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Computer-Assisted Proofs

1976 CE20th-century United States (Appel and Haken)

Concept

When the proof is too long for humans — the new mathematical methodology.

Understand it in one breath

"Reduce a theorem exhaustively to finitely many cases, then use a computer to verify every case." This differs from checking many examples. The 1976 Four Color Theorem, the 2014 Flyspeck formal verification of the Kepler conjecture, and the 2016 Boolean Pythagorean Triples result are prominent examples. Trust depends on the completeness of the reduction and on independently checking the program or proof certificate.

At a glance

Year

Theorem

Role of the computer

Scale

1976

Four Color Theorem

Checked a finite unavoidable set of configurations by program

Large-scale computation for its time

1996

Robbins conjecture (Boolean algebra)

EQP automated prover (McCune)

8 days of automated search

1998

Kepler conjecture (sphere packing)

5,000 inequalities + LP

Hales 1998 → Flyspeck 2014

2014

Flyspeck (Hales verification)

Fully formal verification in Coq + HOL Light

Years of collaboration

2016

Boolean Pythagorean triples

SAT solver

About 200 terabytes of data generated during the computation

2021+

Lean and the Mathlib ecosystem

Collaborative formalization of theorems and libraries

Many collaborations, including formalization of the PFR theorem

Trust in a computer-assisted proof depends less on a computer/no-computer divide than on complete reduction, inspectable code or certificates, independent rechecking, and a clearly identified small trusted base.

Key formula

complete finite reduction+verification of every casetheorem\text{complete finite reduction} + \text{verification of every case} \Longrightarrow \text{theorem}

Key moments

1976 CE

The Four Color Theorem — a landmark computer-assisted proof

Appel and Haken combined a finite reduction with extensive computer checking. The result made the inspectability of computer-dependent proofs a central question.

1998 CE

The Kepler conjecture

Thomas Hales proved that no arrangement of equal spheres is denser than the familiar close-packed arrangements. Checking the proof required years of computer work.

2016 CE

Boolean Pythagorean triples — 200 terabytes

Marijn Heule, Oliver Kullmann, and Victor Marek produced an enormous computer-assisted proof with a 200-terabyte certificate — far beyond what a human could read line by line.

2024 CE

Proof assistants such as Lean

Proof assistants such as Lean, Coq, and Isabelle let computers check formal proofs down to their logical foundations, and their combination with AI is opening a new era.

Modern applications

The Four Color Theorem, the Kepler conjecture, Boolean Pythagorean triples, large-scale checks of Riemann zeros, and formal verification of critical systems.

Beyond MathVoyage

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