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Equivariant simplicial reconstruction. (English) Zbl 1454.05127

Summary: We introduce and analyze parallelizable algorithms to compress and accurately reconstruct finite simplicial complexes that have nontrivial automorphisms. The compressed data-called a complex of groups-amounts to a functor from (the poset of simplices in) the orbit space to the 2-category of groups, whose higher structure is prescribed by isomorphisms arising from conjugation. Using this functor, we show how to algorithmically recover the original complex up to equivariant simplicial isomorphism. Our algorithms are derived from generalizations (by Bridson-Haefliger, Carbone-Rips, and Corson, among others) of the classical Bass-Serre theory for reconstructing group actions on trees.

MSC:

05E18 Group actions on combinatorial structures
05E45 Combinatorial aspects of simplicial complexes
20F65 Geometric group theory
18N10 2-categories, bicategories, double categories
57M07 Topological methods in group theory
06A07 Combinatorics of partially ordered sets

Software:

Magma

References:

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