# RSK-type dynamics

robinson_schensted_knuth

The RSK-type dynamics is a kind of weight-preserving dynamics on the space of (semi-standard) Young tableau / Gelfand-Tsetlin patterns.

Like the usual RSK, the basic building block is the insertion of a row to a Young tableau.

Unlike the usual RSK, it is generalised to having random output, namely it maps a deterministic tableau to a random tableau.

Definition. An RSK-type dynamics is a random map $$R$$: $$(r_{1 : \ell}, (\lambda^k_j)_{1 \le j \le k \ell}) \mapsto (\tilde\lambda^k_j)_{1 \le j \le k \ell}$$ satisfying

$| \lambda^k | - | \lambda^{k - 1} | + r_k = | \tilde\lambda^k | - | \tilde\lambda^{k - 1} | \qquad (1)$

Basically it says the following:

For any integer $$k$$, the number of $$k$$s in the old tableau plus the number of inserted $$k$$s equals the number of $$k$$s in the new tableau.

If we introduce time index $$n$$, namely suppose at time $$n$$, $$r = w_{n, 1 : \ell}$$ is inserted to $$\lambda^{n - 1, 1 : \ell}$$ to produce $$\lambda^{n, 1 : \ell}$$, the weight-preserving property (1) can be written in a more symmetric manner

$|\lambda^{n - 1, k - 1}| + |\lambda^{n, k}| - |\lambda^{n - 1, k}| - |\lambda^{n, k - 1}| = w_{n, k}. \qquad \text{a.s.}$

Example. RSK, qRSK and gRSK.