Free subexponentiality and regular variation

Rajat Subhra Hazra

Abstract

We study the tail behavior of the law of the sum of free identically distributed random variables affiliated to some W*-probability space with its law having regularly varying tail. We introduce the notion of free subexponentiality by extending the concept from the classical setup and show that the laws with regularly varying tail are subexponential. The analysis is based on the relation between the remainder terms in Taylor series expansions of Cauchy and Voiculescu transforms, when the law admits moments. We study the tail behavior of the law of the sum of free identically distributed random till certain finite order. We use this analysis to extend Embrechts-Goldie-Veraverbeke theorem regarding the tail equivalence of a free infinitely divisible law and its LC)vy measure in the regular variation setup.