Contou-Carrère symbol

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In mathematics, the Contou-Carrère symbola,b〉 is a Steinberg symbol defined on pairs of invertible elements of the ring of Laurent power series over an Artinian ring k, taking values in the group of units of k. It was introduced by Contou-Carrère (1994).

Mathematics field of study concerning quantity, patterns and change

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In mathematics a Steinberg symbol is a pairing function which generalises the Hilbert symbol and plays a role in the algebraic K-theory of fields. It is named after mathematician Robert Steinberg.

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Definition

If k is an Artinian local ring, then any invertible formal Laurent series a with coefficients in k can be written uniquely as

where w(a) is an integer, the elements ai are in k, and are in m if i is negative, and is a unit if i = 0.

The Contou-Carrère symbol 〈a,b〉 of a and b is defined to be

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References

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