Quark Number Susceptibility and Thermal Dilepton Rate: An effective model study

Fluctuations of conserved quantum numbers are associated with the corresponding susceptibilities because of the symmetry of the system. The underlying fact is that these fluctuations as defined through the static correlators become identical to the direct calculation of these susceptibilities defined through the thermodynamic derivatives, due to the fluctuation-dissipation theorem. In the present talk I will discuss that a diagrammatic calculation of the static correlators associated with conserved quark number fluctuation and the corresponding susceptibilities are possible in case of mean field theories, if the implicit dependence of the mean fields on the quark chemical potential are taken into account appropriately. As an aside the vector current correlation function, some of its spectral properties and thermal dilepton rate will also be discussed within the framework of effective mean field model.