Audenaert–Datta conjecture on the full joint convexity range

Let MN\mathcal M_N denote the set of complex N×NN\times N matrices and PN\mathcal P_N the subset of positive definite matrices. For p,qRp,q\in\mathbb R, s>0s>0, and KMNK\in\mathcal M_N, define

PN×PN(A,B)Tr(Bq/2KApKBq/2)s.\mathcal P_N\times\mathcal P_N\ni(A,B)\mapsto\operatorname{Tr}\left(B^{q/2}K^*A^pKB^{q/2}\right)^s.

Audenaert–Datta conjecture. If 1p21\leq p\leq2, 1q<0-1\leq q<0, and s1/(p+q)s\geq1/(p+q), then this map is jointly convex. These conditions complement the necessary conditions stated in the source and conjecturally give the sufficient range for joint convexity.

Sources & referencesView supporting material

Primary source

Eric A. Carlen, Rupert L. Frank and Elliott H. Lieb, “Inequalities for quantum divergences and the Audenaert-Datta conjecture”, arXiv:1806.03985 (2018).

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