Supercurrent Stability in a Quasi-1D Weakly Interacting Bose Gas

We discuss a possibility of observing superfluid phenomena in a quasi-1D weakly interacting Bose gas at finite temperatures. The weakness of interaction in combination with generic properties of 1D liquids can result in a situation when relaxational time of supercurrent is essentially larger than the time of experimental observation, and the behavior of the system is indistinguishable from that of a genuine superfluid.Comment: Revtex, 4 pages, no figures; Submitted to Phys. Rev. A (Brief Reports

Dynamical mean-field theory for bosons

We discuss the recently developed bosonic dynamical mean-field (B-DMFT) framework, which maps a bosonic lattice model onto the selfconsistent solution of a bosonic impurity model with coupling to a reservoir of normal and condensed bosons. The effective impurity action is derived in several ways: (i) as an approximation to the kinetic energy functional of the lattice problem, (ii) using a cavity approach, and (iii) by using an effective medium approach based on adding a one-loop correction to the selfconsistently defined condensate. To solve the impurity problem, we use a continuous-time Monte Carlo algorithm based on a sampling of a perturbation expansion in the hybridization functions and the condensate wave function. As applications of the formalism we present finite temperature B-DMFT phase diagrams for the bosonic Hubbard model on a 3d cubic and 2d square lattice, the condensate order parameter as a function of chemical potential, critical exponents for the condensate, the approach to the weakly interacting Bose gas regime for weak repulsions, and the kinetic energy as a function of temperature.Comment: 26 pages, 19 figure

Driving-Induced Symmetry Breaking in the Spin-Boson System

A symmetric dissipative two-state system is asymptotically completely delocalized independent of the initial state. We show that driving-induced localization at long times can take place when both the bias and tunneling coupling energy are harmonically modulated. Dynamical symmetry breaking on average occurs when the driving frequencies are odd multiples of some reference frequency. This effect is universal, as it is independent of the dissipative mechanism. Possible candidates for an experimental observation are flux tunneling in the variable barrier rf SQUID and magnetization tunneling in magnetic molecular clusters.Comment: 4 pages, 4 figures, to be published in PR

Low-temperature behavior of a Magnetic Impurity in a Heisenberg Chain

Using the bosonization technique, we have studied a spin-1/2 magnetic impurity in Heisenberg chain, and shown that the impurity specific heat and spin susceptibility have an anomalous temperature dependence.Comment: 12 pages, Revtex, no figure, to be published in Phys. Rev. Let

Qubit Entanglement Dephasing Dynamics Driven by a Bath of Spins

We study the entanglement dynamics for a two-spin system coupled to a spin environment of different configurations by z-x type interaction. The models considered in this paper are solved both analytically and numerically giving rise to some concise analytical expressions when certain approximations are properly made. Our purpose is to find how the initial states of the environment with different numbers of spins affect the decay or revival of the entanglement between central qubits. In Particular, it is found that the block-entangled environment could speed up the decay and revival of the qubit entanglement. Our results exhibit some interesting features that have not been found for a boson bath.Comment: 13 pages, 8 figures.Submitted to New Journal of Physic

Formation Conditions of Copper Porphyry Mineralization in the Kadica–Bukovik Ore District, Eastern Macedonia

Macedonia is located in the Serbian–Macedonian sector of the Eurasian Tethys metallogenic belt (Fig. 1). Mineralization related to Cenozoic activation in this area is expressed in the formation of a volcanoplutonic complex in the dispersed spreading setting [1]. Previous joint works with Macedonian geologists made it possible to establish that the present-day tectonic structure of Macedonia reflects dislocations closely related to Cenozoic magmatism and productive mineralization [2]. The Kadica–Bukovik ore district is located in the easternmost Surdulica–Osogovo–Pasos metallogenic zone characterized by the wide development of lead– zinc mineralization (Fig. 1). The zone incorporates systems of sheeted bodies and discordant dikes of quartz latites with an absolute age within 24–12 Ma. Recent discovery of the gold-bearing porphyry copper mineralization in the eastern Kadica ore district is inconsistent with its metallogenic specialization and previous metallogenic model of this belt [2]. To study this phenomenon, we carried out complex studies, which involved structural–geomorphological analysis of ore district [4], on the one hand, and thermobarogeochemical study of ore formation conditions, on the other hand