ProductLog

ProductLog[z]

gives the principal solution for w in .

ProductLog[k,z]

gives the k^(th) solution.

Details

  • Mathematical function, suitable for both symbolic and numerical manipulation.
  • The solutions are ordered according to their imaginary parts.
  • For , ProductLog[z] is real.
  • ProductLog[z] satisfies the differential equation .
  • For certain special arguments, ProductLog automatically evaluates to exact values.
  • ProductLog can be evaluated to arbitrary numerical precision.
  • ProductLog automatically threads over lists.
  • ProductLog[z] has a branch cut discontinuity in the complex z plane running from to .
  • ProductLog[k,z] allows k to be any integer, with corresponding to the principal solution.
  • ProductLog[k,z] for integer has a branch cut discontinuity from to 0.

Examples

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Basic Examples  (6)

Evaluate numerically:

Plot over a subset of the reals:

Plot over a subset of the complexes:

Series expansion at the origin:

Asymptotic expansions at Infinity:

Asymptotic expansions at a singular point:

Scope  (28)

Numerical Evaluation  (5)

Evaluate numerically:

Evaluate to high precision:

The precision of the output tracks the precision of the input:

Complex number input:

Evaluate efficiently at high precision:

ProductLog threads elementwise over lists and matrices:

Specific Values  (4)

Values of ProductLog at fixed points:

Values at zero:

Values at infinity:

Find a value of x for which the ProductLog[x]=0.5 using Solve:

Visualization  (3)

Plot the ProductLog function:

Plot the real part of :

Plot the imaginary part of :

Polar plot with :

Function Properties  (3)

ProductLog is defined for all real values from the interval [-,):

ProductLog is defined for all complex values:

The real range:

TraditionalForm formatting:

Differentiation  (3)

The first derivative with respect to z:

Higher derivatives with respect to z:

Plot the higher derivatives with respect to z:

Derivative of a nested logarithmic function:

Integration  (3)

Compute the indefinite integral using Integrate:

Verify the anti-derivative:

Definite integral of ProductLog:

More integrals:

Series Expansions  (5)

Find the Taylor expansions using Series:

Plots of the first three approximations around :

Expand the two-argument form:

The general term in the series expansion using SeriesCoefficient:

Find the series expansion at Infinity:

Find series expansions at branch points and branch cuts:

The series expansion at infinity contains nested logarithms:

Function Identities and Simplifications  (2)

ProductLog gives the solution for the following equation:

Expand assuming real variables x and y:

Generalizations & Extensions  (3)

Evaluate numerically on different sheets of the Riemann surface:

Find series expansions at branch points and branch cuts:

The branch points and branch cuts are different for :

Applications  (8)

Plot the real and imaginary parts of ProductLog:

Plot the Riemann surface of ProductLog:

Calculate the limit of :

Compare the exact result with explicit iterations for :

Determine the number of labeled unrooted trees from the generating function:

Solve LotkaVolterra equations:

Find the frequency of the maximum of the blackbody spectrum:

Solve the Haissinski equation:

Equipotential curves of a plate capacitor:

Properties & Relations  (4)

Compositions with the inverse function may need PowerExpand:

Use FullSimplify to simplify expressions containing ProductLog:

Solve a transcendental equation:

Integrals:

Possible Issues  (2)

Generically :

On branch cuts, machineprecision inputs can give numerically wrong answers:

Use arbitraryprecision arithmetic to get correct results:

Neat Examples  (2)

Nested derivatives:

Nested integrals:

Introduced in 1996
 (3.0)