Inversive Plane

An inversive plane is a class of incidence structure in mathematics.

It may be axiomatised by taking two classes, "points" and "circles" (or "blocks") with the properties

  • any three points lie on exactly one circle;
  • if P and Q are points and c a circle with P on c and Q not, then there is exactly one circle e containing P and Q and intersecting c only in P;
  • there are four points not all on the same circle.

The finite inversive planes are precisely the designs. Such a design is always a Steiner system.

Read more about Inversive Plane:  Ovoids, Derived Designs and Extensions

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