Susceptibilities in effective model (Through Skype)

Non-perturbative model studies are established as an useful tool to
explore different features of QCD at both vanishing and non-vanishing
chemical potential. I have worked with such a model namely
Nambu-Jona-Lasinio (NJL) model and its Polyakov loop extended version
known as PNJL model.

I have divided my talk into three parts. In the first part, I will
show some results for a situation where isospin symmetry is explicitly
broken in 2 flavor sector. Although bulk thermodynamics and diagonal
susceptibilities remain almost unaltered, some off-diagonal
susceptibilities show significant deviation from their isospin
symmetric limit. We found a linear proportionality between these
susceptibilities and mass difference between light flavors. We give
some possible connection to HIC experiments in this context.

In the next part, we have tried to calculate quark number
susceptibility analytically using fluctuation-dissipation theorem
(FDT) and we found that result from the most expected form of FDT is
not matching with the Taylor coefficients of pressure. We have shown
that the difference is coming due to implicit chemical potential
dependence of pressure through mean fields. Our calculation points
towards a formal modification of FDT, when used in mean field models.

In continuation of the previous work, in the last section, we explored
isospin number fluctuation and flavor off-diagonal susceptibility to
study the importance of implicit dependence. Some logical arguments
immediately tells us about a correspondence between implicit
dependence and a particular class of diagrams in non-perturbative QCD.