藏在暗原子云中的光

集体效应减缓了致密原子云中受激原子的衰减,研究者可以制备并操纵这一亚辐射态。     

Method of phase diagrams in the electrodynamics of plane stratified structures

Radiophysics Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 33, No. 7, pp. 826–831, July, 1990.     

平面对称黑洞的统计熵

避开求解各种粒子波动方程的困难,直接应用量子统计的方法,计算平面对称黑面背景下玻色场与费米场的配分函数,得到黑面熵的积分表达式.然后应用改进的brickwall方法膜模型,计算黑面视界所对应的统计熵.在所得结果中当所取的积分下限和上限都趋于视界上时,可得到黑面熵与相应黑面视界面积成正比的关系,不存在原brickwall方法中的舍去项与对数发散项.整个计算过程,物理图像清楚,计算简单,为研究黑洞熵提供了一条简捷的新途径 关键词： 量子统计 膜模型 黑面熵     

Statistical characteristics of a point-source field in a randomly stratified medium in the absence of regular refraction

The problem of a point-source field in a multidimensional ramdomly stratified medium is considered. The inhomogeneities are described by a delta-correlated Gaussian process with a zero mean. The behavior of the wave-field intensity at the boundary of the half-space is analyzed under given fluctuations of the medium. Analytical results are compared with the results of statistical simulation.Institute of Automation and Process Monitoring, Far-East Branch of the Russian Academy of Sciences, Vladivostok. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 10, pp. 1023–1032, October, 1995.     

Interface separation in the transonic range caused by a plane stress pulse

This is a continuation of the authors' investigation [1] of the localized separation between two contacting solids that is caused by an incident plane elastic wave of arbitrary form. The interface is taken as frictionless and incapable of transmitting tensile tractions. It is further assumed that the two solids have identical mechanical properties, and that the angle of incidence of the incoming wave is such that the disturbance propagates along the interface with a transonic speed. Moving dislocations are employed in the formulation and the problem is reduced to a singular integral equation with a Cauchy kernel. Specific results are worked out for an incident tensile stress pulse of a parabolic shape. An intriguing aspect of the results is that, in spite of the incident wave being continuous, the elastic fields are singular at the trailing edge of the separation zone.     

Absorption of a laser light pulse in a dense plasma

An experimental study of the absorption of a laser light pulse in a transient, high-density, high-temperature plasma is presented. The plasma is generated around a metallic anode tip by a fast capacitive discharge occurring in vacuum. The amount of transmitted light is measured for plasmas made of different metallic ions in the regions of the discharge of high electronic density. Variation of the transmission during the laser pulse is also recorded. Plasma electrons are considered responsible for the very high absorption observed.     

Employing a spheroidal global potential to estimate the quadrupole deformation of nuclei

A spheroidal global shell potential is constructed on the basis of the optical model whose global parameters are extracted from experimental data on nucleon-nucleus scattering. This potential is used to estimate the quadrupole deformation of a large number of light, intermediate, and heavy nuclei in the mass-number range 10 ? A ? 240. The results are compared with the results of similar calculations for the Nilsson potential and with the estimates of the quadrupole deformation that follow from data on the static quadrupole moments of the nuclei considered in the present study.     

Propagation and scattering of light in stratified media

The propagation and scattering of light in stratified media are considered. Based on the Maxwell equations, the present approaches to the solution of these problems are formulated in a unified way. The particular features of the wave propagation in stratified media are discussed. Scalar and vector fields are considered. Media with small-and large-scale regular inhomogeneities are examined. The construction of the Green’s function of the wave equation in a spatially homogeneous medium is discussed. Stratified isotropic and anisotropic media are analyzed. The scattering of light in a stratified medium is studied with emphasis on the Kirchhoff method, as this makes it possible to obtain calculation formulas in a form convenient for comparing the theory with the experiment. The propagation of waves in photonic crystals and the formation of forbidden zones in such objects are briefly considered.     

Simulation of the propagation of a light pulse in a randomly inhomogeneous medium

The propagation of a Gaussian pulse in an inhomogeneous medium is considered. The detected pulse is represented as a series in the scattering multiplicities. The developed approach enables one to describe the passage of a pulse through a randomly inhomogeneous medium in the general case, beyond the framework of the diffusion approximation. The known results of the diffusion approximation are shown to represent limiting cases of the expansion constructed in the scattering multiplicities. The calculations are performed by the Monte Carlo method for cases of singly and multiply scattering media. The agreement between the results of the theoretical analysis and the numerical simulation allows one to use the approach developed in both optical problems and investigation of propagation of waves of other nature, in particular, seismic waves.     

Statistical physics of Bose-Einstein-condensed light in a dye microcavity

We theoretically analyze the temperature behavior of paraxial light in thermal equilibrium with a dye-filled optical microcavity. At low temperatures the photon gas undergoes Bose-Einstein condensation, and the photon number in the cavity ground state becomes macroscopic with respect to the total photon number. Owing to a grand-canonical excitation exchange between the photon gas and the dye molecule reservoir, a regime with unusually large fluctuations of the condensate number is predicted for this system that is not observed in present atomic physics Bose-Einstein condensation experiments.     

Scattering of a light pulse by a spherical particle

In this work the scattering of a brief light pulse by a homogeneous spherical particle is studied within the framework of linear electrodynamics. Convenient formulas are obtained for the scattered fields of the pulse. As a concrete example the Rayleigh scattering of a light pulse is considered.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 80–84, August, 1972.     

Transmission of a light pulse by a nonlinear medium

Resonance interaction is considered for a pulse of monochromatic radiation in a medium of phthalocyanin type, on the basis of a two-level model. The change in pulse width and height are deduced, as is the degree of bleaching.     

Generation of a single tunable ultrashort light pulse

A novel system for generating single tunable ultrashort light pulses of high power is described. The pulse train from a mode-locked flashlamp pumped dye laser passes through an amplifier, which is pumped by an N₂ laser. As gain is only available for a few nsec, only one pulse in the train gets amplified. The energy of the resulting single pulse is about 100 μJ.