Riemann Zeta Function Zeros

Zeros of the
Riemann zeta function 
come in two different types. So-called "trivial zeros" occur at
all negative even integers

,

,

, ..., and "nontrivial zeros" occur at certain values of

satisfying
 |
(1)
|
for

in the "
critical strip"

. In general, a nontrivial zero of

is denoted

, and the

th nontrivial zero with

is commonly denoted

(Brent 1979; Edwards 2001, p. 43), with the corresponding value of

being called

.
Wiener (1951) showed that the
prime number theorem is literally equivalent to the assertion that

has no zeros on

(Hardy 1999, p. 34; Havil 2003, p. 195). The
Riemann hypothesis asserts that the nontrivial zeros of

all have
real part ![sigma=R[s]=1/2](https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_vB8u6E3yePvh4xXV_yugeUygtbPnyoyt8_WSHGf9U5XELU3HybmmPU1x-nr0zbY4GPOk3SwEcZPlmnG6Ma7NTF5sxJihtxCG2mjJU8V-vFKvFvRleKcyW2z-4dTDLdBr7Spd2lecsmOFLsEfkKpITsAlwS6V5Z=s0-d)
, a line called the "
critical line." This is known to be true for the first

zeros.

An attractive poster plotting zeros of the
Riemann zeta function on the
critical line together with annotations for relevant historical information, illustrated above, was created by Wolfram Research (1995).
The plots above show the real and imaginary parts of

plotted in the complex plane together with the
complex modulus of

. As can be seen, in right half-plane, the function is fairly flat, but with a large number of horizontal ridges. It is precisely along these ridges that the nontrivial zeros of

lie.

The position of the complex zeros can be seen slightly more easily by plotting the contours of zero real (red) and imaginary (blue) parts, as illustrated above. The zeros (indicated as black dots) occur where the curves intersect.

The figures above highlight the zeros in the
complex plane by plotting

(where the zeros are dips) and

(where the zeros are peaks).

The above plot shows

for

between 0 and 60. As can be seen, the first few nontrivial zeros occur at the values given in the following table (Wagon 1991, pp. 361-362 and 367-368; Havil 2003, p. 196; Odlyzko), where the corresponding negative values are also roots. The integers closest to these values are 14, 21, 25, 30, 33, 38, 41, 43, 48, 50, ... (OEIS
A002410). The numbers of nontrivial zeros less than 10,

,

, ... are 0, 29, 649, 10142, 138069, 1747146, ... (OEIS
A072080; Odlyzko).
 | Sloane |  |
1 | A058303 | 14.134725 |
2 | | 21.022040 |
3 | | 25.010858 |
4 | | 30.424876 |
5 | | 32.935062 |
6 | | 37.586178 |

The so-called
xi-function 
defined by Riemann has precisely the same zeros as the nontrivial zeros of

with the additional benefit that

is entire and

is purely real and so are simpler to locate.
ZetaGrid is a distributed computing project attempting to calculate as many zeros as possible. It had reached 1029.9 billion zeros as of Feb. 18, 2005. Gourdon (2004) used an algorithm of Odlyzko and Schönhage to calculate the first

zeros (Pegg 2004, Pegg and Weisstein 2004). The following table lists historical benchmarks in the number of computed zeros (Gourdon 2004).
year |  | author |
1903 | 15 | J. P. Gram |
1914 | 79 | R. J. Backlund |
1925 | 138 | J. I. Hutchinson |
1935 |  | E. C. Titchmarsh |
1953 |  | A. M. Turing |
1956 |  | D. H. Lehmer |
1956 |  | D. H. Lehmer |
1958 |  | N. A. Meller |
1966 |  | R. S. Lehman |
1968 |  | J. B. Rosser, J. M. Yohe, L. Schoenfeld |
1977 |  | R. P. Brent |
1979 |  | R. P. Brent |
1982 |  | R. P. Brent, J. van de Lune, H. J. J. te Riele, D. T. Winter |
1983 |  | J. van de Lune, H. J. J. te Riele |
1986 |  | J. van de Lune, H. J. J. te Riele, D. T. Winter |
2001 |  | J. van de Lune (unpublished) |
2004 |  | S. Wedeniwski |
2004 |  | X. Gourdon and P. Demichel |
Numerical evidence suggests that all values of

corresponding to nontrivial zeros are
irrational (e.g., Havil 2003, p. 195; Derbyshire 2004, p. 384).
No known zeros with order greater than one are known. While the existence of such zeros would not disprove the Riemann hypothesis, it would cause serious problems for many current computational techniques (Derbyshire 2004, p. 385).
Some nontrivial zeros lie extremely close together, a property known as
Lehmer's phenomenon.
The Riemann zeta function can be factored over its nontrivial zeros

as the
Hadamard product
![zeta(s)=(e^([ln(2pi)-1-gamma/2]s))/(2(s-1)Gamma(1+1/2s))product_(rho)(1-s/rho)e^(s/rho)](https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_s6dFkTE9pLuxcKlZv6qiRgZBSW_ImXfZ9eJJAAveQC-XzcSzG7xcFNQJc-r1sEl97GZVhtiovQaRkNXUxTM3KkRZU8uhFYKh2q3SoJJfTOyQ1MlnOB8mkO6vXP8IeZOOiiBptIlSALS2dv2Br5k5Y-fv8PCH2__KxDIsrHaoal=s0-d) |
(2)
|
(Titchmarsh 1987, Voros 1987).
Let

denote the

th nontrivial zero of

, and write the sums of the negative integer powers of such zeros as
 |
(3)
|
(Lehmer 1988, Keiper 1992). But by the functional equation, the nontrivial zeros are paired as

and

, so if the zeros with positive
imaginary part are written as

, then the sums become
![Z(n)=sum_(k)[(sigma_k+it_k)^(-n)+(1-sigma_k-it_k)^(-n)].](https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_tRyTkl1XN4OXQZ-T-ZH5WjdmII36eoI8oNUfa5Zw-_ePYCvPW5kdVHUQE6qEhaduM-P_hMEM9IfxDRljng9vJFb25IrtF7ePZZSfkgda7V30-rdHytPpxKh-hHHc5DWhiqqTBQzYw8bO6iNK4ZN1v4ykRqB8UY7GwhkCHwatad=s0-d) |
(4)
|
Such sums can be computed analytically, and the first few are
where

is the
Euler-Mascheroni constant,

are
Stieltjes constants,

is the
Riemann zeta function, and

is
Apéry's constant. These values can also be written in terms of the Li constants (Bombieri and Lagarias 1999).
The case
 |
(11)
|
(OEIS
A074760; Edwards 2001, p. 160) is classical and was known to Riemann, who used it in his computation of the roots of

(Davenport 1980, pp. 83-84; Edwards 2001, pp. 67 and 159). It is also equal to the constant

from
Li's criterion.
Assuming the truth of the
Riemann hypothesis (so that

), equation (◇) can be written for the first few values of

in the simple forms
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