Decoherence and damping in ideal gases

The particle and current densities are shown to display damping and undergo decoherence in ideal quantum gases. The damping is read off from the equations of motion reminiscent of the Navier-Stokes equations and shows some formal similarity with Landau damping. The decoherence leads to consistent density and current histories with characteristic length and time scales given by the ideal gas.Comment: final version, to appear in Europhysical Lette

Confinement as crossover

The order parameter of confinement together with the haaron model of the QCD vacuum is reviewed and it is pointed out that confining forces are generated by the non-renormalizable, invariant Haar-measure vertices of the path integral. A hybrid model is proposed for the description of the crossover leading to the confining vacuum. This scenario suggests that the differences between the low and the high temperature phases of QCD should be looked for in the quark channels instead of the hadronic sector.Comment: 8 pages, delivered at the Workshop on Quark Matter in Astro- and Particle Physics, Rostock, Germany, november, 200

Path Integral for the Dirac Equation

A c-number path integral representation is constructed for the solution of the Dirac equation. The integration is over the real trajectories in the continuous three-space and other two canonical pairs of compact variables controlling the spin and the chirality flips.Comment: 5 pages, revtex. Argument extended, several equations corrected, more references adde

Internal Space Renormalization Group Methods for Atomic and Condensed Matter Physics

The functional renormalization group method is used to take into account the vacuum polarization around localized bound states generated by external potential. The application to Atomic Physics leads to improved Hartree-Fock and Kohn-Sham equations in a systematic manner within the framework of the Density Functional Theory. Another application to Condensed Matter Physics consists of an algorithm to compute quenched averages with or without Coulomb interaction in a non-perturbative manner.Comment: Talk presented at the Conference "Renormalization Group 2002 (RG-2002)" Strba, Slovakia, March 2002, 6 pages no figure

Irreversibility and decoherence in an ideal gas

Different models are described where non-interacting particles generate dissipative effective forces by the mixing of infinitely many soft normal modes. The effective action is calculated for these models within the Closed Time Path formalism. This is a well known scheme for quantum systems but its application in classical mechanics presents a new, more unified derivation and treatment of dissipative forces within classical and quantum physics.Comment: Talk delivered at DICE2014, the Seventh International Workshop on Spacetime - Matter - Quantum Mechanics, Castiglioncello, september 2014, 16 page

Spontaneous breakdown of the time reversal symmetry

The role of the environment initial conditions in the breaking of the time reversal symmetry of effective theories and in generating the soft irreversibility is studied by the help of Closed Time Path formalism. The initial conditions break the time reversal symmetry of the solution of the equation of motion in a trivial manner. When open systems are considered then the initial conditions of the environment must be included in the effective dynamics. This is achieved by means of a generalized $\epsilon$-prescription where the non-uniform convergence of the limit $\epsilon\to0$ leaves behind a spontaneous breakdown of the time reversal symmetry.Comment: Final version, to appear in Symmetr