Семейно-математическое (вынос коммента из Фейсбука)
Everybody's mathematical subject in our family is/was different, and the collaboration distances between us are long. Everyone chose his/her mathematical specialization based on aesthetical rather than career considerations, and everyone's sense of mathematical aesthetics was different. My late father (died in 1988) was an expert in functional analysis (Banach spaces etc.) who dreamed about doing finite-dimensional combinatorial geometry. Unfortunately, his algebraic background was way too weak for that. My mother (retired from math. research now) was doing some kind of game theory: duels. Noisy and silent duels, mixed duels, the duel of two machine-gunners, the duel of two snipers, the fighter-bomber duel, this kind of stuff. From my perspective, it is applied math. with mostly military applications, but she was into it for the sake of the beauty of the mathematics involved. My brother as a child was interested in math. logic, and so he wrote two papers in math. logic (recursion theory, Kolmogorov complexity) joint with his late advisor. I loved algebra from my childhood, and so I am a homological algebraist. With strong topological algebra/functional analysis-inspired overtones, as is fitting of someone who grew up in a circle of functional analyst family friends.