How do you generalize the formula for matrices (or operators)
$$\int d^d x \, \exp \Big\{ - \frac{1}{2} x^i A_{ij} x^j \Big\} = \sqrt{\frac{(2 \pi)^d}{\det A}} = \sqrt{\det (2 \pi A^{-1})}$$
for tensors, i.e.
$$\int [d^d x]^2 \, \exp \Big\{ - \frac{1}{2} x^{ij} T_{ijkl} x^{kl} \Big\} \, ?$$
By $[d^d x ]^2$ I mean the integral over all variables $dx^{11}, dx^{12}, ..., dx^{21}, dx^{22}, ..., dx^{dd}$.