The Nature of Thermopower in Bipolar Semiconductors

The thermoemf in bipolar semiconductors is calculated. It is shown that it is necessary to take into account the nonequilibrium distribution of electron and hole concentrations (Fermi quasilevels of the electrons and holes). We find that electron and hole electric conductivities of contacts of semiconductor samples with connecting wires make a substantial contribution to thermoemf.Comment: 17 pages, RevTeX 3.0 macro packag

Effect of fluctuations on vortex lattice structural transitions in superconductors

The rhombic-to-square transition field $H_{\Box}(T)$ for cubic and tetragonal materials in fields along [001] is evaluated using the nonlocal London theory with account of thermal vortex fluctuations. Unlike extended Ginzburg-Landau models, our approach shows that the line $H_{\Box}(T)$ and the upper critical field $H_{c2}(T)$ do not cross due to strong fluctuations near $H_{c2}(T)$ which suppress the square anisotropy induced by the nonlocality. In increasing fields, this causes re-entrance of the rhombic structure in agreement with recent neutron scattering data on borocarbides.Comment: 4 pages, 2 figure

Analytic model for a frictional shallow-water undular bore

We use the integrable Kaup-Boussinesq shallow water system, modified by a small viscous term, to model the formation of an undular bore with a steady profile. The description is made in terms of the corresponding integrable Whitham system, also appropriately modified by friction. This is derived in Riemann variables using a modified finite-gap integration technique for the AKNS scheme. The Whitham system is then reduced to a simple first-order differential equation which is integrated numerically to obtain an asymptotic profile of the undular bore, with the local oscillatory structure described by the periodic solution of the unperturbed Kaup-Boussinesq system. This solution of the Whitham equations is shown to be consistent with certain jump conditions following directly from conservation laws for the original system. A comparison is made with the recently studied dissipationless case for the same system, where the undular bore is unsteady.Comment: 24 page

Dynamics of Macroscopic Tunneling in Elongated BEC

We investigate macroscopic tunneling from an elongated quasi 1-d trap, forming a 'cigar shaped' BEC. Using recently developed formalism we get the leading analytical approximation for the right hand side of the potential wall, i.e. outside the trap, and a formalism based on Wigner functions, for the left side of the potential wall, i.e. inside the BEC. We then present accomplished results of numerical calculations, which show a 'blip' in the particle density traveling with an asymptotic shock velocity, as resulted from previous works on a dot-like trap, but with significant differences from the latter. Inside the BEC a pattern of a traveling dispersive shock wave is revealed. In the attractive case, we find trains of bright solitons frozen near the boundary.Comment: 6 pages, 15 figure

Quantum orbits of R-matrix type

Given a simple Lie algebra \gggg, we consider the orbits in \gggg^* which are of R-matrix type, i.e., which possess a Poisson pencil generated by the Kirillov-Kostant-Souriau bracket and the so-called R-matrix bracket. We call an algebra quantizing the latter bracket a quantum orbit of R-matrix type. We describe some orbits of this type explicitly and we construct a quantization of the whole Poisson pencil on these orbits in a similar way. The notions of q-deformed Lie brackets, braided coadjoint vector fields and tangent vector fields are discussed as well.Comment: 18 pp., Late

Mass Transfer Mechanism in Real Crystals by Pulsed Laser Irradiation

The dynamic processes in the surface layers of metals subjected activity of a pulsing laser irradiation, which destroyed not the crystalline structure in details surveyed. The procedure of calculation of a dislocation density generated in bulk of metal during the relaxation processes and at repeated pulse laser action is presented. The results of evaluations coincide with high accuracy with transmission electron microscopy dates. The dislocation-interstitial mechanism of laser-stimulated mass-transfer in real crystals is presented on the basis of the ideas of the interaction of structure defects in dynamically deforming medium. The good compliance of theoretical and experimental results approves a defining role of the presented mechanism of mass transfer at pulse laser action on metals. The possible implementation this dislocation-interstitial mechanism of mass transfer in metals to other cases of pulsing influences is justifiedComment: 10 pages, 2 figures, Late

On the temperature dependence of ballistic Coulomb drag in nanowires

We have investigated within the theory of Fermi liquid dependence of Coulomb drag current in a passive quantum wire on the applied voltage $V$ across an active wire and on the temperature $T$ for any values of $eV/k_BT$. We assume that the bottoms of the 1D minibands in both wires almost coincide with the Fermi level. We come to conclusions that 1) within a certain temperature interval the drag current can be a descending function of the temperature $T$; 2) the experimentally observed temperature dependence $T^{-0.77}$ of the drag current can be interpreted within the framework of Fermi liquid theory; 3) at relatively high applied voltages the drag current as a function of the applied voltage saturates; 4) the screening of the electron potential by metallic gate electrodes can be of importance.Comment: 7 pages, 1 figur

Absorption suppression in photonic crystals

We study electromagnetic properties of periodic composite structures, such as photonic crystals, involving lossy components. We show that in many cases a properly designed periodic structure can dramatically suppress the losses associated with the absorptive component, while preserving or even enhancing its useful functionality. As an example, we consider magnetic photonic crystals, in which the lossy magnetic component provides nonreciprocal Faraday rotation. We show that the electromagnetic losses in the composite structure can be reduced by up to two orders of magnitude, compared to those of the uniform magnetic sample made of the same lossy magnetic material. Importantly, the dramatic absorption reduction is not a resonance effect and occurs over a broad frequency range covering a significant portion of photonic frequency band

Whitham systems and deformations

We consider the deformations of Whitham systems including the "dispersion terms" and having the form of Dubrovin-Zhang deformations of Frobenius manifolds. The procedure is connected with B.A. Dubrovin problem of deformations of Frobenius manifolds corresponding to the Whitham systems of integrable hierarchies. Under some non-degeneracy requirements we suggest a general scheme of the deformation of the hyperbolic Whitham systems using the initial non-linear system. The general form of the deformed Whitham system coincides with the form of the "low-dispersion" asymptotic expansions used by B.A. Dubrovin and Y. Zhang in the theory of deformations of Frobenius manifolds.Comment: 27 pages, Late