128 research outputs found

### Effective linear meson model

The effective action of the linear meson model generates the mesonic n-point
functions with all quantum effects included. Based on chiral symmetry and a
systematic quark mass expansion we derive relations between meson masses and
decay constants. The model ``predicts'' values for f_eta and f_eta' which are
compatible with observation. This involves a large momentum dependent eta-eta'
mixing angle which is different for the on--shell decays of the eta and the
eta'. We also present relations for the masses of the 0^{++} octet. The
parameters of the linear meson model are computed and related to cubic and
quartic couplings among pseudoscalar and scalar mesons. We also discuss
extensions for vector and axialvector fields. In a good approximation the
exchange of these fields is responsible for the important nonminimal kinetic
terms and the eta-eta' mixing encountered in the linear meson model.Comment: 79 pages, including 3 abstracts, 9 tables and 9 postscript figures,
LaTeX, requires epsf.st

### Quark and Nuclear Matter in the Linear Chiral Meson Model

We present an analytical description of the phase transitions from a nucleon
gas to nuclear matter and from nuclear matter to quark matter within the same
model. The equation of state for quark and nuclear matter is encoded in the
effective potential of a linear sigma model. We exploit an exact differential
equation for its dependence upon the chemical potential $\mu$ associated to
conserved baryon number. An approximate solution for vanishing temperature is
used to discuss possible phase transitions as the baryon density increases. For
a nucleon gas and nuclear matter we find a substantial density enhancement as
compared to quark models which neglect the confinement to baryons. The results
point out that the latter models are not suitable to discuss the phase diagram
at low temperature.Comment: 27 pages, Int.J.Mod.Phys.A versio

### Two flavor chiral phase transition from nonperturbative flow equations

We employ nonperturbative flow equations to compute the equation of state for
two flavor QCD within an effective quark meson model. This yields the
temperature and quark mass dependence of quantities like the chiral condensate
or the pion mass. A precision estimate of the universal critical equation of
state for the three-dimensional O(4) Heisenberg model is presented. We
explicitly connect the O(4) universal behavior near the critical temperature
and zero quark mass with the physics at zero temperature and a realistic pion
mass. For realistic quark masses the pion correlation length near T_c turns out
to be smaller than its zero temperature value.Comment: 49 pages including 15 figures, LaTeX, uses epsf.sty and rotate.st

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