Theory of transient spectroscopy of multiple quantum well structures

A theory of the transient spectroscopy of quantum well (QW) structures under a large applied bias is presented. An analytical model of the initial part of the transient current is proposed. The time constant of the transient current depends not only on the emission rate from the QWs, as is usually assumed, but also on the subsequent carrier transport across QWs. Numerical simulation was used to confirm the validity of the proposed model, and to study the transient current on a larger time scale. It is shown that the transient current is influenced by the nonuniform distribution of the electric field and related effects, which results in a step-like behavior of the current. A procedure of extraction of the QW emission time from the transient spectroscopy experiments is suggested.Comment: 5 pages, 4 figures, to be published in J. Appl. Phy

Property (T)(T) for noncommutative universal lattices

We establish a new spectral criterion for Kazhdan's property $(T)$ which is applicable to a large class of discrete groups defined by generators and relations. As the main application, we prove property $(T)$ for the groups $EL_n(R)$, where $n\geq 3$ and $R$ is an arbitrary finitely generated associative ring. We also strengthen some of the results on property $(T)$ for Kac-Moody groups from a paper of Dymara and Januszkiewicz (Invent. Math 150 (2002)).Comment: 47 pages; final versio

The calculation of the relaxation processes during dehydration of fish

The methods of study of relaxation processes that are applicable during fish dehydration considering the influence of the chemical composition, geometric size of the processing object and regime parameters of the dehydration processes are developed in this work. The usage of the numerical methods of calculation on the basis of solution of the second-order differential equation with boundary conditions of the third kind allow with sufficient accuracy for engineering practice modeling the different conditions of the dehydration process conducting with periodic restoration of hydraulic conductivity properties of the objects of dehydration. The proposed calculation methods applicable to dehydration processes. Which consists of a continuous initial period and the combined periods of drying fish and relaxation dehydration facility. During the relaxation is provided an exposure to a drying agent for dewatering for a certain time. During relaxation stops the supply of electric power to the heating elements. Reduces the rate of circulation of the drying agent. In the drying installation is supplied with air of lower temperature and higher relative humidity than the drying agent. In drier conditions are created that constrain external mass transfer and promotes relaxation of moisture, that is, to its redistribution in the thickness of the fish. During the relaxation of the moisture is gradually shifting from the central layers where dehydration has not yet come to the dehydrated surface layers. The appearance of moisture inside the dehydrated surface area leads to putting up and expansion of capillaries. At the next interval change product moisture re-enters the dehydration process, the high conductive properties throughout its volume

Stable monopole and dyon solutions in the Einstein-Yang-Mills theory in asymptotically anti-de Sitter Space

A continuum of new monopole and dyon solutions in the Einstein-Yang-Mills theory in asymptotically anti-de Sitter space are found. They are regular everywhere and specified with their mass, and non-Abelian electric and magnetic charges. A class of monopole solutions which have no node in non-Abelian magnetic fields are shown to be stable against spherically symmetric linear perturbations.Comment: 9 pages with 5 figures. Revised version. To appear in Phys Rev Let

Detection of Giant Pulses from the Pulsar PSR B0031-07

Giant pulses have been detected from the pulsar PSR B0031-07. A pulse with an intensity higher than the intensity of the average pulse by a factor of 50 or more is encountered approximately once per 300 observed periods. The peak flux density of the strongest pulse is 530 Jy, which is a factor of 120 higher than the peak flux density of the average pulse. The giant pulses are a factor of 20 narrower than the integrated profile and are clustered about its center.Comment: 7 pages, 2 figures, to appear in: Pis'ma v Astronomicheskii Zhurnal, 2004, v.30, No.4, and will be translated as: Astronomy Letters, v.30, No.

Instantaneous Radio Spectra of Giant Pulses from the Crab Pulsar from Decimeter to Decameter Wavelengths

The results of simultaneous multifrequency observations of giant radio pulses from the Crab pulsar, PSR B0531+21, at 23, 111, and 600 MHz are presented and analyzed. Giant pulses were detected at a frequency as low as 23 MHz for the first time. Of the 45 giant pulses detected at 23 MHz, 12 were identified with counterparts observed simultaneously at 600 MHz. Of the 128 giant pulses detected at 111 MHz, 21 were identified with counterparts observed simultaneously at 600 MHz. The spectral indices for the power-law frequency dependence of the giant-pulse energies are from -3.1 to -1.6. The mean spectral index is -2.7 +/- 0.1 and is the same for both frequency combinations (600-111 MHz and 600-23 MHz). The large scatter in the spectral indices of the individual pulses and the large number of unidentified giant pulses suggest that the spectra of the individual giant pulses do not actually follow a simple power law. The observed shapes of the giant pulses at all three frequencies are determined by scattering on interstellar plasma irregularities. The scatter broadening of the pulses and its frequency dependence were determined as tau_sc=20*(f/100)^(-3.5 +/- 0.1) ms, where the frequency f is in MHz.Comment: 13 pages, 1 figure, 1 table (originally published in Russian in Astronomicheskii Zhurnal, 2006, vol. 83, No. 7, pp. 630-637), translated by Georgii Rudnitski

Perturbation theory for self-gravitating gauge fields I: The odd-parity sector

A gauge and coordinate invariant perturbation theory for self-gravitating non-Abelian gauge fields is developed and used to analyze local uniqueness and linear stability properties of non-Abelian equilibrium configurations. It is shown that all admissible stationary odd-parity excitations of the static and spherically symmetric Einstein-Yang-Mills soliton and black hole solutions have total angular momentum number $\ell = 1$, and are characterized by non-vanishing asymptotic flux integrals. Local uniqueness results with respect to non-Abelian perturbations are also established for the Schwarzschild and the Reissner-Nordstr\"om solutions, which, in addition, are shown to be linearly stable under dynamical Einstein-Yang-Mills perturbations. Finally, unstable modes with $\ell = 1$ are also excluded for the static and spherically symmetric non-Abelian solitons and black holes.Comment: 23 pages, revtex, no figure

The Evolution of NGC 7027 at Radio Frequencies: A New Determination of the Distance and Core Mass

We present the results of a 25-year program to monitor the radio flux evolution of the planetary nebula NGC7027. We find significant evolution of the spectral flux densities. The flux density at 1465 MHz, where the nebula is optically thick, is increasing at a rate of 0.251+-0.015 % per year, caused by the expansion of the ionized nebula. At frequencies where the emission is optically thin, the spectral flux density is changing at a rate of -0.145+-0.005 % per year, caused by a decrease in the number of ionizing photons coming from the central star. A distance of 980+-100 pc is derived. By fitting interpolated models of post-AGB evolution to the observed changes, we find that over the 25-yr monitoring period, the stellar temperature has increased by 3900+-900 K and the stellar bolometric luminosity has decreased by 1.75+-0.38 %. We derive a distance-independent stellar mass of 0.655+-0.01 solar masses adopting the Bloecker stellar evolution models, or about 0.04 solar masses higher when using models of Vassiliadis & Wood which may provide a better fit. A Cloudy photoionization model is used to fit all epochs at all frequencies simultaneously. The differences between the radio flux density predictions and the observed values show some time-independent residuals of typically 1 %. A possible explanation is inaccuracies in the radio flux scale of Baars et al. We propose an adjustment to the flux density scale of the primary radio flux calibrator 3C286, based on the Cloudy model of NGC7027. We also calculate precise flux densities for NGC7027 for all standard continuum bands used at the VLA, as well as for some new 30GHz experiments.Comment: submitted to the Astrophysical Journa