On Arthur's packets of real classical groups

This article is part of a project started in [AMR18] which consists in investigating Arthur packets for real classical groups. Our goal is to give an explicit description of these packets and to establish the multiplicity one property (which is known to hold for p-adic and complex groups). The main result in this paper is a construction of packets from unipotent packets on c-Levi factors using cohomological induction. An important tool used in the argument is a result on commutativity between cohomological induction and spectral endoscopic transfer.