A lower bound on the separation between two solutions of a scalar Riemann-Liouville fractional differential equation

In this paper, we establish a lower bound on the separation between two distinct solutions of a scalar Riemann-Liouville fractional differential equation. As a consequence, we show that the Lyapunov exponent of an arbitrary non-trivial solution of a bounded linear scalar Riemann-Liouville fractional differential equation is always non-negative.