Abstract.Let π be an automorphic irreducible cuspidal representation of GL m over a Galois (not necessarily cyclic) extension E of Q of degree . Assume that π is invariant under the action of the Galois group Gal E/Q . We computed the n-level correlation of normalized nontrivial zeros of L(s, π) and proved that it is equal to the n-level correlation of normalized nontrivial zeros of a product of distinct L-functions L(s, π 1 ) · · · L(s, π ) attached to cuspidal representations π 1 , . . . , π of GL m over Q. This is done unconditionally for m = 1, 2 and for m = 3, 4 with the degree having no prime factor ≤ (m 2 + 1)/2. In other cases, the computation is under a conjecture of bounds toward the Ramanujan conjecture over E, and a conjecture on convergence of certain series over prime powers (Hypothesis H over E and Q). The results provide an evidence that π should be (noncyclic) base change of distinct cuspidal representations π 1 , . . . , π of GL m (Q A ), if it is invariant under the Galois action. A technique used in this article is a version of Selberg orthogonality for automorphic L-functions (Lemma 6.2 and Theorem 6.4), which is proved unconditionally, without assuming π and π 1 , . . . , π being self-contragredient.
Introduction.According to Langlands' functoriality conjecture, the L-function attached to an automorphic irreducible cuspidal representation π of GL m over a number field E should equal a product of L(s, π j ) for certain cuspidal representations π j of GL m j over Q. Arthur and Clozel [ArtClo] proved that this is indeed the case when E is a cyclic Galois extension of Q and π is stable under Gal E/Q . In fact in this case, π is the base change of exactly nonequivalent cuspidal representations π Q , π Q ⊗ η E/Q , . . . , π Q ⊗ η