effect of non-linear structure formation on the large-scale expansion of the universe. We take a bottom-up approach to cosmological modelling by splitting our universe into cells. The matter content within each cell is described by the post-Newtonian formalism. We assume that most of the cell is in the vicinity of weak gravitational fields, so that it can be described using a perturbed Minkowski metric. Our cells are patched together using the Israel junction conditions. We impose reflection symmetry across the boundary of these cells. This allows us to calculate the equation of motion for the boundary of the cell and, hence, the expansion rate of the universe. At Newtonian order, we recover the standard Friedmann-like equations. At post-Newtonian orders, we obtain a correction to the large-scale expansion of the universe. Our framework does not depend on the process of averaging in cosmology. As an example, we use this framework to investigate the cosmological evolution ...
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.
Nonlinear Dynamics of Soft-Matter: Continuum Mechanics in the Classroom
Dennin, Michael
2005-03-01
Recent efforts in soft-condensed matter physics has generated a renewed interest in the fundamental physics of continuum systems. There has been a recognition that a wide variety of systems, from glasses to foams to granular material, exhibit similar behavior with regard to their dynamics. Even under conditions of external driving, these systems are often ``jammed''. In other words, they exhibit a solid like response to the external driving. With sufficient driving force, there is a transition to a flowing state as the system ''unjams''. This flowing state is generally comprised of nonlinear rearrangements of particles within the system. The question has been raised as to whether or not this represents a general new state of matter, or if the details of each individual system is relevant. At the same time, the interest in the response of complex fluids, such as foams and granular matter, that are composed of mesoscopic, or even macrosopic, sized ``particles'' (such as sand grains), has raised interesting questions concerning the application of continuum mechanics to these systems. Both the nonlinear response of these materials and the application of continuum mechanics raise fundamental physics questions that are generally not covered in typical undergraduate (or even graduate) curricula. This talk will not only review some of the important questions in this field, but also present suggestions as to its integration into the undergraduate curriculum.
Nakamura, Kouji
2008-01-01
Some formulae for the perturbations of the matter fields are summarized within the framework of the second-order gauge-invariant cosmological perturbation theory in a four dimensional homogeneous isotropic universe, which is developed in the papers [K. Nakamura, Prog. Theor. Phys. {\\bf 117} (2005), 17.]. We derive the formulae for the perturbations of the energy momentum tensors and equations of motion in the cases of a perfect fluid, an imperfect fluid, and a signle scalar field, and show that all equations are derived in terms of gauge-invariant variables without any gauge fixing.
Energy Technology Data Exchange (ETDEWEB)
Moraes, P.H.R.S. [Divisao de Astrofisica, INPE-Instituto Nacional de Pesquisas Espaciais, Sao Jose dos Campos, SP (Brazil)
2015-04-01
In this work, I present exact cosmological solutions from Wesson's induced matter model applied to a general 5D metric in f(R,T) theory of gravity. The non-conservation of the energy-momentum tensor, predicted by f(R,T) theory, allows the derivation of a relation that describes the time evolution of the extra coordinate, revealing its compactification. It is shown that such a compactification could induce the effects of an accelerated expansion in the observable universe. (orig.)
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
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......The absorption of a single photon that excites a quantum system from a low to a high energy level is an elementary process of light-matter interaction, and a route towards realizing pure single-photon absorption has both fundamental and practical implications in quantum technology. Due to nonlinear...... 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...
Man, Weining; Fardad, Shima; Zhang, Ze; Prakash, Jai; Lau, Michael; Zhang, Peng; Heinrich, Matthias; Christodoulides, Demetrios N; Chen, Zhigang
2013-11-22
We demonstrate a new class of synthetic colloidal suspensions capable of exhibiting negative polarizabilities, and observe for the first time robust propagation and enhanced transmission of self-trapped light over long distances that would have been otherwise impossible in conventional suspensions with positive polarizabilities. Such light penetration through the strong scattering environment is attributed to the interplay between optical forces and self-activated transparency effects while no thermal effect is involved. By judiciously mixing colloidal particles of both negative and positive polarizabilities, we show that the resulting nonlinear response of these systems can be fine-tuned. Our experimental observations are in agreement with theoretical analysis based on a thermodynamic model that takes into account particle-particle interactions. These results may open up new opportunities in developing soft-matter systems with engineered optical nonlinearities.
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.
Static black holes in equilibrium with matter: nonlinear equation of state
Zaslavskii, Oleg B
2010-01-01
We consider a spherically symmetric black hole in equilibrium with surrounding classical matter that is characterized by a nonlinear dependence of the radial pressure p_{r} on the density {\\rho}. We examine under which requirements such an equilibrium is possible. It is shown that if the radial and transverse pressures are equal (Pascal perfect fluid), equation of state should be approximately linear near the horizon. The corresponding restriction on ((dp_{r})/(d{\\rho})) is a direct generalization of the result, previously found for an exactly linear equation of state. In the anisotropic case there is no restriction on equation of state but the horizon should be simple (nondegenerate).
Kehagias, Alex
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 both scalar and tensor degrees of freedom which may exist at null infinity and perturb the asymptotic d...
Cosmology and particle physics
Turner, Michael S.
1988-01-01
The interplay between cosmology and elementary particle physics is discussed. The standard cosmology is reviewed, concentrating on primordial nucleosynthesis and discussing how the standard cosmology has been used to place constraints on the properties of various particles. Baryogenesis is discussed, showing how a scenario in which the B-, C-, and CP-violating interactions in GUTs provide a dynamical explanation for the predominance of matter over antimatter and for the present baryon-to-photon ratio. It is shown how the very early dynamical evolution of a very weakly coupled scalar field which is initially displaced from the minimum of its potential may explain a handful of very fundamental cosmological facts which are not explained by the standard cosmology.
Testing loop quantum cosmology
Wilson-Ewing, Edward
2017-03-01
Loop quantum cosmology predicts that quantum gravity effects resolve the big-bang singularity and replace it by a cosmic bounce. Furthermore, loop quantum cosmology can also modify the form of primordial cosmological perturbations, for example by reducing power at large scales in inflationary models or by suppressing the tensor-to-scalar ratio in the matter bounce scenario; these two effects are potential observational tests for loop quantum cosmology. In this article, I review these predictions and others, and also briefly discuss three open problems in loop quantum cosmology: its relation to loop quantum gravity, the trans-Planckian problem, and a possible transition from a Lorentzian to a Euclidean space-time around the bounce point.
Zhao, Wen
2016-01-01
The foundation of modern cosmology relies on the so-called cosmological principle which states an homogeneous and isotropic distribution of matter in the universe on large scales. However, recent observations, such as the temperature anisotropy of the cosmic microwave background (CMB) radiation, the motion of galaxies in the universe, the polarization of quasars and the acceleration of the cosmic expansion, indicate preferred directions in the sky. If these directions have a cosmological origin, the cosmological principle would be violated, and modern cosmology should be reconsidered. In this paper, by considering the preferred axis in the CMB parity violation, we find that it coincides with the preferred axes in CMB quadrupole and CMB octopole, and they all align with the direction of the CMB kinematic dipole. In addition, the preferred directions in the velocity flows, quasar alignment, anisotropy of the cosmic acceleration, the handedness of spiral galaxies, and the angular distribution of the fine-structu...
A numerical relativity scheme for cosmological simulations
Daverio, David; Mitsou, Ermis
2016-01-01
Fully non-linear cosmological simulations may prove relevant in understanding relativistic/non-linear features and, therefore, in taking full advantage of the upcoming survey data. We propose a new 3+1 integration scheme which is based on the presence of a perfect fluid (hydro) field, evolves only physical states by construction and passes the robustness test on an FLRW space-time. Although we use General Relativity as an example, the idea behind that scheme is applicable to any generally-covariant modified gravity theory and/or matter content, including a N-body sector.
AIC and BIC for cosmological interacting scenarios
Arevalo, Fabiola; Moya, Jorge
2016-01-01
In this paper we study linear and non-linear cosmological interactions with analytical solutions, 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 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.
AIC and BIC for cosmological interacting scenarios
Arevalo, Fabiola; Cid, Antonella; Moya, Jorge
2016-01-01
In this paper we study linear and non-linear cosmological interactions with analytical solutions, 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 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, w...
Directory of Open Access Journals (Sweden)
P. Ko
2014-12-01
Full Text Available 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(1X 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.
Nojiri, S.; Odintsov, S. D.; Oikonomou, V. K.
2016-06-01
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.
Attosecond nonlinear polarization and light-matter energy transfer in solids.
Sommer, A; Bothschafter, E M; Sato, S A; Jakubeit, C; Latka, T; Razskazovskaya, O; Fattahi, H; Jobst, M; Schweinberger, W; Shirvanyan, V; Yakovlev, V S; Kienberger, R; Yabana, K; Karpowicz, N; Schultze, M; Krausz, F
2016-05-23
Electric-field-induced charge separation (polarization) is the most fundamental manifestation of the interaction of light with matter and a phenomenon of great technological relevance. Nonlinear optical polarization produces coherent radiation in spectral ranges inaccessible by lasers and constitutes the key to ultimate-speed signal manipulation. Terahertz techniques have provided experimental access to this important observable up to frequencies of several terahertz. Here we demonstrate that attosecond metrology extends the resolution to petahertz frequencies of visible light. Attosecond polarization spectroscopy allows measurement of the response of the electronic system of silica to strong (more than one volt per ångström) few-cycle optical (about 750 nanometres) fields. Our proof-of-concept study provides time-resolved insight into the attosecond nonlinear polarization and the light-matter energy transfer dynamics behind the optical Kerr effect and multi-photon absorption. Timing the nonlinear polarization relative to the driving laser electric field with sub-30-attosecond accuracy yields direct quantitative access to both the reversible and irreversible energy exchange between visible-infrared light and electrons. Quantitative determination of dissipation within a signal manipulation cycle of only a few femtoseconds duration (by measurement and ab initio calculation) reveals the feasibility of dielectric optical switching at clock rates above 100 terahertz. The observed sub-femtosecond rise of energy transfer from the field to the material (for a peak electric field strength exceeding 2.5 volts per ångström) in turn indicates the viability of petahertz-bandwidth metrology with a solid-state device.
Attosecond nonlinear polarization and light-matter energy transfer in solids
Sommer, A.; Bothschafter, E. M.; Sato, S. A.; Jakubeit, C.; Latka, T.; Razskazovskaya, O.; Fattahi, H.; Jobst, M.; Schweinberger, W.; Shirvanyan, V.; Yakovlev, V. S.; Kienberger, R.; Yabana, K.; Karpowicz, N.; Schultze, M.; Krausz, F.
2016-06-01
Electric-field-induced charge separation (polarization) is the most fundamental manifestation of the interaction of light with matter and a phenomenon of great technological relevance. Nonlinear optical polarization produces coherent radiation in spectral ranges inaccessible by lasers and constitutes the key to ultimate-speed signal manipulation. Terahertz techniques have provided experimental access to this important observable up to frequencies of several terahertz. Here we demonstrate that attosecond metrology extends the resolution to petahertz frequencies of visible light. Attosecond polarization spectroscopy allows measurement of the response of the electronic system of silica to strong (more than one volt per ångström) few-cycle optical (about 750 nanometres) fields. Our proof-of-concept study provides time-resolved insight into the attosecond nonlinear polarization and the light-matter energy transfer dynamics behind the optical Kerr effect and multi-photon absorption. Timing the nonlinear polarization relative to the driving laser electric field with sub-30-attosecond accuracy yields direct quantitative access to both the reversible and irreversible energy exchange between visible-infrared light and electrons. Quantitative determination of dissipation within a signal manipulation cycle of only a few femtoseconds duration (by measurement and ab initio calculation) reveals the feasibility of dielectric optical switching at clock rates above 100 terahertz. The observed sub-femtosecond rise of energy transfer from the field to the material (for a peak electric field strength exceeding 2.5 volts per ångström) in turn indicates the viability of petahertz-bandwidth metrology with a solid-state device.
Can we distinguish early dark energy from a cosmological constant?
Shi, Difu; Baugh, Carlton M.
2016-07-01
Early dark energy (EDE) models are a class of quintessence dark energy with a dynamically evolving scalar field which display a small but non-negligible amount of dark energy at the epoch of matter-radiation equality. Compared with a cosmological constant, the presence of dark energy at early times changes the cosmic expansion history and consequently the shape of the linear theory power spectrum and potentially other observables. We constrain the cosmological parameters in the EDE cosmology using recent measurements of the cosmic microwave background and baryon acoustic oscillations. The best-fitting models favour no EDE; here we consider extreme examples which are in mild tension with current observations in order to explore the observational consequences of a maximally allowed amount of EDE. We study the non-linear evolution of cosmic structure in EDE cosmologies using large-volume N-body simulations. Many large-scale structure statistics are found to be very similar between the Λ cold dark matter (ΛCDM) and EDE models. We find that EDE cosmologies predict fewer massive haloes in comparison to ΛCDM, particularly at high redshifts. The most promising way to distinguish EDE from ΛCDM is to measure the power spectrum on large scales, where differences of up to 15 per cent are expected.
Self-Consistent Cosmological Simulations of DGP Braneworld Gravity
Energy Technology Data Exchange (ETDEWEB)
Schmidt, Fabian [Univ. of Chicago, IL (United States). Kavli Inst. for Cosmological Physics (KICP)
2009-09-01
We perform cosmological N-body simulations of the Dvali-Gabadadze-Porrati braneworld model, by solving the full non-linear equations of motion for the scalar degree of freedom in this model, the brane bending mode. While coupling universally to matter, the brane-bending mode has self-interactions that become important as soon as the density field becomes non-linear. These self-interactions lead to a suppression of the field in high-density environments, and restore gravity to General Relativity. The code uses a multi-grid relaxation scheme to solve the non-linear field equation in the quasi-static approximation. We perform simulations of a flat self-accelerating DGP model without cosmological constant. However, the type of non-linear interactions of the brane-bending mode, which are the focus of this study, are generic to a wide class of braneworld cosmologies. The results of the DGP simulations are compared with standard gravity simulations assuming the same expansion history, and with DGP simulations using the linearized equation for the brane bending mode. This allows us to isolate the effects of the non-linear self-couplings of the field which are noticeable already on quasi-linear scales. We present results on the matter power spectrum and the halo mass function, and discuss the behavior of the brane bending mode within cosmological structure formation. We find that, independently of CMB constraints, the self-accelerating DGP model is strongly constrained by current weak lensing and cluster abundance measurements.
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.
Unlocking the full potential of wave-matter nonlinear coupling in the epsilon-near-zero regime
Ciattoni, Alessandro; Marini, Andrea; Di Falco, Andrea; Faccio, Daniele; Scalora, Michael
2015-01-01
In recent years, unconventional metamaterial properties have triggered a revolution of electromagnetic research which has unveiled novel scenarios of wave-matter interaction. A very small dielectric permittivity is a leading example of such unusual features, since it produces an exotic static-like regime where the electromagnetic field is spatially slowly-varying over a physically large region. The so-called epsilon-near-zero metamaterials thus offer an ideal platform where to manipulate the inner details of the "stretched" field. Here we theoretically prove that a standard nonlinearity is able to operate such a manipulation to the point that even a thin slab produces a dramatic nonlinear pulse transformation, if the dielectric permittivity is very small within the field bandwidth. The predicted non-resonant releasing of full nonlinear coupling produced by the epsilon-near-zero condition does not resort to any field enhancement mechanisms and opens novel routes to exploiting matter nonlinearity for steering t...
A convenient set of comoving cosmological variables and their application
Martel, Hugo; Shapiro, Paul R.
1998-06-01
A set of cosmological variables, which we shall refer to as `supercomoving variables', are presented which are an alternative to the standard comoving variables, particularly useful for describing the gas dynamics of cosmic structure formation. For an ideal gas with a ratio of specific heats gamma=5/3, the supercomoving position, velocity and thermodynamic properties (i.e. density, temperature and pressure) of matter are constant in time in a uniform, isotropic, adiabatically expanding universe. Expressed in terms of these supercomoving variables, the non-relativistic, cosmological fluid conservation equations of the Newtonian approximation and the Poisson equation closely resemble their non-cosmological counterparts. This makes it possible to generalize non-cosmological results and techniques to address problems involving departures from uniform, adiabatic Hubble expansion in a straightforward way, for a wide range of cosmological models. These variables were initially introduced by Shandarin to describe structure formation in matter-dominated models. In this paper, we generalize supercomoving variables to models with a uniform contribution to the energy density corresponding to a non-zero cosmological constant, domain walls, cosmic strings, a non-clumping form of non-relativistic matter (e.g. massive neutrinos in the presence of primordial density fluctuations of small wavelength) or a radiation background. Each model is characterized by the value of the density parameter Omega_0 of the non-relativistic matter component in which density fluctuation is possible, and the density parameter Omega_X0 of the additional non-clumping component. For each type of non-clumping background, we identify families within which different values of Omega_0 and Omega_X0 lead to fluid equations and solutions in supercomoving variables which are independent of the cosmological parameters Omega_0 and Omega_X0. We also generalize the description to include the effects of non
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
Quintessential Maldacena-Maoz Cosmologies
McInnes, Brett
2004-01-01
Maldacena and Maoz have proposed a new approach to holographic cosmology based on Euclidean manifolds with disconnected boundaries. This approach appears, however, to be in conflict with the known geometric results [the Witten-Yau theorem and its extensions] on spaces with boundaries of non-negative scalar curvature. We show precisely how the Maldacena-Maoz approach evades these theorems. We also exhibit Maldacena-Maoz cosmologies with [cosmologically] more natural matter content, namely quin...
The joint statistics of mildly non-linear cosmological densities and slopes in count-in-cells
Bernardeau, Francis; Pichon, Christophe
2015-01-01
In the context of count-in-cells statistics, the joint probability distribution of the density in two concentric spherical shells is predicted from first first principle for sigmas of the order of one. The agreement with simulation is found to be excellent. This statistics allows us to deduce the conditional one dimensional probability distribution function of the slope within under dense (resp. overdense) regions, or of the density for positive or negative slopes. The former conditional distribution is likely to be more robust in constraining the cosmological parameters as the underlying dynamics is less evolved in such regions. A fiducial dark energy experiment is implemented on such counts derived from Lambda-CDM simulations.
Aval, Hadi Gholian
2016-01-01
In this paper I will combine and use two Cardy-Jacobsen and Yaffe-Svetitsky conjectures [1, 2] to present a mechanism for a late-time inflation during the electroweak symmetry breaking due to discrete Z_3 symmetry at O(10^2 ) GeV and a psudo-inflation at O(10^2 ) MeV scale in order to solve the cosmological domain wall problem and thermal and non-thermal relics overproduction in the early universe. We will see that Cardy-Jacobsen conjecture and Zeldovic statement for cosmological domain wall problem are incompatible. Also, in the psudo-inflation mechanism presented here there would be a latent heat release and entropy injection without an exponential expansion and reheating period.
Shirasaki, Masato; Macias, Oscar; Horiuchi, Shunsaku; Shirai, Satoshi; Yoshida, Naoki
2016-09-01
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 ⟨σ v ⟩˜10-23 cm3/s are excluded for TeV-scale DM depending on channel. Lifetimes of ˜1 025 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.
Energy Technology Data Exchange (ETDEWEB)
Turner, Michael S.
1997-03-01
The Hubble constant sets the size and age of the Universe, and, together with independent determinations of the age, provides a consistency check of the standard cosmology. The Hubble constant also provides an important test of our most attractive paradigm for extending the standard cosmology, inflation and cold dark matter.
Slowly moving matter-wave gap soliton propagation in weak random nonlinear potential
Institute of Scientific and Technical Information of China (English)
Zhang Ming-Rui; Zhang Yong-Liang; Jiang Xun-Ya; Zi Jian
2008-01-01
We systematically investigate the motion of slowly moving matter-wave gap solitons in a nonlinear potential, produced by the weak random spatial variation of the atomic scattering length. With the weak randomness, we construct an effective-particle theory to study the motion of gap solitons. Based on the effective-particle theory, the effect of the randomness on gap solitous is obtained, and the motion of gap solitons is finally solved. Moreover, the analytic results for the general behaviours of gap soliton motion, such as the ensemble-average speed and the reflection probability depending on the weak randomness are obtained. We find that with the increase of the random strength the ensemble-average speed of gap solitons decreases slowly where the reduction is proportional to the variance of the weak randomness, and the reflection probability becomes larger. The theoretical results are in good agreement with the numerical simulations based on the Gross-Pitaevskii equation.
Shirasaki, Masato; Horiuchi, Shunsaku; Shirai, Satoshi; Yoshida, Naoki
2016-01-01
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 $\\sim660$ squared degrees in total. We improve upon our previous analyses by using an updated extragalactic $\\gamma$-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 $\\sim100$ in the mass range of O(1) TeV when including contributions from secondary $\\gamma...
Corda, Christian
2010-01-01
This Symposium is devoted to the Memory of Lev Kofman, June-17-1957-November-12-2009. The accelerated expansion of the Universe, which is today observed, shows that cosmological dynamics is dominated by the so-called Dark Energy field which provides a large negative pressure. This is the standard picture, in which such new ingredient is considered as a source of the right hand side of the field equations. It should be some form of non-clustered non-zero vacuum energy which, together with the clustered Dark Matter, drives the global dynamics. This is the so-called "concordance model" (ACDM) which gives, in agreement with the Cosmic Microwave Background Radiation (CMBR), dim Lyman Limit Systems (LLS) and type la supernovae (SNeIa) data, a good framework to understand the today observed Universe. However, it presents several shortcomings as the well known "coincidence" and "cosmological constant" problems . An alternative approach is to have a better understanding of the energy concept in General Relativity and ...
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.
Kehagias, A.; Riotto, A.
2016-05-01
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.
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.
Cosmological Probes for Supersymmetry
Khlopov, Maxim
2015-01-01
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.
Quantum Cosmology: Effective Theory
Bojowald, Martin
2012-01-01
Quantum cosmology has traditionally been studied at the level of symmetry-reduced minisuperspace models, analyzing the behavior of wave functions. However, in the absence of a complete full setting of quantum gravity and detailed knowledge of specific properties of quantum states, it remained difficult to make testable predictions. For quantum cosmology to be part of empirical science, it must allow for a systematic framework in which corrections to well-tested classical equations can be derived, with any ambiguities and ignorance sufficiently parameterized. As in particle and condensed-matter physics, a successful viewpoint is one of effective theories, adapted to specific issues one encounters in quantum cosmology. This review presents such an effective framework of quantum cosmology, taking into account, among other things, space-time structures, covariance, the problem of time and the anomaly issue.
Gibbons, Gary W
2013-01-01
In this paper we lay down the foundations for a purely Newtonian theory of cosmology, valid at scales small compared with the Hubble radius, using only Newtonian point particles acted on by gravity and a possible cosmological term. We describe the cosmological background which is given by an exact solution of the equations of motion in which the particles expand homothetically with their comoving positions constituting a central configuration. We point out, using previous work, that an important class of central configurations are homogeneous and isotropic, thus justifying the usual assumptions of elementary treatments. The scale factor is shown to satisfy the standard Raychaudhuri and Friedmann equations without making any fluid dynamic or continuum approximations. Since we make no commitment as to the identity of the point particles, our results are valid for cold dark matter, galaxies, or clusters of galaxies. In future publications we plan to discuss perturbations of our cosmological background from the p...
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.
Cosmological $N$-body simulations including radiation perturbations
Brandbyge, Jacob; Tram, Thomas; Leclercq, Florent; Fidler, Christian; Hannestad, Steen
2016-01-01
Cosmological $N$-body simulations are the standard tool 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 coupling between matter and radiation ($\\equiv$ photons and neutrinos). In this paper we investigate novel hybrid simulations which incorporate interactions between radiation and matter to the leading order in General Relativity, whilst evolving the matter dynamics in full non-linearity according to Newtonian theory. Our hybrid simulations come with a relativistic space-time and make it possible to investigate structure formation in a unified framework. In the present work we focus on simulations initialized at $z=99$, and show that the extracted matter power spectrum receives up to $3\\%$ corrections on very large scales through radiation. Our numerical findings compare favourably with linear analytical results from...
Li, Bohua; Rindler-Daller, Tanja
2016-01-01
We consider an alternative dark matter candidate, ultralight bosonic dark matter ($m>10^{-22}$eV) described by a complex scalar field (SFDM) with a global U(1) symmetry, for which the associated charge density is conserved after particle production during standard reheating (w=0). We allow for a repulsive self-interaction. In a Lambda-SFDM universe, SFDM starts relativistic, evolving from stiff (w=1) to radiationlike (w=1/3), before becoming nonrelativistic at late times (w=0). Thus, before the radiation-dominated era, there is an earlier era of stiff-SFDM-domination. Transitions between these eras, determined by SFDM particle mass $m$ and the quartic self-interaction coupling strength $\\lambda$, are thus constrained by cosmological observables, particularly N_{eff}, the effective number of neutrino species during BBN, and z_{eq}, the redshift of matter-radiation equality. Furthermore, since the stochastic gravitational wave background (SGWB) from inflation is amplified during the stiff era, it can contribute...
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...
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.
A solution of the cusp problem in relaxed halos of dark matter
Mikheeva, E; Doroshkevich, A.; Lukash, V.
2007-01-01
We propose a solution of the cusp problem in framework of the standard $\\Lambda$CDM cosmology. To do this we describe the linear and nonlinear periods of halo formation by the entropy function of dark matter particles. This approach allows us to take into account together the impact of both the processes of nonlinear relaxation of compressed matter and the small scale initial velocity perturbations in collapsed halos. We show that such random velocities lead to the random variations of the de...
Cosmological extrapolation of MOND
Kiselev, V V
2011-01-01
Regime of MOND, which is used in astronomy to describe the gravitating systems of island type without the need to postulate the existence of a hypothetical dark matter, is generalized to the case of homogeneous distribution of usual matter by introducing a linear dependence of the critical acceleration on the size of region under consideration. We show that such the extrapolation of MOND in cosmology is consistent with both the observed dependence of brightness on the redshift for type Ia supernovae and the parameters of large-scale structure of Universe in the evolution, that is determined by the presence of a cosmological constant, the ordinary matter of baryons and electrons as well as the photon and neutrino radiation without any dark matter.
Neutrinos in particle physics, astronomy, and cosmology
Xing, Zhi-Zhong
2011-01-01
""Neutrinos in Particle Physics, Astronomy and Cosmology"" provides a comprehensive and up-to-date introduction to neutrino physics, neutrino astronomy and neutrino cosmology. The intrinsic properties and fundamental interactions of neutrinos are described, as is the phenomenology of lepton flavor mixing, seesaw mechanisms and neutrino oscillations. The cosmic neutrino background, stellar neutrinos, supernova neutrinos and ultrahigh-energy cosmic neutrinos, together with the cosmological matter-antimatter asymmetry and other roles of massive neutrinos in cosmology, are discussed in detail. Thi
Quintin, Jerome; Cai, Yi-Fu; Brandenberger, Robert H
2015-01-01
Assuming that curvature perturbations and gravitational waves originally arise from vacuum fluctuations in a matter-dominated phase of contraction, we study the dynamics of the cosmological perturbations evolving through a nonsingular bouncing phase described by a generic single scalar field Lagrangian minimally coupled to Einstein gravity. In order for such a model to be consistent with the current upper limits on the tensor-to-scalar ratio, there must be an enhancement of the curvature fluctuations during the bounce phase. We show that, while it remains possible to enlarge the amplitude of curvature perturbations due to the non-trivial background evolution, this growth is very limited because of the conservation of curvature perturbations on super-Hubble scales. We further perform a general analysis of the evolution of primordial non-Gaussianities through the bounce phase. By studying the general form of the bispectrum we show that the non-Gaussianity parameter $f_{\\mathrm{NL}}$ (which is of order unity bef...
Initial Conditions for Accurate N-Body Simulations of Massive Neutrino Cosmologies
Zennaro, Matteo; Villaescusa-Navarro, Francisco; Carbone, Carmelita; Sefusatti, Emiliano; Guzzo, Luigi
2016-01-01
The set-up of the initial conditions in cosmological N-body simulations is usually implemented by rescaling the desired low-redshift linear power spectrum to the required starting redshift consistently with the Newtonian evolution of the simulation. The implementation of this practical solution requires more care in the context of massive neutrino cosmologies, mainly because of the non-trivial scale-dependence of the linear growth that characterises these models. In this work we consider a simple two-fluid, Newtonian approximation for cold dark matter and massive neutrinos perturbations that can reproduce the cold matter linear evolution predicted by Boltzmann codes such as CAMB or CLASS with a 0.1% accuracy or below for all redshift relevant to nonlinear structure formation. We use this description, in the first place, to quantify the systematic errors induced by several approximations often assumed in numerical simulations, including the typical set-up of the initial conditions for massive neutrino cosmolog...
Ackermann, M; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bouvier, A; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Carrigan, S; Casandjian, J M; Cecchi, C; Elik, O C; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Cutini, S; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; Silva, E do Couto e; Drell, P S; Dubois, R; Dumora, D; Edmonds, Y; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Fortin, P; Frailis, M; Fukazawa, Y; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giglietto, N; Giordano, F; Glanzman, T; Godfrey, G; Grove, J E; Guillemot, L; Guiriec, S; Gustafsson, M; Hadasch, D; Harding, A K; Horan, D; Hughes, R E; Johnson, A S; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knodlseder, J; Kuss, M; Lande, J; Latronico, L; Garde, M Llena; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Makeev, A; Mazziotta, M N; McEnery, J E; Meurer, C; Michelson, P F; Mitthumsiri, W; Mizuno, T; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Omodei, N; Orlando, E; Ormes, J F; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Raino, S; Rando, R; Reimer, A; Reimer, O; Reposeur, T; Rodriguez, A Y; Roth, M; Sadrozinski, H F W; Sander, A; Parkinson, P M Saz; Scargle, J D; Sellerholm, A; Sgro, C; Siskind, E J; Smith, P D; Spandre, G; Spinelli, P; Starck, J L; Strickman, M S; Suson, D J; Takahashi, H; Tanaka, T; Thayer, J B; Thayer, J G; Torres, D F; Uchiyama, Y; Usher, T L; Vasileiou, V; Vilchez, N; Vitale, V; Waite, A P; Wang, P; Winer, B L; Wood, K S; Ylinen, T; Zaharijas, G; Ziegle, M
2010-01-01
The first published Fermi large area telescope (Fermi-LAT) measurement of the isotropic diffuse gamma-ray emission is in good agreement with a single power law, and is not showing any signature of a dominant contribution from dark matter sources in the energy range from 20 to 100 GeV. We use the absolute size and spectral shape of this measured flux to derive cross section limits on three types of generic dark matter candidates: annihilating into quarks, charged leptons and monochromatic photons. Predicted gamma-ray fluxes from annihilating dark matter are strongly affected by the underlying distribution of dark matter, and by using different available results of matter structure formation we assess these uncertainties. We also quantify how the dark matter constraints depend on the assumed conventional backgrounds and on the Universe's transparency to high-energy gamma-rays. In reasonable background and dark matter structure scenarios (but not in all scenarios we consider) it is possible to exclude models pro...
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.
Cylindrical wormholes with positive cosmological constant
Richarte, Mart'\\in G
2013-01-01
We construct cylindrical, traversable wormholes with finite radii by taking into account the cut-and-paste procedure for the case of cosmic string manifolds with a positive cosmological constant. Under reasonable assumptions about the equation of state of the matter located at the shell, we find that the wormhole throat undergoes a monotonous evolution provided it moves at a constant velocity. In order to explore the dynamical nonlinear behaviour of the wormhole throat, we consider that the matter at the shell is supported by anisotropic Chaplygin gas, anti-Chaplygin gas, or a mixed of Chaplygin and anti-Chaplygin gases implying that wormholes could suffer an accelerated expansion or contraction but the oscillatory behavior seems to be forbidden.
Cylindrical wormholes with positive cosmological constant
Richarte, Martín G.
2013-07-01
We construct cylindrical, traversable wormholes with finite radii by taking into account the cut-and-paste procedure for the case of cosmic string manifolds with a positive cosmological constant. Under reasonable assumptions about the equation of state of the matter located at the shell, we find that the wormhole throat undergoes a monotonous evolution provided it moves at a constant velocity. In order to explore the dynamical nonlinear behavior of the wormhole throat, we consider that the matter of the shell is supported by anisotropic Chaplygin gas, anti-Chaplygin gas, or a mixture of Chaplygin and anti-Chaplygin gases, implying that wormholes could suffer an accelerated expansion or contraction, but that oscillatory behavior seems to be forbidden.
Dariescu, Marina-Aura; Dariescu, Ciprian
2017-01-01
This work is devoted to the spatially open Friedmann-Robertson-Walker (FRW) Universe evolving from the stiff matter era to the dust dominated one. Within the quantum analysis based on the Wheeler-DeWitt equation, we derive the wave function of the (k = -1)-FRW Universe with combined matter sources. On the classical level, one has to deal with the Friedmann equation which leads on a dependence of the scale function on time generally expressed from functional relations involving elliptic integrals.
Shabani, Hamid; Ziaie, Amir Hadi
2017-08-01
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 -0.51, for at least a root of equation n(s)=s-1, include an unphysical dark energy solution preceding an improper matter era. Finally, for nlaw dependency i.e., f(R,T)=R^{β }+(-T)^{α } can be observationally motivating for m→ 0+ and -0.024<α <0.02 and therefore could provide a suitable setting for later investigations.
Shimabukuro, Hayato; Inoue, Susumu; Yokoyama, Shuichiro
2014-01-01
Although the cosmological paradigm based on cold dark matter and adiabatic, nearly scale-invariant primordial fluctuations is consistent with a wide variety of existing observations, it has yet to be sufficiently tested on scales smaller than those of massive galaxies, and various alternatives have been proposed that differ significantly in the consequent small-scale power spectrum (SSPS) of large-scale structure. Here we show that a powerful probe of the SSPS at $k\\gtrsim 10$ Mpc$^{-1}$ can be provided by the 21 cm forest, that is, systems of narrow absorption lines due to intervening, cold neutral hydrogen in the spectra of high-redshift background radio sources in the cosmic reionization epoch. Such features are expected to be caused predominantly by collapsed gas in starless minihalos, whose mass function can be very sensitive to the SSPS. As specific examples, we consider the effects of neutrino mass, running spectral index (RSI) and warm dark matter (WDM) on the SSPS, and evaluate the expected distribut...
Studies into the averaging problem: Macroscopic gravity and precision cosmology
Wijenayake, Tharake S.
2016-08-01
With the tremendous improvement in the precision of available astrophysical data in the recent past, it becomes increasingly important to examine some of the underlying assumptions behind the standard model of cosmology and take into consideration nonlinear and relativistic corrections which may affect it at percent precision level. Due to its mathematical rigor and fully covariant and exact nature, Zalaletdinov's macroscopic gravity (MG) is arguably one of the most promising frameworks to explore nonlinearities due to inhomogeneities in the real Universe. We study the application of MG to precision cosmology, focusing on developing a self-consistent cosmology model built on the averaging framework that adequately describes the large-scale Universe and can be used to study real data sets. We first implement an algorithmic procedure using computer algebra systems to explore new exact solutions to the MG field equations. After validating the process with an existing isotropic solution, we derive a new homogeneous, anisotropic and exact solution. Next, we use the simplest (and currently only) solvable homogeneous and isotropic model of MG and obtain an observable function for cosmological expansion using some reasonable assumptions on light propagation. We find that the principal modification to the angular diameter distance is through the change in the expansion history. We then linearize the MG field equations and derive a framework that contains large-scale structure, but the small scale inhomogeneities have been smoothed out and encapsulated into an additional cosmological parameter representing the averaging effect. We derive an expression for the evolution of the density contrast and peculiar velocities and integrate them to study the growth rate of large-scale structure. We find that increasing the magnitude of the averaging term leads to enhanced growth at late times. Thus, for the same matter content, the growth rate of large scale structure in the MG model
Cosmological neutrino simulations at extreme scale
Emberson, J. D.; Yu, Hao-Ran; Inman, Derek; Zhang, Tong-Jie; Pen, Ue-Li; Harnois-Déraps, Joachim; Yuan, Shuo; Teng, Huan-Yu; Zhu, Hong-Ming; Chen, Xuelei; Xing, Zhi-Zhong
2017-08-01
Constraining neutrino mass remains an elusive challenge in modern physics. Precision measurements are expected from several upcoming cosmological probes of large-scale structure. Achieving this goal relies on an equal level of precision from theoretical predictions of neutrino clustering. Numerical simulations of the non-linear evolution of cold dark matter and neutrinos play a pivotal role in this process. We incorporate neutrinos into the cosmological N-body code CUBEP3M and discuss the challenges associated with pushing to the extreme scales demanded by the neutrino problem. We highlight code optimizations made to exploit modern high performance computing architectures and present a novel method of data compression that reduces the phase-space particle footprint from 24 bytes in single precision to roughly 9 bytes. We scale the neutrino problem to the Tianhe-2 supercomputer and provide details of our production run, named TianNu, which uses 86% of the machine (13 824 compute nodes). With a total of 2.97 trillion particles, TianNu is currently the world’s largest cosmological N-body simulation and improves upon previous neutrino simulations by two orders of magnitude in scale. We finish with a discussion of the unanticipated computational challenges that were encountered during the TianNu runtime.
Tartaglia, Angelo
2015-01-01
Starting from some relevant facts concerning the behaviour of the universe over large scale and time span, the analogy between the geometric approach of General Relativ- ity and the classical description of an elastic strained material continuum is discussed. Extending the elastic deformation approach to four dimensions it is shown that the accelerated expansion of the universe is recovered. The strain field of space-time repro- duces properties similar to the ones ascribed to the dark energy currently called in to explain the accelerated expansion. The strain field in the primordial universe behaves as radiation, but asymptotically it reproduces the cosmological constant. Subjecting the theory to a number of cosmological tests confirms the soundness of the approach and gives an optimal value for the one parameter of the model, i.e. the bulk modulus of the space-time continuum. Finally various aspects of the Strained State Cosmology (SSC) are discussed and contrasted with some non-linear massive gravity theor...
Non-linear hydrodynamics of axion dark matter: relative velocity effects and "quantum forces"
Marsh, David J E
2015-01-01
The non-linear hydrodynamic equations for axion/scalar field dark matter (DM) in the non-relativistic Madelung-Shcr\\"{o}dinger form are derived in a simple manner, including the effects of universal expansion and Hubble drag. The hydrodynamic equations are used to investigate the relative velocity between axion DM and baryons, and the moving-background perturbation theory (MBPT) derived. Axions massive enough to be all of the DM do not affect the coherence length of the relative velocity, but the MBPT equations are modified by the inclusion of the axion effective sound speed. These MBPT equations are necessary for accurately modelling the effects of axion DM on the formation of the first cosmic structures, and suggest that the 21cm power spectrum could improve constraints on axion mass by up to four orders of magnitude with respect to the current best constraints. A further application of these results uses the "quantum force" analogy to model scalar field gradient energy in a smoothed-particle hydrodynamics ...
2011-01-01
The twentieth century elevated our understanding of the Universe from its early stages to what it is today and what is to become of it. Cosmology is the weapon that utilizes all the scientific tools that we have created to feel less lost in the immensity of our Universe. The standard model is the theory that explains the best what we observe. Even with all the successes that this theory had, two main questions are still to be answered: What is the nature of dark matter and dark energy? This book attempts to understand these questions while giving some of the most promising advances in modern cosmology.
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.
Halo Concentration and the Dark Matter Power Spectrum
Huffenberger, Kevin M; Huffenberger, Kevin M.; Seljak, Uros
2003-01-01
We explore the connection between halo concentration and the dark matter power spectrum using the halo model. We fit halo model parameters to non-linear power spectra over a large range of cosmological models. We find that the non-linear evolution of the power spectrum generically prefers the concentration at non-linear mass scale to decrease with the effective slope of the linear power spectrum, in agreement with the direct analysis of the halo structure in different cosmological models. Using these analyses, we compute the predictions for non-linear power spectrum beyond the current resolution of N-body simulations. We find that the halo model predictions are generically below the analytical non-linear models, suggesting that the latter may overestimate the amount of power on small scales.
An Approach to Loop Quantum Cosmology Through Integrable Discrete Heisenberg Spin Chains
Dantas, Christine C
2012-01-01
The quantum evolution equation of Loop Quantum Cosmology (LQC) -- the quantum Hamiltonian constraint -- is a difference equation. We relate the LQC constraint equation in vacuum Bianchi I separable (locally rotationally symmetric) models with an integrable differential-difference nonlinear Schr\\"odinger type equation, which in turn is known to be associated with integrable, discrete Heisenberg spin chain models in condensed matter physics. We illustrate the similarity between both systems with a simple constraint in the linear regime.
Evolution and Statistics of Non-Sphericity of Dark Matter Halos from Cosmological N-Body Simulation
Suto, Daichi; Nishimichi, Takahiro; Sasaki, Shin; Suto, Yasushi
2016-01-01
We revisit the non-sphericity of cluster-mass scale halos from cosmological N-body simulation on the basis of triaxial modelling. In order to understand the difference between the simulation results and the conventional ellipsoidal collapse model (EC), we first consider the evolution of individual simulated halos. The major difference between EC and the simulation becomes appreciable after the turn-around epoch. Moreover, it is sensitive to the individual evolution history of each halo. Despite such strong dependence on individual halos, the resulting nonsphericity of halos exhibits weak but robust mass dependence in a statistical fashion; massive halos are more spherical up to the turn-around, but gradually become less spherical by z = 0. This is clearly inconsistent with the EC prediction; massive halos are usually more spherical. In addition, at z=0, inner regions of the halos are less spherical than outer regions, i.e., the density distribution inside the halos is highly inhomogeneous and therefore not se...
Stornaiolo, C
2002-01-01
In this letter we propose the existence of low density black holes and discuss its compatibility with the cosmological observations. The origin of these black holes can be traced back to the collapse of long wavelength cosmological perturbations during the matter dominated era, when the densities are low enough to neglect any internal and thermal pressure. By introducing a threshold density $\\hat{\\rho}$ above which pressure and non-gravitational interactions become effective, we find the highest wavelength for the perturbations that can reach an equilibrium state instead of collapsing to a black hole. The low density black holes introduced here, if they exist, can be observed through weak and strong gravitational lensing effects. Finally we observe that we obtained here a cosmological model which is capable to explain in a qualitative way the void formation together with the value $\\Omega=1$. But we remark that it needs to be improved by considering non spherical symmetric black holes.
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.
Embedding cosmological inflation, axion dark matter and seesaw mechanism in a 3-3-1 gauge model
Ferreira, J. G.; de S. Pires, C. A.; Rodrigues, J. G.; Rodrigues da Silva, P. S.
2017-08-01
The Peccei-Quinn symmetry is an intrinsic global symmetry of the 3-3-1 gauge models. Its spontaneous breaking mechanism engendering an invisible KSVZ-like axion links the 3-3-1 models with new physics at ∼1010 GeV scale. The axion that results from this mechanism is an interesting candidate for the dark matter of the universe, while its real partner may drive inflation if radiative corrections are taken into account. This is obtained by connecting the type I seesaw mechanism with the spontaneous breaking of the Peccei-Quinn symmetry. In the end of the day we have a scenario providing a common answer to the strong-CP problem, inflation, dark matter and neutrino mass.
Embedding cosmological inflation, axion dark matter and seesaw mechanism in a 3-3-1 gauge model
Directory of Open Access Journals (Sweden)
J.G. Ferreira, Jr.
2017-08-01
Full Text Available The Peccei–Quinn symmetry is an intrinsic global symmetry of the 3-3-1 gauge models. Its spontaneous breaking mechanism engendering an invisible KSVZ-like axion links the 3-3-1 models with new physics at ∼1010 GeV scale. The axion that results from this mechanism is an interesting candidate for the dark matter of the universe, while its real partner may drive inflation if radiative corrections are taken into account. This is obtained by connecting the type I seesaw mechanism with the spontaneous breaking of the Peccei–Quinn symmetry. In the end of the day we have a scenario providing a common answer to the strong-CP problem, inflation, dark matter and neutrino mass.
Exploring Bouncing Cosmologies with Cosmological Surveys
Cai, Yi-Fu
2014-01-01
In light of the recent observational data coming from the sky we have two significant directions in the field of theoretical cosmology recently. First, we are now able to make use of present observations, such as the Planck and BICEP2 data, to examine theoretical predictions from the standard inflationary $\\Lambda$CDM which were made decades of years ago. Second, we can search for new cosmological signatures as a way to explore physics beyond the standard cosmic paradigm. In particular, a subset of early universe models admit a nonsingular bouncing solution that attempts to address the issue of the big bang singularity. These models have achieved a series of considerable developments in recent years, in particular in their perturbative frameworks, which made brand-new predictions of cosmological signatures that could be visible in current and forthcoming observations. In this article we present two representative paradigms of very early universe physics. The first is the so-called new matter (or matter-ekpyro...
Indian Academy of Sciences (India)
Sabine Kraml
2006-10-01
There is a strong and growing interplay between particle physics and cosmology. In this talk, I discuss some aspects of this interplay concerning dark matter candidates put forth by theories beyond the standard model. In explaining the requirements for collider tests of such dark matter candidates, I focus in particular on the case of the lightest neutralino in the MSSM.
Nonstandard cosmologies from physics beyond the Standard model
Khlopov, M. Yu.
2016-01-01
The modern cosmology is based on inflationary models with baryosynthesis and dark matter/energy.It implies extension of particle symmetry beyond the Standard model. Studies of physical basis of the modern cosmology combine direct searches for new physics at accelerators with its indirect non-accelerator probes, in which cosmological consequences of particle models play important role. The cosmological consequences of particle models inevitably go beyond the 'standard' cosmological $\\Lambda$CD...
Evolution and statistics of non-sphericity of dark matter halos from cosmological N-body simulation
Suto, Daichi; Kitayama, Tetsu; Nishimichi, Takahiro; Sasaki, Shin; Suto, Yasushi
2016-10-01
We revisit the non-sphericity of cluster-mass-scale halos from cosmological N-body simulation on the basis of triaxial modeling. In order to understand the difference between the simulation results and the conventional ellipsoidal collapse model (EC), we first consider the evolution of individual simulated halos. The major difference between EC and the simulation becomes appreciable after the turnaround epoch. Moreover, it is sensitive to the individual evolution history of each halo. Despite such strong dependence on individual halos, the resulting non-sphericity of halos exhibits weak but robust mass dependence in a statistical fashion; massive halos are more spherical up to the turnaround, but gradually become less spherical by z = 0. This is clearly inconsistent with the EC prediction: massive halos are usually more spherical. In addition, at z = 0, inner regions of the simulated halos are less spherical than outer regions; that is, the density distribution inside the halos is highly inhomogeneous and therefore not self-similar (concentric ellipsoids with the same axis ratio and orientation). This is also inconsistent with the homogeneous density distribution that is commonly assumed in EC. Since most of previous fitting formulae for the probability distribution function (PDF) of the axis ratio of triaxial ellipsoids have been constructed under the self-similarity assumption, they are not accurate. Indeed, we compute the PDF of the projected axis ratio a1/a2 directly from the simulation data without the self-similarity assumption, and find that it is very sensitive to the assumption. The latter needs to be carefully taken into account in direct comparison with observations, and therefore we provide an empirical fitting formula for the PDF of a1/a2. Our preliminary analysis suggests that the derived PDF of a1/a2 roughly agrees with the current weak-lensing observations. More importantly, the present results will be useful for future exploration of the non
Evolution and statistics of non-sphericity of dark matter halos from cosmological N-body simulation
Suto, Daichi; Kitayama, Tetsu; Nishimichi, Takahiro; Sasaki, Shin; Suto, Yasushi
2016-12-01
We revisit the non-sphericity of cluster-mass-scale halos from cosmological N-body simulation on the basis of triaxial modeling. In order to understand the difference between the simulation results and the conventional ellipsoidal collapse model (EC), we first consider the evolution of individual simulated halos. The major difference between EC and the simulation becomes appreciable after the turnaround epoch. Moreover, it is sensitive to the individual evolution history of each halo. Despite such strong dependence on individual halos, the resulting non-sphericity of halos exhibits weak but robust mass dependence in a statistical fashion; massive halos are more spherical up to the turnaround, but gradually become less spherical by z = 0. This is clearly inconsistent with the EC prediction: massive halos are usually more spherical. In addition, at z = 0, inner regions of the simulated halos are less spherical than outer regions; that is, the density distribution inside the halos is highly inhomogeneous and therefore not self-similar (concentric ellipsoids with the same axis ratio and orientation). This is also inconsistent with the homogeneous density distribution that is commonly assumed in EC. Since most of previous fitting formulae for the probability distribution function (PDF) of the axis ratio of triaxial ellipsoids have been constructed under the self-similarity assumption, they are not accurate. Indeed, we compute the PDF of the projected axis ratio a1/a2 directly from the simulation data without the self-similarity assumption, and find that it is very sensitive to the assumption. The latter needs to be carefully taken into account in direct comparison with observations, and therefore we provide an empirical fitting formula for the PDF of a1/a2. Our preliminary analysis suggests that the derived PDF of a1/a2 roughly agrees with the current weak-lensing observations. More importantly, the present results will be useful for future exploration of the non
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
Back Reaction of Cosmological Perturbations
Brandenberger, R H
2000-01-01
The presence of cosmological perturbations affects the background metric and matter configuration in which the perturbations propagate. This effect, studied a long time ago for gravitational waves, also is operational for scalar gravitational fluctuations, inhomogeneities which are believed to be more important in inflationary cosmology. The back-reaction of fluctuations can be described by an effective energy-momentum tensor. The issue of coordinate invariance makes the analysis more complicated for scalar fluctuations than for gravitational waves. We show that the back-reaction of fluctuations can be described in a diffeomorphism-invariant way. In an inflationary cosmology, the back-reaction is dominated by infrared modes. We show that these modes give a contribution to the effective energy-momentum tensor of the form of a negative cosmological constant whose absolute value grows in time. We speculate that this may lead to a self-regulating dynamical relaxation mechanism for the cosmological constant. This ...
On Hamiltonian formulation of cosmologies
Indian Academy of Sciences (India)
K D Krori; S Dutta
2000-03-01
Novello et al [1,2] have shown that it is possible to ﬁnd a pair of canonically conjugate variables (written in terms of gauge-invariant variables) so as to obtain a Hamiltonian that describes the dynamics of a cosmological system. This opens up the way to the usual technique of quantization. Elbaz et al [4] have applied this method to the Hamiltonian formulation of FRW cosmological equations. This note presents a generalization of this approach to a variety of cosmologies. A general Schrödinger wave equation has been derived and exact solutions have been worked out for the stiff matter era for some cosmological models. It is argued that these solutions appear to hint at their possible relevance in the early phase of cosmological evolution.
Brandenberger, R H; Brandenberger, Robert H.; Magueijo, Joao
1999-01-01
We review a few off-the-beaten-track ideas in cosmology. They solve a variety of fundamental problems; also they are fun. We start with a description of non-singular dilaton cosmology. In these scenarios gravity is modified so that the Universe does not have a singular birth. We then present a variety of ideas mixing string theory and cosmology. These solve the cosmological problems usually solved by inflation, and furthermore shed light upon the issue of the number of dimensions of our Universe. We finally review several aspects of the varying speed of light theory. We show how the horizon, flatness, and cosmological constant problems may be solved in this scenario. We finally present a possible experimental test for a realization of this theory: a test in which the Supernovae results are to be combined with recent evidence for redshift dependence in the fine structure constant.
Cosmological perturbations in teleparallel Loop Quantum Cosmology
Haro, Jaime
2013-01-01
Cosmological perturbations in Loop Quantum Cosmology (LQC) could be studied from two totally different ways. The first one, called holonomy corrected LQC, is performed in the Hamiltonian framework, where the Asthekar connection is replaced by a suitable sinus function (holonomy correction), in order to have a well-defined quantum analogue. The alternative approach is based in the fact that isotropic LQC could be also obtained as a particular case of teleparallel $F(T)$ gravity (teleparallel LQC). Then, working in the Lagrangian framework and using the well-know perturbation equations in $F(T)$ gravity, we have obtained, in teleparallel LQC, the equations for scalar and tensor perturbations, and the corresponding Mukhanov-Sasaki equations. For scalar perturbations, our equation only differs from the one obtained by holonomy corrections in the velocity of sound, leading both formulations, essentially to the same scale invariant power spectrum when a matter-dominated universe is considered. However for tensor pe...
Efficient Cosmological Perturbation Theory with FAST-PT
Fang, Xiao; Blazek, Jonathan; McEwen, Joseph; Hirata, Christopher M.
2017-01-01
Cosmological perturbation theory is a powerful tool to model observations of large-scale structure in the weakly non-linear regime. However, even at next-to-leading order, it results in computationally expensive mode-coupling integrals. In this talk, I will focus on the physics behind our extremely efficient algorithm, FAST-PT. I will show how the algorithm can be applied to calculate 1-loop power spectra for several cosmological observables, including the matter density, galaxy bias, galaxy intrinsic alignments, the Ostriker-Vishniac effect, the secondary CMB polarization due to baryon flows, and redshift-space distortions. Our public code is written in Python and is easy to use and adapt to additional applications.
Cosmology from start to finish.
Bennett, Charles L
2006-04-27
Cosmology is undergoing a revolution. With recent precise measurements of the cosmic microwave background radiation, large galaxy redshift surveys, better measurements of the expansion rate of the Universe and a host of other astrophysical observations, there is now a standard, highly constrained cosmological model. It is not a cosmology that was predicted. Unidentified dark particles dominate the matter content of our Universe, and mysteries surround the processes responsible for the accelerated expansion at its earliest moments (inflation?) and for its recent acceleration (dark energy?). New measurements must address the fundamental questions: what happened at the birth of the Universe, and what is its ultimate fate?
Analytic self-gravitating Skyrmions, cosmological bounces and AdS wormholes
Ayón-Beato, Eloy; Canfora, Fabrizio; Zanelli, Jorge
2016-01-01
We present a self-gravitating, analytic and globally regular Skyrmion solution of the Einstein-Skyrme system with winding number w = ± 1, in presence of a cosmological constant. The static spacetime metric is the direct product R ×S3 and the Skyrmion is the self-gravitating generalization of the static hedgehog solution of Manton and Ruback with unit topological charge. This solution can be promoted to a dynamical one in which the spacetime is a cosmology of the Bianchi type-IX with time-dependent scale and squashing coefficients. Remarkably, the Skyrme equations are still identically satisfied for all values of these parameters. Thus, the complete set of field equations for the Einstein-Skyrme-Λ system in the topological sector reduces to a pair of coupled, autonomous, nonlinear differential equations for the scale factor and a squashing coefficient. These equations admit analytic bouncing cosmological solutions in which the universe contracts to a minimum non-vanishing size, and then expands. A non-trivial byproduct of this solution is that a minor modification of the construction gives rise to a family of stationary, regular configurations in General Relativity with negative cosmological constant supported by an SU (2) nonlinear sigma model. These solutions represent traversable AdS wormholes with NUT parameter in which the only "exotic matter" required for their construction is a negative cosmological constant.
Domènech, Guillem
2016-01-01
From higher dimensional theories, e.g. string theory, one expects the presence of non-minimally coupled scalar fields. We review the notion of conformal frames in cosmology and emphasize their physical equivalence, which holds at least at a classical level. Furthermore, if there is a field, or fields, which dominates the universe, as it is often the case in cosmology, we can use such notion of frames to treat our system, matter and gravity, as two different sectors. On one hand, the gravity sector which describes the dynamics of the geometry and on the other hand the matter sector which has such geometry as a playground. We use this interpretation to build a model where the fact that a curvaton couples to a particular frame metric could leave an imprint in the CMB.
An Improved Cosmological Model
Tsamis, N C
2016-01-01
We study a class of non-local, action-based, and purely gravitational models. These models seek to describe a cosmology in which inflation is driven by a large, bare cosmological constant that is screened by the self-gravitation between the soft gravitons that inflation rips from the vacuum. Inflation ends with the universe poised on the verge of gravitational collapse, in an oscillating phase of expansion and contraction that should lead to rapid reheating when matter is included. After the attainment of a hot, dense universe the nonlocal screening terms become constant as the universe evolves through a conventional phase of radiation domination. The onset of matter domination triggers a much smaller anti-screening effect that could explain the current phase of acceleration.
Tsamis, N. C.; Woodard, R. P.
2016-08-01
We study a class of nonlocal, action-based, and purely gravitational models. These models seek to describe a cosmology in which inflation is driven by a large, bare cosmological constant that is screened by the self-gravitation between the soft gravitons that inflation rips from the vacuum. Inflation ends with the Universe poised on the verge of gravitational collapse, in an oscillating phase of expansion and contraction that should lead to rapid reheating when matter is included. After the attainment of a hot, dense Universe the nonlocal screening terms become constant as the Universe evolves through a conventional phase of radiation domination. The onset of matter domination triggers a much smaller antiscreening effect that could explain the current phase of acceleration.
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.
Tunable rotary orbits of matter-wave nonlinear modes in attractive Bose-Einstein condensates
Energy Technology Data Exchange (ETDEWEB)
He, Y J; Wang, H Z [State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-Sen University, Guangzhou, 510275 (China); Malomed, Boris A [Department of Physical Electronics, School of Electrical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978 (Israel); Mihalache, Dumitru [Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH), 407 Atomistilor, Magurele-Bucharest 077125 (Romania)], E-mail: stswhz@mail.sysu.edu.cn
2008-03-14
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.
Cosmology and astrophysics 1992
Krauss, L M
1992-01-01
I review recent developments in cosmology and astrophysics relevant to particle physics, focussing on the following questions: What's new in 1992? What have we learned since the last ICHEP meeting in 1990? and What are the prospects for the future? AMong the topics explicitly discussed are: COBE, Large Scale Structure, and Dark Matter; Bib Bang Nucleosynthesis; the Solar Neutrino Problem; and High Energy Gamma Ray PHysics.
Ryan, M.
1972-01-01
The study of cosmological models by means of equations of motion in Hamiltonian form is considered. Hamiltonian methods applied to gravity seem to go back to Rosenfeld (1930), who constructed a quantum-mechanical Hamiltonian for linearized general relativity theory. The first to notice that cosmologies provided a simple model in which to demonstrate features of Hamiltonian formulation was DeWitt (1967). Applications of the ADM formalism to homogeneous cosmologies are discussed together with applications of the Hamiltonian formulation, giving attention also to Bianchi-type universes. Problems involving the concept of superspace and techniques of quantization are investigated.
Cosmics cosmological initial conditions and microwave anisotropy codes
Bertschinger, E
1995-01-01
COSMICS is a package of fortran programs useful for computing transfer functions and microwave background anisotropy for cosmological models, and for generating gaussian random initial conditions for nonlinear structure formation simulations of such models. Four programs are provided: {\\bf linger\\_con} and {\\bf linger\\_syn} integrate the linearized equations of general relativity, matter, and radiation in conformal Newtonian and synchronous gauge, respectively; {\\bf deltat} integrates the photon transfer functions computed by the linger codes to produce photon anisotropy power spectra; and {\\bf grafic} tabulates normalized matter power spectra and produces constrained or unconstrained samples of the matter density field. Version 1.0 of COSMICS is available at http://arcturus.mit.edu/cosmics/ . The current release gives fortran-77 programs that run on workstations and vectorized supercomputers. Unix makefiles are included that make it simple to build and test the package. A future release will include portable...
Cosmological models of galaxy formation
Menci, N.
I review the present status of galaxy formation models within a cosmological framework. I focus on semi-analytic models based on the Cold Dark Matter scenario, discussing the role of the different physical process involving dark matter and baryons in determining the observed statistical properties of galaxies and their dependence on cosmic time and on environment evolution. I will highlight some present problems and briefly present the main effects of assuming a Warm Dark Matter scenario.
Nonlinear Spinor field in isotropic space-time and dark energy models
Saha, Bijan
2016-01-01
Within the scope of isotropic FRW cosmological model the role of nonlinear spinor field in the evolution of the Universe is studied. It is found that unlike in anisotropic cosmological models in the present case the spinor field does not possess nontrivial non-diagonal components of energy-momentum tensor. The spinor description of different matter was given and evolution of the Universe corresponding to these source is illustrated. In the framework of a three fluid system the utility of spinor description of matter is established.
The screening Horndeski cosmologies
Starobinsky, Alexei A.; Sushkov, Sergey V.; Volkov, Mikhail S.
2016-06-01
We present a systematic analysis of homogeneous and isotropic cosmologies in a particular Horndeski model with Galileon shift symmetry, containing also a Λ-term and a matter. The model, sometimes called Fab Five, admits a rich spectrum of solutions. Some of them describe the standard late time cosmological dynamic dominated by the Λ-term and matter, while at the early times the universe expands with a constant Hubble rate determined by the value of the scalar kinetic coupling. For other solutions the Λ-term and matter are screened at all times but there are nevertheless the early and late accelerating phases. The model also admits bounces, as well as peculiar solutions describing ``the emergence of time''. Most of these solutions contain ghosts in the scalar and tensor sectors. However, a careful analysis reveals three different branches of ghost-free solutions, all showing a late time acceleration phase. We analyse the dynamical stability of these solutions and find that all of them are stable in the future, since all their perturbations stay bounded at late times. However, they all turn out to be unstable in the past, as their perturbations grow violently when one approaches the initial spacetime singularity. We therefore conclude that the model has no viable solutions describing the whole of the cosmological history, although it may describe the current acceleration phase. We also check that the flat space solution is ghost-free in the model, but it may acquire ghost in more general versions of the Horndeski theory.
Investigating inhomogeneous Szekeres models and their applications to precision cosmology
Peel, Austin Chandler
Exact solutions of Einstein's field equations that can describe the evolution of complex structures in the universe provide complementary frameworks to standard perturbation theory in which to analyze cosmological and astrophysical phenomena. The flexibility and generality of the inhomogeneous and anisotropic Szekeres metric make it the best known exact solution to explore nonlinearities in the universe. We study applications of Szekeres models to precision cosmology, focusing on the influence of inhomogeneities in two primary contexts---the growth rate of cosmic structures and biases in distance determinations to remote sources. We first define and derive evolution equations for a Szekeres density contrast, which quantifies exact deviations from a smooth background cosmology. Solving these equations and comparing to the usual perturbative approach, we find that for models with the same matter content, the Szekeres growth rate is larger through the matter-dominated cosmic era. Including a cosmological constant, we consider exact global perturbations, as well as the evolution of a single extended structure surrounded by an almost homogeneous background. For the former, we use growth data to obtain a best fit Szekeres model and find that it can fit the data as well as the standard Lambda-Cold Dark Matter (LCDM) cosmological model but with different cosmological parameters. Next, to study effects of inhomogeneities on distance measures, we build an exact relativistic Swiss-cheese model of the universe, where a large number of non-symmetric and randomly placed Szekeres structures are embedded within a LCDM background. Solving the full relativistic propagation equations, light beams are traced through the model, where they traverse the inhomogeneous structures in a way that mimics the paths of real light beams in the universe. For beams crossing a single structure, their magnification or demagnification reflects primarily the net density encountered along the path
Silk, Joseph
2008-11-01
recent, and comprehensive, is Cosmology, in which the University of Texas physicist and Nobel Laureate, Steven Weinberg provides a concise introduction to modern cosmology. The book is aimed at the level of a final year physics undergraduate, or a first year graduate student. The discussion is self-contained, with numerous derivations. It begins with an overview of the standard cosmological model, and presents a detailed treatment of fluctuation growth. There are sections on gravitational lensing and inflationary cosmology, on microwave background fluctuations and structure growth. There are aspects however where a supplementary book is essential for the physicist being introduced to cosmology. The text is lacking in physical cosmology. The baryon physics of galaxy formation is barely mentioned, apart from a discussion of the Jeans mass. And it ignores one of the greatest contributions to the field by Russian cosmologist Yaakov Zel'dovich, who discovered the only nonspherical solution to the nonlinear evolution of density fluctuations, one that has since dominated our understanding of the large-scale structure of the universe via the cosmic web. But these are minor quibbles about what provides an outstanding introduction to modern cosmology, and one that takes us from the physics fundamentals up to the cosmic frontier. I recommend Cosmology for anyone wishing to enter the field and with a good physics background. It is ideal for the astronomer who may only have a sketchy knowledge of general relativity or particle physics. She will learn about vielbeins and scalar fields, gauge-invariant fluctuation theory and inflation. Steven Weinberg is a leading physicist who has also made important contributions to cosmology. The text provides a rigorous treatment of the standard model of cosmology, and of structure formation. Numerous exercises are provided. It provides an excellent core for a course on cosmology.
Cosmography: Cosmology without the Einstein equations
Visser, M
2004-01-01
How much of modern cosmology is really cosmography? How much of modern cosmology is independent of the Einstein equations? (Independent of the Friedmann equations?) These questions are becoming increasingly germane -- as the models cosmologists use for the stress-energy content of the universe become increasingly baroque, it behoves us to step back a little and carefully disentangle cosmological kinematics from cosmological dynamics. The use of basic symmetry principles (such as the cosmological principle) permits us to do a considerable amount, without ever having to address the vexatious issues of just how much "dark energy", "dark matter", "quintessence", and/or "phantom matter" is needed in order to satisfy the Einstein equations. This is the sub-sector of cosmology that Weinberg refers to as "cosmography", and in this article I will explore the extent to which cosmography is sufficient for analyzing the Hubble law and so describing many of the features of the universe around us.
Backreaction mechanism in multifluid and extended cosmologies
Jimenez, Jose Beltran; Dunsby, P K S; Saez-Gomez, D
2013-01-01
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. General Relativity together with pressure-free matter have until recently been considered as the sole ingredients for averaged calculations. 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.
Belinski, V
2009-01-01
The talk at international conference in honor of Ya. B. Zeldovich 95th Anniversary, Minsk, Belarus, April 2009. The talk represents a review of the old results and contemporary development on the problem of cosmological singularity.
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.
Kumar, Suresh
2014-01-01
In this work we consider a spatially homogeneous and flat FRW space-time filled with non-interacting matter and dark energy components. The equation of state (EoS) parameters of the two sources are varied phenomenologically in terms of scale factor of the FRW space-time in such a way that the evolution of the Universe takes place from the early radiation-dominated phase to the present dark energy-dominated phase. We find parameters of the model in terms of redshift, which in principle are observationally testable and allow us to compare the derived model with observations. We constrain the model in two cases with the latest astronomical observations, and discuss the best fit model parameters in detail. First, we explore a special case of the model with WMAP+BAO+H0 observations by synchronizing the model with the $\\Lambda$CDM model at the present epoch. An interesting point that emerges from this observational analysis is that the model is not only consistent with the $\\Lambda$CDM predictions at the present ep...
Kengne, E; Lakhssassi, A
2015-03-01
We consider a lossless one-dimensional nonlinear discrete bi-inductance electrical transmission line made of N identical unit cells. When lattice effects are considered, we use the reductive perturbation method in the semidiscrete limit to show that the dynamics of modulated waves can be modeled by the classical nonlinear Schrödinger (CNLS) equation, which describes the modulational instability and the propagation of bright and dark solitons on a continuous-wave background. Our theoretical analysis based on the CNLS equation predicts either two or four frequency regions with different behavior concerning the modulational instability of a plane wave. With the help of the analytical solutions of the CNLS equation, we investigate analytically the effects of the linear capacitance CS on the dynamics of matter-wave solitons in the network. Our results reveal that the linear parameter CS can be used to manipulate the motion of bright, dark, and kink soliton in the network.
Chavanis, Pierre-Henri
2016-01-01
We develop a general formalism applying to Newtonian self-gravitating Bose-Einstein condensates. This formalism may find application in the context of dark matter halos. We introduce a generalized Gross-Pitaevskii equation including a source of dissipation (damping) and an arbitrary nonlinearity. Using the Madelung transformation, we derive the hydrodynamic representation of this generalized Gross-Pitaevskii equation and obtain a damped quantum Euler equation involving a friction force proportional and opposite to the velocity and a pressure force associated with an equation of state determined by the nonlinearity present in the generalized Gross-Pitaevskii equation. In the strong friction limit, we obtain a quantum Smoluchowski equation. These equations satisfy an $H$-theorem for a free energy functional constructed with a generalized entropy. We specifically consider the Boltzmann and Tsallis entropies associated with isothermal and polytropic equations of state. We also consider the entropy associated with...
Cosmological implications of Primordial Black Holes
Bernal, Jos\\' e Luis; Bellomo, Nicola; Raccanelli, Alvise; Verde, Licia
2017-01-01
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 $\\sim 30 M_{\\odot}$ 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 observation...
Institute of Scientific and Technical Information of China (English)
张新民
2011-01-01
宇宙暗物质和暗能量是21世纪粒子物理和宇宙学研究中的两个重大的科学问题,文章首先简述了宇宙学研究的历史和现状以及对粒子物理学提出的新的挑战,接着较详细地介绍了暗物质、暗能量和反物质相关的科学问题以及在国际上这个研究领域近年来所取得的进展,最后展望了中国在暗物质和暗能量实验探测研究方面的前景.%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.
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.
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.
The Higgs Portal and Cosmology
Assamagan, Ketevi; Chou, John Paul; Curtin, David; Fedderke, Michael A; Gershtein, Yuri; He, Xiao-Gang; Klute, Markus; Kozaczuk, Jonathan; Kotwal, Ashutosh; Lowette, Steven; No, Jose Miguel; Plehn, Tilman; Qian, Jianming; Ramsey-Musolf, Michael; Safonov, Alexei; Shelton, Jessie; Spannowsky, Michael; Su, Shufang; Walker, Devin G E; Willocq, Stephane; Winslow, Peter
2016-01-01
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.
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.
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.
Particle physics in astrophysics and cosmology
Rees, Martin J.
1990-08-01
This paper briefly outlines some topics of current interest on the interface between astrophysics/cosmology and particle physics. These include: the implications of the cosmic light element abundances; evidence for non-baryonic dark matter, and the prospects for experimental searches; cosmic strings; and `inflationary' cosmology.
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.
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.
Cosmological Models with Time Dependent G and A Coupling Scalars
Institute of Scientific and Technical Information of China (English)
N.Ibotombi Singh; S.Kiranmla Chanu; S.Surendra Singh
2009-01-01
A cosmological model in which the universe has its critical density and gravitational constants generalized as coupling scalars in Einstein's theory is considered.A general method of solving the field equations is given.An exact solution for matter distribution in cosmological models satisfying G = Go(R/Ro)n is presented.Corresponding physical interpretations of the cosmological solutions are also discussed.
New Cosmology with Clusters of Galaxies
Schücker, P
2005-01-01
The review summarizes present and future applications of galaxy clusters to cosmology with emphasis on nearby X-ray clusters. The discussion includes the density of dark matter, the normalization of the matter power spectrum, neutrino masses, and especially the equation of state of the dark energy, the interaction between dark energy and ordinary matter, gravitational holography, and the effects of extra-dimensions.
Particle Aspects of Cosmology and Baryogenesis
Riazuddin, M
2003-01-01
An introduction to particle aspects of cosmology with particular refrence to primordial nucleosynthesis, dark matter and baryogenesis is provided. In particular, various scenarios-GUT baryogenesis, electroweak baryogenesis and baryogenesis through leptogenesis are reviewed.
Cosmological neutrino simulations at extreme scale
Emberson, J D; Inman, Derek; Zhang, Tong-Jie; Pen, Ue-Li; Harnois-Deraps, Joachim; Yuan, Shuo; Teng, Huan-Yu; Zhu, Hong-Ming; Chen, Xuelei; Xing, Zhi-Zhong
2016-01-01
Constraining neutrino mass remains an elusive challenge in modern physics. Precision measurements are expected from several upcoming cosmological probes of large-scale structure. Achieving this goal relies on an equal level of precision from theoretical predictions of neutrino clustering. Numerical simulations of the non-linear evolution of cold dark matter and neutrinos play a pivotal role in this process. We incorporate neutrinos into the cosmological N-body code CUBEP3M and discuss the challenges associated with pushing to the extreme scales demanded by the neutrino problem. We highlight code optimizations made to exploit modern high performance computing architectures and present a novel method of data compression that reduces the phase-space particle footprint from 24 bytes in single precision to roughly 9 bytes. We scale the neutrino problem to the Tianhe-2 supercomputer and provide details of our production run, named TianNu, which uses 86% of the machine (13,824 compute nodes). With a total of 2.97 tr...
Ferreira, Cesar P; de Holanda, Pedro C
2015-01-01
We study sterile neutrinos in an extension of the standard model, based on the gauge group $SU(3)_C\\otimes SU(3)_L\\otimes SU(3)_R\\otimes U(1)_N$, and use this model to illustrate how to apply cosmological limits to thermalized particles that decouple while relativistic. These neutrinos, $N_{aL}$, can be dark matter candidates, with a keV mass range arising rather naturally in this model. We analyse the cosmological limits imposed by $N_{eff}$ and dark matter abundance on these neutrinos. Assuming that these neutrinos have roughly equal masses and are not CDM, we conclude that the $N_{eff}$ experimental value can be satisfied in some cases and the abundance constraint implies that these neutrinos are hot dark matter. With this information, we give upper bounds on the Yukawa coupling between the sterile neutrinos and a scalar field, the possible values of the VEV of this scalar field and lower bounds to the mass of one gauge boson of the model.
Narimani, Ali; Scott, Douglas
2011-01-01
Although it is possible that some fundamental physical constants could vary in time, it is important to only consider dimensionless combinations, such as the fine structure constant or the equivalent coupling constant for gravity. Once all such dimensionless numbers have been given, then we can be sure that our cosmological picture is governed by the same physical laws as that of another civilization with an entirely different set of units. An additional feature of the standard model of cosmology raises an extra complication, namely that the epoch at which we live is a crucial part of the model. This can be defined by giving the value of any one of the evolving cosmological parameters. It takes some care to avoid inconsistent results for constraints on variable constants, which could be caused by effectively fixing more than one parameter today. We show examples of this effect by considering in some detail the physics of Big Bang nucleosynthesis, recombination and microwave background anisotropies, being care...
Nonstandard cosmologies from physics beyond the Standard model
Khlopov, M Yu
2016-01-01
The modern cosmology is based on inflationary models with baryosynthesis and dark matter/energy.It implies extension of particle symmetry beyond the Standard model. Studies of physical basis of the modern cosmology combine direct searches for new physics at accelerators with its indirect non-accelerator probes, in which cosmological consequences of particle models play important role. The cosmological consequences of particle models inevitably go beyond the 'standard' cosmological $\\Lambda$CDM model and some possible feature of such 'nonstandard'cosmological scenarios is the subject of the present brief review.
Rich, James
2009-01-01
The book is aimed at astrophysics students and professional physicists who wish to understand the basics of cosmology and general relativity as well as the observational foundations of the LambdaCDM model of the Universe. The book provides a self-contained introduction to general relativity that is based on the homogeneity and isotropy of the local universe. The simplicity of this space allows general relativity to be presented in a very elementary manner while laying the foundation for the treatment of more complicated problems. The new edition presents the most recent observations, including those of CMB anisotropies by WMAP and of Baryon Acoustic Oscillations by SDSS. Future observational and theoretical challenges for the understanding of dark energy and dark matter are discussed. From 1st edition reviews: "The book provides a comprehensive and thorough explication of current cosmology at a level appropriate for a beginning graduate student or an advanced and motivated undergraduate. ... This is an extrem...
Kiselev, V V
2012-01-01
A huge value of cosmological constant characteristic for the particle physics and the inflation of early Universe are inherently related to each other: one can construct a fine-tuned superpotential, which produces a flat potential of inflaton with a constant density of energy V=\\Lambda^4 after taking into account for leading effects due to the supergravity, so that an introduction of small quantum loop-corrections to parameters of this superpotential naturally results in the dynamical instability relaxing the primary cosmological constant by means of inflationary regime. The model phenomenologically agrees with observational data on the large scale structure of Universe at \\Lambda~10^{16} GeV.
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
2016-09-01
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.
Galtsov, D V
2003-01-01
We discuss isotropic and homogeneous D-brane-world cosmology with non-Abelian Born-Infeld (NBI) matter on the brane. In the usual Friedmann-Robertson-Walker (FRW) model the scale non-invariant NBI matter gives rise to an equation of state which asymptotes to the string gas equation $p=-\\epsilon/3$ and ensures a start-up of the cosmological expansion with zero acceleration. We show that the same state equation in the brane-world setup leads to the Tolman type evolution as if the conformal symmetry was effectively restored. This is not precisely so in the NBI model with symmetrized trace, but the leading term in the expansion law is still the same. A cosmological sphaleron solution on the D-brane is presented.
Causal compensated perturbations in cosmology
Energy Technology Data Exchange (ETDEWEB)
Veeraraghavan, S.; Stebbins, A. (Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (USA) California Univ., Berkeley (USA) Canadian Institute for Theoretical Astrophysics, Toronto (Canada))
1990-12-01
A theoretical framework is developed to calculate linear perturbations in the gravitational and matter fields which arise causally in response to the presence of stiff matter sources in a FRW cosmology. It is shown that, in order to satisfy energy and momentum conservation, the gravitational fields of the source must be compensated by perturbations in the matter and gravitational fields, and the role of such compensation in containing the initial inhomogeneities in their subsequent evolution is discussed. A complete formal solution is derived in terms of Green functions for the perturbations produced by an arbitrary source in a flat universe containing cold dark matter. Approximate Green function solutions are derived for the late-time density perturbations and late-time gravitational waves in a universe containing a radiation fluid. A cosmological energy-momentum pseudotensor is defined to clarify the nature of energy and momentum conservation in the expanding universe. 55 refs.
Inhomogeneous Cosmology with Numerical Relativity
Macpherson, Hayley J; Price, Daniel J
2016-01-01
We perform three-dimensional numerical relativity simulations of homogeneous and inhomogeneous expanding spacetimes, with a view towards quantifying non-linear effects from cosmological inhomogeneities. We demonstrate fourth-order convergence with errors less than one part in 10^6 in evolving a flat, dust Friedmann-Lemaitre-Roberston-Walker (FLRW) spacetime using the Einstein Toolkit within the Cactus framework. We also demonstrate agreement to within one part in 10^3 between the numerical relativity solution and the linear solution for density, velocity and metric perturbations in the Hubble flow over a factor of ~350 change in scale factor (redshift). We simulate the growth of linear perturbations into the non-linear regime, where effects such as gravitational slip and tensor perturbations appear. We therefore show that numerical relativity is a viable tool for investigating nonlinear effects in cosmology.
Cosmology with the Square Kilometre Array by SKA-Japan
Yamauchi, Daisuke; Ichiki, Kiyotomo; Kohri, Kazunori; Namikawa, Toshiya; Oyama, Yoshihiko; Sekiguchi, Toyokazu; Shimabukuro, Hayato; Takahashi, Keitaro; Takahashi, Tomo; Yokoyama, Shuichiro; Yoshikawa, Kohji
2016-12-01
In the past several decades, the standard cosmological model has been established and its parameters have been measured to a high precision, while there are still many fundamental questions in cosmology; such as the physics in the very early universe, the origin of the cosmic acceleration, and the nature of dark matter. The forthcoming radio telescope, the Square Kilometre Array (SKA), which will be the world's largest, will be able to open a new frontier in cosmology and will be one of the most powerful tools for cosmology in the coming decade. The cosmological surveys conducted by the SKA would have the potential not only to answer these fundamental questions but also deliver precision cosmology. In this article we briefly review the role of the SKA from the viewpoint of modern cosmology. The cosmological science led by the SKA-Japan Consortium (SKA-JP) Cosmology Science Working Group is also discussed.
Cosmology with the Square Kilometre Array by SKA-Japan
Yamauchi, Daisuke; Ichiki, Kiyotomo; Kohri, Kazunori; Namikawa, Toshiya; Oyama, Yoshihiko; Sekiguchi, Toyokazu; Shimabukuro, Hayato; Takahashi, Keitaro; Takahashi, Tomo; Yokoyama, Shuichiro; Yoshikawa, Kohji
2016-10-01
In the past several decades, the standard cosmological model has been established and its parameters have been measured to a high precision, while there are still many fundamental questions in cosmology; such as the physics in the very early universe, the origin of the cosmic acceleration, and the nature of dark matter. The forthcoming radio telescope, the Square Kilometre Array (SKA), which will be the world's largest, will be able to open a new frontier in cosmology and will be one of the most powerful tools for cosmology in the coming decade. The cosmological surveys conducted by the SKA would have the potential not only to answer these fundamental questions but also deliver precision cosmology. In this article we briefly review the role of the SKA from the viewpoint of modern cosmology. The cosmological science led by the SKA-Japan Consortium (SKA-JP) Cosmology Science Working Group is also discussed.
Cosmology with the Square Kilometre Array by SKA-Japan
Yamauchi, Daisuke; Kohri, Kazunori; Namikawa, Toshiya; Oyama, Yoshihiko; Sekiguchi, Toyokazu; Shimabukuro, Hayato; Takahashi, Keitaro; Takahashi, Tomo; Yokoyama, Shuichiro; Yoshikawa, Kohji
2016-01-01
In the past several decades, the standard cosmological model has been established and its parameters have been measured to a high precision, while there are still many of the fundamental questions in cosmology; such as the physics in the very early Universe, the origin of the cosmic acceleration and the nature of the dark matter. The future world's largest radio telescope, Square Kilometre Array (SKA), will be able to open the new frontier of cosmology and will be one of the most powerful tools for cosmology in the next decade. The cosmological surveys conducted by the SKA would have the potential not only to answer these fundamental questions but also deliver the precision cosmology. In this article we briefly review the role of the SKA from the view point of the modern cosmology. The cosmology science led by the SKA-Japan Consortium (SKA-JP) Cosmology Science Working Group is also discussed.
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.
Energy Technology Data Exchange (ETDEWEB)
Koivisto, Tomi [Institute for Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, N-0315 Oslo (Norway); Wills, Danielle [Centre for Particle Theory, Department of Mathematical Sciences, Durham University, South Road, Durham, DH1 3LE (United Kingdom); Zavala, Ivonne, E-mail: t.s.koivisto@astro.uio.no, E-mail: d.e.wills@durham.ac.uk, E-mail: e.i.zavala@rug.nl [Centre for Theoretical Physics, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands)
2014-06-01
Disformally coupled cosmologies arise from Dirac-Born-Infeld actions in Type II string theories, when matter resides on a moving hidden sector D-brane. Since such matter interacts only very weakly with the standard model particles, this scenario can provide a natural origin for the dark sector of the universe with a clear geometrical interpretation: dark energy is identified with the scalar field associated to the D-brane's position as it moves in the internal space, acting as quintessence, while dark matter is identified with the matter living on the D-brane, which can be modelled by a perfect fluid. The coupling functions are determined by the (warped) extra-dimensional geometry, and are thus constrained by the theory. The resulting cosmologies are studied using both dynamical system analysis and numerics. From the dynamical system point of view, one free parameter controls the cosmological dynamics, given by the ratio of the warp factor and the potential energy scales. The disformal coupling allows for new scaling solutions that can describe accelerating cosmologies alleviating the coincidence problem of dark energy. In addition, this scenario may ameliorate the fine-tuning problem of dark energy, whose small value may be attained dynamically, without requiring the mass of the dark energy field to be unnaturally low.
iCosmo: an Interactive Cosmology Package
Refregier, Alexandre; Kitching, Thomas; Rassat, Anais
2008-01-01
iCosmo is a software package to perform interactive cosmological calculations for the low redshift universe. The computation of distance measures, the matter power spectrum, and the growth factor is supported for any values of the cosmological parameters. It also performs the computation of observables for several cosmological probes such as weak gravitational lensing, baryon acoustic oscillations and supernovae. The associated errors for these observables can be derived for customised surveys, or for pre-set values corresponding to current or planned instruments. The code also allows for the 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 library available in this language. iCosmo can also be used as an engine to perform cosmological calculations in batch mode, and forms a convenient evolutive platform for t...
Plionis, M.
2004-07-01
The recent scientific efforts in Astrophysics & Cosmology have brought a revolution to our understanding of the Cosmos. Amazing results is the outcome of amazing experiments! The huge scientific, technological & financial effort that has gone into building the 10-m class telescopes as well as many space and balloon observatories, essential to observe the multitude of cosmic phenomena in their manifestations at different wavelengths, from gamma-rays to the millimetre and the radio, has given and is still giving its fruits of knowledge. These recent scientific achievements in Observational and Theoretical Cosmology were presented in the "Multiwavelength Cosmology" conference that took place on beautiful Mykonos island in the Aegean between 17 and 20 June 2003. More than 180 Cosmologists from all over the world gathered for a four-day intense meeting in which recent results from large ground based surveys (AAT/2-df, SLOAN) and space missions (WMAP, Chandra, XMM, ISO, HST) were presented and debated, providing a huge impetus to our knowledge of the Cosmos. The future of the subject (experiments, and directions of research) was also discussed. The conference was devoted mostly on the constraints on Cosmological models and galaxy formation theories that arise from the study of the high redshift Universe, from clusters of galaxies, and their evolution, from the cosmic microwave background, the large-scale structure and star-formation history. Link: http://www.wkap.nl/prod/b/1-4020-1971-8
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)
General relativistic polytropes with a repulsive cosmological constant
Stuchlík, Zdeněk; Novotný, Jan
2016-01-01
Spherically symmetric equilibrium configurations of perfect fluid obeying a polytropic equation of state are studied in spacetimes with a repulsive cosmological constant. The configurations are specified in terms of three parameters---the polytropic index $n$, the ratio of central pressure and central energy density of matter $\\sigma$, and the ratio of energy density of vacuum and central density of matter $\\lambda$. The static equilibrium configurations are determined by two coupled first-order nonlinear differential equations that are solved by numerical methods with the exception of polytropes with $n=0$ corresponding to the configurations with a uniform distribution of energy density, when the solution is given in terms of elementary functions. The geometry of the polytropes is conveniently represented by embedding diagrams of both the ordinary space geometry and the optical reference geometry reflecting some dynamical properties of the geodesic motion. The polytropes are represented by radial profiles of...
The WiggleZ Dark Energy Survey: Final data release and cosmological results
Parkinson, David; Blake, Chris; Poole, Gregory B; Davis, Tamara M; Brough, Sarah; Colless, Matthew; Contreras, Carlos; Couch, Warrick; Croom, Scott; Croton, Darren; Drinkwater, Michael J; Forster, Karl; Gilbank, David; Gladders, Mike; Glazebrook, Karl; Jelliffe, Ben; Jurek, Russell J; Li, I-hui; Madore, Barry; Martin, D Christopher; Pimbblet, Kevin; Pracy, Michael; Sharp, Rob; Wisnioski, Emily; Woods, David; Wyder, Ted K; Yee, H K C
2012-01-01
This paper presents cosmological results from the final data release of the WiggleZ Dark Energy Survey. We perform full analyses of different cosmological models using the WiggleZ power spectra measured at z=0.22, 0.41, 0.60, and 0.78, combined with other cosmological datasets. The limiting factor in this analysis is the theoretical modelling of the galaxy power spectrum, including non-linearities, galaxy bias, and redshift-space distortions. In this paper we assess several different methods for modelling the theoretical power spectrum, testing them against the Gigaparsec WiggleZ simulations (GiggleZ). We fit for a base set of 6 cosmological parameters, {Omega_b h^2, Omega_CDM h^2, H_0, tau, A_s, n_s}, and 5 supplementary parameters {n_run, r, w, Omega_k, sum m_nu}. In combination with the Cosmic Microwave Background (CMB), our results are consistent with the LambdaCDM concordance cosmology, with a measurement of the matter density of Omega_m =0.29 +/- 0.016 and amplitude of fluctuations sigma_8 = 0.825 +/- 0...
Nonsingular bouncing cosmologies in light of BICEP2
Energy Technology Data Exchange (ETDEWEB)
Cai, Yi-Fu; Quintin, Jerome [Department of Physics, McGill University, 3600 rue University, Montréal, QC, H3A 2T8 Canada (Canada); Saridakis, Emmanuel N. [Physics Division, National Technical University of Athens, 15780 Zografou Campus, Athens (Greece); Wilson-Ewing, Edward, E-mail: yifucai@physics.mcgill.ca, E-mail: jquintin@physics.mcgill.ca, E-mail: Emmanuel_Saridakis@baylor.edu, E-mail: wilson-ewing@phys.lsu.edu [Department of Physics and Astronomy, Louisiana State University, Tower Drive, Baton Rouge, 70803 (United States)
2014-07-01
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.
The screening Horndeski cosmologies
Starobinsky, Alexei A; Volkov, Mikhail S
2016-01-01
We present a systematic analysis of homogeneous and isotropic cosmologies in a particular Horndeski model with Galileon shift symmetry, containing also a $\\Lambda$-term and a matter. The model, sometimes called Fab Five, admits a rich spectrum of solutions. Some of them describe the standard late time cosmological dynamic dominated by the $\\Lambda$-term and matter, while at the early times the universe expands with a constant Hubble rate determined by the value of the scalar kinetic coupling. For other solutions the $\\Lambda$-term and matter are screened at all times but there are nevertheless the early and late accelerating phases. The model also admits bounces, as well as peculiar solutions describing "the emergence of time". Most of these solutions contain ghosts in the scalar and tensor sectors. However, a careful analysis reveals three different branches of ghost-free solutions, all showing a late time acceleration phase. We analyze the dynamical stability of these solutions and find that all of them are...
Davydov, Evgeny
2011-01-01
Vector fields can arise in the cosmological context in different ways, and we discuss both abelian and nonabelian sector. In the abelian sector vector fields of the geometrical origin (from dimensional reduction and Einstein-Eddington modification of gravity) can provide a very non-trivial dynamics, which can be expressed in terms of the effective dilaton-scalar gravity with the specific potential. In the non-abelian sector we investigate the Yang-Mills SU(2) theory which admits isotropic and homogeneous configuration. Provided the non-linear dependence of the lagrangian on the invariant F*F(dual), one can obtain the inflationary regime with the exponential growth of the scale factor. The effective amplitudes of the 'electric' and 'magnetic' components behave like slowly varying scalars at this regime, what allows the consideration of some realistic models with non-linear terms in the Yang-Mills lagrangian.
The screening Horndeski cosmologies
Energy Technology Data Exchange (ETDEWEB)
Starobinsky, Alexei A. [L.D. Landau Institute for Theoretical Physics RAS,Moscow 119334 (Russian Federation); Department of General Relativity and Gravitation, Institute of Physics,Kazan Federal University,Kremlevskaya street 18, 420008 Kazan (Russian Federation); Sushkov, Sergey V. [Department of General Relativity and Gravitation, Institute of Physics,Kazan Federal University,Kremlevskaya street 18, 420008 Kazan (Russian Federation); Volkov, Mikhail S. [Laboratoire de Mathématiques et Physique Théorique CNRS-UMR 7350,Université de Tours,Parc de Grandmont, 37200 Tours (France); Department of General Relativity and Gravitation, Institute of Physics,Kazan Federal University,Kremlevskaya street 18, 420008 Kazan (Russian Federation)
2016-06-06
We present a systematic analysis of homogeneous and isotropic cosmologies in a particular Horndeski model with Galileon shift symmetry, containing also a Λ-term and a matter. The model, sometimes called Fab Five, admits a rich spectrum of solutions. Some of them describe the standard late time cosmological dynamic dominated by the Λ-term and matter, while at the early times the universe expands with a constant Hubble rate determined by the value of the scalar kinetic coupling. For other solutions the Λ-term and matter are screened at all times but there are nevertheless the early and late accelerating phases. The model also admits bounces, as well as peculiar solutions describing “the emergence of time”. Most of these solutions contain ghosts in the scalar and tensor sectors. However, a careful analysis reveals three different branches of ghost-free solutions, all showing a late time acceleration phase. We analyse the dynamical stability of these solutions and find that all of them are stable in the future, since all their perturbations stay bounded at late times. However, they all turn out to be unstable in the past, as their perturbations grow violently when one approaches the initial spacetime singularity. We therefore conclude that the model has no viable solutions describing the whole of the cosmological history, although it may describe the current acceleration phase. We also check that the flat space solution is ghost-free in the model, but it may acquire ghost in more general versions of the Horndeski theory.
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
Directory of Open Access Journals (Sweden)
Gianguido Dall'Agata
2016-01-01
Full Text Available 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.
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
Gill, S P D; Gibson, B K; Flynn, C; Ibata, R A; Lewis, G F; Gill, Stuart P.D.; Knebe, Alexander; Gibson, Brad K.; Flynn, Chris; Ibata, Rodrigo A.; Lewis, Geraint F.
2002-01-01
An adaptive multi grid approach to simulating the formation of structure from collisionless dark matter is described. MLAPM (Multi-Level Adaptive Particle Mesh) is one of the most efficient serial codes available on the cosmological 'market' today. As part of Swinburne University's role in the development of the Square Kilometer Array, we are implementing hydrodynamics, feedback, and radiative transfer within the MLAPM adaptive mesh, in order to simulate baryonic processes relevant to the interstellar and intergalactic media at high redshift. We will outline our progress to date in applying the existing MLAPM to a study of the decay of satellite galaxies within massive host potentials.
Gelmini, Graciela B
1996-01-01
Talks given at the V Taller de Particulas y Campos (V-TPyC) and V Taller Latinoam. de Fenomenologia de las Interac. Fundam. (V-TLFIF), Puebla, Mexico, 10/30 - 11/3 1995. 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 neighbourhood, 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 format...
Symmetries of homogeneous cosmologies
Cotsakis, S; Pantazi, H; Cotsakis, Spiros; Leach, Peter; Pantazi, Hara
1998-01-01
We reformulate the dynamics of homogeneous cosmologies with a scalar field matter source with an arbitrary self-interaction potential in the language of jet bundles and extensions of vector fields. In this framework, the Bianchi-scalar field equations become subsets of the second Bianchi jet bundle, $J^2$, and every Bianchi cosmology is naturally extended to live on a variety of $J^2$. We are interested in the existence and behaviour of extensions of arbitrary Bianchi-Lie and variational vector fields acting on the Bianchi variety and accordingly we classify all such vector fields corresponding to both Bianchi classes $A$ and $B$. We give examples of functions defined on Bianchi jet bundles which are constant along some Bianchi models (first integrals) and use these to find particular solutions in the Bianchi total space. We discuss how our approach could be used to shed new light to questions like isotropization and the nature of singularities of homogeneous cosmologies by examining the behaviour of the vari...
Neves, J C S
2015-01-01
In the Nietzschean philosophy, the concept of force from physics is important to build one of its main concepts: the will to power. The concept of force, which Nietzsche found out in the Classical Mechanics, almost disappears in the physics of the XX century with the Quantum Field Theory and General Relativity. Is the Nietzschean world as contending forces, a Dionysian cosmology, possible in the current science?
Alvarez, Enrique
1985-01-01
Some cosmological consequences of the assumption that superstrings are more fundamental objects than ordinary local quantum fields are examined. We study, in particular, the dependence of both the string tension and the temperature of the primordial string soup on cosmic time. A particular scenario is proposed in which the universe undergoes a contracting ``string phase'' before the ordinary ``big bang,'' which according to this picture is nothing but the outcome of the transition from nonlocal to local fundamental physics.
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 ...
Incorporation of Mach's Principle in ΛFRW Cosmology that depends dynamically of the distance range
Falcon, N.
2017-07-01
It postulates a FRW cosmological model without dark matter and cosmological term depending the distance scale, in addition to incorporate Mach's principle, is consistent with the observations: rotation curves of the galaxies, the nucleosynthesis primordial and CMB. The dynamic expression of Cosmological term is an alternative to non-baryonic dark matter and a reinterpretation of dark energy.
Cosmological evolution in exponential gravity
Energy Technology Data Exchange (ETDEWEB)
Bamba, Kazuharu; Geng, Chao-Qiang; Lee, Chung-Chi, E-mail: bamba@phys.nthu.edu.tw, E-mail: geng@phys.nthu.edu.tw, E-mail: g9522545@oz.nthu.edu.tw [Department of Physics, National Tsing Hua University, Hsinchu, Taiwan (China)
2010-08-01
We explore the cosmological evolution in the exponential gravity f(R) = R+c{sub 1}(1−e{sup −c{sub 2}R}) (c{sub 1,2} = constant). We summarize various viability conditions and explicitly demonstrate that the late-time cosmic acceleration following the matter-dominated stage can be realized. We also study the equation of state for dark energy and confirm that the crossing of the phantom divide from the phantom phase to the non-phantom (quintessence) one can occur. Furthermore, we illustrate that the cosmological horizon entropy globally increases with time.
Cosmological evolution in exponential gravity
Bamba, Kazuharu; Lee, Chung-Chi
2010-01-01
We explore the cosmological evolution in the exponential gravity $f(R)=R +c_1 \\left(1-e^{- c_2 R} \\right)$ ($c_{1, 2} = \\mathrm{constant}$). We summarize various viability conditions and explicitly demonstrate that the late-time cosmic acceleration following the matter-dominated stage can be realized. We also study the equation of state for dark energy and confirm that the crossing of the phantom divide from the phantom phase to the non-phantom (quintessence) one can occur. Furthermore, we illustrate that the cosmological horizon entropy globally increases with time.
Mendes, L E; Mendes, Luis E.; Mazumdar, Anupam
2001-01-01
A five dimensional brane cosmology with non-minimally coupled scalar field to gravity has been considered in a Jordan-Brans-Dicke frame. We derive an effective four dimensional field equations on a 3+1 dimensional brane where the fifth dimension has been assumed to have an orbifold symmetry. We have noticed that the evolution equation for the matter component stuck to the brane is non-trivially coupled to the scalar field living on the brane and the bulk. Finally we discuss some cosmological consequences of this set-up.
Cosmological dynamics of extended chameleons
Tamanini, Nicola
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 $\\Lambda$CDM 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.
Gauge Invariant Cosmological Perturbation Theory
Durrer, R
1993-01-01
After an introduction to the problem of cosmological structure formation, we develop gauge invariant cosmological perturbation theory. We derive the first order perturbation equations of Einstein's equations and energy momentum ``conservation''. Furthermore, the perturbations of Liouville's equation for collisionless particles and Boltzmann's equation for Compton scattering are worked out. We fully discuss the propagation of photons in a perturbed Friedmann universe, calculating the Sachs--Wolfe effect and light deflection. The perturbation equations are extended to accommodate also perturbations induced by seeds. With these general results we discuss some of the main aspects of the texture model for the formation of large scale structure in the Universe (galaxies, clusters, sheets, voids). In this model, perturbations in the dark matter are induced by texture seeds. The gravitational effects of a spherically symmetric collapsing texture on dark matter, baryonic matter and photons are calculated in first orde...
Precision cosmology in muddy waters: Cosmological constraints and N-body codes
Smith, Robert E; Potter, Doug; Marian, Laura; Crocce, Martin; Moore, Ben
2012-01-01
Future large-scale structure surveys of the Universe will aim to constrain the cosmological model and the true nature of dark energy with unprecedented accuracy. In order for these surveys to achieve their designed goals, they will require predictions for the nonlinear matter power spectrum to sub-percent accuracy. Through the use of a large ensemble of cosmological N-body simulations, we demonstrate that if we do not understand the uncertainties associated with simulating structure formation, i.e. knowledge of the `true' simulation parameters, and simply seek to marginalize over them, then the constraining power of such future surveys can be significantly reduced. However, for the parameters {n_s, h, Om_b, Om_m}, this effect can be largely mitigated by adding the information from a CMB experiment, like Planck. In contrast, for the amplitude of fluctuations sigma8 and the time-evolving equation of state of dark energy {w_0, w_a}, the mitigation is mild. On marginalizing over the simulation parameters, we find...
Shortcuts in Cosmological Branes
Abdalla, Elcio; Cuadros-Melgar, B; Abdalla, Elcio; Casali, Adenauer G.; Cuadros-Melgar, Bertha
2004-01-01
We aim at gathering information from gravitational interaction in the Universe, at energies where quantum gravity is required. In such a setup a dynamical membrane world in a space-time with scalar bulk matter described by domain walls, as well as a dynamical membrane world in empty Anti de Sitter space-time are analysed. We later investigate the possibility of having shortcuts for gravitons leaving the membrane and returning subsequently. In comparison with photons following a geodesic inside the brane, we verify that shortcuts exist. For late time universes they are small, but for some primordial universes they can be quite effective. In the case of matter branes, we argue that at times just before nucleosynthesis the effect is sufficiently large to provide corrections to the inflationary scenario, especially as concerning the horizon problem and the Cosmological Background Radiation.
Cosmological Structure Formation
Primack, Joel R
2015-01-01
LCDM is remarkably successful in predicting the cosmic microwave background and large-scale structure, and LCDM parameters have been determined with only mild tensions between different types of observations. Hydrodynamical simulations starting from cosmological initial conditions are increasingly able to capture the complex interactions between dark matter and baryonic matter in galaxy formation. Simulations with relatively low resolution now succeed in describing the overall galaxy population. For example, the EAGLE simulation in volumes up to 100 cubic Mpc reproduces the observed local galaxy mass function nearly as well as semi-analytic models. It once seemed that galaxies are pretty smooth, that they generally grow in size as they evolve, and that they are a combination of disks and spheroids. But recent HST observations combined with high-resolution hydrodynamic simulations are showing that most star-forming galaxies are very clumpy; that galaxies often undergo compaction which reduces their radius and ...
Particle astrophysics of nonlinear supersymmetric general relativity
Energy Technology Data Exchange (ETDEWEB)
Shima, K.; Tsuda, M. [Laboratory of Physics, Saitama Institute of Technology, Fukaya, Saitama (Japan)
2009-05-15
An explanation of relations between the large scale structure of the universe and the tiny scale structure of the particle physics, e.g. the observed mysterious relation between the (dark) energy density and the dark matter of the universe and the neutrino mass and the SUSY breaking mass scale of the particle physics may be given by the nonlinear supersymmetric general relativity (NLSUSY GR). NLSUSY GR shows that considering the physics before/of the big bang (BB) of the universe may be significant and may give new insight to unsolved problems of the low energy particle physics, cosmology and their relations. (Abstract Copyright [2009], Wiley Periodicals, Inc.)
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 Λ 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.
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.
Szydlowski, Marek; Borowiec, Andrzej; Wojnar, Aneta
2015-01-01
We investigate modified gravity cosmological model $f(R)=R+\\gamma R^2$ in Palatini formalism. We consider the universe filled with the Chaplygin gas and baryonic matter. The dynamics is reduced to the 2D sewn dynamical system of a Newtonian type. For this aim we use dynamical system theory. We classify all evolutional paths in the model as well as trajectories in the phase space. We demonstrate that the presence of a degenerate freeze singularity (glued freeze type singularities) is a generic feature of early evolution of the universe. We point out that a degenerate type III of singularity can be considered as an endogenous model of inflation between the matter dominating epoch and the dark energy phase. We also investigate cosmological models with negative $\\gamma$. It is demonstrated that $\\gamma$ equal zero is a bifurcation parameter and dynamics qualitatively changes in comparison to positive $\\gamma$. Instead of the big bang the sudden singularity appears and there is a generic class of bouncing solution...
Interacting galaxies and cosmological parameters
Reboul, H
2006-01-01
We propose a (physical)-geometrical method to measure the present rates of the density cosmological parameters for a Friedmann-Lemaitre universe. The distribution of linear separations between two interacting galaxies,when both of them undergo a first massive starburst, is used as a standard of length. Statistical properties of the linear separations of such pairs of ``interactivated'' galaxies are estimated from the data in the Two Degree Field Galaxy Redshift Survey. Synthetic samples of interactivated pairs are generated with random orientations and a likely distribution of redshifts. The resolution of the inverse problem provides the probability densities of the retrieved cosmological parameters. The accuracies that can be achieved by that method on matter and cosmological constant densities parameters are computed depending on the size of ongoing real samples. Observational prospects are investigated as the foreseeable surface densities on the sky and magnitudes of those objects.
FAST-PT: a novel algorithm to calculate convolution integrals in cosmological perturbation theory
McEwen, Joseph E.; Fang, Xiao; Hirata, Christopher M.; Blazek, Jonathan A.
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.
FAST-PT: a novel algorithm to calculate convolution integrals in cosmological perturbation theory
McEwen, Joseph E; Hirata, Christopher M; Blazek, Jonathan A
2016-01-01
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, including the applications described here.
Problems and Challenges for Cosmology involving Massive Neutrinos
Krauss, L M
1996-01-01
I review the challenges and problems facing the standard cosmological model, involving an $\\Omega=1$ Universe dominated by non-baryonic dark matter, which arise due to: age estimates of the universe, estimates of the baryon fraction of the universe, and structure formation. Certain of these problems are exacerbated, and certain of these are eased, by the inclusion of some component to the energy density of matter from massive neutrinos. I conclude with a comparison of the two favored current cosmological models, involving either a mixture of cold dark matter and hot dark matter, or the inclusion of a cosmological constant.
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.
Cold electroweak baryogenesis and quantum cosmological correlations
M.P. van der Meulen
2008-01-01
This thesis describes two subjects from theoretical cosmology. The first concerns the creation of the matter--anti-matter asymmetry, which is generally assumed to be created in the early universe by a process called baryogenesis. The details of this process are yet unknown and there exist many model
Dolgov, A. D.
These lectures have been given to particle physicists, mostly experimentalists and very briefly and at a pedestrian level review the problems of dark matter. The content of the lectures is the following: 1. Introduction. 2. Cosmological background. 3. Luminous matter. 4. Primordial nucleosynthesis and the total amount of baryons. 5. Gravitating invisible matter. 6. Baryonic crisis. 7. Inflationary omega. 8. Intermediate summary. 9. Possible forms of dark matter. 10. Structure formation: basic assumptions. 11. Structure formations: basics of the theory. 12. Evolution of perturbations with different forms of dark matter. 13. Conclusion. The presentation and conclusion reflect personal view of the author that a considerable amount of invisible energy in the universe is in the form of vacuum energy (cosmological constant) and possibly in the form of a classical field which adjusts vacuum energy to the value permitted and requested by astronomical data.
Modified Gravity or Dark Matter?
Moffat, J W
2011-01-01
Modified Gravity (MOG) has been used successfully to explain the rotation curves of galaxies, the motion of galaxy clusters, the Bullet Cluster, and cosmological observations without the use of dark matter or Einstein's cosmological constant. We review the main theoretical ideas and applications of the theory to astrophysical and cosmological data.
The velocity field in MOND cosmology
Candlish, G N
2016-01-01
The recently developed code for N-body/hydrodynamics simulations in Modified Newtonian Dynamics (MOND), known as RAyMOND, is used to investigate the consequences of MOND on structure formation in a cosmological context, with a particular focus on the velocity field. This preliminary study investigates the results obtained with the two formulations of MOND implemented in RAyMOND, as well as considering the effects of changing the choice of MOND interpolation function, and the cosmological evolution of the MOND acceleration scale. The simulations are contrived such that structure forms in a background cosmology that is similar to $\\Lambda$CDM, but with a significantly lower matter content. Given this, and the fact that a fully consistent MOND cosmology is still lacking, we compare our results with a standard $\\Lambda$CDM simulation, rather than observations. As well as demonstrating the effectiveness of using RAyMOND for cosmological simulations, it is shown that a significant enhancement of the velocity field ...
Cosmic curvature from de Sitter equilibrium cosmology.
Albrecht, Andreas
2011-10-01
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.
N-body simulations of coupled dark energy cosmologies
Baldi, Marco; Robbers, Georg; Springel, Volker
2008-01-01
If the accelerated expansion of the Universe at the present epoch is driven by a dark energy scalar field, there may well be a non-trivial coupling between the dark energy and the cold dark matter (CDM) fluid. Such interactions give rise to new features in cosmological structure growth, like an additional long-range attractive force between CDM particles, or variations of the dark matter particle mass with time. We have implemented these effects in the N-body code GADGET-2 and present results of a series of high-resolution N-body simulations where the dark energy component is directly interacting with the cold dark matter. As a consequence of the new physics, CDM and baryon distributions evolve differently both in the linear and in the nonlinear regime of structure formation. Already on large scales a linear bias develops between these two components, which is further enhanced by the nonlinear evolution. We also find, in contrast with previous work, that the density profiles of CDM halos are less concentrated...
Geometrically nonlinear deformation and the emergent behavior of polarons in soft matter.
Li, Xiaobao; Liu, Liping; Sharma, Pradeep
2015-11-07
Mechanical strain can alter the electronic structure of both bulk semiconductors as well as nanostructures such as quantum dots. This fact has been extensively researched and exploited for tailoring electronic properties. The strain mediated interaction between the charge carriers and the lattice is interpreted through the so-called deformation potential. In the case of soft materials or nanostructures, such as DNA, the deformation potential leads to the formation of polarons which largely determine the electronic characteristics of DNA and similar polymer entities. In addition, polarons are also speculated to be responsible for the mechanism of quantum actuation in carbon nanotubes. The deformation potential is usually taken to be a linear function of the lattice deformation (U ∼ αε) where α is the deformation potential "constant" that determines the coupling strength and ε is the mechanical strain. In this letter, by carefully accounting for nonlinear geometric deformation that has been hitherto ignored so far in this context, we show that the deformation potential constant is renormalized in a non-trivial manner and is hardly a constant. It varies spatially within the material and with the size of the material. This effect, while negligible for hard materials, is found to be important for soft materials and critically impacts the interpretation of quantities such as polaron size, binding energy, and accordingly, electronic behavior.
Agarwal, Nishant; Khoury, Justin; Trodden, Mark
2009-01-01
We develop a fully covariant, well-posed 5D effective action for the 6D cascading gravity brane-world model, and use this to study cosmological solutions. We obtain this effective action through the 6D decoupling limit, in which an additional scalar degree mode, \\pi, called the brane-bending mode, determines the bulk-brane gravitational interaction. The 5D action obtained this way inherits from the sixth dimension an extra \\pi self-interaction kinetic term. We compute appropriate boundary terms, to supplement the 5D action, and hence derive fully covariant junction conditions and the 5D Einstein field equations. Using these, we derive the cosmological evolution induced on a 3-brane moving in a static bulk. We study the strong- and weak-coupling regimes analytically in this static ansatz, and perform a complete numerical analysis of our solution. Although the cascading model can generate an accelerating solution in which the \\pi field comes to dominate at late times, the presence of a critical singularity prev...
Newtonian cosmology - Problems of cosmological didactics
Energy Technology Data Exchange (ETDEWEB)
Skarzynski, E.
1983-03-01
The article presents different methods of model construction in Newtonian cosmology. Newtonian cosmology is very convenient for discussion of local problems, so the problems presented are of great didactic importance. The constant k receives a new interpretation in relativistic cosmology as the curvature of the space in consequence of the greater informational capacity of Riemann space in comparison to Euclidean space. 11 references.
Vacuum solutions of Bianchi cosmologies in quadratic gravity
Energy Technology Data Exchange (ETDEWEB)
Deus, Juliano Alves de; Muller, Daniel [Universidade de Brasilia (UnB), DF (Brazil)
2011-07-01
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{sub 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)