There exists a positive function $\psi(t)${on}$t\geq0${, with fast decay at
infinity, such that for every measurable set}$\Omega${in the Euclidean space
and}$R>0${, there exist entire functions}$A(x) ${and}$B(x) ${of exponential
type}$R${, satisfying\}$A(x)\leq \chi_{\Omega}(x)\leq B(x)${and}$| B(x)-A(x)|
\leqslant\psi(R\operatorname*{dist}(x,\partial\Omega)) $. This leads to
Erd\H{o}s Tur\'{a}n estimates for discrepancy of point set distributions in the
multi dimensional torus.
This paper contains an $L^{p}$ improving result for convolution operators
defined by singular measures associated to hypersurfaces on the motion group.
This needs only mild geometric properties of the surfaces, and it extends
earlier results on Radon type transforms on $\mathbb{R}^{n}$. The proof relies
on the harmonic analysis on the motion group.