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Tag

Invariants

3 resources tagged “Invariants” across the knowledge library.

3 items

Guide6 Aug 2026Definition of Group Homology and CohomologyGroup homology and cohomology as derived functors of coinvariants and invariants, equivalently as Tor and Ext over the group ring, with the basic properties and long exact sequences.3 min readRead More Guide6 Aug 2026Definition of Lie Algebra CohomologyLie algebra cohomology as Ext over the enveloping algebra, invariants and coinvariants, the explicit description in degrees 0 and 1, and derivations.3 min readRead More Guide6 Aug 2026Low-Dimensional Group CohomologyExplicit descriptions of H^0, H^1 and H_1 for group cohomology, with trivial and non-trivial coefficients, and their interpretations.3 min readRead More