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单词 VeblenWedderburnSystem
释义

Veblen-Wedderburn system


A Veblen-Wedderburn system is an algebraic system over a set R with two binary operationsMathworldPlanetmath + (called addition) and (called multiplication) on R such that

  1. 1.

    there is a 0R, and that R is an abelian groupMathworldPlanetmath under +, with 0 the additive identity

  2. 2.

    R-{0}, together with , is a loop (we denote 1 as its identity elementMathworldPlanetmath)

  3. 3.

    is right distributivePlanetmathPlanetmath over +; that is, (a+b)c=ac+bc

  4. 4.

    if ab, then the equation xa=xb+c has a unique solution in x

A Veblen-Wedderburn system is also called a quasifield.

Usually, we write ab instead of ab.

For any a,b,cR, by defining a ternary operation * on R, given by

a*b*c:=ab+c,

it is not hard to see that (R,*,0,1) is a ternary ring. In fact, it is a linear ternary ring because ab=a*b*0 and a+c=a*1*c.

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 planeMathworldPlanetmath 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 R be a Veblen-Wedderburn system. If the multiplication , in addition to be right distributive over +, is also left distributive over +, then R is a semifield. If , on the other hand, is associative, then R is an abelian nearfield (a nearfield such that + is commutativePlanetmathPlanetmath).

References

  • 1 R. Casse, Projective Geometry, An Introduction, Oxford University Press (2006)

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更新时间:2025/5/4 15:40:00