# Von Mangoldt function

In mathematics, the **von Mangoldt function** is an arithmetic function named after German mathematician Hans von Mangoldt. It is an example of an important arithmetic function that is neither multiplicative nor additive.

## Contents

## DefinitionEdit

The von Mangoldt function, denoted by Λ(*n*), is defined as

The values of Λ(*n*) for the first nine positive integers (i.e. natural numbers) are

which is related to (sequence A014963 in the OEIS).

The **summatory von Mangoldt function**, *ψ*(*x*), also known as the Chebyshev function, is defined as

Von Mangoldt provided a rigorous proof of an explicit formula for *ψ*(*x*) involving a sum over the non-trivial zeros of the Riemann zeta function. This was an important part of the first proof of the prime number theorem.

## PropertiesEdit

The von Mangoldt function satisfies the identity^{[1]}^{[2]}

The sum is taken over all integers d that divide n. This is proved by the fundamental theorem of arithmetic, since the terms that are not powers of primes are equal to 0. For example, consider the case *n* = 12 = 2^{2} × 3. Then

By Möbius inversion, we have^{[2]}^{[3]}^{[4]}

## Dirichlet seriesEdit

The von Mangoldt function plays an important role in the theory of Dirichlet series, and in particular, the Riemann zeta function. For example, one has

The logarithmic derivative is then^{[5]}

These are special cases of a more general relation on Dirichlet series. If one has

for a completely multiplicative function *f* (*n*), and the series converges for Re(*s*) > σ_{0}, then

converges for Re(*s*) > σ_{0}.

## Chebyshev functionEdit

The second Chebyshev function *ψ*(*x*) is the summatory function of the von Mangoldt function:^{[6]}

The Mellin transform of the Chebyshev function can be found by applying Perron's formula:

which holds for Re(*s*) > 1.

## Exponential seriesEdit

Hardy and Littlewood examined the series^{[7]}

in the limit *y* → 0^{+}. Assuming the Riemann hypothesis, they demonstrate that

In particular this function is oscillatory with diverging oscillations: there exists a value *K* > 0 such that both inequalities

hold infinitely often in any neighbourhood of 0. The graphic to the right indicates that this behaviour is not at first numerically obvious: the oscillations are not clearly seen until the series is summed in excess of 100 million terms, and are only readily visible when *y* < 10^{−5}.

## Riesz meanEdit

The Riesz mean of the von Mangoldt function is given by

Here, λ and δ are numbers characterizing the Riesz mean. One must take *c* > 1. The sum over ρ is the sum over the zeroes of the Riemann zeta function, and

can be shown to be a convergent series for *λ* > 1.

## Approximation by Riemann zeta zerosEdit

The real part of the sum over the zeta zeros:

- , where
*ρ*(*i*) is the i-th zeta zero, peaks at primes, as can be seen in the adjoining graph, and can also be verified through numerical computation. It does not sum up to the Von Mangoldt function.^{[8]}

The Fourier transform of the von Mangoldt function gives a spectrum with spikes at ordinates equal to imaginary part of the Riemann zeta function zeros. This is sometimes called a duality.

## See alsoEdit

## ReferencesEdit

**^**Apostol (1976) p.32- ^
^{a}^{b}Tenenbaum (1995) p.30 **^**Apostol (1976) p.33**^**Schroeder, Manfred R. (1997).*Number theory in science and communication. With applications in cryptography, physics, digital information, computing, and self-similarity*. Springer Series in Information Sciences.**7**(3rd ed.). Berlin: Springer-Verlag. ISBN 3-540-62006-0. Zbl 0997.11501.**^**Hardy & Wright (2008) §17.7, Theorem 294**^**Apostol (1976) p.246**^**Hardy, G. H. & Littlewood, J. E. (1916). "Contributions to the Theory of the Riemann Zeta-Function and the Theory of the Distribution of Primes" (PDF).*Acta Mathematica*.**41**: 119–196. doi:10.1007/BF02422942. Archived from the original (PDF) on 2012-02-07. Retrieved 2014-07-03.**^**Conrey, J. Brian (March 2003). "The Riemann hypothesis" (PDF).*Notices Am. Math. Soc*.**50**(3): 341–353. Zbl 1160.11341. Page 346

- Apostol, Tom M. (1976),
*Introduction to analytic number theory*, Undergraduate Texts in Mathematics, New York-Heidelberg: Springer-Verlag, ISBN 978-0-387-90163-3, MR 0434929, Zbl 0335.10001 - Hardy, G. H.; Wright, E. M. (2008) [1938]. Heath-Brown, D. R.; Silverman, J. H. (eds.).
*An Introduction to the Theory of Numbers*(6th ed.). Oxford: Oxford University Press. ISBN 978-0-19-921985-8. MR 2445243. Zbl 1159.11001.

- Tenebaum, Gérald (1995).
*Introduction to analytic and probabilistic number theory*. Cambridge Studies in Advanced Mathematics.**46**. Translated by C.B. Thomas. Cambridge: Cambridge University Press. ISBN 0-521-41261-7. Zbl 0831.11001.

## External linksEdit

- Allan Gut,
*Some remarks on the Riemann zeta distribution*(2005) - S.A. Stepanov (2001) [1994], "Mangoldt function", in Hazewinkel, Michiel (ed.),
*Encyclopedia of Mathematics*, Springer Science+Business Media B.V. / Kluwer Academic Publishers, ISBN 978-1-55608-010-4 - Chris King,
*Primes out of thin air*(2010) - Heike,
*How plot Riemann zeta zero spectrum in Mathematica?*(2012)