# Mertens conjecture

In mathematics, the **Mertens conjecture** is the disproven statement that the Mertens function is bounded by , which implies the Riemann hypothesis. It was conjectured by Thomas Joannes Stieltjes in an 1885 letter to Charles Hermite (reprinted in Stieltjes (1905)) and Franz Mertens (1897), and disproved by Andrew Odlyzko and Herman te Riele (1985).
It is a striking example of a mathematical proof contradicting a large amount of computational evidence in favor of a conjecture.

## Definition

In number theory, we define the Mertens function as

where μ(k) is the Möbius function; the **Mertens conjecture** is that for all *n* > 1,

## Disproof of the conjecture

Stieltjes claimed in 1885 to have proven a weaker result, namely that was bounded, but did not publish a proof.[1] (In terms of , the Mertens conjecture is that .)

In 1985, Andrew Odlyzko and Herman te Riele proved the Mertens conjecture false: indeed, and .[2][3] It was later shown that the first counterexample appears below (Pintz 1987) but above 10^{14}.[4] The upper bound has since been lowered to (Kotnik and Te Riele 2006) or approximately , but no counterexample is explicitly known. The law of the iterated logarithm states that if
μ is replaced by a random sequence of +1s and −1s then the order of growth of the partial sum of the first *n* terms is (with probability 1) about (*n* log log *n*)^{1/2}, which suggests that the order of growth of *m*(*n*) might be somewhere around (log log *n*)^{1/2}. The actual order of growth may be somewhat smaller; it was conjectured by Steve Gonek in the early 1990s that the order of growth of *m*(*n*) was , which was also conjectured by Ng (2004), based on a heuristic argument assuming the Riemann hypothesis and certain conjectures about the averaged behavior of zeros of the Riemann zeta function.[5]

In 1979, Cohen and Dress found the largest known value of for *M*(7766842813) = 50286, and, in 2011, Kuznetsov found the largest known negative value for *M*(11609864264058592345) = -1995900927.[6] In 2016, Hurst computed M(n) for every *n* ≤ 10^{16} but did not find larger values of *m*(*n*).[7]

In 2006, Kotnik and te Riele improved the upper bound and showed that there are infinitely many values of *n* for which *m*(*n*)>1.2184, but without giving any specific value for such an *n*.[8] In 2016, Hurst made further improvements by showing and .

## Connection to the Riemann hypothesis

The connection to the Riemann hypothesis is based on the Dirichlet series for the reciprocal of the Riemann zeta function,

valid in the region . We can rewrite this as a Stieltjes integral

and after integrating by parts, obtain the reciprocal of the zeta function as a Mellin transform

Using the Mellin inversion theorem we now can express *M* in terms of
1/ζ as

which is valid for 1 < σ < 2, and valid for 1/2 < σ < 2 on the Riemann hypothesis.
From this, the Mellin transform integral must be convergent, and hence
*M*(*x*) must be *O*(*x*^{e}) for every exponent *e* greater than
1/2. From this it follows that

for all positive ε is equivalent to the Riemann hypothesis, which therefore would have followed from the stronger Mertens hypothesis, and follows from the hypothesis of Stieltjes that

- .

## References

- Borwein, Peter; Choi, Stephen; Rooney, Brendan; et al., eds. (2007).
*The Riemann hypothesis. A resource for the aficionado and virtuoso alike*. CMS Books in Mathematics. New York, NY: Springer-Verlag. p. 69. ISBN 978-0-387-72125-5. Zbl 1132.11047. - Odlyzko & te Riele (1985)
- Sandor et al (2006) pp.188–189
- Kotnik, Tadej; van de Lune, Jan (November 2003). "Further systematic computations on the summatory function of the Möbius function".
*MAS-R0313*. - "The distribution of the summatory function of the Möbius function" (PDF).
- Kuznetsov, Eugene (2011). "Computing the Mertens function on a GPU". arXiv:1108.0135 [math.NT].
- Hurst, Greg (2016). "Computations of the Mertens Function and Improved Bounds on the Mertens Conjecture". arXiv:1610.08551 [math.NT].
- Kotnik & te Riele (2006)

## Further reading

- Kotnik, Tadej; te Riele, Herman (2006). "The Mertens Conjecture Revisited". In Hess, Florian (ed.).
*Algorithmic number theory. 7th international symposium, ANTS-VII, Berlin, Germany, July 23--28, 2006. Proceedings*. Lecture Notes in Computer Science.**4076**. Berlin: Springer-Verlag. pp. 156–167. doi:10.1007/11792086_12. ISBN 3-540-36075-1. Zbl 1143.11345. - Kotnik, T.; van de Lune, J. (2004). "On the order of the Mertens function" (PDF).
*Experimental Mathematics*.**13**: 473–481. Archived from the original (PDF) on 2007-04-03. - Mertens, F. (1897). "Über eine zahlentheoretische Funktion".
*Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften, Mathematisch-Naturwissenschaftliche Klasse, Abteilung 2a*.**106**: 761–830. - Odlyzko, A. M.; te Riele, H. J. J. (1985), "Disproof of the Mertens conjecture" (PDF),
*Journal für die reine und angewandte Mathematik*,**357**: 138–160, doi:10.1515/crll.1985.357.138, ISSN 0075-4102, MR 0783538, Zbl 0544.10047 - Pintz, J. (1987). "An effective disproof of the Mertens conjecture".
*Astérisque*. 147–148: 325–333. - Sándor, József; Mitrinović, Dragoslav S.; Crstici, Borislav, eds. (2006),
*Handbook of number theory I*, Dordrecht: Springer-Verlag, pp. 187–189, ISBN 1-4020-4215-9, Zbl 1151.11300 - Stieltjes, T. J. (1905), "Lettre a Hermite de 11 juillet 1885, Lettre #79", in Baillaud, B.; Bourget, H. (eds.),
*Correspondance d'Hermite et Stieltjes*, Paris: Gauthier—Villars, pp. 160–164