From my undergrad engineering math I understand some context here but am getting confused after a decade of programming. Words like "compact" and "closure" [0] probably do not translate directly to the mathematics space from software development - but don't really expect them to...

Thanks for the post it's a good kick in the rear to explore conceptually what eigenvalues/vectors are again!

[0]: from looking up "compact operator" https://en.wikipedia.org/wiki/Compact_operator