Asymptotic behaviour and estimates of slowly varying convolution   semigroups
  We prove the asymptotic formulas for the transition densities of isotropic unimodal convolution semigroups of probability measures on $\mathbb{R} ^d$ under the assumption that its L\'{e}vy--Khintchine exponent varies slowly. We also derive some new estimates of the transition densities and Green functions. 
Tomasz Grzywny and Micha{\l} Ryznar and Bartosz Trojan
math.PR math.FA