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On the number of zeros of diagonal quartic forms over finite fields

  • Junyong Zhao , Yulu Feng , Shaofang Hong EMAIL logo und Chaoxi Zhu
VerĂśffentlicht/Copyright: 28. Januar 2022

Abstract

Let 𝔽q be the finite field of q=pm≡1(mod4) elements with p being an odd prime and m being a positive integer. For c,y∈𝔽q with y∈𝔽q* non-quartic, let Nn⁢(c) and Mn⁢(y) be the numbers of zeros of x14+⋯+xn4=c and x14+⋯+xn-14+y⁢xn4=0, respectively. In 1979, Myerson used Gauss sums and exponential sums to show that the generating function ∑n=1∞Nn⁢(0)⁢xn is a rational function in x and presented its explicit expression. In this paper, we make use of the cyclotomic theory and exponential sums to show that the generating functions

∑n=1∞Nn⁢(c)⁢xn and ∑n=1∞Mn+1⁢(y)⁢xn

are rational functions in x. We also obtain the explicit expressions of these generating functions. Our result extends Myerson’s theorem gotten in 1979.

MSC 2010: 11T06; 11T22

Communicated by Freydoon Shahidi


Award Identifier / Grant number: 12171332

Funding statement: S. F. Hong was supported partially by National Science Foundation of China Grant no. 12171332.

Acknowledgements

The authors would like to thank Professor Freydoon Shahidi and the anonymous referee for their careful reading of the manuscript and helpful suggestions that improve the presentation of the paper.

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Received: 2021-07-29
Revised: 2021-11-04
Published Online: 2022-01-28
Published in Print: 2022-03-01

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