ALMOST SURE EXPONENTIAL STABILITY OF NEUTRAL STOCHASTIC DIFFERENTIAL-DIFFERENCE EQUATIONS

A neutral stochastic differential difference equation d[x(t) - G(x(t - tau))] = f(t, x(t), x(t - tau)) dt + sigma(t, x(t), x(t - tau)) dw(t) was introduced by V. B. Kolmanovskii and Y. R. Nosov (''Stability and Periodic Modes of Control Systems with Aftereffect,'' Nauka, Moscow, 1981) several years ago. However, so far little is known about the alm ost sure exponential stability for such equations and the aim of this paper is to close this gap. The convergence of nonnegative special sem imartingales established by R. Sh. Lipster and A. N. Shiryayev (''Theo ry of Martingales,'' Kluwer Academic, Dordrecht, 1989) and the Ito for mula will play a key role in this paper. (C) 1997 Academic Press.