We study the probability, PS(t), of a cluster to remain intact in
one-dimensional cluster-cluster aggregation when the cluster diffusion
coefficient scales with size as D(s)∼sγ. PS(t) exhibits a
stretched exponential decay for γ<0 and the power-laws t−3/2 for
γ=0, and t−2/(2−γ) for 0<γ<2. A random walk picture
explains the discontinuous and non-monotonic behavior of the exponent. The
decay of PS(t) determines the polydispersity exponent, τ, which
describes the size distribution for small clusters. Surprisingly,
τ(γ) is a constant τ=0 for 0<γ<2.Comment: submitted to Europhysics Letter