arXiv subjects

D. A. Varshalovich

Publications and source records attributed to D. A. Varshalovich.

27 records · Page 2Linked to original sources

arXiv2007

Rapid HeII->HeI recombination and radiation concerned with this process

Recombination of the primordial helium plasma (HeII->HeI, $z \simeq 1500 - 3000$) is considered. This process has an effect on the CMBR anisotropy and CMBR spectrum distortion. In this work an influence of neutral hydrogen on kinetics of HeII->HeI recombination is investigated in the frame of the standard cosmological model. It is shown that small amount of neutral hydrogen ($10^{-5} - 10^{-2}$ of total number of hydrogen ions and atoms) leads to acceleration of HeII->HeI recombination at $z\lesssim 2000$ and at $z\lesssim 1600$ quasi-equilibrium HeII->HeI recombination (according to the Saha formula) becomes valid.

astro-ph↗

arXiv2007

The redshift distribution of absorption-line systems in QSO spectra

A statistical analysis of the space-time distribution of absorption-line systems (ALSs) observed in QSO spectra within the cosmological redshift interval $z$=0.0--3.7 is carried out on the base of our catalog of absorption systems (Ryabinkov et al. 2003). We confirm our previous conclusion that the $z$-distribution of absorbing matter contains non-uniform component displaying a pattern of statistically significant alternating maxima (peaks) and minima (dips). Using the wavelet transformation we determine the positions of the maxima and minima and estimate their statistical significance. The positions of the maxima and minima of the $z$-distributions obtained for different celestial hemispheres turn out to be weakly sensitive to orientations of the hemispheres. The data reveal a regularity (quasi-periodicity) of the sequence of the peaks and dips with respect to some rescaling functions of $z$. The same periodicity was found for the one-dimensional correlation function calculated for the sample of the ALSs under investigation. We assume the existence of a regular structure in the distribution of absorption matter, which is not only spatial but also temporal in nature with characteristic time varying within the interval 150--650 Myr for the cosmological model applied.

astro-ph↗

arXiv2005

CMBR distortion concerned with recombination of the primordial hydrogen plasma

CMBR distortion concerned with recombination of the primordial plasma is calculated in frequency band from 1 GHz to 100 GHz in the frame of the standard cosmological model for different values of cosmological density parameters: nonrelativistic matter density $Ω_m$ and baryonic matter density $Ω_b$. Comparison of these results with observational data which will be obtained from planned experiments may be used for independent determination of the cosmological parameters $Ω_m$ and $Ω_b$.

astro-ph↗

arXiv2004

A catalogue of absorption-line systems in QSO spectra

We present a new catalog of absprption-line systems identified in the quasar spectra. It contains data on 821 QSOs and 8558 absorption systems comprizing 16139 absorption lines with measured redshifts in the QSO spectra. The catalog includes absorption-line systems consisting of lines of heavy elements, lines of neutral hydrogen, Lyman limit systems, damped Lyαabsorption systems, and broad absorption-line systems. The catalog is available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/412/707 and at www.ioffe.ru/astro/QC. Using the data of the present catalog we also discuss redshift distributions of absorption-line systems.

astro-ph↗

arXiv2000

Puzzle of the constancy of fundamental constants

We discuss experiments and observations aimed at testing the possible space-time variability of fundamental physical constants, predicted by the modern theory. Specifically, we consider two of the dimensionless physical parameters which are important for atomic and molecular physics: the fine-structure constant and the electron-to-proton mass ratio. We review the current status of such experiments and critically analyze recent claims of a detection of the variability of the fine-structure constant on the cosmological time scale. We stress that such a detection remains to be checked by future experiments and observations. The tightest of the firmly established upper limits read that the considered constants could not vary by more than 0.015% on the scale of 10 Gigayears.

physics.atom-ph↗

arXiv2000

Testing cosmological variability of fundamental constants

One of the topical problems of contemporary physics is a possible variability of the fundamental constants. Here we consider possible variability of two dimensionless constants which are most important for calculation of atomic and molecular spectra (in particular, the X-ray ones): the fine-structure constant α=e^2/\hbar c and the proton-to-electron mass ratio μ=m_p/m_e. Values of the physical constants in the early epochs are estimated directly from observations of quasars - the most powerful sources of radiation, whose spectra were formed when the Universe was several times younger than now. A critical analysis of the available results leads to the conclusion that present-day data do not reveal any statistically significant evidence for variations of the fundamental constants under study. The most reliable upper limits to possible variation rates at the 95% confidence level, obtained in our work, read: |\dotα/α| < (1.4e-14)/yr, |\dotμ/μ| < (1.5e-14)/yr on the average over the last ten billion years.

physics.atom-ph↗

arXiv1998

The fine-structure constant: a new observational limit on its cosmological variation and some theoretical consequences

Endeavours of the unification of the four fundamental interactions have resulted in a development of theories having cosmological solutions in which low-energy limits of fundamental physical constants vary with time. The validity of such theoretical models should be checked by comparison of the theoretical predictions with observational and experimental bounds on possible time-dependences of the fundamental constants. Based on high-resolution measurements of quasar spectra, we obtain the following direct limits on the average rate of the cosmological time variation of the fine-structure constant α: |\dotα/α| < 1.9 \times 10^{-14} yr^{-1} is the most likely limit, and |\dotα/α| < 3.1 \times 10^{-14} yr^{-1} is the most conservative limit. Analogous estimates published previously, as well as other contemporary tests for possible variations of α(those based on the "Oklo phenomenon", on the primordial nucleosynthesis models, and others) are discussed and compared with the present upper limit. We argue that the present result is the most conservative one.

astro-ph↗

arXiv1998

Testing cosmological variability of the proton-to-electron mass ratio using the spectrum of PKS 0528-250

Multidimensional cosmologies allow for variations of fundamental physical constants over the course of cosmological evolution, and different versions of the theories predict different time dependences. In particular, such variations could manifest themselves as changes of the proton-to-electron mass ratio μ=m_p/m_e over the period of ~ 10^{10} years since the moment of formation of high-redshift QSO spectra. Here we analyze a new, high-resolution spectrum of the z=2.81080 molecular hydrogen absorption system toward the quasar PKS 0528-250 to derive a new observational constraint to the time-averaged variation rate of the proton-to-electron mass ratio. We find |\dotμ / μ| < 1.5 \times 10^{-14}/year, which is much tighter than previously measured limits.

astro-ph↗

arXiv1996

Testing cosmological variations of fundamental physical constants by analysis of quasar spectra

Contemporary multidimensional cosmological theories predict different variations of fundamental physical constants in course of the cosmological evolution. On the basis of the QSO spectra analysis, we show that the fine-structure constant α=e^2/(\hbar c) and the proton-to-electron mass ratio μ=m_p/m_e reveal no statistically significant variation over the last 90% of the lifetime of the Universe. At the 2σsignificance level, the following upper bounds are obtained for the epoch corresponding to the cosmological redshifts z ~ 3 (i.e., ~ 10 Gyr ago): |Δα/α| < 0.00016 and |Δμ/μ| < 0.00022. The corresponding upper limits to the time-average rates of the constant variations are |dα/(αdt)| < 1.6\times 10^{-14} yr^{-1} and |dμ/(μdt)| < 2.2\times10^{-14} yr^{-1}. These limits serve as criteria for selection of those theoretical models which predict αand μvariation with the cosmological time. In addition, we test a possible anisotropy of the high-redshift fine splitting over the celestial sphere, which might reveal a non-equality of αvalues in causally disconnected areas of the Universe.

astro-ph↗