The Quarterly Journal of Mathematics Advance Access published online on February 19, 2009
The Quarterly Journal of Mathematics, doi:10.1093/qmath/hap008
ON CUSP FORM COEFFICIENTS IN NONLINEAR EXPONENTIAL SUMS

Department of Mathematics, Shandong University, Jinan 250100, People's Republic of China
E-mail: qfsun{at}mail.sdu.edu.cn
Received 2 December 2008;
revised 14 January 2009
| Abstract |
|---|
Let f be either a holomorphic Hecke eigenform of weight
for SL2(
) with
|
|
) with Laplace eigenvalue
+
2. In the latter case, |
|
is the modified Bessel function of the third kind and e(z) = e2
iz. This paper studied the cancelation of the coefficients
(n) or
(n) in nonlinear exponential sums with amplitude n
, 0 < 
.