DOI: 10.68381/jca22042 ISSN: 0944-6532

A Robust Version of Convex Integral Functionals

Keita Owari

We study the pointwise supremum of convex integral functionals

\mathcal{I}_{f,\gamma}(\xi)= \sup_{Q} \left( \int_\Omega f(\omega,\xi(\omega))Q(d\omega)-\gamma(Q)\right) I f , γ ( ξ ) = sup ⁡ Q ( ∫ Ω f ( ω , ξ ( ω ) ) Q ( d ω ) − γ ( Q ) )
on
L^\infty(\Omega,\mathcal{F},\mathbb{P}) L ∞ ( Ω , F , P )
where
f:\Omega \times\mathbb{R}\rightarrow\overline{\mathbb{R}} f : Ω × R → R ‾
is a proper normal convex integrand,
\gamma γ
is a proper convex function on the set of probability measures absolutely continuous w.r.t.
\mathbb{P} P
, and the supremum is taken over all such measures. We give a pair of upper and lower bounds for the conjugate of
\mathcal{I}_{f,\gamma} I f , γ
as direct sums of a common regular part and respective singular parts; they coincide when
\mathrm{dom}(\gamma)=\{\mathbb{P}\} d o m ( γ ) = { P }
as Rockafellar's classical result, while both inequalities can generally be strict. We then investigate when the conjugate eliminates the singular measures, which a fortiori yields the equality in bounds, and its relation to other finer regularity properties of the original functional and of the conjugate.