## Rowmotion in slow motion.(English)Zbl 1459.06010

Summary: Rowmotion is a simple cyclic action on the distributive lattice of order ideals of a poset: it sends the order ideal $$x$$ to the order ideal generated by the minimal elements not in $$x$$. It can also be computed in ‘slow motion’ as a sequence of local moves. We use the setting of trim lattices to generalize both definitions of rowmotion, proving many structural results along the way. We introduce a flag simplicial complex (similar to the canonical join complex of a semidistributive lattice) and relate our results to recent work of Barnard by proving that extremal semidistributive lattices are trim. As a corollary, we prove that if $$A$$ is a representation finite algebra and mod $$A$$ has no cycles, then the torsion classes of $$A$$ ordered by inclusion form a trim lattice.

### MSC:

 06D75 Other generalizations of distributive lattices 06B10 Lattice ideals, congruence relations 05E16 Combinatorial aspects of groups and algebras
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