Comptes Rendus
Number Theory
On a theorem of Friedlander and Iwaniec
Comptes Rendus. Mathématique, Volume 348 (2010) no. 17-18, pp. 947-950.

In [3], Friedlander and Iwaniec (2009) studied the so-called Hyperbolic Prime Number Theorem, which asks for an infinitude of elements γ=(abcd)SL(2,Z) such that the norm squared

γ2=a2+b2+c2+d2=p,
is a prime. Under the Elliott–Halberstam conjecture, they proved the existence of such, as well as a formula for their count, off by a constant from the conjectured asymptotic. In this Note, we study the analogous question replacing the integers with the Gaussian integers. We prove unconditionally that for every odd n3, there is a γSL(2,Z[i]) such that γ2=n. In particular, every prime is represented. The proof is an application of Siegel's mass formula.

Dans [3], Friedlander et Iwaniec (2009) ont introduit l'ensemble des nombres premiers qui admettent une représentation

γ2=a2+b2+c2+d2=p,
γ=(abcd)SL(2,Z). Ils y étudient la question de savoir si cet ensemble est infini, et le démontrent sous la conjecture de Elliott et Halberstam. Dans cette Note, nous considérons le problème analogue pour les entiers de Gauss, donc γSL(2,Z[i]), et montrons que γ2 représente alors en fait tout nombre impair. La formule de masse de Siegel joue un rôle essentiel.

Received:
Published online:
DOI: 10.1016/j.crma.2010.08.004

Jean Bourgain 1; Alex Kontorovich 1, 2

1 Department of Mathematics, Institute for Advanced Study, 1 Einstein Drive, Princeton, NJ 08540, USA
2 Department of Mathematics, Brown University, Providence, RI 02912, USA
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Jean Bourgain; Alex Kontorovich. On a theorem of Friedlander and Iwaniec. Comptes Rendus. Mathématique, Volume 348 (2010) no. 17-18, pp. 947-950. doi : 10.1016/j.crma.2010.08.004. https://comptes-rendus.academie-sciences.fr/mathematique/articles/10.1016/j.crma.2010.08.004/

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[3] John B. Friedlander; Henryk Iwaniec Hyperbolic prime number theorem, Acta Math., Volume 202 (2009) no. 1, pp. 1-19

[4] Henryk Iwaniec Almost-primes represented by quadratic polynomials, Invent. Math., Volume 47 (1978), pp. 171-188

[5] Yoshiyuki Kitaoka A note on local densities of quadratic forms, Nagoya Math. J., Volume 92 (1983), pp. 145-152

[6] Irma Reiner On the two-adic density of representations by quadratic forms, Pacific J. Math., Volume 6 (1956), pp. 753-762

[7] Carl Ludwig Siegel Über die analytische Theorie der quadratischen Formen, Ann. Math. (2), Volume 36 (1935) no. 3, pp. 527-606

[8] Tonghai Yang An explicit formula for local densities of quadratic forms, J. Number Theory, Volume 72 (1998) no. 2, pp. 309-356

[9] Tonghai Yang Local densities of 2-adic quadratic forms, J. Number Theory, Volume 108 (2004) no. 2, pp. 287-345

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