Regularity estimates in H\"older spaces for Schr\"odinger operators via   a T1 theorem
  We derive H\"older regularity estimates for operators associated with a time independent Schr\"odinger operator of the form $-\Delta+V$. The results are obtained by checking a certain condition on the function $T1$. Our general method applies to get regularity estimates for maximal operators and square functions of the heat and Poisson semigroups, for Laplace transform type multipliers and also for Riesz transforms and negative powers $(-\Delta+V)^{-\gamma/2}$, all of them in a unified way. 
Tao Ma, P. R. Stinga, J. L. Torrea, Chao Zhang
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