19,204 research outputs found
Hyperbolic Unit Groups and Quaternion Algebras
We Classify the rational quadratic extensions K and the finite groups G for
which the group ring R[G] of G over the ring R of integers of K has the
property that the group of units of augmentation 1 of R[G] is hyperbolic. We
also construct units in a non-split quaternion algebra over R.Comment: 15 pages, this work is part of the PHd. Thesis of the third author.
The paper was accepted in Proceedings Mathematical Science
Test of Chemical freeze-out at RHIC
We present the results of a systematic test applying statistical thermal
model fits in a consistent way for different particle ratios, and different
system sizes using the various particle yields measured in the STAR experiment.
Comparison between central and peripheral Au+Au and Cu+Cu collisions with data
from p+p collisions provides an interesting tool to verify the dependence with
the system size. We also present a study of the rapidity dependence of the
thermal fit parameters using available data from RHIC in the forward rapidity
regions and also using different parameterization for the rapidity distribution
of different particles.Comment: SQM2008 conference proceeding
Vacuumless kinks systems from vacuum ones, an example
Some years ago, Cho and Vilenkin, introduced a model which presents
topological solutions, despite not having degenerate vacua as is usually
expected. Here we present a new model with topological defects, connecting
degenerate vacua but which in a certain limit recovers precisely the one
proposed originally by Cho and Vilenkin. In other words, we found a kind of
parent model for the so called vacuumless model. Then the idea is extended to a
model recently introduced by Bazeia et al. Finally, we trace some comments the
case of the Liouville model.Comment: 11 pages, 4 figure
Position-dependent-mass; Cylindrical coordinates, separability, exact solvability, and PT-symmetry
The kinetic energy operator with position-dependent-mass in cylindrical
coordinates is obtained. The separability of the corresponding Schr\"odinger
equation is discussed within radial cylindrical mass settings. Azimuthal
symmetry is assumed and spectral signatures of various z-dependent interaction
potentials (Hermitian and non-Hermitian PT-symmetric) are reported.Comment: 16 page
Caracterização morfológica de acessos de bacurizeiro por meio de descritores florais.
O bacurizeiro é uma espécie frutÃfera originária da Amazônia, onde são encontradas amplas variações em forma e tamanho de frutos, rendimento e qualidade de polpa, dentre outras caracterÃsticas de interesse (CAVALCANTE, 1996). Apesar de apresentar elevado potencial de uso na alimentação humana, ainda há carência de conhecimentos cientÃficos sobre a espécie, com destaque para biologia floral, mecanismos reprodutivos, manejo cultural e estabelecimento de descritores mÃnimos. O objetivo deste trabalho foi efetuar, com base em descritores florais, a caracterização morfológica de acessos de bacurizeiro da Coleção de Germoplasma da Embrapa Meio-Norte, estabelecidos em Teresina-PI
Irreversibility and the arrow of time in a quenched quantum system
Irreversibility is one of the most intriguing concepts in physics. While
microscopic physical laws are perfectly reversible, macroscopic average
behavior has a preferred direction of time. According to the second law of
thermodynamics, this arrow of time is associated with a positive mean entropy
production. Using a nuclear magnetic resonance setup, we measure the
nonequilibrium entropy produced in an isolated spin-1/2 system following fast
quenches of an external magnetic field and experimentally demonstrate that it
is equal to the entropic distance, expressed by the Kullback-Leibler
divergence, between a microscopic process and its time-reverse. Our result
addresses the concept of irreversibility from a microscopic quantum standpoint.Comment: 8 pages, 7 figures, RevTeX4-1; Accepted for publication Phys. Rev.
Let
Experimental Determination of Thermal Entanglement in Spin Clusters using Magnetic Susceptibility Measurements
The present work reports an experimental observation of thermal entanglement
in a clusterized spin chain formed in the compound NaCuSiO.
The presence of entanglement was investigated through two measured quantities,
an Entanglement Witness and the Entanglement of Formation, both derived from
the magnetic susceptibility. It was found that pairwise entanglement exists
below K. Tripartite entanglement was also observed below K. A theoretical study of entanglement evolution as a function of applied
field and temperature is also presented.Comment: Submited to Phys. Rev.
Estrutura genética populacional de bacurizeiros na região Meio-Norte do Brasil.
A região Meio-Norte caracteriza-se pela sua biodiversidade, com destaque para espécies frutÃferas nativas, como, por exemplo, o bacurizeiro, cujos frutos são apreciados na alimentação pelas populações locais. A fragmentação e/ou desmatamento que ocorre nessa área causa danos para populações de plantas, afetando a estrutura genética destas. Assim esse estudo verificou a estruturação genética em cinco populações de bacurizeiro dos Estados do Maranhão e Piauà por meio de marcadores entre simples sequências repetidas (ISSR) e da análise de variância molecular. Da diversidade genética total, 28,88% foi dividido entre as populações e 77,16% dentro das populações, portanto há estruturação significativa entre as populações
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