arXiv subjects

E. V. Arbuzova

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

At least 19 recordsLinked to original sources

arXiv2026

Vacuum energy problem in anti-de Sitter space

We investigate the cosmological evolution of a universe with an initially large negative vacuum energy, corresponding to an anti-de Sitter (AdS) space-time. Such a universe inevitably contracts and collapses into a singularity. To prevent this collapse, we propose a dynamical mechanism of vacuum energy compensation based on a scalar field non-minimally coupled to the curvature scalar. Numerical and analytical calculations demonstrate that the suggested mechanism completely compensates the gravitational impact of the vacuum energy, successfully driving the curvature to zero. As a result, the universe avoids the singularity and evolves into a power-law expansion, typical for a radiation-dominated cosmology.

gr-qc↗

arXiv2026

Possible explanation of primordial $^7$Li deficit

A reduction mechanism of the theoretically predicted excessive abundance of $^7$Li via baryons evaporated by primordial black holes is suggested. It is shown that the fraction of $^7$Li with respect to the number density of baryons can be diminished down to the observed value via the process of $^7$Li transformation by neutron capture. The created in this process $^8$Li or $^8$Be quickly decay into a pair of $^4$He nuclei.

astro-ph.CO↗

arXiv2025

Dynamical mechanism of vacuum energy compensation

The model of vacuum energy compensation due to interaction of a scalar field $ϕ$ with curvature scalar of the form $βR ϕ^2 f(ϕ) $ is proposed. It is shown that with a simple power form of $f(ϕ)$ the exponential expansion, induced by vacuum energy (or what is the same by cosmological constant), is transformed into canonical cosmological evolution of the universe dominated by relativistic matter.

gr-qc↗

arXiv2025

The highest energy cosmic rays from superheavy dark matter particles

It is commonly accepted that high energy cosmic rays up to $10^{19}$ eV can be produced in catastrophic astrophysical processes. However the source of a few observed events with higher energies remains mysterious. We propose that they may originate from decay or annihilation of ultra heavy particles of dark matter. Such particles naturally appear in some models of modified gravity related to Starobinsky inflation.

hep-ph↗

arXiv2024

Cosmic rays from annihilation of heavy dark matter particles

The origin of the ultra high energy cosmic rays via annihilation of heavy stable, fermions "f", of the cosmological dark matter (DM) is studied. The particles in question are supposed to be created by the scalaron decays in $R^2$ modified gravity. Novel part of our approach is the assumption that the mass of these carriers of DM is slightly below than a half of the scalaron mass. In such a case the phase space volume becomes tiny. It leads to sufficiently low probability of "f" production, so their average cosmological energy density could be equal to the observed energy density of dark matter. Several regions of the universe, where the annihilation could take place, are studied. They include the whole universe under assumption of homogeneous energy density, the high density DM clump in the galactic centre, the cloud of DM in the Galaxy with realistic density distribution, and high density clusters of DM in the Galaxy. Possible resonance annihilation of $f \bar f$ into energetic light particle is considered. We have shown that the proposed scenario can successfully explain the origin of the ultrahigh energy flux of cosmic rays where the canonical astrophysical mechanisms are not operative.

hep-ph↗

arXiv2024

Superheavy SUSY-kind dark matter and high energy cosmic rays

The search for supersymmetric partners at Large Hadron Collider revealed negative result. Though, strictly speaking, it does not exclude low energy supersymmetry, but still it leads to strong constraints of the parameter space. Therefore the search for supersymmetric particles at higher energies becomes of interest. It is shown that in $R^2$-modified cosmology heavy particles with the interaction strength typical for supersymmetry could be promising candidates for carriers of dark matter. We consider the heating of the Universe at the post-inflationary stage via particle production by oscillating curvature scalar (scalaron). The bounds on the masses of dark matter particles are obtained for different dominant decay modes of the scalaron. Possible impact of superheavy particle decays on the spectrum of ultra high energy cosmic rays is discussed.

hep-ph↗

arXiv2023

Cosmic rays from heavy particle decays

Multidimensional modification of gravity with a smaller mass scale of the gravitational interaction is considered. Stable by assumption dark matter particles could decay via interactions with virtual black holes. The decay rates of such processes are estimated. It is shown that with the proper fixation of the parameters the decays of these ultra-massive particles can give noticeable contribution to the flux of high energy cosmic rays in particular, near the Greisen-Zatsepin-Kuzmin limit. Such particles can also create neutrinos of very high energies observed in the existing huge underwater or ice-cube detectors.

hep-ph↗

arXiv2023

Calculations of scalaron decay probabilities

The particle production through the scalaron decays are considered for several different channels. The central part of the work is dedicated to a study of the decay probability into two complex minimally coupled massless scalars. The calculations are performed by two different independent methods. In addition we calculated the decay probability into real minimally coupled massless scalars, conformally coupled massive scalars, massive fermions, and gauge bosons. The results are compared with the published papers which in some cases disagree with each other.

hep-ph↗

arXiv2022

Rates of particle production in $R^2$ gravity and supersymmetry-kind dark matter

Universe heating in $R^2$-modified gravity is considered. The rates of particle production by the scalaron are calculated for different decay channels. Freezing of massive stable relics with the interaction strength typical for supersymmetry is studied. It is shown that the bounds on masses of supersymmetry-kind particles allowing them to form the cosmological dark matter (DM)depend upon the dominant decay mode of the scalaron. In any case the results presented open much wider mass window for DM with the interaction strength typical for supersymmetry.

astro-ph.CO↗

arXiv2022

On graviton propagation in curved space-time background

Equation describing propagation of gravitational waves (GW) over arbitrary curved space-time background is analyzed. New terms, which are absent in the conventional homogeneous and isotropic Friedmann cosmology, are found. Some examples of realistic metric, where these new terms manifest themselves, are presented. Possible implications to very low frequency GW are briefly discussed.

gr-qc↗

arXiv2022

New Options for SUSY-kind Dark Matter

In the conventional cosmology masses of the stable supersymmetric relics, candidates for the dark matter (DM) particles, should be typically below 1 TeV. This is in conflict with the LHC bounds on the low energy SUSY. However, in $R^2$-gravity the masses of the stable particles with the interaction strength typical for SUSY could be much higher depending upon the dominant decay mode of the scalaron. We discuss the bounds on the masses of DM particles for the following dominant decay modes: to minimally coupled massless scalars, to massive fermions, and to gauge bosons.

hep-ph↗

arXiv2020

Superheavy dark matter in $R^2$-cosmology

The conventional Friedmann cosmology is known to be in tension with the existence of stable particles having interaction strength typical for supersymmetry and heavier than several TeV. A possible way to save life of such particles may be a modification of the standard cosmological expansion law in such a way that the density of these heavy relics would be significantly reduced. We study particle creation in the Starobinsky inflationary model for different decay channels of the scalaron. It is shown that in the process of thermalization superheavy stable particles with the coupling strength typical for the GUT SUSY could be created with the density equal to the observed density of dark matter.

hep-ph↗

arXiv2020

Superheavy dark matter in $R+R^2$ cosmology with conformal anomaly

Cosmological evolution and particle creation in $R^2$-modified gravity are considered for the case of the dominant decay of the scalaron into a pair of gauge bosons due to conformal anomaly. It is shown that in the process of thermalization superheavy dark matter with the coupling strength typical for the GUT SUSY can be created. Such dark matter would have the proper cosmological density if the particle mass is close to $10^{12}$ GeV.

hep-ph↗

arXiv2019

Dark matter in $R+R^2$ cosmology

Production of massive stable relics in $R^2$-modified gravity is considered. It is shown that the cosmological evolution and kinetics of massive species differs significantly from those in the conventional cosmology. The results are applied to the lightest supersymmetric particles and it is argued that they are viable candidates for the constituents of dark matter, if their mass is about 1000 TeV.

astro-ph.CO↗

arXiv2018

Distortion of the standard cosmology in R+R^2 theory

Universe history in $R^2$-gravity is studied from "beginning" up to the present epoch. It is assumed that initially the curvature scalar $R$ was sufficiently large to induce the proper duration of inflation. Gravitational particle production by the oscillating $R(t)$ led to a graceful exit from inflation, but the cosmological evolution in the early universe was drastically different from the standard one till the universe age reached the value of the order of the inverse decay rate of the oscillating curvature $R(t)$. This deviation from the standard cosmology might have a noticeable impact on the formation of primordial black holes and baryogenesis. At later time, after exponential decay of the curvature oscillations, cosmology may return to normality.

gr-qc↗

arXiv2018

Spontaneous and Gravitational Baryogenesis

Some problems of spontaneous and gravitational baryogenesis are discussed. Gravity modification due to the curvature dependent term in gravitational baryogensis scenario is considered. It is shown that the interaction of baryonic fields with the curvature scalar leads to strong instability of the gravitational equations of motion and as a result to noticeable distortion of the standard cosmology.

gr-qc↗

arXiv2017

Problems of spontaneous and gravitational baryogenesis

Spontaneous and closely related to it gravitational baryogenesis are critically analyzed. It is shown that the coupling of the curvature scalar to baryonic current, which induces nonzero baryonic asymmetry of the universe, simultaneously leads to higher order gravitational equations, which have exponentially unstable solutions. It is shown that this instability endangers the standard cosmology.

hep-ph↗

arXiv2017

Instability of gravitational baryogenesis with fermions

The derivative coupling of baryonic current to the curvature scalar in gravitational baryogenesis scenarios leads to higher order equations for gravitational field. It is shown that these equations are strongly unstable and destroy standard cosmology. This is a generalization of our earlier results obtained for scalar baryons to realistic fermions.

gr-qc↗