Multiplicative structures on comodules in higher categories
Takeshi Torii
TL;DR
This work extends multiplicative structures to comodules over bialgebras in the setting of $\infty$-categories by developing duoidal and mixed-duoidal frameworks, and by constructing generalized bimodule and right module objects that lift $\mathcal{O}$-monoidal structures to categories of (co)modules. The central result shows that for an $(\mathcal{O},\mathbf{Ass})$-bialgebra $\Gamma$ in ${}_A\mathrm{BMod}_A(\mathcal{M})$, where $\mathcal{M}$ is an $(\mathcal{O}\times\mathbf{Ass})$-monoidal $\infty$-category and $A$ an $(\mathcal{O}\times\mathbf{Ass})$-algebra, the right $\Gamma$-comodules $\mathrm{Rcomod}_{(A,\Gamma)}(\mathcal{M})$ form an $\mathcal{O}$-monoidal $\infty$-category with a strong $\mathcal{O}$-monoidal forgetful functor. The paper also develops parallel theories for bicomodules and right modules, and analogously for right comodules via the RM operad, providing a coherent, higher-algebraic framework for multiplicative structures on a broad class of (co)modules. These results lay foundational groundwork for applying higher category techniques to multiplicative phenomena in homotopy theory, representation theory, and related fields.
Abstract
In this paper we study multiplicative structures on comodules over bialgebras in the setting of $\infty$-categories. We show that the $\infty$-category of comodules over an $(\mathcal{O},\mathbf{Ass})$-bialgebra in a mixed $(\mathcal{O},\mathbf{Ass})$-duoidal $\infty$-category has the structure of an $\mathcal{O}$-monoidal $\infty$-category for any $\infty$-operad $\mathcal{O}$.
