1,100 research outputs found
Quantum Correlations in Two-Particle Anderson Localization
We predict the quantum correlations between non-interacting particles
evolving simultaneously in a disordered medium. While the particle density
follows the single-particle dynamics and exhibits Anderson localization, the
two-particle correlation develops unique features that depend on the quantum
statistics of the particles and their initial separation. On short time scales,
the localization of one particle becomes dependent on whether the other
particle is localized or not. On long time scales, the localized particles show
oscillatory correlations within the localization length. These effects can be
observed in Anderson localization of non-classical light and ultra-cold atoms.Comment: 4 pages, 4 figures, comments welcom
Bloch oscillations of Path-Entangled Photons
We show that when photons in N-particle path entangled |N,0> + |0,N> state
undergo Bloch oscillations, they exhibit a periodic transition between
spatially bunched and antibunched states. The transition occurs even when the
photons are well separated in space. We study the scaling of the
bunching-antibunching period, and show it is proportional to 1/N.Comment: An error in figure 1b of the original manuscript was corrected, and
the period was redefine
A Thousand and One Nova Outbursts
Multicycle nova evolution models have been calculated over the past twenty
years, the number being limited by numerical constraints. Here we present a
long-term evolution code that enables a continuous calculation through an
unlimited number of nova cycles for an unlimited evolution time, even up to (or
exceeding) a Hubble time. Starting with two sets of the three independent nova
parameters -- the white dwarf mass, the temperature of its isothermal core, and
the rate of mass transfer on to it -- we have followed the evolution of two
models, with initial masses of 1 and 0.65 solar masses, accretion rates
(constant throughout each calculation) of 1e-11 and 1e-9 solar-masses/yr, and
relatively high initial temperatures (as they are likely to be at the onset of
the outburst phase), through over 1000 and over 3000 cycles, respectively. The
results show that although on the short-term consecutive outbursts are almost
identical, on the long-term scale the characteristics change. This is mainly
due to the changing core temperature, which decreases very similarly to that of
a cooling white dwarf for a time, but at a slower rate thereafter. As the white
dwarf's mass continually decreases, since both models lose more mass than they
accrete, the central pressure decreases accordingly. The outbursts on the
massive white dwarf change gradually from fast to moderately fast, and the
other characteristics (velocity, abundance ratios, isotopic ratios) change,
too. Very slowly, a steady state is reached, where all characteristics, both in
quiescence and in outburst, remain almost constant. For the less massive white
dwarf accreting at a high rate, outbursts are similar throughout the evolution.Comment: To be published in MNRA
Diffusion in sparse networks: linear to semi-linear crossover
We consider random networks whose dynamics is described by a rate equation,
with transition rates that form a symmetric matrix. The long time
evolution of the system is characterized by a diffusion coefficient . In one
dimension it is well known that can display an abrupt percolation-like
transition from diffusion () to sub-diffusion (D=0). A question arises
whether such a transition happens in higher dimensions. Numerically can be
evaluated using a resistor network calculation, or optionally it can be deduced
from the spectral properties of the system. Contrary to a recent expectation
that is based on a renormalization-group analysis, we deduce that is
finite; suggest an "effective-range-hopping" procedure to evaluate it; and
contrast the results with the linear estimate. The same approach is useful for
the analysis of networks that are described by quasi-one-dimensional sparse
banded matrices.Comment: 13 pages, 4 figures, proofed as publishe
Nonlinear interactions with an ultrahigh flux of broadband entangled photons
We experimentally demonstrate sum-frequency generation (SFG) with entangled
photon-pairs, generating as many as 40,000 SFG photons per second, visible even
to the naked eye. The nonclassical nature of the interaction is exhibited by a
linear intensity-dependence of the nonlinear process. The key element in our
scheme is the generation of an ultrahigh flux of entangled photons while
maintaining their nonclassical properties. This is made possible by generating
the down-converted photons as broadband as possible, orders of magnitude wider
than the pump. This approach is readily applicable for other nonlinear
interactions, and may be applicable for various quantum-measurement tasks.Comment: 4 pages, 2 figures, Accepted to Phys. Rev. Let
The Pure Spinor Formulation of Superstrings
In this lectures we outline the construction of pure spinor superstrings. We
consider both the open and closed pure spinor superstrings in critical and
noncritical dimensions and on flat and curved target spaces with RR flux. We
exhibit the integrability properties of pure spinor superstrings on curved
backgrounds with RR fluxes.Comment: These lectures have been given in the RTN Winter School on Strings,
Supergravity and Gauge Theories, CERN (2008). 32 pages, a typo correcte
Response of discrete nonlinear systems with many degrees of freedom
We study the response of a large array of coupled nonlinear oscillators to
parametric excitation, motivated by the growing interest in the nonlinear
dynamics of microelectromechanical and nanoelectromechanical systems (MEMS and
NEMS). Using a multiscale analysis, we derive an amplitude equation that
captures the slow dynamics of the coupled oscillators just above the onset of
parametric oscillations. The amplitude equation that we derive here from first
principles exhibits a wavenumber dependent bifurcation similar in character to
the behavior known to exist in fluids undergoing the Faraday wave instability.
We confirm this behavior numerically and make suggestions for testing it
experimentally with MEMS and NEMS resonators.Comment: Version 2 is an expanded version of the article, containing detailed
steps of the derivation that were left out in version 1, but no additional
result
FUSE Measurements of Interstellar Fluorine
The source of fluorine is not well understood, although core-collapse
supernovae, Wolf-Rayet stars, and asymptotic giant branch stars have been
suggested. A search for evidence of the nu process during Type II supernovae is
presented. Absorption from interstellar F I is seen in spectra of HD 208440 and
HD 209339A acquired with the Far Ultraviolet Spectroscopic Explorer. In order
to extract the column density for F I from the line at 954 A, absorption from
H2 has to be modeled and then removed. Our analysis indicates that for H2
column densities less than about 3 x 10^20 cm^-2, the amount of F I can be
determined from lambda 954. For these two sight lines, there is no clear
indication for enhanced F abundances resulting from the nu process in a region
shaped by past supernovae.Comment: 17 pages, 4 figures, accepted for publication in Ap
Localization of Multi-Dimensional Wigner Distributions
A well known result of P. Flandrin states that a Gaussian uniquely maximizes
the integral of the Wigner distribution over every centered disc in the phase
plane. While there is no difficulty in generalizing this result to
higher-dimensional poly-discs, the generalization to balls is less obvious. In
this note we provide such a generalization.Comment: Minor corrections, to appear in the Journal of Mathematical Physic
Relativistic Hydrodynamics with General Anomalous Charges
We consider the hydrodynamic regime of gauge theories with general triangle
anomalies, where the participating currents may be global or gauged, abelian or
non-abelian. We generalize the argument of arXiv:0906.5044, and construct at
the viscous order the stress-energy tensor, the charge currents and the entropy
current.Comment: 13 pages, Revte
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