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Cohomology of finite monogenic self-distributive structures. (English) Zbl 1383.20039

Summary: A shelf is a set with a binary operation \(\triangleright\) satisfying \(a\triangleright (b\triangleright c) = (a\triangleright b) (a\triangleright c)\). Racks are shelves with invertible translations \(b \mapsto a\triangleright b\); many of their aspects, including cohomological, are better understood than those of general shelves. Finite monogenic shelves (FMS), of which Laver tables and cyclic racks are the most famous examples, form a remarkably rich family of structures and play an important role in set theory. We compute the cohomology of FMS with arbitrary coefficients. On the way we develop general tools for studying the cohomology of shelves. Moreover, inside any finite shelf we identify a sub-rack which inherits its major characteristics, including the cohomology. For FMS, these sub-racks are all cyclic.

MSC:

20N02 Sets with a single binary operation (groupoids)
55N35 Other homology theories in algebraic topology
57M27 Invariants of knots and \(3\)-manifolds (MSC2010)

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