Pointwise fundamental theorem of L-fractional calculus beyond analytic functions

Determine whether the fundamental theorem of L-fractional calculus (and its Caputo counterpart) can be strengthened from holding almost everywhere to holding at every point for a class of functions larger than analytic or fractional-analytic functions.

Background

The paper proves pointwise versions of the fundamental theorem for analytic (or fractional-analytic) data, while for general absolutely continuous functions the identities hold almost everywhere. Extending pointwise validity to a broader class would clarify solution notions and rigor in fractional calculus.

References

Can the "almost everywhere" condition in the fundamental theorem of L-fractional calculus (and in Caputo fractional calculus) be weakened? (See Lemma 4.1 and Proposition 4.2.)

Theory on linear L-fractional differential equations and a new Mittag-Leffler-type function (2403.00341 - Jornet, 1 Mar 2024) in Section 8, Open Problems