Comments on “Finite-time and fixed-time stabilization: Implicit Lyapunov function approach”

This paper explains a technical problem in the main theorem of the well-known paper “Finite-time and fixed-time stabilization: implicit Lyapunov function approach” by Polyakov et al. (2015), which makes impossible to fulfill one of its conditions for the class of disturbances therein specified, thus rendering void its supposed applicability and advantages over ordinary sliding mode methodologies.