arXiv subjects

Sergey Pavluchenko

Publications and source records attributed to Sergey Pavluchenko.

8 recordsLinked to original sources

arXiv2026

On the Properties of the Power-Law Cosmological Solutions in Lovelock Gravity

In this paper we study the properties of Kasner cosmological solutions in Lovelock gravity. Recent progress in the investigation of flat cosmological models in Lovelock gravity unveiled the fact that in quadratic (Gauss--Bonnet) and cubic Lovelock gravities, the higher-order power-law solutions could play the role of both future and past asymptotes, and under some conditions, there could exist a smooth transition between them. So it is natural to question if this feature is unique to Gauss--Bonnet and cubic Lovelock gravities, or if it is a general feature of Lovelock gravity. Our analysis suggests that starting from quartic and in all higher-order Lovelock gravities, the high-order Kasner solution cannot play the role of a past asymptote, not only preventing the abovementioned transition from happening, but also potentially hindering the possibility of reaching viable compactification.

gr-qc↗

arXiv2024

Cosmological Models in Lovelock Gravity: An Overview of Recent Progress

In the current review, we provide a summary of the recent progress made in the cosmological aspect of extra-dimensional Lovelock gravity. Our review covers a wide variety of particular model/matter source combinations: Einstein--Gauss--Bonnet as well as cubic Lovelock gravities with vacuum, cosmological constant, perfect fluid, spatial curvature, and some of their combinations. Our analysis suggests that it is possible to set constraints on the parameters of the above-mentioned models from the simple requirement of the existence of a smooth transition from the initial singularity to a realistic low-energy regime. Initially, anisotropic space naturally evolves into a configuration with two isotropic subspaces, and if one of these subspaces is three-dimensional and is expanding while another is contracting, we call it realistic compactification. Of course, the process is not devoid of obstacles, and in our paper, we review the results of the compactification occurrence investigation for the above-mentioned models. In particular, for vacuum and $\Lambda$-term EGB models, compactification is not suppressed (but is not the only possible outcome either) if the number of extra dimensions is $D \geqslant 2$; for vacuum cubic Lovelock gravities it is always present (however, cubic Lovelock gravity is defined only for $D \geqslant 3$ number of extra dimensions); for the EGB model with perfect fluid it is present for $D=2$ (we have not considered this model in higher dimensions yet), and in the presence of spatial curvature, the realistic stabilization of extra dimensions is always present (however, such a model is well-defined only in $D \geqslant 4$ number of extra dimensions).

gr-qc↗

arXiv2018

On the Stability of Dark Energy Scalar Field Reconstruction from SNe Ia Data

The current paper addresses the possibility of Dark Energy scalar field potential reconstruction from SNe Ia data and the problems arising during the process. We describe the method and test its limits and features with use of synthetic data, as well as discuss several issues connected to error propagation. We conclude that the chosen smoothing method -- binning of the data -- introduces immense uncertainty amplification which limits the practical application of this method, leaving us with other alternatives. We also address the ``instability of the reconstruction'', an important effect when a false scalar field -- real or phantom -- could be reconstructed if the $\Omega_m$ and $H_0$ parameters are wrongly estimated; a similar effect could be expected in other Dark Energy models as well.

astro-ph.CO↗

arXiv2018

Limits on the Reconstruction of a Single Dark Energy Scalar Field Potential from SNe Ia Data

In this paper we perform a reconstruction of the scalar field potential responsible for cosmic acceleration using SNe Ia data. After describing the method, we test it with real SNe Ia data-Union2.1 and JLA SNe datasets. We demonstrate that with the current data precision level, the full reconstruction is not possible. We discuss the problems which arise during the reconstruction process and the ways to overcome them.

astro-ph.CO↗

arXiv2018

Realistic Compactification Models in Einstein-Gauss-Bonnet Gravity

We report the results of a study on the dynamical compactification of spatially flat cosmological models in Einstein-Gauss-Bonnet gravity. The analysis was performed in the arbitrary dimension in order to be more general. We consider both vacuum and $Λ$-term cases. Our results suggest that for vacuum case, realistic compactification into the Kasner (power law) regime occurs with any number of dimensions ($D$), while the compactification into the exponential solution occurs only for $D \geqslant 2$. For the $Λ$-term case only compactification into the exponential solution exists, and it only occurs for $D \geqslant 2$ as well. Our results, combined with the bounds on Gauss-Bonnet coupling and the $Λ$-term ($α, Λ$, respectively) from other considerations, allow for the tightening of the existing constraints and forbid $α< 0$.

hep-th↗

arXiv2015

Non-constant volume exponential solutions in higher-dimensional Lovelock cosmologies

In this paper we propose a scheme which allows one to find all possible exponential solutions of special class -- non-constant volume solutions -- in Lovelock gravity in arbitrary number of dimensions and with arbitrate combinations of Lovelock terms. We apply this scheme to (6+1)- and (7+1)-dimensional flat anisotropic cosmologies in Einstein-Gauss-Bonnet and third-order Lovelock gravity to demonstrate how our scheme does work. In course of this demonstration we derive all possible solutions in (6+1) and (7+1) dimensions and compare solutions and their abundance between cases with different Lovelock terms present. As a special but more "physical" case we consider spaces which allow three-dimensional isotropic subspace for they could be viewed as examples of compactification schemes. Our results suggest that the same solution with three-dimensional isotropic subspace is more "probable" to occur in the model with most possible Lovelock terms taken into account, which could be used as kind of anthropic argument for consideration of Lovelock and other higher-order gravity models in multidimensional cosmologies.

gr-qc↗

arXiv2014

Exact exponential solutions in Einstein-Gauss-Bonnet flat anisotropic cosmology

In this paper we are looking for the exponential solutions (i.e. the solutions with the scale factors change exponentially over time) in the Einstein-Gauss-Bonnet gravity. We argue that we found all possible non-constant-volume solutions (up to permutations) in lower dimensions ((4+1) and (5+1)) and developed a scheme which allows one to find necessary conditions in arbitrary dimension.

gr-qc↗

arXiv2003

Generality of inflation in closed FRW models

We investigate the generality of inflation in closed FRW models for a wide class of quintessence potentials. It is shown that inflation is not suppressed for most of them for a wide class of their parameters. This allows us to decide if inflation is common even in case of a closed universe.

astro-ph↗