Abstract:
We obtain upper functions that serve as almost sure asymptotic upper bounds for a displacement
process given by an integrated time-varying Ornstein–Uhlenbeck process.
The form of upper functions depends on the characteristics (the
stability rate and the diffusion coefficient) of a stochastic linear differential equation.
We introduce the notion of anomalous diffusion related to behavior of upper functions and compare the
results of diffusion classification (normal diffusion, subdiffusion, and superdiffusion)
with those obtained on the basis of mean square displacements.
Keywords:time-varying Ornstein–Uhlenbeck process, upper function, anomalous diffusion, the law of the iterated logarithm.