1,579 research outputs found
Interacting multi-component exciton gases in a potential trap: phase separation and Bose-Einstein condensation
The system under consideration is a multi-component gas of interacting para-
and orthoexcitons confined in a three dimensional potential trap. We calculate
the spatially resolved optical emission spectrum due to interband transitions
involving weak direct and phonon mediated exciton-photon interactions. For each
component, the occurrence of a Bose-Einstein condensate changes the spectrum in
a characteristic way so that it directly reflects the constant chemical
potential of the excitons and the renormalization of the quasiparticle
excitation spectrum. Moreover, the interaction between the components leads, in
dependence on temperature and particle number, to modifications of the spectra
indicating phase separation of the subsystems. Typical examples of density
profiles and luminescence spectra of ground-state para- and orthoexcitons in
cuprous oxide are given.Comment: 7 pages, 6 figure
Updated analysis of meson-nucleon sigma terms in the perturbative chiral quark model
We present an updated analysis of meson-baryon sigma terms in the
perturbative chiral quark model, which is based on effective chiral Lagrangian.
The new feature concerns the inclusion of excited states in the quark
propagator. Its influence on meson loops is shown to lead in particular for the
pion-nucleon sigma term to an enhancement relevant for the current evaluation
of this quantity. We also determine various flavor combinations of the scalar
nucleon form factors and their respective low-momentum transfer limits.Comment: 26 pages, 10 figures, to be published in Phys Rev
Learning frequent behaviors patterns in intelligent environments for attentiveness level
Nowadays, when it comes to achieving goals in business environments
or educational environments, the performance successfully has an important
role in performing a task. However, this performance can be affected by
several factors. One of the most common is the lack of attention. The individual’s
attention in performing a task can be determinant for the final quality or
even at the task’s conclusion. In this paper is intended to design a solution that
can reduce or even eliminate the lack of attention on performing a task. The
idea consist on develop an architecture that capture the user behavior through
the mouse and keyboard usage. Furthermore, the system will analyze how the
devices are used.This work has been supported by COMPETE: POCI-01-0145-FEDER-007043 and
FCT – Fundação para a Ciência e Tecnologia within the Project Scope:
UID/CEC/00319/2013.info:eu-repo/semantics/publishedVersio
Evidence for Complex Subleading Exponents from the High-Temperature Expansion of the Hierarchical Ising Model
Using a renormalization group method, we calculate 800 high-temperature
coefficients of the magnetic susceptibility of the hierarchical Ising model.
The conventional quantities obtained from differences of ratios of coefficients
show unexpected smooth oscillations with a period growing logarithmically and
can be fitted assuming corrections to the scaling laws with complex exponents.Comment: 10 pages, Latex , uses revtex. 2 figures not included (hard copies
available on request
Quark model description of quasi-elastic pion knockout from the proton at JLAB
The interference term between s- and t-pole contributions to the p(e,e' pi+)n
cross section is evaluated on the basis of the constituent quark model. It is
shown that the contribution of baryon s-poles can be modeled by a nonlocal
extension of the Kroll-Rudermann contact term. This contribution is in a
destructive interference with the pion t-pole that is essential to improve the
description of recent JLab data at the invariant mass W=1.95 GeV. Some
predictions are made for a new JLab measurement at higher values W=2.1-2.3 GeV
and Q2 centered at 1.6 and 2.45 GeV2/c2.Comment: 15 pages, 4 figures, to be published in Phys. Lett.
Spin-Boson Hamiltonian and Optical Absorption of Molecular Dimers
An analysis of the eigenstates of a symmetry-broken spin-boson Hamiltonian is
performed by computing Bloch and Husimi projections. The eigenstate analysis is
combined with the calculation of absorption bands of asymmetric dimer
configurations constituted by monomers with nonidentical excitation energies
and optical transition matrix elements. Absorption bands with regular and
irregular fine structures are obtained and related to the transition from the
coexistence to a mixing of adiabatic branches in the spectrum. It is shown that
correlations between spin states allow for an interpolation between absorption
bands for different optical asymmetries.Comment: 15 pages, revTeX, 8 figures, accepted for publication in Phys. Rev.
Hund's coupling and the metal-insulator transition in the two-band Hubbard model
The Mott-Hubbard metal-insulator transition is investigated in a two-band
Hubbard model within dynamical mean-field theory. To this end, we use a
suitable extension of Wilson's numerical renormalization group for the solution
of the effective two-band single-impurity Anderson model. This method is
non-perturbative and, in particular, allows to take into account the full
exchange part of the Hund's rule coupling between the two orbitals. We discuss
in detail the influence of the various Coulomb interactions on thermodynamic
and dynamic properties, for both the impurity and the lattice model. The
exchange part of the Hund's rule coupling turns out to play an important role
for the physics of the two-band Hubbard model and for the nature of the
Mott-transition
Static overscreening and nonlinear response in the Hubbard Model
We investigate the static charge response for the Hubbard model. Using the
Slave-Boson method in the saddle-point approximation we calculate the charge
susceptibility. We find that RPA works quite well close to half-filling,
breaking, of course, down close to the Mott transition. Away from half filling
RPA is much less reliable: Already for very small values of the Hubbard
interaction U, the linear response becomes much more efficient than RPA,
eventually leading to overscreening already beyond quite moderate values of U.
To understand this behavior we give a simple argument, which implies that the
response to an external perturbation at large U should actually be strongly
non-linear. This prediction is confirmed by the results of exact
diagonalization.Comment: 10 pages, 7 figures, RevTe
Entropy Production in Relativistic Hydrodynamics
The entropy production occurring in relativistic hydrodynamical systems such
as the quark-gluon plasma (QGP) formed in high-energy nuclear collisions is
explored. We study mechanisms which change the composition of the fluid, i.e.
particle production and/or chemical reactions, along with chemo- and
thermo-diffusion. These effects complement the conventional dissipative effects
of shear viscosity, bulk viscosity, and heat conductivity.Comment: 15 pages; LaTex. Accepted for publication in Physics Letters B. - Two
typos corrected and one reference adde
- …