Seat number configuration of the box-ball system, and its relation to the 10-elimination and invariant measures
Hayate Suda
TL;DR
The paper develops a unified framework for linearizing BBS dynamics through seat-number configurations by introducing the $k$-skip map $\Psi_k$, which acts as a shift on seat numbers and generalizes the classical $10$-elimination. It extends these constructions from the half-line to the whole-line, establishing a time-linearization theorem with an offset and proving that the $k$-skip map preserves key invariants such as the $\zeta_k$-counts. By connecting the $k$-skip map to invariant measures in FG, the authors derive distributional results for $\Psi_k(\eta)$ under both excursion-based and Markovian measures, including explicit updates of parameters under $k$-skip and the resulting expectations of the seat-number carrier. The results provide a probabilistic lens on BBS linearization, with implications for randomized BBS and potential space-time scaling analyses of tagged solitons.
Abstract
The box-ball system (BBS) is a soliton cellular automaton introduced in [TS], and it is known that the dynamics of the BBS can be linearized by several methods. Recently, a new linearization method, called the seat number configuration, is introduced in [MSSS]. The aim of this paper is fourfold. First, we introduce the $k$-skip map $Ψ_{k} : Ω\to Ω$, where $Ω$ is the state space of the BBS, and show that the $k$-skip map induces a shift operator of the seat number configuration. Second, we show that the $k$-skip map is a natural generalization of the $10$-elimination, which was originally introduced in [MIT] to solve the initial value problem of the periodic BBS. Third, we generalize the notions and results of the seat number configuration and the $k$-skip map for the BBS on the whole-line. Finally, we investigate the distribution of $Ψ_{k}(η), η\in Ω$ when the distribution of $η$ belongs to a certain class of invariant measures of the BBS introduced in [FG]. As an application of the above results, we compute the expectation of the carrier with seat numbers.
