31 research outputs found
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 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