Support $\tau$-tilting subcategories in exact categories

Let $\mathcal{E}=(\mathcal{A},\mathcal{S})$ be an exact category with enough projectives $\mathcal{P}$. We introduce the notion of support $\tau$-tilting subcategories of $\mathcal{E}$. It is compatible with existing definitions of support $\tau$-tilting modules (subcategories) in various context. It is also a generalization of tilting subcategories of exact categories. We show that there is a bijection between support $\tau$-tilting subcategories and certain $\tau$-cotorsion pairs. Given a support $\tau$-tilting subcategory $\mathcal{T}$, we find a subcategory ${\mathcal{E}}_{\mathcal{T}}$ of $\mathcal{E}$ which is an exact category and $\mathcal{T}$ is a tilting subcategory of ${\mathcal{E}}_{\mathcal{T}}$. If $\mathcal{E}$ is Krull-Schmidt, we prove the cardinal $\mathrm{\mid }\mathcal{T}\mathrm{\mid }$ is equal to the number of isomorphism classes of indecomposable projectives $Q$ such that ${\mathrm{H}\mathrm{o}\mathrm{m}}_{\mathcal{E}}(Q,\mathcal{T})\mathrm{\ne }0$. We also show a functorial version of Brenner-Butler’s theorem.