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(All higher categories will be strict unless otherwise noted):

It is a somewhat folklorish fact that if you equip the category of $(m,n)$ categories with the cartesian monoidal structure, then a category enriched in $(m,n)$-cat is an $(m+1,n+1)$-category. More succinctly, there is an equivalence of categories

$$((m,n)\text{-Cat}, \times)\text{-Cat} \cong (m+1,n+1)\text{-Cat}.$$

There is another monoidal structure on $(m,n)\text{-Cat}$, the Crans–Gray tensor product. Denote it by $\otimes$. If I understand correctly, this should be thought of as a sort of weak version of a product, e.g. if I denote by $[1]$ the interval category, then $[1] \times [1]$ is a commutative square, whereas $[1]\otimes[1]$ is a weakly commuting square.

Given this monoidal structure, it feels natural to enrich categories in it — that is, to consider the category $((m,n)\text{-Cat},\otimes)\text{-Cat}$. For the case $m=n=2$, this turns out to recover "$3$-categories with weak interchange and everything else strict" (also called Gray categories).

Question 1: Is there somewhere in which a (Quillen) adjunction

$$((2,2)\text{-Cat}, \otimes)\text{-Cat} \rightleftarrows ((2,2)\text{-Cat}, \times)\text{-Cat} \cong (3,3)\text{-Cat}$$

is constructed? This seems (relatively) simple but I haven't been able to find a reference.

Question 2: Has anyone studied any other cases of $((m,n)\text{-Cat},\otimes)\text{-Cat}$? I am specifically interested in the case $m = \omega$ (and even more specifically, I am happy to restrict to $n=0$).

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  • $\begingroup$ Are you asking about the lax Gray or pseudo Gray tensor product? Are your $(m,n)$-categories weak or strict? $\endgroup$ Commented Nov 30 at 6:17
  • $\begingroup$ @TimCampion I'm asking about strict higher categories. As for pseudo vs lax, I'm happy to get answers of either variety. My impression, though, was that only the lax version had been fully constructed. (Though if I understand correctly, there should be no distinction in the case $n=0$). $\endgroup$
    – K. Strong
    Commented Nov 30 at 14:59

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