  We give a $L^2\times L^2 \rightarrow L^2$ convolution estimate for singular
measures supported on transversal hypersurfaces in $\mathbb{R}^n$, which
improves earlier results of Bejenaru, Herr & Tataru as well as Bejenaru & Herr.
The arising quantities are relevant in the study of the validity of bilinear
estimates for dispersive partial differential equations. We also prove a class
of global, nonlinear Brascamp-Lieb inequalities with explicit constants in the
same spirit.
