Math 2.0

Special functions Object

Weierstrass elliptic function

Builds on Elliptic functionMeromorphic functionPole

Description

Let ω1,ω2∈ℂ\omega_1, \omega_2 \in \C be linearly independent over ℝ\R, and let Λ=ℤω1+ℤω2\Lambda = \Z\omega_1 + \Z\omega_2 be the lattice they span. The Weierstrass elliptic function of Λ\Lambda is ℘(z)=1z2+∑ω∈Λ∖{0}(1(z−ω)2−1ω2),z∈ℂ∖Λ.\wp(z) = \frac{1}{z^2} + \sum_{\omega \in \Lambda \setminus \set{0}} \left( \frac{1}{(z - \omega)^2} - \frac{1}{\omega^2} \right), \qquad z \in \C \setminus \Lambda. The series converges absolutely and uniformly on compact subsets of ℂ∖Λ\C \setminus \Lambda, because ∑ω≠0∣ω∣−3<∞\sum_{\omega \ne 0} \abs{\omega}^{-3} < \infty.

  1. ℘\wp is a meromorphic function on ℂ\C whose poles are exactly the points of Λ\Lambda, each a pole of order 22.
  2. ℘\wp is even, and ℘(z+ω)=℘(z)\wp(z + \omega) = \wp(z) for all ω∈Λ\omega \in \Lambda, so ℘\wp is an elliptic function for Λ\Lambda.
  3. ℘\wp satisfies the differential equation (℘′)2=4℘3−g2℘−g3(\wp')^2 = 4\wp^3 - g_2 \wp - g_3, where g2=60∑ω≠0ω−4g_2 = 60 \sum_{\omega \ne 0} \omega^{-4} and g3=140∑ω≠0ω−6g_3 = 140 \sum_{\omega \ne 0} \omega^{-6}.

Remarks

Periodicity is checked on the derivative first: ℘′(z)=−2∑ω∈Λ(z−ω)−3\wp'(z) = -2 \sum_{\omega \in \Lambda} (z - \omega)^{-3} is visibly Λ\Lambda-periodic. So ℘(z+ω1)−℘(z)\wp(z + \omega_1) - \wp(z) is a constant cc; putting z=−ω1/2z = -\omega_1/2 and using that ℘\wp is even gives c=0c = 0. The differential equation follows because (℘′)2−4℘3+g2℘+g3(\wp')^2 - 4\wp^3 + g_2\wp + g_3 is elliptic without poles, hence constant, and its Laurent expansion at 00 shows the constant is 00. Every elliptic function for Λ\Lambda is a rational function of ℘\wp and ℘′\wp'. The map z↦(℘(z),℘′(z))z \mapsto (\wp(z), \wp'(z)) identifies the torus ℂ/Λ\C / \Lambda minus one point with the affine cubic curve y2=4x3−g2x−g3y^2 = 4x^3 - g_2 x - g_3.

Reading path

To understand this page from the ground up, read these 16 pages in order. The foundations come first.

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Each page uses the pages above it. The colour of the bar on a box shows how strong the evidence is, and the box also gives it as text. The list has the same pages.
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  1. Complex numbers object
  2. Elliptic function concept
  3. Real numbers object
  4. Set bounded above definition
  5. Real and imaginary parts definition
  6. Supremum definition
  7. Completeness axiom statement
  8. Existence of square roots of nonnegative reals statement
  9. Square root definition
  10. Modulus of a complex number definition
  11. Complex differentiability definition
  12. Holomorphic function definition
  13. Isolated singularity definition
  14. Pole definition
  15. Meromorphic function definition
  16. Weierstrass elliptic function object

Further reading

  1. Web https://en.wikipedia.org/wiki/Weierstrass_elliptic_function
About this page
Tag361NAK68QK
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Kindobject
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MSC33E05, 30D30
Instance ofElliptic function
UsesElliptic function, Meromorphic function, Pole
Same as
Changed2 November 2026

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