Lemma 8.8 for bound quiver algebras #
lem:dimension-infinity (local-ray-geometry.tex): "Let kQ/(ρ_1, …, ρ_t) be a
finite-dimensional bound quiver algebra, with each relation between radical paths with specified
endpoints. For a nonzero dimension vector d, put D = Σ_v d_v², N = Σ_{a : v → w} d_v d_w,
F = Σ_i d_{source(ρ_i)} d_{target(ρ_i)}. If N − F ≥ D, the algebra is representation-infinite."
The algebra kQ/(ρ) is the category algebra of the relation category kQ/(ρ) (path-order
product). A point x of the representation space (matrices on the arrows) gives the arrow maps
of a representation; the relations evaluate to the matrices relMat x i, whose entries are
F polynomials in the coordinates (relP), vanishing at 0 (the relations have no
length-zero part) and stable under ∏ GL_{d v} (relMat_act). A point of their zero set gives a
functor kQ/(ρ) → Mod k (Φ), hence a right module of dimension Σ d_v (repObj), and
isomorphic modules come from conjugate points (conj_of_iso). Finite representation type would
give finitely many orbits, contradicting OrbitDim.orbits_not_finite
(not_isRepresentationFinite_bound).
The arrows.
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The source of an arrow.
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The target of an arrow.
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The points of the representation space.
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Path matrices #
The matrix of a path at a point (path order: M_{p a} = M_a M_p).
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The generic matrix of an arrow.
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The polynomial matrix of a path.
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The relations #
The matrix of a relation at a point.
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The polynomial matrix of a relation.
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Realization in Mod k #
The space k^{d v}.
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The functor and the module of a point #
The functor kQ/(ρ) → Mod k of a point of the zero set.
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The linear map of a morphism of kQ/(ρ).
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The action of the bound quiver algebra on ⊕_v k^{d v}.
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The right module structure.
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The module of a point.
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The identification with ∏ k^{d v} is k-linear.
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Isomorphisms are conjugations #
The component maps of an isomorphism.
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The component maps as linear maps.
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The arrow relation g_q M_e = M'_e g_p.
Isomorphic modules are conjugate points.
Lemma 8.8 #
The labelled biproducts.
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Lemma 8.8 (lem:dimension-infinity): let kQ/(ρ₁, …, ρ_t) be a finite-dimensional
bound quiver algebra (the category algebra of the relation category, path-order product), each
relation ρ_i : s_i → t_i a combination of paths of positive length. For a nonzero dimension
vector d with N − F ≥ D, i.e. Σ_v d_v² + Σ_i d_{s_i} d_{t_i} ≤ Σ_{a : v → w} d_v d_w, the
algebra is representation-infinite.