Fong–Tsui conjecture for bounded operators

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Let TT be a bounded operator on a complex Hilbert space. Write

Re⁡T=T+T∗2\operatorname{Re} T=\frac{T+T^*}{2}

for its real part, and let ∣T∣|T| denote the positive square root of T∗TT^*T.

Fong–Tsui conjecture. If

∣T∣≤∣Re⁡T∣,|T|\leq |\operatorname{Re} T|,

then TT is self-adjoint.

This conjecture asks whether domination of the absolute value of a bounded operator by the absolute value of its real part forces self-adjointness. It was proposed as a strengthening of an earlier result of Fong and Istrătescu; the supplied source treats it as an open question.

References

Primary source

Mohammed Hichem Mortad, “A Contribution to the Fong-Tsui Conjecture Related to Self-adjoint Operators”, arXiv:1208.4346 (2012).

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