A mathematician whose work I have admired for years is Chandler Davis. I’ve only sampled a small selection of his ouvre, but it’s always interesting.
So I was extremely interested to find this page, describing how Davis went to jail for six months in 1960, for refusing, on principle, to testify before the House Unamerican Activities Committee.
(As a technical paranthetical aside, I was rather chuffed earlier this year when Chris Dawson and I found a way of using one of Davis’ best-known results in a paper. Specifically, we made use of the Davis-Kahan theorem to understand how quantum entanglement arises as the result of competition between local and interaction terms in many-body quantum systems. The Davis-Kahan theorem is a very nice theorem that gives detailed information about how the eigenspaces of an operator change under perturbation. )