
We prove that the lower bounds for Betti numbers of the rack, quandle and degeneracy cohomology given by Carter, Jelsovsky, Kamada, and Saito, are in fact equalities. We compute as well the Betti numbers of the twisted cohomology introduced by Carter, Elhamdadi, and Saito. We also give a group-theoretical interpretation of the second cohomology group for racks.
Boundary formula corrected. 9 pages
quandles, Algebra and Number Theory, rack cohomology, Invariants of knots and \(3\)-manifolds, cohomology groups, Other homology theories in algebraic topology, Hopf algebras (associative rings and algebras), racks, (Co)homology of rings and associative algebras (e.g., Hochschild, cyclic, dihedral, etc.), Mathematics - Quantum Algebra, FOS: Mathematics, Quantum Algebra (math.QA), Betti numbers, Cohomology of groups, Other (co)homology theories
quandles, Algebra and Number Theory, rack cohomology, Invariants of knots and \(3\)-manifolds, cohomology groups, Other homology theories in algebraic topology, Hopf algebras (associative rings and algebras), racks, (Co)homology of rings and associative algebras (e.g., Hochschild, cyclic, dihedral, etc.), Mathematics - Quantum Algebra, FOS: Mathematics, Quantum Algebra (math.QA), Betti numbers, Cohomology of groups, Other (co)homology theories
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