604 research outputs found
Lateral Effects in Fermion Antibunching
Lateral effects are analyzed in the antibunching of a beam of free
non-interacting fermions. The emission of particles from a source is
dynamically described in a 3D full quantum field-theoretical framework. The
size of the source and the detectors, as well as the temperature of the source
are taken into account and the behavior of the visibility is scrutinized as a
function of these parameters.Comment: 22 pages, 4 figure
Spectral resolution of the Liouvillian of the Lindblad master equation for a harmonic oscillator
A Lindblad master equation for a harmonic oscillator, which describes the
dynamics of an open system, is formally solved. The solution yields the
spectral resolution of the Liouvillian, that is, all eigenvalues and
eigenprojections are obtained. This spectral resolution is discussed in depth
in the context of the biorthogonal system and the rigged Hilbert space, and the
contribution of each eigenprojection to expectation values of physical
quantities is revealed. We also construct the ladder operators of the
Liouvillian, which clarify the structure of the spectral resolution.Comment: 22pages, no figure; title changed, minor corrections, references
added; minor correction
Phase diagram of neutron-rich nuclear matter and its impact on astrophysics
Dense matter as it can be found in core-collapse supernovae and neutron stars
is expected to exhibit different phase transitions which impact the matter
composition and equation of state, with important consequences on the dynamics
of core-collapse supernova explosion and on the structure of neutron stars. In
this paper we will address the specific phenomenology of two of such
transitions, namely the crust-core solid-liquid transition at sub-saturation
density, and the possible strange transition at super-saturation density in the
presence of hyperonic degrees of freedom. Concerning the neutron star
crust-core phase transition at zero and finite temperature, it will be shown
that, as a consequence of the presence of long-range Coulomb interactions, the
equivalence of statistical ensembles is violated and a clusterized phase is
expected which is not accessible in the grand-canonical ensemble. A specific
quasi-particle model will be introduced to illustrate this anomalous
thermodynamics and some quantitative results relevant for the supernova
dynamics will be shown. The opening of hyperonic degrees of freedom at higher
densities corresponding to the neutron stars core modifies the equation of
state. The general characteristics and order of phase transitions in this
regime will be analyzed in the framework of a self-consistent mean-field
approach.Comment: Invited Talk given at the 11th International Conference on
Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1,
2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference
Series (JPCS
Initial wave packets and the various power-law decreases of scattered wave packets at long times
The long time behavior of scattered wave packets from a
finite-range potential is investigated, by assuming to be
initially located outside the potential. It is then shown that can
asymptotically decrease in the various power laws at long time, according to
its initial characteristics at small momentum. As an application, we consider
the square-barrier potential system and demonstrate that exhibits
the asymptotic behavior , while another behavior like can
also appear for another .Comment: 5 pages, 1 figur
The various power decays of the survival probability at long times for free quantum particle
The long time behaviour of the survival probability of initial state and its
dependence on the initial states are considered, for the one dimensional free
quantum particle. We derive the asymptotic expansion of the time evolution
operator at long times, in terms of the integral operators. This enables us to
obtain the asymptotic formula for the survival probability of the initial state
, which is assumed to decrease sufficiently rapidly at large .
We then show that the behaviour of the survival probability at long times is
determined by that of the initial state at zero momentum . Indeed,
it is proved that the survival probability can exhibit the various power-decays
like for an arbitrary non-negative integers as ,
corresponding to the initial states with the condition as .Comment: 15 pages, to appear in J. Phys.
A Dynamical Mean Field Theory for the Study of Surface Diffusion Constants
We present a combined analytical and numerical approach based on the Mori
projection operator formalism and Monte Carlo simulations to study surface
diffusion within the lattice-gas model. In the present theory, the average jump
rate and the susceptibility factor appearing are evaluated through Monte Carlo
simulations, while the memory functions are approximated by the known results
for a Langmuir gas model. This leads to a dynamical mean field theory (DMF) for
collective diffusion, while approximate correlation effects beyond DMF are
included for tracer diffusion. We apply our formalism to three very different
strongly interacting systems and compare the results of the new approach with
those of usual Monte Carlo simulations. We find that the combined approach
works very well for collective diffusion, whereas for tracer diffusion the
influence of interactions on the memory effects is more prominent.Comment: 13 pages LaTeX and 6 PostScript figures, style files included. To
appear in Surface Science Letter
Unusual conductance collapse in one-dimensional quantum structures
We report an unusual insulating state in one-dimensional quantum wires with a
non-uniform confinement potential. The wires consist of a series of closely
spaced split gates in high mobility GaAs/AlGaAs heterostructures. At certain
combinations of wire widths, the conductance abruptly drops over three orders
of magnitude, to zero on a linear scale. Two types of collapse are observed,
one occurring in multi-subband wires in zero magnetic field and one in single
subband wires in an in-plane field. The conductance of the wire in the collapse
region is thermally activated with an energy of the order of 1 K. At low
temperatures, the conductance shows a steep rise beyond a threshold DC
source-drain voltage of order 1 mV, indicative of a gap in the density of
states. Magnetic depopulation measurements show a decrease in the carrier
density with lowering temperature. We discuss these results in the context of
many-body effects such as charge density waves and Wigner crystallization in
quantum wires.Comment: 5 pages, 5 eps figures, revte
Cathdodoluminescence study of meteoritic pre-solar nanodiamonds: An implication for origin of diamond particles in NGC 7027 planetary nebula
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