Definition of "cohomology" []

• A theory associating a system of quotient groups to each topological space. (noun)
• A system of quotient groups associated to a topological space. (noun)

Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License

• "Section 33.9 is six pages of Penrose trying to explain "sheaf cohomology" whose ideas "… are fairly sophisticated mathematically, but actually very natural.""
• "Section 33.10 explains how positive/negative frequency splitting along with "holomorphic first sheaf cohomology" plays "a direct role in generating deformations of twistor space.""
• "This then leads us into some very rich theory of the algebraic topology of the Dirac operator and something called quantum cohomology."