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Given a representation of a reductive group, Braverman-Finkelberg-Nakajima have defined a remarkable Poisson variety called the Coulomb branch. Their construction of this space was motivated by considerations from supersymmetric gauge theories and symplectic duality. The coordinate ring of this Coulomb branch is defined as a kind of cohomological Hall algebra; thus it makes sense to develop a type of “Springer theory” to define modules over this algebra. In this talk, we will explain this BFN Springer theory and give many examples. In the toric case, we will see a beautiful combinatorics of polytopes. In the quiver case, we will see connections to the representations of quivers over power series rings. In the general case, we will explore the relations between this Springer theory and quasimap spaces.
[-] Given a representation of a reductive group, Braverman-Finkelberg-Nakajima have defined a remarkable Poisson variety called the Coulomb branch. Their construction of this space was motivated by considerations from supersymmetric gauge theories and symplectic duality. The coordinate ring of this Coulomb branch is defined as a kind of cohomological Hall algebra; thus it makes sense to develop a type of “Springer theory” to define modules over this ...
[+] 81T40 ; 81T60
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y
The algebra $U(gl_n)$ contains a famous and beautiful commutative subalgebra, called the Gelfand-Tsetlin subalgebra. One problem which has attracted great attention over the recent decades is to classify the simple modules on which this subalgebra acts locally finitely (the Gelfand-Tsetlin modules). In investigating this question, Futorny and Ovsienko expanded attention to a generalization of these algebras, saddled with the unfortunate name of “principal Galois orders”. I'll explain how all interesting known examples of these (and some unknown ones, such as the rational Cherednik algebras of $G(l,p,n)!)$ are the Coulomb branches of N = 4 3D gauge theories, and how this perspective allows us to classify the simple Gelfand-Tsetlin modules for $U(gl_n)$ and Cherednik algebras and explain the Koszul duality between Higgs and Coulomb categories O.
[-] The algebra $U(gl_n)$ contains a famous and beautiful commutative subalgebra, called the Gelfand-Tsetlin subalgebra. One problem which has attracted great attention over the recent decades is to classify the simple modules on which this subalgebra acts locally finitely (the Gelfand-Tsetlin modules). In investigating this question, Futorny and Ovsienko expanded attention to a generalization of these algebras, saddled with the unfortunate name of ...
[+] 17B10 ; 17B37
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$T$-structures on derived categories of coherent sheaves are an important tool to encode both representation-theoretic and geometric information. Unfortunately there are only a limited amount of tools available for the constructions of such $t$-structures. We show how certain geometric/categorical quantum affine algebra actions naturally induce $t$-structures on the categories underlying the action. In particular we recover the categories of exotic sheaves of Bezrukavnikov and Mirkovic.
This is joint work with Sabin Cautis.
[-] $T$-structures on derived categories of coherent sheaves are an important tool to encode both representation-theoretic and geometric information. Unfortunately there are only a limited amount of tools available for the constructions of such $t$-structures. We show how certain geometric/categorical quantum affine algebra actions naturally induce $t$-structures on the categories underlying the action. In particular we recover the categories of ...
[+] 14F05 ; 16E35
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Let $G$ be a semisimple algebraic group of adjoint type. The universal centralizer is the family of centralizers in $G$ of regular elements in Lie$(G)$, parametrized by their conjugacy classes. It has a natural symplectic structure, obtained by Hamiltonian reduction from the cotangent bundle $T^∗ G$. We consider a partial compactification of the universal centralizer, where each centralizer fiber is replaced by its closure inside the wonderful compactification of $G$. The symplectic structure extends to a log-symplectic Poisson structure on this partial compactification, whose fibers are isomorphic to regular Hessenberg varieties.
[-] Let $G$ be a semisimple algebraic group of adjoint type. The universal centralizer is the family of centralizers in $G$ of regular elements in Lie$(G)$, parametrized by their conjugacy classes. It has a natural symplectic structure, obtained by Hamiltonian reduction from the cotangent bundle $T^∗ G$. We consider a partial compactification of the universal centralizer, where each centralizer fiber is replaced by its closure inside the wonderful ...
[+] 20G05
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Skein algebras are certain diagrammatically defined algebras spanned by tangles drawn on the cylinder of a surface, with multiplication given by stacking diagrams. Quantum cluster algebras are certain systems of mutually birational quantum tori whose defining relations are encoded in a quiver drawn on the surface. The category of quantum character sheaves is a $q$-deformation of the category of ad-equivariant $D$-modules on the group $G$, expressed through an algebra $D_q (G)$ of “q-difference” operators on $G$.
In this I talk I will explain that these are in fact three sides of the same coin – namely they each arise as different flavors of factorization homology, and hence fit in the framework of four-dimensional topological field theory.
[-] Skein algebras are certain diagrammatically defined algebras spanned by tangles drawn on the cylinder of a surface, with multiplication given by stacking diagrams. Quantum cluster algebras are certain systems of mutually birational quantum tori whose defining relations are encoded in a quiver drawn on the surface. The category of quantum character sheaves is a $q$-deformation of the category of ad-equivariant $D$-modules on the group $G$, ...
[+] 13F60 ; 16TXX ; 17B37 ; 58B32
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I will discuss applications of geometric representation theory to topological and quantum invariants of character stacks. In particular, I will explain how generalized Springer correspondence for class $D$-modules and Koszul duality for Hecke categories encode surprising structure underlying the homology of character stacks of surfaces (joint work with David Ben-Zvi and David Nadler). I will then report on some work in progress with David Jordan and Pavel Safronov concerning a q-analogue of these ideas. The applications include an approach towards Witten's conjecture on the fi dimensionality of skein modules, and methods for computing these dimensions in certain cases.
[-] I will discuss applications of geometric representation theory to topological and quantum invariants of character stacks. In particular, I will explain how generalized Springer correspondence for class $D$-modules and Koszul duality for Hecke categories encode surprising structure underlying the homology of character stacks of surfaces (joint work with David Ben-Zvi and David Nadler). I will then report on some work in progress with David Jordan ...
[+] 14F10 ; 14D23
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y
Character varieties of closed surfaces have a natural Poisson structure whose quantization may be constructed in terms of the corresponding quantum group. When the quantum parameter is a root of unity, this quantization carries a central subalgebra isomorphic to the algebra of functions on the classical character variety. In this talk I will describe a procedure which allows one to obtain Azumaya algebras via quantum Hamiltonian reduction. As an application, I will show that quantizations of character varieties at roots of unity are Azumaya over the corresponding classical character varieties.
This is a report on joint work with Iordan Ganev and David Jordan.
[-] Character varieties of closed surfaces have a natural Poisson structure whose quantization may be constructed in terms of the corresponding quantum group. When the quantum parameter is a root of unity, this quantization carries a central subalgebra isomorphic to the algebra of functions on the classical character variety. In this talk I will describe a procedure which allows one to obtain Azumaya algebras via quantum Hamiltonian reduction. As an ...
[+] 17B63 ; 14F05 ; 14L24 ; 16T20
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In this talk I will give a short overview about fusion rings arising from quantum groups at odd and even roots of unities. These are Grothendieck rings of certain semisimple tensor categories. Then I will study these rings in more detail. The main focus of the talk will be an expectation by Cherednik that there is a certain DAHA action on these rings which can be used to describe the multiplication and semisimplicity of these rings. As a result we present a theorem which makes Cherednik's expectation rigorous.
[-] In this talk I will give a short overview about fusion rings arising from quantum groups at odd and even roots of unities. These are Grothendieck rings of certain semisimple tensor categories. Then I will study these rings in more detail. The main focus of the talk will be an expectation by Cherednik that there is a certain DAHA action on these rings which can be used to describe the multiplication and semisimplicity of these rings. As a result ...
[+] 17B37 ; 20G42
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Puzzles are combinatorial objects developed by Knutson and Tao for computing the expansion of the product of two Grassmannian Schubert classes. I will describe how selfdual puzzles give the restriction of a Grassmannian Schubert class to the symplectic Grassmannian in equivariant cohomology. The proof uses the machinery of quantum integrable systems. Time permitting, I will also discuss some ideas about how to interpret and generalize this result using Lagrangian correspondences and Maulik-Okounkov stable classes.
This is joint work in progress with Allen Knutson and Paul Zinn-Justin.
[-] Puzzles are combinatorial objects developed by Knutson and Tao for computing the expansion of the product of two Grassmannian Schubert classes. I will describe how selfdual puzzles give the restriction of a Grassmannian Schubert class to the symplectic Grassmannian in equivariant cohomology. The proof uses the machinery of quantum integrable systems. Time permitting, I will also discuss some ideas about how to interpret and generalize this ...
[+] 14M15 ; 05E10
English
