cotensor
The cotensor product, denoted M ☐_C N, is a construction in the theory of coalgebras and comodules. It takes a right C-comodule M and a left C-comodule N over a coalgebra C (typically over a field k) and produces a new object that encodes the compatibility between their coactions.
Definition and construction: Let ρ_M: M → M ⊗ C be the coaction on M and ρ_N: N →
Universal property and functoriality: The cotensor product is a subobject of M ⊗ N and is functorial
Special cases and relations: If C is the base field k equipped with its trivial coalgebra structure
See also: tensor product of comodules, corings, coalgebras, Hopf algebras.