The Weierstrass Representation

Building minimal surfaces from complex analysis — the (g, η) construction

The Weierstrass Representation

The Weierstrass representation is a remarkable bridge between complex analysis and differential geometry. It shows that every minimal surface can be constructed from a pair of complex-analytic data: a meromorphic function g (the stereographic Gauss map) and a holomorphic 1-form η.

This construction is extraordinarily powerful: by choosing different (g, η) pairs, you can generate every known minimal surface — and discover new ones.

Interactive: Weierstrass Builder

Select a Weierstrass data preset to see the corresponding minimal surface alongside the domain coloring of its Gauss map g(z). The hue encodes the argument of g(z), and the brightness encodes its modulus.

Minimal Surface (Catenoid)
Gauss Map: g(z) = eᶻ
g(z):g(z) = eᶻη:η = e⁻ᶻ dz

The Representation Formula

Given a meromorphic function g and a holomorphic 1-form η = f(z)dz, the minimal surface is:

X₁ = Re ∫ (1 - g²) η

X₂ = Re ∫ i(1 + g²) η

X₃ = Re ∫ 2g η

Interactive: Gauss Map Visualizer

The orange dot traces a point on the Enneper surface (left) and its corresponding unit normal on the Gauss map sphere (right). The function g in the Weierstrass representation is exactly the stereographic projection of this normal — a deep connection between complex analysis and geometry.

Enneper Surface
Gauss Map (Unit Sphere)
Point on surface → its unit normal on the Gauss map sphere

Interactive: Associate Family

Multiplying η by e^(iθ) rotates through the associate family — a continuous family of isometric minimal surfaces. The most famous example morphs the catenoid (θ = 0) into the helicoid (θ = π/2).

Key Takeaways

  • Weierstrass data: A pair (g, η) of complex-analytic objects determines a minimal surface.
  • g = Gauss map: The meromorphic function is the stereographic projection of the unit normal.
  • Associate family: Rotating η by e^(iθ) gives isometric deformations (catenoid ↔ helicoid).
  • Universal construction: Every simply connected minimal surface has a Weierstrass representation.