32,795 research outputs found
Dipolar gases in quasi one-dimensional geometries
We analyze the physics of cold dipolar gases in quasi one-dimensional
geometries, showing that the confinement-induced scattering resonances produced
by the transversal trapping are crucially affected by the dipole-dipole
interaction. As a consequence, the dipolar interaction may drastically change
the properties of quasi-1D dipolar condensates, even for situations in which
the dipolar interaction would be completely overwhelmed by the short-range
interactions in a 3D environment.Comment: 4 pages, 3 eps figure
Project of a superfluid He3 detector for direct detection of non-baryonic dark matter : MACHe3
MACHe3 (MAtrix of Cells of superfluid Helium 3) is a project of non-baryonic
Dark Matter search using superfluid He3 as sensitive medium. Simulations on a
high granularity matrix show very good rejection against background events.
First results on a prototype cell are very encouraging. Neutron detection has
been highlighted as well as cosmic muon detection. A phenomenological study has
been done with the DarkSUSY code to investigate complementarity of MACHe3 with
existing Dark Matter detectors.Comment: 5 pages, 5 figures, to appear in Proceedings of the 4th Marseille
International Cosmology Conferenc
Magnetic Properties of the Metamagnet Ising Model in a three-dimensional Lattice in a Random and Uniform Field
By employing the Monte Carlo technique we study the behavior of Metamagnet
Ising Model in a random field. The phase diagram is obtained by using the
algorithm of Glaubr in a cubic lattice of linear size with values ranging
from 16 to 42 and with periodic boundary conditions.Comment: 4 pages, 6 figure
Resistively detected nuclear magnetic resonance via a single InSb two-dimensional electron gas at high temperature
We report on the demonstration of the resistively detected nuclear magnetic
resonance (RDNMR) of a single InSb two-dimensional electron gas (2DEG) at
elevated temperatures up to 4 K. The RDNMR signal of 115In in the simplest
pseudospin quantum Hall ferromagnet triggered by a large direct current shows a
peak-dip line shape, where the nuclear relaxation time T1 at the peak and the
dip is different but almost temperature independent. The large Zeeman,
cyclotron, and exchange energy scales of the InSb 2DEG contribute to the
persistence of the RDNMR signal at high temperatures.Comment: 11pages,3figure
Resonant x-ray scattering study on multiferroic BiMnO3
Resonant x-ray scattering is performed near the Mn K-absorption edge for an
epitaxial thin film of BiMnO3. The azimuthal angle dependence of the resonant
(003) peak (in monoclinic indices) is measured with different photon
polarizations; for the channel a 3-fold symmetric oscillation
is observed in the intensity variation, while the scattering
intensity remains constant. These features are accounted for in terms of the
peculiar ordering of the manganese 3d orbitals in BiMnO3. It is demonstrated
that the resonant peak persists up to 770 K with an anomaly around 440 K; these
high and low temperatures coincide with the structural transition temperatures,
seen in bulk, with and without a symmetry change, respectively. A possible
relationship of the orbital order with the ferroelectricity of the system is
discussed.Comment: 14 pages, 4 figure
Universal optimal broadband photon cloning and entanglement creation in one dimensional atoms
We study an initially inverted three-level atom in the lambda configuration
embedded in a waveguide, interacting with a propagating single-photon pulse.
Depending on the temporal shape of the pulse, the system behaves either as an
optimal universal cloning machine, or as a highly efficient deterministic
source of maximally entangled photon pairs. This quantum transistor operates
over a wide range of frequencies, and can be implemented with today's
solid-state technologies.Comment: 5 pages, 3 figure
Soft Spheres Make More Mesophases
We use both mean-field methods and numerical simulation to study the phase
diagram of classical particles interacting with a hard-core and repulsive, soft
shoulder. Despite the purely repulsive interaction, this system displays a
remarkable array of aggregate phases arising from the competition between the
hard-core and shoulder length scales. In the limit of large shoulder width to
core size, we argue that this phase diagram has a number of universal features,
and classify the set of repulsive shoulders that lead to aggregation at high
density. Surprisingly, the phase sequence and aggregate size adjusts so as to
keep almost constant inter-aggregate separation.Comment: 4 pages, 2 included figure
Structure factor and dynamics of the helix-coil transition
Thermodynamical properties of the helix-coil transition were successfully
described in the past by the model of Lifson, Poland and Sheraga. Here we
compute the corresponding structure factor and show that it possesses a
universal scaling behavior near the transition point, even when the transition
is of first order. Moreover, we introduce a dynamical version of this model,
that we solve numerically. A Langevin equation is also proposed to describe the
dynamics of the density of hydrogen bonds. Analytical solution of this equation
shows dynamical scaling near the critical temperature and predicts a gelation
phenomenon above the critical temperature. In the case when comparison of the
two dynamical approaches is possible, the predictions of our phenomenological
theory agree with the results of the Monte Carlo simulations.Comment: 11 pages, 7 figure
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