Published online by Cambridge University Press: 30 October 2000
Consider the following infinite dimensional stochastic evolution equation over some Hilbert space H with norm [mid ]·[mid ]:
formula here
It is proved that under certain mild assumptions, the strong solution Xt(x0)∈V[rarrhk ]H[rarrhk ]V*, t [ges ] 0, is mean square exponentially stable if and only if there exists a Lyapunov functional Λ(·, ·)[ratio ]H×R+→R1 which satisfies the following conditions:
formula here
formula here
where [Lscr ] is the infinitesimal generator of the Markov process Xt and ci, ki, μi, i = 1, 2, 3, are positive constants. As a by-product, the characterization of exponential ultimate boundedness of the strong solution is established as the null decay rates (that is, μi = 0) are considered.