7,968 research outputs found
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
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 () 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 .Comment: 12 pages, Latex, 2 figure
Controlled engineering of spin polarized transport properties in a zigzag graphene nanojunction
We investigate a novel way to manipulate the spin polarized transmission in a
two terminal zigzag graphene nanoribbon in presence of Rashba spin-orbit (SO)
interaction with circular shaped cavity engraved into it. A usual technique to
control the spin polarized transport behaviour of a nanoribbon can be achieved
by tuning the strength of the SO coupling, while we show that an efficient
engineering of the spin polarized transport properties can also be done via
cavities of different radii engraved in the nanoribbon. Simplicity of the
technique in creating such cavities in the experiments renders an additional
handle to explore transport properties as a function of the location of the
cavity in the nanoribbon. Further, a systematic assessment of the interplay of
the Rashba interaction and the dimensions of the nanoribbon is presented. These
results should provide useful input to the spintronic behaviour of such
devices. In addition to the spin polarization, we have also included an
interesting discussion on the charge transmission properties of the nanoribbon,
where, in absence of any SO interaction a metal-insulator transition induced by
the presence of a cavity is observed.Comment: 7 pages, 9 figures (Accepted in Europhysics Letters
Comment on Fermionic and Bosonic Pair-creation in an External Electric Field at Finite Temperature
We show that contrary to the claim made by Hallin and Liljenberg in Phys. Rev. D52 1150,(1995), (hep-th/9412188) the thermal correction to the thermal decay or pair production rate for a system placed in a heat bath in the presence of an external electric field, is always nonzero in the finite as well as infinite time limit. Using the formalism outlined there, we reestimate the decay rate for different values of temperature, mass and time.We also try to identify the parameter ranges where the quantity of interest agrees with that computed previously, at high temperature (in the infinite time limit), from the imaginary part of the effective action using imaginary time and real time formalism of thermal field theory. We also point out that in the strictly infinite time limit, the correct decay rate as obtained from the work of Hallin et. al. tends to diverge
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