Vertical-Horizontal Full Compatibility of One-Dimensional Subshifts
摘要
We study the notion of full-compatibility: given two one-dimensional subshifts H and V, is there a two-dimensional subshift X such that \({H = \{c_{\mid \mathbb {Z}\times \{0\}} \mid c \in X\}}\) and \({V =\{c_{\mid \{0\}\times \mathbb {Z}} \mid c \in X\}}\) ? We show that this problem is decidable when both X and Y are nearest-neighbor SFTs but undecidable when at least one is allowed to be of slightly higher complexity. We also prove that the problem is undecidable for three nearest-neighbor SFTs combined in a three-dimensional subshift.