Commit 2025-07-23 17:08 68bc12ad

feat(RepresentationTheory/Homological): (co)(res/inf) natural transformations on group (co)homology (#27393) Given a group homomorphism f : G →* H, we define

• groupCohomology.resNatTrans k f: restriction natural transformation between the functors sending A : Rep k H to Hⁿ(H, A) and to Hⁿ(G, Res(f)(A)).
• groupHomology.coresNatTrans k f: corestriction natural transformation between the functors sending A : Rep k H to Hₙ(G, Res(f)(A)) and to Hₙ(H, A). Given a normal subgroup S ≤ G, we define
• groupCohomology.infNatTrans k S: inflation natural transformation between the functors sending A : Rep k G to Hⁿ(G ⧸ S, A^S) and to Hⁿ(G, A).
• groupHomology.coinfNatTrans k S: coinflation natural transformation between the functors sending sending A : Rep k G to Hₙ(G, A) and to Hₙ(G ⧸ S, A_S).