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LeanPool.RegtsSevenster.RS.Classical.Deligne.ChainMul

The multiplication of the chain algebra #

The symmetric multiplication descends through the module-tensor coequalizer of two symmetric powers, giving a module map of bundles; through the interchange, the tensor product of two chain stages multiplies into the chain stage of summed arity.

Defining equation of the chain multiplication: under the stage projections it is the raw crossing followed by the symmetric multiplications.