We consider several seemingly unrelated theorems, each with the word ellipse in the statement: Siebeck’s theorem, the elliptical range theorem, Poncelet’s theorem, and the Blaschke ellipse theorem.

We study the following question: suppose that A and ℬ are two algebras of complex n × n matrices such that the ring commutator [A, B] = AB – BA is "small" for each A ∈ A and B ∈ ℬ; does this imply ...

Sets, functions, and universal elements -- The integers -- Groups -- Rings -- Special fields -- Modules -- Vector spaces -- Matrices -- Determinants and tensor ...