Turing machines will exist in even very simple universes, because they are very simple. Instead physicists usually use complexity theory to analyze any proposed

Turing machines will exist in even very simple universes, because they are very simple. Instead physicists usually use complexity theory to analyze any proposed new universe or a theory for our universe. If for example, the new theory ensures P=NP, then is suspect. There is a lot of work done on this, but I don't know a good reference off the top of my head. However, sometimes, people do think about Turing Machines. Here is one paper by Scott Aaronson http://www.scottaaronson.com/papers/ctchalt.pdf http://www.scottaaronson.com/papers/ctchalt.pdf