Hi Saibal, Your thesis is very interesting, as far as I understand it. I am sure you are right about the fact that renormalisation theory can put light ... on the question "what is a physical system and what is a physical simulation of a physical system?".
I see more and more my own Z1* as a sort of renormalisation on the computationalist indeterminacy (*Too* many worlds with comp). The quantum would be the result of renormalising classical comp indeterminacy! Do you know the Hopf algebra of renormalisation? (cf the Connes and Kreimer "Lessons from Quantum Field Theory"? (hep-th/9904044). My interest for Hopf algebra grew from the reading of the the Kitaev "fault-tolerant quantum computation by anyons" (quant-ph/9707021) (what crazy paper!), but your remark + your thesis + Connes and Kreimer adds still deeper motivations. BTW you said (to the FOR list): >In quantum field theory Feynman diagrams are used to perform perturbative >computations. Now, here it is clear from the start that virtual particles >and ghosts, as they appear in these diagrams, don't exist. Only the >external lines represent real physical particles. What makes you so sure? I guess it's my incompetence in Quantum Field Theory, but this is not clear for me. I would appreciate a short comment on the MWI view of QFT, perturbation and renormalisation. >All this is very clear >because the Feynman rules are derived from a well defined theory that is >well understood. Ah ? Bruno