Matrix Valued Spherical Functions Associated to the Three Dimensional Hyperbolic Space

Spherical functions and rapid decay for hyperbolic groups

We investigate properties of some spherical fonctions defined on hyperbolic groups using boundary representations on the Gromov boundary endowed with the Patterson-Sullivan measure class. We prove sharp decay estimates for spherical functions as well as spectral inequalities associated with boundary representations. This point of view on the boundary allows us to view the so-called \emph{property RD} (also called \emph{Haagerup's inequality}) as a particular case of a more general behavior of spherical functions on hyperbolic groups. In particular, we give a constructive proof using a boundary…

Riesz operators and some spherical representations for hyperbolic groups

We introduce the Riesz operator in the context of Gromov hyperbolic groups in order to investigate a one parameter family of non unitary boundary Hilbertian representations of hyperbolic groups. We prove asymptotic Schur's relations, the latter being the main result of this paper. Up to normalization, the Riesz operator plays the role in the context of hyperbolic groups of the Knapp-Stein intertwiner for complementary series for Lie groups. Assuming the positivity of the Riesz operator, we define an analogue of complementary series for hyperbolic groups and prove their irreducibility.

A sequence of matrix valued orthogonal polynomials associated to spherical functions

The main purpose of this paper is to obtain an explicit expression of a family of matrix valued orthogonal polynomials {P_n}_n, with respect to a weight W, that are eigenfunctions of a second order differential operator D. The weight W and the differential operator D were found in [12], using some aspects of the theory of the spherical functions associated to the complex projective spaces. We also find other second order differential operator E symmetric with respect to W and we describe the algebra generated by D and E.

Matrix elements of irreducible representations of $\mathrm{SU}(n+1)\times\mathrm{SU}(n+1)$ and multivariable matrix-valued orthogonal polynomials

In Part 1 we study the spherical functions on compact symmetric pairs of arbitrary rank under a suitable multiplicity freeness assumption and additional conditions on the branching rules. The spherical functions are taking values in the spaces of linear operators of a finite dimensional representation of the subgroup, so the spherical functions are matrix-valued. Under these assumptions these functions can be described in terms of matrix-valued orthogonal polynomials in several variables, where the number of variables is the rank of the compact symmetric pair. Moreover, these polynomials are u…

Spherical Functions Associated With the Three Dimensional Sphere

In this paper, we determine all irreducible spherical functions Φof any K -type associated to the pair (G,K)=(\SO(4),\SO(3)). This is accomplished by associating to Φa vector valued function H=H(u) of a real variable u, which is analytic at u=0 and whose components are solutions of two coupled systems of ordinary differential equations. By an appropriate conjugation involving Hahn polynomials we uncouple one of the systems. Then this is taken to an uncoupled system of hypergeometric equations, leading to a vector valued solution P=P(u) whose entries are Gegenbauer's polynomials. Afterward, we …

双曲群与球面极小曲面

Hyperbolic groups and spherical minimal surfaces

本文证明了负曲率流形的球面体积等于其基本群作用下单位球面商空间超极限中面积最小化极小曲面的面积，结合度量流理论与无挠双曲群正则表示极限完成证明。

Fischer decomposition for spinor valued polynomials in several variables

It is well-known that polynomials decompose into spherical harmonics. This result is called separation of variables or the Fischer decomposition. In the paper we prove the Fischer decomposition for spinor valued polynomials in $k$ vector variables of ${\mathbb R}^m$ under the stable range condition $m\geq 2k$. Here the role of spherical harmonics is played by monogenic polynomials, that is, polynomial solutions of the Dirac equation in $k$ vector variables.

Cuspidal discrete series for projective hyperbolic spaces

We have in [1] proposed a definition of cusp forms on semisimple symmetric spaces $G/H$, involving the notion of a Radon transform and a related Abel transform. For the real non-Riemannian hyperbolic spaces, we showed that there exists an infinite number of cuspidal discrete series, and at most finitely many non-cuspidal discrete series, including in particular the spherical discrete series. For the projective spaces, the spherical discrete series are the only non-cuspidal discrete series. Below, we extend these results to the other hyperbolic spaces, and we also study the question of when the…

Funciones Esféricas Matriciales Asociadas a las Esferas y a los Espacios Proyectivos Reales

In this work we start by determining all irreducible spherical functions $Φ$ of any $K $-type associated to the pair $(G,K)=(\SO(4),\SO(3))$. The functions $P=P(u)$ corresponding to the irreducible spherical functions of a fixed $K$-type $π_\ell$ are appropriately packaged into a sequence of matrix valued polynomials $(P_w)_{w\ge0}$ of size $(\ell+1)\times(\ell+1)$. Finally we prove that $\widetilde P_w={P_0}^{-1}P_w$ is a sequence of matrix orthogonal polynomials with respect to a weight matrix $W$. Moreover, we show that $W$ admits a second order symmetric hypergeometric operator $\widetilde…

量子矩阵球函数

Quantum Matrix Spherical Functions as Orthogonal Polynomials

本文提出了一种量子矩阵球函数理论，通过将经典三元组转化为量子三元组，得到具有差反射算子代数对角化的向量值正交多项式，并将其与中间Macdonald多项式联系起来。