crystal
Part II, One Graph, Four Covers · defined in Chapter VIII, Space as a Tally
The three-dimensional net of tallies, Sunada’s crystal, which the program reads as space.
Walks from a fixed report with the same endpoint and the same tally are exactly the vertices of the maximal abelian cover of , with periods . Realized by the harmonic projection, the only report-covariant linear map from oriented letters to periods, the cover is trivalent, three-dimensional, of girth ten, strongly isotropic and chiral. Its periods carry the report group as , so all twenty-four report permutations act as proper rotations, and edges along complementary letters are perpendicular, not opposite as the older dictionary of letters as directions assumed.
On the report qubit’s Minkowski space each letter generates a boost between its two reports, and the periods are exactly the tallies that generate rotations: the crystal’s metric is the norm of the observer’s rotation algebra. Read modulo 2 that metric is the Fano plane with a marked point, a clock; modulo 3 it picks out the four report axes, turned by the rotation group of a cube; modulo 7 its null directions are the eight points of the sky. That the crystal is physical space is a reading, and it costs one added clause, that the circulation of the observer’s live path of report changes is retained, which changes a finite statistic already at fourth order in time.
Among three-dimensional crystal nets with injective standard realization, the strongly isotropic ones are the diamond crystal and the crystal, the latter together with its mirror image. The crystal is chiral: it is not carried to its mirror image by any orientation-preserving isometry.
As mathematics
The maximal abelian cover of , with deck group , in its standard realization: each oriented letter is projected onto the circulation space by . Every edge has squared length , the three edges at a site meet at in a plane, and the periods are the integer triples with coordinates of equal parity. Sunada showed that among three-dimensional crystal nets with injective standard realization the strongly isotropic ones are the diamond and the crystal, the latter with its mirror image.
It has girth 10. Its decagons fall into six classes and include the cyclic reductions of the commutators of the triangle loops, and on the tori , , they span the cycle space. The dilation by about a vertex maps vertices to vertices exactly when or , since the vertex classes are points of order 4 in the Jacobian of .
| Its name in another field | Bridge |
|---|---|
| Sunada’s crystal | built |
| the srs net | built |
| the Laves graph | built |
| Wells’s -a | built |
| the hyperoctagon lattice of Kitaev models | classical |
| space | a reading |
- Built from
- tallykernel graph
- Builds
- arena