de Rham cohomology and a non-exact closed form
Research context
postgraduate concept · established · As of 2026-10-10
de Rham cohomology quotients closed k-forms by exact k-forms.
Key knowledge
de Rham cohomology quotients closed k-forms by exact k-forms. On R² minus the origin, omega=(x dy−y dx)/(x²+y²) is closed but its integral around the positively oriented unit circle is 2pi, so it cannot be globally exact. Local derivative identities do not decide global integrability; topology obstructs a single-valued potential.
Values and equations
H-dR^k(M)=ker(d:Omega^k→Omega^(k+1))/im(d:Omega^(k-1)→Omega^k)
- Omega^k
- Space of smooth k-forms
- M
- Smooth manifold
- d
- Exterior derivative
Conditions and scope
- The origin is excluded; the formula is smooth only on the punctured plane.
- Coefficients are real, and closed/exact refers to smooth differential forms.
Sources · 1
References
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Evidence and review
Author checked this English statement, displayed equation where present and stated hypotheses against these source locations: §§1.2, 2.1–2.2, 3.1, 11.1–11.2, 12.1–12.2, 13.1, 15.1–15.3, 17.1–17.3; each record narrows its applicable claim. The check is bounded to the recorded claims; no complete proof reconstruction, software proof replay or universal literature completeness is claimed.
2026-10-10 · Author source-body/statement/equation/domain check, with graph associations scoped individually. Separate independent content/source/inventory review is required before branch closure.
Entry details
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- research-math-de-rham-obstruction
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- research.1
- Structured reference record
- Postgraduate & research reference