Derivation of Transport Equations using the Time-Dependent Projection Operator Method

We develop a formalism to carry out coarse-grainings in quantum field theoretical systems by using a time-dependent projection operator in the Heisenberg picture. A systematic perturbative expansion with respect to the interaction part of the Hamiltonian is given, and a Langevin-type equation without a time-convolution integral term is obtained. This method is applied to a quantum field theoretical model, and coupled transport equations are derived.Comment: 17 pages, Prog. Theor. Phys. in Pres

Pre-critical Phenomena of Two-flavor Color Superconductivity in Heated Quark Matter -- diquark-pair fluctuations and non-Fermi liquid behavior --

We investigate the fluctuations of the diquark-pair field and their effects on observables above the critical temperature $T_c$ in two-flavor color superconductivity (CSC) at moderate density using a Nambu-Jona-Lasinio-type effective model of QCD. Because of the strong-coupling nature of the dynamics, the fluctuations of the pair field develop a collective mode, which has a prominent strength even well above T_c. We show that the collective mode is actually the soft mode of CSC. We examine the effects of the pair fluctuations on the specific heat and the quark spectrum for T above but close to T_c. We find that the specific heat exhibits singular behavior because of the pair fluctuations, in accordance with the general theory of second-order phase transitions. The quarks display a typical non-Fermi liquid behavior, owing to the coupling with the soft mode, leading to a pseudo-gap in the density of states of the quarks in the vicinity of the critical point. Some experimental implications of the precursory phenomena are also discussed.Comment: 39 pages, 26 eps figures. The published version to appear in Prog. Theor. Phys. 114 (2005), 117-155. The references are up-date

Non-equilibrium Critical Dynamics and Precursory Phenomena in Color Superconductivity

We derive an effective equation to describe the non-equilibrium dynamics of the pair field of color superconductivity near the critical temperature. We also discuss how critical dynamics affects the specific heat and density of state above the critical temperature.Comment: 2 pages, 2 figures, PTPTeX. Proceedings of "Nuclear Matter under Extreme Conditions" at YITP, Kyoto, Japan, Dec. 1-3, 200

Pseudogap of Color Superconductivity

We show that the pseudogap of the quark density of states is formed in hot quark matter as a precursory phenomenon of the color superconductivity on the basis of a low-energy effective theory. We clarify that the soft mode of the di-quark pair field gives rise to a peculiar behavior of the quark dispersion relation and a short life-time of the quasiparticles near the Fermi surface, both of which make a depression of the density of states of quarks. Our result suggests that the appearance of the pseudogap is a universal phenomenon of strong coupling superconductors, irrespective of the dimensionality.Comment: 4 pages, 4 figures, PTPTeX; Proceedings of Finite Density QCD at Nara July 10-12 2003 Nara Prefecture Public Hall Big Roof Nara Japan; v2:errors in affiliation are correcte

Consistency of field-theoretical and kinetic calculations of viscous transport coefficients for a relativistic fluid

The transport coefficients of causal relativistic dissipative fluid dynamics are calculated both in a field-theoretical and a kinetic approach. We find that the results from the traditional kinetic calculation by Israel and Stewart are modified. The new expressions for the viscous transport coefficients agree with the results obtained in the field-theoretical approach when the contributions from pair creation and annihilation are neglected.Comment: 4 pages, 2 figure