An existence theorem for elliptic equations with nonlocal boundary conditions

This research was completed during an enriching visit to Professor Chun Liu at the Illinois Institute of Technology (IIT) in the Fall of 2023. The author is deeply grateful to Professor Liu and IIT for providing a conducive and supportive environment that significantly facilitated this work. Sincere gratitude is also extended to the referee for providing valuable feedback that substantially improved the final manuscript. Partial support for this research was provided by the Taiwan Ministry of Science and Technology under grant number 112-2115-M-007-008-MY2.