288 research outputs found
Solution of a class of one-dimensional reaction-diffusion models in disordered media
We study a one-dimensional class of reaction-diffusion models on a
parameters manifold. The equations of motion of the correlation
functions close on this manifold. We compute exactly the long-time behaviour of
the density and correlation functions for
{\it quenched} disordered systems. The {\it quenched} disorder consists of
disconnected domains of reaction. We first consider the case where the disorder
comprizes a superposition, with different probabilistic weights, of finite
segments, with {\it periodic boundary conditions}. We then pass to the case of
finite segments with {\it open boundary conditions}: we solve the ordered
dynamics on a open lattice with help of the Dynamical Matrix Ansatz (DMA) and
investigate further its disordered version.Comment: 11 pages, no figures. To appear in Phys.Rev.
Exact multipoint and multitime correlation functions of a one-dimensional model of adsorption and evaporation of dimers
In this work, we provide a method which allows to compute exactly the
multipoint and multi-time correlation functions of a one-dimensional stochastic
model of dimer adsorption-evaporation with random (uncorrelated) initial
states.
In particular explicit expressions of the two-point
noninstantaneous/instantaneous correlation functions are obtained. The
long-time behavior of these expressions is discussed in details and in various
physical regimes.Comment: 6 pages, no figur
Generating Entangled Microwave Radiation Over Two Transmission Lines
Using a superconducting circuit, the Josephson mixer, we demonstrate the
first experimental realization of spatially separated two-mode squeezed states
of microwave light. Driven by a pump tone, a first Josephson mixer generates,
out of quantum vacuum, a pair of entangled fields at different frequencies on
separate transmission lines. A second mixer, driven by a -phase shifted
copy of the first pump tone, recombines and disentangles the two fields. The
resulting output noise level is measured to be lower than for vacuum state at
the input of the second mixer, an unambiguous proof of entanglement. Moreover,
the output noise level provides a direct, quantitative measure of entanglement,
leading here to the demonstration of 6 Mebit.s (Mega entangled bits per
second) generated by the first mixer.Comment: 5 pages, 4 figures. Supplementary Information can be found here as an
ancillary fil
Quantum computing with spatially delocalized qubits
We analyze the operation of quantum gates for neutral atoms with qubits that
are delocalized in space, i.e., the computational basis states are defined by
the presence of a neutral atom in the ground state of one out of two trapping
potentials. The implementation of single qubit gates as well as a controlled
phase gate between two qubits is discussed and explicit calculations are
presented for rubidium atoms in optical microtraps. Furthermore, we show how
multi-qubit highly entangled states can be created in this scheme.Comment: 4 pages, 4 figure
Non-universal dynamics of dimer growing interfaces
A finite temperature version of body-centered solid-on-solid growth models
involving attachment and detachment of dimers is discussed in 1+1 dimensions.
The dynamic exponent of the growing interface is studied numerically via the
spectrum gap of the underlying evolution operator. The finite size scaling of
the latter is found to be affected by a standard surface tension term on which
the growth rates depend. This non-universal aspect is also corroborated by the
growth behavior observed in large scale simulations. By contrast, the
roughening exponent remains robust over wide temperature ranges.Comment: 11 pages, 7 figures. v2 with some slight correction
Bose-Einstein Condensates in Optical Quasicrystal Lattices
We analyze the physics of Bose-Einstein condensates confined in 2D
quasi-periodic optical lattices, which offer an intermediate situation between
ordered and disordered systems. First, we analyze the time-of-flight
interference pattern that reveals quasi-periodic long-range order. Second, we
demonstrate localization effects associated with quasi-disorder as well as
quasiperiodic Bloch oscillations associated with the extended nature of the
wavefunction of a Bose-Einstein condensate in an optical quasicrystal. In
addition, we discuss in detail the crossover between diffusive and localized
regimes when the quasi-periodic potential is switched on, as well as the
effects of interactions
Smoothing effect and delocalization of interacting Bose-Einstein condensates in random potentials
We theoretically investigate the physics of interacting Bose-Einstein
condensates at equilibrium in a weak (possibly random) potential. We develop a
perturbation approach to derive the condensate wavefunction for an amplitude of
the potential smaller than the chemical potential of the condensate and for an
arbitrary spatial variation scale of the potential. Applying this theory to
disordered potentials, we find in particular that, if the healing length is
smaller than the correlation length of the disorder, the condensate assumes a
delocalized Thomas-Fermi profile. In the opposite situation where the
correlation length is smaller than the healing length, we show that the random
potential can be significantly smoothed and, in the meanfield regime, the
condensate wavefunction can remain delocalized, even for very small correlation
lengths of the disorder.Comment: The word "screening" has been changed to "smoothing" to avoid
confusions with other effects discussed in the literature. This does not
affect the content of paper, nor the results, nor the physical discussio
Quantum approach to nucleation times of kinetic Ising ferromagnets
Low temperature dynamics of Ising ferromagnets under finite magnetic fields
are studied in terms of quantum spin representations of stochastic evolution
operators. These are constructed for the Glauber dynamic as well as for a
modification of this latter, introduced by K. Park {\it et al.} in Phys. Rev.
Lett. {\bf 92}, 015701 (2004). In both cases the relaxation time after a field
quench is evaluated both numerically and analytically using the spectrum gap of
the corresponding operators. The numerical work employs standard recursive
techniques following a symmetrization of the evolution operator accomplished by
a non-unitary spin rotation. The analytical approach uses low temperature
limits to identify dominant terms in the eigenvalue problem. It is argued that
the relaxation times already provide a measure of actual nucleation lifetimes
under finite fields. The approach is applied to square, triangular and
honeycomb lattices.Comment: 14 pages, 6 figure
Systemic and sex-biased regulation of OBP expression under semiochemical stimuli.
Abstract Constitutive expression of Odorant-Binding Proteins (OBPs) in antennae and other body parts has been examined mainly to infer their involvement in insect olfaction, while their regulation in response to semiochemical stimuli has remained poorly known. Previous studies of semiochemical response were basically done using electrophysiology, which integrates the response of the set of OBPs present in an antenna or sensillum, without revealing the regulation of OBPs or which ones might be involved. In this study we used boll weevil as a model and mined its OBPs by RNA-Seq to study their simultaneous antennal expression by qPCR under controlled semiochemical stimuli with aggregation pheromone and plant volatiles. In the absence of a semiochemical stimulus, 23 of 24 OBPs were constitutively expressed in the antenna in both sexes. Semiochemicals changed systemically the expression of OBPs in both sexes. There were different patterns of up- and down-regulation in female antennae for each semiochemical stimulus, consistent with female chemical ecology. On the other hand, the only response in males was down-regulation of some OBPs. We suggest that these systemic changes in OBP expression might be related to enhancing detection of the semiochemical stimuli and/or priming the olfactory system to detect other environmental chemicals
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