A first-passage time problem for many random walkers

The passage of ions through membrane channels plays an important role in many fields of biology. An earlier paper [M. Boguñá, A.M. Berezhkovskii, G.H. Weiss, Phys. Rev. E 62 (2000) 3250] developed a toy model for statistical properties of the occupancy of a single site by different numbers of lattice random walkers chosen from an infinite set. It was assumed there that the residence time in one sojourn at the origin differed from the residence time of points elsewhere. In this paper we derive some properties of the corresponding first-passage time to the occupancy of the special site by k(>1) random walkers in one or two dimensions. Results of our study were obtained from an extensive set of simulations.