arXiv subjects

S. S. Avancini

Publications and source records attributed to S. S. Avancini.

29 records · Page 2Linked to original sources

arXiv2005

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.

nucl-th↗

arXiv2004

Instabilities in asymmetric nuclear matter

The existence of phase transitions from liquid to gas phases in asymmetric nuclear matter (ANM) is related with the instability regions which are limited by the spinodals. In this work we investigate the instabilities in ANM described within relativistic mean field hadron models, both with constant and density dependent couplings at zero and finite temperatures. In calculating the proton and neutron chemical potentials we have used an expansion in terms of Bessel functions that is convenient at low densities. The role of the isovector scalar $δ$-meson is also investigated in the framework of relativistic mean field models and density dependent hadronic models. It is shown that the main differences occur at finite temperature and large isospin asymmetry close to the boundary of the instability regions.

nucl-th↗

arXiv2003

On the density dependent hadron field theory at finite temperature and its thermodynamical consistency

In this work we study in a formal way the density dependent hadron field theory at finite temperature for nuclear matter. The thermodynamical potential and related quantities, as energy density and pressure are derived in two different ways. We first obtain the thermodynamical potential from the grand partition function, where the Hamiltonian depends on the density operator and is truncated at first order. We then reobtain the thermodynamical potential by calculating explicitly the energy density in a Thomas-Fermi approximation and considering the entropy of a fermi gas. The distribution functions for particles and antiparticles are the output of the minimization of the thermodynamical potential. It is shown that in the mean field theory the thermodynamical consistency is achieved. The connection with effective chiral lagrangians with Brown-Rho scaling is discussed.

nucl-th↗

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.

nucl-th↗

arXiv2002

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.

cond-mat.soft↗

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.

nucl-th↗

arXiv2001

Applications of the Quon Algebra: 3-D Harmonic Oscillator and the Rotor Model

In this work we present a method to build in a systematic way a many-body quon basis state. In particular, we show a closed expression for a given number N of quons, restricted to the permutational symmetric subspace, which belongs to the whole quonic space. The method is applied to two simple problems: the three-dimensional harmonic oscillator and the rotor model and compared to previous quantum algebra results. The differences obtained and possible future applications are also discussed.

quant-ph↗

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.

nucl-th↗

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↗

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.

nucl-th↗

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.

nucl-th↗