8,896 research outputs found
Statistical correlations of an anyon liquid at low temperatures
Using a proposed generalization of the pair distribution function for a gas
of non-interacting particles obeying fractional exclusion statistics in
arbitrary dimensionality, we derive the statistical correlations in the
asymptotic limit of vanishing or low temperature. While Friedel-like
oscillations are present in nearly all non-bosonic cases at T=0, they are
characterized by exponential damping at low temperature. We discuss the
dependence of these features on dimensionality and on the value of the
statistical parameter alpha.Comment: to appear in Phys. Chem. Liquid
Spatial fluctuations in an optical parametric oscillator below threshold with an intracavity photonic crystal
We show how to control spatial quantum correlations in a multimode degenerate
optical parametric oscillator type I below threshold by introducing a spatially
inhomogeneous medium, such as a photonic crystal, in the plane perpendicular to
light propagation. We obtain the analytical expressions for all the
correlations in terms of the relevant parameters of the problem and study the
number of photons, entanglement, squeezing, and twin beams. Considering
different regimes and configurations we show the possibility to tune the
instability thresholds as well as the quantumness of correlations by breaking
the translational invariance of the system through a photonic crystal
modulation.Comment: 12 pages, 7 figure
A Three Dimensional Lattice of Ion Traps
We propose an ion trap configuration such that individual traps can be
stacked together in a three dimensional simple cubic arrangement. The isolated
trap as well as the extended array of ion traps are characterized for different
locations in the lattice, illustrating the robustness of the lattice of traps
concept. Ease in the addressing of ions at each lattice site, individually or
simultaneously, makes this system naturally suitable for a number of
experiments. Application of this trap to precision spectroscopy, quantum
information processing and the study of few particle interacting system are
discussed.Comment: 4 pages, 4 Figures. Fig 1 appears as a composite of 1a, 1b, 1c and
1d. Fig 2 appears as a composite of 2a, 2b and 2
Thomas-Fermi Method For Particles Obeying Generalized Exclusion Statistics
We use the Thomas-Fermi method to examine the thermodynamics of particles
obeying Haldane exclusion statistics. Specifically, we study
Calogero-Sutherland particles placed in a given external potential in one
dimension. For the case of a simple harmonic potential (constant density of
states), we obtain the exact one-particle spatial density and a {\it closed}
form for the equation of state at finite temperature, which are both new
results. We then solve the problem of particles in a potential
(linear density of states) and show that Bose-Einstein condensation does not
occur for any statistics other than bosons.Comment: 10 pages (TeX), 2 figures available upon reques
Comment on ``the Klein-Gordon Oscillator''
The different ways of description of the particle with oscillator-like
interaction are considered. The results are in conformity with the previous
paper of S. Bruce and P. Minning.Comment: LaTeX file, 5p
Kinetic Energy Density Study of Some Representative Semilocal Kinetic Energy Functionals
There is a number of explicit kinetic energy density functionals for
non-interacting electron systems that are obtained in terms of the electron
density and its derivatives. These semilocal functionals have been widely used
in the literature. In this work we present a comparative study of the kinetic
energy density of these semilocal functionals, stressing the importance of the
local behavior to assess the quality of the functionals. We propose a quality
factor that measures the local differences between the usual orbital-based
kinetic energy density distributions and the approximated ones, allowing to
ensure if the good results obtained for the total kinetic energies with these
semilocal functionals are due to their correct local performance or to error
cancellations. We have also included contributions coming from the laplacian of
the electron density to work with an infinite set of kinetic energy densities.
For all the functionals but one we have found that their success in the
evaluation of the total kinetic energy are due to global error cancellations,
whereas the local behavior of their kinetic energy density becomes worse than
that corresponding to the Thomas-Fermi functional.Comment: 12 pages, 3 figure
Two-particle photoemission from strongly correlated systems: A dynamical-mean field approach
We study theoretically the simultaneous, photo-induced two-particle
excitations of strongly correlated systems on the basis of the Hubbard model.
Under certain conditions specified in this work, the corre- sponding transition
probability is related to the two-particle spectral function which we calculate
using three different methods: the dynamical-mean field theory combined with
quantum Monte Carlo (DMFT- QMC) technique, the first order perturbation theory
and the ladder approximations. The results are analyzed and compared for
systems at the verge of the metal-insulator transitions. The dependencies on
the electronic correlation strength and on doping are explored. In addition,
the account for the orbital degeneracy allows an insight into the influence of
interband correlations on the two particle excitations. A suitable experimental
realization is discussed.Comment: 25 pp, 10 figs. to be published in PR
One-dimensional non-interacting fermions in harmonic confinement: equilibrium and dynamical properties
We consider a system of one-dimensional non-interacting fermions in external
harmonic confinement. Using an efficient Green's function method we evaluate
the exact profiles and the pair correlation function, showing a direct
signature of the Fermi statistics and of the single quantum-level occupancy. We
also study the dynamical properties of the gas, obtaining the spectrum both in
the collisionless and in the collisional regime. Our results apply as well to
describe a one-dimensional Bose gas with point-like hard-core interactions.Comment: 11 pages, 5 figure
Phase transitions near black hole horizons
The Reissner-Nordstrom black hole in four dimensions can be made unstable
without violating the dominant energy condition by introducing a real massive
scalar with non-renormalizable interactions with the gauge field. New stable
black hole solutions then exist with greater entropy for fixed mass and charge
than the Reissner-Nordstrom solution. In these new solutions, the scalar
condenses to a non-zero value near the horizon. Various generalizations of
these hairy black holes are discussed, and an attempt is made to characterize
when black hole hair can occur.Comment: 30 pages, 6 figures. v2: minor corrections, references adde
Ester biosynthesis in kiwifruit: from genes to enzymes to pathways
The distinctive flavours of different kiwifruit (Actinidia) genotypes are determined by a unique combination of volatile compounds. We are using a genomics approach to identify genes responsible for the production of esters in kiwifruit. From an extensive database of kiwifruit ESTs we have mined acyl transferase genes, including putative alcohol acyl transferases predicted to be involved in the final step of ester biosynthesis. In this paper we report the first functional characterisation of two acyl transferases in kiwifruit, AeAT9 and AdAT17, using either transient expression in planta or by recombinant protein expression in yeast. Evidence is provided that both enzymes are alcohol acyl transferases and could potentially have roles in the biosynthesis of esters in kiwifruit. Our results suggest these two alcohol acyl transferases enzymes contribute to the production of branched, straight chain and sulphur esters
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