Zeroes of Rankin-Selberg L-functions and the trace formula

We express the contribution of certain maximal parabolic Eisenstein series to the spectral side of the Arthur--Selberg trace formula for GL (n) in terms of zeroes of Rankin--Selberg L-functions, generalizing previous results for GL (2) and Hecke L-functions. As applications, we prove a lower bound for the sum of these zeroes, and a base change relation between the zeroes in the case n=2 for cyclic extensions of prime degree.