One-dimensional Feynman--Kac regularity under the Engelbert--Schmidt conditions
Abstract
Let X be a time-homogeneous one-dimensional diffusion whose coefficients satisfy the Engelbert--Schmidt conditions, and let q be a bounded potential. We show that the associated Feynman--Kac semigroup is smooth in time and C1 in space, with a locally absolutely continuous first spatial derivative; the Kolmogorov equation holds almost everywhere. If the drift, second-order coefficient, and potential are continuous, the Feynman--Kac value is C1,2 in the interior. Thus, in the time-homogeneous one-dimensional setting, continuity suffices for interior C1,2 regularity. We identify the corresponding semigroups with the killed and reflected Feynman--Kac functionals, treat nonzero, time-independent Dirichlet data, and give examples showing the sharpness of the continuity assumptions and the failure of the corresponding statement in two dimensions.
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BibTeX
@misc{ruf2026onedimensional,
title = {{One-dimensional Feynman--Kac regularity under the Engelbert--Schmidt conditions}},
author = {Johannes Ruf},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.29854},
eprint = {2608.29854},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.29854},
}
RIS
TY - UNPB
TI - One-dimensional Feynman--Kac regularity under the Engelbert--Schmidt conditions
AU - Johannes Ruf
PY - 2026
DA - 2026/08/30
PB - arXiv
DO - 10.48550/arxiv.2608.29854
UR - https://arxiv.org/abs/2608.29854
AB - Let X be a time-homogeneous one-dimensional diffusion whose coefficients satisfy the Engelbert--Schmidt conditions, and let q be a bounded potential. We show that the associated Feynman--Kac semigroup is smooth in time and C^1 in space, with a locally absolutely continuous first spatial derivative; the Kolmogorov equation holds almost everywhere. If the drift, second-order coefficient, and potential are continuous, the Feynman--Kac value is C^1,2 in the interior. Thus, in the time-homogeneous one-dimensional setting, continuity suffices for interior C^1,2 regularity. We identify the corresponding semigroups with the killed and reflected Feynman--Kac functionals, treat nonzero, time-independent Dirichlet data, and give examples showing the sharpness of the continuity assumptions and the failure of the corresponding statement in two dimensions.
ER -