Monoidal Adjunctions - Linearity and Duality

Abstract

We explain two related constructions on the data of two monoidal symmetric closed categories $\mathcal{A}$ and $\mathcal{E}$ and monoidal functors $F:\mathcal{E}\to \mathcal{A}$ and $G:\mathcal{A}\to \mathcal{E}$. In a first part, we recall and partly extend work of A. Kock: In case $F$ is left-adjoint to $G$, and this adjunction is monoidal, we can equip the Eilenberg-Moore category ${\mathcal{E}}^T$ for $T$ being the canonical monad associated to the adjunction, with the structure of symmetric monoidal closed category, provided $\mathcal{E}$ has equalizers and ${\mathcal{E}}^T$ co-equalizers. In a second part, inspired by the Chu-construction, we build a category ${\mathcal{R}}_G$, which is symmetric monoidal closed as well, under the condition that $\mathcal{E}$ has pullbacks. Similarly we build a category ${\mathcal{L}}^F$ which is symmetric monoidal closed under the condition that $\mathcal{A}$ has what we call $F$-pushouts and $F$-pullbacks. In case $F⊣G$ is a monoidal adjunction, we show that ${\mathcal{L}}^F$ and ${\mathcal{R}}_G$ are isomorphic as symmetric monoidal closed categories. We show also how ${\mathcal{E}}^T$ is related to both.

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