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Grzegorz Bobinski

Publications and source records attributed to Grzegorz Bobinski.

At least 19 recordsLinked to original sources
arXiv2021

Tangent spaces of orbit closures for representations of Dynkin quivers of type D

Let $\Bbbk$ be an algebraically closed field, $Q$ a finite quiver, and denote by $\mathop{\mathrm{rep}}_Q^{\mathbf{d}}$ the affine $\Bbbk$-scheme of representations of $Q$ with a fixed dimension vector ${\mathbf{d}}$. Given a representation $M$ of $Q$ with dimension vector ${\mathbf{d}}$, the set ${\mathcal{O}}_M$ of points in $\mathop{\mathrm{rep}}_Q^{\mathbf{d}}(\Bbbk)$ isomorphic as representations to $M$ is an orbit under an action on $\mathop{\mathrm{rep}}_Q^{\mathbf{d}}(\Bbbk)$ of a product of general linear groups. The orbit ${\mathcal{O}}_M$ and its Zariski closure $\overline{\mathcal{O}}_M$, considered as reduced subschemes of $\mathop{\mathrm{rep}}_Q^{\mathbf{d}}$, are contained in an affine scheme ${\mathcal{C}}_M$ defined by rank conditions on suitable matrices associated to $\mathop{\mathrm{rep}}_Q^{\mathbf{d}}$. For all Dynkin and extended Dynkin quivers, the sets of points of $\overline{\mathcal{O}}_M$ and ${\mathcal{C}}_M$ coincide, or equivalently, $\overline{\mathcal{O}}_M$ is the reduced scheme associated to ${\mathcal{C}}_M$. Moreover, $\overline{\mathcal{O}}_M={\mathcal{C}}_M$ provided $Q$ is a Dynkin quiver of type ${\mathbb{A}}$, and this equality is a conjecture for the remaining Dynkin quivers (of type ${\mathbb{D}}$ and ${\mathbb{E}}$). Let $Q$ be a Dynkin quiver of type ${\mathbb{D}}$ and $M$ a finite dimensional representation of $Q$. We show that the equality $T_N\overline{\mathcal{O}}_M=T_N{\mathcal{C}}_M$ of Zariski tangent spaces holds for any closed point $N$ of $\overline{\mathcal{O}}_M$. As a consequence, we describe the tangent spaces to $\overline{\mathcal{O}}_M$ in representation theoretic terms.

math.AG↗
arXiv2019

A characterization of representation infinite quiver settings

We characterize pairs (Q,d) consisting of a quiver Q and a dimension vector d, such that over a given algebraically closed field k there are infinitely many representations of Q of dimension vector d. We also present an application of this result to the study of algebras with finitely many orbits with respect to the action of (the double product) of the group of units.

math.RT↗
arXiv2013

On moduli spaces for quasi-tilted algebras

We prove that if a quasi-tilted algebra is tame, then the associated moduli spaces are products of projective spaces. Together with an earlier result of Chindris this gives a geometric characterization of the tame quasi-tilted algebras.

math.RT↗
arXiv2011

Normality of maximal orbit closures for Euclidean quivers

Let Delta be an Euclidean quiver. We prove that the closures of the maximal orbits in the varieties of representations of Delta are normal and Cohen--Macaulay (even complete intersections). Moreover, we give a generalization of this result for the tame concealed-canonical algebras.

math.RT↗
arXiv2009

The graded centers of derived discrete algebras

We describe in the paper the graded centers of the derived categories of the derived discrete algebras. In particular, we prove that if $A$ is a derived discrete algebra, then the reduced part of the graded center of the derived category of $A$ is nontrivial if and only if $A$ has infinite global dimension. Moreover, we show that the nilpotent part of the graded center is controlled by the objects for which the Auslander--Reiten translation coincides with a power of the suspension functor.

math.RT↗