Local smoothing for the backscattering transform

An analysis of the backscattering data for the Schr\"odinger operator in odd dimensions $n\ge 3$ motivates the introduction of the backscattering transform $B: C_0^\infty ({\mathbb R}^n;{\mathbb C})\to C^\infty ({\mathbb R}^n; {\mathbb C})$. This is an entire analytic mapping and we write $Bv = \sum_1^\infty B_Nv$ where $B_Nv$ is the $N$:th order term in the power series expansion at $v=0$. In this paper we study estimates for $B_Nv$ in $H_{(s)}$ spaces, and prove that $Bv$ is entire analytic in $v \in H_{(s)}\cap \Cal E'$ when $s\ge (n-3)/2$.