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Paper   IPM / M / 18027
School of Mathematics
  Title:   The rigidity of filtered colimits of N-cluster tilting subcategories
  Author(s):  Alireza Nasr-Isfahani (Joint with Z. Fazelpour)
  Status:   To Appear
  Journal: Proc. R. Soc. Edinb., Sect. A, Math.
  Supported by:  IPM
  Abstract:
Let $\Lambda$ be an artin algebra and $\mathcal{M}$ be an $n$-cluster tilting subcategory of $\Lambda$-mod with $n \geq 2$. From the viewpoint of higher homological algebra, a question that naturally arose in [17] is when $\mathcal{M}$ induces an $n$-cluster tilting subcategory of $\Lambda$-Mod. In this paper, we answer this question and explore its connection to Iyamaâ??s question on the finiteness of $n$-cluster tilting subcategories of $\Lambda$-mod. In fact, our theorem reformulates Iyamaâ??s question in terms of the vanishing of Ext; and highlights its relation with the rigidity of filtered colimits of $\mathcal{M}$. Also, we show that ${\rm Add}(\mathcal{M})$ is an $n$-cluster tilting subcategory of $\Lambda$-Mod if and only if ${\rm Add}(\mathcal{M})$ is a maximal $n$-rigid subcategory of $\Lambda$-Mod if and only if $\mathcal{M}$ is of finite type if and only if ${\rm Ext}_{\Lambda}^1({\underrightarrow{\lim}}\mathcal{M}, {\underrightarrow{\lim}}\mathcal{M})=0$. Moreover, we present several equivalent conditions for Iyamaâ??s question which shows the relation of Iyama's question with different subjects in representation theory such as purity and covering theory.

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