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RESEARCH PRODUCT

Exponential sums related to Maass forms

Esa V. VesalainenJesse Jääsaari

subject

FOURIER COEFFICIENTSPure mathematicsLogarithmHolomorphic function01 natural sciencesUpper and lower boundsAPPROXIMATE FUNCTIONAL-EQUATIONFunctional equationFOS: Mathematics111 MathematicsNumber Theory (math.NT)0101 mathematicsFourier coefficients of cusp formsFourier seriesexponential sumsMathematicsAlgebra and Number TheoryMathematics - Number Theory010102 general mathematicsVoronoi summation formulaCusp formADDITIVE TWISTSExponential functionSQUAREExponential sumRIEMANN ZETA-FUNCTION

description

We estimate short exponential sums weighted by the Fourier coefficients of a Maass form. This requires working out a certain transformation formula for non-linear exponential sums, which is of independent interest. We also discuss how the results depend on the growth of the Fourier coefficients in question. As a byproduct of these considerations, we can slightly extend the range of validity of a short exponential sum estimate for holomorphic cusp forms. The short estimates allow us to reduce smoothing errors. In particular, we prove an analogue of an approximate functional equation previously proven for holomorphic cusp form coefficients. As an application of these, we remove the logarithm from the classical upper bound for long linear sums weighted by Fourier coefficients of Maass forms, the resulting estimate being the best possible. This also involves improving the upper bounds for long linear sums with rational additive twists, the gains again allowed by the estimates for the short sums. Finally, we shall use the approximate functional equation to bound somewhat longer short exponential sums.

yearjournalcountryeditionlanguage
2019-01-01
10.4064/aa8447-9-2018http://hdl.handle.net/10138/310618