The space-fractional Poisson process

In this paper, we introduce the space-fractional Poisson process whose state probabilities p(k)(alpha)(t), t >= 0, alpha is an element of (0, 1]. are governed by the equations (d/dt)p(k)(alpha)(t) = -lambda(alpha)(1 - B)(alpha)p(k)(alpha)(t), where (1 - B)(alpha) is the fractional difference operator found in the time series analysis. We explicitly obtain the distributions p(k)(alpha)(t), the probability generating functions G(alpha)(u, t), which are also expressed as distributions of the minimum of i.i.d. uniform random variables. The comparison with the time-fractional Poisson process is investigated and finally, we arrive at the more general space-time-fractional Poisson process of which we give the explicit distribution. (C) 2011 Elsevier B.V. All rights reserved.