Markov theorem

In mathematics the Markov theorem gives necessary and sufficient conditions for two braids to have closures that are equivalent links. In algebraic topology, Alexander's theorem states that every knot or link in three-dimensional Euclidean space is the closure of a braid. The Markov theorem, proved by Russian mathematician Andrei Andreevich Markov Jr.[1] states that three conditions are necessary and sufficient for two braids to have equivalent closures:

1. They are equivalent braids
2. They are conjugate braids
3. Appending or removing on the right of the braid a strand that crosses the strand to its left exactly once.