相关论文: When Did Cosmic Acceleration Start ?
We describe a method to derive the expansion and acceleration rates directly from the data, without the need for the specification of a theory of gravity, and without adopting an a priori parameterization of the form or redshift evolution…
We explore the late time cosmological dynamics of the Universe within the framework of $f(Q,\mathcal{L}_{m})$ gravity by considering the specific form $f(Q, \mathcal{L}_m)=-Q+2\mathcal{L}_m+\gamma$. To describe the cosmic pressure…
We use the recent type Ia supernova, cosmic microwave background and large-scale structure data to shed light on the temporal evolution of the dark energy equation of state $w(z)$ out to redshift one. We constrain the most flexible…
The possible slowing down of cosmic acceleration was widely studied. However, the imposition of dark energy parametrization brought some tensions. In our recent paper, we test this possibility using a model-independent method, Gaussian…
We investigate the dynamical properties of dark energy through a detailed analysis of its equation of state parameter $w(z)$ as a function of redshift. We derive a general expression for $w(z)$ from the Friedmann-Lema\^itre-Robertson-Walker…
We use the Allen et al. (2008) galaxy cluster gas mass fraction versus redshift data to constrain parameters of three different dark energy models: a cosmological constant dominated one ($\Lambda$CDM); the XCDM parameterization of dark…
Associated with the cosmic acceleration are the old and new cosmological constant problems, recently put into the more general context of the dark energy problem. In broad terms, the old problem is related to an unexpected order of…
The influence of a dark component on the first epoch of galaxy formation is analysed by using the ages of the three oldest high-redshift galaxies known in the literature. Our results, based on a spatially flat accelerated Universe driven by…
Below scales of about 100/h Mpc our universe displays a complex inhomogeneous structure dominated by voids, with clusters of galaxies in sheets and filaments. The coincidence that cosmic expansion appears to start accelerating at the epoch…
The current expansion of the Universe has been observed to be accelerating, and the widely accepted spatially-flat concordance model of general relativistic cosmology attributes this phenomenon to a constant dark energy, a cosmological…
The cosmological model best capable of fitting current observational data features two separate epochs during which the Universe is accelerating. During the earliest stages of the Universe, such acceleration is known as cosmological…
In the present paper, it is found that dark energy emerges spontaneously from the modified gravity. According to cosmological scenario, obtained here, the universe inflates for $\sim 10^{-37}$ sec. in the beginning and late universe…
The energy conditions provide a very promising model-independent study of the current acceleration of the universe. However, in order to connect these conditions with observations, one often needs first to integrate them, and then find the…
We review the ability of redshift surveys to provide constraints on the Dark Energy content of the Universe. The matter power spectrum and dynamics at the present epoch are nearly `blind' to Dark Energy, but combined with the CMB they can…
We focus on uncertainties in supernova measurements, in particular of individual magnitudes and redshifts, to review to what extent supernovae measurements of the expansion history of the universe are likely to allow us to constrain a…
The dynamical age of the universe depends upon the rate of the expansion of the universe, which explicitly involves the dark energy equation of state parameter $w(z)$. Consequently, the evolution of $w(z)$ has a direct imprint on the age of…
In the standard cosmological paradigm cosmic acceleration is to only be a very recent (viz. $z \leq 1$) phenomenon, with the universe being required to be decelerating at all higher redshifts. We suggest that this particular expectation of…
We use lookback time versus redshift data from galaxy clusters (Capozziello et al., 2004) and passively evolving galaxies (Simon et al., 2005), and apply a bayesian prior on the total age of the Universe based on WMAP measurements, to…
In order to explain the current acceleration of the Universe, the fine tuning problem of the cosmological constant $\Lambda$ and the cosmic coincidence problem, different alternative models have been proposed in the literature. We use the…
A new cosmic scenario with gravitationally induced particle creation is proposed. In this model the Universe evolves from an early to a late time de Sitter era, with the recent accelerating phase driven only by the negative creation…