Given a tile ("7" or "8") of a tiling, its Conway signature is an infinite-to-the-left sequence of symbols taken in {0,1,2,3,4,5,6}
that records the subdivision history that originated it.
Most recent subdivision history is recorded to the right, in particular the last symbol of the signature is 0 iff the are focusing on
a tile "7".
The meaning of the symbols is clarified in the image on the left showing the subdivision process for a tile "8". In a signature we do not allow for the consecutive pair of symbols ...06... The notation "[w]p." denotes the periodic signature "...wwwwp." where w is any nonempty finite sequence of symbols and p is a possibly empty finite sequence of symbols. A tile is part of an infinite worm if and only if its signature contains only symbols in {0,2,6}; An infinite worm is described as a bi-infinite sequence of tiles "8" and "7" conventionally oriented as illustrated. |