Reverse trace inequality for powers greater than one

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Let A,B≥0A,B\geq 0. Let ff be a nonnegative and nondecreasing function on an interval J\mathcal{J} such that spec⁡(A)⊆J\operatorname{spec}(A)\subseteq\mathcal{J}. Reverse trace inequality. One has

Tr⁡[f(A)AsBs]≥Tr⁡[f(A)(A1/2BA1/2)s],∀ s≥1.\operatorname{Tr}\left[ f(A) A^s B^s \right] \geq \operatorname{Tr}\left[ f(A) \left(A^{1/2} B A^{1/2} \right)^s \right], \quad \forall\,s\geq 1.

This conjectures the reverse of the proved trace inequality for s∈[0,1]s\in[0,1]. The authors note that operator convexity of x↦xsx\mapsto x^s may establish it for s∈[1,2]s\in[1,2] under a suitable relaxation of an auxiliary theorem's hypotheses; the full range s≥1s\geq 1 remains open.

References

Primary source

Po-Chieh Liu and Hao-Chung Cheng, “On Araki-Type Trace Inequalities”, arXiv:2507.05242 (2025).

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