arXiv subjects

V. V. Sokolov

Publications and source records attributed to V. V. Sokolov.

87 records · Page 5Linked to original sources

arXiv1999

Quantum Resonances of Kicked Rotor and SU(q) group

The quantum kicked rotor (QKR) map is embedded into a continuous unitary transformation generated by a time-independent quasi-Hamiltonian. In some vicinity of a quantum resonance of order $q$, we relate the problem to the {\it regular} motion along a circle in a $(q^2-1)$-component inhomogeneous "magnetic" field of a quantum particle with $q$ intrinsic degrees of freedom described by the $SU(q)$ group. This motion is in parallel with the classical phase oscillations near a non-linear resonance.

chao-dyn↗

arXiv1999

BVR_cI_c light curves of GRB970508 optical remnant and magnitudes of underlying host galaxy

The observations with the SAO-RAS 6-m telescope in July-August 1998 show that the GRB970508 optical remnant has varied very little since November 1997. We can conclude that we observe a proper host galaxy without the GRB optical remnant. The fitting results of the light curve of the GRB remnant plus the host galaxy until about 400 days after the primary event are reported here. The best $χ^2$-fits with a power law, for most of the filters used, are not acceptable. Some intrinsic variability of the GRB optical remnant fading is possible, which demands a more complex law presenting the largest multiband homogeneous data set from a single telescope.

astro-ph↗

arXiv1999

Realistic model of correlated disorder and Anderson localization

A conducting 1D chain or 2D film inside (or on the surface of) an insulator is considered. Impurities displace the charges inside the insulator. This results in a long-range fluctuating electric field acting on the conducting line (plane). This field can be modeled by that of randomly distributed electric dipoles. This model provides a random correlated potential with \propto 1/k. In the 1D case such correlations may essentially influence the localization length but do not destroy Anderson localization.

cond-mat↗

arXiv1998

Properties of the host galaxy of the gamma-ray burst 970508 and local star-forming galaxies

Late-time observations of GRB970508 with the SAO-RAS 6-m telescope in July-August 1998 show that the optical transient (OT) varies very little since November 1997. Here we report the $BVR_cI_c$ light-curves behaviour up to 470 days from the GRB occurence with independent $BVR_cI_c$ power-law fits. After ~=200 days the power-law decay has ceased and the OT contamination to the host galaxy flux is already less than the observational errors of the brightness estimates. Spectral energy distribution for the host galaxy alone (without OT) and comparison of its broad-band spectrum to the average continuum spectra of different Hubble types galaxies are shown. The best fits to the BVR_cI_c spectral energy distribution of the GRB host with local starburst galaxies are found for the blue compact S0 dwarf galaxy NGC1510, the Scd starburst HII galaxy NGC7793 and the blue compact galaxy Mrk 1267. Position of the host galaxy in the M_B vs. log(D_25) diagram for local late-type LEDA galaxies allows us to attribute GRB970508 host galaxy to the blue compact galaxies.

astro-ph↗

arXiv1998

BVR_cI_c light curves of GRB970508 optical remnant and colors of underlying host galaxy

Optical observations of the GRB 970508 optical remnant were continued with the 6-m telescope of SAO RAS in standard BVRcIc bands in Oct.-Dec.1997 and in Jan. 1998. The results of the photometry of GRB970508 remnant and of three nearby galaxies are presented. The BVRcIc light curves of the GRB970508 remnant may be described by a power law plus a constant F(t)=F_0(t-t_0)^α+C. In In parameters determination of the faint host galaxy we used the results of our BVRcIc photometry of May-August, 1997, the data of recent observations Keck-II and WHT telescopes and also the data of Rc and B bands photometry obtained by other authors based on our secondary standards. The level-off from the initial power-law decline seen in the first months after the burst observed in all bands. The effect is the most strong in Ic band. The best χ^2-fits for Fo, α, C parameters of the data in each of 4 bands point to the presence of a faint constant source with Ic=24.13\pm0.28, Rc = 25.55\pm0.19, V=25.80\pm 0.14, B=26.68\pm 0.14. The average αof light curve power law is -1.23\pm0.04. The optical remnant has the power law F_νν^βspectrum with spectral slope = -1.10\pm0.08 and does not change after optical curve maximum. BVRcIc spectrum together with an absolute magnitude of the constant component M_B_rest=-17.5\pm0.3 and the limit of the linear size of underlying host galaxy d<1.1 kpc, calculated for z=0.835,H_0=75km s^-1 Mpc^-1, q_0=0.5, correspond to a host galaxy, such as a starburst dwarf, red starburst dwarf, irregular dwarf, HII galaxy, or blue compact dwarf galaxy. All these types of dwarf galaxies show evidence of starburst or post starburst activity. Galaxy G2 has a spectrum similar to one of the host GRB galaxy and lies at the projected distance of ~20 kpc from GRB.

astro-ph↗

arXiv1998

BVRcIc photometry of GRB970508 optical remnant: May-August, 1997

We present the results of photometric observations of the variable optical source associated to the remnant of the gamma-ray burst GRB970508 performed at SAO RAS (Russia) from May to August 1997. The observations were carried out with the standard (Johnson-Kron-Cousins) photometric BVRcIc system using the 1-meter and 6-meter telescopes. The brightness of the optical source increased from Rc=21.19 (May 9.75 UT) to Rc=19.70 (May 10.77 UT), whereupon it was decaying in all the four BVRcIc bands during about one month after the burst. Between the 3rd and the 6th night after the GRB970508 event, the flux decrease of the optical source follows an exponential law in all the four bands. In that period the broad-band spectrum of the object does not change and can be approximately described by a power with index -1.1. The subsequent observations showed a reduction of the source brightness decrease rate in all bands. The source flux decay after the maximum in the Rc band is well described by a single power-law with index -1.171 for the whole set of observations during 86 days. In the other bands the decay seems to slow down from the 31th day onwards. In particular, in the Ic band the source magnitude is about 23.1 from the 36th day after the GRB to the end of the observations (August 4, 1997).

astro-ph↗

arXiv1997

BVRI observations of PSR B0656+14 with the 6-meter telescope

We observed the middle-aged radio pulsar 0656+14 with a CCD detector at the 6-m telescope. Broadband BVRI images show the following magnitudes of the pulsar counterpart: B = 24.85 (+0.19, -0.16), V = 24.90 (+0.16, -0.14), R = 24.52 (+0.12, -0.11), I = 23.81 (+0.27, -0.21). We fitted the UV-optical (space + ground-based) data with a two-component model which combines a power law (non-thermal component) with a thermal spectrum emitted by the neutron star surface. The power law component, with the energy power-law index α=1.5 (+1.1,-1.2), dominates in the observed range. Constraints on the thermal component correspond to the Rayleigh-Jeans parameter G\equiv T_6(R_{10}/d_{500})^2=4.1 (+2.1, -4.1), where $T=10^6T_6$ K is the brightness temperature, R_\infty = 10 R_{10}$ km is the neutron star radius as seen by a distant observer, and $d=500 d_{500}$ pc is the distance. The shape of the optical-UV spectrum of PSR 0656+14 differs considerably from those observed from other pulsars: the middle-aged Geminga and young Crab, Vela.

astro-ph↗

arXiv1997

Multicolor photometry of the GRB970508 optical remnant

We report results of follow-up multicolor photometry of the optical variable source that is a probable remnant of the gamma-ray burst GRB970508 discovered by the BeppoSAX satellite (IAUC 6649). Observations were carried out in Johnson-Kron-Cousins $ BVR_cI_c system with the 1-m and 6-m telescopes of SAO RAS. Between the 2nd and the 5th day after the burst a fading of the remnant is well fitted with an exponential law in all four bands. During this period the `broadband spectrum' of the object was unchanged and can be approximated by a power-law, F_ν\proptoν^{-1.1}. After the 5th day the decline of brightness is slowed down. In the R_c band until the 32nd day, the light curve can be described by a power-law relation, F_t \propto t^{-1.2}.

astro-ph↗

arXiv1997

Deep photometric study of the region of the gamma-ray burst localization of June 13, 1979

In the framework of the hypothesis on potential sources of some gamma-ray bursts being single compact objects of neutron star type with finite surface temperature in the vicinity of the Sun a method of search in the optical range for a corresponding candidate in the region of a powerful short burst localization is considered. The localization region of the GRB790613 event is studied in the B, V and R filters. B-V and V-R colors of 196 objects with a S/N > 4 are measured up to the average practical photometric limit B < 25.7, V < 25.7 and R < 25.6 for the whole obtained mosaic of CCD images. No blue objects with B-V < 0 and V-R <0 were found up to B \approx 25.2, which can be interpreted as the absence of a compact object with a temperature > 1.5 10^{5}, K in this direction up to a distance \approx 40, pc. A probable common upper limit to the temperature of the supposed compact objects in the vicinity of the Sun is indicated based on the accumulated optical and X--ray data. The study of blue (B-V < 0) objects in the smallest (in the northern sky) gamma-ray box GRB790613, in view of the results of the search for point-like sources in the soft X--ray in the localization regions of bright gamma-ray bursts, does not exclude the existence of such ``cold'' (<= 10^{5} K) objects, which could give an essential contribution to the observed density of hidden matter close to the Sun and some of them could be related with the closest sources of gamma-ray bursts. Several interesting objects were also found in (or near) the localization region of the GRB790613 event.

astro-ph↗

arXiv1997

A Simple Mode on a Highly Excited Background: Collective Strength and Damping in the Continuum

Simple states, such as isobaric analog states or giant resonances, embedded into continuum are typical for mesoscopic many-body quantum systems. Due to the coupling to compound states in the same energy range, a simple mode acquires a damping width ("internal" dynamics). When studied experimentally with the aid of various reactions, such states reveal enhanced cross sections in specific channels at corresponding resonance energies ("external" dynamics which include direct decay of a simple mode and decays of intrinsic compound states through their own channels). We consider the interplay between internal and external dynamics using a general formalism of the effective nonhermitian hamiltonian and looking at the situation both from "inside" (strength functions and spreading widths) and from "outside" (S-matrix, cross sections and delay times). The restoration of isospin purity and disappearance of the collective strength of giant resonances at high excitation energy are discussed as important particular manifestations of this complex interplay.

nucl-th↗

arXiv1997

Interfering Doorway States and Giant Resonances. I: Resonance Spectrum and Multipole Strengths

A phenomenological schematic model of multipole giant resonances (GR) is considered which treats the external interaction via common decay channels on the same footing as the coherent part of the internal residual interaction. The damping due to the coupling to the sea of complicated states is neglected. As a result, the formation of GR is governed by the interplay and competition of two kinds of collectivity, the internal and the external one. The mixing of the doorway components of a GR due to the external interaction influences significantly their multipole strengths, widths and positions in energy. In particular, a narrow resonance state with an appreciable multipole strength is formed when the doorway components strongly overlap.

nucl-th↗

arXiv1997

Interfering Doorway States and Giant Resonances. II: Transition Strengths

The mixing of the doorway components of a giant resonance (GR) due to the interaction via common decay channels influences significantly the distribution of the multipole strength and the energy spectrum of the decay products of the GR. The concept of the partial widths of a GR becomes ambiguous when the mixing is strong. In this case, the partial widths determined in terms of the $K$- and $S$-matrices must be distinguished. The photoemission turns out to be most sensitive to the overlapping of the doorway states. At high excitation energies, the interference between the doorway states leads to a restructuring towards lower energies and apparent quenching of the dipole strength.

nucl-th↗

arXiv1997

Dynamical theory of quantum chaos or hidden random matrix ensemble?

In a recent Letter [Phys.Rev.Lett., 77,4536 (1996), chao-dyn/9609014] Altland and Zirnbauer claim that they rigorously proved the complete analogy between a (classically chaotic) dynamical system and disordered (random) solids. The purpose of this Comment is to show that, in fact, their theory fails to take into account dynamical features which go beyond standard random matrix theory description.

cond-mat.dis-nn↗

arXiv1997

Optical observations of nearby isolated pulsar PSR 0656+14 at the 6-meter telescope

The data of BVR observations of the middle-aged radio pulsar PSR 0656+14 on January, 20/21 at the BTA (6-m) are presented. The brightness is determined in Cousins B filter B ~~25.1 with lambda_eff=4448A in adjacent for HST F130LP long-pass filter of a star-like object, coinsiding with the position of VLA radio source. Relatively large observed V and R fluxes (<~3sigma or > 10E-30 ergs cm^-2 s^-2 Hz^-1) can witness a non-thermal nature of optical radiation of this pulsar up to lambda~~6600A. Most probably in the UV-optical (BVR) spectral range a power-law spectrum is superimposed on the thermal-like radiation of the entire neutron star surface what can be related to a mechanism itself of the pulsar activity.

astro-ph↗

arXiv1995

Time Delay Correlations in Chaotic Scattering: Random Matrix Approach

We study the correlations of time delays in a model of chaotic resonance scattering based on the random matrix approach. Analytical formulae which are valid for arbitrary number of open channels and arbitrary coupling strength between resonances and channels are obtained by the supersymmetry method. We demonstrate that the time delay correlation function, though being not a Lorentzian, is characterized, similar to that of the scattering matrix, by the gap between the cloud of complex poles of the $S$-matrix and the real energy axis.

chao-dyn↗