Related papers: A Comparison of the LVDP and {\Lambda}CDM Cosmolog…
The present work deals with kinematical models of latetime cosmology. It is based on purely phenomenological assumption about the deceleration parameter. The models are confronted to observational data sets of type Ia supernovae distance…
Present-day extragalactic observations are mostly rather well-modelled by a general-relativistic model, the $\Lambda$ CDM model. The model appears to surpass the limits of known physics by requiring that the Universe be dominated by "dark…
We investigate observational constraints on the running vacuum model (RVM) of $\Lambda=3\nu (H^{2}+K/a^2)+c_0$ in the spatially curved universe, where $\nu$ is the model parameter, $K$ corresponds to the spatial curvature constant, and…
We show that a cosmology driven by gravitationally induced particle production of all non-relativistic species existing in the present Universe mimics exactly the observed flat accelerating $\Lambda$CDM cosmology with just one dynamical…
We study dynamics of $\Lambda(t)$ cosmological models which are a natural generalization of the standard cosmological model (the $\Lambda$CDM model). We consider a class of models: the ones with a prescribed form of…
The status of the standard cosmological model, also known as "LCDM" is described. With some simple assumptions, this model fits a wide range of data, with just six (or seven) free parameters. One should be skeptical about this claim, since…
Recent cosmological observations show hints for possible deviations from the standard $\Lambda$CDM paradigm at late times. To study such deviation, we introduce a minimal phenomenological framework in which the total equation of state of…
This paper explores models of the FLRW universe that incorporate a time-varying cosmological term $\Lambda(t)$. Specifically, we assume a power-law form for the cosmological term as a function of the scale factor: $\Lambda(t)=\Lambda_{0}…
Despite the fact that a rigid $\Lambda$-term is a fundamental building block of the concordance $\Lambda$CDM model, we show that a large class of cosmological scenarios with dynamical vacuum energy density $\rho_{\Lambda}$ and/or…
We present a comparative analysis of current observational constraints on three recently discussed alternative models for explaining the low-redshift acceleration of the universe: the so-called steady-state torsion model, the generalized…
The present standard model of cosmology, $\Lambda$CDM, contains some intriguing coincidences. Not only are the dominant contributions to the energy density approximately of the same order at the present epoch, but we note that contrary to…
In this work, we have considered a model independent approach to study the nature of the late time cosmic acceleration. We have used the Pade approximation to parametrize the comoving distance. Consequently, from this comoving distance, we…
The homogeneous, isotropic, and flat $\Lambda$CDM universe favored by observations of the cosmic microwave background can be described using only Euclidean geometry, locally correct Newtonian mechanics, and the basic postulates of special…
We develop a novel analytical dynamical analysis to derive precise energy density ratio evolutions for the $\phi$CDM and $poly\Lambda$CDM models, comparing them to the standard $\Lambda$CDM model and validating against numerical solutions.…
We study the cosmological predictions of two recently proposed non-local modifications of General Relativity. Both models have the same number of parameters as $\Lambda$CDM, with a mass parameter $m$ replacing the cosmological constant. We…
The current cosmological paradigm, $\Lambda$CDM, is characterized its expansive description of the history of the Universe, its deep connections to particle physics and the large amounts of data that support it. Nonetheless, $\Lambda$CDM's…
We study the running vacuum model in which the vaccum energy density depends on square of Hubble parameter in comparison with the $\Lambda$CDM model. In this work, the Bayesian inference method is employed to test against the standard…
We address the question of the uniqueness of spatially flat $\Lambda$CDM-like evolution for FLRW cosmologies in General Relativity, i.e. whether any model other than the spatially flat $\Lambda$CDM can give rise to the same type of scale…
In this work, we carry out a comprehensive perturbative analysis of four cosmological models featuring a sign-switching cosmological constant. Among these, we include the well-known $\Lambda_{\rm s}$CDM model, characterised by an abrupt…
This thesis investigates late-time cosmic acceleration using modified gravity theories with a focus on $f(Q)$ gravity, as an alternative to the $\Lambda$CDM model. The standard cosmological model attributes the acceleration to a…