(Joint NISER-TIFR discussion session) Najmul Haque

Title: General structure of gauge boson propagator in a hot magnetized medium

Abstract:
Recently we have systematically constructed the general structure of the gauge
boson self-energy and the effective propagator in presence of a nontrivial background
like hot magnetized medium using three mutually orthogonal projection tensors.
The hard thermal loop approximation has been used for the heat bath to obtain
various form factors associated with the two point function. We have analyzed the
dispersion spectra of the gauge boson using the effective propagator both in weak
and strong magnetic field approximation. The formalism is applicable to both QED
and QCD. The presence of a heat bath usually breaks the Lorentz (boost) symmetry
whereas that of magnetic field breaks the rotational symmetry in the system. The
presence of only thermal background leads to a longitudinal (plasmon) mode and a
two-fold degenerate transverse mode. In presence of a hot but weakly magnetized
background the degeneracy of the two transverse mode is lifted at low momenta
where one remains massive and the other one becomes massless. We also note that
the plasmon mode also becomes massless. On the other hand, in strong field approximation
the three modes behave almost like that of a free massless gauge boson in
Lowest Landau Level due to the dimensional reduction.