A box-ball system (BBS) is a discrete dynamical system consisting of
balls
in an infinite strip of boxes. During each BBS move, the balls take turns jumping to
the first empty box, beginning with the smallest-numbered ball. The one-line
notation of a permutation can be used to define a BBS state. This paper
proves that the Robinson–Schensted (RS) recording tableau of a permutation
completely determines the dynamics of the box-ball system containing the
permutation.
Every box-ball system eventually reaches steady state, decomposing into solitons.
We prove that the rightmost soliton is equal to the first row of the RS insertion
tableau and it is formed after at most one BBS move. This fact helps us compute the
number of BBS moves required to form the rest of the solitons. First, we prove
that if a permutation has an L-shaped soliton decomposition then it reaches
steady state after at most one BBS move. Permutations with L-shaped soliton
decompositions include noncrossing involutions and column reading words.
Second, we make partial progress on the conjecture that every permutation on
objects reaches steady
state after at most
BBS moves. Furthermore, we study the permutations whose soliton decompositions
coincide with standard tableaux; we conjecture that they are closed under
consecutive pattern containment and that the RS recording tableaux belonging to
such permutations are counted by the Motzkin numbers.