Once proved, mathematical theorems* tend to stay proved. Nevertheless, they can sometimes still be improved – say, by making them shorter. Take, for example proofs for The Hairy Ball Theorem. Mathematician Henri Poincaré first drew attention to the Hairy Ball Theorem in 1885 with his treatise ‘Sur les courbes déﬁnies par les équations différentielles (III)’ Journal de […]

# Tag: theorem

## Generalizing Keeler’s theorem (a.k.a. The Futurama Theorem)

Theorem 1. Let n ∈ N, n ≥ 2. The inverse of any permutation in Sn can be written as a product of distinct transpositions in Sn+2 \ Sn. Mathematically inclined aficionados of the cult animation series Futurama will no doubt recognise the theorem above – it was first posited by Ken Keeler in the […]

## Mathematicians on ham sandwiches

The Ham Sandwich Theorem has been a treat and a spur to mathematicians for more than half a century. There was a bit of a kerfuffle about who invented it, but that question did get settled. The Ham Sandwich Theorem cropped up in a branch of mathematics called algebraic topology. The theorem describes a particular truth about […]