1,330 research outputs found
Proposed realization of the Dicke-model quantum phase transition in an optical cavity QED system
The Dicke model describing an ensemble of two-state atoms interacting with a single quantized mode of the electromagnetic field (with omission of the Ă‚^2 term) exhibits a zero-temperature phase transition at a critical value of the dipole coupling strength. We propose a scheme based on multilevel atoms and cavity-mediated Raman transitions to realize an effective Dicke model operating in the phase transition regime. Optical light from the cavity carries signatures of the critical behavior, which is analyzed for the thermodynamic limit where the number of atoms is very large
Renormalization group flows for the second parafermionic field theory for N odd
Using the renormalization group approach, the Coulomb gas and the coset
techniques, the effect of slightly relevant perturbations is studied for the
second parafermionic field theory with the symmetry , for N odd. New
fixed points are found and classified
Hard and soft probe - medium interactions in a 3D hydro+micro approach at RHIC
We utilize a 3D hybrid hydro+micro model for a comprehensive and consistent
description of soft and hard particle production in ultra-relativistic
heavy-ion collisions at RHIC. In the soft sector we focus on the dynamics of
(multi-)strange baryons, where a clear strangeness dependence of their
collision rates and freeze-out is observed. In the hard sector we study the
radiative energy loss of hard partons in a soft medium in the multiple soft
scattering approximation. While the nuclear suppression factor does
not reflect the high quality of the medium description (except in a reduced
systematic uncertainty in extracting the quenching power of the medium), the
hydrodynamical model also allows to study different centralities and in
particular the angular variation of with respect to the reaction
plane, allowing for a controlled variation of the in-medium path-length.Comment: 5 pages, 4 figures, Quark Matter 2006 proceedings, to appear in
Journal of Physics
Antineutrino emission and gamma background characteristics from a thermal research reactor
The detailed understanding of the antineutrino emission from research
reactors is mandatory for any high sensitivity experiments either for
fundamental or applied neutrino physics, as well as a good control of the gamma
and neutron backgrounds induced by the reactor operation. In this article, the
antineutrino emission associated to a thermal research reactor: the OSIRIS
reactor located in Saclay, France, is computed in a first part. The calculation
is performed with the summation method, which sums all the contributions of the
beta decay branches of the fission products, coupled for the first time with a
complete core model of the OSIRIS reactor core. The MCNP Utility for Reactor
Evolution code was used, allowing to take into account the contributions of all
beta decayers in-core. This calculation is representative of the isotopic
contributions to the antineutrino flux which can be found at research reactors
with a standard 19.75\% enrichment in U. In addition, the required
off-equilibrium corrections to be applied to converted antineutrino energy
spectra of uranium and plutonium isotopes are provided. In a second part, the
gamma energy spectrum emitted at the core level is provided and could be used
as an input in the simulation of any reactor antineutrino detector installed at
such research facilities. Furthermore, a simulation of the core surrounded by
the pool and the concrete shielding of the reactor has been developed in order
to propagate the emitted gamma rays and neutrons from the core. The origin of
these gamma rays and neutrons is discussed and the associated energy spectrum
of the photons transported after the concrete walls is displayed.Comment: 14 pages, 11 figures, Data in Appendix A and B (13 pages
Particles in non-Abelian gauge potentials - Landau problem and insertion of non-Abelian flux
We study charged spin-1/2 particles in two dimensions, subject to a
perpendicular non-Abelian magnetic field. Specializing to a choice of vector
potential that is spatially constant but non-Abelian, we investigate the Landau
level spectrum in planar and spherical geometry, paying particular attention to
the role of the total angular momentum J = L +S. After this we show that the
adiabatic insertion of non-Abelian flux in a spin-polarized quantum Hall state
leads to the formation of charged spin-textures, which in the simplest cases
can be identified with quantum Hall Skyrmions.Comment: 24 pages, 10 figures (with corrected legends
New antineutrino energy spectra predictions from the summation of beta decay branches of the fission products
In this paper, we study the impact of the inclusion of the recently measured
beta decay properties of the Tc, Mo, and
Nb nuclei in an updated calculation of the antineutrino energy spectra
of the four fissible isotopes U, and Pu. These
actinides are the main contributors to the fission processes in Pressurized
Water Reactors. The beta feeding probabilities of the above-mentioned Tc, Mo
and Nb isotopes have been found to play a major role in the component
of the decay heat of Pu, solving a large part of the
discrepancy in the 4 to 3000\,s range. They have been measured using the Total
Absorption Technique (TAS), avoiding the Pandemonium effect. The calculations
are performed using the information available nowadays in the nuclear
databases, summing all the contributions of the beta decay branches of the
fission products. Our results provide a new prediction of the antineutrino
energy spectra of U, Pu and in particular of U for
which no measurement has been published yet. We conclude that new TAS
measurements are mandatory to improve the reliability of the predicted spectra.Comment: 10 pages, 2 figure
Effects of inclusion of spray-dried porcine plasma in lactation diets on sow and litter performance.
First measurements with a new -electron detector for spectral shape studies
The shape of the spectrum corresponding to the electrons emitted in
decay carries a wealth of information about nuclear structure and fundamental
physics. In spite of that, few dedicated measurements have been made of
-spectrum shapes. In this work we present a newly developed detector for
electrons based on a telescope concept. A thick plastic scintillator is
employed in coincidence with a thin silicon detector. First measurements
employing this detector have been carried out with mono-energetic electrons
from the high-energy resolution electron-beam spectrometer at Bordeaux. Here we
report on the good reproduction of the experimental spectra of mono-energetic
electrons using Monte Carlo simulations. This is a crucial step for future
experiments, where a detailed Monte Carlo characterization of the detector is
needed to determine the shape of the -electron spectra by deconvolution
of the measured spectra with the response function of the detector. A chamber
to contain two telescope assemblies has been designed for future -decay
experiments at the Ion Guide Isotope Separator On-Line facility in
Jyv\"askyl\"a, aimed at improving our understanding of reactor antineutrino
spectra
High pT and jet physics from RHIC to LHC
The observation of the strong suppression of high pT hadrons in heavy ion
collisions at the Relativistic Heavy Ion Collider (RHIC) at BNL has motivated a
large experimental program using hard probes to characterize the deconfined
medium created. However what can be denoted as ``leading particle physics''
accessible at RHIC presents some limitations which motivate at higher energy
the study of much more penetrating objects: jets. The gain in center of mass
energy expected at the Large Hadron Collider (LHC) at CERN will definitively
improve our understanding on how the energy is lost in the system opening a new
major window of study: the physics of jets on an event-by-event basis. We will
concentrate on the expected performance for jet reconstruction in ALICE using
the EMCal calorimeter.Comment: 14 pages, 14 figures, Proceedings of the Workshop on Relativistic
Nuclear Physics (WRNP) 2007, Kiev, Ukraine. Conference Info:
http://wrnp2007.bitp.kiev.ua/. Final version published in "Physics of Atomic
Nuclei
Entanglement Entropy of Random Fractional Quantum Hall Systems
The entanglement entropy of the and quantum Hall
states in the presence of short range random disorder has been calculated by
direct diagonalization. A microscopic model of electron-electron interaction is
used, electrons are confined to a single Landau level and interact with long
range Coulomb interaction. For very weak disorder, the values of the
topological entanglement entropy are roughly consistent with expected
theoretical results. By considering a broader range of disorder strengths, the
fluctuation in the entanglement entropy was studied in an effort to detect
quantum phase transitions. In particular, there is a clear signature of a
transition as a function of the disorder strength for the state.
Prospects for using the density matrix renormalization group to compute the
entanglement entropy for larger system sizes are discussed.Comment: 29 pages, 16 figures; fixed figures and figure captions; revised
fluctuation calculation
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