Homology after collapsing a nonseparating surface curve
ID: homology-after-collapsing-a-nonseparating-surface-curve
For genus , collapse a nonseparating simple closed curve on a closed orientable surface. Its homology class is primitive, as a curve meeting it transversely once detects by the intersection pairing on an oriented surface. The long exact sequence in relative homology therefore gives , , , and zero higher groups for the quotient. Geometrically it has the homotopy type .
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