14,824 research outputs found
Pion Mass Dependence of Nucleon Magnetic Moments
The relevance of the pion mass, provenient from a term which explicitely
breaks chiral symmetry in the Lagrangian, for nucleon magnetic moment in the
frame of the Skyrmion model in two different versions: the usual Skyrme model
and a modified one which includes a coupling to a light scalar meson field, the
sigma MeV). The results are compared to other
calculations. Our main motivation comes from usual extrapolations for values of
low energy QCD observables obtained in lattices with large values of pion/quark
masses toward realistic value of . which do not allow it. We do a
comparison with results from the Cloudy Bag Model and a chiral hadronic model
from chiral perturbation theory. There are several resulting extrapolations
from the region of large pion mass to the realistic value depending on the
considered model for low energy QCD.Comment: five pages, Contribution for the Proceedings of the Meeting on
Hadronic Interactions, Mackenzie University, S\~ao Paulo, SP, Brazil, May
200
Linear Sigma Model at finite baryonic density and symmetry breakings
The linear sigma model at finite baryonic density with a massive vector field
is investigated considering that all the bosonic fields develop non zero
expected classical values, eventually associated to condensates and
corresponding to dynamical symmetry breakings which might occur in the QCD
phase diagram. A modified equation for the classical vector field is proposed
with its respective solution. Some in medium properties of the model (mainly
masses) are investigated within reasonable prescriptions. In particular the
behavior of the {\it in medium} pion and sigma masses and a particular way of
calculating {\it in medium} coupling to baryons is investigated. A symmetry
radius for finite baryonic densities is proposed and calculated in different
ways in terms of the other variables of the model and these different ways of
calculating it agree quite well. However, assuming that the pion and sigma
masses go to zero close to the restoration of chiral symmetry a too high value
for the critical density is obtained .Comment: Work presented at the 18th Workshop on Hadronic Interactions, Sao
Paulo, SP, Brazil, May 2006. Accepted to be publishe
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