§25.2 Definition and Expansions ‣ Riemann Zeta Function ‣ Chapter 25 Zeta and Related Functions (original) (raw)

Contents
  1. §25.2(i) Definition
  2. §25.2(ii) Other Infinite Series
  3. §25.2(iii) Representations by the Euler–Maclaurin Formula
  4. §25.2(iv) Infinite Products

§25.2(i) Definition

When ℜ⁡s>1,

25.2.1 ζ⁡(s)=∑n=1∞1ns.

Elsewhere ζ⁡(s) is defined by analytic continuation. It is a meromorphic function whose only singularity in ℂ is a simple pole ats=1, with residue 1.

§25.2(ii) Other Infinite Series

25.2.2 ζ⁡(s)=11−2−s⁢∑n=0∞1(2⁢n+1)s,
ℜ⁡s>1.
ⓘ Symbols: ζ⁡(s): Riemann zeta function,ℜ⁡: real part,n: nonnegative integer ands: complex variable Keywords: infinite series Proof sketch: Derivable from (25.2.1). A&S Ref: 23.2.20 (is the special case with integer values of s) Referenced by: (25.11.11) Permalink: http://dlmf.nist.gov/25.2.E2 Encodings: TeX, pMML, png See also: Annotations for §25.2(ii),§25.2 andCh.25
25.2.3 ζ⁡(s)=11−21−s⁢∑n=1∞(−1)n−1ns,
ℜ⁡s>0.
ⓘ Symbols: ζ⁡(s): Riemann zeta function,ℜ⁡: real part,n: nonnegative integer ands: complex variable Keywords: infinite series Source: Apostol (1976, (27), p. 292) A&S Ref: 23.2.19 (is the special case with integer values of s) Referenced by: §25.11(x) Permalink: http://dlmf.nist.gov/25.2.E3 Encodings: TeX, pMML, png See also: Annotations for §25.2(ii),§25.2 andCh.25
25.2.4 ζ⁡(s)=1s−1+∑n=0∞(−1)nn!⁢γn⁢(s−1)n,

where the Stieltjes constants γn are defined via

25.2.5 γn=limm→∞(∑k=1m(ln⁡k)nk−(ln⁡m)n+1n+1).
25.2.6 ζ′⁡(s)=−∑n=2∞(ln⁡n)⁢n−s,
ℜ⁡s>1.
ⓘ Symbols: ζ⁡(s): Riemann zeta function,ln⁡z: principal branch of logarithm function,ℜ⁡: real part,n: nonnegative integer ands: complex variable Keywords: infinite series Source: Apostol (1976, (12), p. 236) Permalink: http://dlmf.nist.gov/25.2.E6 Encodings: TeX, pMML, png See also: Annotations for §25.2(ii),§25.2 andCh.25
25.2.7 ζ(k)⁡(s)=(−1)k⁢∑n=2∞(ln⁡n)k⁢n−s,
ℜ⁡s>1, k=1,2,3,….
ⓘ Symbols: ζ⁡(s): Riemann zeta function,ln⁡z: principal branch of logarithm function,ℜ⁡: real part,k: nonnegative integer,n: nonnegative integer ands: complex variable Keywords: infinite series Source: Apostol (1976, p. 236); with f⁢(n)=1 Permalink: http://dlmf.nist.gov/25.2.E7 Encodings: TeX, pMML, png See also: Annotations for §25.2(ii),§25.2 andCh.25

For further expansions of functions similar to (25.2.1) (Dirichlet series) see §27.4. This includes, for example, 1/ζ⁡(s).

§25.2(iii) Representations by the Euler–Maclaurin Formula

25.2.8 ζ⁡(s)=∑k=1N1ks+N1−ss−1−s⁢∫N∞x−⌊x⌋xs+1⁢dx,
ℜ⁡s>0, N=1,2,3,….
ⓘ Symbols: ζ⁡(s): Riemann zeta function,dx: differential of x,⌊x⌋: floor of x,∫: integral,ℜ⁡: real part,k: nonnegative integer,x: real variable,a: real or complex parameter ands: complex variable Keywords: Euler–Maclaurin formula, improper integral Source: Apostol (1976, (25), p. 269) Proof sketch: Derivable from Apostol (1976, Theorem 12.21, p. 269) by settinga=1 and N↦N−1. A&S Ref: 23.2.9 Referenced by: (25.2.9) Permalink: http://dlmf.nist.gov/25.2.E8 Encodings: TeX, pMML, png See also: Annotations for §25.2(iii),§25.2 andCh.25
25.2.9 ζ⁡(s)=∑k=1N1ks+N1−ss−1−12⁢N−s+∑k=1n(s+2⁢k−22⁢k−1)⁢B2⁢k2⁢k⁢N1−s−2⁢k−(s+2⁢n2⁢n+1)⁢∫N∞B~2⁢n+1⁡(x)xs+2⁢n+1⁢dx,
ℜ⁡s>−2⁢n; n,N=1,2,3,….
ⓘ Symbols: Bn: Bernoulli numbers,ζ⁡(s): Riemann zeta function,(mn): binomial coefficient,dx: differential of x,∫: integral,B~n⁡(x): periodic Bernoulli functions,ℜ⁡: real part,k: nonnegative integer,n: nonnegative integer,x: real variable ands: complex variable Keywords: Euler–Maclaurin formula, improper integral Proof sketch: Derivable from (25.2.8) by repeated integration by parts. Referenced by: §25.18(i),(25.2.10) Permalink: http://dlmf.nist.gov/25.2.E9 Encodings: TeX, pMML, png See also: Annotations for §25.2(iii),§25.2 andCh.25
25.2.10 ζ⁡(s)=1s−1+12+∑k=1n(s+2⁢k−22⁢k−1)⁢B2⁢k2⁢k−(s+2⁢n2⁢n+1)⁢∫1∞B~2⁢n+1⁡(x)xs+2⁢n+1⁢dx,
ℜ⁡s>−2⁢n, n=1,2,3,….
ⓘ Symbols: Bn: Bernoulli numbers,ζ⁡(s): Riemann zeta function,(mn): binomial coefficient,dx: differential of x,∫: integral,B~n⁡(x): periodic Bernoulli functions,ℜ⁡: real part,k: nonnegative integer,n: nonnegative integer,x: real variable ands: complex variable Keywords: Euler–Maclaurin formula Proof sketch: Derivable from (25.2.9) with N=1. A&S Ref: 23.2.3 Permalink: http://dlmf.nist.gov/25.2.E10 Encodings: TeX, pMML, png See also: Annotations for §25.2(iii),§25.2 andCh.25

For B2⁢k see §24.2(i), and for B~n⁡(x)see §24.2(iii).

§25.2(iv) Infinite Products

25.2.11 ζ⁡(s)=∏p(1−p−s)−1,
ℜ⁡s>1,
ⓘ Symbols: ζ⁡(s): Riemann zeta function,ℜ⁡: real part,p: prime number ands: complex variable Keywords: infinite product, primes Source: Apostol (1976, p. 231) A&S Ref: 23.2.2 Referenced by: §25.10(i) Permalink: http://dlmf.nist.gov/25.2.E11 Encodings: TeX, pMML, png See also: Annotations for §25.2(iv),§25.2 andCh.25

product over all primes p.

25.2.12 ζ⁡(s)=(2⁢π)s⁢e−s−(γ⁢s/2)2⁢(s−1)⁢Γ⁡(12⁢s+1)⁢∏ρ(1−sρ)⁢es/ρ,

product over zeros ρ of ζ with ℜ⁡ρ>0 (see §25.10(i)); γ is Euler’s constant (§5.2(ii)).