7,552 research outputs found
Non-marginally bound inhomogeneous dust collapse in higher dimensional space-time
We investigate the occurrence and nature of a naked singularity in the
gravitational collapse of an inhomogeneous dust cloud described by a
self-similar higher dimensional Tolman-Bondi space-time. Bound, marginally
bound and unbound space-times are analyzed. The degree of inhomogeneity of the
collapsing matter necessary to form a naked singularity is given.Comment: 5 pages, RevTeX 4, no figures, 2 tables, Accepted in IJMP
Chaplygin Gravitodynamics
We consider a new approach for gravity theory coupled to Chaplygin matter in
which the {\it{relativistic}} formulation of the latter is of crucial
importance. We obtain a novel form of matter with dust like density and negative pressure. We explicitly show that our results are
compatible with a relativistic generalization of the energy conservation
principle, derived here.Comment: Title changed, Revised version,N o change in conclusions, Journal
ref.: MPL A21 (2006)1511-151
Giant Goos-H\"anchen shift in Scattering: the role of interfering Localized Plasmon modes
The longitudinal and the transverse beam shifts, namely, the Goos-H\"anchen
(GH) and the Spin-Hall (SH) shifts are usually observed at planar interfaces.
It has recently been shown that the transverse SH shift may also arise due to
scattering of plane waves. Here, we show that analogous in-plane (longitudinal)
shift also exist in scattering of plane waves from micro/nano systems. We study
both the GH and the SH shifts in plasmonic metal nanoparticles/ nanostructures
and dielectric micro-particles employing a unified framework that utilizes the
transverse components of the Poynting vector of the scattered wave. The results
demonstrate that interference of neighboring resonance modes in plasmonic
nanostructures (e.g., electric dipolar and quadrupolar modes in metal spheres)
leads to giant enhancement of GH shift in scattering from such systems. We also
unravel interesting correlations between these shifts with the polarimetry
parameters, diattenuation and retardance.Comment: 4 pages, 3 figure
Effect of control procedures on the evolution of entanglement in open quantum systems
The effect of a number of mechanisms designed to suppress decoherence in open
quantum systems are studied with respect to their effectiveness at slowing down
the loss of entanglement. The effect of photonic band-gap materials and
frequency modulation of the system-bath coupling are along expected lines in
this regard. However, other control schemes, like resonance fluorescence,
achieve quite the contrary: increasing the strength of the control kills
entanglement off faster. The effect of dynamic decoupling schemes on two
qualitatively different system-bath interactions are studied in depth. Dynamic
decoupling control has the expected effect of slowing down the decay of
entanglement in a two-qubit system coupled to a harmonic oscillator bath under
non-demolition interaction. However, non-trivial phenomena are observed when a
Josephson charge qubit, strongly coupled to a random telegraph noise bath, is
subject to decoupling pulses. The most striking of these reflects the resonance
fluorescence scenario in that an increase in the pulse strength decreases
decoherence but also speeds up the sudden death of entanglement. This
demonstrates that the behaviour of decoherence and entanglement in time can be
qualitatively different in the strong-coupling non-Markovian regime
N=2 Supersymmetric Planar Particles and Magnetic Interaction from Noncommutativity
We describe a N=2 supersymmetric extension of the nonrelativistic
(2+1)-dimensional model describing particles on the noncommutative plane with
scalar (electric) and vector (magnetic) interactions.
First, we employ the N=2 superfield technique and show that in the presence
of a scalar N=2 superpotential the magnetic interaction is implied by the
presence of noncommutativity of position variables. Further, by expressing the
supersymmetric Hamiltonian as a bilinear in N=2 supercharges we obtain two
supersymmetric models with electromagnetic interactions and two different
noncanonical symplectic structures describing noncommutativity. We show that
both models are related by a map of the Seiberg-Witten type.Comment: LaTeX,12 pages.Minor corrections; version appears in PL
Symplectic embedding and Hamilton-Jacobi analysis of Proca model
Following the symplectic approach we show how to embed the Abelian Proca
model into a first-class system by extending the configuration space to include
an additional pair of scalar fields, and compare it with the improved Dirac
scheme. We obtain in this way the desired Wess-Zumino and gauge fixing terms of
BRST invariant Lagrangian. Furthermore, the integrability properties of the
second-class system described by the Abelian Proca model are investigated using
the Hamilton-Jacobi formalism, where we construct the closed Lie algebra by
introducing operators associated with the generalized Poisson brackets.Comment: 24 page
Universal Scaling Laws for Large Events in Driven Nonequilibrium Systems
For many driven-nonequilibrium systems, the probability distribution
functions of magnitude and recurrence-time of large events follow a powerlaw
indicating a strong temporal correlation. In this paper we argue why these
probability distribution functions are ubiquitous in driven nonequilibrium
systems, and we derive universal scaling laws connecting the magnitudes,
recurrence-time, and spatial intervals of large events. The relationships
between the scaling exponents have also been studied. We show that the
ion-channel current in Voltage-dependent Anion Channels obeys the universal
scaling law.Comment: 9 pages, 5 figure
The Chandrasekhar limit for quark stars
The Chandrasekhar limit for quark stars is evaluated from simple energy
balance relations, as proposed by Landau for white dwarfs or neutron stars. It
has been found that the limit for quark stars depends on, in addition to the
fundamental constants, the Bag constant.Comment: LateX fil
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