Abstract

We study the affine schemes of modules over gentle algebras. We describe the smooth points of these schemes, and we also analyze their irreducible components in detail. Several of our results generalize formerly known results, e.g. by dropping acyclicity, and by incorporating band modules. A special class of gentle algebras are Jacobian algebras arising from triangulations of unpunctured marked surfaces. For these we obtain a bijection between the set of generically tau -reduced decorated irreducible components and the set of laminations of the surface. As an application, we get that the set of bangle functions (defined by Musiker–Schiffler–Williams) in the upper cluster algebra associated with the surface coincides with the set of generic Caldero-Chapoton functions (defined by Geiß–Leclerc–Schröer).

Highlights

  • Introduction and main resultsWe study some geometric aspects of the representation theory of gentle algebras

  • Gentle algebras are special biserial, which implies that their module categories can be described combinatorially, see [56] and [11]

  • The generically τ -reduced decorated components parametrize the generic CalderoChapoton functions, which belong to the coefficient-free upper cluster algebra U(S,M) associated with (S, M)

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Summary

Overview

We study some geometric aspects of the representation theory of gentle algebras. This class of finite-dimensional algebras was defined by Assem and Skowronski [5], who were classifying the iterated tilted algebras of path algebras of extended Dynkin type A. A special class of gentle algebras are Jacobian algebras arising from triangulations of unpunctured marked surfaces (S, M) For these we obtain a bijection between the set of generically τ -reduced decorated irreducible components and the set of laminations of the surface. The generically τ -reduced decorated components parametrize the generic CalderoChapoton functions, which belong to the coefficient-free upper cluster algebra U(S,M) associated with (S, M) In many cases, these generic Caldero-Chapoton functions are known to form a basis, called the generic basis, of U(S,M), see for example [30] and [49]. We use the bijection mentioned above to show that the generic basis coincides with Musiker–Schiffler–Williams’ bangle basis (see [45, Corollary 1.3]) of the coefficient-free cluster algebra A(S,M) associated with (S, M) It is known in most cases (for example, if |M| ≥ 2) that A(S,M) = U(S,M), see [42,43]. In the following subsections we describe our results in more detail

Gentle algebras
Smooth locus and generic reducedness of module schemes
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Band components
Laminations of marked surfaces and generically -reduced components
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Overall structure of the article
Scheme of modules
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Canonical decompositions of irreducible components
Generically -reduced components for tame algebras
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The maps and "
Strings
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String modules
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Classification of modules
Homomorphisms
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Auslander-Reiten translation of string modules
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5.10 Auslander-Reiten formulas
5.11 Rank functions for gentle algebras
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Schemes of complexes
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Rigid and -rigid modules
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Generic reducedness and singular locus
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Irreducible components
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String and band components and generic decompositions
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Generically reduced components
Singular locus
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Simple summands of restrictions
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Decorated modules
Schemes of decorated modules
E-invariants and g-vectors of decorated modules
Generically -reduced decorated components
Decomposition of generically -reduced components
10.1 Marked surfaces
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10.3 Laminations and triangulations
10.4 Curves and loops as combinatorial objects
10.5 From triangulations to gentle Jacobian algebras
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10.7 Rotation of curves and the Auslander-Reiten translation
10.8 Three types of intersections
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10.10 Shear coordinates and g-vectors
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11.2 MSW-functions
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11.3 Dual CC-functions and MSW-functions
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11.4 Bangle functions are generic
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12 An example
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Full Text
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