b = isStablyTrivial f
A possible obstruction to the commutativity of the CI operators in codim c, even asymptotically, would be the nontriviality of the map M_{(k+4)} > M_k \otimes \wedge^2(S^c) in the stable category of maximal CohenMacaulay modules.
In the following example, studied in the paper "Tor as a module over an exterior algebra" of Eisenbud, Peeva and Schreyer, the map is nontrivial...but it is stably trivial. The same goes for higher values of k (which take longer to compute). (note that in this case, with c = 3, two of the three alternating products are actually equal to 0, so we test only the third.)
Note that T is welldefined up to homotopy; so T^2 is welldefined mod mm^2.














The object isStablyTrivial is a method function.