We consider compact Grassmann manifolds G/K over the real, complex or quaternionic numbers whose spherical functions are Heckman–Opdam polynomials of type BC. From an explicit integral representation of these polynomials we deduce a sharp Mehler–Heine formula, that is an approximation of the Heckman–Opdam polynomials in terms of Bessel functions, with a precise estimate on the error term. This ...

In this paper we present an addition to Askey’s scheme of q-hypergeometric orthogonal polynomials involving classes of q-special functions which do not consist of polynomials only. The special functions are q-analogues of the Jacobi and Bessel function. The generalised orthogonality relations and the second order q-difference equations for these families are given. Limit transitions between the...

In this paper we present an addition to Askey’s scheme of q-hypergeometric orthogonal polynomials involving classes of q-special functions which do not consist of polynomials only. The special functions are q-analogues of the Jacobi and Bessel function. The generalised orthogonality relations and the second order q-difference equations for these families are given. Limit transitions between the...

In this paper, we study Bessel processes of dimension δ ≡ 2(1 − μ), with 0 < δ < 2, and some related martingales and random times. Our approach is based on martingale techniques and the general theory of stochastic processes (unlike the usual approach based on excursion theory), although for 0 < δ < 1, these processes are even not semimartingales. The last time before 1 when a Bessel process hi...

Trapezoid maps are a kind of continuous and piecewise linear maps with a flat top. By the conjugacy relationship, we present a complete classification for four families of trapezoid maps. Firstly, using an extension method, we construct all homeomorphic solutions of conjugacy equation φ ◦ f = g ◦ φ for some non-monotone continuous maps f and g. Secondly, using an iterative construction method a...

In this paper we prove $$L^p$$ estimates for Stein’s square functions associated with Fourier–Bessel expansions. Furthermore, transference results from series to Hankel transforms. Actually, these are vector-valued multipliers discrete continuous in the Bessel setting. As a consequence, deduce sharpness of range p -boundedness corresponding property Hankel–Stein functions. Finally, that ones ha...