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Sergey Chervon

Publications and source records attributed to Sergey Chervon.

6 recordsLinked to original sources
arXiv2025

A New Approach to the Analysis of Cosmological Parameters in Multifield Cosmology

Currently, a method has been developed for the cosmological inflation model with a single scalar field to calculate cosmological parameters such as the power spectrum of scalar and tensor perturbations, their spectral indices, and the tensor-to-scalar ratio. However, for a multifield configuration, a definitive method for calculating cosmological parameters has not yet been established. We propose a new effective algorithm for determining cosmological parameters within the tensor-multi-scalar theory of gravity, which describes the early inflationary epoch of the Universe. Our approach is based on utilizing a specific analytical solution within a multifield cosmological model to establish functional relationships between fields. This method enables the computation of cosmological parameters and their comparison with observational data.

gr-qc↗
arXiv2024

Cosmological solutions of a chiral self-gravitating model of $f(R,(\nabla R)^2,\square R)$ gravity

We study modified $f(R,(\nabla R)^2,\square R)$ gravity and show in detail how it can be reduced to Einstein gravity with a few scalar fields and then represented in the form of chiral self-gravitating model of the special type. In further investigation of the model we focus on cosmology and looking for solutions of the dynamic equations of chiral fields and the Einstein-Friedman equations in the Friedman-Robertson-Walker spacetime. Exact solutions of the considered model for zero and constant potential are found. Between them power law solution corresponded to equation of state for stiff matter, de Sitter solution, trigonometric and hyperbolic expansion solution. Various type of chiral fields evolution support listed above solutions.

gr-qc↗
arXiv2020

Spherical symmetric solutions of $f(R)$ gravity with a kinetic curvature scalar

We consider modified $f(R)$ gravity with a kinetic curvature scalar as a chiral self-gravitating model in a spherically symmetric spacetime. Most attention devoted to finding solutions for special case of scaling transformation when modified gravity transforms to Einstein frame from Jordan one. We proposed the method of determination of kinetic function for given scalar field dependence on space coordinate. New classes of solutions are found for special choice of $f(R)$ function.

gr-qc↗
arXiv2016

Development of Zeldovich's approach for cosmological distances measurement in the Friedmann Universe

We present our development of Zeldovich's ideas for the measurement of the cosmological angular diameter distance (ADD) in the Friedmann Universe. We derive the general differential equation for the ADD measurement which is valid for an open, spatially-flat and closed universe, and for any stress energy tensor. We solve the mentioned equations in terms of quadratures in a form suitable for further numerical investigations for the present universe filled by radiation, (baryonic and dark) matter and dark energy. We perform the numerical investigation in the absence of radiation, and show the strong dependence ADD on the filling of the cone of light rays (CLR). The difference of the empty and totally filled CLR may reach 600-700 Mps. for the redshift $f\simeq 3$.

gr-qc↗
arXiv2016

The effect of universe inhomogeneities on cosmological distance measurements

Using the focusing equation, the equation for the cosmological angular diameter distance is derived, based on the ideas of Academician Ya.B. Zel'dovich, namely, that the distribution of matter at small angles is not homogeneous, and the light cone is close to being empty. We propose some ways of testing a method for measuring the angular diameter distances and show that the proposed method leads to results that agree better with the experimental data than those obtained by the usual methods.

gr-qc↗