S = - T ∫ d p + 1 σ - ζ [ e - β U 1 2 ζ a b ( G b a - F b a ) - ( p - 1 ) ] S=-T\int d^{p+1}\sigma\,\sqrt{-\zeta}\Bigl[e^{-\beta U}\frac{1}{2}\zeta^{ab} \left(G_{ba}-{\mathcal{F}}_{ba}\right)-(p-1)\Bigr]