About the sign ambiguity in the evaluation of Grand Canonical traces for quasi-particle statistical density operators. Abstract A simple and general prescription for evaluating unambiguously the sign of the grand-canonical trace of quasi-particle statistical density operators (the so-called sign ambiguity in taking the square root of determinants) is given. Sign ambiguities of this kind appear ...

The study of noncommutative solitons is greatly facilitated if the field equations are integrable, i.e. result from a linear system. For the example of a modified but integrable U(n) sigma model in 2+1 dimensions we employ the dressing method to construct explicit multi-soliton configurations on noncommutative R. These solutions, abelian and nonabelian, feature exact time-dependence for any val...

In a series of two papers we present the theoretical results of πN/meson-baryon scattering in the Kadyshevsky formalism. In this paper the results are given for meson exchange diagrams. On the formal side we show, by means of an example, how general couplings, i.e. couplings containing multiple derivatives and/or higher spin fields, should be treated. We do this by introducing and applying the ...

We describe a pairing mean-field theory related to the Hartree-Fock-Bogoliubov approach, and apply it to the dynamics of dissociation of a molecular Bose-Einstein condensate into correlated bosonic atom pairs. We also perform the same simulation using two stochastic phase-space techniques for quantum dynamics—the positive-P representation method and the truncated Wigner method. By comparing the...

We present a general method for constructing perturbative quantum field theories with global symmetries. We start from a free non-interacting quantum field theory with given global symmetries and we determine all perturbative quantum deformations assuming the construction is not obstructed by anomalies. The method is established within the causal Bogoliubov-Shirkov-Epstein-Glaser approach to pe...

The method of choice for describing attractive quantum systems is Hartree-Fock-Bogoliubov (HFB) theory. This is a nonlinear model which allows for the description of pairing effects, the main explanation for the superconductivity of certain materials at very low temperature. This paper is the first study of Hartree-Fock-Bogoliubov theory from the point of view of numerical analysis. We start by...

A bstract We study the 2D symmetric orbifold CFT of two copies free bosons. The twist operator can join separated in untwisted sector into a joined copy twisted sector. Starting with state any number quanta sector, obtained by action be computed using covering map method. develop new method to compute effect Bogoliubov ansatz and conformal symmetry. This may lead more efficient tools correlatio...

Superconductivity is one of the historical landmarks in condensed matter physics. Since Onnes found out the fact that the electrical resistivity of mercury drops to zero below the temperature 4.2K in 1911, the zero electrical resistivity is observed in many metals and alloys. Such a phenomenon is called superconductivity, and the magnetic properties of superconductors as well as their electric ...

In the present investigation, some novel analytical approximations to both unforced and forced pendulum–cart system oscillators are obtained. our two accurate effective approaches, namely, ansatz method with equilibrium point Krylov–Bogoliubov–Mitropolsky (KBM) method, implemented for analyzing problems.The obtained results compared Runge–Kutta (RK4) numerical approximation. The using KBM metho...

We demonstrate that the time-dependent projected Gross-Pitaevskii equation ~GPE! derived earlier @M. J. Davis, R. J. Ballagh, and K. Burnett, J. Phys. B 34, 4487 ~2001!# can represent the highly occupied modes of a homogeneous, partially-condensed Bose gas. Contrary to the often held belief that the GPE is valid only at zero temperature, we find that this equation will evolve randomized initial...