Estimating the division rate and kernel in the fragmentation equation

Abstract

We consider the fragmentation equation∂f∂t(t,x)=−B(x)f(t,x)+∫y=xy=∞k(y,x)B(y)f(t,y)dy, and address the question of estimating the fragmentation parameters – i.e. the division rate B(x) and the fragmentation kernel k(y,x) – from measurements of the size distribution f(t,⋅) at various times. This is a natural question for any application where the sizes of the particles are measured experimentally whereas the fragmentation rates are unknown, see for instance Xue and Radford (2013) [26] for amyloid fibril breakage. Under the assumption of a polynomial division rate B(x)=αxγ and a self-similar fragmentation kernel k(y,x)=1yk0(xy), we use the asymptotic behavior proved in Escobedo et al. (2004) [11] to obtain uniqueness of the triplet (α,γ,k0) and a representation formula for k0. To invert this formula, one of the delicate points is to prove that the Mellin transform of the asymptotic profile never vanishes, what we do through the use of the Cauchy integral.