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On the number of prime divisors and radicals of non-zero Fourier coefficients of Hilbert cusp forms

  • Sunil L. Naik ORCID logo EMAIL logo
Published/Copyright: September 14, 2022

Abstract

In this article, we derive lower bounds for the number of distinct prime divisors of families of non-zero Fourier coefficients of non-CM primitive cusp forms and more generally of non-CM primitive Hilbert cusp forms. In particular, for the Ramanujan Δ-function, we show that, for any ϵ > 0 , there exist infinitely many natural numbers 𝑛 such that τ ( p n ) has at least

2 ( 1 - ϵ ) log n log log n

distinct prime factors for almost all primes 𝑝. This improves and refines the existing bounds. We also study lower bounds for absolute norms of radicals of non-zero Fourier coefficients of modular forms alluded to above.

MSC 2010: 11F11; 11F30; 11N56

Acknowledgements

The author would like to thank Sanoli Gun and Purusottam Rath for their support and guidance. The author would also like to thank the referee for helpful suggestions. The author would also like to acknowledge the support of DAE number theory plan project.

  1. Communicated by: Jan Bruinier

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Received: 2022-02-16
Revised: 2022-06-23
Published Online: 2022-09-14
Published in Print: 2022-11-01

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