${\mathcal R}$-boundedness of Riesz transforms and spectral multipliers of Schr\"odinger operators
Let $\LL = -\Delta + V$ be a Schr\"odinger operator with a non-negative potential. It is known that its associated Riesz transform $\nabla \LL^{-\sfrac{1}{2}}$ is bounded on $L^p(\RR^d)$ for $p \in (1,2]$, with a bound independent of $V$. We prove more, namely that the set \[ \{ \nabla \LL^{-\sfrac{1}{2}},\ 0 \le V \in...