6,865 research outputs found
Rate of Homogeneous Crystal Nucleation in molten NaCl
We report a numerical simulation of the rate of crystal nucleation of sodium
chloride from its melt at moderate supercooling. In this regime nucleation is
too slow to be studied with "brute-force" Molecular Dynamics simulations. The
melting temperature of ("Tosi-Fumi") NaCl is K. We studied crystal
nucleation at =800K and 825K. We observe that the critical nucleus formed
during the nucleation process has the crystal structure of bulk NaCl.
Interestingly, the critical nucleus is clearly faceted: the nuclei have a
cubical shape. We have computed the crystal-nucleation rate using two
completely different approaches, one based on an estimate of the rate of
diffusive crossing of the nucleation barrier, the other based on the Forward
Flux Sampling and Transition Interface Sampling (FFS-TIS) methods. We find that
the two methods yield the same result to within an order of magnitude. However,
when we compare the extrapolated simulation data with the only available
experimental results for NaCl nucleation, we observe a discrepancy of nearly 5
orders of magnitude. We discuss the possible causes for this discrepancy
Two dimensional black-hole as a topological coset model of c=1 string theory
We show that a special superconformal coset (with ) is equivalent
to matter coupled to two dimensional gravity. This identification allows
a direct computation of the correlation functions of the non-critical
string to all genus, and at nonzero cosmological constant, directly from the
continuum approach. The results agree with those of the matrix model. Moreover
we connect our coset with a twisted version of a Euclidean two dimensional
black hole, in which the ghost and matter systems are mixed.Comment: 51 pages. Appendix by E. Frenke
The long wavelength limit of hard thermal loop effective actions
We derive a closed form expression for the long wavelength limit of the
effective action for hard thermal loops in an external gravitational field. It
is a function of the metric, independent of time derivatives. It is compared
and contrasted with the static limit, and with the corresponding limits in an
external Yang-Mills field.Comment: 5 page
Single-file diffusion and kinetics of template assisted assembly of colloids
We report computer simulation studies of the kinetics of ordering of a two
dimensional system of particles on a template with a one dimensional periodic
pattern. In equilibrium one obtains a re-entrant liquid-solid-liquid phase
transition as the strength of the substrate potential is varied. We show that
domains of crystalline order grow as , with with a
possible cross-over to at late times. We argue that the
law originates from {\em single-file} motion and annihilation of defect pairs
of opposite topological charge along channels created by the template.Comment: 4 pages pdflatex 4 pdf figure
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