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Aslak Bakke Buan

Publications and source records attributed to Aslak Bakke Buan.

At least 19 recordsLinked to original sources
arXiv2024

$τ$-perpendicular wide subcategories

Let $Λ$ be a finite-dimensional algebra. A wide subcategory of $\mathsf{mod}Λ$ is called left finite if the smallest torsion class containing it is functorially finite. In this paper, we prove that the wide subcategories of $\mathsf{mod}Λ$ arising from $τ$-tilting reduction are precisely the Serre subcategories of left finite wide subcategories. As a consequence, we show that the class of such subcategories is closed under further $τ$-tilting reduction. This leads to a natural way to extend the definition of the "$τ$-cluster morphism category" of $Λ$ to arbitrary finite-dimensional algebras. This category was recently constructed by Buan-Marsh in the $τ$-tilting finite case and by Igusa-Todorov in the hereditary case.

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arXiv2022

Mutating signed $τ$-exceptional sequences

We establish some properties of $τ$-exceptional sequences for finite-dimensional algebras. In an earlier paper we established a bijection between the set of ordered support $τ$-tilting modules and the set of complete signed $τ$-exceptional sequences. We describe the action of the symmetric group on the latter induced by its natural action on the former. Similarly, we describe the effect on a $τ$-exceptional sequence obtained by mutating the corresponding ordered support $τ$-tilting module via a construction of Adachi-Iyama-Reiten.

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arXiv2021

Weak cotorsion, $τ$-tilting and two-term categories

Motivated by its links to $τ$-tilting theory, we introduce a generalization of cotorsion pairs in module categories. Such pairs are also linked to co-t-structures in corresponding triangulated categories, and to cotorsion pairs in certain extension closed (and hence extriangulated) subcategories, which we call two-term categories.

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arXiv2021

$τ$-exceptional sequences

We introduce the notions of $τ$-exceptional and signed $τ$-exceptional sequences for any finite dimensional algebra. We prove that for a fixed algebra of rank $n$, and for any positive integer $t \leq n$, there is a bijection between the set of signed $τ$-exceptional sequences of length $t$, and (basic) ordered support $τ$-rigid objects with $t$ indecomposable direct summands. If the algebra is hereditary, our notions coincide with exceptional and signed exceptional sequences. The latter were recently introduced by Igusa and Todorov, who constructed a similar bijection in the hereditary setting.

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arXiv2019

Support varieties - an axiomatic approach

We provide an axiomatic approach for studying support varieties of objects in a triangulated category via the action of a tensor triangulated category, where the tensor product is not necessarily symmetric. This is illustrated by examples, taken in particular from representation theory of finite dimensional algebras.

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arXiv2018

Decorated marked surfaces III: The derived category of a decorated marked surface

We study the Ginzburg dg algebra $Γ_\mathbf{T}$ associated to the quiver with potential arising from a triangulation $\mathbf{T}$ of a decorated marked surface $\mathbf{S}_\bigtriangleup$, in the sense of Qiu. We show that there is a canonical way to identify all finite dimensional derived categories $\mathcal{D}_{fd}(Γ_\mathbf{T})$, denoted by $\mathcal{D}_{fd}(\mathbf{S}_\bigtriangleup)$. As an application, we show that the spherical twist group $\operatorname{ST}(\mathbf{S}_\bigtriangleup)$ associated to $\mathcal{D}_{fd}(\mathbf{S}_\bigtriangleup)$ acts faithfully on its space of stability conditions.

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arXiv2018

A category of wide subcategories

An algebra is said to be \emph{$τ$-tilting finite} provided it has only a finite number of $τ$-rigid objects up to isomorphism. We associate a category to each such algebra. The objects are the wide subcategories of its category of finite dimensional modules, and the morphisms are indexed by support $τ$-tilting pairs.

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arXiv2016

Silted algebras

We study endomorphism algebras of 2-term silting complexes in derived categories of hereditary finite dimensional algebras, or more generally of $\mathop{\rm Ext}\nolimits$-finite hereditary abelian categories. Module categories of such endomorphism algebras are known to occur as hearts of certain bounded $t$-structures in such derived categories. We show that the algebras occurring are exactly the algebras of small homological dimension, which are algebras characterized by the property that each indecomposable module either has injective dimension at most one, or it has projective dimension at most one.

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arXiv2016

Endomorphism algebras of 2-term silting complexes

We study possible values of the global dimension of endomorphism algebras of 2-term silting complexes. We show that for any algebra $A$ whose global dimension $\mathop{\rm gl. dim}\nolimits A\leq 2$ and any 2-term silting complex $\mathbf{P}$ in the bounded derived category ${D^b(A)}$ of $A$, the global dimension of $\mathop{\rm End}\nolimits_{D^b(A)}(\mathbf{P})$ is at most 7. We also show that for each $n>2$, there is an algebra $A$ with $\mathop{\rm gl. dim}\nolimits A=n$ such that ${D^b(A)}$ admits a 2-term silting complex $\mathbf{P}$ with $\mathop{\rm gl. dim}\nolimits \mathop{\rm End}\nolimits_{D^b(A)}(\mathbf{P})$ infinite.

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arXiv2015

A silting theorem

We give a generalization of the classical tilting theorem. We show that for a 2-term silting complex $\mathbf{P}$ in the bounded homotopy category $K^b(\mathop{\rm proj}\nolimits A)$ of finitely generated projective modules of a finite dimensional algebra $A$, the algebra $B = \mathop{\rm End}\nolimits_{K^b(\mathop{\rm proj}\nolimits A)}(\mathbf{P})$ admits a 2-term silting complex $\mathbf{Q}$ with the following properties: (i) The endomorphism algebra of $\mathbf{Q}$ in $K^b(\mathop{\rm proj}\nolimits B)$ is a factor algebra of $A$, and (ii) there are induced torsion pairs in $\mathop{\rm mod}\nolimits A$ and $\mathop{\rm mod}\nolimits B$, such that we obtain natural equivalences induced by $\mathop{\rm Hom}\nolimits$- and $\mathop{\rm Ext}\nolimits$-functors. Moreover, we show how the Auslander-Reiten theory of $\mathop{\rm mod}\nolimits B$ can be described in terms of the Auslander-Reiten theory of $\mathop{\rm mod}\nolimits A$.

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arXiv2015

Algebras of finite representation type arising from maximal rigid objects

We give a complete classification of all algebras appearing as endomorphism algebras of maximal rigid objects in standard 2-Calabi-Yau categories of finite type. Such categories are equivalent to certain orbit categories of derived categories of Dynkin algebras. It turns out that with one exception, all the algebras that occur are $2$-Calabi-Yau-tilted, and therefore appear in an earlier classification by Bertani-Økland and Oppermann. We explain this phenomenon by investigating the subcategories generated by rigid objects in standard 2-Calabi-Yau categories of finite type.

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arXiv2013

Denominators in cluster algebras of affine type

The Fomin-Zelevinsky Laurent phenomenon states that every cluster variable in a cluster algebra can be expressed as a Laurent polynomial in the variables lying in an arbitrary initial cluster. We give representation-theoretic formulas for the denominators of cluster variables in cluster algebras of affine type. The formulas are in terms of the dimensions of spaces of homomorphisms in the corresponding cluster category, and hold for any choice of initial cluster.

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arXiv2013

Torsion pairs and rigid objects in tubes

We classify the torsion pairs in a tube category and show that they are in bijection with maximal rigid objects in the extension of the tube category containing the Pruefer and adic modules. We show that the annulus geometric model for the tube category can be extended to the larger category and interpret torsion pairs, maximal rigid objects and the bijection between them geometrically. We also give a similar geometric description in the case of the linear orientation of a Dynkin quiver of type A.

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arXiv2011

From triangulated categories to module categories via localisation II: Calculus of fractions

We show that the quotient of a Hom-finite triangulated category C by the kernel of the functor Hom(T, -), where T is a rigid object, is preabelian. We further show that the class of regular morphisms in the quotient admit a calculus of left and right fractions. It follows that the Gabriel-Zisman localisation of the quotient at the class of regular morphisms is abelian. We show that it is equivalent to the category of finite dimensional modules over the endomorphism algebra of T in C.

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arXiv2011

From triangulated categories to module categories via localisation

We show that the category of finite-dimensional modules over the endomorphism algebra of a rigid object in a Hom-finite triangulated category is equivalent to the Gabriel-Zisman localisation of the category with respect to a certain class of maps. This generalises the 2-Calabi-Yau tilting theorem of Keller-Reiten, in which the module category is obtained as a factor category, to the rigid case.

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arXiv2011

From m-clusters to m-noncrossing partitions via exceptional sequences

Let W be a finite crystallographic reflection group. The generalized Catalan number of W coincides both with the number of clusters in the cluster algebra associated to W, and with the number of noncrossing partitions for W. Natural bijections between these two sets are known. For any positive integer m, both m-clusters and m-noncrossing partitions have been defined, and the cardinality of both these sets is the Fuss-Catalan number. We give a natural bijection between these two sets by first establishing a bijection between two particular sets of exceptional sequences in the bounded derived category for any finite-dimensional hereditary algebra.

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arXiv2011

Mutation of cluster-tilting objects and potentials

We prove that mutation of cluster-tilting objects in triangulated 2-Calabi-Yau categories is closely connected with mutation of quivers with potentials. This gives a close connection between 2-CY-tilted algebras and Jacobian algebras associated with quivers with potentials. We show that cluster-tilted algebras are Jacobian and also that they are determined by their quivers. There are similar results when dealing with tilting modules over 3-CY algebras. The nearly Morita equivalence for 2-CY-tilted algebras is shown to hold for the finite length modules over Jacobian algebras.

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