Abstract
In 1981, Zagier conjectured that the constant term of the automorphic form \( y^{12}|\Delta (z)|^2\), that is, \( a_0(y):=y^{12} \sum _{n=1}^{\infty } \tau ^2(n) \exp ({-4 \pi ny}), \) where \(\tau (n)\) is the nth Fourier coefficient of the Ramanujan cusp form \(\Delta (z)\), has an asymptotic expansion when \(y \rightarrow 0^{+}\) and it can be expressed in terms of the non-trivial zeros of the Riemann zeta function \(\zeta (s)\). This conjecture was settled by Hafner and Stopple, and later Chakraborty, Kanemitsu, and the second author have extended this result for any Hecke eigenform over the full modular group. In this paper, we investigate a Lambert series associated to the Fourier coefficients of a cusp form and the Möbius function \(\mu (n)\). We present an exact formula for the Lambert series and interestingly the main term is in terms of the non-trivial zeros of \(\zeta (s)\), and the error term is expressed as an infinite series involving the generalized hypergeometric series \({}_2F_1(a,b;c;z)\). As an application of this exact form, we also establish an asymptotic expansion of the Lambert series.
Similar content being viewed by others
References
Banerjee, S., Chakraborty, K.: Asymptotic behaviour of a Lambert series á la Zagier: Maass case. Ramanujan J. 48, 567–575 (2019)
Berndt, B.C.: Ramanujan’s Notebooks. Part V. Springer, New York (1998)
Bhaskaran, R.: On the Versatility of Ramanujan’s Ideas, Ramanujan Visiting Lectures, Technical Report 4. Madurai Kamraj University, pp. 118–129 (1997)
Bochner, S.: Some properties of modular relations. Ann. Math. 2(53), 332–363 (1951)
Bui, H.M., Heath-Brown, D.R.: On simple zeros of the Riemann zeta-function. Bull. Lond. Math. Soc. 45, 953–961 (2013)
Chakraborty, K., Kanemitsu, S., Maji, B.: Modular-type relations associated to the Rankin–Selberg \(L\)-function. Ramanujan J. 42, 285–299 (2017)
Chakraborty, K., Juyal, A., Kumar, S.D., Maji, B.: An asymptotic expansion of a Lambert series associated to cusp forms. Int. J. Number Theory 14, 289–299 (2018)
Chandrasekharan, K., Narasimhan, R.: Hecke’s functional equation and arithmetical identities. Ann. Math. 74, 1–23 (1961)
Conrey, J.B., Ghosh, A., Gonek, S.M.: Simple zeros of the Riemann zeta-function. Proc. Lond. Math. Soc. 76, 497–522 (1998)
Dixit, A.: Character analogues of Ramanujan-type integrals involving the Riemann \(\Xi \)-function. Pac. J. Math. 255, 317–348 (2012)
Dixit, A.: Analogues of the general theta transformation formula. Proc. Roy. Soc. Edinb. Sect. A 143, 371–399 (2013)
Dixit, A., Roy, A., Zaharescu, A.: Ramanujan–Hardy–Littlewood–Riesz phenomena for Hecke forms. J. Math. Anal. Appl. 426, 594–611 (2015)
Fujii, A.: On the distribution of the values of the derivative of the Riemann zeta function at its zeros (I). Proc. Steklov Inst. Math. 276, 51–76 (2012)
Gonek, S.M.: Mean values of the Riemann zeta function and its derivatives. Invent. Math. 75, 123–141 (1984)
Hafner, J., Stopple, J.: A heat kernel associated to Ramanujan’s tau function. Ramanujan J. 4, 123–128 (2000)
Hardy, G.H., Littlewood, J.E.: Contributions to the theory of the Riemann zeta-function and the theory of the distribution of primes. Acta Math. 41, 119–196 (1916)
Hejhal, D.A.: On the distribution of \( | \log \zeta ^{\prime } (1/2 + it)|\), in number theory, trace formulas, and discrete groups. In: Aubert, K.E., Bombieri, E., Goldfeld, D.M. (eds.) Proc. 1987 Selberg Symposium. Academic Press, pp. 343–370 (1989)
Hiary, G.A., Odlyzko, A.M.: Numerical study of the derivative of the Riemann zeta function at zeros. Commentarii Mathematici Universitatis Sancti Pauli 60, 47–60 (2011)
Iwaniec, H., Kowalski, E.: Analytic Number Theory. American Mathematical Society Colloquium Publications, Providence (2004)
Olver, F.W.J., Lozier, D.W., Boisvert, R.F., Clark, C.W. (eds.): NIST Handbook of Mathematical Functions. Cambridge University Press, Cambridge (2010)
Paris, R.B., Kaminski, D.: Asymptotics and Mellin-Barnes Integrals, Encyclopedia of Mathematics and Its Applications, vol. 85. Cambridge University Press, Cambridge (2001)
Rankin, R.A.: Contributions to the theory of Ramanujan’s function \(\tau (n)\) and similar arithmetical functions, I, II. Proc. Camb. Philos. Soc. 35, 351–372 (1939)
Roy, A., Zaharescu, A., Zaki, M.: Some identities involving convolutions of Dirichlet characters and the Möbius function. Proc. Indian Acad. Sci. Math. Sci. 126, 21–33 (2016)
Selberg, A.: Bemerkungen über eine Dirichletsche Reihe, die mit der Theorie der Modulformen nahe verbunden ist. Arch. Math. Naturvid. 43, 47–50 (1940)
Shimura, G.: On the holomorphy of certain Dirichlet series. Proc. Lond. Math. Soc. Ser. 31, 79–98 (1975)
Titchmarsh, E.C.: The Theory of the Riemann Zeta-Function. Clarendon Press, Oxford (1986)
Zagier, D.: The Rankin–Selberg method for automorphic functions which are not of rapid decay. J. Fac. Sci. Univ. Tokyo IA Math. 28, 415–437 (1981)
Zagier, D.: Introduction to Modular Forms, From Number Theory to Physics (Les Houches, 1989), pp. 238–291. Springer, New York (1989)
Acknowledgements
The authors sincerely thank Prof. Steven Gonek for giving information about the manuscripts [5, 9] and for giving important suggestions. We would also like to thank Prof. Atul Dixit for going through the manuscript and giving valuable suggestions. The second author wishes to thank SERB for the Start-Up Research Grant SRG/2020/000144. The third author wants to thank Prof. B. R. Shankar for his continuous support. His research is funded by the National Institute of Technology Karnataka, India. The authors would also like to thank the referee for his valuable comments and suggestions.
Author information
Authors and Affiliations
Corresponding author
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Juyal, A., Maji, B. & Sathyanarayana, S. An exact formula for a Lambert series associated to a cusp form and the Möbius function. Ramanujan J 57, 769–784 (2022). https://doi.org/10.1007/s11139-020-00375-7
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11139-020-00375-7