4,493 research outputs found
A model for projectile fragmentation
A model for projectile fragmentation is developed whose origin can be traced
back to the Bevalac era. The model positions itself between the
phenomenological EPAX parametrization and transport models like "Heavy Ion
Phase Space Exploration" (HIPSE) model and antisymmetrised molecular dynamics
(AMD) model. A very simple impact parameter dependence of input temperature is
incorporated in the model which helps to analyze the more peripheral
collisions. The model is applied to calculate the charge, isotopic
distributions, average number of intermediate mass fragments and the average
size of largest cluster at different Z_{bound} of different projectile
fragmentation reactions at different energies.Comment: Talk given by Gargi Chaudhuri at the 11th International Conference on
Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1,
2012. 10 pages, 7 figure
Pair Correlation Function of Wilson Loops
We give a path integral prescription for the pair correlation function of
Wilson loops lying in the worldvolume of Dbranes in the bosonic open and closed
string theory. The results can be applied both in ordinary flat spacetime in
the critical dimension d or in the presence of a generic background for the
Liouville field. We compute the potential between heavy nonrelativistic sources
in an abelian gauge theory in relative collinear motion with velocity v =
tanh(u), probing length scales down to r_min^2 = 2 \pi \alpha' u. We predict a
universal -(d-2)/r static interaction at short distances. We show that the
velocity dependent corrections to the short distance potential in the bosonic
string take the form of an infinite power series in the dimensionless variables
z = r_min^2/r^2, uz/\pi, and u^2.Comment: 16 pages, 1 figure, Revtex. Corrected factor of two in potential.
Some changes in discussio
M-Theory on (K3 X S^1)/Z_2
We analyze -theory compactified on where the
changes the sign of the three form gauge field, acts on as a parity
transformation and on K3 as an involution with eight fixed points preserving
SU(2) holonomy. At a generic point in the moduli space the resulting theory has
as its low energy limit N=1 supergravity theory in six dimensions with eight
vector, nine tensor and twenty hypermultiplets. The gauge symmetry can be
enhanced (e.g. to ) at special points in the moduli space. At other
special points in the moduli space tensionless strings appear in the theory.Comment: LaTeX file, 11 page
Semiflexible polymers: Dependence on ensemble and boundary orientations
We show that the mechanical properties of a worm-like-chain (WLC) polymer, of
contour length and persistence length \l such that t=L/\l\sim{\cal
O}(1), depend both on the ensemble and the constraint on end-orientations. In
the Helmholtz ensemble, multiple minima in free energy near persists for
all kinds of orientational boundary conditions. The qualitative features of
projected probability distribution of end to end vector depend crucially on the
embedding dimensions. A mapping of the WLC model, to a quantum particle moving
on the surface of an unit sphere, is used to obtain the statistical and
mechanical properties of the polymer under various boundary conditions and
ensembles. The results show excellent agreement with Monte-Carlo simulations.Comment: 15 pages, 15 figures; version accepted for publication in Phys. Rev.
E; one new figure and discussions adde
Observation of Successive Phase Transitions in Ferroelectric Liquid Crystal (Cs-1013) from Dielectric Measurements and a Pseudospin Type Model for Studying Ferro and Antiferroelectric Behaviour
Path integral evaluation of Dbrane amplitudes
We extend Polchinski's evaluation of the measure for the one-loop closed
string path integral to open string tree amplitudes with boundaries and
crosscaps embedded in Dbranes. We explain how the nonabelian limit of
near-coincident Dbranes emerges in the path integral formalism. We give a
careful path integral derivation of the cylinder amplitude including the
modulus dependence of the volume of the conformal Killing group.Comment: Extended version replacing hep-th/9903184, includes discussion of
nonabelian limit, Latex, 10 page
A random walk description of the heterogeneous glassy dynamics of attracting colloids
We study the heterogeneous dynamics of attractive colloidal particles close
to the gel transition using confocal microscopy experiments combined with a
theoretical statistical analysis. We focus on single particle dynamics and show
that the self part of the van Hove distribution function is not the Gaussian
expected for a Fickian process, but that it reflects instead the existence, at
any given time, of colloids with widely different mobilities. Our confocal
microscopy measurements can be described well by a simple analytical model
based on a conventional continuous time random walk picture, as already found
in several other glassy materials. In particular, the theory successfully
accounts for the presence of broad tails in the van Hove distributions that
exhibit exponential, rather than Gaussian, decay at large distance.Comment: 13 pages, 5 figs. Submitted to special issue "Classical and Quantum
Glasses" of J. Phys.: Condens. Matter; v2: response to refere
Effect of ionization/recombination processes on the electrical interactions between positively charged particles in highly collisional plasmas
The effect of ionization and recombination processes on the electrical
interactions between a pair of small charged particles in highly collisional
plasmas is discussed. In particular, it is shown that these processes suppress
the long-range attraction between positively charged particles. The condition
corresponding to the vanishing of attraction is derived. The role of the effect
for conditions of existing experiments is estimated
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