arXiv subjects

D. P. Menezes

Publications and source records attributed to D. P. Menezes.

68 records · Page 4Linked to original sources

arXiv2002

Relativistic Mean Field Approximation in a Density Dependent Parametrization Model at Finite Temperature

In this work we calculate the equation of state of nuclear matter for different proton fractions at zero and finite temperature within the Thomas Fermi approach considering three different parameter sets: the well-known NL3 and TM1 and a density dependent parametrization proposed by Typel and Wolter. The main differences are outlined and the consequences of imposing beta-stability in these models are discussed.

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arXiv2002

Quons Restricted to the Antisymmetric Subspace: Formalism and Applications

In this work we develop a formalism to treat quons restricted to the antisymmetric part of their many-body space. A model in which a system of identical quons interact through a pairing force is then solved within this restriction and the differences between our solution and the usual fermionic model solution are then presented and discussed in detail. Possible connections to physical systems are also considered.

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arXiv2001

Caloric curve for finite nuclei in relativistic models

In this work we calculate the caloric curve (excitation energy per particle as a function of temperature) for finite nuclei within the non--linear Walecka model for different proton fractions. It is shown that the caloric curve is sensitive to the proton fraction. Freeze-out volume effects in the caloric curve are also studied.

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arXiv2001

Relativistic Thomas-Fermi description of Sm isotopes at finite temperature

The caloric curve (excitation energy per particle as a function of temperature) for finite nuclei is calculated within the non-linear Walecka model for different proton fractions and different parameterizations. The results obtained are compared with published experimental data and other theoretical results. Other properties related with the droplet formation as the surface energy, neutron skin thickness and binding energy per nucleon are also displayed as a function of temperature and their behaviours are discussed. It is shown that the caloric curve is sensitive to the proton fraction and to the Coulomb interaction. At T=0 the droplet properties do not depend on the parameterization used. At finite temperature however, the sensitivity appears.

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arXiv2000

The q-Deformed NJL Model "Revisited"

In this work we investigate the chiral symmetry breaking in the q-deformed version of the NJL Model and its consequent mass generation mechanism . We show that the deformation of the NJL model, in the mean field approximation, may take into account correlations that go beyond the mean field and, in a certain limit, approaches the more realistic lattice calculations.

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arXiv1999

Droplet formation in cold asymmetric nuclear matter in the quark-meson-coupling model

The quark-meson-coupling model is used to study droplet formation from the liquid-gas phase transition in cold asymmetric nuclear matter. The critical density and proton fraction for the phase transition are determined in the mean field approximation. Droplet properties are calculated in the Thomas-Fermi approximation. The electromagnetic field is explicitly included and its effects on droplet properties are studied. The results are compared with the ones obtained with the NL1 parametrization of the non-linear Walecka model.

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arXiv1999

Quons as su(2) Irreducible Tensor Operators

We prove that, for the quon algebra, which interpolates between the Bose and Fermi statistics and depends on a free parameter q,it is possible to build an su(2) irreducible representation. One of the consequences of this fact is that the quons couple via the same angular momentum coupling rules obeyed by ordinary bosons and fermions.

math.QA↗

arXiv1998

Nucleation Process in Asymmetric Nuclear Matter

An extended version of the non linear Walecka model, with rho mesons and eletromagnetic field is used to investigate the possibility of phase transitions in hot (warm) nuclear matter, giving rise to droplet formation. Surface properties of asymmetric nuclear matter as the droplet surface energy and its thickness are also examined.

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arXiv1997

Optimized delta expansion for relativistic nuclear models

The optimized $δ$-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 $λϕ^4$ model and then implemented in the Walecka model for the equation of state of nuclear matter. The results obtained with the $δ$ expansion are compared with those obtained with the traditional mean field, relativistic Hartree and Hartree-Fock approximations.

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arXiv1997

Exact Q-Deformed Dyson Expansion for the Nuclear J=5/2 Shell

The quon algebra, which interpolates between the Bose and Fermi algebras and depends on a free paramenter $q$, is used to generate a deformed Dyson boson expansion of the quadrupole operator. Then we obtain a quadrupole-quadrupole hamiltonian, for a single j-shell, in terms of this deformed bosonic operator. The hamiltonian is diagonalized and its eigenvalues are compared with the ones obtained from the fermionic quadrupole-quadrupole hamiltonian. The deformation parameter helps in achieving the correct energy levels, what cannot be encountered in practice with the usual non-deformed Dyson expansion.

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arXiv1996

q- Deformed Boson Expansions

A deformed boson mapping of the Marumori type is derived for an underlying $su(2)$ 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.

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arXiv1996

Nuclear Matter Properties in Derivative Coupling Models Beyond Mean - Field Approximation

The structure of infinite nuclear matter is studied with two of the Zimanyi - Moszkowski (ZM) models in the framework of a relativistic approximation which takes into account Hartree terms and beyond and is compared with the results which come out of the relativistic Hartree - Fock approach in the linear Walecka model. The simple treatment applied to these models can be used in substitution to the more complicated Dirac - Brueckner - Hartree - Fock method to perform future calculations in finite nuclei.

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arXiv1995

Optimized $δ$ expansion for the Walecka model

The optimized $δ$-expansion is used to study vacuum polarization effects in the Walecka model. The optimized $δ$-expansion is a nonperturbative approach for field theoretic models which combines the techniques of perturbation theory and the variational principle. Vacuum effects on self-energies and the energy density of nuclear matter are studied up to ${\cal O}(δ^2)$. When exchange diagrams are neglected, the traditional Relativistic Hartree Approximation (RHA) results are exactly reproduced and, using the same set of parameters that saturate nuclear matter in the RHA, a new stable, tightly bound state at high density is found.

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arXiv1995

Studying medium effects with the optimized $\bdelta$ expansion

The possibility of using the optimized $δ$ expansion for studying medium effects on hadronic properties in quark or nuclear matter is investigated. The $δ$ expansion is employed to study density effects with two commonly used models in hadron and nuclear physics, the Nambu--Jona-Lasinio model for the dynamical chiral symmetry breaking and the Walecka model for the equation of state of nuclear matter. The results obtained with the $δ$ expansion are compared to those obtained with the traditional Hartree-Fock approximation. Perspectives for using the $δ$ expansion in other field theoretic models in hadron and nuclear physics are discussed.

hep-ph↗