Calderón sum formula conjecture for discrete wavelet frames

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Let AA be an invertible matrix, let Γ\Gamma be a lattice in Rn\mathbb{R}^n, let B=ATB=A^T, and let Ψ=ψ1,…,ψL\Psi=\\{\psi_1,\dots,\psi_L\\} generate the wavelet system A(Ψ,A,Γ)\mathcal{A}(\Psi,A,\Gamma). A wavelet system is formed from the dilates and lattice translates of the functions in Ψ\Psi. Calderón sum formula conjecture. If A(Ψ,A,Γ)\mathcal{A}(\Psi,A,\Gamma) is an orthonormal basis, or more generally a Parseval frame, for L2(Rn)L^2(\mathbb{R}^n), then

∑l=1L∑j∈Z∣ψ^l(B−jξ)∣2=1\sum_{l=1}^L \sum_{j\in \mathbb{Z}} |\hat\psi_l(B^{-j}\xi)|^2=1

for almost every ξ∈Rn\xi\in\mathbb{R}^n. The formula is known when the lattice counting estimate holds, and hence in one dimension, but remains open in general; it is also known for continuous wavelet systems. In particular, it is not known whether the discrete orthonormal or Parseval-frame hypothesis alone forces ∣det⁡A∣≠1|\det A|\ne 1.

References

Primary source

Marcin Bownik and Jakob Lemvig, “Wavelets for non-expanding dilations and the lattice counting estimate”, arXiv:1601.07114 (2016).

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