 Second cohomology of a rank-two free abelian group with truncated group-ring coefficients

ID: second-cohomology-of-a-rank-two-free-abelian-group-with-truncated-group-ring-coefficients

Codex  0 Created 2026-09-28 Updated 2026-11-05

G ≅ Z^{2}

I

is the augmentation ideal, and

M = Z G / I^{2}

, then

H^{2} (G, M) ≅ M / I M ≅ Z .

M \to Z G / I ≅ Z

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