Algebraic independence of values of a subclass of entire functions

Translated from Matematicheskie Zametki, Vol. 51, No. 6, pp. 46–51, June, 1992.     

A pulsed laser employing Ar+ ions at high currents and low pressures

There are several papers [1–5] on pulsed Ar⁺ lasers, but all the tests have been done at low current densities (100 A/cm²). We have used densities up to 15–20 kA/cm², the best pressure range being 8×10^–3 to 2×10^–2 mm Hg. The generation under these conditions has some features not seen under ordinary conditions.     

Transformation of the polariton spectrum of a one-dimensional magnetic photonic crystal in an external dc electric field

The conditions are determined for a one-dimensional magnetic superlattice composed of an easy-axis antiferromagnet and a nonmagnetic dielectric, whose axis is collinear with the easy magnetization axis, under which quadratic magneto-optical interaction in an external dc electric field leads to a number of specific features upon localization and propagation of magnetic TM and TE polaritons.     

Refraction of <Emphasis Type="Italic">s</Emphasis>- and <Emphasis Type="Italic">p</Emphasis>-polarized electromagnetic waves at the interface between a nonmagnetic insulator and an easy-axis centroantisymmetric antiferromagnet

Using the example of an easy-axis antiferromagnet with a magnetic structure of 4 _z ⁻2 _x ⁺ I ⁻ the effect of antisymmetric magnetoelectric interaction on the nature of the refraction of the bulk s- or p-polarized electromagnetic waves, incident from outside at any angle to the surface of the magnet, is studied analytically. The easy magnetic axis is collinear to the normal to the medium interface.     

Spatially modulated antiferromagnetic structures in an easy-plane multiferroic

Possible types of spatially modulated periodic antiferromagnetic structures in a uniaxial rhombohedral multiferroic with BiFeO₃ crystal symmetry have been studied depending on the ratio of the uniaxial anisotropy and magnetoelectric interaction parameters. It has been shown that, along with symmetric cycloid antiferromagnetic structures with zero transverse component of the antiferromagnetism vector, there are changes in the antiferromagnetism vector direction with both right and left nonzero components of the antiferromagnetic moment, which are branched from the high-symmetry spatially modulated distribution. These solutions degenerate into a homogeneous state at a critical value of the normalized easy-plane anisotropy parameter. The existence of the found spatially inhomogeneous antiferromagnetic states with an incommensurate period can lead to additional features in magnetoelectric properties in multiferroics of the type under consideration near magnetic phase transitions in electric and magnetic fields.     

Sensitivity enhancement of the gravitational detector OGRAN

The gravitational wave antenna OGRAN is installed in the underground laboratory of the Baksan Neutrino Observatory. At the present time, it has a limited sensitivity sufficient only to detect gravitational radiation from sources situated at a distance of about 100 kpc. The calculations presented in this paper demonstrate the increase in the sensitivity by two orders of magnitude with cooling of the acoustical resonator of the antenna to the liquid-nitrogen temperature. The possibility of using the same optical detection scheme as the one under room temperature is discussed. The revised construction of the cryogenic version of the OGRAN antenna is considered. The results of experiments carried out with the pilot model of cryogenic antenna are presented.     

Combined weak-current discharge in a copper-vapor laser

We have considered the application of a new method of pumping of active media on metal vapors by a combined weak-current discharge. A distinguishing feature of a weak-current discharge compared to the method for the traditional pumping of self-contained lasers is the regime of lower energy input to the discharge. Using this regime, it is possible to realize a pulsed-periodic form of the discharge with laser pulses of various shapes and durations at low current amplitudes (several amperes). Additional pulsed-periodic discharge is used to heat the active zone.     

The defects and spectral properties of sapphire grown by melting methods

The paper is devoted to the study of the spectral properties of the sapphire single crystals grown by Verneuil, Czochralski, Cyropulos, Stepanov and horizontal directed crystallization methods. Varing the methods, parameters of growth and starting material purity, one can control the concentration of electronic and hole centers in wide range and spectral properties of sapphire up to the irradiation.