L\'evy processes and Fourier multipliers
  We study Fourier multipliers which result from modulating jumps of L\'evy processes. Using the theory of martingale transforms we prove that these operators are bounded in $L^p(\Rd)$ for $1<p<\infty$ and we obtain the same explicit bound for their norm as the one known for the second order Riesz transforms. 
Rodrigo Ba\~nuelos, Krzysztof Bogdan