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Theorem

Odd Number Theorem

Mathematical Physics

The odd number theorem is a result in differential topology applied to strong gravitational lensing, stating that a bounded transparent gravitational lens must always produce an odd number of images of a background source. Its rigorous proof rests on Uhlenbeck's Morse theory of null geodesics together with the Poincare-Hopf theorem, which together show why the image count can never come out even.

Facts
Classification
Statement Form
Characterization Theorem 1
Statement
The number of multiple images produced by a bounded transparent lens must be odd. 1
Connections

Has Statement Form

Entity-backed identity for the statement-form enum value this theorem already carries, resolved to a mathematics concept by an explicit value-to-entity map (phase 3 bucket conversion, docs\design_entity_backed_browse_buckets_20260928.md). The statement-form fact itself stays on the theorem unchanged.

In Branch

Source Odd number theorem - Wikipedia
Sources
1. Odd number theorem - Wikipedia
  • Introduction, sentence 1
    the number of multiple images produced by a bounded transparent lens must be odd.
  • In Branch: Differential Topology, Lead sentence
    The odd number theorem is a theorem in differential topology about strong gravitational lensing, which states that the number of m
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