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We perform a dynamical system analysis of a cosmological model with linear dependence between the vacuum density and the Hubble parameter, with constant-rate creation of dark matter. We show that the de Sitter spacetime is an asymptotically stable critical point, future limit of any expanding solution. Our analysis also shows that the Minkowski spacetime is an unstable critical point, which eventually collapses to a singularity. In this way, such a prescription for the vacuum decay not only predicts the correct future de Sitter limit, but also forbids the existence of a stable Minkowski universe. We also study the effect of matter creation on the growth of structures and their peculiar velocities, showing that it is inside the current errors of redshift space distortions observations. [ABSTRACT FROM AUTHOR]

The concordance particle creation model - a class of A(t) Cold Dark Matter (CDM) cosmologies - is studied using large-scale structure (LSS) formation, with particular attention to the integrated Sachs-Wolfe effect. The evolution of the gravitational potential and the amplitude of the cross-correlation of the cosmic microwave background (CMB) signal with LSS surveys are calculated in detail. We properly include in our analysis the peculiarities involving the baryonic dynamics of the A(t)CDM model which were not included in previous works. Although both the A(t)CDM and the standard cosmology are in agreement with available data for the CMB-LSS correlation, the former presents a slightly higher signal which can be identified with future data. [ABSTRACT FROM AUTHOR]

We study non-linear structure formation in an interacting model of the dark sector of the Universe in which the dark energy density decays linearly with the Hubble parameter, ρΛ ∝ H, leading to a constant-rate creation of cold dark matter. We derive all relevant expressions to calculate the mass function and the cluster number density using the Sheth–Torman formalism and show that the effect of the interaction process is to increase the number of bound structures of large masses (M ≳ 1014 M⊙ h−1) when compared to the standard Λ cold dark matter model. Since these models are not reducible to each other, this number counts signature can in principle be tested in future surveys. [ABSTRACT FROM PUBLISHER]

Abstract: The split of a generalised Chaplygin gas with an equation of state into an interacting mixture of pressureless matter and a dark-energy component with equation of state implies the existence of non-adiabatic pressure perturbations. We demonstrate that the square of the effective (non-adiabatic) sound speed of the medium is proportional to the ratio of the perturbations of the dark energy to those of the dark matter. Since, as demonstrated explicitly for the particular case , dark-energy perturbations are negligible compared with dark-matter perturbations on scales that are relevant for structure formation, we find . Consequently, there are no oscillations or instabilities which have plagued previous adiabatic Chaplygin-gas models. [Copyright &y& Elsevier]

In previous papers, a cosmological model with constant rate particle creation and vacuum term decaying linearly with the Hubble parameter was shown to lead to a good concordance when tested against precise observations: the position of the first peak in the spectrum of anisotropies of the cosmic microwave background (CMB), the Hubble diagram for Type Ia supernovae (SNe Ia), the distribution of large-scale structures and the distance to the baryonic acoustic oscillations (BAO). That model has the same number of parameters as the spatially flat standard model and seems to alleviate some observational/theoretical tensions appearing in the latter. In this paper, we complement those tests with 109 gamma-ray bursts (GRBs), 59 of them with redshifts above z = 1.4, which permits to extend the Hubble diagram to redshifts up to z ≈ 8. For the calibration of the 50 GRBs with z < 1.4, we use the 288 supernovae of the Sloan Digital Sky Survey project, calibrated with the MLCS2k2 fitter, less model-dependent than other samples like Union2. Our results show a good concordance with the previous tests and, again, less tensions between SNe Ia and GRB best fits as compared to the standard model. [ABSTRACT FROM AUTHOR]

In a recent paper we have shown that a minimally coupled, self-interacting scalar field of mass m can form black holes of mass M = 3 / (4 m) (in Planck units). If dark matter is composed by axions, they can form miniclusters that for QCD axions have masses below this value. In this work it is shown that for a scenario in which the axion mass depends on the temperature as m ∝ T - 6 , minicluster masses above 0.32 M ⊙ , corresponding to an axion mass of 3 × 10 - 10 eV, exceed M and can collapse into black holes. If a fraction of these black holes is in binary systems, gravitational waves emitted during the inspiral phase could be detected by advanced interferometers like LIGO or VIRGO and by the planned Einstein Telescope. For a detection rate of one event per year, the lower limits on the binary fraction are 10 - 4 and 10 - 6 for LIGO and Einstein Telescope respectively. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate that creation of dark-matter particles at a constant rate implies the existence of a cosmological term that decays linearly with the Hubble rate. We discuss the cosmological model that arises in this context and test it against observations of the first acoustic peak in the cosmic microwave background (CMB) anisotropy spectrum, the Hubble diagram for supernovas of type Ia (SNIa), the distance scale of baryonic acoustic oscillations (BAO) and the distribution of large scale structures (LSS). We show that a good concordance is obtained, albeit with a higher value of the present matter abundance than in the ΛCDM model. We also comment on general features of the CMB anisotropy spectrum and on the cosmic coincidence problem. [Copyright &y& Elsevier]