I posted this question before in the Physics stack exchange, but it was recommended to post it better here.
While reading a paper I saw the following integral equation.
$\frac{1}{g} = \int_{-\pi}^{\pi} (\prod_{\sigma}\frac{\mathrm{d}p_{\sigma}}{2\pi}) \frac{\delta(\Sigma_{\sigma} p_{\sigma})}{(\prod_{\sigma} (1+\frac{2 \mathrm{sin}(p_{\sigma}/2)}{m}) -1)} \, ,\, \mathrm{with}\, \sigma = {1,2,3,4} $
But there was no solution given for it. To learn more about this integral equation, I would like to solve it. Sadly I don't even know how to begin/deal with this equation or more precisely with the integral itself. Hopefully someone can give me a hint or two.
cheers!