Meson correlation functions in a QCD plasma

The temporal pseudoscalar meson correlation function in a QCD plasma is investigated in a range of temperatures exceeding $T_c$ and yet of experimental interest. Only the flavour-singlet channel is considered and the imaginary time formalism is employed for the finite temperature calculations. The behaviour of the meson spectral function and of the temporal correlator is first studied in the HTL approximation, where one replaces the free thermal quark propagators with the HTL resummed ones. This procedure satisfactory describes the soft fermionic modes, but its application to the propagation of hard quarks is not reliable. An improved version of the so-called NLA scheme, which allows a better treatment of the hard fermionic modes, is then proposed. The impact of the improved NLA on the pseudoscalar temporal correlator is investigated.Comment: 35 pages, 15 figure

DCC: Attractive Idea Seeks Serious Confirmation

The theoretical ideas relevant for the physics of the disoriented chiral condensate (DCC) are reviewed.Comment: 18 pages LaTex, based on invited lecture given by A.Krzywicki at the workshop "Quark, plasma and beyond", Zif, Bielefeld, May 1996 ; a reference is correcte

Renormalized Finite Temperature phi^4 theory from the 2PI Effective Action

We present an analytical and numerical study of scalar phi^4 theory at finite temperature with a renormalized 2-loop truncation of the 2PI effective action.Comment: 4 pages. Presented at International Conference on Strong and Electroweak Matter (SEWM 2006), Upton, New York, 10-13 May 200

Comparing different hard-thermal-loop approaches to quark number susceptibilities

We compare our previously proposed hard-thermal-loop (HTL) resummed calculation of quark number susceptibilities using a self-consistent two-loop approximation to the quark density with a recent calculation of the same quantity at the one-loop level in a variant of HTL-screened perturbation theory. Besides pointing out conceptual problems with the latter approach, we show that it severely over-includes the leading-order interaction effects while including none of the plasmon term which after all is the reason to construct improved resummation schemes.Comment: 6 pages, 6 figures. Revised version to appear in Eur. J. Phys.

The thermodynamics of the quark-gluon plasma: Self-consistent resummations vs. lattice data

We discuss a recent approach for overcoming the poor convergence of the perturbative expansion for the thermodynamic potential of QCD. This approach is based on self-consistent approximations which allow for a gauge-invariant and manifestly ultraviolet-finite resummation of the essential physics of the hard thermal/dense loops. The results thus obtained are in good agreement with available lattice data down to temperatures of about twice the critical temperature. Calculations for a plasma with finite quark density (i.e., with a non-zero chemical potential $\mu$) are no more difficult than at $\mu=0$.Comment: 4 pages LaTeX2e, contribution to the proceedings of the 15th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (QM 2001), Long Island, New York, January 15 - 20, 200

Finite momentum meson correlation functions in a QCD plasma

The finite momentum meson spectral function (MSF) in the pseudoscalar channel is evaluated, adopting for the fermionic propagators HTL expressions. The different contributions to the meson spectral functions are clearly displayed. Our analysis may be of relevance for lattice studies of MSF based so far on the Maximum Entropy Method. As a further step the correlation function along the (imaginary-) temporal direction is evaluated.Comment: 29 pages, 25 figures, submitted to Nucl.Phys.

Universal shocks in the Wishart random-matrix ensemble - a sequel

We study the diffusion of complex Wishart matrices and derive a partial differential equation governing the behavior of the associated averaged characteristic polynomial. In the limit of large size matrices, the inverse Cole-Hopf transform of this polynomial obeys a nonlinear partial differential equation whose solutions exhibit shocks at the evolving edges of the eigenvalue spectrum. In a particular scenario one of those shocks hits the origin that plays the role of an impassable wall. To investigate the universal behavior in the vicinity of this wall, a critical point, we derive an integral representation for the averaged characteristic polynomial and study its asymptotic behavior. The result is a Bessoid function.Comment: 7 pages, 2 figure