3,964 research outputs found
Particle yields in heavy ion collisions and the influence of strong magnetic fields
It is expected that the magnetic field in the surface of magnetars do not
exceed G. However, in heavy ion collisions, this value is expected to
be much higher. We investigate the effects of a magnetic fields varying from
, to G in strange matter (composed of , and
quarks). We model matter as a free gas of baryons and mesons under the
influence of an external magnetic field. We study the effects of such strong
fields through a fit to some data sets of the STAR experiment. For
this purpose we solve the Dirac, Rarita-Schwinger, Klein-Gordon and Proca
equations subject to magnetic fields in order to obtain the energy expressions
and the degeneracy for spin 1/2, spin 3/2, spin 0 and spin 1 particles,
respectively. Our results show that a field of the order of G
produces an improved fitting to the experimental data as compared to the
calculations without magnetic field.Comment: 20 pages, 16 figures, 4 table
Ensino e capacitação agroflorestal no Brasil: uma abordagem com enfase na região Amazônica.
Cópia de trabalho editado em CD-ROM
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
Emergence of Clusters in Growing Networks with Aging
We study numerically a model of nonequilibrium networks where nodes and links
are added at each time step with aging of nodes and connectivity- and
age-dependent attachment of links. By varying the effects of age in the
attachment probability we find, with numerical simulations and scaling
arguments, that a giant cluster emerges at a first-order critical point and
that the problem is in the universality class of one dimensional percolation.
This transition is followed by a change in the giant cluster's topology from
tree-like to quasi-linear, as inferred from measurements of the average
shortest-path length, which scales logarithmically with system size in one
phase and linearly in the other.Comment: 8 pages, 6 figures, accepted for publication in JSTA
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 Rarita-Schwinger Particles Under de Influence of Strong Magnetic Fields
In this work, we calculate the solutions of the Rarita-Schwinger equation
with the inclusion of the eletromagnetic interaction. Our gauge and coupling
prescription choices lead to Dirac-type solutions. One of the consequences of
our results are the Landau level occupation of particles, quite different from
the usual spin 1/2 particle system occupation numbers.Comment: 12 page
Optimized delta expansion for relativistic nuclear models
The optimized -expansion is a nonperturbative approach for field
theoretic models which combines the techniques of perturbation theory and the
variational principle. This technique is discussed in the
model and then implemented in the Walecka model for the equation of state of
nuclear matter. The results obtained with the expansion are compared
with those obtained with the traditional mean field, relativistic Hartree and
Hartree-Fock approximations.Comment: 22 pages Latex, 3 ps figures, to appear in Z. Phys.
Seleção simultânea para desenvolvimento de linhagens de feijão-caupi de porte ereto e do tipo fradinho.
Cowpea bean is a socioeconomically important legume that contribute to generate employment and income. This species presents great grain variability, and the commercial subclass black eye stands out as a very appreciated grain in Brazil and abroad, thus requiring the development of new cultivars. The objective of this work was to evaluate and select lineages of commercial black eye cowpea, based on simultaneous, and direct selection..
- …