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Finite Temperature (finite + temperature)
Selected AbstractsA disc-wind model with correct crossing of all magnetohydrodynamic critical surfacesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2000N. Vlahakis The classical Blandford & Payne model for the magneto-centrifugal acceleration and collimation of a disc-wind is revisited and refined. In the original model, the gas is cold and the solution is everywhere subfast magnetosonic. In the present model the plasma has a finite temperature and the self-consistent solution of the MHD equations starts with a subslow magnetosonic speed which subsequently crosses all critical points, at the slow magnetosonic, Alfvén and fast magnetosonic separatrix surfaces. The superfast magnetosonic solution thus satisfies MHD causality. Downstream of the fast magnetosonic critical point the poloidal streamlines overfocus towards the axis and the solution is terminated. The validity of the model to disc winds associated with young stellar objects is briefly discussed. [source] Effect of magnon,LA phonon interaction on LA phonon excitation at finite temperaturePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2008Tai-Min Cheng Abstract A magnon,longitudinal acoustic (LA) phonon interaction model is developed on the basis of a two-dimensional square Heisenberg ferromagnetic system. The LA phonon excitation is studied by Matsubara,Green function theory, and the LA phonon excitation dispersion curves are calculated on the main symmetric lines in Brillouin zone (BZ). It is found that there exists obvious LA phonon hardening. The hardening of LA phonons becomes more evident near the M point of the BZ boundary. The influences of various parameters on LA phonon hardening are also discussed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Local level statistics for optical and transport properties of disordered systems at finite temperaturePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2006A. Malyshev Abstract It is argued that the (traditional) global level statistics which determines localization and coherent transport properties of disordered systems (e.g. the Anderson model) at zero temperature becomes inappropriate when it comes to incoherent transport. We define local level statistics which proves to be relevant for finite temperature incoherent transport and optics of one-dimensional systems (e.g. molecular aggregates, conjugated polymers, etc.). (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Purely electronic transport and localization in the Bose glassANNALEN DER PHYSIK, Issue 12 2009M. Müller Abstract We discuss transport and localization properties on the insulating side of the disorder dominated superconductor-insulator transition, described in terms of the dirty boson model. Analyzing the spectral properties of the interacting bosons in the absence of phonons, we argue that the Bose glass phase admits three distinct regimes. For strongest disorder the boson system is a fully localized, perfect insulator at any temperature. At smaller disorder, only the low temperature phase exhibits perfect insulation while delocalization takes place above a finite temperature. We argue that a third phase must intervene between these perfect insulators and the superconductor. This conducting Bose glass phase is characterized by a mobility edge in the many body spectrum, located at finite energy above the ground state. In this insulating regime purely electronically activated transport occurs, with a conductivity following an Arrhenius law at asymptotically low temperatures, while a tendency to superactivation is predicted at higher T. These predictions are in good agreement with recent transport experiments in highly disordered films of superconducting materials. [source] | ||||||||||