95,970 research outputs found
Crystallization of Simple Fluids: Relative Stability of f.c.c. and b.c.c Structures
A free-energy functional for a crystal that contains both the symmetry
conserved and symmetry broken parts of the direct pair correlation function is
developed. The free-energy functional is used to investigate the
crystallization of fluids interacting via the inverse power potential ;
. In agreement with simulation results we find
that for the freezing is into close packed f.c.c structure while for
soft repulsions b.c.c phase is more stable.Comment: 9 pages, 2 figure
A characterization of the central shell-focusing singularity in spherical gravitational collapse
We give a characterization of the central shell-focusing curvature
singularity that can form in the spherical gravitational collapse of a bounded
matter distribution obeying the dominant energy condition. This
characterization is based on the limiting behaviour of the mass function in the
neighbourhood of the singularity. Depending on the rate of growth of the mass
as a function of the area radius R, the singularity may be either covered or
naked. The singularity is naked if this growth rate is slower than R, covered
if it is faster than R, and either naked or covered if the growth rate is same
as R.Comment: 12 pages, Latex, significantly revised version, including change of
title. Revised version to appear in Classical and Quantum Gravit
Electron-drift driven ion-acoustic mode in a dusty plasma with collisional effects
Instabilities of ion-acoustic waves in a dusty plasma with electron-drift,
collisional, and dust charge fluctuations effects, have been investigated. The
regimes are clearly marked out where the theory is applicable. The critical
electron-drift velocity required to drive the instability is predicted. It is
also shown that electron thermal conductivity and charged grains concentration
enhance the growth of the ion-acoustic mode whereas ion-viscosity, ion-thermal
conductivity, and dust charge fluctuations have a stabilizing effect.Comment: 7 pages, 3 PS-LaTeX figures (to be published in Physics of Plasmas
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