59,095 research outputs found
Dynamical instabilities in density-dependent hadronic relativistic models
Unstable modes in asymmetric nuclear matter (ANM) at subsaturation densities
are studied in the framework of relativistic mean-field density-dependent
hadron models. The size of the instabilities that drive the system are
calculated and a comparison with results obtained within the non-linear Walecka
model is presented. The distillation and anti-distillation effects are
discussed.Comment: 8 pages, 8 Postscript figures. Submitted for publication in Phys.
Rev.
Out-of-equilibrium states and quasi-many-body localization in polar lattice gases
The absence of energy dissipation leads to an intriguing out-of-equilibrium
dynamics for ultracold polar gases in optical lattices, characterized by the
formation of dynamically-bound on-site and inter-site clusters of two or more
particles, and by an effective blockade repulsion. These effects combined with
the controlled preparation of initial states available in cold gases
experiments can be employed to create interesting out-of-equilibrium states.
These include quasi-equilibrated effectively repulsive 1D gases for attractive
dipolar interactions and dynamically-bound crystals. Furthermore,
non-equilibrium polar lattice gases can offer a promising scenario for the
study of many-body localization in the absence of quenched disorder. This
fascinating out-of-equilibrium dynamics for ultra-cold polar gases in optical
lattices may be accessible in on-going experiments.Comment: 5+1 pages, 4+1 figure
An effective many-body theory for strongly interacting polar molecules
We derive a general effective many-body theory for bosonic polar molecules in
strong interaction regime, which cannot be correctly described by previous
theories within the first Born approximation. The effective Hamiltonian has
additional interaction terms, which surprisingly reduces the anisotropic
features of dipolar interaction near the shape resonance regime. In the 2D
system with dipole moment perpendicular to the plane, we find that the phonon
dispersion scales as \sqrt{|\bfp|} in the low momentum (\bfp) limit,
showing the same low energy properties as a 2D charged Bose gas with Coulomb
() interactions.Comment: Same as published version (11 pages, 2 figure
Exoplanets: Gaia and the importance of ground based spectroscopy follow-up
The search for extrasolar planets has developed rapidly and, today, more than
1700 planets have been found orbiting stars. Thanks to Gaia, we will collect
high-accuracy astrometric orbits of thousands of new low-mass celestial
objects, such as extra-solar planets and brown dwarfs. These measurements in
combination with spectroscopy and with present day and future extrasolar planet
search programs (like HARPS, ESPRESSO) will have a crucial contribution to
several aspects of planetary astrophysics (formation theories, dynamical
evolution, etc.). Moreover, Gaia will have a strong contribution on the stellar
chemical and kinematic characterisation studies. In this paper we present a
short overview of the importance of Gaia in the context of exoplanet research.
As preparatory work for Gaia, we will then present a study where we derived
stellar parameters for a sample of field giant stars
Exponential Convergence Towards Stationary States for the 1D Porous Medium Equation with Fractional Pressure
We analyse the asymptotic behaviour of solutions to the one dimensional
fractional version of the porous medium equation introduced by Caffarelli and
V\'azquez, where the pressure is obtained as a Riesz potential associated to
the density. We take advantage of the displacement convexity of the Riesz
potential in one dimension to show a functional inequality involving the
entropy, entropy dissipation, and the Euclidean transport distance. An argument
by approximation shows that this functional inequality is enough to deduce the
exponential convergence of solutions in self-similar variables to the unique
steady states
Comment on "Theory and computer simulation for the equation of state of additive hard-disk fluid mixtures"
A flaw in the comparison between two different theoretical equations of state
for a binary mixture of additive hard disks and Monte Carlo results, as
recently reported in C. Barrio and J. R. Solana, Phys. Rev. E 63, 011201
(2001), is pointed out. It is found that both proposals, which require the
equation of state of the single component system as input, lead to comparable
accuracy but the one advocated by us [A. Santos, S. B. Yuste, and M. L\'{o}pez
de Haro, Mol. Phys. 96, 1 (1999)] is simpler and complies with the exact limit
in which the small disks are point particles.Comment: 4 pages, including 1 figur
Antiresonance and interaction-induced localization in spin and qubit chains with defects
We study a spin chain with an anisotropic XXZ coupling in an external field.
Such a chain models several proposed types of a quantum computer. The chain
contains a defect with a different on-site energy. The interaction between
excitations is shown to lead to two-excitation states localized next to the
defect. In a resonant situation scattering of excitations on each other might
cause decay of an excitation localized on the defect. We find that destructive
quantum interference suppresses this decay. Numerical results confirm the
analytical predictions.Comment: Updated versio
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