Explicit expressions for the integrals of second degree polynomials in the orthogonal group

38 Views Asked by At

Wikipedia has explicit formulas for first and second degree polynomial integrals in the unitary group using Weingarten functions (https://en.wikipedia.org/wiki/Weingarten_function).

Is there any closed form formula for similar integrals but in the Orthogonal group $O_d$? I am refering to integrals of the form:

$\int_{O_d} o_{ij} o_{kl} o_{mn} o_{pq} d\mu(O_d)$

where $\mu(O_d)$ is the Haar measure of the Orthogonal group.

I have found Theorem 2.1 and Proposition 2.2 in https://arxiv.org/pdf/0910.1258.pdf but I'm not sure how to go from this to a closed form formula, similar to the Wikipedia article. Thanks!