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    Acyclic cluster algebras with dense gg-vector fans

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    The gg-vector fans play an important role in studying cluster algebras and silting theory. We survey cluster algebras with dense gg-vector fans and show that a connected acyclic cluster algebra has a dense gg-vector fan if and only if it is either finite type or affine type. As an application, we classify finite dimensional hereditary algebras with dense gg-vector fans.23 page

    Wide subcategories are semistable

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    For an arbitrary finite dimensional algebra Λ\Lambda, we prove that any wide subcategory of modΛ\mathsf{mod} \Lambda satisfying a certain finiteness condition is θ\theta-semistable for some stability condition θ\theta. More generally, we show that wide subcategories of modΛ\mathsf{mod} \Lambda associated with two-term presilting complexes of Λ\Lambda are semistable. This provides a complement for Ingalls-Thomas-type bijections for finite dimensional algebras.Comment: 8 page

    Dimension vectors of ττ-rigid modules and ff-vectors of cluster monomials from triangulated surfaces

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    For the cluster algebra A\mathcal{A} associated with a triangulated surface, we give a characterization of the triangulated surface such that different non-initial cluster monomials in A\mathcal{A} have different ff-vectors. Similarly, for the associated Jacobian algebra JJ, we give a characterization of the triangulated surface such that different ττ-rigid JJ-modules have different dimension vectors. Moreover, we also show that different basic support ττ-tilting JJ-modules have different dimension vectors. Our main ingredient is a notion of intersection numbers defined by Qiu and Zhou. As an application, we show that the denominator conjecture holds for A\mathcal{A} if the marked surface is a closed surface with exactly one puncture, or the given tagged triangulation has neither loops nor tagged arcs connecting punctures.45 page

    Denominator vectors and dimension vectors from triangulated surfaces

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    In a categorification of skew-symmetric cluster algebras, each cluster variable corresponds with an indecomposable module over the associated Jacobian algebra. Buan, Marsh and Reiten studied when the denominator vector of each cluster variable in an acyclic cluster algebra coincides with the dimension vector of the corresponding module. In this paper, we give analogues of their results for cluster algebras from triangulated surfaces by comparing two kinds of intersection numbers of tagged arcs.20 pages, v2: minor correction

    Denseness of gg-vector cones from weighted orbifolds

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    We study gg-vector cones in a cluster algebra defined from a weighted orbifold of rank nn introduced by Felikson, Shapiro and Tumarkin. We determine the closure of the union of the gg-vector cones. It is equal to Rn\mathbb{R}^n except for a weighted orbifold with empty boundary and exactly one puncture, in which case it is equal to the half space of a certain explicit hyperplane in Rn\mathbb{R}^n.Comment: 21 pages. this article draws heavily from arXiv:1904.12479, v2: minor correction

    Combinatorial cluster expansion formulas from triangulated surfaces

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    We give a cluster expansion formula for cluster algebras with principal coefficients defined from triangulated surfaces in terms of perfect matchings of angles. Our formula simplifies the cluster expansion formula given by Musiker-Schiffler-Williams in terms of perfect matchings of snake graphs. A key point of our proof is to give a bijection between perfect matchings of angles in some triangulated polygon and perfect matchings of the corresponding snake graph. Moreover, they also correspond bijectively with perfect matchings of the corresponding bipartite graph and minimal cuts of the corresponding quiver with potential.31 page

    Erratum to: Tame Algebras Have Dense g-Vector Fans

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    International audienceWhen this paper first published online, it contained a number of errors, which have nowbeen corrected online.The original paper did not clearly state that Pierre-Guy Plamondon and ToshiyaYurikusa were the author of the paper, but that Bernhard Keller was the author of theappendix.A dedication to the memory of Andrzej Skowronski was missin

    Going Beyond Counting First Authors in Author Co-citation Analysis

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    The present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed

    FF-matrices of cluster algebras from triangulated surfaces

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    For a given marked surface (S,M)(S,M) and a fixed tagged triangulation TT of (S,M)(S,M), we show that each tagged triangulation TT' of (S,M)(S,M) is uniquely determined by the intersection numbers of tagged arcs of TT and tagged arcs of TT'. As consequence, each cluster in the cluster algebra A(T)\mathcal{A}(T) is uniquely determined by its FF-matrix which is a new numerical invariant of the cluster introduced by Fujiwara and Gyoda.Comment: 33 page
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