PolyLog
Details
- Mathematical function, suitable for both symbolic and numerical manipulation.
.
.
. - PolyLog[n,z] has a branch cut discontinuity in the complex
plane running from 1 to
. - For certain special arguments, PolyLog automatically evaluates to exact values.
- PolyLog can be evaluated to arbitrary numerical precision.
- PolyLog automatically threads over lists.
- PolyLog can be used with Interval and CenteredInterval objects. »
Examples
open all close allBasic Examples (6)
PolyLog[3, 1 / 2]Plot over a subset of the reals:
Plot[PolyLog[2, x], {x, -2, 1}]Plot over a subset of the complexes:
ComplexPlot3D[PolyLog[2, z], {z, -2 - 2I, 2 + 2I}, PlotLegends -> Automatic]Series expansion at the origin:
Series[PolyLog[2, x], {x, 0, 10}]Series expansion at Infinity:
Series[PolyLog[2, x], {x, ∞, 6}]//NormalSeries expansion at a singular point:
Series[PolyLog[2, x], {x, 1, 2}, Assumptions -> x > 1]//NormalScope (33)
Numerical Evaluation (6)
PolyLog[2, .9]PolyLog[0, 5.0]N[PolyLog[1, 1 / 3], 50]The precision of the output tracks the precision of the input:
PolyLog[2, .300000000000000000]PolyLog[.2 + I, .5 - I]Evaluate efficiently at high precision:
PolyLog[2 / 3, 1 / 3`100]//TimingPolyLog[2 / 3, 1 / 8`1000];//TimingCompute worst-case guaranteed intervals using Interval and CenteredInterval objects:
PolyLog[2, Interval[{0.7, 0.8}]]PolyLog[2, CenteredInterval[-4, 1 / 100]]Compute average-case statistical intervals using Around:
PolyLog[1 / 2, Around[1 / 2, 0.01]]Compute the elementwise values of an array:
PolyLog[2, {{1 / 2, 0}, {0, 1 / 2}}]Or compute the matrix PolyLog function using MatrixFunction:
MatrixFunction[PolyLog[2, #]&, {{1 / 2, 0}, {0, 1 / 2}}]Specific Values (5)
Simple exact values are generated automatically:
Table[PolyLog[n, 1 ], {n, 1, 4}]PolyLog for symbolic z:
Table[PolyLog[n, z], {n, -2, 1}]PolyLog for symbolic n:
PolyLog[n, -1]PolyLog[1, 0]Find a value of z for which PolyLog[1,z ]=1:
zval = z /. Solve[PolyLog[1, z ] == 1, z][[1]]Plot[PolyLog[1, z ], {z, -1, 1}, Epilog -> Style[Point[{zval, PolyLog[1, zval ]}], PointSize[Large], Red]]Visualization (3)
Plot the PolyLog function as a function of its parameter n:
Plot[PolyLog[n, 2, 1 / 3], {n, 1, 10}]Plot the PolyLog function for various orders:
Plot[{PolyLog[3, x], PolyLog[4, x], PolyLog[5, x]}, {x, -10, 1}]Plot the real part of PolyLog function:
ComplexContourPlot[Re[PolyLog[2, z]], {z, -3 - 4I, 3 + 4I}, IconizedObject[«PLotOptions»]]Plot the imaginary part of PolyLog function:
ComplexContourPlot[Im[PolyLog[2, z]], {z, -3 - 4I, 3 + 4I}, IconizedObject[«PlotOptions»]]Function Properties (11)
Real domain of PolyLog:
FunctionDomain[PolyLog[n, x], x]FunctionDomain[PolyLog[n, z], z, Complexes]FunctionRange[PolyLog[2, x], x, y]PolyLog threads elementwise over lists:
PolyLog[4, {0.2, 0.5, 0.7}]PolyLog is not an analytic function:
FunctionAnalytic[PolyLog[n, x], x, Assumptions -> n > 1]PolyLog is not meromorphic:
FunctionMeromorphic[PolyLog[n, x], x, Assumptions -> n > 1]//Reduce
is non-decreasing on its real domain for
:
FunctionMonotonicity[{PolyLog[n, x], x ≤ 1}, x, Assumptions -> n > 1]For other values of
, it might or might not be monotonic:
FunctionMonotonicity[{PolyLog[1 / 2, x], x < 1}, x]FunctionMonotonicity[{PolyLog[-1 / 2, x], x < 1}, x]FunctionInjective[PolyLog[n, x], x, Assumptions -> n > 1]Plot[{PolyLog[2, x], 1}, {x, -5, 5}]FunctionSurjective[PolyLog[n, x], x, Assumptions -> n > 1]Plot[{PolyLog[2, x], 10}, {x, -10, 10}]PolyLog is neither non-negative nor non-positive:
FunctionSign[PolyLog[2, x], x]FunctionSign[{PolyLog[3, x], x < 1}, x]PolyLog has both singularity and discontinuity for x≥1:
FunctionSingularities[PolyLog[2, x], x]FunctionDiscontinuities[PolyLog[2, x], x]FunctionConvexity[{PolyLog[2, x], x ≤ 1}, x]TraditionalForm formatting:
PolyLog[n, z]//TraditionalFormPolyLog[n, p, z]//TraditionalFormDifferentiation (2)
First derivatives with respect to z:
D[PolyLog[n, z], z]D[PolyLog[n, p, z], z]Higher derivatives with respect to z:
Table[D[PolyLog[n, z], {z, k}], {k, 1, 3}]//FullSimplifyPlot the higher derivatives with respect to z when n=1/2:
Plot[Evaluate[% /. n -> 1 / 2], {z, -2, 2}, PlotLegends -> {"First Derivative", "Second Derivative", "Third Derivative"}]Series Expansions (2)
Find the Taylor expansion using Series:
Series[PolyLog[n, x], {x, 0, 8}]Plots of the first three approximations around
:
terms = Normal@Table[Series[PolyLog[3, x], {x, 0, m}], {m, 1, 5, 2}];
Plot[{PolyLog[3, x], terms}, {x, -10, 10}]Taylor expansion at a generic point:
Series[PolyLog[n, x], {x, x0, 2}]// FullSimplifyFunction Identities and Simplifications (4)
PolyLog is defined through the identity:
PolyLog[n, z] == Sum[z ^ k / k ^ n, {k, 1, ∞}]PolyLog[n, z] == Subsuperscript[∫, 0, z](1/t)PolyLog[n - 1, t]ⅆtFor positive integer
,
can be expressed in terms of hypergeometric functions:
Table[PolyLog[n, z] == z HypergeometricPFQ[ConstantArray[1, n + 1], ConstantArray[2, n], z]//FullSimplify, {n, 9}]For negative integer
,
is a rational function of
:
Table[PolyLog[-n, z] == (-1)^n + 1Underoverscript[∑, j = 0, n](j!StirlingS2[n + 1, j + 1]/(z - 1)^j + 1)//FullSimplify, {n, 9}]Generalizations & Extensions (7)
Ordinary Polylogarithm Function (5)
Infinite arguments give symbolic results:
PolyLog[2, Infinity]PolyLog can be applied to power series:
PolyLog[2, -1 + z + O[z] ^ 5]Derivative[2, 0][PolyLog][1, -1]Series expansion at branch cuts:
Series[PolyLog[2, z], {z, 2, 3}]Series[PolyLog[2, z], {z, Infinity, 5}]Give the result for an arbitrary symbolic direction:
Series[PolyLog[2, z], {z, DirectedInfinity[w], 3}]Applications (5)
Plot of the absolute value of the dilogarithm function in the complex plane:
ContourPlot[Abs[PolyLog[2, x + I y]], {x, -2, 2}, {y, -2, 2}]Calculate integrals over Bose–Einstein distributions:
Integrate[(ϵ^α/E^ϵ - μ - 1), {ϵ, 0, Infinity}, Assumptions -> α ≥ -1 / 2]Calculate integrals over Fermi–Dirac distributions:
Integrate[(ϵ^α/E^ϵ - μ + 1), {ϵ, 0, Infinity}, Assumptions -> α ≥ -1 / 2]Volume of a hyperbolic ideal tetrahedron with vertices at
, 0, 1,
(subject to
):
v[z_] := Im[PolyLog[2, z]] + Arg[1 - z] Log[Abs[z]]Plot the volume as a function of the vertex
:
Plot3D[v[x + I y], {x, -5, 5}, {y, 0, 5}]Mahler measure of the trivariate polynomial
as a function of
:
m[a_] = Piecewise[{{(2/Pi^2)(PolyLog[3, a] - PolyLog[3, -a]), 0 ≤ a ≤ 1}, {Log[a] + (2/Pi^2)(PolyLog[3, 1 / a] - PolyLog[3, -1 / a]), a > 1}}]Plot[m[a], {a, 0, 100}]Generate the Eulerian numbers [MathWorld]:
Table[Rest[CoefficientList[(1 - t)^n + 1PolyLog[-n, t], t]], {n, 9}]//ColumnProperties & Relations (6)
Use FullSimplify to simplify polylogarithms:
FullSimplify[PolyLog[2, 1 - z] + PolyLog[2, z] + Log[z] Log[1 - z]]Use FunctionExpand to expand polylogarithms:
PolyLog[2, 1 - I]FunctionExpand[%]FunctionExpand[PolyLog[2, Exp[I Pi / 3]]]Numerically find a root of a transcendental equation:
FindRoot[PolyLog[2, z] - 2 PolyLog[2, z + 2] + z == 2, {z, 3 + I}]Integrate[(PolyLog[2, z]/(z - 1)^2), z]Integrate[t ^ a PolyLog[2, t], {t, 0, 1}]Generate from integrals and sums:
Sum[z ^ k / k ^ ν, {k, 1, Infinity}]Sum[HarmonicNumber[n, r] z ^ n, {n, Infinity}]Integrate[t ^ (ν - 1) / (E ^ t - z), {t, 0, Infinity}]PolyLog appears in special cases of various mathematical functions:
HypergeometricPFQ[{1, 1, 1}, {2, 2}, z]HurwitzLerchPhi[z, n, 1]Neat Examples (1)
Plot the Riemann surface of the dilogarithm
:
With[{ε = 1*^-12},
ParametricPlot3D[Table[{r Cos[φ], r Sin[φ], Im[PolyLog[2, r Exp[I φ]] + 2π I(Log[r] + I φ) j]}, {j, -2, 2}], {r, 0, 4}, {φ, ε, 2π - ε}, BoxRatios -> {1, 1, 3}, Mesh -> None, PlotRange -> {All, All, {-12, 12}}, PlotStyle -> Directive[Hue[0.86], Opacity[0.6]]]]See Also
Zeta PolyGamma LerchPhi HarmonicPolyLog GeneralizedPolyLog MultiplePolyLog AlternatingHarmonicNumber
Function Repository: PolyLogSimplify
Related Guides
Related Links
History
Introduced in 1988 (1.0) | Updated in 1999 (4.0) ▪ 2000 (4.1) ▪ 2002 (4.2) ▪ 2021 (13.0) ▪ 2022 (13.1)
Text
Wolfram Research (1988), PolyLog, Wolfram Language function, https://reference.wolfram.com/language/ref/PolyLog.html (updated 2022).
CMS
Wolfram Language. 1988. "PolyLog." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2022. https://reference.wolfram.com/language/ref/PolyLog.html.
APA
Wolfram Language. (1988). PolyLog. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/PolyLog.html
BibTeX
@misc{reference.wolfram_2026_polylog, author="Wolfram Research", title="{PolyLog}", year="2022", howpublished="\url{https://reference.wolfram.com/language/ref/PolyLog.html}", note=[Accessed: 12-June-2026]}
BibLaTeX
@online{reference.wolfram_2026_polylog, organization={Wolfram Research}, title={PolyLog}, year={2022}, url={https://reference.wolfram.com/language/ref/PolyLog.html}, note=[Accessed: 12-June-2026]}