Finite Geometry Notes

The historical road from the Platonic solids to the finite simple groups is well known. This website sketches, in accordance with Thompson's hope expressed above, a road less traveled. This road begins more than 24 centuries ago, with Plato's diamond figure [PL, also HE]. It leads, through the study of symmetry, to the powerful combinatorial structure S(5,8,24) [MA, also CA] used in studies of finite simple groups [TH, also CO] and also in a recent attack [DH] on the fourcolor conjecture.
In 1975, the author discovered symmetry properties of Plato's diamond that he described in a preprint [CUL1] distributed at the 1976 American Mathematical Society summer meeting in Toronto. This later resulted in the following citation:
"In every civilization and culture, colored tilings and
patterns appear among the earliest decorations.... In
particular, 2color patterns arose  early and
frequently  through a device known as
'counterchange'.... An early paper with remarkable
counterchange designs formed by diagonally divided
squares  onehalf black, onehalf white  was
published by Truchet (1704). For a more recent treatment,
with many illustrations, see Cullinane (1976). However,
all these were more or less 'accidental' occurrences,
independently reinvented many times, and passed from
generation to generation by artists and artisans. The
only artist who deliberately and consistently tried to
investigate colored patterns (more specifically, colored
tilings) was M. C. Escher...."
 Branko Grunbaum and G. C. Shephard [GR, 1987]
Compare these words with those of G. H. Hardy:
"A mathematician, like a painter or a poet, is a maker of patterns." [HA]
Compare also the quotations in the website A Mathematician's Aesthetics. [CUL4]
Later, in 1978, the author came across the following:
"...A guiding principle in modern mathematics is this
lesson: Whenever you have to do with a
structureendowed entity S [capital sigma in the
original] try to determine its group of
automorphisms, the group of those elementwise
transformations which leave all structural relations
undisturbed. You can expect to gain a deep insight into
the constitution of S in this way."
Hermann Weyl [WE, p. 144]
Inspired by Weyl's lesson, the author determined in 1978 the group of automorphisms of the patterns described in the preprint [CUL1, updated in CUL3], and published this information in an abstract [CUL2, February 1979]. In March 1979, R. T. Curtis sent the author a copy of his paper [CUR]. This paper describes the action of the Mathieu group M_{24} on the Steiner system S=S(5,8,24). Part of this group action is identical to the action described in the abstract [CUL2]. Thus a trail may be traced from Plato's diamond in the Meno dialogue, via S, to recent studies of finite simple groups. For more on the relation of these studies to S, see (for instance) Feit [FE], who notes that the Leech lattice underlying various new sporadic groups "is a blown up version of S(5,8,24)."
Also discussed at the 1976 A.M.S. meeting in Toronto was an attempted computer proof of the fourcolor conjecture. For a recent human proof attempt, see Dharwadker's website [DH]. This new attack (as yet unrefereed) on the fourcolor conjecture uses the same Steiner system S discussed above. The road that led to Dharwadker's use of S is a story yet to be told.
For the author's rough critique (as of November 28, 2000) of Dharwadker's proof attempt, click here.
For other critiques, enter Dharwadker as the search term after you have clicked here.
Page last updated Nov. 30, 2000; created Nov. 19, 2000.