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Sachin S. Sharma

Publications and source records attributed to Sachin S. Sharma.

12 recordsLinked to original sources
arXiv2025

The affine Brylinski filtration and $\mathscr{W}$-algebras

The Brylinski-Kostant filtration on a representation of a finite-dimensional semisimple Lie algebra has interpretations in terms of the algebra, geometry and combinatorics of the representation. Its extension to affine Lie algebras was first studied by Slofstra. Recent work of the present authors constructed a Poincaré-Birkhoff-Witt type basis for the dominant weight spaces of the basic representation of affine Lie algebras of type $A$, which is compatible with the affine Brylinski filtration. In this paper, we overcome the constraint of type dependence, and furnish a new, uniform proof which holds for all simply-laced affine Lie algebras.

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arXiv2024

Weyl modules for twisted toroidal Lie algebras

In this paper, we extend the notion of Weyl modules for twisted toroidal Lie algebra $\mathcal{T}(μ)$. We prove that the level one global Weyl modules of $\mathcal{T}(μ)$ are isomorphic to the tensor product of the level one representation of twisted affine Lie algebras and certain lattice vertex algebras. As a byproduct, we calculate the graded character of the level one local Weyl modules of $\mathcal{T}(μ)$.

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arXiv2022

Representations of loop extended Witt algebras

In this paper, we classify irreducible modules for loop extended Witt algebras with finite dimensional weight spaces. They turn out to be either modules with uniformly bounded weight spaces or highest weight modules. We further prove that all these modules are single point evaluation modules ($n \geq 2$). So they are actually irreducible modules for extended Witt algebras.

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arXiv2022

Weyl modules for toroidal Lie algebras

In this paper we study Weyl modules for a toroidal Lie algebra $\CT$ with arbitrary $n$ variables. Using the work of Rao \cite{1995}, we prove that the level one global Weyl modules of $\CT$ are isomorphic to suitable submodules of a Fock space representation of $\CT$ upto a twist. As an application, we compute the graded character of the level one local Weyl module of $\CT$, thereby generalising the work of Kodera \cite{ko}.

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arXiv2021

The Brylinski filtration for affine Kac-Moody algebras and representations of $\mathcal{W}$-algebras

We study the Brylinski filtration induced by a principal Heisenberg subalgebra of an affine Kac-Moody algebra $\mathfrak{g}$, a notion first introduced by Slofstra. The associated graded space of this filtration on dominant weight spaces of integrable highest weight modules of $\mathfrak{g}$ has Hilbert series coinciding with Lusztig's $t$-analogue of weight multiplicities. For the level 1 vacuum module $L(Λ_0)$ of affine Kac-Moody algebras of type $A$, we show that the Brylinski filtration may be most naturally understood in terms of (vertex algebra) representations of the corresponding $\mathcal{W}$-algebra. We show that the dominant weight spaces together form an irreducible Verma module of $\mathcal{W}$ and that the natural PBW basis of this module is compatible with the Brylinski filtration, thereby determining explicitly the subspaces of the filtration. Our basis is the analogue for the principal vertex operator realization of $L(Λ_0)$, of Feigin-Frenkel's basis of $\mathcal{W}$.

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arXiv2020

Integrable modules for loop affine-Virasoro algebra

In this paper we classify the irreducible integrable modules for the loop affine-Virasoro algebra $(( \overset{\circ}{\mathfrak{g}} \otimes \mathbb{C}[t, t^{-1}] \oplus \mathbb{C} K) \rtimes \text{Vir}) \otimes A$, where $A$ is a finitely generated commutative associative algebra with unity.

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arXiv2015

The $t$-analogs of string functions for $A_1^{(1)}$ and Hecke indefinite modular forms

We study generating functions for Lusztig's $t$-analog of weight multiplicities associated to integrable highest weight representations of the simplest affine Lie algebra $A_1^{(1)}$. At $t=1$, these reduce to the {\em string functions} of $A_1^{(1)}$, which were shown by Kac and Peterson to be related to certain Hecke indefinite modular forms. Using their methods, we obtain a description of the general $t$-string function; we show that its values can be realized as radial averages of a certain extension of the Hecke indefinite modular form.

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arXiv2015

The irreducible modules for the derivations of the rational quantum torus

Let $\bbcq$ be the quantum torus associated with the $d \times d$ matrix $q = (q_{ij})$, $q_{ii} = 1$, $q_{ij}^{-1} = q_{ji}$, $q_{ij}$ are roots of unity, for all $1 \leq i, j \leq d.$ Let $\Der(\bbcq)$ be the Lie algebra of all the derivations of $\bbcq$. In this paper we define the Lie algebra $\Der(\bbcq) \ltimes \bbcq$ and classify its modules which are irreducible and have finite dimensional weight spaces. These modules under certain conditions turn out to be of the form $V \otimes \bbcq$, where $V$ is a finite dimensional irreducible $gl_d$-module.

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arXiv2015

Integrable modules for Lie Torus

In the last two decades the structure of Extended Affine Lie algebras (EALA) is extensively studied. In explicitly constructing an EALA, the centerless Lie Torus play an important role. In this paper we consider the Universal central extension of a centerless Lie Torus and classify the irreducible integrable modules for them when the center acts non-trivially. They turn out to be "highest weight modules" for direct sum of finitely many affine Lie algebras.

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arXiv2015

Weyl modules associated to Kac-Moody Lie algebras

Weyl modules were originally defined for affine Lie algebras by Chari and Pressley in \cite{CP}. In this paper we extend the notion of Weyl modules for a Lie algebra $\mathfrak{g} \otimes A$, where $\mathfrak{g}$ is any Kac-Moody algebra and A is any finitely generated commutative associative algebra with unit over $\mathbb{C}$, and prove a tensor product decomposition theorem generalizing \cite{CP}.

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arXiv2012

The t-analog of the basic string function for twisted affine Kac-Moody algebras

We study Lusztig's t-analog of weight multiplicities associated to level one representations of twisted affine Kac-Moody algebras. An explicit closed form expression is obtained for the corresponding t-string function using constant term identities of Macdonald and Cherednik. The closed form involves the generalized exponents of the graded pieces of the twisted affine algebra, considered as modules for the underlying finite dimensional simple Lie algebra. This extends previous work on level 1 t-string functions for the untwisted simply-laced affine Kac-Moody algebras.

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