Reduced quiver quantum toroidal algebras
Andrei Neguţ
TL;DR
The paper provides a concrete generators-and-relations description of reduced quiver quantum toroidal algebras acting on BPS crystal spaces for toric Calabi-Yau threefolds. Using a shuffle-algebra realization and the notion of shrubby quivers, it proves that for shrubby $Q$ the kernel of the shuffle map is generated by coefficients of face-associated series $e_F$, giving an explicit Serre-like presentation of the reduced positive (and negative) halves. In the $X=\mathbb{C}^3$ example, this yields a cubic relation together with two face-wheel relations and ties the reduced algebra to the localized K-theoretic Hall algebra via a wheel-vanishing subspace $\mathcal{S}^+$. The results thereby deliver a tractable, torsion-free presentation for reduced quiver quantum toroidal algebras and illuminate their connection to BPS algebras, brane tilings, and $K$-theoretic Hall algebras on toric Calabi-Yau geometries.
Abstract
We give a generators-and-relations description of the reduced versions of quiver quantum toroidal algebras, which act on the spaces of BPS states associated to (non-compact) toric Calabi-Yau threefolds X. As an application, we obtain a description of the K-theoretic Hall algebra of (the quiver with potential associated to) X, modulo torsion.
