156 results on '"V. K. Dubrovich"'
Search Results
2. Some Features of the Direct and Inverse Double-Compton Effect as Applied to Astrophysics
- Author
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T. Zalialiutdinov and V. K. Dubrovich
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Physics ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,Photon ,Soft photon ,Atomic Physics (physics.atom-ph) ,Scattering ,QC1-999 ,Compton scattering ,FOS: Physical sciences ,Detailed balance ,Electron ,Radiation ,Physics - Atomic Physics ,Computational physics ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Infrared divergence ,quantum electrodynamics ,double Compton scattering ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
In the present paper, the process of inverse double-Compton (IDC) scattering is considered in the context of astrophysical applications. It is assumed that the two hard X-ray photons emitted from an astrophysical source are scattered on a free electron and converted into a single soft photon of optical range. Using the QED S-matrix formalism for the derivation of a cross-section of direct double-Compton (DDC) scattering and assuming detailed balance conditions, an analytical expression for the cross-section of the IDC process is presented. It is shown that at fixed energies of incident photons, the inverse cross-section has no infrared divergences, and its behavior is completely defined by the spectral characteristics of the photon source itself, in particular by the finite interaction time of radiation with an electron. Thus, even for the direct process, the problem of resolving infrared divergence actually refers to a real physical source of radiation in which photons are never actually plane waves. As a result, the physical frequency profile of the scattered radiation for DDC as well as for IDC processes is a function of both the intensity and line shape of the incident photon field.
- Published
- 2021
3. Observational manifestations of ‘cosmological dinosaurs’ at redshifts z ∼ 20
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Yu. N. Eroshenko, S. I. Grachev, and V. K. Dubrovich
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Physics ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,010308 nuclear & particles physics ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Dark matter ,Cosmic background radiation ,FOS: Physical sciences ,Astronomy and Astrophysics ,Primordial black hole ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Radius ,01 natural sciences ,Universe ,Redshift ,General Relativity and Quantum Cosmology ,Space and Planetary Science ,0103 physical sciences ,Hydrogen line ,Halo ,010303 astronomy & astrophysics ,Astrophysics - Cosmology and Nongalactic Astrophysics ,media_common - Abstract
We consider a primordial black hole of very high mass, $10^9-10^{10}M_\odot$, surrounded by dark matter and barionic halo at redshifts $z\sim20$ without any local sources of energy release. Such heavy and concentrated objects in the early universe were previously called ``cosmological dinosaurs''. Spectral distribution and spatial variation of the brightness in the 21 cm line of atomic hydrogen are calculated with the theory of radiation transfer. It is shown that a narrow and deep absorption arises in the form of the spherical shell around the primordial black hole at the certain radius. The parameters of this shell depend almost exclusively on the mass of the black hole. The hardware and methodological aspects of the search for such objects are discussed., 9 pages, 10 figures
- Published
- 2021
4. Superconducting Receivers for Space, Balloon, and Ground-Based Sub-Terahertz Radio Telescopes
- Author
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G. M. Bubnov, Vyacheslav Vdovin, Artem Chekushkin, Valery P. Koshelets, V. K. Dubrovich, Lyudmila V. Filippenko, S. A. Lemzyakov, Andrey M. Baryshev, K. I. Rudakov, V. S. Edelman, D. V. Nagirnaya, Andrey Smirnov, S. N. Vdovichev, Yu. Yu. Balega, A. A. Gunbina, G. V. Yakopov, M. A. Tarasov, I. I. Zinchenko, P. N. Dmitriev, Andrey Khudchenko, R. A. Yusupov, V. B. Haikin, and Astronomy
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Nuclear and High Energy Physics ,Terahertz radiation ,LINES ,law.invention ,Telescope ,Radio telescope ,Optics ,DESIGN ,law ,Condensed Matter::Superconductivity ,Broadband ,Electrical and Electronic Engineering ,DETECTOR ,MILLIMETER ,Physics ,Noise temperature ,PRIMORDIAL HYDROGEN ,business.industry ,Detector ,ELECTRON BOLOMETER ,Astronomy and Astrophysics ,Statistical and Nonlinear Physics ,LOCAL BURST MODEL ,Electronic, Optical and Magnetic Materials ,WAVE ,RADIATION ,business ,TEMPERATURE-FLUCTUATIONS SCATTERING ,Microwave ,Radio astronomy - Abstract
We give a review of both our own original scientific results of the development of superconducting receivers for sub-terahertz astronomy and the main leading concepts of the global instrumentation. The analysis of current astronomical problems, the results of microwave astroclimate research, and the development of equipment for sub-terahertz radio astronomy studies justify the need and feasibility of a major infrastructure project in Russia to create a sub-terahertz telescope, as well as to enhance the implementation of the ongoing Millimetron and Suffa projects. The following results are discussed: i) superconducting coherent receivers and broadband subterahertz detectors for space, balloon, and ground-based radio telescopes have been developed and tested; ii) ultrasensitive receiving systems based on tunnel structures such as superconductor-insulator-superconductor (SIS) and superconductor-insulator-normal metal-insulator-superconductor (SINIS) have been created, fabricated, and examined; iii) a receiving array based on SINIS detectors and microwave readout system for such structures has been implemented; iv) methods for manufacturing high-quality tunnel structures Nb/AlOx/Nb and Nb/AlN/NbN based on niobium films with a current density of up to 30 kA/cm(2) have been developed. Receivers operated at 200 to 950 GHz and having a noise temperature only a factor of 2 to 5 higher than the quantum limit have been created and tested.
- Published
- 2020
5. Absorption in the 21-cm Line in Primordial Matter Density Fluctuations at the Stage of Their Nonlinear Compression
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V. K. Dubrovich and S. I. Grachev
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Physics ,010308 nuclear & particles physics ,Cosmic microwave background ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Radius ,01 natural sciences ,Spectral line ,Redshift ,Computational physics ,Space and Planetary Science ,0103 physical sciences ,Radiative transfer ,Hydrogen line ,Absorption (electromagnetic radiation) ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,Line (formation) - Abstract
The mechanisms of absorption formation in the cosmic microwave background (CMB) spectrum at the frequency of the 21-cm line of the transition between the ground-state hyperfine sublevels of the hydrogen atom are analyzed. We show that a strong nonlinearity at the compression stage of primordial matter density fluctuations can give rise to a significant (in depth) absorption even before the explosions of the first stars. In this case, the main effect is due to the heating of matter in a certain narrow range of temperatures under cloud compression. We consider a steady-state radiative transfer in the 21-cm line in a medium that represents a contracting primordial matter density fluctuation at a given redshift z modeled by a homogeneous spherically symmetric cloud in the state of collapse with an adiabatic change in the gas temperature. For a sequence of cloud states with different degrees of compression we have calculated the frequency profiles of the line in the flux of radiation emerging from the cloud. In the initial state we specify the cloud radius r0, while the gas density is assumed to be equal to the mean cosmological density for a given redshift. We show that for a separate cloud at z = 20, r0 = 1 kpc, and a degree of radius compression of 1.9 the absorption depth in the line center can reach 0.9 K. When averaged over an ensemble of clouds, the central frequency of the line and its width are determined by the details of the fluctuation evolution dynamics.
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- 2019
6. Production and evaporation of micro black holes as a link between mirror universes
- Author
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Yury Eroshenko, V. K. Dubrovich, Maxim Yu. Khlopov, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
- Subjects
Particle physics ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,interpretation of experiments: CERN LHC Coll ,media_common.quotation_subject ,Planck mass ,FOS: Physical sciences ,Astrophysics::Cosmology and Extragalactic Astrophysics ,GeV ,01 natural sciences ,dark matter: parametrization ,Cosmology ,evaporation ,General Relativity and Quantum Cosmology ,Micro black hole ,symbols.namesake ,Big Bang nucleosynthesis ,cosmological model: parameter space ,0103 physical sciences ,Planck ,010306 general physics ,black hole: production ,media_common ,Physics ,010308 nuclear & particles physics ,temperature: reheating ,nucleosynthesis: primordial ,scale: Planck ,matter: mirror ,Universe ,baryon ,Black hole ,symbols ,higher-dimensional ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,Mirror matter ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
It is shown that the equalization of temperatures between our and mirror sectors occurs during one Hubble time due to microscopic black hole production and evaporation in particle collisions if the temperature of the Universe is near the multidimensional Plank mass. This effect excludes the multidimensional Planck masses smaller than the reheating temperature of the Universe ($\sim10^{13}$ GeV) in the mirror matter models, because the primordial nucleosynthesis theory requires that the temperature of the mirror world should be lower than ours. In particular, the birth of microscopic black holes in the LHC is impossible if the dark matter of our Universe is represented by baryons of mirror matter. It excludes some of the possible coexisting options in particle physics and cosmology. Multidimensional models with flat additional dimensions are already strongly constrained in maximum temperature due to the effect of Kaluza-Klein mode (KK-mode) overproduction. In these models, the reheating temperature should be significantly less than the multidimensional Planck mass, so our restrictions in this case are not paramount. The new constraints play a role in multidimensional models in which the spectrum of KK-modes does not lead to their overproduction in the early Universe, for example, in theories with hyperbolic additional space., Comment: 8 pages, 1 figure, accepted for publication in Phys. Rev. D, replaced by the accepted version
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- 2021
7. Supermassive primordial black holes at high redshifts
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V. K. Dubrovich, Yu. N. Eroshenko, and S. I. Grachev
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Physics ,Space and Planetary Science ,Astrophysics::High Energy Astrophysical Phenomena ,Cosmic microwave background ,Astronomy and Astrophysics ,Primordial black hole ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Astrophysics::Galaxy Astrophysics ,Mathematical Physics ,Redshift ,Radio astronomy - Abstract
We consider some properties and possible observational manifestations of the very heavy primordial black holes (PBHs), with masses [Formula: see text]. These black holes should be surrounded by the dense dark matter and baryonic halos even at early cosmological epochs. There are mechanisms as for radiation emission in the centers due to accretion and for deep absorption of relic radiation at the periphery of the halos. We calculate the absorption profile in the 21[Formula: see text]cm line of atomic hydrogen by solving the equations of radiation transfer through the baryonic halo around a PBH. The calculations show that a spherical absorbing layer appears around the object, which can be observed with radio telescopes. Also, at some epochs, shock waves may form at the periphery of the objects. The accelerated charged particles can radiate in radio frequency band, so it is possible that these objects can explain the recently discovered radio circles.
- Published
- 2021
8. Luminescence in Primordial Helium Lines at the Pre-recombination Epoch
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V. K. Dubrovich and S. I. Grachev
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Physics ,Photon ,Quantum yield ,Astronomy and Astrophysics ,01 natural sciences ,Redshift ,Spectral line ,Space and Planetary Science ,Excited state ,0103 physical sciences ,Radiative transfer ,Atomic physics ,010306 general physics ,Absorption (electromagnetic radiation) ,010303 astronomy & astrophysics ,Line (formation) - Abstract
The formation of luminescent subordinate He I lines by the absorption of radiation from a source in lines of the main He I series in an expanding Universe is considered. A burst of radiation in continuum is assumed to occur at some instant of time corresponding to redshift z0. This radiation is partially absorbed at different z < z0 in lines of the main He I series (different pumping channels) and then is partially converted into radiation in subordinate lines. If ν ik is the laboratory transition frequency of some subordinate line emerging at some z, then at the present epoch its frequency will be ν = ν ik /(1 + z). The quantum yield, i.e., the number of photons emitted in the subordinate line per initial excited atom, has been calculated for different z (and, consequently, for different ν). Several pumping channels have been considered. We show that the luminescent lines can be both emission and absorption ones; the same line can be an emission one for one of the pumping channels and an absorption one for another. For example, the 1s2s–1s2p (1S–1P*) line is an emission one for the 1s2–1s2p pumping and an absorption one for the 1s2–1s3p pumping. We show that in the frequency range 30–80 GHz the total quantum yield for the first and second of the above channels can reach +50 and −50%, respectively.
- Published
- 2018
9. Local burst model of CMB temperature fluctuations: scattering in primordial hydrogen lines
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S. I. Grachev and V. K. Dubrovich
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Physics ,Opacity ,Space and Planetary Science ,Thomson scattering ,Scattering ,Cosmic microwave background ,Radiative transfer ,Hydrogen line ,Astronomy and Astrophysics ,Black-body radiation ,Astrophysics ,Redshift - Abstract
The propagation of an instantaneous burst of isotropic radiation from the time of its onset at some redshift z0 to the time of its detection at the present epoch (at z = 0) is considered within the framework of a flat Universe. Thomson scattering by free electrons and scattering in primordial hydrogen lines (Hα, Hβ, Pα, and Pβ) are believed to be the sources of opacity, with the single-scattering albedo in the lines being calculated by taking into account the deexcitation of the upper levels of the transitions being considered under the action of background blackbody radiation. The profiles of these lines in the burst spectrum at the present epoch have been constructed for various z0 at various distances from the burst center. To a first approximation, these profiles do not depend on the burst radiation spectrum and intensity. It is shown that the lines are purely absorption ones at a sufficiently large distance, but an emission component can appear with decreasing distance, which strengthens as the distance decreases, while the absorption component weakens. The absorption depth in the combined profile can reach 2 ×10−4 for the Hα and Hβ lines and 7 × 10−6 for the Pα and Pβ lines. In this case, the relative amplitude of the temperature fluctuations lies within the range 10−7−10−9. The calculations have been performed for bursts with different characteristic initial sizes. At the same z0, the hydrogen line profiles essentially coincide for sizes smaller than some value, and the contrast of the lines decreases with increasing burst size for greater ones.
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- 2015
10. On the possibility of observable signatures of μp and (μ 4He)+ lines on the spectra of astrophysical sources
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T. Zalialiutdinov and V. K. Dubrovich
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Physics ,chemistry.chemical_element ,Quantum yield ,Observable ,Radiation ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Spectral line ,010305 fluids & plasmas ,Ion ,chemistry ,0103 physical sciences ,Physics::Atomic and Molecular Clusters ,Physics::Atomic Physics ,Atomic physics ,010306 general physics ,Luminescence ,Mathematical Physics ,Helium ,Exotic atom - Abstract
We examine the processes of the luminescence in subordinate lines of muonic hydrogen $ \mu p $ and muonic helium ion $ (\mu ^4\mathrm{He})^{+} $ in the presence of background source of X-ray emission. It is supposed that a certain amount of muonic atoms existing in the vicinity of astrophysical source reemits absorbed radiation in the subordinate lines. The intensity of luminescence of such a process is proportional to the quantum yield which was calculated for different pumping channels and different models of spectra. It is shown that the luminescent lines of muonic hydrogen and muonic helium ion can be very noticeable in the spectrum of background source.
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- 2020
11. Searching for New Sites for THz Observations in Eurasia
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Igor Zinchenko, Andrey S. Marukhno, Yuriy Yu . Balega, Evgeniy B. Abashin, Oleg S. Bolshakov, Grigoriy M. Bubnov, Stepan Yu. Dryagin, Vladimir I. Nosov, Vyacheslav Vdovin, and V. K. Dubrovich
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Radiation ,Precipitable water ,Terahertz radiation ,law.invention ,Telescope ,Observatory ,law ,Very-long-baseline interferometry ,Environmental science ,Satellite ,Electrical and Electronic Engineering ,Optical depth ,Remote sensing ,Radio astronomy - Abstract
This paper deals with the preliminary results of the astroclimate monitoring in the short millimeter-wave band in the territory of the CIS countries. The optical depths for the 3-mm and 2-mm-band windows have been determined with the atmospheric dip method. The preliminary results of single measurements taken at Mus-Khaya Mountain (2,000 m/6,560 ft, Eastern Yakutia) and in Central Russia are presented. The paper also deals with the results of the observations of the first half of 2014 done within the regular monitoring of the astroclimate conditions combined with the meteorological observations at the site of the BTA telescope in the North Caucasus (2,000 m/6,560 ft) and on the Suffa Plateau (2,400 m/7,870 ft, Uzbekistan). The collected statistical data yield the mean number of cloudless days per year. In addition, the seasonal variations of the precipitable water vapour (PWV) have been approximately calculated for each site explored. Knowing the PWV, the total absorption can be predicted for different atmospheric windows, including the terahertz band (2.0 mm, 1.3 mm, and 0.87 mm). Using available data on the measurements of the absorption, the PWV, height, etc., suitability of the site can be evaluated for potential stationing of a millimeter or a submillimeter wave range observatory. The ultimate goal of this research is to find a suitable location for the radio astronomic observatory designed for the ground support of the future submillimeter wave VLBI space mission (“Millimetron”), as well as for the terahertz satellite telecommunication and CMB observations.
- Published
- 2015
12. Gain of parabolic mesh reflector antennas with arbitrary depths
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V. K. Dubrovich, S. B. Glybovsky, and V. P. Akimov
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Physics ,Ideal (set theory) ,Physics and Astronomy (miscellaneous) ,business.industry ,Aperture ,Mesh networking ,Astrophysics::Instrumentation and Methods for Astrophysics ,Reflector (antenna) ,Square (algebra) ,Optics ,Focal length ,Boundary value problem ,business ,Electrical conductor - Abstract
Analytical expressions for calculating the gain of a parabolic mesh reflector with arbitrary ratio of the focal length to aperture diameter have been derived using the method of averaged boundary conditions. The results are obtained for a dense thin-wire mesh with square cells and ideal electric contacts between conductors at junctions. Specific features of the influence of mesh topology on the gain of reflectors with various depths are considered.
- Published
- 2013
13. Local Bursts Model of CMB Temperature Fluctuations: Scattering in Resonance Lines of Primordial Hydrogen and Helium
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S. I. Grachev and V. K. Dubrovich
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Physics ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,Scattering ,Thomson scattering ,Cosmic microwave background ,chemistry.chemical_element ,FOS: Physical sciences ,Astronomy and Astrophysics ,01 natural sciences ,Resonance (particle physics) ,Redshift ,Amplitude ,chemistry ,Space and Planetary Science ,0103 physical sciences ,Radiative transfer ,Atomic physics ,010306 general physics ,010303 astronomy & astrophysics ,Helium ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
Within the framework of a flat cosmological model a propagation of an instantaneous burst of isotropic radiation is considered from the moment of its beginning at some initial redshift z0 to the moment of its registration now (at z=0). We take into account Thomson scattering by free electrons and scattering in La and Lb lines of primordial hydrogen and in lines 1s2 - 1s2p, 1s3p (1S-1P*) of HeI. It is shown that relative amplitude of spectrum distortions caused by scattering in these lines may be from 1000 to 10000 times greater than maximum possible amplitude due to scattering in subordinate lines considered in our previous paper (Dubrovich, Grachev, 2015). In a linear approximation on the optical thickness in the lines the profiles of distortions in resonance lines turn out to be purely in absorption and do not depend on both direction and distance to the burst center in contradistinction to the profiles in subordinate lines. The profiles contain jumps on frequencies corresponding to appearance of a source (burst) at a given redshift z=z0. For z0=5000 the jumps in hydrogen La and Lb lines are on frequencies 493 and 584 GHz respectively and jumps in two HeI lines are on 855 and 930 GHz for z0=6000. Relative magnitude of jumps amounts to 1e-4 - 3e-3., Comment: 15 pages, 7figures. Submitted to Astronomy Letters
- Published
- 2016
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14. Spectral and spatial fluctuations of cosmic microwave background radiation. RATAN-600 radio telescope observations with a Fourier spectral analyzer
- Author
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A. P. Venger, I. V. Gosachinskij, and V. K. Dubrovich
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Physics ,Cosmic microwave background ,Astronomy ,Rotational transition ,Astronomy and Astrophysics ,Astrophysics ,Spectral line ,law.invention ,Radio telescope ,Celestial pole ,law ,Angular resolution ,Emission spectrum ,Maser ,Instrumentation - Abstract
The “circumpolar survey” technique allowed us to achieve a rather high antenna temperature sensitivity of 0.5 mK at 6 cm on a fixed antenna with a relatively narrow frequency resolution band (600 kHz) and an angular resolution of 45″ × 7′. Starting from 2007 we use a Fourier spectral analyzer with a survey band 10 times broader than that of previous observations. This upgrade allowed us to rapidly perform repeated test observations, which confirmed the power-law nature and the frequency structure of spatial spectra in two strips in the vicinity of the celestial pole in the 4′–16′ interval of angular periods. These observations also showed that the Galactic CH molecular line that was by chance captured in our survey strip (Λ-doubling of rotational transition) has nothing to do with the emission spectra we obtained. The angular pattern of emission in two main lines of Λ-doubling (4847.84 and 4870.12 MHz) is absolutely different, whereas there is practically no maser amplification in the CH line to explain this fact. Our observations also confirm the H110 α line (4874.157 MHz), which forms in the tenuous ionized Galactic hydrogen at such relatively high latitudes. Other features of the spatial spectra also appear to be quite real, although their interpretation remains unclear and requires further studies.
- Published
- 2012
15. Influence of short-duration matter temperature perturbations on the cosmological hydrogen recombination spectrum
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S. I. Grachev, V. K. Dubrovich, and V. G. Romanyuk
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Physics ,Hydrogen ,Gaussian ,Perturbation (astronomy) ,chemistry.chemical_element ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Redshift ,Cosmology ,symbols.namesake ,Wavelength ,Amplitude ,chemistry ,Space and Planetary Science ,symbols ,Atomic physics ,Recombination - Abstract
A perturbation in the ratio of the matter temperature to the radiation temperature in the form of a Gaussian with amplitude A and width σ (in units of the redshift z) centered at some redshift zc is considered, with some “standard” temperature ratio obtained from a simultaneous solution of the cosmological recombination kinetics and energy equations being taken as the initial (unperturbed) one. Comparatively small (A = ± 0.01), fast (σ = 17) perturbations are shown to give rise to distinct narrow absorption (for A > 0) or emission (for A 0) or increase (for A < 0) in intensity with increasing wavelength.
- Published
- 2009
16. Search for spatial and spectral fluctuations of cosmic microwave background radiation with the ratan-600 radio telescope. The 2001–2006 observations
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I. V. Gosachinskij, A. P. Wenger, V. K. Dubrovich, and G. N. Il’in
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Physics ,Radio telescope ,Wavelength ,Angular frequency ,Amplitude ,Celestial pole ,Cosmic microwave background ,Astronomy and Astrophysics ,Astrophysics ,Antenna (radio) ,Instrumentation ,Spectral line - Abstract
We report some of the results of the search for narrow-band spatial and spectral fluctuations of cosmic microwave background at the wavelength of 6.2 cmperformed with the RATAN-600 radio telescope in 2001–2006 in two 35′ × 7′ strips on the sky in the vicinity of the North Celestial Pole. We find the spectra of spatial fluctuations in the 12 MHz radio-frequency band and in the interval of spatial periods from 4′ to 16′ to exhibit power-law rises with exponents reaching −2.0±0.5, with a periodicity of 2–3 MHz. We also find two narrow-band (in terms of angular frequency) features at 4870.4 and 4871.5 MHz with the corresponding fluctuation amplitudes of 5±0.5 mK in terms of antenna temperature in the vicinity of angular periods of about 5′ with the frequency bandwidths of about 600 kHz. Standard tests performed using the spectra of the half-sum and half-difference of two groups of observations randomly drawn from a total sample of 23 records of the March 2002 observing set confirm the reality of the features of the angular spectrumof fluctuations mentioned above and so does the comparison with the spectra of cold matched load connected to the receiver input instead of the antenna. However, the nature of the features found remains unclear. Our attempt to link this radiation to rotational transitions 2Π1/2, J = 5/2 of the CH molecule, which has one of the components of its multiplet located inside the frequency interval of interest considered failed.
- Published
- 2008
17. Primordial hydrogen recombination dynamics with recoil upon scattering in the Ly-α line
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S. I. Grachev and V. K. Dubrovich
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Physics ,Scattering ,Cosmic microwave background ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Heavy traffic approximation ,Redshift ,Spectral line ,Recoil ,Space and Planetary Science ,Ionization ,Radiative transfer ,Atomic physics - Abstract
It is shown that taking into account a recoil for radiation scattering in the Ly-alpha line can lead to a noticable acceleration of primordial hydrogen recombination. Thus for LambdaCDM model a decrease of ionization degree exceeds 1% for redshifts z in a range 800 - 1050 achieving approximately 1.3% at z=900. Corresponding corrections to the cosmic microwave background power spectra can achieve 1.1% for TT spectra and 1.7% for EE ones. Radiative transfer in these calculations was treated in a quasistationary approximation. Numerical solutions are also obtained in diffusion approximation for a nonstationary problem of Ly-alpha line radiative transfer under partial frequency redistribution with a recoil. An evolution of a local line profile is traced to as well as an evolution of a relative number of uncompensated transitions from 2p state down to 1s one. It is shown that taking into account nonstationarity of Ly-alpha line radiative transfer can lead to an additional acceleration of primordial hydrogen recombination.
- Published
- 2008
18. A new spectrum analyzer for radio astronomical studies with the radio telescope RATAN-600
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A. S. Morozov, G. N. Il’in, S. V. Logvinenko, A. P. Venger, and V. K. Dubrovich
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Physics ,Spectrum analyzer ,business.industry ,Astrophysics::High Energy Astrophysical Phenomena ,Astronomy ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Radio telescope ,symbols.namesake ,Fourier transform ,Optics ,Very-long-baseline interferometry ,symbols ,business ,Instrumentation - Abstract
The spectral measuring facility with a new Fourier analyzer for use with the radio telescope RATAN-600 is described and its experimental data are reported.
- Published
- 2008
19. Quantum peculiarities of the primordial hydrogen recombination
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V. K. Dubrovich
- Subjects
Physics ,Photon ,Hydrogen ,Cosmic microwave background ,chemistry.chemical_element ,Astronomy and Astrophysics ,Discrete dipole approximation ,chemistry ,Deuterium ,Space and Planetary Science ,Excited state ,Physics::Atomic Physics ,Atomic physics ,Quantum ,Helium - Abstract
Some problems of the two-photon decay of highly excited atomic hydrogen and helium levels are considered. The necessary accuracy of calculating the transition probabilities is shown to require abandoning the purely dipole approximation in the theory of atomic hydrogen radiation. The range of applicability of the perturbation theory to this process is discussed. We suggest a new mechanism of the Lyman photon redistribution due to very close locations of the 20P and 19P levels in the hydrogen and deuterium atoms, respectively (hydrogen-deuterium resonance).
- Published
- 2007
20. CMB recombination lines of hydrogen: The differential spectrum
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V. K. Dubrovich and S. I. Grachev
- Subjects
Physics ,Hydrogen ,Cosmic microwave background ,Cosmic background radiation ,chemistry.chemical_element ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Hydrogen atom ,Molecular physics ,Wavelength ,Superposition principle ,chemistry ,Space and Planetary Science ,Distortion ,Recombination - Abstract
We have calculated the distortions of the cosmic microwave background (CMB) spectrum in the wavelength range 2–50 cm due to the superposition of the CMB hydrogen recombination radiation in subordinate lines. The level populations were determined by numerically solving the equation of recombination kinetics together with the statistical equilibrium equations for a 60-level model hydrogen atom. The relative distortions are ≈10−7–10−6, with their wavelength dependence having a low-contrast, wavy pattern. However, the contrast increases severalfold and becomes pronounced when passing to the differential distortion spectrum. We study the dependence of the distortions on cosmological parameters.
- Published
- 2004
21. Hydrogen absorption lines in the cosmic microwave background spectrum
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N. N. Shakhvorostova and V. K. Dubrovich
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Physics ,Hydrogen ,Cosmic microwave background ,Cosmic background radiation ,chemistry.chemical_element ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Spectral line ,Redshift ,Dipole ,chemistry ,Space and Planetary Science ,Observational cosmology ,Physics::Atomic Physics ,Atomic physics ,Recombination - Abstract
We have calculated the intensities of the subordinate hydrogen lines formed during the recombination epoch at redshifts 800≲z≲1600. We show that an allowance for the angular momentum splitting of hydrogen atomic energy levels and the dipole transition selection rules can reveal absorption features in the cosmic microwave background recombination spectrum in the submillimeter wavelength range.
- Published
- 2004
22. Magnetic Monopoles in the Early Universe: Pair Production
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N. A. Sushko and V. K. Dubrovich
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Physics ,Particle physics ,Pair production ,Quantum electrodynamics ,media_common.quotation_subject ,Magnetic monopole ,Coulomb ,Particle ,Electron temperature ,Astronomy and Astrophysics ,Universe ,media_common - Abstract
Magnetic monopoles and antimonopoles with masses M=1016 Gev and charges q=68.5e in the early universe are considered. Pair production may occur as a result of their Coulomb interaction. Some conditions for formation of such pairs are discussed. In particular, numerical simulations of three particle collisions are carried out. Probabilities for pair production are found in terms of the N-body problem.
- Published
- 2003
23. [Untitled]
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S. I. Grachev, V. K. Dubrovich, and N. N. Shakhvorostova
- Subjects
Physics ,Structure formation ,Scattering ,Cosmic microwave background ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Polarization (waves) ,Cosmology ,symbols.namesake ,symbols ,Rayleigh scattering ,Anisotropy ,Microwave - Abstract
The work is devoted to the investigations of possible observational manifestations of protoobjects related to the “dark ages” epoch (10 < z < 1000), before formation of self-luminous galaxies and stars. These objects can distort the cosmic microwave background. Formation of these objects is described in the “pancake theory” and in the model of “hierarchic clustering.” According to these theories we may consider these protoobjects as flat layers. We consider both Thomson (with Rayleigh phase matrix) and resonance (for complete frequency redistribution) scattering of cosmic microwave background radiation by a moving flat layer. The resulting anisotropy and polarization of cosmic microwave radiation are calculated for a wide range of layer optical thickness (from an optically thin layer to an optically thick one). Analytical solutions are also obtained for the case of an optically thin layer and are compared with the numerical ones.
- Published
- 2003
24. Search for spatial and spectral fluctuations of the cosmic microwave background radiation using the RATAN-600 radio telescope
- Author
-
V. K. Dubrovich, G. N. Il’in, V. A. Prozorov, S. R. Zhelenkov, and I. V. Gosachinskij
- Subjects
Physics ,Frequency band ,Cosmic microwave background ,Astronomy ,Rotational transition ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Radio telescope ,Celestial pole ,Space and Planetary Science ,Observational cosmology ,Astrophysics::Galaxy Astrophysics ,Microwave ,Background radiation - Abstract
We report the results of a search for spatial and spectral fluctuations of the cosmic microwave background in the region of the North celestial pole carried out at 6.2 cm using the RATAN-600 radio telescope in 1999–2000. The spatial spectrum is flat and has no features exceeding ΔT/T =10−3 in a ∼1 MHz frequency band for spatial periods from 0.5′ to 16′. If this estimate is adopted as an upper limit for emission associated with the first rotational transition of primordial LiH at z=90.7, we obtain an upper limit for the LiH abundance of about 3×10−14 for protocluster masses of about 1013M⊙.
- Published
- 2002
25. Formation mechanisms of 'Negative'-intensity spots in the cosmic microwave background radiation and distant objects
- Author
-
V. K. Dubrovich
- Subjects
Physics ,Wavelength ,Space and Planetary Science ,Thomson scattering ,Magnitude (astronomy) ,Cosmic microwave background ,Bremsstrahlung ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Electron ,Redshift ,Radio spectrum - Abstract
We consider the formation mechanisms of “negative”-intensity spots in the radio band for various astrophysical conditions. For wavelengths λ
- Published
- 2001
26. Spectral-spatial fluctuations of the relic radiation—a new class of objects in the universe
- Author
-
V. K. Dubrovich
- Subjects
Physics ,Cold dark matter ,Hot dark matter ,Dark matter ,Astronomy ,Steady State theory ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Cosmology ,Redshift ,De Sitter universe ,Instrumentation ,Background radiation - Abstract
In this work a short review of the main ideas and problems connected with studies of post-recombinational stage of the Universe evolution in the range of redshifts zinvestigate from 1400 to 5 is given. It is shown that the main role in forming observational effects must play the primordial molecules scattering the background radiation in the protogalaxies and protostars moving with pecular velocities. This gives us a possibility to in principle, fully the initial large-scale distribution of matter in the Universe and to determine the primordial chemical abundance. Moreover, detailed study of predicted effects should give a unique information about the presence and physical parameters of unstable dark matter.
- Published
- 1994
27. Propagation of the burst of radiation in expanding and recombining Universe: Thomson scattering
- Author
-
S. I. Grachev and V. K. Dubrovich
- Subjects
Physics ,Photon ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,Opacity ,Thomson scattering ,Scattering ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Polarization (waves) ,Redshift ,symbols.namesake ,Space and Planetary Science ,symbols ,Rayleigh scattering ,Radiant intensity ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
Within the framework of a flat cosmological model a propagation of an instantaneous burst of nonpolarized isotropic radiation is considered from the moment of its beginning at some initial redshift z0 to the moment of its registration now (at z=0). Thomson (Rayleigh) scattering by free electrons is considered as the only source of opacity. Spatial distributions of the mean (over directions) radiation intensity are calculated as well as angular distributions of radiation intensity and polarization at some different distances from the center of the burst. It is shown that for redshifts z0 large enough (z0 > 1400) the profile of the mean intensity normalized to the total number of photons emitted during the burst weakly depends on initial conditions (say the moment z0 of the burst, the width and shape of initial radiation distribution in space). As regards angular distributions of intensity and polarization they turn to be rather narrow (3 - 5 arcmin) while polarization can reach 70%. On the average an expected polarization can be about 15%., 14 pages, 7 figures
- Published
- 2010
- Full Text
- View/download PDF
28. Two-photon decays of highly excited states in hydrogen
- Author
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V. K. Dubrovich, Leonti Labzowsky, Andrey V. Volotka, Günter Plunien, and D. Solovyev
- Subjects
Physics ,SIMPLE (dark matter experiment) ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,Hydrogen ,Atomic Physics (physics.atom-ph) ,chemistry.chemical_element ,FOS: Physical sciences ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Physics - Atomic Physics ,Two-photon excitation microscopy ,chemistry ,Excited state ,Principal quantum number ,Limit (mathematics) ,Physics::Atomic Physics ,Atomic physics ,Astrophysics - Cosmology and Nongalactic Astrophysics ,Physics - Optics ,Optics (physics.optics) - Abstract
The relativistic and nonrelativistic approaches for the calculations of the two-photon decay rates of highly excited states in hydrogen are compared. The dependence on the principal quantum number (n) of the ns, nd, and np initial states is investigated up to n = 100 for the nonresonant emissions. For the ns states together with the main E1E1 channel the contributions of higher multipoles (M1M1, E2E2, E1M2) are considered. For the np states the E1M1 and E1E2 channels are evaluated. Moreover, the simple analytical formula for the E1M1 decay is derived in the nonrelativistic limit., Comment: 10 pages, 3 tables
- Published
- 2010
- Full Text
- View/download PDF
29. Hydrogen recombination in an expanding universe
- Author
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V. K. Dubrovich and S. I. Grachev
- Subjects
Physics ,Hydrogen ,chemistry ,chemistry.chemical_element ,Astronomy and Astrophysics ,Astrophysics ,Recombination ,Metric expansion of space - Published
- 1992
30. Chemistry of heavy elements in the Dark Ages
- Author
-
C. Winteler, Patrick Vonlanthen, V. K. Dubrovich, M. Signore, Thomas Rauscher, D. Puy, Groupe de Recherches Autrichiennes et Allemandes. UHB (GRAAL), MEN : JE2314-Université de Rennes 2 (UR2), University of Basel (Unibas), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), and Special Astrophysical Observatory, St Petersburg Branch
- Subjects
Physics ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,media_common.quotation_subject ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Universe ,Chemical species ,Space and Planetary Science ,Nucleosynthesis ,Dark Ages ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,Reionization ,Relative species abundance ,Order of magnitude ,Recombination ,media_common ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
Primordial molecules were formed during the Dark Ages, i.e. the time between recombination and reionization in the early Universe. The purpose of this article is to analyze the formation of primordial molecules based on heavy elements during the Dark Ages, with elemental abundances taken from different nucleosynthesis models. We present calculations of the full non-linear equation set governing the primordial chemistry. We consider the evolution of 45 chemical species and use an implicit multistep method of variable order of precision with an adaptive stepsize control. We find that the most abundant Dark Ages molecules based on heavy elements are CH and OH. Non-standard nucleosynthesis can lead to higher heavy element abundances while still satisfying the observed primordial light abundances. In that case, we show that the abundances of molecular species based on C, N, O and F can be enhanced by two orders of magnitude compared to the standard case, leading to a CH relative abundance higher than that of HD+ or H2D+., Comment: 14 pages, accepted by Astronomy and Astrophysics
- Published
- 2009
31. Molecular fluorine chemistry in the early Universe
- Author
-
Patrick Vonlanthen, Anton Lipovka, Dahbia Talbi, V. K. Dubrovich, Denis Puy, Groupe de Recherche en Astronomie et Astrophysique du Languedoc (GRAAL), and Université Montpellier 2 - Sciences et Techniques (UM2)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
media_common.quotation_subject ,Cosmic microwave background ,chemistry.chemical_element ,FOS: Physical sciences ,Astrophysics ,7. Clean energy ,01 natural sciences ,Big Bang nucleosynthesis ,0103 physical sciences ,Emission spectrum ,010306 general physics ,010303 astronomy & astrophysics ,media_common ,Physics ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,Astrophysics (astro-ph) ,Astronomy and Astrophysics ,Diatomic molecule ,Universe ,Redshift ,3. Good health ,chemistry ,13. Climate action ,Space and Planetary Science ,Fluorine ,Lithium - Abstract
Some models of Big Bang nucleosynthesis suggest that very high baryon density regions were formed in the early Universe, and generated the production of heavy elements other than lithium such as fluorine F. We present a comprehensive chemistry of fluorine in the post-recombination epoch. Calculation of F, F- and HF abundances, as a function of redshift z, are carried out. The main result is that the chemical conditions in the early Universe can lead to the formation of HF. The final abundance of the diatomic molecule HF is predicted to be close to 3.75 10(-17) when the initial abundance of neutral fluorine F is 10(-15). These results indicate that molecules of fluorine HF were already present during the dark age. This could have implications on the evolution of proto-objects and on the anisotropies of cosmic microwave background radiation. Hydride of fluorine HF may affect enhancement of the emission line intensity from the proto-objects and could produce spectral-spatial fluctuations., Comment: Accepted in Astronomy and Astrophysics, 7 pages, 2 figures
- Published
- 2007
- Full Text
- View/download PDF
32. Primordial pairing and binding of superheavy charge particles in the early Universe
- Author
-
M. Yu. Khlopov and V. K. Dubrovich
- Subjects
Physics ,Antiparticle ,Charge conservation ,Annihilation ,Physics and Astronomy (miscellaneous) ,Field (physics) ,media_common.quotation_subject ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Charge (physics) ,Astrophysics ,Charged particle ,Universe ,Nuclear physics ,Particle ,media_common - Abstract
Primordial superheavy particles, considered as the source of Ultra High Energy Cosmic Rays (UHECR) and produced in local processes in the early Universe, should bear some strictly or approximately conserved charge to be sufficiently stable to survive to the present time. Charge conservation makes them to be produced in pairs, and the estimated separation of particle and antiparticle in such pair is shown to be in some cases much smaller than the average separation determined by the averaged number density of considered particles. If the new U(1) charge is the source of a long range field similar to electromagnetic field, the particle and antiparticle, possessing that charge, can form primordial bound system with annihilation timescale, which can satisfy the conditions, assumed for this type of UHECR sources. These conditions severely constrain the possible properties of considered particles., Comment: Latex, 4 pages. The final version to appear in Pis'ma ZhETF (the conditions for the primordial binding are specified, some refs added)
- Published
- 2002
- Full Text
- View/download PDF
33. Molecules in the Shell of Quasars 1556+3517 and 0840+3633
- Author
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V. K. Dubrovich and A. A. Lipovka
- Subjects
Physics ,Molecular cloud ,Ionization ,Optical depth (astrophysics) ,Quasar ,Emission spectrum ,Astrophysics ,Absorption (chemistry) ,Spectral line ,Line (formation) - Abstract
A new class of low- ionization BAL quasars (Becker et al. (1997)), represented by QSO 1556+3517, 0840+3633 and 0059-2735, is considered. Their optical spectra are completely dominated by absorption features, whereas emission lines are weak or absent. The possibility to explain these exclusive features of their spectra by the existence of molecular shells, responsible for the absorption is discussed. In particular, it is suggested that a line at λ= 2063A, attributed to CrII, is a line of the Cameron band a3 II i X 1Σ+ of the CO molecule. Estimation of the expected optical depth in rotational radio lines of this molecule is made. It is suggested to carry out radio observations of quasars 1556+3517 and 0840+3633 to check the molecular hypothesis.
- Published
- 1999
34. Supermassive primordial black holes at high redshifts.
- Author
-
Dubrovich, V. K., Eroshenko, Yu. N., and Grachev, S. I.
- Subjects
SUPERMASSIVE black holes ,BLACK holes ,RADIATION absorption ,RADIO telescopes ,SHOCK waves - Abstract
We consider some properties and possible observational manifestations of the very heavy primordial black holes (PBHs), with masses ∼ (1 0 9 − 1 0 1 0) M ⊙ . These black holes should be surrounded by the dense dark matter and baryonic halos even at early cosmological epochs. There are mechanisms as for radiation emission in the centers due to accretion and for deep absorption of relic radiation at the periphery of the halos. We calculate the absorption profile in the 21 cm line of atomic hydrogen by solving the equations of radiation transfer through the baryonic halo around a PBH. The calculations show that a spherical absorbing layer appears around the object, which can be observed with radio telescopes. Also, at some epochs, shock waves may form at the periphery of the objects. The accelerated charged particles can radiate in radio frequency band, so it is possible that these objects can explain the recently discovered radio circles. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
35. Investigation of the electromagnetically induced transparency in the era of cosmological hydrogen recombination
- Author
-
D. Solovyev, G. Plunien, and V. K. Dubrovich
- Subjects
Physics ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,Photon ,Field (physics) ,Atomic Physics (physics.atom-ph) ,Electromagnetically induced transparency ,Cosmic microwave background ,FOS: Physical sciences ,Hydrogen atom ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Physics - Atomic Physics ,Quantum electrodynamics ,Optical depth (astrophysics) ,Atom ,Recombination ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
Investigation of the cosmic microwave background formation processes is one of the most actual problem at present time. In this paper we analyze the response of the hydrogen atom to the external photon fields. Field characteristics are defined via conditions corresponding to the recombination era of universe. Approximation of three-level atom is used to describe the "atom - fields" interaction. It is found that the phenomena of the electromagnetically induced transparancy takes place in this case. Consideration of EIT phenomena makes it necessary to update astrophysical description of the processes of the cosmic microwave background formation and, in particular, Sobolev escape probability. Additional terms to the optical depth in definition of Sobolev escape probability on the level about 1% are found., 16 pages, 4 figures, 1 Table
- Published
- 2012
36. Yurii Nikolaevich Pariiskii (on his 80th birthday)
- Author
-
Adelina V Temirova, A. B. Berlin, G A Pinchuk, Yurii Yu. Balega, Nikolai S. Kardashev, M. G. Mingaliev, V M Bogod, I V Kostyuk, P A Fridman, Rustam D. Dagkesamanskii, V K Dubrovich, and I V Gosachinskii
- Subjects
General Physics and Astronomy - Published
- 2012
37. Gamow memorial conference St. Petersburg session
- Author
-
Yu. N. Parijskij and V. K. Dubrovich
- Subjects
Physics ,St petersburg ,Library science ,Astronomy and Astrophysics ,Session (computer science) ,Instrumentation - Abstract
(2000). Gamow memorial conference St. Petersburg session. Astronomical & Astrophysical Transactions: Vol. 19, No. 3-4, pp. 201-202.
- Published
- 2000
38. Quantum electrodynamics of non-demolition detection of single microwave photon by superconducting qubit array.
- Author
-
Navez, P., Balanov, A. G., Savel'ev, S. E., and Zagoskin, A. M.
- Subjects
MICROWAVES ,PHOTONS ,CAVITY resonators ,QUALITY factor ,RESONATORS ,SUPERCONDUCTING quantum interference devices ,QUANTUM electrodynamics - Abstract
By consistently applying the formalism of quantum electrodynamics, we developed a comprehensive theoretical framework describing the interaction of single microwave photons with an array of superconducting transmon qubits in a waveguide cavity resonator. In particular, we analyze the effects of microwave photons on the array's response to a weak probe signal exciting the resonator. The study reveals that high quality factor cavities provide a better spectral resolution of the response, while cavities with moderate quality factors allow better sensitivity for a single-photon detection. Remarkably, our analysis showed that a single-photon signal can be detected by even a sole qubit in a cavity under the realistic range of system parameters. We also discuss how the quantum properties of the microwave radiation and electrodynamical properties of resonators affect the response of qubits' array. Our results provide an efficient theoretical background for informing the development and design of quantum devices consisting of arrays of qubits, especially for those using a cavity where an explicit expression for the transmission or reflection is required. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
39. Statistical Estimates of the Vapor Content and Atmospheric Optical Thickness from Reanalysis and Radiosounding Data as Applied to Millimeter Telescopes.
- Author
-
Shikhovtsev, A. Yu. and Kovadlo, P. G.
- Abstract
Possibilities of astronomical millimeter and submillimeter observations strongly depend on the precipitable water vapor (PWV), which determines the radiation absorption. The precise estimation of the PWV within large regions is one of key astroclimate problems. In this work, we refine estimates of the PWV for different sites based on processing ERA5 reanalysis and radiosounding data and test the previously suggested technique for correcting PWV values taking into account the characteristic water vapor vertical scale and the relative difference in grid node altitudes. In addition, the spatial distribution of the nighttime atmospheric optical thickness at a wavelength of 3 mm averaged over December–February 2013–2022 was derived for the first time for Russia and the adjacent territory. Our results can serve the basis for selecting an astronomic site for a new large millimeter telescope within the Eurasian Sub-Millimeter and Millimeter Telescope Project. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
40. Astronomical Research at the Mathematics Faculty of St. Petersburg University, I.
- Author
-
Prokopjeva, M. S., Krayani, H. A., and Il'in, V. B.
- Abstract
The development of astronomical research at St. Petersburg University since its foundation is considered. The subjects of works are briefly described and the main achievements of university astronomers in the 18th–19th centuries are highlighted. The most important research carried out at the university in various fields of astronomy in the 20th century are listed. Certain emphasis is made on the mathematical side of the works. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
41. The role of small molecular cations in the chemical flow of the interstellar environments.
- Author
-
González-Sánchez, Lola, Sathyamurthy, N., and Gianturco, Francesco A.
- Abstract
Molecular ions have been ubiquitous in a variety of environments in the interstellar medium, from Circumstellar Envelopes to Dark Molecular Clouds and to Diffuse Clouds. Their role in the multitude of molecular processes which have been found to occur in those environments has been the subject of many studies over the years, so that we have acquired by now a complex body of data on their chemical structures, their possible function within chemical reactions and their most likely paths to formation. In the present work we review a broad range of such molecular ions, focusing exclusively on positive ions involving the smallest and simplest cations which have been either detected or conjectured as present in the interstellar medium (ISM). We therefore consider mainly molecular cations formed with components like H, H
+ , He and He+ , atomic species which are by far the most abundant baryons in the ISM in general. Their likely structures and their roles in a variety of chemical energy flow paths are discussed and presented within the context of their interstellar environments. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
42. Luminescence in Primordial Helium Lines at the Pre-recombination Epoch.
- Author
-
Dubrovich, V. K. and Grachev, S. I.
- Subjects
LUMINESCENCE ,RADIATION absorption ,REDSHIFT ,SPECTRAL lines ,PHOTONS ,ELECTROMAGNETIC radiation - Abstract
The formation of luminescent subordinate He I lines by the absorption of radiation from a source in lines of the main He I series in an expanding Universe is considered. A burst of radiation in continuum is assumed to occur at some instant of time corresponding to redshift
z 0 . This radiation is partially absorbed at differentz <z 0 in lines of the main He I series (different pumping channels) and then is partially converted into radiation in subordinate lines. Ifν is the laboratory transition frequency of some subordinate line emerging at someik z , then at the present epoch its frequency will beν =ν /(1 +ik z ). The quantum yield, i.e., the number of photons emitted in the subordinate line per initial excited atom, has been calculated for differentz (and, consequently, for differentν ). Several pumping channels have been considered. We show that the luminescent lines can be both emission and absorption ones; the same line can be an emission one for one of the pumping channels and an absorption one for another. For example, the 1s2s-1s2p (1S-1P*) line is an emission one for the 1s2-1s2p pumping and an absorption one for the 1s2-1s3p pumping. We show that in the frequency range 30-80 GHz the total quantum yield for the first and second of the above channels can reach +50 and −50%, respectively. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
43. Finite Time Effects in Single and Double Compton Scattering.
- Author
-
Dubrovich, V. K. and Zalialiutdinov, T. A.
- Subjects
COMPTON scattering ,COMPTON effect ,RELATIVISTIC electrodynamics ,QUANTUM electrodynamics ,ELECTRON scattering ,FREE electron lasers - Abstract
The process of Compton scattering by a free electron with subsequent reemission of one or two photons is considered in the assumption of finite interaction time. The corresponding cross sections are obtained in the framework of relativistic quantum electrodynamics using a modified form of fermion propagator with complex transmitted momentum. It is shown that finite time effects can be observable at sufficiently low energies of scattered photons. The proposed method also regularizes arising infrared divergence in the cross section of the double Compton effect. Possible experimental verification of considered theoretical approach is discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
44. Local burst model of CMB temperature fluctuations: Scattering in the resonance lines of primordial hydrogen and helium.
- Author
-
Dubrovich, V. and Grachev, S.
- Subjects
COSMIC background radiation ,RADIATIVE transfer ,THOMSON scattering ,HYDROGEN ,HELIUM - Abstract
The propagation of an instantaneous burst of isotropic radiation from the time of its onset at some redshift z to the time of its detection at the present epoch (at z = 0) is considered within the framework of a flat Universe. The Thomson scattering by free electrons and the scattering in the primordial hydrogen Lα and Lβ lines and in the He I 1s2-1s2p, 1s3p (S-P*) lines are taken into account. It is shown that the relative amplitude of the spectral distortions due to the scattering in these lines at the corresponding frequencies can be a factor of 10−10 greater than the maximum possible amplitude from the scattering in the subordinate hydrogen lines considered previously (Dubrovich and Grachev 2015). In the linear approximation in optical depth, the distortion profiles in the resonance lines turn out to be purely absorption ones and depend neither on the direction nor on the distance to the burst center, in contrast to the profiles in the subordinate lines. The profiles contain jumps at frequencies corresponding to the instant the source (burst) appears at a given redshift z . For example, at z = 5000 the jumps in the hydrogen Lα and Lβ lines lie at frequencies of 493 and 584 GHz, respectively, while in the above two helium lines they lie at frequencies of 855 and 930 GHz at z = 6000. The relative magnitude of the jumps ranges from 10−4 to 3 × 10−3. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
45. A Mobile Full-Revolving Radiometric Complex for Astronomical and Atmospheric Research.
- Author
-
Bolshakov, O. S., Bubnov, G. M., Vdovin, A. V., Vdovin, V. F., Gladishev, V. O., Gunbina, A. A., Dubrovich, V. K., Zemlyanukha, P. M., Kauc, V. L., Krasilnikov, A. M., Lesnov, I. V., Mansfeld, M. A., Mineev, K. V., and Sharandin, E. A.
- Subjects
ANTENNAS (Electronics) ,INTEGRATED optics ,WAVEGUIDES ,RADIOMETERS ,ELECTRONIC data processing - Abstract
A radiometric complex for astronomical and atmospheric research in the 3-mm wavelength range has been developed. The radiometer is assembled according to the modulation scheme with a mechanical obturator based on oversized quasi-optical waveguides. A Cassegrain antenna with 1° far-field pattern at a −3 dB level is used as the antenna system. Calibration is carried out using a built-in noise generator. The receiving system of the radiometer, together with the antenna, is placed on a two-coordinate turntable for observations in a selected region of the celestial sphere. Control, as well as capture and processing of experimental data, are performed remotely using the developed software. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
46. Optical Thickness of the Atmosphere above the Terskol Peak.
- Author
-
Shikhovtsev, A. Yu., Khaikin, V. B., Kovadlo, P. G., and Baron, P.
- Abstract
Estimates of the optical thickness of the atmosphere above the Terskol Peak are presented. The optical thickness is represented as a quantity depending on absorption coefficients determined mainly by water vapor and oxygen. The calculations are carried out under a clear sky without regard to aerosol components. Water vapor variations are considered as the main factor determining the radiation attenuation in the atmosphere in the millimeter and submillimeter spectrum ranges. The average optical thickness of the atmosphere is estimated with the use of the MPM Liebe and MOLIERE models (in the JPL and HITRAN configurations) for frequencies of 100, 150, and 225 GHz. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
47. Primordial black holes and mirror dark matter.
- Author
-
Kitabayashi, Teruyuki
- Subjects
BLACK holes ,DARK matter ,MIRRORS ,BARYONS - Abstract
If mirror matter exists but cannot comprise all of the dark matter (DM) in the universe, we can expect that the additional DM component may only interact with the other sectors gravitationally. One of the natural candidates of a gravitationally interacting component is a primordial black hole (PBH). Therefore, if mirror matter exists but cannot comprise all of the DM in the universe, the existence of PBH may be expected as a candidate of the additional DM component. In this case, the remaining DM components may be PBHs or S U (3) × S U (2) × U (1) singlet particles from PBH. We show constraints on PBH with the mirror DM. Particularly, the initial PBH mass is estimated to be 1 0 1 7 g ≲ M PBH ≲ 1 0 2 3 g , if the DM comprises mirror baryons and PBHs. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
48. Statistical Analysis of the Water Vapor Content in North Caucasus and Crimea.
- Author
-
Shikhovtsev, A. Yu., Khaikin, V. B., Mironov, A. P., and Kovadlo, P. G.
- Abstract
Results of studying the precipitable water vapor content in the atmosphere column for Terskol Peak (the Elbrus region), Kislovodsk city, Nauchny settlement (Crimea), Shaki city (Azerbaijan), and Khunzakh settlement (Dagestan) are presented. The comparative analysis of variations in the precipitable water vapor content estimated by data of measurements at GNSS stations and ERA-5 reanalysis is performed. Using the ERA-5 reanalysis makes it possible to reveal new sites promising for location of millimeter/submillimeter telescopes. With allowance for the comparatively low total cloud cover, Rutul and Agul raions of mountainous Dagestan (Mt. Khorai (3521 m) and Mt. Karakh (2876 m) with surroundings, as well as Mt. Sindaku (2849 m) with surroundings) are most promising sites for the location of the Russian millimeter/submillimeter telescope in North Caucasus. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
49. Direct Measurements of Atmospheric Absorption of Subterahertz Waves in the Northern Caucasus.
- Author
-
Balega, Yu. Yu., Bataev, D. K.-S., Bubnov, G. M., Vdovin, V. F., Zemlyanukha, P. M., Lolaev, A. B., Lesnov, I. V., Marukhno, A. S., Marukhno, N. A., Murtazaev, A. K., Khaykin, V. S., and Khudchenko, A. V.
- Subjects
SOLAR radiation ,ELECTROMAGNETIC wave absorption ,SUBMILLIMETER waves ,SPACE debris ,RADIO interferometers ,RADIO astronomy ,ASTEROIDS - Abstract
The first results of direct expedition measurements of atmospheric absorption of electromagnetic waves in the sub-terahertz frequency range of 0.1–1 THz, carried out in order to select an optimal site from the point of view of the microwave astroclimate for development of an observatory that can become an element of the radio interferometer of the Suffa observatory and, in the future, enter into collaboration with the Event horizon telescope (EHT), are presented in brief. The EHT, presenting an image of the shadow of a black hole, today consists of a dozen antennas located around the globe, and at present has no elements in its network in northern Eurasia. The studies performed may be useful not only for radio astronomy problems, but also for space communications, radar of the Moon, asteroids, and the detection of space debris objects. The first results of direct measurements of propagation of subterahertz waves at the selected sites confirmed the initial hypothesis of the expedition. This hypothesis was formulated on the basis of an analysis of meteorological data, as well as satellite data on atmospheric absorption in other ranges: optics and low-frequency radio bands. It was assumed that the work in the subterahertz frequency range in the eastern part of the northern Caucasus is more promising than in the western Caucasus. The western part is more attractive because today there are a number of observatories already operating, and the installation of one more antenna would have been much easier in terms of the necessary infrastructure and required highly qualified personnel. The hypothesis of the predominance of the eastern part was convincingly confirmed in the completed research by comparing the absorption in the 2- and 3-mm bands from the previously surveyed areas of the Western Caucasus (Terskol peak, Pastukhov mountain, KMO, BTA, RATAN-600 sites, etc.) with those studied during the expedition in 2021 for the Eastern sites on the Mayak (Gunib), Stolovaya, and Shalbuzdag mountains. Even measurements at the highest peak not only in the Western Caucasus, but also in Europe, at Mount Elbrus, carried out as part of this expedition, gave results worse than those in Dagestan and North Ossetia, confirming the futility of further search for a place for an effective subterahertz instrument in the eastern part of the North Caucasus. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
50. Spectral and spatial fluctuations of cosmic microwave background radiation. RATAN-600 radio telescope observations with a Fourier spectral analyzer.
- Author
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Venger, A., Gosachinskij, I., and Dubrovich, V.
- Subjects
METAPHYSICAL cosmology ,COSMIC background radiation ,RADIO astronomy ,SPECTRUM analysis ,HYDROGEN - Abstract
The 'circumpolar survey' technique allowed us to achieve a rather high antenna temperature sensitivity of 0.5 mK at 6 cm on a fixed antenna with a relatively narrow frequency resolution band (600 kHz) and an angular resolution of 45″ × 7′. Starting from 2007 we use a Fourier spectral analyzer with a survey band 10 times broader than that of previous observations. This upgrade allowed us to rapidly perform repeated test observations, which confirmed the power-law nature and the frequency structure of spatial spectra in two strips in the vicinity of the celestial pole in the 4′-16′ interval of angular periods. These observations also showed that the Galactic CH molecular line that was by chance captured in our survey strip (Λ-doubling of rotational transition) has nothing to do with the emission spectra we obtained. The angular pattern of emission in two main lines of Λ-doubling (4847.84 and 4870.12 MHz) is absolutely different, whereas there is practically no maser amplification in the CH line to explain this fact. Our observations also confirm the H110 α line (4874.157 MHz), which forms in the tenuous ionized Galactic hydrogen at such relatively high latitudes. Other features of the spatial spectra also appear to be quite real, although their interpretation remains unclear and requires further studies. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
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