English

Inversion formula and range conditions for a vector multi-interval finite Hilbert transform in $L^2$

Functional Analysis 2018-06-04 v1

Abstract

Given nn disjoint intervals IjI_j, on R\mathbb R together with nn functions ψjL2(Ij)\psi_j\in L^2(I_j), j=1,nj=1,\dots n, and an n×nn\times n matrix Θ\Theta, the problem is to find an L2L^2 solution φ=Col(φ1,,φn)\vec \varphi= {\rm Col} (\varphi_1,\dots, \varphi_n), φjL2(Ij)\varphi_j \in L^2(I_j) to the linear system χΘHφ=ψ\chi\Theta \mathcal H \vec \varphi = \vec\psi, where H=diag(H1,,Hn)\mathcal H = {\rm diag} (\mathcal H_1 ,\dots, \mathcal H_n) is a matrix of finite Hilbert transforms and χ=diag(χ1,,χn)\chi=\text{diag}(\chi_1,\dots,\chi_n) is a matrix of the corresponding characteristic functions on IjI_j, and ψ=Col(ψ1,,ψn)\vec \psi={\rm Col} (\psi_1,\dots,\psi_n). Since we can interpret χΘHφ\chi\Theta \mathcal H \vec \varphi as a generalized vector multi-interval finite Hilbert transform, we call the formula for the solution as "the inversion formula" and the necessary and sufficient conditions for the existence of a solution as the "range conditions". In this paper we derive the explicit inversion formula and the range conditions in two specific cases: a) the matrix Θ\Theta is symmetric and positive definite, and; b) all the entries of Θ\Theta are equal to one. We also prove the uniqueness of solution, that is, that our transform is injective. When the matrix Θ\Theta is positive definite, the inversion formula is given in terms of the solution of the associated matrix Riemann-Hilbert Problem. We also discuss other cases of the matrix Θ\Theta.

Cite

@article{arxiv.1806.00436,
  title  = {Inversion formula and range conditions for a vector multi-interval finite Hilbert transform in $L^2$},
  author = {Alexander Katsevich and Marco Bertola and Alexander Tovbis},
  journal= {arXiv preprint arXiv:1806.00436},
  year   = {2018}
}

Comments

18 pages

R2 v1 2026-06-23T02:16:24.526Z