arXiv subjects

S. G. Rubin

Publications and source records attributed to S. G. Rubin.

At least 19 recordsLinked to original sources

arXiv2022

Hot primordial regions with anomalous hydrogenless chemical composition

We study primordial nucleosynthesis in hypothetical hot regions that could be formed by the primordial density inhomogeneities. It is shown that the regions survived up to the present times acquire an abnormally high metallicity. This conclusion holds in wide range of initial parameters of such regions. We considered the thermonuclear reaction rates and estimated abundances of deuterium and helium-3 and -4 inside these areas. It has been established that all baryons tend to form helium-4, which is the thermonuclear link in the chain of formation of heavier elements.

astro-ph.CO↗

arXiv2022

Local temperature distribution in the vicinity of gravitationally bound objects in the expanding Universe

We consider a cluster of Primordial Black Holes which is decoupled from the cosmological expansion (Hubble flow) and this region is heated as compared to the surrounding matter. The increased temperature inside the region can be explained by several mechanisms of Primordial Black Holes formation. We study the temperature dynamics of the heated region of Primordial Black Holes cluster.

gr-qc↗

arXiv2020

Neutrino cooling effect of primordial hot areas in dependence on its size

We consider the temperature dynamics of hypothetical primordial hot areas in the Universe. Such areas can be produced by the primordial density inhomogeneities and can survive to the modern era, in particular due to primordial black hole (PBH) cluster of size $R \gtrsim 1$ pc and more. Here we concentrate on the neutrino cooling effect which is realized due to reactions of weak $p\leftrightarrow n$ transitions and $e^{\pm}$ annihilation. The given neutrino cooling mechanism is found to work in a wide range of parameters. For those parameters typical for PBH cluster considered, the cooling mechanism is quite valuable for the temperatures $T \gtrsim 3$ MeV.

astro-ph.CO↗

arXiv2020

Formation of conserved charge at the de Sitter space

The article considers a new mechanism of charge accumulation in the early Universe in theories with compact extra dimensions. The relaxation processes in the extra space metric that take place during its formation lead to the establishment of symmetrical extra space configuration. As a result, the initial accumulation of the number associated with the symmetry occurs. We demonstrate this mechanism using a simple example of a two-dimensional apple-like extra space metric with $U(1)$-symmetry. The conceptual idea of the mechanism can be used to develop a model for the production of the baryon or lepton number in the early Universe.

gr-qc↗

arXiv2020

Neutrino Cooling of Primordial Hot Regions

The effect of neutrino cooling of possible primary regions filled by the hot matter is discussed. Such regions could contain the primordial density inhomogeneities of different origin and survive up to modern epoch. We show that the final temperature of such region is $\sim 10\, {\rm keV}$ provided that the initial temperature is within the interval $10\, {\rm keV} ... 100\, {\rm MeV}$. The cooling is realized due to the nuclear reactions containing $n-p$ transition. The lower limit $10\, {\rm keV}$ is accounted for by suppression of the reactions rates because of threshold effect and $n$, $e^{\pm}$ density diminishment.

astro-ph.CO↗

arXiv2019

Cosmology and matter induced branes

The extra space paradigm plays a significant role in modern physics and in cosmology as the specific case. In this review, the relation between the main cosmological parameters - Planck mass and Cosmological constants - and a metric of extra space is discussed. Matter distribution inside extra space and its effect on the 4-dimensional observational parameters is of particular interest. The ways to solve the Fine-tuning problem and the Hierarchy problem are analyzed.

gr-qc↗

arXiv2017

Reionization effect enhancement due to primordial black holes

Primordial black holes (PBH) could account for variety of phenomena like dark matter, reionization of the Universe, early quasars, coalescence of black holes registered through gravitational waves recently. Each phenomenon relates to PBH of a specific mass range. PBH mass spectra varies in a wide range depending on specific model. Earlier we have shown that PBH with monochromatic mass distribution around $5\times 10^{16}$ g value allow to re-ionize the Universe moderately. Here we show that reionization effect and contribution to dark matter can be simultaneously enhanced with more natural extended mass distribution in the range around the same mass value.

astro-ph.CO↗

arXiv2016

Cosmological implications of Higgs field fluctuations during inflation

Cosmological implications of Higgs field fluctuations during inflation are considered. This study is based on the Standard Model and the standard quadratic model of chaotic inflation where the Higgs field is minimally coupled to gravity and has no direct coupling to the inflaton. In the Standard model the renormalisation group improved effective potential develops an instability (an additional minimum and maximum) at large field values. It is shown that such a new maximum should take place at an energy scale above $10^{14} \;\text{GeV},$ otherwise a universe like ours is extremely unlikely. The extension to the case of the Higgs field interacting with the inflaton field is discussed.

astro-ph.CO↗

arXiv2015

Formation and Search of Large Scale Antimatter Regions

In the present paper we discuss a generation of large antimatter regions with sizes exceeding the critical surviving size. In the modern epoch domains with high antimatter density evolve to single galaxies with a peculiar content of anti-helium and anti-deuterium.

astro-ph.CO↗

arXiv2014

Signatures of primordial black hole dark matter

The nonbaryonic dark matter of the Universe is assumed to consist of new stable forms of matter. Their stability reflects symmetry of micro world and mechanisms of its symmetry breaking. In the early Universe heavy metastable particles can dominate, leaving primordial black holes (PBHs) after their decay, as well as the structure of particle symmetry breaking gives rise to cosmological phase transitions, from which massive black holes and/or their clusters can originate. PBHs can be formed in such transitions within a narrow interval of masses about $10^{17}$g and, avoiding severe observational constraints on PBHs, can be a candidate for the dominant form of dark matter. PBHs in this range of mass can give solution of the problem of reionization in the Universe at the redshift $z\sim 5... 10$. Clusters of massive PBHs can serve as a nonlinear seeds for galaxy formation, while PBHs evaporating in such clusters can provide an interesting interpretation for the observations of point-like gamma-ray sources. Analysis of possible PBH signatures represents a universal probe for super-high energy physics in the early Universe in studies of indirect effects of the dark matter.

astro-ph.CO↗

arXiv2014

Role of initial conditions in the Universe formation

A dependence of low energy physics on initial conditions in the framework of multidimensional gravity is discussed. It is shown that the observable symmetries could be a result of specific topologies originated from space-time foam.

gr-qc↗

arXiv2013

Baryon number of the Universe as a result of extra space dynamics

Origin of baryon asymmetry is studied in the framework of extra dimensional approach. Baryon excess production and the symmetrization of extra-space are performed simultaneously. Baryon number is conserved long after the inflationary stage when the U(1) symmetry is achieved.

gr-qc↗

arXiv2013

Higgs-Like Field and Extra Dimensions

We study the origin of the Higgs field in the framework of the universal extra dimensions. It is shown that a Higgs-like Lagrangian can be extracted from a metric of an extra space. The way to distinguish our model and the Standard Model is discussed.

gr-qc↗

arXiv2013

Nonlinear multidimensional gravity and the Australian dipole

The existing observational data on possible variations of fundamental physical constants (FPC) confirm more or less confidently only a variability of the fine structure constant $α$ in space and time. A model construction method is described, where variations of $α$ and other FPCs (including the gravitational constant $G$) follow from the dynamics of extra space-time dimensions in the framework of curvature-nonlinear multidimensional theories of gravity. An advantage of this method is a unified approach to variations of different FPCs. A particular model explaining the observable variations of $α$ in space and time has been constructed. It comprises a FRW cosmology with accelerated expansion, perturbed due to slightly inhomogeneous initial data.

gr-qc↗

arXiv2012

Low energy physics and properties of extra space

The mechanism of low energy physics formation in the framework of multidimensional gravity is discussed. It is shown that a wide set of parameters of a primary theory could lead to the observable Universe. Quantum fluctuations of extra space metric and its consequent classical evolution play an important role in this process.

gr-qc↗

arXiv2012

Clusters of Black Holes as Point-Like Gamma-ray Sources

The possibility of identifying some of Galactic gamma-ray sources as clusters of primordial black holes is discussed. The known scenarios of supermassive black hole formation indicate the multiple formation of lower-mass black holes. Our analysis demonstrates that due to Hawking evaporation the cluster of black holes with masses about $10^{15}$ g could be observed as a gamma-ray source. The total mass of typical cluster is $\sim 10 M_\odot$. Detailed calculations have been performed on the basis of specific model of primordial black hole formation.

astro-ph.HE↗

arXiv2012

Emergence of symmetries

The mechanism of symmetry formation is discussed in the framework of multidimensional gravity. It is shown that this process is strictly connected to the entropy decrease of compact space. The existence of low energy symmetries is not postulated from the beginning. They could be absent during the inflationary stage under certain conditions discussed in the paper.

gr-qc↗

arXiv2012

The universe formation by a space reduction cascade with random initial parameters

In this paper we discuss the creation of our universe using the idea of extra dimensions. The initial, multidimensional Lagrangian contains only metric tensor. We have found many sets of the numerical values of the Lagrangian parameters corresponding to the observed low-energy physics of our universe. Different initial parameters can lead to the same values of fundamental constants by the appropriate choice of a dimensional reduction cascade. This result diminishes the significance of the search for the 'unique' initial Lagrangian. We also have obtained a large number of low-energy vacua, which is known as a 'landscape' in the string theory.

gr-qc↗