32,978 research outputs found
Nonequilibrium Steady State Driven by a Nonlinear Drift Force
We investigate the properties of the nonequilibrium steady state for the
stochastic system driven by a nonlinear drift force and influenced by noises
which are not identically and independently distributed. The nonequilibrium
steady state (NESS) current results from a residual part of the drift force
which is not cancelled by the diffusive action of noises. From our previous
study for the linear drift force the NESS current was found to circulate on the
equiprobability surface with the maximum at a stable fixed point of the drift
force. For the nonlinear drift force, we use the perturbation theory with
respect to the cubic and quartic coefficients of the drift force. We find an
interesting potential landscape picture where the probability maximum shifts
from the fixed point of the drift force and, furthermore, the NESS current has
a nontrivial circulation which flows off the equiprobability surface and has
various centers not located at the probability maximum. The theoretical result
is well confirmed by the computer simulation.Comment: 10 pages, 4 figure
Reply to Catalán : double-proton-transfer dynamics of photo-excited 7-azaindole dimers
The letter by Catalán (1) is concerned with the nature of double-proton transfer in dimers of 7-azaindole (7-AI), and the pertinent issue is whether or not the reaction is concerted. The subject is not new, and, for organic reactions, it has been discussed in the literature for decades. It is now understood that the concerted/consecutive mechanism has to be defined based on the timescale of the vibration motions and the family of coherent trajectories involved (ref. 2 and references therein). For double-proton transfer in isolated dimers, this timescale criterion has been invoked, and, as supported by a variety of time-resolved experiments in several groups and also by theory (ref. 3 and references therein), the conclusion is that the reaction is not concerted on the timescale of the vibrations involved; Catalán and some researchers (see ref. 3) assert that the two protons move in exact concert, maintaining the C_(2h) symmetry at all times
Multidimensional Bosonization
Bosonization of degenerate fermions yields insight both into Landau Fermi
liquids, and into non-Fermi liquids. We begin our review with a pedagogical
introduction to bosonization, emphasizing its applicability in spatial
dimensions greater than one. After a brief historical overview, we present the
essentials of the method. Well known results of Landau theory are recovered,
demonstrating that this new tool of many-body theory is robust. Limits of
multidimensional bosonization are tested by considering several examples of
non-Fermi liquids, in particular the composite fermion theory of the
half-filled Landau level. Nested Fermi surfaces present a different challenge,
and these may be relevant in the cuprate superconductors. We conclude by
discussing the future of multidimensional bosonization.Comment: 91 pages, 15 eps figures, LaTeX. Minor changes to match the published
versio
Light-cone Quantum Mechanics of the Eleven-dimensional Superparticle
The linearized interactions of eleven-dimensional supergravity are obtained
in a manifestly supersymmetric light-cone gauge formalism. These vertices are
used to calculate certain one-loop processes involving external gravitini,
antisymmetric three-form potentials and gravitons, thereby determining some
protected terms in the effective action of M-theory compactified on a
two-torus.Comment: 31 pages, harvmac (b); A minor TeX error correcte
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