7,485 research outputs found
Pion-nucleon Sigma Term in the Global Color Model of QCD
We study the pion-nucleon sigma term in vacuum and in nuclear matter in the
framework of global color model of QCD. With the effective gluon propagator
being taken as the -function in momentum space of Munczek-Nomirovsky
model, we estimate that the sigma term at chiral limit in the vacuum is 9/2
times the current quark mass and it decreases with the nuclear matter density.
With the presently obtained in-medium pion-nucleon sigma term, we study the
in-medium chiral quark condensate and obtain a reasonable variation behavior
against the nuclear matter density.Comment: 17 pages, 3 figure
Quark Condensates in Nuclear Matter in the Global Color Symmetry Model of QCD
With the global color symmetry model being extended to finite chemical
potential, we study the density dependence of the local and nonlocal scalar
quark condensates in nuclear matter. The calculated results indicate that the
quark condensates increase smoothly with the increasing of nuclear matter
density before the critical value (about 12) is reached. It also
manifests that the chiral symmetry is restored suddenly as the density of
nuclear matter reaches its critical value. Meanwhile, the nonlocal quark
condensate in nuclear matter changes nonmonotonously against the space-time
distance among the quarks.Comment: 15 pages, 3 figure
Reevaluation of the density dependence of nucleon radius and mass in the global color symmetry model of QCD
With the global color symmetry model (GCM) at finite chemical potential, the
density dependence of the bag constant, the total energy and the radius of a
nucleon in nuclear matter is investigated. A relation between the nuclear
matter density and the chemical potential with the action of QCD being taken
into account is obtained. A maximal nuclear matter density for the existence of
the bag with three quarks confined within is given. The calculated results
indicate that, before the maximal density is reached, the bag constant and the
total energy of a nucleon decrease, and the radius of a nucleon increases
slowly, with the increasing of the nuclear matter density. As the maximal
nuclear matter density is reached, the mass of the nucleon vanishes and the
radius becomes infinite suddenly. It manifests that a phase transition from
nucleons to quarks takes place.Comment: 18 pages, 3 figure
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