Stationary transport in mesoscopic hybrid structures with contacts to superconducting and normal wires. A Green's function approach for multiterminal setups

We generalize the representation of the real time Green's functions introduced by Langreth and Nordlander [Phys. Rev. B 43 2541 (1991)] and Meir and Wingreen [Phys. Rev. Lett. 68 2512 (1992)] in stationary quantum transport in order to study problems with hybrid structures containing normal (N) and superconducting (S) pieces. We illustrate the treatment in a S-N junction under a stationary bias and investigate in detail the behavior of the equilibrium currents in a normal ring threaded by a magnetic flux with attached superconducting wires at equilibrium. We analyze the flux sensitivity of the Andreev states and we show that their response is equivalent to the one corresponding to the Cooper pairs with momentum q=0 in an isolated superconducting ring.Comment: 11 pages, 3 figure

Renormalization of modular invariant Coulomb gas and Sine-Gordon theories, and quantum Hall flow diagram

Using the renormalisation group (RG) we study two dimensional electromagnetic coulomb gas and extended Sine-Gordon theories invariant under the modular group SL(2,Z). The flow diagram is established from the scaling equations, and we derive the critical behaviour at the various transition points of the diagram. Following proposal for a SL(2,Z) duality between different quantum Hall fluids, we discuss the analogy between this flow and the global quantum Hall phase diagram.Comment: 10 pages, 1 EPS figure include

Efficient solutions of self-consistent mean field equations for dewetting and electrostatics in nonuniform liquids

We use a new configuration-based version of linear response theory to efficiently solve self-consistent mean field equations relating an effective single particle potential to the induced density. The versatility and accuracy of the method is illustrated by applications to dewetting of a hard sphere solute in a Lennard-Jones fluid, the interplay between local hydrogen bond structure and electrostatics for water confined between two hydrophobic walls, and to ion pairing in ionic solutions. Simulation time has been reduced by more than an order of magnitude over previous methods.Comment: Supplementary material included at end of main pape

Conductivity fluctuations in polymer's networks

Polymer's network is treated as an anisotropic fractal with fractional dimensionality D = 1 + \epsilon close to one. Percolation model on such a fractal is studied. Using the real space renormalization group approach of Migdal and Kadanoff we find threshold value and all the critical exponents to be strongly nonanalytic functions of \epsilon, e.g. the critical exponent of the conductivity was obtained to be \epsilon^{-2}\exp(-1-1/\epsilon). The main part of the finite size conductivities distribution function at the threshold was found to be universal if expressed in terms of the fluctuating variable, which is proportional to the large power of the conductivity, but with dimensionally-dependent low-conductivity cut-off. Its reduced central momenta are of the order of \exp(-1/\epsilon) up to the very high order.Comment: 7 pages, one eps figure, uses epsf style, to be published in Proc. of LEES-97 (Physica B

Boltzmann Collision Term

We derive the Boltzmann equation for scalar fields using the Schwinger-Keldysh formalism. The focus lies on the derivation of the collision term. We show that the relevant self-energy diagrams have a factorization property. The collision term assumes the Boltzmann-like form of scattering probability times statistical factors for those self-energy diagrams which correspond to tree level scattering processes. Our proof covers scattering processes with any number of external particles, which come from self-energy diagrams with any number of loops.Comment: 17 pages, 4 figure

In-Medium Effects in Photo- and Neutrino-Induced Reactions on Nuclei

In this talk various aspects of in-medium behavior of hadrons are discussed with an emphasis on observable effects. It is stressed that final state interactions can have a major effect on observables and thus have to be considered as part of the theory. This is demonstrated with examples from photo-nucleus and neutrino-nucleus interactions.Comment: Invited talk, given by U. Mosel, at MESON2006, 9-th International Workshop on Meson Production, Interaction and Decay, June 9-13, 2006, Cracow, Polan

Artificial electric field in Fermi Liquids

Based on the Keldysh formalism, we derive an effective Boltzmann equation for a quasi-particle associated with a particular Fermi surface in an interacting Fermi liquid. This provides a many-body derivation of Berry curvatures in electron dynamics with spin-orbit coupling, which has received much attention in recent years in non-interacting models. As is well-known, the Berry curvature in momentum space modifies naive band dynamics via an artificial magnetic field in momentum space. Our Fermi liquid formulation completes the reinvention of modified band dynamics by introducing in addition an "artificial electric field", related to Berry curvature in frequency and momentum space. We show explicitly how the artificial electric field affects the renormalization factor and transverse conductivity of interacting U(1) Fermi liquids with non-degenerate bands. Accordingly, we also propose a method of momentum resolved Berry's curvature detection in terms of angle resolved photoemission spectroscopy (ARPES)