No. Its top nonzero group would force dimension three. Poincare duality requires , and the universal coefficient theorem gives , since is free. This contradicts the proposed vanishing of . Equivalently its listed Betti numbers give Euler characteristic , impossible for a closed oriented odd-dimensional manifold.
No. The dimension would again be three. The universal coefficient theorem gives , since both and vanish. Poincare duality then forces , contradicting the proposed torsion group. In general the second integral homology of a connected closed oriented three-manifold is free abelian, being dual to its first homology.
Universal coefficient theorem for cohomology Created 2026-09-24 Updated 2026-10-14
This is the cohomological form of the universal coefficient theorem, with Ext and Hom terms rather than the homological tensor and Tor terms.
For an abelian coefficient group , cohomology fits into a split short exact sequence
Universal coefficient theorem for homology Created 2026-09-24 Updated 2026-10-14
For an abelian coefficient group , there is a split short exact sequence
For , the Tor term vanishes.
This is the homology case of the universal coefficient theorem; its cohomology case uses Hom and Ext rather than tensor product and Tor.