The large c limit of det(A+cB) where B is singular
This post was written long after the original document. The date on the post roughly corresponds to the document itself, not to the writing of this post.
In a group meeting, my Ph.D. advisor posed a mathematical question related to something he was working on. That afternoon, I figured out and wrote up a solution. Bill (my advisor) later confirmed the solution through a different approach (perturbation theory). I don’t think the specific approach he was working on ever led to anything useful, but this is a nice mathematical result.