arXiv subjects

Stein Meereboer

Publications and source records attributed to Stein Meereboer.

4 recordsLinked to original sources

arXiv2026

Quantum spherical functions of type $χ$ as Macdonald-Koornwinder polynomials

The theory of quantum symmetric pairs is applied to $q$-special functions. Previous work shows the existence of a family $χ$-spherical functions indexed by the integers for each Hermitian quantum symmetric pair. A distinguished family of such functions, invariant under the Weyl group of the restricted roots, is shown to be a family of Macdonald-Koornwinder polynomials if the restricted root system is reduced or if the Satake diagram is of type $\mathsf{AIII_a}$.

math.RT↗

arXiv2026

Quantum Matrix Spherical Functions as Orthogonal Polynomials

A general theory of matrix-spherical functions for dual Hopf algebras and right coideal subalgebras is developed. We establish their existence and define their orthogonality relations. When specialized to Kolb and Letzter's quantum symmetric pair coideal subalgebras, we associate, to each classical commutative triple, a unique corresponding quantum commutative triple. This leads to families of vector-valued orthogonal polynomials, which diagonalize a commutative algebra of difference-reflection operators and are invariant under sending $q \mapsto q^{-1}$. Various examples of these vector-valued orthogonal polynomials are given and identified with Intermediate Macdonald polynomials

math.QA↗

arXiv2025

Based morphisms for characters of quantum symmetric pairs

We study based one-dimensional modules of quantum symmetric pairs over the field $\mathbb{Q}(q)$. We provide a complete classification of one-dimensional $\mathbf{B}$-modules that appear as submodules of simple finite-dimensional based $\mathbf{U}$-modules and determine the corresponding branching rules. The main result of this paper shows that the corresponding projections are morphisms of based $\mathbf{B}$-modules. To this end we characterize one-dimensional modules at $q=\infty$, thus developing a $\imath$crystal basis theory for these modules. This is then applied to show compatibility with the integral forms of the (dual-)canonical basis.

math.QA↗

arXiv2025

Symmetries for spherical functions of type $χ$ for quantum symmetric pairs

Let $\mathfrak{g}$ be a complex semisimple Lie algebra and let $\mathbf{U}_q(\mathfrak{g})$ denote the associated Drinfel'd Jimbo quantized enveloping algebra. In this paper we study spherical functions of $\mathbf{U}_q(\mathfrak{g})$ related to characters. We show invariance under the Wang-Zhang braid group operators and show relative Weyl group invariance, when restricted to the quantum torus.

math.RT↗