Degenerations for modules over representation-finite selfinjective algebras
Immersions of module varieties
We show that a homomorphism of algebras is a categorical epimorphism if and only if all induced morphisms of the associated module varieties are immersions. This enables us to classify all minimal singularities in the subvarieties of modules from homogeneous standard tubes.
Degenerations in the Module Varieties of Generalized Standard Auslander-Reiten Components
An orbit closure for a representation of the Kronecker quiver with bad singularities
We give an example of a representation of the Kronecker quiver for which the closure of the corresponding orbit contains a singularity smoothly equivalent to the isolated singularity of two planes crossing at a point. Therefore this orbit closure is neither Cohen-Macaulay nor unibranch.
Unibranch orbit closures in module varieties
On the numbers of discrete indecomposable modules over tame algebras
Schubert varieties and representations of Dynkin quivers
We show that the types of singularities of Schubert varieties in the flag varieties Flagₙ, n ∈ ℕ, are equivalent to the types of singularities of orbit closures for the representations of Dynkin quivers of type 𝔸. Similarly, we prove that the types of singularities of Schubert varieties in products of Grassmannians Grass(n,a) × Grass(n,b), a, b, n ∈ ℕ, a, b ≤ n, are equivalent to the types of singularities of orbit closures for the representations of Dynkin quivers of type 𝔻. We also show that...
Degenerations for indecomposable modules and tame algebras
On the zero set of semi-invariants for quivers
Modules and quiver representations whose orbit closures are hypersurfaces
Let A be a finitely generated associative algebra over an algebraically closed field. We characterize the finite-dimensional A-modules whose orbit closures are local hypersurfaces. The result is reduced to an analogous characterization for orbit closures of quiver representations obtained in Section 3.
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