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Roberto Percacci had comment on emergence at Woit's blog in reply to this by "H.M."
http://www.math.columbia.edu/~woit/wordpress/?p=3123&cpage=1#comment-61076
H.M.:"...You have to understand the difference between emergence and reductionism. The prevalent idea in high energy physics is that everything (up to a limit) can be split apart and reduced into more and more fundamental particles (or strings). For example the proton is build out of three quarks, which again might be build out of more fundamental things.
The idea of emergence is VERY different. If a particle is not fundamental it is not necessarily build out of smaller particles, it can be a COLLECTIVE degree of freedom. There are many examples of collective phenomena in physics (specially pioneered in Condensed Matter Physics), and these “particles” cannot be described in a reductionist way. Quantum solid and liquids, are microscopically non-relativistic and build out of many-particles interacting with EM. But they can have low energy degrees of freedom which are much more symmetric, ie have Lorentz invariance and emergent non-Abelian gauge bosons.
Thus the answer to your question is that; what emergent models can offer is to describe emergent phenomena! IF gauge symmetries and gravity are not fundamental, but emergent collective degrees of freedom, they cannot be described by, say, strings. Wither the content of the standard model is fundamental or emergent is not known (though most people tend to prefer non-emergence)."
Percacci:"Quoting H M:
> what emergent models can offer is to describe emergent phenomena!
Yes, that would be useful, but much of the literature does not address the issue of constructing workable emergent models for gravity. It seems to me that those that go furthest in this direction are people that do not usually talk much about emergence. For instance, you could argue that causal dynamical triangulations is currently the most successful way of actually calculating emergent properties of gravity."
http://www.math.columbia.edu/~woit/wordpress/?p=3123&cpage=1#comment-61101
You could also argue that LQG is that, currently. IOW that the emergent properties of gravity are collective degrees of freedom arising from the evolution of nodes (as described in the spin-network picture)
http://www.math.columbia.edu/~woit/wordpress/?p=3123&cpage=1#comment-61076
H.M.:"...You have to understand the difference between emergence and reductionism. The prevalent idea in high energy physics is that everything (up to a limit) can be split apart and reduced into more and more fundamental particles (or strings). For example the proton is build out of three quarks, which again might be build out of more fundamental things.
The idea of emergence is VERY different. If a particle is not fundamental it is not necessarily build out of smaller particles, it can be a COLLECTIVE degree of freedom. There are many examples of collective phenomena in physics (specially pioneered in Condensed Matter Physics), and these “particles” cannot be described in a reductionist way. Quantum solid and liquids, are microscopically non-relativistic and build out of many-particles interacting with EM. But they can have low energy degrees of freedom which are much more symmetric, ie have Lorentz invariance and emergent non-Abelian gauge bosons.
Thus the answer to your question is that; what emergent models can offer is to describe emergent phenomena! IF gauge symmetries and gravity are not fundamental, but emergent collective degrees of freedom, they cannot be described by, say, strings. Wither the content of the standard model is fundamental or emergent is not known (though most people tend to prefer non-emergence)."
Percacci:"Quoting H M:
> what emergent models can offer is to describe emergent phenomena!
Yes, that would be useful, but much of the literature does not address the issue of constructing workable emergent models for gravity. It seems to me that those that go furthest in this direction are people that do not usually talk much about emergence. For instance, you could argue that causal dynamical triangulations is currently the most successful way of actually calculating emergent properties of gravity."
http://www.math.columbia.edu/~woit/wordpress/?p=3123&cpage=1#comment-61101
You could also argue that LQG is that, currently. IOW that the emergent properties of gravity are collective degrees of freedom arising from the evolution of nodes (as described in the spin-network picture)