A Physically Universal Turing Machine
arXiv:2003.10328
Abstract
We construct a two-dimensional Turing machine that is physically universal in both the moving tape and moving head model. In particular, it is mixing of all finite orders in both models. We also provide a variant that is physically universal in the moving tape model, but not in the moving head model.
45 pages plus 6 pages of appendices, 17 figures