3,355 research outputs found
Comparison of calculated radiochemical cross sections with experimental results for incident protons and negative pions in the 50 to 400 MeV region - Effect of varying a few nuclear parameters in the calculations
Effect of varying nuclear parameters in calculating radiochemical cross sections for incident proton and negative pion reactions in 50 to 400 MeV regio
Some Effects of a Modified Evaporation Program on Calculations of Radiochemical Cross Sections and Particle Multiplicities for Protons on Carbon and Aluminum Targets
Modified Fortran evaporation program used for calculating radiochemical cross sections and particle multiplicities for protons on carbon and aluminum target
Towards a nonequilibrium thermodynamics: a self-contained macroscopic description of driven diffusive systems
In this paper we present a self-contained macroscopic description of
diffusive systems interacting with boundary reservoirs and under the action of
external fields. The approach is based on simple postulates which are suggested
by a wide class of microscopic stochastic models where they are satisfied. The
description however does not refer in any way to an underlying microscopic
dynamics: the only input required are transport coefficients as functions of
thermodynamic variables, which are experimentally accessible. The basic
postulates are local equilibrium which allows a hydrodynamic description of the
evolution, the Einstein relation among the transport coefficients, and a
variational principle defining the out of equilibrium free energy. Associated
to the variational principle there is a Hamilton-Jacobi equation satisfied by
the free energy, very useful for concrete calculations. Correlations over a
macroscopic scale are, in our scheme, a generic property of nonequilibrium
states. Correlation functions of any order can be calculated from the free
energy functional which is generically a non local functional of thermodynamic
variables. Special attention is given to the notion of equilibrium state from
the standpoint of nonequilibrium.Comment: 21 page
Quantum quench in the sine-Gordon model
We consider the time evolution in the repulsive sine-Gordon quantum field
theory after the system is prepared in a particular class of initial states. We
focus on the time dependence of the one-point function of the semi-local
operator . By using two different methods
based on form-factor expansions, we show that this expectation value decays to
zero exponentially, and we determine the decay rate by analytical means. Our
methods generalise to other correlation functions and integrable models.Comment: 41 pages, 1 figure, some typos correcte
Prethermalization and thermalization in models with weak integrability breaking
We study the effects of integrability breaking perturbations on the
non-equilibrium evolution of many-particle quantum systems. We focus on a class
of spinless fermion models with weak interactions. We employ equation of motion
techniques that can be viewed as generalizations of quantum Boltzmann
equations. We benchmark our method against time dependent density matrix
renormalization group computations and find it to be very accurate as long as
interactions are weak. For small integrability breaking, we observe robust
prethermalization plateaux for local observables on all accessible time scales.
Increasing the strength of the integrability breaking term induces a "drift"
away from the prethermalization plateaux towards thermal behaviour. We identify
a time scale characterizing this cross-over.Comment: 9 pages, 4 figure
Long range correlations and phase transition in non-equilibrium diffusive systems
We obtain explicit expressions for the long range correlations in the ABC
model and in diffusive models conditioned to produce an atypical current of
particles.In both cases, the two-point correlation functions allow to detect
the occurrence of a phase transition as they become singular when the system
approaches the transition
Literature Survey of Radiochemical Cross-section Data Below 425 Mev
Literature survey of radiochemical cross sections below 425 Me
Non equilibrium current fluctuations in stochastic lattice gases
We study current fluctuations in lattice gases in the macroscopic limit
extending the dynamic approach for density fluctuations developed in previous
articles. More precisely, we establish a large deviation principle for a
space-time fluctuation of the empirical current with a rate functional \mc
I (j). We then estimate the probability of a fluctuation of the average
current over a large time interval; this probability can be obtained by solving
a variational problem for the functional \mc I . We discuss several possible
scenarios, interpreted as dynamical phase transitions, for this variational
problem. They actually occur in specific models. We finally discuss the time
reversal properties of \mc I and derive a fluctuation relationship akin to
the Gallavotti-Cohen theorem for the entropy production.Comment: 36 Pages, No figur
Lagrangian phase transitions in nonequilibrium thermodynamic systems
In previous papers we have introduced a natural nonequilibrium free energy by
considering the functional describing the large fluctuations of stationary
nonequilibrium states. While in equilibrium this functional is always convex,
in nonequilibrium this is not necessarily the case. We show that in
nonequilibrium a new type of singularities can appear that are interpreted as
phase transitions. In particular, this phenomenon occurs for the
one-dimensional boundary driven weakly asymmetric exclusion process when the
drift due to the external field is opposite to the one due to the external
reservoirs, and strong enough.Comment: 10 pages, 2 figure
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