BesselY[n,z]
gives the Bessel function of the second kind
.
BesselY
BesselY[n,z]
gives the Bessel function of the second kind
.
Details
- Mathematical function, suitable for both symbolic and numerical manipulation.
satisfies the differential equation
. - BesselY[n,z] has a branch cut discontinuity in the complex z plane running from
to
. - FullSimplify and FunctionExpand include transformation rules for BesselY.
- For certain special arguments, BesselY automatically evaluates to exact values.
- BesselY can be evaluated to arbitrary numerical precision.
- BesselY automatically threads over lists.
- BesselY can be used with Interval and CenteredInterval objects. »
Examples
open all close allBasic Examples (5)
BesselY[0, 2.5]Plot
over a subset of the reals:
Plot[BesselY[0, r], {r, 0, 15}]Plot over a subset of the complexes:
ComplexPlot3D[BesselY[1 / 2, z], {z, -2 - 2I, 2 + 2I}, PlotLegends -> Automatic]Series expansion at the origin:
Series[BesselY[0, x], {x, 0, 3}]Series expansion at Infinity:
Series[BesselY[0, x], {x, ∞, 2}]//NormalScope (44)
Numerical Evaluation (6)
BesselY[0, 1.0]N[BesselY[0, 1], 50]The precision of the output tracks the precision of the input:
BesselY[0, 1.0000000000000000000000000000000000000000]Evaluate for complex arguments and parameters:
BesselY[0.5 I, 3 - I]Evaluate BesselY efficiently at high precision:
BesselY[0, 1`500]//TimingBesselY[0, 1`5000];//TimingCompute worst-case guaranteed intervals using Interval and CenteredInterval objects:
BesselY[1 / 2, Interval[{1, 1.2}]]BesselY[1 / 2, CenteredInterval[2, 1 / 100]]Or compute average-case statistical intervals using Around:
BesselY[2, Around[2, 0.01]]Compute the elementwise values of an array:
BesselY[0.5, {{1, 2}, {3, 4}}]Or compute the matrix BesselY function using MatrixFunction:
MatrixFunction[BesselY[0.5, #]&, {{1, 2}, {3, 4}}]Specific Values (4)
Value of BesselY for integers (
) orders at
:
{BesselY[0, 0], BesselY[1, 0]}For half-integer indices, BesselY evaluates to elementary functions:
Table[BesselY[(2n + 1) / 2, x], {n, 0, 2}]Limit[BesselY[n, x], x -> Infinity]{BesselYZero[0, 1], BesselYZero[0, 2], BesselYZero[0, 3]}//NFind the first zero of
using Solve:
sol = Solve[BesselY[0, x] == 0 && 0 < x < 3, x]//Nxzero = x /. First@sol;Plot[BesselY[0, x], {x, -1, 8}, Epilog -> Style[Point[{xzero, BesselY[0, xzero]}], PointSize[Large], Red]]Visualization (3)
Plot the BesselY function for integer orders (
):
Plot[{BesselY[0, x], BesselY[1, x], BesselY[2, x]}, {x, 0, 10}]Plot the real and imaginary parts of the BesselY function for integer orders (
):
ReImPlot[{BesselY[0, x], BesselY[1, x], BesselY[2, x]}, {x, -5, 5}]ComplexContourPlot[Re[BesselY[0, z]], {z, -4 - 4I, 8 + 4I}, IconizedObject[«PlotOptions»]]ComplexContourPlot[Im[BesselY[0, z]], {z, -4 - 4I, 8 + 4I}, IconizedObject[«PlotOptions»]]Function Properties (10)
is defined for all real values greater than 0:
FunctionDomain[BesselY[n, x], x]FunctionDomain[BesselY[n, z], z, Complexes]Approximate function range of
:
FunctionRange[BesselY[0, x], x, y]//NApproximate function range of
:
FunctionRange[BesselY[1, x], x, y]//NTable[FunctionAnalytic[BesselY[n, z], z], {n, -2, 2}]BesselY is neither non-decreasing nor non-increasing:
Table[FunctionMonotonicity[BesselY[n, z], z], {n, 5}]Table[FunctionMonotonicity[BesselY[1 / n, z], z], {n, 5}]BesselY is not injective:
Table[FunctionInjective[BesselY[n, z], z], {n, 5}]Table[FunctionInjective[BesselY[1 / n, z], z], {n, 5}]Plot[{BesselY[1, z], BesselY[2, z], BesselY[1 / 3, z], .2}, {z, 0, 15}]BesselY is not surjective:
Table[FunctionSurjective[BesselY[n, z], z], {n, 5}]Table[FunctionSurjective[BesselY[1 / n, z], z], {n, 5}]Plot[{BesselY[1, z], BesselY[2, z], BesselY[1 / 3, z], 1}, {z, 0, 15}]BesselY is neither non-negative nor non-positive:
Table[FunctionSign[BesselY[n, z], z], {n, 4}]
has both singularity and discontinuity for z≤0:
FunctionSingularities[BesselY[n, z], z]FunctionDiscontinuities[BesselY[n, z], z]BesselY is neither convex nor concave:
Table[FunctionConvexity[BesselY[a, z], z], {a, 5}]TraditionalForm formatting:
BesselY[n, r]//TraditionalFormDifferentiation (3)
D[BesselY[n, x], x]derivs = Table[D[BesselY[n, x], {x, k}], {k, 1, 4}]Plot[Evaluate[derivs /. n -> 0], {x, 0, 10}, PlotLegends -> {"First Derivative", "Second Derivative", "Third Derivative", "Fourth Derivative"}]D[BesselY[n, x], {x, j}]Integration (3)
Indefinite integral of BesselY:
Integrate[BesselY[n, x], x]Integrate expressions involving BesselY:
Integrate[r BesselY[n, r] ^ 2 , r]Integrate[BesselY[0, r], r]Definite integral of BesselY over its real domain:
Integrate[BesselY[n, x], {x, 0, Infinity}]Series Expansions (5)
Series[BesselY[0, x], {x, 1, 3}]Plot the first three approximations for
around
:
terms = Normal@Table[Series[BesselY[0, x], {x, 1, m}], {m, 1, 3}];
Plot[{BesselY[0, x], terms}, {x, 0.5, 2.5}]General term in the series expansion of BesselY:
SeriesCoefficient[BesselY[0, x], {x, 1, n}]Asymptotic approximation of BesselY:
Series[BesselY[n, x], {x, Infinity, 0}]Taylor expansion at a generic point:
Series[BesselY[n, x], {x, x0, 2}]// FullSimplifyBesselY can be applied to a power series:
BesselY[1, x / (1 + x) + O[x] ^ 2]Integral Transforms (3)
Compute the Laplace transform using LaplaceTransform:
LaplaceTransform[BesselY[n, t], t, s]HankelTransform[BesselY[n, r], r, s ]MellinTransform[BesselY[n, x], x, s]Function Identities and Simplifications (3)
Use FullSimplify to simplify Bessel functions:
FullSimplify[ r BesselY[2, r] + r BesselY[0, r]]FullSimplify[z(BesselY[n - 1, z] + BesselY[n + 1, z]) == 2n BesselY[n, z]]For integer
and arbitrary fixed
,
:
FullSimplify[BesselY[-n, z] == (-1)^n BesselY[n, z], n∈ℤ]Function Representations (4)
Integral representation of BesselY:
Integrate[-( 2^n + 1z^-n/ Sqrt[π]Gamma[(1/2) - n])(t^2 - 1)^-n - (1/2)Cos[z t], {t, 1, Infinity}, Assumptions -> { Abs[Re[n]] < (1/2)∧z > 0}]Represent using BesselJ and Sin for non-integer
:
FullSimplify[(BesselJ[n, x]Cos[n π] - BesselJ[-n, x]/Sin[n π]), n ≠ 0]BesselY can be represented in terms of MeijerG:
MeijerGReduce[BesselY[n, x], x]Activate[%]BesselY can be represented as a DifferenceRoot:
DifferenceRootReduce[BesselY[k, z], k]Applications (2)
Solve the Bessel differential equation:
DSolve[x ^ 2 f''[x] + x f'[x] + (x ^ 2 - n ^ 2)f[x] == 0, f[x], x]Solve a differential equation:
DSolve[(a + x Cot[x]) y[x] + (x + 2 x^2 Cot[x]) Derivative[1][y][x] + x^2 Derivative[2][y][x] == 0, y[x], x]Solve the inhomogeneous Bessel differential equation:
DSolve[x^2y''[x] + x y'[x] + (x ^ 2 - 1)y[x] == (2/π)x ^ 2, y[x], x]Properties & Relations (3)
Use FullSimplify to simplify Bessel functions:
FullSimplify[ r BesselY[2, r] + r BesselY[0, r]]BesselY can be represented as a DifferentialRoot:
DifferentialRootReduce[BesselY[n, x], x]The exponential generating function for BesselY:
ExponentialGeneratingFunction[BesselY[n, k], n, x]Possible Issues (1)
With numeric arguments, half-integer Bessel functions are not automatically evaluated:
BesselY[11 / 2, 1]For symbolic arguments they are:
BesselY[11 / 2, x]This can lead to major inaccuracies in machine-precision evaluation:
{BesselY[153 / 2, 55.], BesselY[153 / 2, x] /. x -> 55.}Neat Examples (1)
With[{n = 0, ε = 1*^-12}, ParametricPlot3D[Table[{r Cos[φ], r Sin[φ], Im[(-1)^n k(BesselY[n, r Exp[I φ]] + 2I k BesselJ[n, r Exp[I φ]])]}, {k, -2, 2}], {r, ε, 3}, {φ, -π + ε, π - ε}, BoxRatios -> {1, 1, 2.5}, Mesh -> None, PlotStyle -> Directive[Hue[0.46], Opacity[0.6]]]]With[{ν = 1 / 3, ε = 1*^-12}, ParametricPlot3D[Table[{r Cos[φ], r Sin[φ], Im[Exp[-k ν π I] BesselY[ν, r Exp[I φ]] + 2 I Cos[ν π]ChebyshevU[k - 1, Cos[ν π]] BesselJ[ν, r Exp[I φ]]]}, {k, -2, 2}], {r, ε, 3}, {φ, -π + ε, π - ε}, BoxRatios -> {1, 1, 2.5}, Mesh -> None, PlotStyle -> Directive[Hue[0.23], Opacity[0.6]]]]Tech Notes
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), BesselY, Wolfram Language function, https://reference.wolfram.com/language/ref/BesselY.html (updated 2022).
CMS
Wolfram Language. 1988. "BesselY." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2022. https://reference.wolfram.com/language/ref/BesselY.html.
APA
Wolfram Language. (1988). BesselY. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/BesselY.html
BibTeX
@misc{reference.wolfram_2026_bessely, author="Wolfram Research", title="{BesselY}", year="2022", howpublished="\url{https://reference.wolfram.com/language/ref/BesselY.html}", note=[Accessed: 12-June-2026]}
BibLaTeX
@online{reference.wolfram_2026_bessely, organization={Wolfram Research}, title={BesselY}, year={2022}, url={https://reference.wolfram.com/language/ref/BesselY.html}, note=[Accessed: 12-June-2026]}