22,955 research outputs found
Thermodynamic Geometry of the Born-Infeld-anti-de Sitter black holes
Thermodynamic geometry is applied to the Born-Infeld-anti-de Sitter black
hole (BIAdS) in the four dimensions, which is a nonlinear generalization of the
Reissner-Norstr\"Aom-AdS black hole (RNAdS). We compute the Weinhold as well as
the Ruppeiner scalar curvature and find that the singular points are not the
same with the ones obtained using the heat capacity. Legendre-invariant metric
proposed by Quevedo and the metric obtained by using the free energy as the
thermodynamic potential are obtained and the corresponding scalar curvatures
diverge at the Davies points.Comment: Latex,19 pages,14 figure
Inherent properties of binary tetrahedral semiconductors
A new approach utilising the concept of ionic charge theory has been used to
explain the inherent properties such as lattice thermal conductivity and bulk
modulus of 3,5 and 2,6 semiconductors. The lattice thermal conductivity of
these semiconductors exhibit a linear relationship when plotted on a log scale
against the nearest neighbour distance but fall on two straight lines according
to the product of the ionic charge of the compounds. On the basis of this
result a simple relationship of lattice thermal conductivity with bulk modulus
is proposed and used to estimate the bulk modulus of these semiconductors. A
fairly good agreement has been found between the experimantal and calculated
values of these parameters for zinc blende structured solids.Comment: 6 pages, 19 reference
SEMI-SUPERVISED CLASSIFICATION OF LAND COVER BASED ON SPECTRAL REFLECTANCE DATA EXTRACTED FROM LISS IV IMAGE
A methodology is proposed for extracting information on land cover based on hyperspectral reflectance data derived from satellite image, without supervising with ground truth. The reflectance percentage, being a characteristic feature of the ground object acts as an indirect guidance to the classification and hence the method is named semi-supervised classification. It is tried with IRS LISS IV image of a specific part of southern West Bengal, India. At least three categories, viz. vegetation, waterbody and open land are distinctly identified with the present technique. It is hoped that a method like this is more useful in the analysis of hyperspectral imagery, which is an area of upthrust in future. 1
On Dimer Models and Closed String Theories
We study some aspects of the recently discovered connection between dimer
models and D-brane gauge theories. We argue that dimer models are also
naturally related to closed string theories on non compact orbifolds of \BC^2
and \BC^3, via their twisted sector R charges, and show that perfect
matchings in dimer models correspond to twisted sector states in the closed
string theory. We also use this formalism to study the combinatorics of some
unstable orbifolds of \BC^2.Comment: 1 + 25 pages, LaTeX, 11 epsf figure
Leptogenesis bound on neutrino masses in left-right symmetric models with spontaneous D-parity violation
We study the baryogenesis via leptogenesis in a class of left-right symmetric
models, in which -parity is broken spontaneously. We first discuss the
consequence of the spontaneous -parity breaking on the neutrino masses. Than
we study the lepton asymmetry in various cases, from the decay of right handed
neutrino as well as the triplet Higgs, depending on their relative masses they
acquire from the symmetry breaking pattern. The leptogenesis bound on their
masses are discussed by taking into account the low energy neutrino oscillation
data. It is shown that a TeV scale leptogenesis is viable if there are
additional sources of CP violation like domain wall originating from the
spontaneous -parity violation.Comment: 32 pages (revtex), 12 eps figures, clarifications are added in
section VII, A new section VIII is added, useful references are added.
Journal version, To appear in Phys. Rev.
Closed String Tachyons on C/Z_N
We analyse the condensation of closed string tachyons on the
orbifold. We construct the potential for the tachyons upto the quartic
interaction term in the large limit. In this limit there are near marginal
tachyons. The quartic coupling for these tachyons is calculated by subtracting
from the string theory amplitude for the tachyons, the contributions from the
massless exchanges, computed from the effective field theory. We argue that
higher point interaction terms are are also of the same order in 1/N as the
quartic term and are necessary for existence of the minimum of the tachyon
potential that is consistent with earlier analysis.Comment: 19 pages, 1 figure; comments added about dependence of contact
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Investigation into the limits of perturbation theory at low Q^2 using HERA deep inelastic scattering data
A phenomenological study of the final combined HERA data on inclusive deep
inelastic scattering (DIS) has been performed. The data are presented and
investigated for a kinematic range extending from values of the four-momentum
transfer, , above 10 GeV down to the lowest values observable at
HERA of = 0.045 GeV and Bjorken , = 6
10. The data are well described by fits based on perturbative quantum
chromodynamics (QCD) using collinear factorisation and evolution of the parton
densities encompassed in the DGLAP formalism from the highest down to
of a few GeV. The Regge formalism can describe the data up to 0.65 GeV. The complete data set can be described by a new fit
using the ALLM parameterisation. The region between the Regge and the
perturbative QCD regimes is of particular interest.Comment: 38 pages, 13 figure
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