Al-Rashed–Zegarliński conjecture on monotonicity of the Schatten quadratic form

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Let HH be a complex Hilbert space and let B(H)B(H) denote the linear operators on HH. For 1<p<∞1<p<\infty, define the Schatten norm by ∥T∥p=(Tr⁡∣T∣p)1/p\|T\|_p=(\operatorname{Tr}|T|^p)^{1/p}. For A,B,D∈B(H)A,B,D\in B(H), define the quadratic form

⟨A,B⟩D:=∂s∂t∣s=t=0∥D+sA+tB∥p2.\langle A,B\rangle_D:=\left.\partial_s\partial_t\right|_{s=t=0}\|D+sA+tB\|_p^2.

Al-Rashed–Zegarliński's quadratic-form conjecture. For every completely positive trace-preserving map ϕ\phi on B(H)B(H) and all A,B,D∈B(H)A,B,D\in B(H),

⟨ϕ(A),ϕ(A)⟩ϕ(D)≤⟨A,A⟩D.\langle\phi(A),\phi(A)\rangle_{\phi(D)}\leq\langle A,A\rangle_D.

The source introduces this as a special case of a conjecture concerning monotonicity of a noncommutative Luxembourg norm. The supplied text does not state whether this conjecture is proved or disproved, so its status remains open here.

References

Primary source

Haonan Zhang, “Some convexity and monotonicity results of trace functionals”, arXiv:2108.05785 (2023).

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