26,266 research outputs found
Probing electronic excitations in molecular conduction
We identify experimental signatures in the current-voltage (I-V)
characteristics of weakly contacted molecules directly arising from excitations
in their many electron spectrum. The current is calculated using a
multielectron master equation in the Fock space of an exact diagonalized model
many-body Hamiltonian for a prototypical molecule. Using this approach, we
explain several nontrivial features in frequently observed I-Vs in terms of a
rich spectrum of excitations that may be hard to describe adequately with
standard one-electron self-consistent field (SCF) theories.Comment: Significantly different content -- inadequacy of SCF approach
described with simple model, and a whole new class of experiments showing
gate modulated current steps discussed in terms of excitations in the
molecular many-body spac
Role of Many-particle excitations in Coulomb Blockaded Transport
We discuss the role of electron-electron and electron-phonon correlations in
current flow in the Coulomb Blockade regime, focusing specifically on
nontrivial signatures arising from the break-down of mean-field theory. By
solving transport equations directly in Fock space, we show that
electron-electron interactions manifest as gateable excitations experimentally
observed in the current-voltage characteristic. While these excitations might
merge into an incoherent sum that allows occasional simplifications, a clear
separation of excitations into slow `traps' and fast `channels' can lead to
further novelties such as negative differential resistance, hysteresis and
random telegraph signals. Analogous novelties for electron-phonon correlation
include the breakdown of commonly anticipated Stokes-antiStokes intensities,
and an anomalous decrease in phonon population upon heating due to reabsorption
of emitted phonons.Comment: 14 pages 10 figures, Invited article for the special issue on
"Conductivity of single molecules and supramolecular architectures", IOP
Journal of Physics Condensed matte
Comment on ''Understanding the Area Proposal for Extremal Black Hole Entropy''
A. Ghosh and P. Mitra made the proposal how to explain the area law for the
entropy of extreme black holes in some model calculations. I argue that their
approach implicitly operates with strongly singular geometries and says nothing
about the contribution of regular metrics of extreme black holes into the
partition function.Comment: 5 pages, ReVTeX, no figures. Expanded from the journal version to
include response to Ghosh and Mitra Reply
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
Statistics of the Kolkata Paise Restaurant Problem
We study the dynamics of a few stochastic learning strategies for the
'Kolkata Paise Restaurant' problem, where N agents choose among N equally
priced but differently ranked restaurants every evening such that each agent
tries get to dinner in the best restaurant (each serving only one customer and
the rest arriving there going without dinner that evening). We consider the
learning strategies to be similar for all the agents and assume that each
follow the same probabilistic or stochastic strategy dependent on the
information of the past successes in the game. We show that some 'naive'
strategies lead to much better utilization of the services than some relatively
'smarter' strategies. We also show that the service utilization fraction as
high as 0.80 can result for a stochastic strategy, where each agent sticks to
his past choice (independent of success achieved or not; with probability
decreasing inversely in the past crowd size). The numerical results for
utilization fraction of the services in some limiting cases are analytically
examined.Comment: 10 pages, 3 figs; accepted in New J Phy
A study of global monopole in Lyra geometry
A class of exact static solution around a global monopole resulting from the
breaking of a global S0(3) symmetry is obtained in the context of Lyra
geometry. Our solution is shown to possess an interesting feature like
wormholes space-time. It has been shown that the global monopole exerts no
gravitational force on surrounding non-relativistic matter.Comment: 6 pages, Published in Mod.Phys.Lett.A19:2785-2790,200
Local cloning of Bell states and distillable entanglement
The necessary and sufficient amount of entanglement required for cloning of
orthogonal Bell states by local operation and classical communication is
derived, and using this result, we provide here some additional examples of
reversible, as well as irreversible states.Comment: 5 pages, two columns, Latex. Few typos have been corrected. An
explanation of the teleportation map (eqn. (3) in the manuscript) has been
provide
Planar Two-particle Coulomb Interaction: Classical and Quantum Aspects
The classical and quantum aspects of planar Coulomb interactions have been
studied in detail. In the classical scenario, Action Angle Variables are
introduced to handle relativistic corrections, in the scheme of
time-independent perturbation theory. Complications arising due to the
logarithmic nature of the potential are pointed out. In the quantum case,
harmonic oscillator approximations are considered and effects of the
perturbations on the excited (oscillator) states have been analysed. In both
the above cases, the known 3+1-dimensional analysis is carried through side by
side, for a comparison with the 2+1-dimensional (planar) results.Comment: LaTex, Figures on request, e-mail:<[email protected]
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