Lerch's Transcendent

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Lerch's Transcendent

Definition

Ξ¦ ⁑ ( z , s , a ) = βˆ‘ n = 0 ∞ z n ( a + n ) s Lerch-Phi 𝑧 𝑠 π‘Ž superscript subscript 𝑛 0 superscript 𝑧 𝑛 superscript π‘Ž 𝑛 𝑠 {\displaystyle{\displaystyle{\displaystyle{\Phi\left(z,s,a\right)=\sum_{n=0}^{% \infty}\frac{z^{n}}{(a+n)^{s}}}}}} {\displaystyle { \LerchPhi@{z}{s}{a} = \sum_{n=0}^\infty \frac{z^n}{(a+n)^s} } }

Constraint(s): a β‰  0 , - 1 , - 2 , … , | z | < 1 formulae-sequence π‘Ž 0 1 2 … 𝑧 1 {\displaystyle{\displaystyle{\displaystyle a\neq 0,-1,-2,\dots,|z|<1}}} &
β„œ ⁑ s > 1 , | z | = 1 formulae-sequence 𝑠 1 𝑧 1 {\displaystyle{\displaystyle{\displaystyle\Re{s}>1,|z|=1}}}


\HurwitzZeta ⁒ @ ⁒ s ⁒ a = Ξ¦ ⁑ ( 1 , s , a ) \HurwitzZeta @ 𝑠 π‘Ž Lerch-Phi 1 𝑠 π‘Ž {\displaystyle{\displaystyle{\displaystyle\HurwitzZeta@{s}{a}=\Phi\left(1,s,a% \right)}}} {\displaystyle \HurwitzZeta@{s}{a} = \LerchPhi@{1}{s}{a} }

Constraint(s): β„œ ⁑ s > 1 𝑠 1 {\displaystyle{\displaystyle{\displaystyle\Re{s}>1}}} &
a β‰  0 , - 1 , - 2 , … π‘Ž 0 1 2 … {\displaystyle{\displaystyle{\displaystyle a\neq 0,-1,-2,\dots}}}


\Polylogarithm ⁒ s ⁒ @ ⁒ z = z ⁒ Ξ¦ ⁑ ( z , s , 1 ) \Polylogarithm 𝑠 @ 𝑧 𝑧 Lerch-Phi 𝑧 𝑠 1 {\displaystyle{\displaystyle{\displaystyle\Polylogarithm{s}@{z}=z\Phi\left(z,s% ,1\right)}}} {\displaystyle \Polylogarithm{s}@{z} = z \LerchPhi@{z}{s}{1} }

Constraint(s): β„œ ⁑ s > 1 𝑠 1 {\displaystyle{\displaystyle{\displaystyle\Re{s}>1}}} &
| z | ≀ 1 𝑧 1 {\displaystyle{\displaystyle{\displaystyle|z|\leq 1}}}


Properties

Ξ¦ ⁑ ( z , s , a ) = z m ⁒ Ξ¦ ⁑ ( z , s , a + m ) + βˆ‘ n = 0 m - 1 z n ( a + n ) s Lerch-Phi 𝑧 𝑠 π‘Ž superscript 𝑧 π‘š Lerch-Phi 𝑧 𝑠 π‘Ž π‘š superscript subscript 𝑛 0 π‘š 1 superscript 𝑧 𝑛 superscript π‘Ž 𝑛 𝑠 {\displaystyle{\displaystyle{\displaystyle\Phi\left(z,s,a\right)=z^{m}\Phi% \left(z,s,a+m\right)+\sum_{n=0}^{m-1}\frac{z^{n}}{(a+n)^{s}}}}} {\displaystyle \LerchPhi@{z}{s}{a} = z^m \LerchPhi@{z}{s}{a+m} + \sum_{n=0}^{m-1} \frac{z^n}{(a+n)^s} }

Constraint(s): a β‰  0 , - 1 , - 2 , … , | z | < 1 formulae-sequence π‘Ž 0 1 2 … 𝑧 1 {\displaystyle{\displaystyle{\displaystyle a\neq 0,-1,-2,\dots,|z|<1}}} &
β„œ ⁑ s > 1 , | z | = 1 formulae-sequence 𝑠 1 𝑧 1 {\displaystyle{\displaystyle{\displaystyle\Re{s}>1,|z|=1}}} &
m = 1 , 2 , 3 , … π‘š 1 2 3 … {\displaystyle{\displaystyle{\displaystyle m=1,2,3,\dots}}}


Ξ¦ ⁑ ( z , s , a ) = 1 Ξ“ ⁑ ( s ) ⁒ ∫ 0 ∞ x s - 1 ⁒ e - a ⁒ x 1 - z ⁒ e - x ⁒ d x Lerch-Phi 𝑧 𝑠 π‘Ž 1 Euler-Gamma 𝑠 superscript subscript 0 superscript π‘₯ 𝑠 1 π‘Ž π‘₯ 1 𝑧 π‘₯ π‘₯ {\displaystyle{\displaystyle{\displaystyle\Phi\left(z,s,a\right)=\frac{1}{% \Gamma\left(s\right)}\int_{0}^{\infty}\frac{x^{s-1}{\mathrm{e}^{-ax}}}{1-z{% \mathrm{e}^{-x}}}\mathrm{d}x}}} {\displaystyle \LerchPhi@{z}{s}{a} = \frac{1}{\EulerGamma@{s}} \int_0^\infty \frac{x^{s-1} \expe^{-ax}}{1-z\expe^{-x}} \diff{x} }

Constraint(s): β„œ ⁑ s > 0 𝑠 0 {\displaystyle{\displaystyle{\displaystyle\Re{s}>0}}} &
β„œ ⁑ a > 0 π‘Ž 0 {\displaystyle{\displaystyle{\displaystyle\Re{a}>0}}} &
z ∈ \Complex βˆ– [ 1 , ∞ ) 𝑧 \Complex 1 {\displaystyle{\displaystyle{\displaystyle z\in\Complex\setminus[1,\infty)}}}


Ξ¦ ⁑ ( z , s , a ) = 1 2 ⁒ a - s + ∫ 0 ∞ z x ( a + x ) s ⁒ d x - 2 ⁒ ∫ 0 ∞ sin ⁑ ( x ⁒ ln ⁑ z - s ⁒ arctan ⁑ ( x / a ) ) ( a 2 + x 2 ) s / 2 ⁒ ( e 2 ⁒ Ο€ ⁒ x - 1 ) ⁒ d x Lerch-Phi 𝑧 𝑠 π‘Ž 1 2 superscript π‘Ž 𝑠 superscript subscript 0 superscript 𝑧 π‘₯ superscript π‘Ž π‘₯ 𝑠 π‘₯ 2 superscript subscript 0 π‘₯ 𝑧 𝑠 π‘₯ π‘Ž superscript superscript π‘Ž 2 superscript π‘₯ 2 𝑠 2 2 π‘₯ 1 π‘₯ {\displaystyle{\displaystyle{\displaystyle\Phi\left(z,s,a\right)=\frac{1}{2}a^% {-s}+\int_{0}^{\infty}\frac{z^{x}}{(a+x)^{s}}\mathrm{d}x-2\int_{0}^{\infty}% \frac{\sin\left(x\ln z-s\operatorname{arctan}\left(x/a\right)\right)}{(a^{2}+x% ^{2})^{s/2}({\mathrm{e}^{2\pi x}}-1)}\mathrm{d}x}}} {\displaystyle \LerchPhi@{z}{s}{a} = \frac{1}{2} a^{-s} + \int_0^\infty \frac{z^x}{(a+x)^s} \diff{x} - 2 \int_0^\infty \frac{\sin@{x \ln@@{z} - s \atan@{x/a}}} {(a^2 + x^2)^{s/2} (\expe^{2 \cpi x} - 1)} \diff{x} }

Constraint(s): β„œ ⁑ s > 0 𝑠 0 {\displaystyle{\displaystyle{\displaystyle\Re{s}>0}}} if | z | < 1 𝑧 1 {\displaystyle{\displaystyle{\displaystyle|z|<1}}} &
β„œ ⁑ s > 1 𝑠 1 {\displaystyle{\displaystyle{\displaystyle\Re{s}>1}}} if | z | = 1 , β„œ ⁑ a > 0 formulae-sequence 𝑧 1 π‘Ž 0 {\displaystyle{\displaystyle{\displaystyle|z|=1,\Re{a}>0}}}