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(14:00-15:00 UTC) Speaker: Davide Gabrielli (L'Aquila)
Title: Soliton decomposition of the Box Ball System
Abstract: The Box-Ball System (BBS) is a one-dimensional cellular automaton on the integer lattice. It is related to the Korteweg-de Vries (KdV) equation and exhibits solitonic behaviour. It was introduced by Takahashi and Satsuma who identified conserved quantities called solitons. We illustrate equivalent definitions of the system and we describe the Takahashi and Satsuma algorithm of identification of the solitons. We propose a different soliton decomposition which is equivalent to a branch decomposition of the tree associated to the excursions of the walk constructed starting from the ball configuration. Ferrari, Nguyen, Rolla and Wang (FNRW) map a ball configuration to a family of "soliton components" indexed by the soliton sizes. Building over this decomposition, we give an explicit construction of a large family of invariant measures for the BBS that are also shift invariant, including Markov and Bernoulli product measures. The construction is based on the concatenation of iid excursions in the associated walk trajectory.
(15:00-16:00 UTC) Speaker: Pablo A. Ferrari (Universidad de Buenos Aires)
Title: Soliton dynamics in the Box-Ball system
Abstract: A soliton is a solitary wave that in absence of other solitons moves at speed proportional to its size and conserves shape and speed even after colliding with other solitons. The FNRW soliton decomposition of a ball configuration is based on the k-slots, boxes determined by the configuration where size k solitons can be inserted. The components of a configuration η are denoted ζk∈N^Z, where ζk(i)=n means that there are n size k solitons in slot i of the kth component. The dynamics of the components reduce to a hierarchic translation; the shift of a component depending on the larger size components. Shift invariant ball distributions with independent components are time invariant for the dynamics. For space-ergodic initial distributions, the asymptotic speeds of solitons are shown to satisfy an universal system of linear equations related to the Generalized Gibbs Ensemble hydrodynamics.
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One World Probability Team