On time‐fractional partial differential equations of time‐dependent piecewise constant order.

This contribution considers the time‐fractional subdiffusion with a time‐dependent variable‐order fractional operator of order β(t)$$ \beta (t) $$. It is assumed that β(t)$$ \beta (t) $$ is a piecewise constant function with a finite number of jumps. A proof technique based on the Fourier method and results from constant‐order fractional subdiffusion equations has been designed. This novel approach results in the well‐posedness of the problem. [ABSTRACT FROM AUTHOR]