Decoherence Dynamics in Low-Dimensional Cold Atom Interferometers

We report on a study of the dynamics of decoherence of a matter-wave interferometer, consisting of a pair of low-dimensional cold atom condensates at finite temperature. We identify two distinct regimes in the time dependence of the coherence factor of the interferometer: quantum and classical. Explicit analytical results are obtained in both regimes. In particular, in the two-dimensional (2D) case in the classical (long time) regime, we find that the dynamics of decoherence is universal, exhibiting a power-law decay with an exponent, proportional to the ratio of the temperature to the Kosterlitz-Thouless temperature of a single 2D condensate. In the one-dimensional (1D) case in the classical regime we find a universal nonanalytic time dependence of decoherence, which is a consequence of the nonhydrodynamic nature of damping in 1D liquids.Comment: 4 pages, published versio

Phonon Localization in One-Dimensional Quasiperiodic Chains

Quasiperiodic long range order is intermediate between spatial periodicity and disorder, and the excitations in 1D quasiperiodic systems are believed to be transitional between extended and localized. These ideas are tested with a numerical analysis of two incommensurate 1D elastic chains: Frenkel-Kontorova (FK) and Lennard-Jones (LJ). The ground state configurations and the eigenfrequencies and eigenfunctions for harmonic excitations are determined. Aubry's "transition by breaking the analyticity" is observed in the ground state of each model, but the behavior of the excitations is qualitatively different. Phonon localization is observed for some modes in the LJ chain on both sides of the transition. The localization phenomenon apparently is decoupled from the distribution of eigenfrequencies since the spectrum changes from continuous to Cantor-set-like when the interaction parameters are varied to cross the analyticity--breaking transition. The eigenfunctions of the FK chain satisfy the "quasi-Bloch" theorem below the transition, but not above it, while only a subset of the eigenfunctions of the LJ chain satisfy the theorem.Comment: This is a revised version to appear in Physical Review B; includes additional and necessary clarifications and comments. 7 pages; requires revtex.sty v3.0, epsf.sty; includes 6 EPS figures. Postscript version also available at http://lifshitz.physics.wisc.edu/www/koltenbah/koltenbah_homepage.htm

Putting competing orders in their place near the Mott transition

We describe the localization transition of superfluids on two-dimensional lattices into commensurate Mott insulators with average particle density p/q (p, q relatively prime integers) per lattice site. For bosons on the square lattice, we argue that the superfluid has at least q degenerate species of vortices which transform under a projective representation of the square lattice space group (a PSG). The formation of a single vortex condensate produces the Mott insulator, which is required by the PSG to have density wave order at wavelengths of q/n lattice sites (n integer) along the principle axes; such a second-order transition is forbidden in the Landau-Ginzburg-Wilson framework. We also discuss the superfluid-insulator transition in the direct boson representation, and find that an interpretation of the quantum criticality in terms of deconfined fractionalized bosons is only permitted at special values of q for which a permutative representation of the PSG exists. We argue (and demonstrate in detail in a companion paper: L. Balents et al., cond-mat/0409470) that our results apply essentially unchanged to electronic systems with short-range pairing, with the PSG determined by the particle density of Cooper pairs. We also describe the effect of static impurities in the superfluid: the impurities locally break the degeneracy between the q vortex species, and this induces density wave order near each vortex. We suggest that such a theory offers an appealing rationale for the local density of states modulations observed by Hoffman et al. (cond-mat/0201348) in STM studies of the vortex lattice of BSCCO, and allows a unified description of the nucleation of density wave order in zero and finite magnetic fields. We note signatures of our theory that may be tested by future STM experiments.Comment: 35 pages, 16 figures; (v2) part II is cond-mat/0409470; (v3) added new appendix and clarifying remarks; (v4) corrected typo

Stress-strain state of pipeline depending on complicated environment

The paper presents the 3D model and FEM analysis of the stress-strain state of the soil- pipe interaction system. The analysis shows that the geological environment has shown a strong effect on the pipelines. This stress-strain analysis is carried out using the ANSYS finite element program

Mechanical state assessment using lamb wave technique in static tensile tests

The paper deals with the investigation of Lamb wave ultrasonic technique for damage (or mechanical state) evaluation of AA7068T3 specimens in the course of tensile testing. Two piezoelectric transducers (PZT), one of which is used as an actuator and the other as sensor, were adhesively bonded on the specimen surface using epoxy. Two frequencies of testing signals (60 kHz and 350 kHz) were used. The set of static tensile tests were performed. The recorded signals were processed to calculate the informative parameters in order to evaluate the changes in stress-strain state of the specimens and their microstructure

Stress and Strain State Analysis of Defective Pipeline Portion

The paper presents computer simulation results of the pipeline having defects in a welded joint. Autodesk Inventor software is used for simulation of the stress and strain state of the pipeline. Places of the possible failure and stress concentrators are predicted on the defective portion of the pipeline

Correlations in Transmission of Light through a Disordered Amplifying Medium

The angular and frequency correlation functions of the transmission coefficient for light propagation through a strongly scattering amplifying medium are considered. It is found that just as in the case of an elastic scattering medium the correlation function consists of three terms. However, the structure of the terms is rather different. Angular correlation has a power-law decay and exhibits oscillations. There is no "memory effect" as in the case of an elastic medium. Interaction between diffusion modes is strongly enhanced near the lasing threshold. Frequency correlation scale decreases close to the lasing threshold. We also consider time correlations of the transmission in the case of nonstationary inhomogeneities. We find short- and long-range time correlations. The scale of the short-range correlation decreases, while the long-range correlation scale becomes infinite near the threshold.Comment: 16 pages, 7 postscript figure

Theory of Spin-Charge Coupled Transport in a Two-Dimensional Electron Gas with Rashba Spin-Orbit Interactions

We use microscopic linear response theory to derive a set of equations that provide a complete description of coupled spin and charge diffusive transport in a two-dimensional electron gas (2DEG) with the Rashba spin-orbit (SO) interaction. These equations capture a number of interrelated effects including spin accumulation and diffusion, Dyakonov-Perel spin relaxation, magnetoelectric, and spin-galvanic effects. They can be used under very general circumstances to model transport experiments in 2DEG systems that involve either electrical or optical spin injection. We comment on the relationship between these equations and the exact spin and charge density operator equations of motion. As an example of the application of our equations, we consider a simple electrical spin injection experiment and show that a voltage will develop between two ferromagnetic contacts if a spin-polarized current is injected into a 2DEG, that depends on the relative magnetization orientation of the contacts. This voltage is present even when the separation between the contacts is larger than the spin diffusion length.Comment: 8 pages, 1 eps figure. Corrected an error in the calculation of the spin-charge coupling coefficient, pointed out in cond-mat/0406730, added several reference