Speaker
Description
The QCD critical point (QCD-CP) of a second-order nature
comes to exist when an explicit chiral symmetry breaking is present
at finite baryon density where the charge-conjugation symmetry is lost.
Thus, the order parameter of it is a linear
combination of the baryon density and the chiral scalar condensate,
but not the pure scalar chiral condensate.
Accordingly, the dynamical fluctuations of
the order parameter in the normal phase
has a dominant strength in the space-like region coming from
the collective particle-hole excitation corresponding to
density fluctuations; the peak energy of the collective mode goes down (softens) as the system approaches the QCD-CP in the normal phase and eventually vanishes there. This is the soft mode of the QCD-CP.
In this talk, employing Nambu-Jona-Lasinio model, we show that the photon self-energy in the medium is modified by the soft mode so significantly that the dilepton-pair production rate as well as the electric conductivity are anomalously enhanced near the critical point in the normal phase, through an Aslamazov-Larkin-like and other related processes, known to cause the 'para conductivity' in metal superconductors above the critical temperature.