📝 SummarXiv

Abstract

Simple conditions have been developed in [Zhang, Wahl and Yu, SIAM Rev. 2014; Yu and Wang, Math. Biosci. Eng. 2019], which are used to identify the existence of slow-fast relaxation oscillations that appear in differential systems, where the geometric singular perturbation theory is not applicable. In this study, we present seven models which fail to satisfy these conditions, yet still show recurrence phenomena, which motivate us to generalize these conditions to establish new simple hypothetical conditions for identifying slow-fast relaxation oscillations and providing arguments towards the development of a mathematical theory.