The influence of strange quarks on QCD phase diagram and chemical freeze-out: Results from the hadron resonance gas model

We confront the lattice results on QCD phase diagram for two and three flavors with the hadron resonance gas model. Taking into account the truncations in the Taylor-expansion of energy density $\epsilon$ done on the lattice at finite chemical potential $\mu$, we find that the hadron resonance gas model under the condition of constant $\epsilon$ describes very well the lattice phase diagram. We also calculate the chemical freeze-out curve according to the entropy density $s$. The $s$-values are taken from lattice QCD simulations with two and three flavors. We find that this condition is excellent in reproducing the experimentally estimated parameters of the chemical freeze-out.Comment: 5 pages, 3 figures and 1 table Talk given at VIIIth international conference on ''Strangeness in Quark Matter'' (SQM 2004), Cape Town, South Africa, Sep. 15-20 200

Entropy for Color Superconductivity in Quark Matter

We study a model for color superconductivity with both three colors and massless flavors including quark pairing. By using the Hamiltonian in the color-flavor basis we can calculate the quantum entropy. From this we are able to further investigate the phases of the color superconductor, for which we find a rather sharp transition to color superconductivity above a chemical potential around $290$MeV.Comment: 10 pages, 2 eps-figure

Entropy for Colored Quark States at Finite Temperature

The quantum entropy at finite temperatures is analyzed by using models for colored quarks making up the physical states of the hadrons. We explicitly work out some special models for the structure of the states of SU(2) and SU(3) relating to the effects of the temperature on the quantum entropy. We show that the entropy of the singlet states monotonically decreases meaning that the mixing of these states continually diminishes with the temperature. It has been found that the structure of the octet states is more complex so that it can be best characterized by two parts. One part is very similar to that of the singlet states. The other one reflects the existence of strong correlations between two of the three color states. Furthermore, we work out the entropy for the {\it classical} Ising and the {\it quantum} XY spin chains. In Ising model the quantum (ground state) entropy does not directly enter into the canonical partition function. It also does not depend on the number of spatial dimensions, but only on the number of quantum states making up the ground state. Whereas, the XY spin chain has a finite entropy at vanishing temperature. The results from the spin models qualitatively analogous to our models for the states of SU(2) and SU(3).Comment: 19 pages, 4 eps figure

The effects of colored quark entropy on the bag pressure

We study the effects of the ground state entropy of colored quarks upon the bag pressure at low temperatures. The vacuum expectation values of the quark and gluon fields are used to express the interactions in QCD ground state in the limit of low temperatures and chemical potentials. Apparently, the inclusion of this entropy in the equation of state provides the hadron constituents with an additional heat which causes a decrease in the effective latent heat inside the hadronic bag and consequently decreases the non-perturbative bag pressure. We have considered two types of baryonic bags, $\Delta$ and $\Omega^-$. In both cases we have found that the bag pressure decreases with the temperature. On the other hand, when the colored quark ground state entropy is not considered, the bag pressure as conventionally believed remains constant for finite temperature.Comment: 13 pages, 2 eps-figures (2 parts each

Event-by-Event Fluctuations of Particle Ratios in Heavy-Ion Collisions

We study event-by-event dynamical fluctuations of various particle ratios at different energies. We assume that particle production in final state is due to chemical equilibrium processes. We compare results from resonance gas model with available experimental data. At SPS energies, the model can very well reproduce the experimentally measured fluctuations. We make predictions for dynamical fluctuations of strangeness and non-strangeness particle ratios. We found that the energy-dependence is non-monotonic. Furthermore, we found that fluctuations strongly depend on particle ratios.Comment: 6 pages, 2 figure, 1 tabl