Seminarium Fizyki Materii Skondensowanej

Stochastic search processes are often used to find a target with unknown position. They can be observed in many natural phenomena and at any scale, for instance, in the search of animals in quest of a prey. They also occur when a protein proceeds to bind to a specific site of a DNA molecule, a problem of high importance in molecular biology. Thus, relying on chance can be an efficient way of searching for a target. We shall see that, still more surprisingly, the time necessary for finding the target can be minimized by alternating periods of effective search with "non reactive" phases, during which the searcher can not find the target, but just moves through the search region. We shall study simple models which show how and in what conditions these time-consuming, unproductive phases can decrease the search time very significantly.