Draft:Bivariant theory
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In mathematics, a bivariant theory, introduced by Fulton and MacPherson, is a pair of covariant and contravariant functors that assign to a map a group and a ring respectively. It generalizes a cohomology theory, which is a contravariant functor that assigns to a space a ring, namely a cohomology ring. The name "bivariant" refers to the fact that the theory contains both covariant and contravariant functors.[1]
Examples of bivariant theories include Chow groups and algebraic K-theory.
Reference
- ^ Fulton, William; MacPherson, Robert (1981). Categorical Framework for the Study of Singular Spaces. American Mathematical Society. ISBN 9780821822432.
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