1,753 research outputs found
Temperature of nonextensive system: Tsallis entropy as Clausius entropy
The problem of temperature in nonextensive statistical mechanics is studied.
Considering the first law of thermodynamics and a "quasi-reversible process",
it is shown that the Tsallis entropy becomes the Clausius entropy if the
inverse of the Lagrange multiplier, , associated with the constraint on
the internal energy is regarded as the temperature. This temperature is
different from the previously proposed "physical temperature" defined through
the assumption of divisibility of the total system into independent subsystems.
A general discussion is also made about the role of Boltzmann's constant in
generalized statistical mechanics based on an entropy, which, under the
assumption of independence, is nonadditive.Comment: 14 pages, no figure
A Semi-relativistic Equation of State for Stellar Interiors
Using the technique of Pade Approximants for the correlation contributions of
charged particles we are able to reproduce complex mathematical expressions by
simple algebraic formulas. The Pade formulas are analytical expressions, which
interpolate between certain density-temperature regions and are characterized
by exact asymptotics. We present a semi-relativistic description of the
thermodynamics applicable for stellar interiors. Comparisons with
equation-of-state data obtained by other calculational schemes are presented.Comment: 4 pages including 2 PostScript figures, also available from
http://www.speckle.mpifr-bonn.mpg.de/publications.html, accepted for
publication in Contributions to Plasma Physic
Nonextensivity in Geological Faults?
Geological fault systems, as the San Andreas fault (SAF) in USA, constitute
typical examples of self-organizing systems in nature. In this paper, we have
considered some geophysical properties of the SAF system to test the viability
of the nonextensive models for earthquakes developed in [Phys. Rev. E {\bf 73},
026102, 2006]. To this end, we have used 6188 earthquakes events ranging in the
magnitude interval that were taken from the Network Earthquake
International Center catalogs (NEIC, 2004-2006) and the Bulletin of the
International Seismological Centre (ISC, 1964-2003). For values of the Tsallis
nonextensive parameter , it is shown that the energy
distribution function deduced in above reference provides an excellent fit to
the NEIC and ISC SAF data.Comment: 9 pages, 1 figure, standard LaTeX fil
Accessing directly the strange quark content of the proton at HERA
We investigate a double-spin asymmetry for the semi-inclusive
hyperon production in the longitudinally deep inelastic lepton-proton
scattering, the sign of which can provide us with important information about
the strange quark helicity distribution in the proton.On the basis of the
interpretation of the longitudinal deep inelastic lepton-nucleon scattering
data as a negative strange quark polarization in the proton and the preliminary
results on the measurement of the longitudinal polarization at the
resonance in electron-positron annihilation,we predict a minus sign for the
suggested observable. The experimental condition required for our suggestion is
met by the HERA facilities, so the asymmetry considered can be measured by the
HERMES experiments at HERA in the near future.Comment: 10 pages, Revtex, completely rephrased, references adde
Mean Field Fluid Behavior of the Gaussian Core Model
We show that the Gaussian core model of particles interacting via a
penetrable repulsive Gaussian potential, first considered by Stillinger (J.
Chem. Phys. 65, 3968 (1976)), behaves like a weakly correlated ``mean field
fluid'' over a surprisingly wide density and temperature range. In the bulk the
structure of the fluid phase is accurately described by the random phase
approximation for the direct correlation function, and by the more
sophisticated HNC integral equation. The resulting pressure deviates very
little from a simple, mean-field like, quadratic form in the density, while the
low density virial expansion turns out to have an extremely small radius of
convergence. Density profiles near a hard wall are also very accurately
described by the corresponding mean-field free-energy functional. The binary
version of the model exhibits a spinodal instability against de-mixing at high
densities. Possible implications for semi-dilute polymer solutions are
discussed.Comment: 13 pages, 2 columns, ReVTeX epsfig,multicol,amssym, 15 figures;
submitted to Phys. Rev. E (change: important reference added
Equation of state of fully ionized electron-ion plasmas
Thermodynamic quantities of Coulomb plasmas consisting of point-like ions
immersed in a compressible, polarizable electron background are calculated for
ion charges Z=1 to 26 and for a wide domain of plasma parameters ranging from
the Debye-Hueckel limit to the crystallization point and from the region of
nondegenerate to fully degenerate nonrelativistic or relativistic electrons.
The calculations are based on the linear-response theory for the electron-ion
interaction, including the local-field corrections in the electronic dielectric
function. The thermodynamic quantities are calculated in the framework of the
N-body hypernetted-chain equations and fitted by analytic expressions. We
present also accurate analytic approximations for the free energy of the ideal
electron gas at arbitrary degeneracy and relativity and for the excess free
energy of the one-component plasma of ions (OCP) derived from Monte Carlo
simulations.
The extension to multi-ionic mixtures is discussed within the framework of
the linear mixing rule. These formulae provide a completely analytic, accurate
description of the thermodynamic quantities of fully ionized electron-ion
Coulomb plasmas, a useful tool for various applications from liquid state
theory to dense stellar matter.Comment: 13 pages, 2 tables, 7 figures, REVTeX using epsf.sty. To be published
in Phys. Rev. E, vol. 58 (1998
Naturalness and Focus Points with Non-Universal Gaugino Masses
Relations between the gaugino masses have been shown to alleviate the degree
of fine-tuning in the MSSM. In this paper we consider specific models of
supersymmetry breaking with gravity mediation and demonstrate that within both
GUT and string constructions it is possible to generate these relations in a
natural way. We have numerically studied the degree of fine-tuning in these
models, including one-loop corrections, and have found regions of parameter
space that can satisfy all known collider constraints with fine-tunings less
than 20%. We discuss some of the phenomenological features of these models
within the regions of reduced fine-tuning.Comment: 31 pages, 21 figures. Version accepted for publication in Nuclear
Physics
Structure Functions of Unstable Lithium Isotopes
We study both the spin-average and spin-dependent structure functions of the
lithium isotopes, Li, which could be measured at RIKEN and other
nuclear facilities in the future. It is found that the light-cone momentum
distribution of the valence neutron in the halo of Li is very sharp and
symmetric around y = 1, because of the weak binding. The EMC ratios for Li
isotopes are then calculated. We study the possibility of extracting the
neutron structure function from data for the nuclear structure functions of the
Li isotopes. Next we calculate the spin-dependent structure functions of
Li isotopes, which have spin of 3/2. The effect of the nuclear
binding and Fermi motion on the multipole spin structure function,
, is about 10% in the region x < 0.7, but it becomes quite
important at large x. The spin structure function of is also
investigated. Finally, we discuss the modification of the Gottfried and Bjorken
integrals in a nuclear medium and point out several candidates for a pair of
mirror nuclei to study the flavor-nonsinglet quark distributions in nuclei.Comment: 23 pages + 7 tables + 15 figure
Screening of Spherical Colloids beyond Mean Field -- A Local Density Functional Approach
We study the counterion distribution around a spherical macroion and its
osmotic pressure in the framework of the recently developed
Debye-H"uckel-Hole-Cavity (DHHC) theory. This is a local density functional
approach which incorporates correlations into Poisson-Boltzmann theory by
adding a free energy correction based on the One Component Plasma. We compare
the predictions for ion distribution and osmotic pressure obtained by the full
theory and by its zero temperature limit with Monte Carlo simulations. They
agree excellently for weakly developed correlations and give the correct trend
for stronger ones. In all investigated cases the DHHC theory and its
computationally simpler zero temperature limit yield better results than the
Poisson-Boltzmann theory.Comment: 10 pages, 4 figures, 2 tables, RevTeX4-styl
- âŠ