KelvinBei
Details
- Mathematical function, suitable for both symbolic and numerical manipulation.
- For positive real values of parameters,
. For other values,
is defined by analytic continuation. - KelvinBei[n,z] has a branch cut discontinuity in the complex z plane running from
to
. - KelvinBei[z] is equivalent to KelvinBei[0,z].
- For certain special arguments, KelvinBei automatically evaluates to exact values.
- KelvinBei can be evaluated to arbitrary numerical precision.
- KelvinBei automatically threads over lists.
Examples
open all close allBasic Examples (6)
KelvinBei[2.5]Plot
over a subset of the reals:
ReImPlot[KelvinBei[x], {x, 0, 10}, PlotRange -> All]Plot over a subset of the complexes:
ComplexPlot3D[KelvinBei[2, z], {z, -2 - 2I, 2 + 2I}, PlotLegends -> Automatic]Series expansion at the origin:
Series[KelvinBei[x], {x, 0, 15}]Series expansion at Infinity:
Series[KelvinBei[x], {x, ∞, 2}]//FullSimplify//NormalSeries expansion at a singular point:
Series[KelvinBei[n, x], {x, -1, 2}, Assumptions -> x > 1]//FullSimplifyScope (37)
Numerical Evaluation (6)
KelvinBei[.5]KelvinBei[4588, 0]N[KelvinBei[-7, 8], 50]N[KelvinBei[-2], 50]The precision of the output tracks the precision of the input:
KelvinBei[2, 0.20444444000555555008005]N[KelvinBei[2.47, 5 - I]]N[KelvinBei[I + 2.47, 5]]Evaluate efficiently at high precision:
KelvinBei[7, 5`100]//TimingKelvinBei[7, 5`100000];//TimingCompute average-case statistical intervals using Around:
KelvinBei[Around[.9, 0.1]]Compute the elementwise values of an array:
KelvinBei[1, {{0, 1.2}, {1.2, 0}}]Or compute the matrix KelvinBei function using MatrixFunction:
MatrixFunction[KelvinBei[1, #]&, {{0, 1.2}, {1.2, 0}}]Specific Values (3)
KelvinBei[0]KelvinBei[1, 0]Find the positive minimum of KelvinBei[0,x]:
xmin = x /. FindRoot[D[KelvinBei[0, x], x] == 0, {x, 8}]Plot[KelvinBei[0, x], {x, -1, 10}, Epilog -> Style[Point[{xmin, KelvinBei[0, xmin]}], PointSize[Large], Red]]For half-integer orders, KelvinBei evaluates to elementary functions:
Table[KelvinBei[n, x Sqrt[2]], {n, {-1 / 2, 1 / 2}}]//FunctionExpandVisualization (3)
Plot the KelvinBei function for integer (
) and half-integer (
) orders:
Plot[{KelvinBei[0, x], KelvinBei[1, x], KelvinBei[-1 / 2, x]}, {x, 0, 10}]ComplexContourPlot[Re[KelvinBei[0, z]], {z, -3 - 6I, 3 + 6I}, IconizedObject[«PlotOptions»]]ComplexContourPlot[Im[KelvinBei[0, z]], {z, -3 - 6I, 3 + 6I}, IconizedObject[«PlotOptions»]]ComplexContourPlot[Re[KelvinBei[-1 / 4, z]], {z, -3 - 6I, 3 + 6I}, IconizedObject[«PlotOptions»]]ComplexContourPlot[Im[KelvinBei[-1 / 4, z]], {z, -3 - 6I, 3 + 6I}, IconizedObject[«PlotOptions»]]Function Properties (12)
FunctionDomain[KelvinBei[0, x], x]FunctionDomain[KelvinBei[0, z], z, Complexes]
is defined for all real values greater than 0:
FunctionDomain[KelvinBei[-1 / 2, x], x]The complex domain is the whole plane except
:
FunctionDomain[KelvinBei[-1 / 2, z], z, Complexes]FunctionRange[KelvinBei[0, x], x, y]Approximate function range of
:
FunctionRange[KelvinBei[1, x], x, y]//QuietKelvinBei[0, -x]KelvinBei[1, -x]FunctionAnalytic[KelvinBei[0, z], z]KelvinBei is neither non-decreasing nor non-increasing:
Table[FunctionMonotonicity[KelvinBei[n, x], x, PositiveReals], {n, 4}]Table[FunctionMonotonicity[KelvinBei[1 / n, x], x, PositiveReals], {n, 4}]KelvinBei is not injective:
Table[FunctionInjective[KelvinBei[n, x], x], {n, 4}]Table[FunctionInjective[KelvinBei[1 / n, x], x], {n, 4}]Plot[{KelvinBei[1, x], KelvinBei[2, x], KelvinBei[1 / 3, x], -3, 1}, {x, 0, 7}]KelvinBei is neither non-negative nor non-positive:
Table[FunctionSign[KelvinBei[n, x], x, PositiveReals], {n, 4}]
has singularities or discontinuities in the non-positive reals when
is not an integer:
FunctionSingularities[KelvinBei[n, x], x]FunctionDiscontinuities[KelvinBei[n, x], x]KelvinBei is neither convex nor concave:
Table[FunctionConvexity[{KelvinBei[a, x], x > 0}, x], {a, 5}]TraditionalForm formatting:
KelvinBei[n, x]//TraditionalFormDifferentiation (3)
The first derivative with respect to
:
D[KelvinBei[x] , x]The first derivative with respect to
when
:
D[KelvinBei[1, x] , x]Higher derivatives with respect to
:
Table[D[KelvinBei[x], {x, k}], {k, 1, 5}]//SimplifyPlot the higher derivatives with respect to
:
Plot[%, {x, -20, 20}, PlotLegends -> {"First Derivative", "Second Derivative", "Third Derivative", "Fourth Derivative", "Fifth Derivative"}]Formula for the ![]()
derivative with respect to
:
D[KelvinBei[x], {x, k}]// FullSimplifyIntegration (3)
Compute the indefinite integral using Integrate:
Integrate[KelvinBei[x], x]// FullSimplifyFullSimplify[D[%, x]]// FullSimplifyIntegrate[KelvinBei[x], {x, 0, 5}]Integrate[x KelvinBei[x]^2, x]// FullSimplifyIntegrate[x^2 KelvinBei[x], {x, 0, 5}]// FullSimplifySeries Expansions (5)
Find the Taylor expansion using Series:
Series[KelvinBei[n, x], {x, 0, 4}]Plots of the first three approximations around
:
terms = Normal@Table[Series[KelvinBei[x], {x, 1, m}], {m, 1, 5, 2}];
Plot[{KelvinBei[x], terms}, {x, 0, 10}, PlotRange -> {{0, 9}, {-10, 10}}]The general term in the series expansion using SeriesCoefficient:
SeriesCoefficient[KelvinBei[x], {x, 1, m}]// FullSimplifyFind the series expansion at Infinity:
Series[KelvinBei[x], {x, Infinity, 1}]//Normal//FullSimplifyFind series expansion for an arbitrary symbolic direction
:
Series[KelvinBei[x], {x, DirectedInfinity[z], 1}, Assumptions -> x > 0 && z > 0]//Normal//FullSimplify//QuietThe Taylor expansion at a generic point:
Series[KelvinBei[x], {x, x0, 2}]//FullSimplifyFunction Identities and Simplifications (2)
KelvinBei[n, x] == (x/2 Sqrt[2] n)(-KelvinBei[-1 + n, x] - KelvinBei[1 + n, x] + KelvinBer[-1 + n, x] + KelvinBer[1 + n, x])//FullSimplifyKelvinBei[n, x] == -KelvinBei[2 + n, x] - (Sqrt[2] (1 + n) (KelvinBei[1 + n, x] + KelvinBer[1 + n, x])/x)//FullSimplifyGeneralizations & Extensions (1)
KelvinBei can be applied to a power series:
KelvinBei[Log[1 + x] + O[x] ^ 7]Applications (3)
Solve the Kelvin differential equation:
DSolve[x^4 Derivative[4][f][x] + 2 x^3 Derivative[3][f][x] - (1 + 2 n^2) (-x Derivative[1][f][x] + x^2 Derivative[2][f][x]) + (-4 n^2 + n^4 + x^4) f[x] == 0, f[x], x]Plot the resistance of a wire with circular cross section versus AC frequency (skin effect):
Plot[ω / 2 ( KelvinBer[ω]KelvinBei'[ω] - KelvinBei[ω]KelvinBer'[ω]) / (KelvinBer'[ω] ^ 2 + KelvinBei'[ω] ^ 2), {ω, 0, 4}]For some specific values, HypergeometricPFQRegularized is represented with KelvinBei:
(π z^2/16) HypergeometricPFQRegularized[{}, {(3/2), (3/2), 1}, -(z^4/256)]Properties & Relations (5)
The one‐argument form evaluates to the two-argument form:
KelvinBei[x]Use FullSimplify to simplify expressions involving Kelvin functions:
D[x KelvinBei[1, x], x]FullSimplify[%]Use FunctionExpand to expand Kelvin functions of half-integer orders:
FunctionExpand[KelvinBei[1 / 2, x]]Integrate expressions involving Kelvin functions:
Integrate[x (KelvinBer[x]^2 + KelvinBei[x]^2), x]KelvinBei can be represented in terms of MeijerG:
MeijerGReduce[KelvinBei[n, x], x]Activate[%]//FullSimplifyTech Notes
Related Guides
Related Links
History
Text
Wolfram Research (2007), KelvinBei, Wolfram Language function, https://reference.wolfram.com/language/ref/KelvinBei.html.
CMS
Wolfram Language. 2007. "KelvinBei." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/KelvinBei.html.
APA
Wolfram Language. (2007). KelvinBei. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/KelvinBei.html
BibTeX
@misc{reference.wolfram_2026_kelvinbei, author="Wolfram Research", title="{KelvinBei}", year="2007", howpublished="\url{https://reference.wolfram.com/language/ref/KelvinBei.html}", note=[Accessed: 13-June-2026]}
BibLaTeX
@online{reference.wolfram_2026_kelvinbei, organization={Wolfram Research}, title={KelvinBei}, year={2007}, url={https://reference.wolfram.com/language/ref/KelvinBei.html}, note=[Accessed: 13-June-2026]}