Functional approach without path integrals to finite temperature free fermions

Charret et al. applied the properties of Grassmann generators to develop a new method to calculate the coefficientes of the high temperature expansion of the grand canonical partition function of self-interacting fermionic mo dels on d-dimensions (d greater than or equal to 1). The method explores th e anti-commuting nature of fermionic fields and avoids the calculation of t he fermionic path integral. We apply this new method to the relativistic fr ee Dirac fermions and recover the known results in the literature without t he beta-independent and mu-independent infinities that plague the continuum path integral formulation.