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SolvedTopologyMillennium Prize Problem

Poincaré conjecture

Every simply connected, closed 3-manifold is a 3-sphere. Proved by Perelman.

Exact statement

M3 closed, π1(M)=1 ⟹ M≅S3M^{3}\ \text{closed},\ \pi_1(M)=1\ \Longrightarrow\ M\cong S^{3}
∂gij∂t=−2Rij(Ricci flow)\frac{\partial g_{ij}}{\partial t}=-2R_{ij}\quad(\text{Ricci flow})

Every simply connected, closed (compact, without boundary) three-dimensional manifold is homeomorphic to the three-sphere.

Status

Solved by Grigori Perelman (2002–2003) using Richard Hamilton's Ricci flow; the only Millennium Problem solved so far.

Posed: 1904, Henri Poincaré.

Millennium Prize awarded to Grigori Perelman on 18 March 2010; he declined it (and the 2006 Fields Medal).

In plain words

Imagine a loop of string on a surface. If every loop can be shrunk to a point without leaving the surface, the surface is a sphere. Poincaré asked whether the same is true one dimension up: is a closed 3-dimensional space in which every loop shrinks necessarily the 3-sphere?

Perelman proved it by running Hamilton's Ricci flow, which smooths a metric the way heat smooths temperature, cutting out developing singularities ('surgery') and showing the process ends in round pieces. He proved Thurston's more general geometrization conjecture along the way.

How it was solved

  1. 1961: Smale proves the analogue in dimensions 5 and higher.
  2. 1982: Freedman proves dimension 4; Hamilton introduces Ricci flow.
  3. 2002–2003: Perelman posts three papers on arXiv completing the proof (and geometrization).
  4. 2006: Detailed expositions by Kleiner–Lott, Morgan–Tian and Cao–Zhu confirm the proof; Perelman declines the Fields Medal.
  5. 2010: The Clay Mathematics Institute awards the Millennium Prize; Perelman declines it.

What our solver can and cannot do

The Poincaré conjecture is settled, so the solver shows the result and its history. It can check concrete examples, but the full proof lives in the references below. Open the solver.

Frequently asked questions

What does the Poincaré conjecture say?
Every simply connected, closed (compact, without boundary) three-dimensional manifold is homeomorphic to the three-sphere.
Has the Poincaré conjecture been solved?
Solved by Grigori Perelman (2002–2003) using Richard Hamilton's Ricci flow; the only Millennium Problem solved so far.
Is there a prize?
Millennium Prize awarded to Grigori Perelman on 18 March 2010; he declined it (and the 2006 Fields Medal).
Can MathGPT solve the Poincaré conjecture?
MathGPT shows the statement, who settled it and how, with references; the proof itself is in the cited papers.

References

  • G. Perelman, arXiv:math/0211159, arXiv:math/0303109, arXiv:math/0307245.
  • J. Morgan and G. Tian, Ricci Flow and the Poincaré Conjecture, AMS/Clay (2007).
  • R. Hamilton, 'Three-manifolds with positive Ricci curvature', J. Differential Geom. 17 (1982).