Gaussian cubature arising from hybrid characters of simple Lie groups

TL;DR

This paper develops new Gaussian and Radau cubature formulas derived from hybrid characters of simple Lie groups with two root lengths, utilizing finite order elements for node placement.

Contribution

It introduces novel cubature formulas based on hybrid Weyl group orbit functions, extending previous Gaussian cubature methods to new cases involving short and long roots.

Findings

New Gaussian cubature formulas for short root cases

New Radau cubature formulas for long root cases

Nodes derived from finite order elements of Lie groups

Abstract

Lie groups with two different root lengths allow two mixed sign homomorphisms on their corresponding Weyl groups, which in turn give rise to two families of hybrid Weyl group orbit functions and characters. In this paper we extend the ideas leading to the Gaussian cubature formulas for families of polynomials arising from the characters of irreducible representations of any simple Lie group, to new cubature formulas based on the corresponding hybrid characters. These formulas are new forms of Gaussian cubature in the short root length case and new forms of Radau cubature in the long root case. The nodes for the cubature arise quite naturally from the (computationally efficient) elements of finite order of the Lie group.