On the functor of comonotonically maxitive functionals
Taras Radul
TL;DR
The paper defines a functor $S$ of comonotonically maxitive functionals and proves its isomorphism with the capacity functor $M$ via the max-plus fuzzy integral, providing an idempotent analogue of the Riesz representation. It proves a representation theorem: a normalized, monotone, comonotonically maximative, and plus-homogeneous functional $I:C(X)\to\mathbb{R}$ corresponds uniquely to a capacity $c\in MX$ by $I(\varphi)=\int_X^{\vee+} \varphi dc$, with $c$ constructed to ensure upper semicontinuity. This yields a homeomorphism $l_X: MX\to SX$, establishing $M\cong S$ as functors and situating $I$ as a subfunctor of $O$. The work situates these constructions in the category-theoretic monad framework on compacta, relating $O$, $I$, and $\Pi$ and outlining conditions under which $S$ can be extended to a submonad of $O$. Overall, it generalizes the Riesz-type correspondence to capacities via the max-plus integral and clarifies the categorical structure of these non-additive measures.
Abstract
We introduce a functor of functionals which preserve maximum of comonotone functions and addition of constants. This functor is a subfunctor of the functor of order-preserving functionals and contains the idempotent measure functor as subfunctor. The main aim of this paper is to show that this functor is isomorphic to the capacity functor. We establish such isomorphism using the fuzzy max-plus integral. In fact, we can consider this result as an idempotent analogue of Riesz Theorem about a correspondence between the set of $σ$-additive regular Borel measures and the set of linear positively defined functionals.
