Triangular Matrix Categories over path Categories and Quasi-hereditary Categories, as well as one point extensions by Projectives (2107.10982v1)

Abstract: In this paper, we prove that the lower triangular matrix category $\Lambda =\left [ \begin{smaLLMatrix} \mathcal{T}&0\ M&\mathcal{U} \end{smaLLMatrix} \right ]$, where $\mathcal{T}$ and $\mathcal{U}$ are quasi-hereditary $\mathrm{Hom}$-finite Krull-Schmidt $K$-categories and $M$ is a $\mathcal U\otimes_K \mathcal T^{op}$-module that satisfies suitable conditions, is quasi-hereditary in the sense of \cite{LGOS1} and \cite{Martin}. Moreover, we solve the problem of finding quotients of path categories isomorphic to the lower triangular matrix category $\Lambda$, where $\mathcal T=K\mathcal{R/J}$ and $\mathcal U=K\mathcal{Q/I}$ are path categories of infinity quivers modulo admissible ideals. Finally, we study the case where $\Lambda$ is a path category of a quiver $Q$ with relations and $\mathcal U$ is the full additive subcategory of $\Lambda$ obtained by deleting a source vertex $$ in $Q$ and $\mathcal T=\mathrm{add} {}$. We then show that there exists an adjoint pair of functors $(\mathcal R, \mathcal E)$ between the functor categories $\mathrm{mod} \ \Lambda$ and $\mathrm{mod} \ \mathcal U$ that preserve orthogonality and exceptionality; see \cite{Assem1}. We then give some examples of how to extend classical tilting subcategories of $\mathcal U$-modules to classical tilting subcategories of $\Lambda$-modules.