Cohomology Operations
The Hopf algebra MU*(MU) is isomorphic to the polynomial algebra R, where R is the reduced bordism ring of a 0-sphere.
The coproduct is given by
where the notation 2i means take the piece of degree 2i. This can be interpreted as follows. The map
is a continuous automorphism of the ring of formal power series in x, and the coproduct of MU*(MU) gives the composition of two such automorphisms.
Read more about this topic: Complex Cobordism
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