Ando-type unitarily invariant norm inequalities for operator functions

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Let AA and BB be positive matrices, let ff be a function on [0,∞)[0,\infty) with f(0)=0f(0)=0, and let ∣∣∣⋅∣∣∣|||\cdot||| be an arbitrary unitarily invariant norm. Ando-type conjecture. If ff is operator monotone, then

∣∣∣(A−B)(f(A)−f(B))∣∣∣≤∣∣∣∣A−B∣f(∣A−B∣)∣∣∣.||| (A-B)(f(A)-f(B))||| \le ||||A-B|f(|A-B|)|||.

If ff is operator convex, the inequality is reversed. This would extend the Ando inequality from the operator norm setting to arbitrary unitarily invariant norms for operator monotone and operator convex functions.

References

Primary source

Trung Hoa Dinh, Minh Toan Ho, Cong Trinh Le and Bich Khue Vo, “Two trace inequalities for operator functions”, arXiv:1904.01961 (2019).

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