Anomalous density effect near the interface between two media

A theoretical investigation is presented for the local energy loss of a relativistic charged particle and theK-shell excitation cross section σ _K when the particle crosses a sharp interface between two different media. The logarithmic increase of the local energy loss andσ _K with the particle energy is shown to differ essentially from the case of a homogeneous medium. The calculations ofσ _K for aluminum and copper foils are in good agreement with the experimental data.     

Stieltjes Differential in Impulse Nonlinear Problems

Doklady Mathematics - An impulse nonlinear problem admitting discontinuous solutions that are functions of bounded variation is studied. This problem models the deformation of a discontinuous...     

Rate of Radiative p2H Capture

Russian Physics Journal - Within the framework of the modified potential cluster model with forbidden states, we consider radiative p2H capture at energies from 1 keV to 10 MeV. It is shown that on...     

The first results of observations of acoustic signals generated by cosmic ray muons in a seismically stressed medium

The first results of observations of acoustic signals generated by high-energy muons of extensive air showers, which propagate in a seismically stressed medium are presented. The cosmophysical method for monitoring the volume stressed state is tested using the experimental setup developed in the earthquake-prone region of Almaty at the Tien Shan High-Altitude Scientific Station of the Lebedev Physical Institute. High-amplitude acoustic signals correlated with the passage and interaction of muon groups in the Earth’s crust are detected for the first time.     

Stretching of a Cosmic String in the Presence of a Vacuum Domain Wall

It is shown that the domain wall pumps a cosmic string in its gravitational field with a gravitational energy. This increases the tension energy and results in the string straightening. The process of straightening is a new physical mechanism of cosmic-string stretching.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 20–26, April, 2005.     

Ab initio simulation of gap discrete breathers in strained graphene

The methods of the density functional theory were used for the first time for the simulation of discrete breathers in graphene. It is demonstrated that breathers can exist with frequencies lying in the gap of the phonon spectrum, induced by uniaxial tension of a monolayer graphene sheet in the “zigzag” direction (axis X), polarized in the “armchair” direction (axis Y). The found gap breathers are highly localized dynamic objects, the core of which is formed by two adjacent carbon atoms located on the Y axis. The atoms surrounding the core vibrate at much lower amplitudes along both the axes (X and Y). The dependence of the frequency of these breathers on amplitude is found, which shows a soft type of nonlinearity. No breathers of this type were detected in the gap induced by stretching along the Y axis. It is shown that the breather vibrations may be approximated by the Morse oscillators, the parameters of which are determined from ab initio calculations. The results are of fundamental importance, as molecular dynamics calculations based on empirical potentials cannot serve as a reliable proof of the existence of breathers in crystals.     

Group-theoretical analysis of possible structural phase transitions in the high-temperature superconductors

A group-theoretical analysis is performed for the complete condensation of order parameters at structural phase transitions (SPT's) in the high-temperature superconductors belonging to the D ¹⁷ _4h -14/mmm space group in the high-symmetry phase. As a rule, such transformations are due to a successive softening of phonons with wave vectors k ₁ = 1/2 b ₃ and k ₂ = 1/2 (b ₁ - b ₃) belonging to the K13(X) star of the Brillouin zone of a tetragonal body-centered Bravais cell. SPT's in system La_2-x Ba _x CuO₄ are considered in detail.     

Dynamics of systems of extended bodies in monad representation

A universal form proposed earlier by the author for the equations of motion is used to find a monad representation of the equations of motion of a system of N extended bodies in general relativity theory. An explicit form of the equations of motion in a fixed chronometric reference system is presented. It is shown that it differs from the known coordinate motion equations obtained by the Fock method.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 72–78, January, 1995.     

Long-wavelength coherent radio radiation of cascades. I. Calculation within the cascade theory

The long-wavelength limit for radio radiation from high-energy particle cascades was calculated within the cascade theory taking into account the processes resulting in an negative excess. The results obtained were compared to the results of Monte Carlo numerical calculations.