Wiener-Hopf factorization and distribution of extrema for a family of L\'{e}vy processes

TL;DR

This paper introduces a new family of Lévy processes with meromorphic characteristic exponents, providing semi-explicit formulas for Wiener-Hopf factors and the distribution of the supremum, along with efficient numerical methods.

Contribution

It develops a ten-parameter family of Lévy processes with explicit Wiener-Hopf factorization and supremum distribution, including analytical and numerical techniques for their computation.

Findings

Wiener-Hopf factors expressed as infinite products over roots

Supremum density computed via exponentially converging series

Roots are proven to be real and simple, enabling efficient evaluation

Abstract

In this paper we introduce a ten-parameter family of L\'{e}vy processes for which we obtain Wiener-Hopf factors and distribution of the supremum process in semi-explicit form. This family allows an arbitrary behavior of small jumps and includes processes similar to the generalized tempered stable, KoBoL and CGMY processes. Analytically it is characterized by the property that the characteristic exponent is a meromorphic function, expressed in terms of beta and digamma functions. We prove that the Wiener-Hopf factors can be expressed as infinite products over roots of a certain transcendental equation, and the density of the supremum process can be computed as an exponentially converging infinite series. In several special cases when the roots can be found analytically, we are able to identify the Wiener-Hopf factors and distribution of the supremum in closed form. In the general case we prove that all the roots are real and simple, and we provide localization results and asymptotic formulas which allow an efficient numerical evaluation. We also derive a convergence acceleration algorithm for infinite products and a simple and efficient procedure to compute the Wiener-Hopf factors for complex values of parameters. As a numerical example we discuss computation of the density of the supremum process.