Famous Examples
Desargues' theorem holds in a projective plane P if and only if P is the projective plane over some division ring D—. The projective plane is then called desarguesian. A theorem of Amitsur and Bergman states that, in the context of desarguesian projective planes, for every intersection theorem there is a rational identity such that the plane P satisfies the intersection theorem if and only if the division ring D satisfies the rational identity.
- Pappus's hexagon theorem holds in a desarguesian projective plane if and only if D is a field; it corresponds to the identity .
- Fano's theorem (which states a certain intersection does not happen) holds in if and only if D has characteristic ; it corresponds to the identity a+a=0.
Read more about this topic: Intersection Theorem
Famous quotes containing the words famous and/or examples:
“Martyrdom ... is the only way in which a man can become famous without ability.”
—George Bernard Shaw (1856–1950)
“In the examples that I here bring in of what I have [read], heard, done or said, I have refrained from daring to alter even the smallest and most indifferent circumstances. My conscience falsifies not an iota; for my knowledge I cannot answer.”
—Michel de Montaigne (1533–1592)