| dc.description.abstract | In this thesis, we investigate meson properties at finite chemical potential and
vanishing temperature and study the influence of mesonic and baryonic backcoupling
effects on the chiral order parameters and different parts of the QCD phase diagram.
For this purpose, we solve a coupled set of (truncated) Dyson-Schwinger equations
for the Landau gauged quark and gluon propagators with N f = 2 (+1) dynamical
quark flavors and the two cases of including and neglecting the backcoupling of
hadrons. The corresponding quark-meson Bethe-Salpeter vertices and bound state
properties, i.e. the meson masses and decay constants, of multiple light- and
strange-quark mesons are explicitly calculated from their homogeneous Bethe-
Salpeter equations at finite chemical potential and vanishing temperature. Since
the baryon backcoupling is calculated in the quark-diquark approximation, the
necessary baryon and diquark wave-functions and properties are approximated by
corresponding results explicitly calculated in vacuum.
At vanishing temperature, we study the changes of the quark dressing functions and
meson Bethe-Salpeter wave-functions with chemical potential and thereby trace
charge-conjugation parity breaking. For the light and strange quarks, we observe
two separate first-order coexistence regions. From zero chemical potential up to
the end of these coexistence regions, we find constant masses and decay constants
for every considered meson and the quark condensate. Thereby, we explicitly verify
the Silver-Blaze property of QCD. Inside the light- and strange-quark coexistence
region, the Pion and the K̄ meson, respectively, become more massive while their
decay constants decrease. The corresponding quantities for the (axial-)vector and
scalar mesons and the K meson remain (almost) perfectly constant.
For the backcoupling of the Pion and/or Sigma meson as well as for the backcoupling
of the nucleon and/or scalar diquark, we find similar chiral-restoration effects.
Considering backcoupled baryons, oscillations of the quark propagator at finite
chemical potential and vanishing temperature prevent a clear statement regarding
the liquid-gaseous phase transition. For Pion and Sigma meson backcoupling, we
observe a (small) shift of the critical endpoint towards smaller chemical potentials
and a reduced curvature of the chiral crossover line. We conclude that the location
of the critical endpoint in the phase diagram is mainly determined by microscopic
degrees of freedom of QCD (quarks and gluons) while its critical properties are
dominated by macroscopic degrees of freedom (especially the Sigma meson). | de_DE |
