Sufficiency of weak Hilbert-transform estimates in the absolutely continuous case

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Let AA be the indefinite Sturm–Liouville operator, assume

σdisc⁡(A)=∅,\sigma_{\operatorname{disc}}(A)=\emptyset,

and suppose that both spectral measures dΣ+d\Sigma_+ and dΣ−d\Sigma_- are absolutely continuous, so that Σ±=Σac⁡±\Sigma_\pm=\Sigma_{\operatorname{ac}\pm}. Let and denote the corresponding weak two-weight estimates for the Hilbert transform.

Absolutely continuous sufficiency conjecture. Under these assumptions, the conditions and are sufficient for AA to be similar to a selfadjoint operator.

This is a special-case sufficiency claim stated after the broader conjecture. The supplied material gives no resolution status, so it is recorded as open.

References

Primary source

I. M. Karabash and M. M. Malamud, “Indefinite Sturm-Liouville operators (x) (- d^2dx^2 +q(x)) with finite-zone potentials”, arXiv:math/0610087 (2006).

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