Noise And Delay Enhanced Stability In Tumor-Immune Responses To Chemotherapy System

The stability of tumor-immune responses to chemotherapy system with Gaussian colored noises and time delay is discussed by means of the maximum Lyapunov exponent. The unified colored noise approximation of multidimensional stochastic dynamic system with Gaussian colored and white noises is extended to the general case for the Gaussian colored noises having different self-correlation times and the correlated noises. We derive the analytic formula of the maximum Lyapunov exponent of system as a function of intensities and correlation times of Gaussian colored noises as well as delay, these parameters could change the stability of system between asymptotically stable and unstable, among, the system appears the noise and delay enhanced stability, which is detected by the maximum Lyapunov exponent. (C) 2021 Elsevier Ltd. All rights reserved.