Existence of categorical products in the category of generalized Set-cellular automata (GCA_Set)
Determine whether binary products exist in the category GCA_Set of generalized Set-cellular automata; specifically, for any sets A and B and groups G and H, ascertain whether there exists an object P in GCA_Set together with generalized Set-cellular automata p_A: P → A^G and p_B: P → B^H such that for every object C^K in GCA_Set and pair of generalized Set-cellular automata α: C^K → A^G and β: C^K → B^H, there exists a unique generalized Set-cellular automaton u: C^K → P with p_A ∘ u = α and p_B ∘ u = β.
References
This implies that the weak product given in Theorem \ref{th-weak} is not a product in $GCA_{Set}$, but it is an open question if a product actually exists in $GCA_{Set}$.
— A categorical framework for cellular automata
(2602.04049 - Castillo-Ramirez et al., 3 Feb 2026) in Section 4, final paragraph (after Theorem 4)