Planes and Designs

Projective and affine planes can be viewed as special kinds of designs. The following functions convert between designs and planes.

Design(P) : Plane -> Dsgn, SetIncPt, SetIncBlk
The design corresponding to the points and lines of the plane P.
FiniteAffinePlane(D) : Inc -> Plane, PlanePtSet, PlaneLnSet
The affine plane corresponding to the incidence structure D.
FiniteProjectivePlane(D) : Inc -> Plane, PlanePtSet, PlaneLnSet
The projective plane corresponding to the incidence structure D.

Example Plane_designs (H150E17)

The development of a Singer difference set provides a design which satisfies the projective plane axioms, and thus can be converted to a projective plane in Magma.
> sds := SingerDifferenceSet(2, 3);
> sds;
{ 0, 1, 3, 9 }
> sdv := Development(sds);
> sdv;
2-(13, 4, 1) Design with 13 blocks
> spp := FiniteProjectivePlane(sdv);
> spp: Maximal;
Projective Plane of order 3
Points: {@ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 @}
Lines:
    {0, 1, 3, 9},
    {1, 2, 4, 10},
    {2, 3, 5, 11},
    {3, 4, 6, 12},
    {0, 4, 5, 7},
    {1, 5, 6, 8},
    {2, 6, 7, 9},
    {3, 7, 8, 10},
    {4, 8, 9, 11},
    {5, 9, 10, 12},
    {0, 6, 10, 11},
    {1, 7, 11, 12},
    {0, 2, 8, 12}
> Universe(Support(spp));
Residue class ring of integers modulo 13
V2.28, 13 July 2023