scholarly journals JOSEPH IDEALS AND LISSE MINIMAL -ALGEBRAS

2016 ◽  
Vol 17 (2) ◽  
pp. 397-417 ◽  
Author(s):  
Tomoyuki Arakawa ◽  
Anne Moreau
Keyword(s):  
Nilpotent Orbit ◽  
Vertex Algebras ◽  
Orbit Closure ◽  
New Family ◽  
Orbit Closures

We consider a lifting of Joseph ideals for the minimal nilpotent orbit closure to the setting of affine Kac–Moody algebras and find new examples of affine vertex algebras whose associated varieties are minimal nilpotent orbit closures. As an application we obtain a new family of lisse ($C_{2}$-cofinite)$W$-algebras that are not coming from admissible representations of affine Kac–Moody algebras.

scholarly journals Poincaré polynomials of generic torus orbit closures in Schubert varieties

2021 ◽  
pp. 189-208
Author(s):  
Eunjeong Lee ◽  
Mikiya Masuda ◽  
Seonjeong Park ◽  
Jongbaek Song
Keyword(s):  
Schubert Variety ◽  
Flag Variety ◽  
Schubert Varieties ◽  
Orbit Closure ◽  
Poincaré Polynomial ◽  
Content Type ◽  
Eulerian Polynomial ◽  
Orbit Closures

The closure of a generic torus orbit in the flag variety G / B G/B of type  A A is known to be a permutohedral variety, and its Poincaré polynomial agrees with the Eulerian polynomial. In this paper, we study the Poincaré polynomial of a generic torus orbit closure in a Schubert variety in  G / B G/B . When the generic torus orbit closure in a Schubert variety is smooth, its Poincaré polynomial is known to agree with a certain generalization of the Eulerian polynomial. We extend this result to an arbitrary generic torus orbit closure which is not necessarily smooth.

Nilpotent Orbit Varieties and the Atomic Decomposition of the Q-Kostka Polynomials

1998 ◽  
Vol 50 (3) ◽  
pp. 525-537 ◽  
Author(s):  
William Brockman ◽  
Mark Haiman
Keyword(s):  
Atomic Decomposition ◽  
Jordan Block ◽  
Geometric Interpretation ◽  
Nilpotent Orbit ◽  
Cohomology Rings ◽  
Direct Sum ◽  
Kostka Polynomials ◽  
Orbit Closures ◽  
Direct Sum Decomposition ◽  
Coordinate Rings

AbstractWe study the coordinate rings of scheme-theoretic intersections of nilpotent orbit closures with the diagonal matrices. Here μ′ gives the Jordan block structure of the nilpotent matrix. de Concini and Procesi [5] proved a conjecture of Kraft [12] that these rings are isomorphic to the cohomology rings of the varieties constructed by Springer [22, 23]. The famous q-Kostka polynomial is the Hilbert series for the multiplicity of the irreducible symmetric group representation indexed by λ in the ring . Lascoux and Schützenberger [15, 13] gave combinatorially a decomposition of as a sum of “atomic” polynomials with non-negative integer coefficients, and Lascoux proposed a corresponding decomposition in the cohomology model.Our work provides a geometric interpretation of the atomic decomposition. The Frobenius-splitting results of Mehta and van der Kallen [19] imply a direct-sum decomposition of the ideals of nilpotent orbit closures, arising from the inclusions of the corresponding sets. We carry out the restriction to the diagonal using a recent theorem of Broer [3]. This gives a direct-sum decomposition of the ideals yielding the , and a new proof of the atomic decomposition of the q-Kostka polynomials.

scholarly journals Normality of orbit closures in the enhanced nilpotent cone

2011 ◽  
Vol 203 ◽  
pp. 1-45 ◽  
Author(s):  
Pramod N. Achar ◽  
Anthony Henderson ◽  
Benjamin F. Jones
Keyword(s):  
Nilpotent Orbit ◽  
Complete Intersections ◽  
Quiver Variety ◽  
Quiver Varieties ◽  
Nilpotent Cone ◽  
Orbit Closures ◽  
Special Cases

AbstractWe continue the study of the closures of GL(V)-orbits in the enhanced nilpotent cone V × N begun by the first two authors. We prove that each closure is an invariant-theoretic quotient of a suitably defined enhanced quiver variety. We conjecture, and prove in special cases, that these enhanced quiver varieties are normal complete intersections, implying that the enhanced nilpotent orbit closures are also normal.

scholarly journals NILPOTENT SUBSPACES AND NILPOTENT ORBITS

2018 ◽  
Vol 106 (1) ◽  
pp. 104-126
Author(s):  
DMITRI I. PANYUSHEV ◽  
OKSANA S. YAKIMOVA
Keyword(s):  
Algebraic Group ◽  
Lie Algebra ◽  
Upper Bound ◽  
Nilpotent Orbit ◽  
Orbit Closure ◽  
Maximal Dimension ◽  
Nilpotent Orbits ◽  
Minimal Dimension ◽  
Semisimple Complex ◽  
Stable Subspace

Let $G$ be a semisimple complex algebraic group with Lie algebra $\mathfrak{g}$. For a nilpotent $G$-orbit ${\mathcal{O}}\subset \mathfrak{g}$, let $d_{{\mathcal{O}}}$ denote the maximal dimension of a subspace $V\subset \mathfrak{g}$ that is contained in the closure of ${\mathcal{O}}$. In this note, we prove that $d_{{\mathcal{O}}}\leq {\textstyle \frac{1}{2}}\dim {\mathcal{O}}$ and this upper bound is attained if and only if ${\mathcal{O}}$ is a Richardson orbit. Furthermore, if $V$ is $B$-stable and $\dim V={\textstyle \frac{1}{2}}\dim {\mathcal{O}}$, then $V$ is the nilradical of a polarisation of ${\mathcal{O}}$. Every nilpotent orbit closure has a distinguished $B$-stable subspace constructed via an $\mathfrak{sl}_{2}$-triple, which is called the Dynkin ideal. We then characterise the nilpotent orbits ${\mathcal{O}}$ such that the Dynkin ideal (1) has the minimal dimension among all $B$-stable subspaces $\mathfrak{c}$ such that $\mathfrak{c}\cap {\mathcal{O}}$ is dense in $\mathfrak{c}$, or (2) is the only $B$-stable subspace $\mathfrak{c}$ such that $\mathfrak{c}\cap {\mathcal{O}}$ is dense in $\mathfrak{c}$.

scholarly journals Generic singularities of nilpotent orbit closures

2017 ◽  
Vol 305 ◽  
pp. 1-77 ◽  
Author(s):  
Baohua Fu ◽  
Daniel Juteau ◽  
Paul Levy ◽  
Eric Sommers
Keyword(s):  
Nilpotent Orbit ◽  
Orbit Closures ◽  
Generic Singularities

scholarly journals ON THE GEOMETRY OF ORBIT CLOSURES FOR REPRESENTATION-INFINITE ALGEBRAS

2012 ◽  
Vol 54 (3) ◽  
pp. 629-636 ◽  
Author(s):  
CALIN CHINDRIS
Keyword(s):  
Orbit Closure ◽  
Kronecker Algebra ◽  
Orbit Closures ◽  
Preprojective Component ◽  
Infinite Algebras

AbstractFor the Kronecker algebra, Zwara found in [14] an example of a module whose orbit closure is neither unibranch nor Cohen-Macaulay. In this paper, we explain how to extend this example to all representation-infinite algebras with a preprojective component.

scholarly journals On Quiver Grassmannians and Orbit Closures for Gen-Finite Modules

2021 ◽  
Author(s):  
Matthew Pressland ◽  
Julia Sauter
Keyword(s):  
Orbit Closure ◽  
Finite Dimensional Algebra ◽  
Tilting Module ◽  
Endomorphism Rings ◽  
Dimensional Algebra ◽  
Indecomposable Modules ◽  
Quiver Grassmannians ◽  
Finite Dimensional ◽  
Orbit Closures ◽  
Endomorphism Algebras

AbstractWe show that endomorphism rings of cogenerators in the module category of a finite-dimensional algebra A admit a canonical tilting module, whose tilted algebra B is related to A by a recollement. Let M be a gen-finite A-module, meaning there are only finitely many indecomposable modules generated by M. Using the canonical tilts of endomorphism algebras of suitable cogenerators associated to M, and the resulting recollements, we construct desingularisations of the orbit closure and quiver Grassmannians of M, thus generalising all results from previous work of Crawley-Boevey and the second author in 2017. We provide dual versions of the key results, in order to also treat cogen-finite modules.

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