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Erik Koelink

Publications and source records attributed to Erik Koelink.

61 records · Page 4Linked to original sources
arXiv1994

Spectral analysis and the Haar functional on the quantum SU(2) group

The Haar functional on the quantum $SU(2)$ group is the analogue of invariant integration on the group $SU(2)$. If restricted to a subalgebra generated by a self-adjoint element the Haar functional can be expressed as an integral with a continuous measure or with a discrete measure or by a combination of both. These results by Woronowicz and Koornwinder have been proved by using the corepresentation theory of the quantum $SU(2)$ group and Schur's orthogonality relations for matrix elements of irreducible unitary corepresentations. These results are proved here by using a spectral analysis of the generator of the subalgebra. The spectral measures can be described in terms of the orthogonality measures of orthogonal polynomials by using the theory of Jacobi matrices.

math.QA↗
arXiv1994

Addition formula for 2-parameter family of Askey-Wilson polynomials

For a two parameter family of Askey-Wilson polynomials, that can be regarded as basic analogues of the Legendre polynomials, an addition formula is derived. The addition formula is a two-parameter extension of Koornwinder's addition formula for the little $q$-Legendre polynomials. A corresponding product formula is derived. As the base tends to one, the addition and product formula go over into the addition and product formula for the Legendre polynomial. The addition formula is derived from the interpretation of Askey-Wilson polynomials as generalised matrix elements on the quantum $SU(2)$ group.

math.CA↗
arXiv1994

On Jacobi and continuous Hahn polynomials

Jacobi polynomials are mapped onto the continuous Hahn polynomials by the Fourier transform and the orthogonality relations for the continuous Hahn polynomials then follow from the orthogonality relations for the Jacobi polynomials and the Parseval formula. In a special case this relation dates back to work by Bateman in 1933 and we follow a part of the historical development for these polynomials. Some applications of this relation are given.

math.CA↗
arXiv1994

Yet another basic analogue of Graf's addition formula

An identity involving basic Bessel functions and Al-Salam--Chihara polynomials is proved for which we recover Graf's addition formula for the Bessel function as the base $q$ tends to $1$. The corresponding product formula is derived. Some known identities for Jackson's $q$-Bessel functions are obtained as limiting cases. As special cases we prove identities for $q$-Charlier polynomials.

math.CA↗
arXiv1994

Askey-Wilson polynomials and the quantum SU(2) group: survey and applications

Generalised matrix elements of the irreducible representations of the quantum $SU(2)$ group are defined using certain orthonormal bases of the representation space. The generalised matrix elements are relatively infinitesimal invariant with respect to Lie algebra like elements of the quantised universal enveloping algebra of $sl(2)$. A full proof of the theorem announced by Noumi and Mimachi [Proc. Japan Acad. Sci. {\bf 66}, Ser. A (1990), pp. 146--149] describing the generalised matrix elements in terms of the full four-parameter family of Askey-Wilson polynomials is given. Various known and new applications of this interpretation are presented.

math.QA↗
arXiv1994

Addition formula for big q-Legendre polynomials

From Koornwinder's interpretation of big $q$-Legendre polynomials as spherical elements on the quantum $SU(2)$ group an addition formula is derived for the big $q$-Legendre polynomial. The formula involves Al-Salam--Carlitz polynomials, little $q$-Jacobi polynomials and dual $q$-Krawtchouk polynomials. For the little $q$-ultraspherical polynomials a product formula in terms of a big $q$-Legendre polynomial follows by $q$-integration. The addition and product formula for the Legendre polynomials are obtained when $q$ tends to 1.

math.QA↗