Inflation procedure for a spectre tiling
A generic complete tiling of the plane with spectre tiles can undergo
a so-called inflation procedure that replaces it with a coarser spectre
tiling where clusters of 9 or 8 tiles are replaced respectively by a single
(larger) spectre tile or by a pair forming the so-called mistic shape.
Such inflation procedure can be iterated infinitely many times and for any given
tile of the original tiling we can build the so-called Conway signature,
a characteristic infinite-to-the-left sequence that encodes the structure
of the tiling.
The inflation procedure undergoes 9 stages that are illustrated in the images below
and follows by local properties that any tiling of the plane is forced to possess.
We also created an animation that shows the complete sequence of the various stages
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Start from a generic tiling (*):
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Isolate groups of three tiles that form two partially superposed
mystics pairs.
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The top tile of each group of three is not part of the real mystic
and we drop it:
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Each mystic is surrounded by six tiles that are always organized in the same structure
to form, with the mystic, a cluster named H7.
These are never superposed and some scattered single tiles are left out:
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Each left-out tile can be associated to an adjacent cluster in such a way that it
forms the upper tile of a pair called tower: two adjacent tiles parallel
to each other.
Thus we enrich some of the H7 clusters by adding each of these scattered tiles
and tranform it to an H8 cluster.
Clusters that are not enriched with a new tile are the 'level 1'
"mystic" cluster H7. The remaining are classified as 'level 1'
spectres (H8).
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Now Place a single reflected, slightly larger and suitably oriented spectre tile on top of
each H8 cluster and a mystic pair of tiles on top of each H7 cluster:
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We are left with a sparse set of reflected tiles:
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Finally translate and grow all tiles to form the inflated resulting tiling,
click on image for an animation.
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The last action is a reflection about the x axis in order to obtain
a tiling with the correct orientation:
We can now start over again to obtain the next level of inflation
click on image for an animation.
click on image for an animation.
*) Not really: in order to construct the images we needed to start from the result of a number
of H7-H8 subdivisions (five successive subdivisions corresponding to
the chosen signature "04040.").
Maurizio Paolini