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Abstract: The absence of guidance from fundamental physics about the mechanism behind cosmic acceleration has given rise to a number of alternative cosmological scenarios. These are based either on modifications of general relativistic gravitation theory on large scales or on the existence of new fields in Nature. In this Letter we investigate the observational viability of some accelerating cosmological models in light of 32 age measurements of passively evolving galaxies as a function of redshift and recent estimates of the product of the cosmic microwave background acoustic scale and the baryonic acoustic oscillation peak scale. By using information-criteria model selection, we select the best-fit models and rank the alternative scenarios. We show that some of these models may provide a better fit to the data than does the current standard cosmological constant dominated (ΛCDM) model. [Copyright &y& Elsevier]

Abstract: The cosmographic expansion history of the universe is investigated by using the 557 type Ia supernovae from the Union2 Compilation set along with the current estimates involving the product of the CMB acoustic scale ℓ A and the BAO peak at two different redshifts. Using a well-behaved parameterization for the deceleration parameter, q(z)= q 0 + q 1 z/(1+ z), we estimate the accelerating redshift z acc =−q 0/(q 0 + q 1) (at which the universe switches from deceleration to acceleration) and investigate the influence of a non-vanishing spatial curvature on these estimates. We also use the asymptotic value of q(z) at high-z to place more restrictive bounds on the model parameters q 0 and q 1, which results in a more precise determination of the epoch of cosmic acceleration. [Copyright &y& Elsevier]

Extending previous results, we explore aspects of the reheating mechanism for non-minimal Higgs inflation in the strong coupling regime. We constrain the radiative corrections for the inflaton's potential by considering the Coleman-Weinberg approximation and use the Renormalization Group Equations for the Higgs field to derive an upper limit on the top quark mass. Using the current Cosmic Microwave Background, Baryon Acoustic Oscillation, and Supernovae data, we obtain m t ≤ 170.44 GeV, confirming the observational compatibility of the model with recent m t estimates reported by the CMS collaboration. We also analyze the breakdown of the well-known correlation involving the Hubble constant H 0 and the clustering parameter σ 8 , which makes the model interesting in light of the cosmological tensions discussed over the last decade. [ABSTRACT FROM AUTHOR]

Abstract: We investigate cosmological consequences of a class of exponential gravity in the Palatini formalism. By using the current largest type Ia Supernova sample along with determinations of the cosmic expansion at intermediary and high-z we impose tight constraints on the model parameters. Differently from other models, we find solutions of transient acceleration, in which the large-scale modification of gravity will drive the Universe to a new decelerated era in the future. We also show that a viable cosmological history with the usual matter-dominated era followed by an accelerating phase is predicted for some intervals of model parameters. [Copyright &y& Elsevier]

Abstract: Motivated by the fact that any nonzero Λ can introduce a length scale or a time scale into Einsteinʼs theory, . Conversely, any cosmological length scale or time scale can introduce a , . In this Letter, we investigate the time varying corresponding to the length scales, including the Hubble horizon, the particle horizon and the future event horizon, and the time scales, including the age of the universe and the conformal time. It is found out that, in this scenario, the model can be taken as the unified origin of the holographic and agegraphic dark energy models with interaction between the matter and the dark energy, where the interacting term is determined by . We place observational constraints on the models originating from different cosmological length scales and time scales with the recently compiled “Union2 compilation” which consists of 557 Type Ia supernovae (SNIa) covering a redshift range . In conclusion, an accelerating expansion universe can be derived in the cases taking the Hubble horizon, the future event horizon, the age of the universe and the conformal time as the length scale or the time scale. [Copyright &y& Elsevier]

We report five measurements of the transverse baryonic acoustic scale, θ BAO , obtained from the angular two-point correlation function calculation for Luminous Red Galaxies of the eleventh data release of the Sloan Digital Sky Survey (SDSS). Each measurement has been obtained by considering a thin redshift shell (Δ z = 0.01 and 0.02) in the interval z ∈ [0.565, 0.660], which contains a large density of galaxies (~ 20, 000 galaxies/redshift shell). Differently from the three-dimensional Baryon Acoustic Oscillations (BAO) measurements, these data points are obtained almost model-independently and provide a Cosmic Microwave Background (CMB)-independent way to estimate the sound horizon r s. Assuming a time-dependent equation-of-state parameter for the dark energy, we also discuss constraints on the main cosmological parameters from θ BAO and CMB data. [ABSTRACT FROM AUTHOR]