This paper (alongside its companion, Part II BSDEYoung-II) investigates backward stochastic differential equations (BSDEs) involving a nonlinear Young integral of the form ₓ^Tg (Yₑ) η (dr, Xₑ), where the driver η (t, x) is a space-time Hölder continuous function and X is a diffusion process. Solutions to such equations provide a probabilistic interpretation of the solutions to stochastic partial differential equations (SPDEs) driven by space-time noise. Assuming the driver η (t, x) is bounded, we establish the existence and uniqueness of the solutions to these BSDEs via a modified Picard iteration method. We then derive a comparison principle by analyzing the associated linear BSDEs and establish regularity properties of the solutions. As an application, we obtain Feynman-Kac formulae for a class of linear stochastic heat equations subject to Neumann boundary conditions.
Song et al. (Fri,) studied this question.