Modern Physics Letters B

By resorting to some results in quantum field theories with spontaneous breakdown of symmetry, we show that an explanation based on microscopic dynamics can be given for the fact that topological defect formation is observed during the process of non-equilibrium phase transitions characterized by a non-zero order parameter. We show that the Nambu–Goldstone particle acquires an effective non-zero mass due to boundary (finite volume) effects and this is related to the size of the defect. We also relate such volume effects with temperature effects.

The thermal conductivity of a quasiparticle (QP) system described by a relativistic four-fermion interaction model in the presence of an external magnetic field is calculated. It is shown that, for narrow widths of quasiparticles, the thermal conductivity, as a function of the applied magnetic field, exhibits a kink behavior at a critical field B_c ~ T². The kink is due to the opening of a gap in the QP spectrum at a critical magnetic field B_c and to the enhancement of the transitions between the zeroth and first Landau levels. Possible applications of the results are discussed.

The emission probability of a cold atom in a microcavity when its center-of-mass motion is described quantum mechanically is presented, but is distinguished from other treatments by the inclusion of the spatial variation along the cavity axis. In particular, the mesa mode cavity profile is considered. The quantum theory of the one-photon mazer is constructed in the framework of the dressed-state coordinate formalism. Simple expressions for the atomic populations, the cavity photon statistics, and the reflection and transmission probabilities are given for any initial state of the atom-field system. The general conclusions reached are illustrated by numerical results.

Bi_2.1Sr_1.9CuO_y thin films (Bi:2201) were deposited onto heated single crystal (100) MgO substrates using inverted cylindrical DC magnetron sputtering with different partial pressures of oxygen in a sputtering gas. The behavior of the normal state resistivity function of temperature is strongly influenced by the composition of sputtering gas used in thin films synthesis. Near the transition to the superconducting state, electrical resistivity changes strongly from "metallic" to insulator (MI). The origin for the increase of electrical resistance was analyzed using some models for the localization of mobile carriers. A good linearity is obtained for ln R as a function of T^α for α = 1/10 and for R as a function of ln T. The last behavior agrees with the pinning and fragmentation of 1D stripes in CuO₂ planes.

The aim of this paper is to present a mathematical model for the steady state of the dieless drawing process. With this model, it is possible to study the influence of various process parameters, such as temperature, strain, strain rate and stress. The paper also presents some elements of the process control for producing variable cross-sections (cone-contour and sinus-contour).