The surfatron offers the possibility of particle acceleration to arbitrarily high energies, given a sufficiently large system. Surfatron acceleration of electrons by waves excited by ions reflected from supernova remnant (SNR) shocks is investigated using particle simulations. It is shown that surfatron and stochastic acceleration could provide a seed population for the acceleration of cosmic r...

The adaptive process can be considered as being driven by two fundamental forces: exploitation and exploration. While the explorative process may be deterministic, the resultant effect may be stochastic. Stochastic effects may also exist in the expoitative process. This thesis considers the effects of stochastic fluctuations inherent in the adaptive process on the behavioural dynamics of a popu...

We use detailed information from U.S. consumers’credit card purchases to provide the first largescale description of the geography of consumption. We find that consumers’mobility is quite limited and document significant heterogeneity in the importance of gravity across sectors. Gravity is stronger in more frequently purchased sectors. Consumers actively manage the spatial dimension of their co...

This paper investigated the stochastic analysis of twodissimilar unit cold standby system considering repair, inspection, post repair under Poisson shocks. The serverman, is called when the operative unit fails. The shocks can attack the operative unit. The repaired unit is sent for inspection to decide whether the repair is satisfactory. If the repair is found unsatisfactory, then the unit is ...

We study the limiting behaviour of the prominent V/S and R/S test statistics, aimed at detecting long–range dependence, under the presence of a stochastic trend, which is given by cumulative random shocks. Depending on the size of these shocks, the asymptotic distribution is characterized either solely by the stochastic trend, or solely by the error sequence, or it is a mixture of both random c...

1 This paper aims to bridge the gap between processes where shocks are permanent and those with transitory shocks by formulating a process in which the long run impact of each innovation is time varying and stochastic. Frequent transitory shocks are supplemented by occasional permanent shifts. The stochastic permanent breaks (STOPBREAK) process is based on the premise that a shock is more likel...