18,038 research outputs found
Non Equilibrium Noise as a Probe of the Kondo Effect in Mesoscopic Wires
We study the non-equilibrium noise in mesoscopic diffusive wires hosting
magnetic impurities. We find that the shot-noise to current ratio develops a
peak at intermediate source-drain biases of the order of the Kondo temperature.
The enhanced impurity contribution at intermediate biases is also manifested in
the effective distribution. The predicted peak represents increased inelastic
scattering rate at the non-equilibrium Kondo crossover.Comment: 4+ pages, 4 figures, published versio
Quantum coherence engineering in the integer quantum Hall regime
We present an experiment where the quantum coherence in the edge states of
the integer quantum Hall regime is tuned with a decoupling gate. The coherence
length is determined by measuring the visibility of quantum interferences in a
Mach-Zehnder interferometer as a function of temperature, in the quantum Hall
regime at filling factor two. The temperature dependence of the coherence
length can be varied by a factor of two. The strengthening of the phase
coherence at finite temperature is shown to arise from a reduction of the
coupling between co-propagating edge states. This opens the way for a strong
improvement of the phase coherence of Quantum Hall systems. The decoupling gate
also allows us to investigate how inter-edge state coupling influence the
quantum interferences' dependence on the injection bias. We find that the
finite bias visibility can be decomposed into two contributions: a Gaussian
envelop which is surprisingly insensitive to the coupling, and a beating
component which, on the contrary, is strongly affected by the coupling.Comment: 4 pages, 5 figure
Global Existence Results and Uniqueness for Dislocation Equations
We are interested in nonlocal Eikonal Equations arising in the study of the
dynamics of dislocations lines in crystals. For these nonlocal but also non
monotone equations, only the existence and uniqueness of Lipschitz and
local-in-time solutions were available in some particular cases. In this paper,
we propose a definition of weak solutions for which we are able to prove the
existence for all time. Then we discuss the uniqueness of such solutions in
several situations, both in the monotone and non monotone case
On a zero speed sensitive cellular automaton
Using an unusual, yet natural invariant measure we show that there exists a
sensitive cellular automaton whose perturbations propagate at asymptotically
null speed for almost all configurations. More specifically, we prove that
Lyapunov Exponents measuring pointwise or average linear speeds of the faster
perturbations are equal to zero. We show that this implies the nullity of the
measurable entropy. The measure m we consider gives the m-expansiveness
property to the automaton. It is constructed with respect to a factor dynamical
system based on simple "counter dynamics". As a counterpart, we prove that in
the case of positively expansive automata, the perturbations move at positive
linear speed over all the configurations
A Search for Dense Molecular Gas in High Redshift Infrared-Luminous Galaxies
We present a search for HCN emission from four high redshift far infrared
(IR) luminous galaxies. Current data and models suggest that these high IR
luminous galaxies represent a major starburst phase in the formation of
spheroidal galaxies, although many of the sources also host luminous active
galactic nuclei (AGN), such that a contribution to the dust heating by the AGN
cannot be precluded. HCN emission is a star formation indicator, tracing dense
molecular hydrogen gas within star-forming molecular clouds (n(H) cm). HCN luminosity is linearly correlated with IR luminosity for
low redshift galaxies, unlike CO emission which can also trace gas at much
lower density. We report a marginal detection of HCN (1-0) emission from the
QSO J1409+5628, with a velocity integrated line luminosity of
K km s pc, while we obtain
3 upper limits to the HCN luminosity of the QSO J0751+2716 of
K km s pc, K km s pc for the starburst galaxy
J1401+0252, and K km s pc for the QSO J1148+5251. We compare the HCN data on these sources, plus three
other high- IR luminous galaxies, to observations of lower redshift
star-forming galaxies. The values of the HCN/far-IR luminosity ratios (or
limits) for all the high sources are within the scatter of the relationship
between HCN and far-IR emission for low star-forming galaxies (truncated).Comment: aastex format, 4 figures. to appear in the Astrophysical Journal;
Revised lens magnification estimate for 1401+025
Classical symmetric functions in superspace
We present the basic elements of a generalization of symmetric function
theory involving functions of commuting and anticommuting (Grassmannian)
variables. These new functions, called symmetric functions in superspace, are
invariant under the diagonal action of the symmetric group on the sets of
commuting and anticommuting variables. In this work, we present the superspace
extension of the classical bases, namely, the monomial symmetric functions, the
elementary symmetric functions, the completely symmetric functions, and the
power sums. Various basic results, such as the generating functions for the
multiplicative bases, Cauchy formulas, involution operations as well as the
combinatorial scalar product are also generalized.Comment: 21 pages, this supersedes the first part of math.CO/041230
Chains of infinite order, chains with memory of variable length, and maps of the interval
We show how to construct a topological Markov map of the interval whose
invariant probability measure is the stationary law of a given stochastic chain
of infinite order. In particular we caracterize the maps corresponding to
stochastic chains with memory of variable length. The problem treated here is
the converse of the classical construction of the Gibbs formalism for Markov
expanding maps of the interval
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