Search

We study cosmological perturbations in a model of unified dark matter and dark energy with a sharp transition in the late-time universe. The dark sector is described by a dark fluid which evolves from an early stage at redshifts $z > z_C$ when it behaves as cold dark matter (CDM) to a late time dark energy (DE) phase ($z < z_C$) when the equation of state parameter is $w = -1 + \epsilon$, with a constant $\epsilon$ which must be in the range $0 < \epsilon < 2/3$. We show that fluctuations in the dark energy phase suffer from an exponential instability, the mode functions growing both as a function of comoving momentum $k$ and of conformal time $\eta$. In order that this exponential instability does not lead to distortions of the energy density power spectrum on scales for which we have good observational results, the redshift $z_C$ of transition between the two phases is constrained to be so close to zero that the model is unable to explain the supernova data., Comment: 17 pages; 2 figures; v2: minor changes to match the published version

The generalized Chaplygin gas could be considered as the unified dark fluid model because it might describe the past decelerating matter dominated era and at present time it provides an accelerating expansion of the Universe. In this paper, we employed the Planck 2015 cosmic microwave background anisotropy, type-Ia supernovae, observed Hubble parameter data sets to measure the full parameter space of the generalized Chaplygin gas as an unified dark matter and dark energy model. The model parameters B s and α determine the evolutional history of this unified dark fluid model by influencing the energy density ρ G C G = ρ G C G 0 [ B s + ( 1 − B s ) a − 3 ( 1 + α ) ] 1 ∕ ( 1 + α ) . We assume the pure adiabatic perturbation of unified generalized Chaplygin gas. In the light of Markov Chain Monte Carlo method, we found that B s = 0 . 75 9 − 0 . 032 − 0 . 046 + 0 . 020 + 0 . 051 and α = 0 . 080 1 − 0 . 0801 − 0 . 0801 + 0 . 0208 + 0 . 1087 at 2 σ level. The model parameter α is very close to zero, the nature of GCG model is very similar to cosmological standard model Λ CDM.

Two-Higgs-Doublet Model of Type-X in the large $\tan\beta$ limit becomes leptophilic to allow a light pseudo-scalar $A$ and thus provides an explanation of the muon $g-2$ anomaly. Introducing a singlet scalar dark matter $S$ in this context, one finds that two important dark matter properties, nucleonic scattering and self-annihilation, are featured separately by individual couplings of dark matter to the two Higgs doublets. While one of the two couplings is strongly constrained by direct detection experiments, the other remains free to be adjusted for the relic density mainly through the process $SS\to AA$. This leads to the $4\tau$ final states which can be probed by galactic gamma ray detections., Comment: Accepted version in Physics Letters B

In this paper, we will study some properties of oscillatons, spherically symmetric object made of a real time-dependent scalar field, using a self-interaction quartic scalar field potential as a class of what is called Self-Interacting Dark Matter (SIDM) models. Since the oscillatons can be regarded as models for astrophysical objects which play the role of dark matter, therefore investigation of their properties could have an important place in present time of cosmology researches. We investigate the properties of these objects by Numerical Solving the system of differential equations obtained from the Einstein–Klein–Gordon (EKG) equations to show their importance as new candidates for dark matter in the galactic scales.

The generalized Chaplygin gas cosmology provides a prime example for the class of unified dark matter models, which substitute the two dark components of the standard cosmological ΛCDM concordance model by a single dark component. The equation of state of the generalized Chaplygin gas is characterised by a parameter α such that the standard ΛCDM model is recovered in the case α = 0 with respect to the background dynamics and the cosmic microwave background (CMB) statistics. This allows to investigate the concordance of different cosmological data sets with respect to α. We compare the supernova data of the Supernova Cosmology Project, the data of the baryon oscillation spectroscopic survey (BOSS) of the third Sloan digital sky survey (SDSS-III) and the CMB data of the Planck 2015 data release. The importance of the BOSS Lyman α forest BAO measurements is investigated. It is found that these data sets possess a common overlap of the confidence domains only for Chaplygin gas cosmologies very close to the ΛCDM model.

In this paper, we have constructed Wet Dark Fluid (WDF) model in an anisotropic homogeneous space-time namely Marder’s space time. We discussed two type of models as: power law expansion model and exponential expansion model. Also some physical parameters of the model are obtained and discussed.

In this paper, we investigate the possibility that the Universe is driven by a single dark fluid described by a Lambert $W$ equation of state parameter, $w_{eff}$, which is essentially dependent on two parameters $\vartheta_{1}$ and $\vartheta_{2}$ which need to be fixed from observations. We obtain the constraints on these parameters using the latest 51 data points of $H(z)$ measurements, spanning the redshift range $0.07\leq z \leq 2.36$. The present study shows that the Universe is indeed undergoing an accelerated expansion phase following the decelerated one at the transition redshift, $z_{t}=0.77\pm0.03$ ($1\sigma$) and is well consistent with the recent observations. We also find that at low redshifts, $w_{eff}$ evolves only in the quintessence regime ($-1, Comment: 11 pages, 6 figures

In this paper, we study the anisotropic Bianchi type-VI 0 metric filled with dark matter and anisotropic ghost dark energy. We have solved the Einstein's field equations by considering hybrid expansion law (HEL) for the average scale factor. It is found that at later times the universe becomes spatially homogeneous, isotropic and flat. From a state finder diagnosis, it is found that our model is having similar behavior like ɅCDM model at late phase of cosmic time.

We consider a dark sector consisting of dark matter that is a Dirac fermion and a scalar mediator. This model has been extensively studied in the past. If the scalar couples to the dark matter in a parity conserving manner then dark matter annihilation to two mediators is dominated by the P-wave channel and hence is suppressed at very low momentum. The indirect detection constraint from the anisotropy of the Cosmic Microwave Background is usually thought to be absent in the model because of this suppression. In this letter we show that dark matter annihilation to bound states occurs through the S-wave and hence there is a constraint on the parameter space of the model from the Cosmic Microwave Background., 5 pages, 3 figures

Recently we reported on the condensation of cold, electrostatically trapped dipolar excitons in GaAs bilayer heterostructure into a new, dense and dark collective phase. Here we analyze and discuss in detail the experimental findings and the emerging evident properties of this collective liquid-like phase. We show that the phase transition is characterized by a sharp increase of the number of non-emitting dipoles, by a clear contraction of the fluid spatial extent into the bottom of the parabolic-like trap, and by spectral narrowing. We extract the total density of the condensed phase which we find to be consistent with the expected density regime of a quantum liquid. We show that there are clear critical temperature and excitation power onsets for the phase transition and that as the power further increases above the critical power, the strong darkening is reduced down until no clear darkening is observed. At this point another transition appears which we interpret as a transition to a strongly repulsive yet correlated e - h plasma. Based on the experimental findings, we suggest that the physical mechanism that may be responsible for the transition is a dynamical final-state stimulation of the dipolar excitons to their dark spin states, which have a long lifetime and thus support the observed sharp increase in density. Further experiments and modeling will hopefully be able to unambiguously identify the physical mechanism behind these recent observations.

A unification of dark matter and dark energy in terms of a logotropic perfect dark fluid has recently been proposed, where deviations with respect to the standard ΛCDM model are dependent on a single parameter B. In this paper we show that the requirement that the linear growth of cosmic structures on comoving scales larger than 8 h − 1 Mpc is not significantly affected with respect to the standard ΛCDM result provides the strongest limit to date on the model ( B 6 × 10 − 7 ), an improvement of more than three orders of magnitude over previous upper limits on the value of B. We further show that this limit rules out the logotropic Unified Dark Energy model as a possible solution to the small scale problems of the Λ CDM model, including the cusp problem of Dark Matter halos or the missing satellite problem, as well as the original version of the model where the Planck energy density was taken as one of the two parameters characterizing the logotropic dark fluid.

In this study, we propose a novel dark cosmology consisting an interacting q -deformed spinor field dark matter and scalar field dark energy. We investigate the proposed deformed dark cosmology in metric-affine Einstein– Cartan–Sciama–Kibble theory. Firstly, we construct the action integral of the model, in order to obtain the energy–momentum tensor of the deformed dark matter and dark energy, from which the energy density and pressure of the deformed dark matter and dark energy can be obtained, respectively. After obtaining the deformed energy densities and pressures, we set up the Friedmann equations, continuity equations and equation of motions for this dark model. Then, we obtain the attractor solutions and stability analysis of the model for the accelerated expansion phase of the universe. We also investigate the effect of deformation parameter on the stable accelerated expansion behavior. Consequently, by mapping the interaction term and the field potentials we present the relationship between them and obtain the constraint on the interaction term in order to obtain a stable attractor solution.

The cosmological model of cold dark matter (CDM) with the dark energy and a scale-invariant adiabatic primordial power spectrum has been considered as the standard cosmological model, i.e. the ΛCDM model. Weakly interacting massive particles (WIMPs) become a prominent candidate for the CDM. Many models extended from the standard model can provide the WIMPs naturally. The standard calculations of relic abundance of dark matter show that the WIMPs are well in agreement with the astronomical observation of ΩDM h2 ≈0.11. The WIMPs have a relatively large mass, and a relatively slow velocity, so they are easy to aggregate into clusters, and the results of numerical simulations based on the WIMPs agree well with the observational results of cosmic large-scale structures. In the aspect of experiments, the present accelerator or non-accelerator direct/indirect detections are mostly designed for the WIMPs. Thus, a wide attention has been paid to the CDM model based on the WIMPs. However, the ΛCDM model has a serious problem for explaining the small-scale structures under one Mpc. Different dark matter models have been proposed to alleviate the small-scale problem. However, so far there is no strong evidence enough to exclude the CDM model. We plan to introduce the research progress of the dark matter model based on the WIMPs, such as the WIMPs miracle, numerical simulation, small-scale problem, and the direct/indirect detection, to analyze the criterion for discriminating the “cold”, “hot”, and “warm” dark matter, and present the future prospects for the study in this field.

Based on the cosmological hydrodynamic simulations, we investigate the correlations between the spin, velocity shear and vorticity in dark matter halos, as well as the relationship between the baryonic matter and the dark matter. We find that (1) the difference between the vorticity of baryonic matter and that of dark matter is evident on the scales of −1 Mpc; (2) the vorticity of baryonic matter exhibits a stronger correlation with the tensor of velocity shear than the vorticity of dark matter does; and (3) the spinning direction of small-mass dark matter halos tends to be parallel to the direction of their host filaments, while the spinning direction of massive dark matter halos tends to be perpendicular to the direction of their host filaments, and the intensity of this kind correlation depends on the size of simulation box, and the simulation accuracy. These factors may cause the relationship between the the spins of dark matter halos and those of galaxies to be complicated, and affect the correlation between the galaxy spins and the nearby large-scale structures.

Yes, but only for a parameter value that makes it almost coincide with the standard model. We reconsider the cosmological dynamics of a generalized Chaplygin gas (gCg) which is split into a cold dark matter (CDM) part and a dark energy (DE) component with constant equation of state. This model, which implies a specific interaction between CDM and DE, has a Λ CDM limit and provides the basis for studying deviations from the latter. Including matter and radiation, we use the (modified) CLASS code (Blas et al., 2011) to construct the CMB and matter power spectra in order to search for a gCg-based concordance model that is in agreement with the SNIa data from the JLA sample and with recent Planck data. The results reveal that the gCg parameter α is restricted to | α | ≲ 0 . 05 , i.e., to values very close to the Λ CDM limit α = 0 . This excludes, in particular, models in which DE decays linearly with the Hubble rate.

We explore the relic abundance of asymmetric Dark Matter in shear--dominated universe in which it is assumed the universe is expanded anisotropically. The modified expansion rate leaves its imprint on the relic density of asymmetric Dark Matter particles if the asymmetric Dark Matter particles are decoupled in shear dominated era. We found the relic abundances for particle and anti--particle are increased. The particle and anti--particle abundances are almost in the same amount for the larger value of the shear factor $x_e$ which makes the indirect detection possible for asymmetric Dark Matter. We use the present day Dark Matter density from the observation to find the constraints on the parameter space in this model., 12 pages, 6 figures

The simplest Higgs-portal dark matter model is studied in the light of dark matter self-interacting effects on the formation of large scale structures. We show the direct detection limits on the resonant and large mass regions. Finally, we also compare these limits with those at the LHC and Xenon 1T experiments., Published version, references added

AGN jets carry helical magnetic fields, which can affect dark matter if the latter is axionic. This preliminary study shows that, in the presence of strong helical magnetic fields, the nature of the axionic condensate may change and become dark energy. Such dark energy may affect galaxy formation and galactic dynamics, so this possibility should not be ignored when considering axionic dark matter., 8 pages, published version

In this letter, we consider a class of scenarios in which the dark matter is part of a heavy hidden sector that is thermally decoupled from the Standard Model in the early universe. The dark matter freezes-out by annihilating to a lighter, metastable state, whose subsequent abundance can naturally come to dominate the energy density of the universe. When this state decays, it reheats the visible sector and dilutes all relic abundances, thereby allowing the dark matter to be orders of magnitude heavier than the weak scale. For concreteness, we consider a simple realization with a Dirac fermion dark matter candidate coupled to a massive gauge boson that decays to the Standard Model through its kinetic mixing with hypercharge. We identify viable parameter space in which the dark matter can be as heavy as ~1-100 PeV without being overproduced in the early universe., Comment: 4 pages + appendices, 2 figures

General considerations in general relativity and quantum mechanics are known to potentially rule out continuous global symmetries in the context of any consistent theory of quantum gravity. Assuming the validity of such considerations, we derive stringent bounds from gamma-ray, X-ray, cosmic-ray, neutrino, and CMB data on models that invoke global symmetries to stabilize the dark matter particle. We compute up-to-date, robust model-independent limits on the dark matter lifetime for a variety of Planck-scale suppressed dimension-five effective operators. We then specialize our analysis and apply our bounds to specific models including the Two-Higgs-Doublet, Left-Right, Singlet Fermionic, Zee-Babu, 3-3-1 and Radiative See-Saw models. {Assuming that (i) global symmetries are broken at the Planck scale, that (ii) the non-renormalizable operators mediating dark matter decay have $O(1)$ couplings, that (iii) the dark matter is a singlet field, and that (iv) the dark matter density distribution is well described by a NFW profile}, we are able to rule out fermionic, vector, and scalar dark matter candidates across a broad mass range (keV-TeV), including the WIMP regime., Matches Published version in Phys.Lett. B760 (2016) 807-815

Spare a thought for the dark-matter hunters. Every time they're on the verge of trapping the elusive stuff thought to make up the bulk of the universe's matter, it slips away. They don't see the expected signals, or they spot something exciting only to watch it fade into background noise. Each time it's the same: put on a brave face, go back to the drawing board and begin the hunt again. Perhaps it's time for a change of tack. Instead of going after a single species of dark matter particle, maybe people should be looking for a menagerie of dark particles and forces--a whole new "dark sector." After all, there is no reason to think dark matter will be any less intricate than the visible stuff they consider ordinary, with its panoply of particles from electrons to quarks. Here, Clark discusses the entire shadow world in which invisible particles influence one another through forces unfelt by the familiar stuff of stars and planets and people.

We propose a heuristic unification of dark matter and dark energy in terms of a single dark fluid with a logotropic equation of state $P=A\ln(\rho/\rho_P)$, where $\rho$ is the rest-mass density, $\rho_P$ is the Planck density, and $A$ is the logotropic temperature. The energy density $\epsilon$ is the sum of a rest-mass energy term $\rho c^2$ mimicking dark matter and an internal energy term $u(\rho)=-P(\rho)-A$ mimicking dark energy. The logotropic temperature is approximately given by $A \simeq \rho_{\Lambda}c^2/\ln(\rho_P/\rho_{\Lambda})\simeq\rho_{\Lambda}c^2/[123 \ln(10)]$, where $\rho_{\Lambda}$ is the cosmological density. More precisely, we obtain $A=2.13\times 10^{-9} \, {\rm g}\, {\rm m}^{-1}\, {\rm s}^{-2}$ that we interpret as a fundamental constant. At the cosmological scale, this model fullfills the same observational constraints as the $\Lambda$CDM model. However, it has a nonzero velocity of sound and a nonzero Jeans length which, at the beginning of the matter era, is about $\lambda_J=40.4\, {\rm pc}$, in agreement with the minimum size of the dark matter halos observed in the universe. At the galactic scale, the logotropic pressure balances gravitational attraction and solves the cusp problem and the missing satellite problem. The logotropic equation of state generates a universal rotation curve that agrees with the empirical Burkert profile of dark matter halos up to the halo radius. In addition, it implies that all the dark matter halos have the same surface density $\Sigma_0=\rho_0 r_h=141\, M_{\odot}/{\rm pc}^2$ and that the mass of dwarf galaxies enclosed within a sphere of fixed radius $r_{u}=300\, {\rm pc}$ has the same value $M_{300}=1.93\times 10^{7}\, M_{\odot}$, in remarkable agreement with the observations., Comment: arXiv admin note: substantial text overlap with arXiv:1504.08355

We consider a resonant SIMP dark matter in models with two singlet complex scalar fields charged under a local dark $U(1)_D$. After the $U(1)_D$ is broken down to a $Z_5$ discrete subgroup, the lighter scalar field becomes a SIMP dark matter which has the enhanced $3\rightarrow 2$ annihilation cross section near the resonance of the heavier scalar field. Bounds on the SIMP self-scattering cross section and the relic density can be fulfilled at the same time for perturbative couplings of SIMP. A small gauge kinetic mixing between the SM hypercharge and dark gauge bosons can be used to make SIMP dark matter in kinetic equilibrium with the SM during freeze-out., Comment: 14 pages, 5 figures, Improved discussion on thermal-averaged annihilation cross section

We update the constraint on the dark matter annihilation cross section by using the recent measurements of the CMB anisotropy by the Planck satellite. We fully calculate the cascade of dark matter annihilation products and their effects on ionization, heating and excitation of the hydrogen, hence do not rely on any assumption on the energy fractions that cause these effects., Comment: 9 pages, 1 figure; to appear in Phys.Lett.B

With the Markov Chain Monte Carlo (MCMC) method, we constrain an interactive dark energy model by combing the up-to-date observational data of Hubble parameter H(z) with the 7-year baryon acoustic oscillation (BAO) data, and the cosmic microwave background (CMB) data observed by the Planck satellite. Under the joint constraint of the three kinds of data, the best-fit values of the model parameters and their 1-σ errors are obtained as follows: the energy density Ω m = 0.266 - 0.028 + 0.028 ( 1 σ ) , the interaction factor γ = 0.090 - 0.098 + 0.100 ( 1 σ ) , the parameter of state equation of dark matter w X = - 1.307 - 0.269 + 0.263 ( 1 σ ) , and the Hubble Constant H 0 = 7420 - 4.56 + 4.66 ( 1 σ ) , where the coupling parameter γ > 0 means that the energy is transferred from dark matter to dark energy, and the coincidence problem in the Lambda-Cold Dark Matter (ΛCDM) model is slightly alleviated in the 1σ range. For comparisons, we constrain the same model with the BAO+CMB observations and H(z) data separately. The results are as follows: (1) The H(z) data could put stricter constraint on the parameter γ than the BAO+CMB observations. (2) The ΛCDM model is best fitted, and the coupling parameter γ is correlated with parameters Ωm and H0. (3) The inconsistency of the constraint results of H0 between the local distance ladder measurements and the Planck observations can be alleviated after taking account of the interaction between dark energy and dark matter.

We present an update of the CLUMPY code for the calculation of the astrophysical J -factors (from dark matter annihilation/decay) for any Galactic or extragalactic dark matter halo including substructures: halo-to-halo concentration scatter may now be enabled, boost factors can include several levels of substructures, and triaxiality is a new option for dark matter haloes. This new version takes advantage of the cfitsio and HEALPix libraries to propose fits output maps using the HEALPix pixelisation scheme. Skymaps for γ -ray and ν signals from generic annihilation/decay spectra are now direct outputs of CLUMPY . Making use of HEALPix routines, smoothing by a user-defined instrumental Gaussian beam and computing the angular power spectrum of the maps are now possible. In addition to these improvements, the main novelty is the implementation of a Jeans analysis module, to obtain dark matter density profiles from kinematic data in relaxed spherical systems (e.g., dwarf spheroidal galaxies). The code is also interfaced with the GreAT toolkit designed for Markov Chain Monte Carlo analyses, from which probability density functions and credible intervals can be obtained for velocity dispersions, dark matter profiles, and J -factors. Program summary Program title: CLUMPY Catalogue identifier: AEKS_v2_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEKS_v2_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 494335 No. of bytes in distributed program, including test data, etc.: 24425968 Distribution format: tar.gz Programming language: C/C++. Computer: PC and Mac. Operating system: UNIX(Linux), MacOS X. RAM: Between 500MB and 1GB depending on the size of the requested skymap Catalogue identifier of previous version: AEKS_v1_0 Journal reference of previous version: Comput. Phys. Comm. 183(2012)656 Classification: 1.1, 1.7, 1.9. External routines: CERN ROOT ( http://root.cern.ch ), GSL ( http://www.gnu.org/software/gsl ), cfitsio ( http://heasarc.gsfc.nasa.gov/fitsio/fitsio.html ), HEALPix C++ and F90 ( http://healpix.sourceforge.net/index.php ), GreAT ( http://lpsc.in2p3.fr/great ) (for MCMC analyses only), and Doxygen ( http://www.doxygen.org ) (optional) Does the new version supersede the previous version?: Yes Nature of problem: Calculation of dark matter profile from kinematic data, γ -ray and ν signals from dark matter annihilation/decay. Solution method: Solve the integro-differential Jeans equation (optimised for speed) for several generic distributions (dark matter profile, light profile, velocity anisotropy). Integration of the DM density (squared) along a line-of-sight for generic dark matter haloes with substructures (spatial, mass, concentration distributions). Draw full skymaps of γ -ray and ν emission from dark matter structures, smoothed by an instrument PSF using HEALPix tools. Reasons for new version: Many more functionalities and options have been added to the code. Summary of revisions: Inclusion of the PPPC4DMID spectra for gamma-ray and neutrino fluxes; HEALPix pixelisation for skymaps and angular power spectrum; DM profile triaxiality enabled; More mass–concentration options; Multi-level substructure boost; Jeans analysis module to compute dark matter profiles for stellar kinematic data; Improved ROOT and FITS output. Restrictions: The diffuse extragalactic contribution to the signal (and γ -ray attenuation) as well as secondary radiation from dark matter remains to be included in order to provide a comprehensive description of the expected signal. Running time: This is highly dependent of the user-defined choices of DM profiles, precision e and integration angle α int : • ∼ 1 hour for a full skymap (including substructures) with α int = 0.1 ° and e = 0.01 ; • ∼ = 1 mn for a 5 ° × 5 ° skymap (including substructures) with α int = 0.1 ° and e = 0.01 ; • ∼ 5 mn for a typical Jeans/MCMC analysis (on a ‘ultrafaint’-like dwarf spheroidal galaxy) using a constant anisotropy profile.

We propose to investigate a secluded WIMP dark matter model consisting of neutral fermions as the dark matter candidate and a Proca-Wentzel (PW) field as a mediator. In the model that we consider here, dark matter WIMPs interact with standard model (SM) particles only through the PW field of ~ MeV -- multi-GeV mass particles. The interactions occur via an U(1)' mediator, V_{\mu}', which couples to the SM by kinetic mixing with U(1) hypercharge bosons, B_{\mu}. One important difference between our model and other such models in the literature is the absence of an extra singlet scalar, so that the parameter with dimension of mass M^2_V is not related to a spontaneous symmetry breaking. This QED based model is also renormalizable. The mass scale of the mediator and the absence of the singlet scalar can lead to interesting astrophysical signatures. The dominant annihilation channels are different from those usually considered in previous work. We show that the GeV-energy gamma-ray excess in the galactic center region, as derived from Fermi-LAT Gamma-ray Space Telescope data, can be attributed to such secluded dark matter WIMPs, given parameters of the model that are consistent with the cosmological dark matter density. Secluded WIMP models are also consistent with suggested upper limits on the DM contribution to the cosmic-ray antiproton flux., Comment: Version accepted for publication in Astroparticle Physics. 28 pages, 7 figures

The cosmic star formation rate (CSFR) represents the fraction of gas that is converted into stars within a certain comoving volume and at a given time t . However the evolution of the dark matter haloes and its relationship with the CSFR is not yet clear. In this context, we have investigated the role of the dark halo mass function - DHMF - in the process of gas conversion into stars. We observed a strong dependence between the fraction of baryons in structures, f b , and the specific mass function used for describing the dark matter haloes. In some cases, we have obtained f b greater than one at redshift z = 0 . This result indicates that the evolution of dark matter, described by the specific DHMF, could not trace the baryonic matter without a bias parameter. We also observed that the characteristic time-scale for star formation, τ , is strongly dependent on the considered DHMF, when the model is confronted against the observational data. Also, as part of this work it was released, under GNU general public license, a Python package called ‘pycosmicstar’ to study the CSFR and its relationship with the DHMF.

The accelerated expansion of the Universe, described by the term Dark Energy, is one of the most important open questions in Cosmology today. This mysterious Dark Energy comprises about 70 % of the Universe and all the available data to date favors the notion that it is a Cosmological Constant. We will review the current status of the experimental data on Dark Energy and provide a short description of the upcoming experiments poised to shed light on this problem.

We review the present theoretical status of particle dark matter, concentrating on two of the most attractive dark matter candidates: sterile neutrinos and weakly interacting massive particles. We review the basic theoretical aspects of each of these two scenarios as well as their observational signatures, with emphasis on the possible signals recently reported by various authors.

We consider a simple generic dissipative dark matter model: a hidden sector featuring two dark matter particles charged under an unbroken $U(1)'$ interaction. Previous work has shown that such a model has the potential to explain dark matter phenomena on both large and small scales. In this framework, the dark matter halo in spiral galaxies features nontrivial dynamics, with the halo energy loss due to dissipative interactions balanced by a heat source. Ordinary supernovae can potentially supply this heat provided kinetic mixing interaction exists with strength $\epsilon \sim 10^{-9}$. This type of kinetically mixed dark matter can be probed in direct detection experiments. Importantly, this self-interacting dark matter can be captured within the Earth and shield a dark matter detector from the halo wind, giving rise to a diurnal modulation effect. We estimate the size of this effect for detectors located in the Southern hemisphere, and find that the modulation is large ($\gtrsim 10\%$) for a wide range of parameters., Comment: 12 pages, 4 figures, clarifying comments and references added

Although weakly interacting massive particle (WIMP) scenario is very well motivated, it is not guaranteed to be the truth. It is important to keep mind open and consider other well-motivated scenarios. In this paper, we briefly review several possible non-WIMP dark matter (DM) candidates. First, we discuss details on asymmetric DM models, in which the baryon asymmetry in standard model sector is related to the asymmetry in DM sector. We discuss how DM relic abundance is determined in such models. Also we cover the possible interesting experimental signatures induced by its asymmetric nature. Then we consider ultralight DM candidates, i.e., axion and dark photon. In such scenarios, DM should be treated as a coherently oscillating background, instead of each individual particle. Searching strategies for such DM candidates is very different than those in conventional DM models. We discuss several interesting experiments looking for these ultralight particles. We also cover interesting subtleties encountered in those experiments.

We study CMB constraints on a model with a cosmological constant and a fraction of dark matter non-minimally coupled to a massless scalar field. In this scenario, there is an extra gravity-like fifth force which can affect the evolution of the Universe enough to have a discernible effect on measurements of cosmological parameters. Using Planck and WMAP polarisation data, we find that up to half of the dark matter can be coupled. The coupling can also be several times larger than in models with a single species of cold dark matter coupled to a quintessence scalar field, as the scalar field does not play the role of dark energy and is therefore less constrained by the data., Comment: 5 pages, 4 figures

We briefly review the halo-independent formalism, that allows to compare data from different direct dark matter detection experiments without making assumptions on the properties of the dark matter halo. We apply this method to spin-independent WIMP-nuclei interactions, for both isospin-conserving and isospin-violating couplings, updating the existing analyses with the addition of the SuperCDMS bound. We point out that this method can be applied to any type of WIMP interaction., 10 pages, 3 figures. To appear in the TAUP 2013 Proceedings

Low mass dark matter theories, if produced as a thermal relic in the early universe, must be accompanied by light mediators in order to obtain the dark matter abundance observed in the present day universe. These light mediators in turn provide a channel for the production of dark matter at fixed target neutrino experiments, producing a relativistic dark matter beam, which could then be detected by neutral-current-like interactions in neutrino detectors. We consider the possibility that fixed target neutrino experiments such as MiniBooNE and T2K could serve as a new dark matter search avenue, sensitive to sub-GeV dark matter scenarios that would be otherwise undetectable. These experiments are found to provide sensitivity to light stable states that could serve as viable candidates for particle dark matter.

In this paper, we have considered the closed FRW universe filled with two interacting fluids; dark matter and holographic dark energy components. Under certain conditions, this dark energy model is characterised by a big rip type future singularity and therefore a finite life time of the universe (Cruz et al., 2008). As the universe passes through a significant time when the matter and the dark energy densities are roughly comparable between the matter and the dark energy dominated era. So, we calculated the fraction of total life time of the universe when the universe passes through the coincidental stage for this future singularity by considering 1 r o r = ρ M ρ DE r o , where r 0 is any fixed ratio. It has been found that the time for the future singularity t s is very large when the value of the constant c is much closed to zero and the fraction is smaller for smaller values of r 0 . Comparison of the results with the observational data and its importance has also been discussed.

We investigate the scenario that one flat direction creates baryon asymmetry of the unverse, while Q balls from another direction can be the dark matter in the gauge-mediated supersymmetry breaking for high-scale inflation. Isocurvature fluctuations are suppressed by the fact that the Affleck-Dine field stays at around the Planck scale during inflation. We find that the dark matter Q balls can be detected in IceCube-like experiments in the future., Comment: 9 pages, 3 figures, published version

We suggest a minimal extension of the standard model, which can explain current experimental data of the dark matter, small neutrino masses and baryon asymmetry of the universe, inflation, and dark energy, and achieve gauge coupling unification. The gauge coupling unification can explain the charge quantization, and be realized by introducing six new fields. We investigate the vacuum stability, coupling perturbativity, and correct dark matter abundance in this model by use of current experimental data., 17 pages, 8 figures

We study late-time cosmic accelerating dynamics from Born–Infeld- f ( R ) gravity in a simplified conformal approach. We find that a variety of cosmic effects such as Little Rip, ΛCDM universe and dark energy cosmology with finite-time future singularities may occur. Unlike the convenient Born–Infeld gravity where in the absence of matter only de Sitter expansion may emerge, apparently any FRW cosmology maybe reconstructed from this conformal version of the Born–Infeld- f ( R ) theory. Despite the fact that the explicit form of f ( R ) is fixed by the conformal ansatz, the relation between the two metrics in this approach may be changed so as to bring out any desired FRW cosmology.

The existence of the dark matter with amount about five times the ordinary matter is now well established experimentally. There are now many candidates for this dark matter. However, dark matter could be just like the ordinary matter in a parallel universe. If both universes are described by a non-abelian gauge symmetries, then there will be no kinetic mixing between the ordinary photon and the dark photon, and the dark proton, dark electron and the corresponding dark nuclei, belonging to the parallel universe, will be stable. If the strong coupling constant, $(\alpha_s)_{dark}$ in the parallel universe is five times that of $\alpha_s$, then the dark proton will be about five time heavier, explaining why the dark matter is five times the ordinary matter. However, the two sectors will still interact via the Higgs boson of the two sectors. This will lead to the existence of a second light Higss boson, just like the Standard Model Higgs boson. This gives rise to the invisible decay modes of the Higgs boson which can be tested at the LHC, and the proposed ILC., Comment: 15 pages, 4 figures

We investigate the phase-space structure of the quintom dark energy paradigm in the framework of spatially flat and homogeneous universe. Considering arbitrary decoupled potentials, we find certain general conditions under which the phantom dominated solution is late time attractor, generalizing previous results found for the case of exponential potential. Center Manifold Theory is employed to obtain sufficient conditions for the instability of de Sitter solution either with phantom or quintessence potential dominance., 10 pages, 5 figures. References and a new section added. Minor typos corrected. The current institution of one of the authors has been updated

We propose and study a scalar extension of the Standard Model which respects a Z3 symmetry remnant of the spontaneous breaking of a global U(1)DM symmetry. The model has a dark matter candidate whose relic density is determined by three classes of processes: the usual self-annihilation, semi-annihilation and purely dark matter 3→2 processes. The latter has been subject of recent interest leading to the so-called 'Strongly Interacting Massive Particle' (SIMP) scenario. We show under which conditions the model can lead to a concrete realization of such scenario and study the possibility that the dark matter self-interactions could address the small scale structure problems. In particular, we find that in order for the SIMP scenario to work, the dark matter mass must be in the range of 100 MeV, with the global symmetry energy breaking scale in the TeV range.

By extending the SM with two scalar singlets, a vector-like fermion doublet and a fermion singlet, all odd under a Z 2 symmetry, it is possible to explain the correct dark matter relic density and also fulfill the main constraints for neutrino physics. In this work, we only consider the case of fermionic dark matter. We study the parameter space, first of all taking into account the relic density constraint, which gives us a set of parameters that can be used as inputs for the Casas-Ibarra parametrization in order to get the remaining parameters that also match neutrino physics. We also analyze possible constraints from lepton flavor violation processes such as μ → e γ .

It is shown that heavy sterile neutrinos can be a consequence of a new broken U(1)X symmetry. This sterile symmetry is further speculated to be related to the conservation of the dark number associated with Dark Matter particles, corresponding to a dark neutrino mass m N D ⩾ 1 keV with a high scale ⩾ ∼ 10 2 GeV dark symmetry U(1)D breaking.

We discuss a model of non perturbative decay of dark energy into hot and cold dark matter. This model provides a mechanism from the field theory to realize the energy transfer from dark energy into dark matter, which is the requirement to alleviate the coincidence problem. The advantage of the model is the fact that we accommodate a mean life compatible with the age of the universe. We also argue that supersymmetry is a natural set up, though not essential., Comment: 5 pages to be published in Physics Letters B

Since it can describe the rotation curves of galaxies without dark matter and can give rise to accelerated expansion, conformal gravity attracts much attention recently. As a theory of modified gravity, it is important to test conformal gravity with astrophysical observations. Here we constrain conformal gravity with SNIa and Hubble parameter data and investigate whether it suffers from an age problem with the age of APM~08279+5255. We find conformal gravity can accommodate the age of APM~08279+5255 at 3 $\sigma$ deviation, unlike most of dark energy models which suffer from an age problem., Comment: 6 pages, 2 figures

Instead of fluid type dark matter (DM), axion-like scalar fields with a periodic self-interaction or some truncations of it are analyzed as a model of galaxy halos. It is probed if such cold Bose–Einstein type condensates could provide a viable soliton type interpretation of the DM ‘bullets’ observed by means of gravitational lensing in merging galaxy clusters. We study solitary waves for two self-interacting potentials in the relativistic Klein–Gordon equation, mainly in lower dimensions, and visualize the approximately shape-invariant collisions of two ‘lump’ type solitons.

Although Planck data supports the standard \Lambda CDM model, it still allows for the presence of Dark Radiation corresponding up to about half an extra standard neutrino species. We propose a scenario for obtaining a fractional "effective neutrino species" from a thermally produced particle which decays into a much lighter stable relic plus standard fermions. At lifetimes much longer than 1 sec, both the relic particles and the non-thermal neutrino component contribute to Dark Radiation. By increasing the stable-to-unstable particle mass ratio, the relic particle no longer acts as Dark Radiation but instead becomes a candidate for Warm Dark Matter with mass O(1keV - 100GeV). In both cases it is possible to address the lithium problem., Comment: 18 pages, 2 figures; v3 matches version to be published in PLB

We attempt to estimate the uncertainty in the constraints on the spin independent dark matter-nucleon cross section due to our lack of knowledge of the dark matter phase space in the galaxy. We fit the density of dark matter before investigating the possible solutions of the Jeans equation compatible with those fits in order to understand what velocity dispersions we might expect at the solar radius. We take into account the possibility of non-Maxwellian velocity distributions and the possible presence of a dark disk. Combining all these effects, we still find that the uncertainty in the interpretation of direct detection experiments for high (>100 GeV) mass dark matter candidates is less than an order of magnitude in cross section., 18 pages, 17 figures

We review in this talk the limits on the dark matter properties which stem from indirect dark matter searches with neutrinos. Concretely we review the limits on the dark matter self-annihilation cross section, the scattering cross section with protons and the lifetime.