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E. V. Mikheeva

Publications and source records attributed to E. V. Mikheeva.

29 records · Page 2Linked to original sources
arXiv2012

A solution to the problems of cusps and rotation curves in dark matter halos in the cosmological standard model

We discuss various aspects of the inner structure formation in virialized dark matter (DM) halos that form as primordial density inhomogeneities evolve in the cosmological standard model. The main focus is on the study of central cusps/cores and of the profiles of DM halo rotation curves, problems that reveal disagreements among the theory, numerical simulations, and observations. A method that was developed by the authors to describe equilibrium DM systems is presented, which allows investigating these complex nonlinear structures analytically and relating density distribution profiles within a halo both to the parameters of the initial small-scale inhomogeneity field and to the nonlinear relaxation characteristics of gravitationally compressed matter. It is shown that cosmological random motions of matter `heat up' the DM particles in collapsing halos, suppressing cusp-like density profiles within developing halos, facilitating the formation of DM cores in galaxies, and providing an explanation for the difference between observed and simulated galactic rotation curves. The analytic conclusions obtained within this approach can be confirmed by the N-body model simulation once improved spatial resolution is achieved for central halo regions.

astro-ph.CO↗
arXiv2011

From the cosmological model to generation of the Hubble flow

We review different approaches to the problem of generating the observed Hubble flow, whose discussion was pioneered by A.D. Sakharov. Extrapolating the Cosmological Standard Model to the past makes it possible to determine physical properties of and conditions in the early universe. We discuss a new cosmogenesis paradigm based on studying geodesically complete geometries of black/white holes with integrable singularities.

astro-ph.CO↗
arXiv2003

Mass function of gravitationally bounded objects in the inhomogeneous Universe

We modify the Press-Schechter formalism to calculate the mass function of gravitationally bounded objects in a local Universe with size $L> 10h^{-1}$Mpc, i.e. separately in voids ($Ω_{m,L}<Ω_m$) and superclusters ($Ω_{m,L}>Ω_m$). The dependence of the abundance of gravitationally bounded objects on local matter density is analyzed.

astro-ph↗
arXiv2002

Current Status of cosmological models with mixed dark matter

An analysis of cosmological mixed dark matter models in spatially flat Friedmann Universe with zero $Λ$-term is presented. We argue that the introduction of cosmic gravity waves helps to satisfy observational constraints. The analysis of models is based on the confrontation with the mass function of clusters of galaxies and the CMB anisotropy. The implication of Press-Schechter formalism allowed to constrain $σ_8=0.52 \pm 0.01$. This normalisation of the spectrum of density perturbations has been used to calculate numerically the value of the large scale CMB anisotropy and the relative contribution of cosmological gravitational waves, T/S. We found that increasing $Ω_ν$ weakens the requirements to the value of T/S, however even for $Ω_ν\le 0.4$ the models with $h+n\ge 1.5$ suggest considerable abundance of gravitational waves, T/S${}^>_\sim 0.3$. Minimisation of the value T/S is possible only in the range of the red spectra ($n<1$) and small $h$ ($<0.6$). However the parameter $Ω_ν$ is strongly constrained by $ΔT/T$ data on the first acoustic peak of Sakharov oscillations. Assuming that T/S $\in[0,3]$ and taking into account observational data on the amplitude of the first acoustic peak we constrain the model parameters. We show that the considered models admit both moderate red and blue spectra of density perturbations $n\in [0.9,1.2]$ with rather high abundance hot dark matter, $Ω_ν\in [0.2,0.4]$. Any condition, $n<0.9$ or $Ω_ν<0.2$, decreases the relative amplitude of the first acoustic peak for more than 30% in comparison with its height measured by BOOMERanG.

astro-ph↗
arXiv2000

Generalised inflation with a gravitational wave background

We propose a Lambda-inflation model which explains a significant part of the COBE signal by primordial cosmic gravitational waves. The primordial density perturbations fulfill both the constraints of large-scale microwave background and galaxy cluster normalization. The model is tested against the galaxy cluster power spectrum and the high-multipole angular CMB anisotropy.

astro-ph↗
arXiv2000

Current status of cosmological MDM model

An analysis of cosmological models in spatially flat Friedmann Universe with cosmic gravitational wave background and zero $Λ$-term is presented. The number of free parameters is equal to 5, they are $σ_8$, $n$, $Ω_ν$, $Ω_b$, and $h$. The normalization of the spectrum of density perturbations on galaxy cluster abundance ($σ_8 = 0.52\pm 0.04$) has been used to calculate numerically the value of the large scale CMB anisotropy ($\ell\simeq 10$) and the relative contribution of cosmological gravitational waves T/S. Increasing $Ω_ν$ weaken the requirements to the value of T/S, however even for $Ω_ν\le 0.4$ the models with $h+n\ge 1.5$ suggest considerable abundance of gravitational waves: T/S${}^>_\sim 0.3$. In models with $Ω_ν\le 0.4$ and scale-invariant spectrum of density perturbations ($n=1$): T/S${}^>_\sim 10(h-0.47)$. Minimization of the value T/S is possible only in the range of the red spectra ($n<1$) and small $h$ ($<0.6$). It is shown that the models with T/S$\in [0, 3]$ admit both moderate red and blue spectra of density perturbations, $n\in[0.9,1.2]$, with rather high abundance hot dark matter, $Ω_ν\in [0.2,0.4]$. Any condition, $n<0.9$ or $Ω_ν<0.2$, decreases the relative amplitude of the first acoustic peak for more than 30% in comparison with its hight in the standard CDM normalized by COBE data.

astro-ph↗
arXiv2000

A generalized inflation model with cosmic gravitational waves

We propose a $Λ$-inflation model which explains a large fraction of the COBE signal by cosmic gravitational waves. The primordial density perturbations fulfil both the contraints of large-scale microwave background and galaxy cluster normalization. The model is tested against the galaxy cluster power spectrum and the high-multipole angular CMB anisotropy.

astro-ph↗
arXiv1999

Lambda-inflation and CMB anisotropy

We explore a broad class of three-parameter inflationary models, called the $Λ$-inflation, and its observational predictions: high abundance of cosmic gravitational waves consistent with the Harrison-Zel'dovich spectrum of primordial cosmological perturbations, the non-power-law wing-like spectrum of matter density perturbations, high efficiency of these models to meet current observational tests, and others. We show that a parity contribution of the gravitational waves and adiabatic density perturbations into the large-scale temperature anisotropy, T/S $\sim 1$, is a common feature of $Λ$-inflation; the maximum values of T/S (basically not larger than 10) are reached in models where (i) the local spectrum shape of density perturbations is flat or slightly red ($n_S{}_\sim^< 1$), and (ii) the residual potential energy of the inflaton is near the GUT scale ($V_0^{1/4} \sim 10^{16} GeV$). The conditions to find large T/S in the paradigm of cosmic inflation and the relationship of T/S to the ratio of the power spectra, $r$, and to the inflationary $γ$ and Hubble parameters, are discussed. We argue that a simple estimate, T/S$\simeq 3r\simeq 12γ\simeq (\frac{H}{6\times 10^{13}{\rm GeV}})^2$, is true for most known inflationary solutions and allows to relate straightforwardly the important parameters of observational and physical cosmology.

astro-ph↗
arXiv1998

Observational Constraints for Power-law spectra of Density Perturbations

We present an analysis of cosmological models with mixed dark matter (spectrum slope of density perturbations $n_S \in [0.6, 1.6]$, hot dark matter abundance $Ω_ν\in [0.0, 0.6]$) in spatially flat Universe, based on Press-Schechter formalism (P\&S). We found that the models with $n_S > 1$ and $Ω_ν< 0.5$ are preferable. Additionally, for all considered models we simulated $ΔT/T\vert_{10^0}$ and compared it with the COBE measured amplitude of CMB anisotropy. We found that the models favourable for galaxy cluster abundance need large amount of cosmological gravitational waves (T/S $> 1$).

astro-ph↗