Chiral Symmetry Breaking and Stability of the Magnetized Vacuum

The recent claim [arXiv:hep-th/0603070, arXiv:hep-th/0605020] that there exists in QED a maximum magnetic field of 10^{42} G, above which the magnetized vacuum becomes unstable with respect to the so-called "positronium collapse" is critically examined and unequivocally refuted.Comment: Contribution to Proceedings of Quantum Field Theory Under the Influence of External Conditions (QFEXT09), Norman, OK, September 21-25, 200

Real-time Nonequilibrium Dynamics in Hot QED Plasmas

The quantum kinetics of photons is studied directly in real time by implementing the dynamical renormalization group. In contrast to conventional approach, the dynamical renormalization group method consistently includes off-shell (energy non-conserving) effects and accounts for time-dependent collisional kernel. To lowest order we find that in the relaxation time approximation the semihard photon distribution function relaxes with a power law.Comment: LaTeX, 3 pages, talk presented at DPF2000, August 10, 2000, revised versio

Analysis and control of a scalar conservation law modeling a highly re-entrant manufacturing system

In this paper, we study a scalar conservation law that models a highly re-entrant manufacturing system as encountered in semi-conductor production. As a generalization of \cite{CKWang}, the velocity function possesses both the local and nonlocal character. We prove the existence and uniqueness of the weak solution to the Cauchy problem with initial and boundary data in $L^{\infty}$. We also obtain the stability (continuous dependence) of both the solution and the out-flux with respect to the initial and boundary data. Finally, we prove the existence of an optimal control that minimizes, in the $L^p$-sense with $p\in [1,\infty)$, the difference between the actual out-flux and a forecast demand over a fixed time period.Comment: 32 pages, 12 figure

Holographic study on the jet quenching parameter in anisotropic systems

We first calculate the jet quenching parameter of an anisotropic plasma with a U(1) chemical potential via the AdS/CFT duality. The effects of charge, anisotropy parameter and quark motion direction on the jet quenching parameter are investigated. We then discuss the situation of anisotropic black brane in the IR region. We study both the jet quenching parameters along the longitudinal direction and transverse plane

Direct photons: a nonequilibrium signal of the expanding quark-gluon plasma

Direct photon production from a longitudinally expanding quark-gluon plasma (QGP) at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies is studied with a real-time kinetic description that is consistently incorporated with hydrodynamics. Within Bjorken's hydrodynamical model, energy nonconserving (anti)quark bremsstrahlung q(\bar{q})\to q(\bar{q})\gamma and quark-antiquark annihilation q\bar{q}\to \gamma are shown to be the dominant nonequilibrium effects during the transient lifetime of the QGP. For central collisions we find a significant excess of direct photons in the range of transverse momentum 1-2 \lesssim p_T \lesssim 5 GeV/c as compared to equilibrium results. The photon rapidity distribution exhibits a central plateau. The transverse momentum distribution at midrapidity falls off with a {\em power law} p^{-\nu}_T with 2.5 \lesssim \nu \lesssim 3 as a consequence of these energy nonconserving processes, providing a distinct experimental {\em nonequilibrium signature}. The power law exponent \nu increases with the initial temperature of the QGP and hence with the total multiplicity rapidity distribution dN_\pi/dy.Comment: LaTeX (elsart.cls), 33 pages, 4 eps figures, updated with data for LHC, to appear in Nucl. Phys.