23,692 research outputs found
Three flavour Quark matter in chiral colour dielectric model
We investigate the properties of quark matter at finite density and
temperature using the nonlinear chiral extension of Colour Dielectric Model
(CCM). Assuming that the square of the meson fields devlop non- zero vacuum
expectation value, the thermodynamic potential for interacting three flavour
matter has been calculated. It is found that remain zero
in the medium whereas changes in the medium. As a result, and
quark masses decrease monotonically as the temperature and density of the quark
matter is increased.In the present model, the deconfinement density and
temperature is found to be lower compared to lattice results. We also study the
behaviour of pressure and energy density above critical temperature.Comment: Latex file. 5 figures available on request. To appear in Phys. Rev.
Algebraic geometric methods for the stabilizability and reliability of multivariable and of multimode systems
The extent to which feedback can alter the dynamic characteristics (e.g., instability, oscillations) of a control system, possibly operating in one or more modes (e.g., failure versus nonfailure of one or more components) is examined
Warm stellar matter with neutrino trapping
The properties of hybrid stars formed by hadronic and quark matter in
beta-equilibrium at fixed entropies are described by appropriate equations of
state (EOS) in the framework of relativistic mean-field theory. In this work we
include the possibility of neutrino trapped EOS and compare the star properties
with the ones obtained after deleptonization, when neutrinos have already
diffused out. We use the nonlinear Walecka model for the hadron matter with two
different sets for the hyperon couplings and the MIT Bag and the
Nambu-Jona-Lasinio models for the quark matter. The phase transition to a
deconfined quark phase is investigated. Depending on the model and the
parameter set used, the mixed phase may or may not exist in the EOS at high
densities.
The star properties are calculated for each equation of state. The maximum
mass stellar configurations obtained within the NJL have larger masses than the
ones obtained within the Bag model. The Bag model predicts a mixed phase in the
interior of the most massive stable stars while, depending on the hyperon
couplings, the NJL model predicts a mixed phase or pure quark matter. Comparing
with neutrino free stars, the maximum allowed baryonic masses for protoneutron
stars are larger for the Bag model and
larger for the NJL model when neutrino trapping is imposed.Comment: 8 pages, 8 figures, 1 tabl
Naked Singularities in the Charged Vaidya-deSitter Spacetime
We study the occurrence of naked singularities in the spherically symmetric
collapse of a charged null fluid in an expanding deSitter background - a piece
of charged Vaidya-deSitter spacetime. The necessary conditions for the
formation of a naked singularity are found. The results for the uncharged
solutions can be recovered from our analysis.Comment: 8 pages, latex, no figure
Scheduling to minimize the coefficient of variation
Cataloged from PDF version of article.In this paper, we address the problem of uninterruptedly scheduling a set of independent jobs that are ready at time
zero with the objective of minimizing the coefficient of variation (CV) of their completion times. We first show that, for
high processing time values of the longest job, a variance (V) minimizing schedule also minimizes CV. Using this
equivalence, we next demonstrate the invalidity of an earlier conjecture about the structure of a CV-optimal schedule and
proceed to establish the NP-hardness of the CV problem. Finally, drawing from our prior work on the V problem, we
provide a pseudo-polynomial dynamic programming algorithm for the solution of the CV problem
Geometry and topology of two kinds of extreme Reissner-Nordstrm-anti-de Sitter black holes
Different geometrical and topological properties have been shown for two
kinds of extreme Reissner-Nordstrm-anti-de Sitter black holes. The
relationship between the geometrical properties and the intrinsic
thermodynamical properties has been made explicit.Comment: Latex, 12 pages, 4 figure
Solitons in 1+1 Dimensional Gauged Sigma Models
We study soliton solutions in 1+1 dimensional gauged sigma models, obtained
by dimensional reduction from its 2+1 dimensional counterparts. We show that
the Bogomol'nyi bound of these models can be expressed in terms of two
conserved charges in a similar way to that of the BPS dyons in 3+1 dimensions.
Purely magnetic vortices of the 2+1 dimensional completely gauged sigma model
appear as charged solitons in the corresponding 1+1 dimensional theory. The
scale invariance of these solitons is also broken because of the dimensional
reduction. We obtain exact static soliton solutions of these models saturating
the Bogomol'nyi bound.Comment: 21 pages, RevTeX, minor changes, version to appear in Physical Review
Generating dynamical black hole solutions
We prove a theorem that characterizes a large family of non-static solutions
to Einstein equations, representing, in general, spherically symmetric Type II
fluid. It is shown that the best known dynamical black hole solutions to
Einstein equations are particular cases from this family. Thus we extend a
recent work of Salgado \cite{ms} to non-static case. The spherically symmetric
static black hole solutions, for Type I fluid, are also retrieved.Comment: 8 Pages, RevTe
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