Triangulated categories arising from n-fold matrix factorizations

Abstract: Let $\mathcal{A}$ be an additive category and let $T\colon \mathcal{A}\rightarrow \mathcal{A}$ be an additive functor equipped with a natural transformation $ω\colon \mathrm{Id}{\mathcal{A}}\rightarrow T$. We prove that the homotopy category of $n$-fold matrix factorizations of $ω$, denoted ${\rm HFact}{n}(\mathcal{A},T,ω)$, admits a natural structure of a right triangulated category. In particular, when $T$ is an automorphism, the homotopy category ${\rm HFact}{n}(\mathcal{A},T,ω)$ becomes triangulated. Furthermore, if $\mathcal{A}$ is a Frobenius exact category and $T$ is an autoequivalence, we obtain that the category ${\rm Fact}{n}(\mathcal{A},T,ω)$ of $n$-fold $(\mathcal{A},T)$-factorizations of $ω$ is a Frobenius exact category. Consequently, the stable category of the Frobenius exact category ${\rm Fact}_{n}(\mathcal{A},T,ω)$ is a triangulated category.