Veblen-Wedderburn system
A Veblen-Wedderburn system is an algebraic system over a set with two binary operations (called addition) and (called multiplication) on such that
- 1.
there is a , and that is an abelian group
under , with the additive identity
- 2.
, together with , is a loop (we denote as its identity element
)
- 3.
is right distributive
over ; that is,
- 4.
if , then the equation has a unique solution in
A Veblen-Wedderburn system is also called a quasifield.
Usually, we write instead of .
For any , by defining a ternary operation on , given by
it is not hard to see that is a ternary ring. In fact, it is a linear ternary ring because and .
For example, any field, or more generally, any division ring, associative or not, is Veblen-Wedderburn. An example of a Veblen-Wedderburn system that is not a division ring is the Hall quasifield.
A well-known fact about Veblen-Wedderburn systems is that, the projective plane of a Veblen-Wedderburn system is a translation plane, and, conversely, every translation plane can be coordinatized by a Veblen-Wedderburn system. This is the reason why a translation plane is also called a Veblen-Wedderburn plane.
Remark. Let be a Veblen-Wedderburn system. If the multiplication , in addition to be right distributive over , is also left distributive over , then is a semifield. If , on the other hand, is associative, then is an abelian nearfield (a nearfield such that is commutative).
References
- 1 R. Casse, Projective Geometry, An Introduction, Oxford University Press (2006)