Posted: Sep 22, 2013 3:02 pm
iamthereforeithink wrote:twistor59 wrote:iamthereforeithink wrote:To me, it makes sense that space and time are emergent, rather than fundamental. It saves us from having to answer questions like "When did time begin?".
As far as I know (i.e. not very far!), in these holographic boundary theories, to date it's only spatial dimensions which they've been able to make emerge, not temporal ones.
Yes (AFAIK), but time seems to be entirely absent from these models. I'm not sure what that means.
Nima's mantra is "spacetime is doomed". I think that just means he wants to formulate physics in a new set of variables in which spacetime doesn't appear. A bit like Roger Penrose's aim to formulate all of physics in twistor space. You can relate the end results back to spacetime by doing a certain transform, but all the calculations are done elsewhere, and the gain from doing this is that the calculations are easier!
iamthereforeithink wrote:
I'm also not completely clear about the implications of this particular geometric object. Apparently, it also does away with the need for virtual particles and "unitarity". How does it do that? When they say it does away with unitarity, do they mean that the probabilities don't sum up to one, or that probabilities are not needed at all?
I would imagine they mean that unitarity is "not manifest". i.e. if you look at the formalism, it's not obvious that all the probabilities add up to one. But if you looked harder and did lots of convoluted calculations, you'd find that unitarity was indeed respected.