Generalised Br\`egman relative entropies: a brief introduction
Abstract
We present some basic elements of the theory of generalised Br\`egman relative entropies over nonreflexive Banach spaces. Using nonlinear embeddings of Banach spaces together with the Euler--Legendre functions, this approach unifies two former approaches to Br\`egman relative entropy: one based on reflexive Banach spaces, another based on differential geometry. This construction allows to extend Br\`egman relative entropies, and related geometric and operator structures, to arbitrary-dimensional state spaces of probability, quantum, and postquantum theory. We give several examples, not considered previously in the literature.
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