Gan, Wee Teck; Ichino, Atsushi The automorphic discrete spectrum of \(\mathrm{Mp}_4\). (English) Zbl 1477.11099 Int. Math. Res. Not. 2021, No. 3, 1603-1677 (2021). In the Langlands program, one of the fundamental problem is Arthur’s conjecture on the parametrization of automorphic discrete spectrum of reductive groups in terms of A-packets. Such a parametrization has been established uniformly for quasi-split classical groups via Arthur’s (twisted) stable trace formula machine. Recently, the authors proved an analogous conjecture for the metaplectic group \(Mp_{2n}\) under certain restrictions on A-packets via the theory of theta correspondence [W. Gan and A. Ichino, Ann. Math. (2) 188, No. 3, 965–1016 (2018; Zbl 1486.11076)]. In the paper under review, in the case of \(Mp_4\), the authors provide a complete answer.The paper is well written. Reviewer: Caihua Luo (Göteborg) Cited in 1 ReviewCited in 1 Document MSC: 11F70 Representation-theoretic methods; automorphic representations over local and global fields 11F55 Other groups and their modular and automorphic forms (several variables) Keywords:metaplectic group; Arthur multiplicity formula; A-packet Citations:Zbl 1486.11076 PDFBibTeX XMLCite \textit{W. T. Gan} and \textit{A. Ichino}, Int. Math. Res. Not. 2021, No. 3, 1603--1677 (2021; Zbl 1477.11099) Full Text: DOI arXiv