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Orbital measures in non-equilibrium statistical mechanics: the Onsager relations
We assume that the properties of nonequilibrium stationary states of systems
of particles can be expressed in terms of weighted orbital measures, i.e.
through periodic orbit expansions. This allows us to derive the Onsager
relations for systems of particles subject to a Gaussian thermostat, under
the assumption that the entropy production rate is equal to the phase space
contraction rate. Moreover, this also allows us to prove that the relevant
transport coefficients are not negative. In the appendix we give an argument
for the proper way of treating grazing collisions, a source of possible
singularities in the dynamics.Comment: LaTeX, 14 pages, 1 TeX figure in the tex
The total nucleon-nucleon cross section at large N_c
It is shown that at sufficiently large for incident momenta which are
much larger than the QCD, the total nucleon-nucleon cross section is
independent of incident momentum and given by . This result is valid in the extreme large
regime of and has corrections of relative order . A possible connection of this result to the
Froissart-Martin bound is discussed.Comment: 4 page
Nitramine propellants
Nitramine propellants without a pressure exponent shift in the burning rate curves are prepared by matching the burning rate of a selected nitramine or combination of nitramines within 10% of burning rate of a plasticized active binder so as to smooth out the break point appearance in the burning rate curve
Note on Phase Space Contraction and Entropy Production in Thermostatted Hamiltonian Systems
The phase space contraction and the entropy production rates of Hamiltonian
systems in an external field, thermostatted to obtain a stationary state are
considered. While for stationary states with a constant kinetic energy the two
rates are formally equal for all numbers of particles N, for stationary states
with constant total (kinetic and potential) energy this only obtains for large
N. However, in both cases a large number of particles is required to obtain
equality with the entropy production rate of Irreversible Thermodynamics.
Consequences of this for the positivity of the transport coefficients and for
the Onsager relations are discussed. Numerical results are presented for the
special case of the Lorentz gas.Comment: 16 pages including 1 table and 3 figures. LaTeX forma
Gibbs entropy and irreversible thermodynamics
Recently a number of approaches has been developed to connect the microscopic
dynamics of particle systems to the macroscopic properties of systems in
nonequilibrium stationary states, via the theory of dynamical systems. This way
a direct connection between dynamics and Irreversible Thermodynamics has been
claimed to have been found. However, the main quantity used in these studies is
a (coarse-grained) Gibbs entropy, which to us does not seem suitable, in its
present form, to characterize nonequilibrium states. Various simplified models
have also been devised to give explicit examples of how the coarse-grained
approach may succeed in giving a full description of the Irreversible
Thermodynamics. We analyze some of these models pointing out a number of
difficulties which, in our opinion, need to be overcome in order to establish a
physically relevant connection between these models and Irreversible
Thermodynamics.Comment: 19 pages, 4 eps figures, LaTeX2
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