Renormalisation Group Improved Thermal Coupling Constant In An External Field

Starting from renormalised Effective Lagrangian, in the presence of an external Chromo-Electric field at finite temperature, the expression for thermal coupling constant ($\alpha = (g^2)/(4 \pi)$) as a function of temperature and external field is derived, using finite temperature two parameter renormalisation group equation of Matsumoto, Nakano and Umezawa. For some values of the parameters, the coupling constant is seen to be approaching a value $\sim unity$.Comment: 12 pages, Latex, 2 figure

Pre-Equilibrium Evolution of QCD Plasma :An Appraisal

We discuss, in this review, the existing models for the production of QGP in Relativistic Heavy Ion Collisions. We shall try to give a brief description of the models available for the pre-equilibrium production of QGP, ranging from soft process dominated QCD regime to the pQCD dominated regime. We also present the estimates for the initial energy density, the temperature and the thermalisation time -- available from each of these studies. Finally, we shall address the questions regarding thermalisation, color equilibration and chemical equilibration of the produced QGP in different experimental facilities.Comment: 15 pages, Latex, 3 figure

Magnetized matter effects on dilaton photon mixing

Dilatons ($\phi(x)$) are a class of bosonic scalar particles associated with scaling symmetry and its compensation (under the violations of the same). Due to two photon coupling, they can produce optical signatures in a magnetic field. In vacuum or plain matter they couple to one of the transversely polarized state of the photon. But in a magnetized matter, they couple to both the transversely polarized state of photon (due to emergence of a parity violating part of photon self energy contribution from a magnetized matter). A part of this work is directed towards understanding the issue of mixing of scalar with various polarizations states of photon in a medium ( magnetized or unmagnetized ) due to the constraints from different discrete (CPT) symmetries associated with the interaction. Based on these symmetry aided arguments, the structure of the mixing matrix is found to be $3 \times 3$. Thus there exists non-zero finite probabilities of oscillation between different polarization states of photon to dilaton. Our analytical and numerical analysis show no existence of periodic oscillation length either in temporal or spatial direction for most general values of the parameters in the theory. Possible astrophysical consequences of these results, those can be detected through observations are discussed.Comment: 39 pages; Accepted for the publication in Phys. Rev.