The boundary of the first order chiral phase transition in the m_pi-m_K--plane with a linear sigma model

Tree-level and complete one-loop parametrisation of the linear sigma model (LSM) is performed and the phase boundary between first order and crossover transition regions of the m_pi-m_K-plane is determined using the optimised perturbation theory (OPT) as a resummation tool of perturbative series. Away from the physical point the parameters of the model were determined by making use of chiral perturbation theory (ChPT). The location of the phase boundary for m_pi=m_K and of the tricritical point (TCP) on the m_pi=0 were estimated.Comment: 4 pages, 1 figure, uses espcrc1.sty; to appear in the proceedings of Strong and Electroweak Matter 2006 (SEWM06), BNL, May 200

Sensitivity of the chiral phase transition of QCD to the scalar meson sector

Gribov's theory of light quark confinement implies the existence of two kinds of scalar bound states. The phase diagram of the three-flavor QCD is mapped out in the (m_pi-m_K)-plane with help of the SU_L(3)xSU_R(3) linear sigma model supplemented with the assumption that the masses of the so-called superbound scalars do not change under the variation of the pion and kaon mass. The phase boundary along the m_pi=m_K line is found in the interval 15 MeV<m_crit<25 MeV, irrespective which f_0-sigma linear combination is identified with the pure superbound state.Comment: 11 pages, 3 figures, presented at the Gribov-75 Memorial Workshop on Quarks, Hadrons, and Strong Interactions, Budapest, Hungary, 22-24 May 200

Resummed one-loop determination of the phase boundary of the SU(3)(R) x SU(3)(L) linear sigma model in the (m(pi) - m(K))-plane

Complete one-loop parametrization of the linear sigma model is performed and the phase boundary between first order and crossover transition regions of the m_pi-m_K-plane is determined using the optimized perturbation theory as a resummation tool of perturbative series. Away from the physical point the parameters of the model were determined by making use of chiral perturbation theory. Along the diagonal m_pi=m_K of the mass--plane we estimate m_pi^c=110 +- 20 MeV. The location of the tricritical point on the m_pi=0 axis is estimated in the interval m_K^TCP in (1700,1850) MeV.Comment: RevTeX4, 11 pages, 6 figures, with macro package feynm

Mapping the boundary of the first order finite temperature restoration of chiral symmetry in the mpi - mK -plane with a linear sigma model

The phase diagram of the three-flavor QCD is mapped out in the low mass corner of the (m(pi)-m(K))-plane with help of the SU(L)(3)xSU(R)(3) linear sigma model (L sigma M). A novel zero temperature parametrization is proposed for the mass dependence of the couplings away from the physical point based on the three-flavor chiral perturbation theory(U(3) ChPT). One-loop thermodynamics is constructed by applying optimized perturbation theory. The unknown dependence of the scalar spectra on the pseudoscalar masses limits the accuracy of the predictions. Results are compared to lattice data and similar investigations with other variants of effective chiral models. The critical value of the pion mass is below 65 MeV for all m(K) value less than or similar to 800 MeV. Along the diagonal m(pi)=m(K), we estimate m(crit)(diag)=40 +/- 20 MeV