347 research outputs found
Compositeness Effects in the Bose-Einstein Condensation
Small deviations from purely bosonic behavior of trapped atomic Bose-Einstein
condensates are investigated with the help of the quon algebra, which
interpolates between bosonic and fermionic statistics. A previously developed
formalism is employed to obtain a generalized version of the Gross-Pitaeviskii
equation. Two extreme situations are considered, the collapse of the condensate
for attractive forces and the depletion of the amount of condensed atoms with
repulsive forces. Experimental discrepancies observed in the parameters
governing the collapse and the depletion of the condensates can be accounted
for by universal fittings of the deformation parameter for each case.Comment: 17 pages, 1 tabl
Collective modes in relativistic npe matter at finite temperature
Isospin and density waves in neutral neutron-proton-electron (npe) matter are
studied within a relativistic mean-field hadron model at finite temperature
with the inclusion of the electromagnetic field. The dispersion relation is
calculated and the collective modes are obtained. The unstable modes are
discussed and the spinodals, which separate the stable from the unstable
regions, are shown for different values of the momentum transfer at various
temperatures. The critical temperatures are compared with the ones obtained in
a system without electrons. The largest critical temperature, 12.39 MeV, occurs
for a proton fraction y_p=0.47. For y_p=0.3 we get =5 MeV and for
y_p>0.495 MeV.
It is shown that at finite temperature the distillation effect in asymmetric
matter is not so efficient and that electron effects are particularly important
for small momentum transfers.Comment: 10 pages, 6 figure
C-banding And Fish In Chromosomes Of The Blow Flies Chrysomya Megacephala And Chrysomya Putoria (diptera, Calliphoridae).
The blow flies Chrysomya putoria and C. megacephala have 2n=12 chromosomes, five metacentric pairs of autosomes and an XX/XY sex chromosome pair. There are no substantial differences in the karyotype morphology of these two species, except for the X chromosome which is subtelocentric in C. megacephala and metacentric in C. putoria and is about 1.4 times longer in C. putoria. All autosomes were characterized by the presence of a C band in the pericentromeric region; C. putoria also has an interstitial band in pair III. The sex chromosomes of both species were heterochromatic, except for a small region at the end of the long arm of the X chromosome. Ribosomal genes were detected in meiotic chromosomes by FISH and in both species the NOR was located on the sex chromosomes. These results confirm that C. putoria was the species introduced into Brazil in 1970s, and not C. chloropyga as formerly described.96371-
q- Deformed Boson Expansions
A deformed boson mapping of the Marumori type is derived for an underlying
algebra. As an example, we bosonize a pairing hamiltonian in a two
level space, for which an exact treatment is possible. Comparisons are then
made between the exact result, our q- deformed boson expansion and the usual
non - deformed expansion.Comment: 8 pages plus 2 figures (available upon request
The pasta phase within density dependent hadronic models
In the present paper we investigate the onset of the pasta phase with
different parametrisations of the density dependent hadronic model and compare
the results with one of the usual parametrisation of the non-linear Walecka
model. The influence of the scalar-isovector virtual delta meson is shown. At
zero temperature two different methods are used, one based on coexistent phases
and the other on the Thomas-Fermi approximation. At finite temperature only the
coexistence phases method is used. npe matter with fixed proton fractions and
in beta-equilibrium are studied. We compare our results with restrictions
imposed on the the values of the density and pressure at the inner edge of the
crust, obtained from observations of the Vela pulsar and recent isospin
diffusion data from heavy-ion reactions, and with predictions from spinodal
calculations.Comment: 15 pages, 11 figures and 7 table
Compositeness effects, Pauli's principle and entanglement
We analyse some compositeness effects and their relation with entanglement.
We show that the purity of a composite system increases, in the sense of the
expectation values of the deviation operators, with large values of the
entanglement between the components of the system. We also study the validity
of Pauli's principle in composite systems. It is valid within the limits of
application of the approach presented here. We also present an example of two
identical fermions, one of them entangled with a distinguishable particle,
where the exclusion principle cannot be applied. This result can be important
in the description of open systems
Relativistic Mean-Field Hadronic Models under Nuclear Matter Constraints
Relativistic mean-field (RMF) models have been widely used in the study of
many hadronic frameworks because of several important aspects not always
present in nonrelativistic models, such as intrinsic Lorentz covariance,
automatic inclusion of spin, appropriate saturation mechanism for nuclear
matter, causality and, therefore, no problems related to superluminal speed of
sound. With the aim of identifying the models which best satisfy well known
properties of nuclear matter, we have analyzed parameterizations of seven
different types of RMF models under three different sets of constraints related
to symmetric nuclear matter, pure neutron matter, symmetry energy, and its
derivatives. One of these (SET1) is formed of the same constraints used in a
recent work [M. Dutra et al., Phys. Rev. C 85, 035201 (2012)] in which we
analyzed Skyrme parameterizations. The results pointed to models
consistent with all constraints. By using another set of constraints, namely,
SET2a, formed by the updated versions of the previous one, we found models
approved simultaneously. Finally, in the third set, named SET2b, in which the
values of the constraints are more restrictive, we found consistent models.
Another interesting feature of our analysis is that the results change
dramatically if we do not consider the constraint regarding the volume part of
the isospin incompressibility (). In this case, we have
approved models in SET2a and in SET2b.Comment: 63 pages, 3 figures and 9 tables. Version accepted for publication in
PR
Density Dependent Parametrization Models: Formalism and Applications
In this work we derive a formalism to incorporate asymmetry and temperature
effects in the Brown-Rho (BR) scaled lagrangian model in a mean field theory.
The lagrangian density discussed in this work requires less parameters than the
usual models with density dependent couplings. We also present the formalism
with the inclusion of the eight lightest baryons, two lightest leptons, beta
equilibrium and charge neutrality in order to apply the BR scaled model to the
study of neutron stars. The results are again compared with the ones obtained
from another density dependent parametrization model. The role played by the
rearrangement term at T=0 for nuclear or neutron star matter and at finite
temperature is investigated. The BR scaled model is shown to be a good tool in
studies involving density dependent effective masses and in astrophysics
applications.Comment: 23 pages, 10 figure
Informalidade e Pandemia na Tríplice Fronteira: o Auxílio Emergencial (Brasil) e o Pytyvõ 2.0 (Paraguai)
Artigo apresentado como trabalho de conclusão do curso de Especialização em Relações Internacionais Contemporâneas.Diante da pandemia do novo coronavírus e a necessidade do isolamento social para tentar frear a transmissão do vírus e evitar o colapso dos sistemas de saúde, a Tríplice Fronteira se tornou um campo fértil para se estudar as repercussões da pandemia. O trabalho informal, em Foz do Iguaçu, do lado brasileiro e em Ciudad del Este, do lado paraguaio, sempre foi uma constante, registrando-se inúmeros pessoas que cruzam a fronteira diariamente em busca de trabalho. Com o bloqueio das fronteiras, os trabalhadores informais ficaram,em sua grande maioria, sem essa possibilidade. O Auxílio Emergencial do Brasil o benefício Pytyvõ 2.0 do Paraguai se tornaram a única renda para muitos que sobreviviam da informalidade e, de certa forma, deu visibilidade a um conjunto de trabalhadores até então pouco visíveis nos estudos e análises sobre o trabalho na região
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