These were posted on another list based on going discussions of Loop Quantum
gravity theory. They may perhaps be of interest here. This is pretty
current.
One of the main failures of Loop Quantum gravity was its inability to
recover low energy physics and in particular incorporate the graviton propagator in
its formulation. However, if the papers linked below are correct LQG has
passed this hurdle which is a significant milestone. I am reminded of Susskind's
remarks which were in my view were, full of the usual stringy hubris against
the loopy guys. ( and gals) According to Susskind, String theory is the
only show in town. But string theory is not background independent which means
it fails to
provide a model which unifies with GR at the small scale. Now that LQG has a
model with a graviton propagator the game may have changed.
Hey has anyone noticed that this topological charge structure might be dual
to 6D compact CY momentum-charge structure. 3 Tweedle charges and 3 braid
charges. Interesting.
Also Markopoulou and Kribs have been able to demonstrate how these
topological structures persist in spite of the Quantum chaos at the Planck scale. This
result is available in an eprint linked below. They have modeled these
topological charges as being stored in space time as qubits which are resilient
enough to persist as particles.
Bob Zannelli
We show that a class of background independent models of quantum spacetime
have local excitations that can be mapped to the first generation fermions of
the standard model of particle physics. These states propagate coherently as
they can be shown to be noiseless subsystems of the microscopic quantum
dynamics. These are identified in terms of certain patterns of braiding of graphs,
thus giving a quantum gravitational foundation for the topological preon
model proposed by one of us.
These results apply to a large class of theories in which the Hilbert space
has a basis of states given by ribbon graphs embedded in a three-dimensional
manifold up to diffeomorphisms, and the dynamics is given by local moves on
the graphs, such as arise in the representation theory of quantum groups. For
such models, matter appears to be already included in the microscopic
kinematics and dynamics.