Kashiwara and Saito have a geometric construction of the infinity crystal for any symmetric Kac-Moody algebra. The underlying set consists of the irreducible components of Lusztigs quiver varieties, which are varieties of nilpotent representations of a pre-projective algebra. We generalize this to symmetrizable Kac-Moody algebras by replacing Lusztigs preprojective algebra with a more general one due to Dlab and Ringel. In non-symmetric types we are forced to work over non-algebraically-closed fields.
We have two constructions of the level-$(0,1)$ irreducible representation of the quantum toroidal algebra of type $A$. One is due to Nakajima and Varagnolo-Vasserot. They constructed the representation on the direct sum of the equivariant K-groups of the quiver varieties of type $hat{A}$. The other is due to Saito-Takemura-Uglov and Varagnolo-Vasserot. They constructed the representation on the q-deformed Fock space introduced by Kashiwara-Miwa-Stern. In this paper we give an explicit isomorphism between these two constructions. For this purpose we construct simultaneous eigenvectors on the q-Fock space using nonsymmetric Macdonald polynomials. Then the isomorphism is given by corresponding these vectors to the torus fixed points on the quiver varieties.
Let $mathscr{A}_q$ be the $K$-theoretic Coulomb branch of a $3d$ $mathcal{N}=4$ quiver gauge theory with quiver $Gamma$, and $mathscr{A}_q subseteq mathscr{A}_q$ be the subalgebra generated by the equivariant $K$-theory of a point together with the dressed minuscule monopole operators $M_{varpi_{i,1},f}$ and $M_{varpi^*_{i,1},f}$. In this paper, we construct an associated cluster algebra quiver $mathcal{Q}_Gamma$ and provide an embedding of the subalgebra $mathscr{A}_q$ into the quantized algebra of regular functions on the corresponding cluster variety.
In the present work we study actions of various groups generated by involutions on the category $mathscr O^{int}_q(mathfrak g)$ of integrable highest weight $U_q(mathfrak g)$-modules and their crystal bases for any symmetrizable Kac-Moody algebra $mathfrak g$. The most notable of them are the cactus group and (yet conjectural) Weyl group action on any highest weight integrable module and its lower and upper crystal bases. Surprisingly, some generators of cactus groups are anti-involutions of the Gelfand-Kirillov model for $mathscr O^{int}_q(mathfrak g)$ closely related to the remarkable quantum twists discovered by Kimura and Oya.
We study quantum geometry of Nakajima quiver varieties of two different types - framed A-type quivers and ADHM quivers. While these spaces look completely different we find a surprising connection between equivariant K-theories thereof with a nontrivial match between their equivariant parameters. In particular, we demonstrate that quantum equivariant K-theory of $A_n$ quiver varieties in a certain $ntoinfty$ limit reproduces equivariant K-theory of the Hilbert scheme of points on $mathbb{C}^2$. We analyze the correspondence from the point of view of enumerative geometry, representation theory and integrable systems. We also propose a conjecture which relates spectra of quantum multiplication operators in K-theory of the ADHM moduli spaces with the solution of the elliptic Ruijsenaars-Schneider model.
The quiver Hopf algebras are classified by means of ramification systems with irreducible representations. This leads to the classification of Nichols algebras over group algebras and pointed Hopf algebras of type one.