New posts in Invariance

Given a finite number of stones. We place every stone on an integer. Prove that, given different movements, we can only make finite number of moves

Partition 100 people, 4 from each country into 4 groups with conditions

What are some puzzles that are solved by using invariants?

Proof that $a\nabla^2 u = bu$ is the only homogenous second order 2D PDE unchanged/invariant by rotation

Interesting Olympiad Style Problem about Invariance

Prove that the value of the expression $|a_1-b_1|+|a_2-b_2|+...+|a_n-b_n|$ does not depend on the coloring.

Suppose $M$ is an $m \times n$ matrix such that all rows and columns of $M$ sum to $1$. Show that $m=n$

Prove that if fewer than $n$ students in class are initially infected, the whole class will never be completely infected.

The Mathematics of Tetris

OCaml variance (+'a, -'a) and invariance