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# Search results

35,902 records were found.

## Entropy of Open Lattice Systems

Comment: Latex, 28 pages, 4 figures as eps files

## Mott Insulator - Superfluid Transitions in a Two Band Model at Finite Temperature and Possible Application to Supersolid 4He

We study Mott insulator - superfluid transition in a two-band boson Hubbard model, which can be mapped onto a spin-1/2 XY model with spins coupled to an additional Ising degree of freedom. By using a modified mean field theory that include the effects of phase fluctuations, we show that the transition is first order at both zero and finite temperatures. On the Mott insulator side, there may be reentrance in phase transition. These features are consequences of the underlying transition between competing defect poor and defect rich phases. The relevance of the model and our results to supersolid 4He and cold bosonic atoms in optical lattices are discussed.

## Trapping mechanism in overdamped ratchets with quenched noise

Comment: 21 pages, 6 figures, to appear in PRE

## Multicriticality of the (2+1)-dimensional gonihedric model: A realization of the (d,m)=(3,2) Lifshitz point

Multicriticality of the gonihedric model in 2+1 dimensions is investigated numerically. The gonihedric model is a fully frustrated Ising magnet with the finely tuned plaquette-type (four-body and plaquette-diagonal) interactions, which cancel out the domain-wall surface tension. Because the quantum-mechanical fluctuation along the imaginary-time direction is simply ferromagnetic, the criticality of the (2+1)-dimensional gonihedric model should be an anisotropic one; that is, the respective critical indices of real-space (\perp) and imaginary-time (\parallel) sectors do not coincide. Extending the parameter space to control the domain-wall surface tension, we analyze the criticality in terms of the crossover (multicritical) scaling theory. By means of the numerical diagonalization for the clusters with N\le 28 spins, we obtained the c...

## Liquid-vapour transition of the long range Yukawa fluid

Comment: 30 pages, 5 figures

## Kinetic theory of two dimensional point vortices from a BBGKY-like hierarchy

Starting from the Liouville equation, we derive the exact hierarchy of equations satisfied by the reduced distribution functions of the single species point vortex gas in two dimensions. Considering an expansion of the solution in powers of 1/N in a proper thermodynamic limit $N\to +\infty$, and neglecting some collective effects, we derive a kinetic equation satisfied by the smooth vorticity field which is valid at order $O(1/N)$. This equation was obtained previously [P.H. Chavanis, Phys. Rev. E, 64, 026309 (2001)] from a more abstract projection operator formalism. If we consider axisymmetric flows and make a markovian approximation, we obtain a simpler kinetic equation which can be studied in great detail. We discuss the properties of these kinetic equations in regard to the $H$-theorem and the convergence (or not) towards the st...

## Driven Spin Systems as Quantum Thermodynamic Machines: Fundamental Limits

Comment: 9 pages, 11 figures, accepted for publication in Phys. Rev. E

## Percolation transition in networks with degree-degree correlation

Comment: 7 pages, 11 figure

## Revisiting the one-dimensional diffusive contact process

In this work we study the one-dimensional contact process with diffusion using two different approaches to research the critical properties of this model: the supercritical series expansions and finite-size exact solutions. With special emphasis we look to the multicritical point and its crossover exponent that characterizes the passage between DP and mean-field critical properties. This crossover occurs in the limit of infinite diffusion rate and our results pointed $\phi=4$ as the better estimate for the crossover exponent in agreement with computational simulations.

## Distribution of Entropy Production for a Colloidal Particle in a Nonequilibrium Steady State

For a colloidal particle driven by a constant force across a periodic potential, we investigate the distribution of entropy production both experimentally and theoretically. For short trajectories, the fluctuation theorem holds experimentally. The mean entropy production rate shows two regimes as a function of the applied force. Theoretically, both mean and variance of the pronounced non-Gaussian distribution can be obtained from a differential equation in good agreement with the experimental data.