The talk is divided in two parts. The first part discusses the phenomenon of chiral symmetry and its breaking at zero temperature.
1. Different definitions of quark masses will be compared and their extraction from experiment are briefly explained. Also the quark condensate, an order parameter for chiral symmetry breaking, is
discussed. Special emphasis will be put on the strange quark mass and condensate. In the second part the temperature dependence of the various quantities introduced in the first part will be described.
We shall briefly comment on modifications at finite density as well.
2. The possible broadening of omega-and phi-mesons produced by heavy-ion collisions is discussed. The predictions for widths of these mesons as the function of the vector meson momentum at different nuclear densities and initial energies are presented.
Additionally the D-meson production by hadron-hadron and ion-ion interactions is analyzed. The problem related to the possible hidden charm in the hadron and nucleus is discussed. The predictions for the asymmetry of the produced D-mesons as the function of the Feynman variable x and the transverse momentum pt are presented.
The possible consequences of the obtained results for heavy-ion collisons at high energies are discussed.
