Let \(\omega \) be a compactly supported smooth \(n\)-form on \(\mathbb {R}^n\). Show that there exists a compactly supported smooth \((n-1)\)-form \(\eta \) with \(\omega =d\eta \) if and only if \[ \int _{\mathbb {R}^n}\omega =0. \] You are allowed to quote facts about \(H^k(X)\) but not about \(H_c^k(X)\).
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Math 6510 • Differentiable Manifolds
Winter 2004 • Question 4