79 research outputs found
Hilbert-Schmidt Operators vs. Integrable Systems of Elliptic Calogero-Moser Type III. The Heun Case
The Heun equation can be rewritten as an eigenvalue equation for an ordinary
differential operator of the form , where the potential is an
elliptic function depending on a coupling vector .
Alternatively, this operator arises from the specialization of the
elliptic nonrelativistic Calogero-Moser system (a.k.a. the Inozemtsev
system). Under suitable restrictions on the elliptic periods and on , we
associate to this operator a self-adjoint operator on the Hilbert space
, where is the real period of
. For this association and a further analysis of , a certain
Hilbert-Schmidt operator on plays a critical
role. In particular, using the intimate relation of and , we obtain a remarkable spectral invariance: In terms of a coupling
vector that depends linearly on , the spectrum of
is invariant under arbitrary permutations ,
Relativistic Lamé functions: Completeness vs. polynomial asymptotics
AbstractIn earlier work we introduced and studied two commuting generalized Lamé operators, obtaining in particular joint eigenfunctions for a dense set in the natural parameter space. Here we consider these difference operators and their eigenfunctions in relation to the Hilbert space L2((0, π/r), w(x)dx), with r > 0 and the weight function w(x) a ratio of elliptic gamma functions. In particular, we show that the previously known pairwise orthogonal joint eigenfunctions need only be supplemented by finitely many new ones to obtain an orthogonal base. This completeness property is derived by exploiting recent results on the large-degree Hilbert space asymptotics of a class of orthonormal polynomials. The polynomials pn(cos(rx)), n ϵN, that are relevant in the Lamé setting are orthonormal in L2((0, π/r), wP(x)dx), with wp(x) closely related to w(x)
On Barnes' multiple zeta and gamma functions
AbstractWe show how various known results concerning the Barnes multiple zeta and gamma functions can be obtained as specializations of simple features shared by a quite extensive class of functions. The pertinent functions involve Laplace transforms, and their asymptotics is obtained by exploiting this. We also demonstrate how Barnes' multiple zeta and gamma functions fit into a recently developed theory of minimal solutions to first order analytic difference equations. Both of these new approaches to the Barnes functions give rise to novel integral representations
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