Functoriality for the exterior square of GL₄ and the symmetric fourth of GL₂

In this paper we prove the functoriality of the exterior square of cusp forms on G L 4 GL_{4} as automorphic forms on G L 6 GL_{6} and the symmetric fourth of cusp forms on G L 2 GL_{2} as automorphic forms on G L 5 GL_{5} . We prove these by applying a converse theorem of Cogdell and Piatetski-Shapiro to analytic properties of certain L L -functions obtained by the Langlands-Shahidi method. We give several applications: First, we prove the weak Ramanujan property of cuspidal representations of G L 4 GL_{4} and the absolute convergence of the exterior square L L -functions of G L 4 GL_{4} . Second, we prove that the fourth…

• NS
  National Science Foundation
• CM
  Clay Mathematics Institute
• NS
  Natural Sciences and Engineering Research Council of Canada