Bosonic Matsubara sum
= Bosonic Matsubara sum
{c}
For $E>0$, contour summation over bosonic Matsubara frequencies gives
$$
T\sum_{n\in\mathbb Z}\frac1{\omega_n^2+E^2}
=\frac1{2E}\coth\frac{E}{2T}.
$$
It separates into the zero-point term $1/(2E)$ and a thermal Bose--Einstein occupation term.
= Matsubara sum
{c}
{synonym}