527 research outputs found
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.Comment: 11 pages including 1 table, 1 figure (available upon request
Spin and pseudospin symmetries of the Dirac equation with confining central potentials
We derive the node structure of the radial functions which are solutions of
the Dirac equation with scalar and vector confining central potentials,
in the conditions of exact spin or pseudospin symmetry, i.e., when one has
, where is a constant. We show that the node structure for exact
spin symmetry is the same as the one for central potentials which go to zero at
infinity but for exact pseudospin symmetry the structure is reversed. We obtain
the important result that it is possible to have positive energy bound
solutions in exact pseudospin symmetry conditions for confining potentials of
any shape, including naturally those used in hadron physics, from nuclear to
quark models. Since this does not happen for potentials going to zero at large
distances, used in nuclear relativistic mean-field potentials or in the atomic
nucleus, this shows the decisive importance of the asymptotic behavior of the
scalar and vector central potentials on the onset of pseudospin symmetry and on
the node structure of the radial functions. Finally, we show that these results
are still valid for negative energy bound solutions for anti-fermions.Comment: 7 pages, uses revtex macro
Influence of pions on the hadron-quark phase transition
In this work we present the features of the hadron-quark phase transition
diagrams in which the pions are included in the system. To construct such
diagrams we use two different models in the description of the hadronic and
quark sectors. At the quark level, we consider two distinct parametrizations of
the Polyakov-Nambu-Jona-Lasinio (PNJL) models. In the hadronic side, we use a
well known relativistic mean-field (RMF) nonlinear Walecka model. We show that
the effect of the pions on the hadron-quark phase diagrams is to move the
critical end point (CEP) of the transitions lines. Such an effect also depends
on the value of the critical temperature (T_0) in the pure gauge sector used to
parametrize the PNJL models. Here we treat the phase transitions using two
values for T_0, namely, T_0 = 270 MeV and T_0 = 190 MeV. The last value is used
to reproduce lattice QCD data for the transition temperature at zero chemical
potential.Comment: 3 pages. Proceedings of XXXV Reuni\~ao de Trabalhos sobre F\'isica
Nuclear no Brasil 201
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