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Recently (25 July) Lee Smolin posted an update of his December 2007 unification paper
http://arxiv.org/abs/0712.0977
The Plebanski action extended to a unification of gravity and Yang-Mills theory
"We study a unification of gravity with Yang-Mills fields based on a simple extension of the Plebanski action to a Lie group G... [which] may be applied to Lisi’s proposal of an E8 unified theory, giving a fully E8 invariant action. The extended form of the Plebanski action suggests a new class of spin foam models."
The persistent intuition that keeps creeping back into consciousness here is the idea of non-local links in a spin network.
This is something that other QG approaches either do not have or have not yet exploited. It is worth keeping an eye on IMO. All the more because Smolin indicates there is a followup paper in the works, with Garrett Lisi and Simone Speziale. In my estimation, the implied prospect, if it materializes, would be solid contribution to Physical Review D putting this unification scheme (with its nonlocal links) on the map.
On the face of it, nonlocal links is a very strange notion. That a spin network can describe the world and that in ancient days the network was disorderly with connections every which way----not like a regular 3D lattice. With the passage of time the network smoothed itself out somewhat and evolved into a more regular configuration giving the semiclassical illusion of the 3D space we know and love. But there persisted this RESIDUE of long-range connections. Some pairs of nodes that were paradoxically both near and far.
To a local observer who cannot see the other end, these look like severed links----culdesacs---singletons---unmatched socks.
This strikes me as being of the nature of a just-so-story creation myth or better a creation HUNCH.
Because, O ye of insatiable curiosity, the unmatched socks are matter. They are what scholars call FERMIONS.
http://arxiv.org/abs/0712.0977
The Plebanski action extended to a unification of gravity and Yang-Mills theory
"We study a unification of gravity with Yang-Mills fields based on a simple extension of the Plebanski action to a Lie group G... [which] may be applied to Lisi’s proposal of an E8 unified theory, giving a fully E8 invariant action. The extended form of the Plebanski action suggests a new class of spin foam models."
The persistent intuition that keeps creeping back into consciousness here is the idea of non-local links in a spin network.
This is something that other QG approaches either do not have or have not yet exploited. It is worth keeping an eye on IMO. All the more because Smolin indicates there is a followup paper in the works, with Garrett Lisi and Simone Speziale. In my estimation, the implied prospect, if it materializes, would be solid contribution to Physical Review D putting this unification scheme (with its nonlocal links) on the map.
On the face of it, nonlocal links is a very strange notion. That a spin network can describe the world and that in ancient days the network was disorderly with connections every which way----not like a regular 3D lattice. With the passage of time the network smoothed itself out somewhat and evolved into a more regular configuration giving the semiclassical illusion of the 3D space we know and love. But there persisted this RESIDUE of long-range connections. Some pairs of nodes that were paradoxically both near and far.
To a local observer who cannot see the other end, these look like severed links----culdesacs---singletons---unmatched socks.
This strikes me as being of the nature of a just-so-story creation myth or better a creation HUNCH.
Because, O ye of insatiable curiosity, the unmatched socks are matter. They are what scholars call FERMIONS.