Lower semicontinuity conjecture for convex integral functionals of matricial measures
Let denote the cone of positive semidefinite Hermitian matrices, let be the -dimensional torus, and let be a nonnegative matricial measure on . Write its Lebesgue decomposition as , where is the absolutely continuous part and is Lebesgue measure. Let be such that is convex in its first argument for every fixed . Lower semicontinuity conjecture. The functional
is lower semicontinuous with respect to the weak* topology. The conjecture is intended to provide a mathematical basis for the chosen divergence index and to ensure existence of a solution to the associated primal problem when the prior is arbitrary; the source discussion does not provide a proof, and its resolution remains open.
References
Primary source
Bin Zhu, Augusto Ferrante, Johan Karlsson and Mattia Zorzi, “M^2-Spectral Estimation: A Flexible Approach Ensuring Rational Solutions”, arXiv:2004.14778 (2021).
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