Colombeau algebra



The product of distributions is not canonically defined on all distributions; it is only partially defined on pairs of distributions whose sum of wave front sets does not intersect zero (“microlocal analysis”).

In contrast, Colombeau 92 defines algebra structures on distributions, now called Colombeau algebras (see Gratus 13 for review) which are globally defined, but at the cost that

  1. they are not uniquely defined,

  2. they do not restrict to the usual pointwise product on all functions.

Briefly: Colombeau considers sequences of functions that converge to distributions (weakly) and defines the product of two distributions as the product of the sequences. This product is not independent of the chosen sequences, which means that the level of abstraction achieved by distribution theory is abandoned.