ABSTRACT
This chapter introduces Gaussian path integrals over Grassmann variables by generalising integrals over a finite number of (Grassmann) degrees of freedom. It evaluates exactly the generating functional for the free-field theory of a Dirac field, much as for the free-field theory of a scalar field. The chapter discusses renormalisable theories of Dirac fields and scalar fields, involving interaction vertices with various numbers of fermion and scalar boson lines. It illustrates the way in which the Feynman rule assigning a minus sign to closed fermion loops arises by considering the scalar meson two-point function.
