Special values of adjoint L-functions and congruences for automorphic   forms on GL(n) over a number field
  We prove an integrality result for the value at s=1 of the adjoint L-function associated to a cohomological cuspidal automorphic representation on GL(n) over any number field. We then show that primes (outside an exceptional set) dividing this special value give rise to congruences between automorphic forms. We also prove a non-vanishing property at infinity for the relevant Rankin-Selberg L-functions on GL(n) x GL(n). 
Baskar Balasubramanyam, A. Raghuram
math.NT