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Would a successful merger of LQG + NCG SM be considered a TOE? 
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#1
May2510, 01:39 AM

P: 716

LQG is an attempt to quantize geometry
Noncommutative geometry is an attempt to express the SM geometrically, and is able to derive the SM Lagrangian and prediction of Higgs mass. LQG is not a TOE since it does not include SM, only quantize gravity, and NCG is not a TOE since it does not include a quantum theory of gravity. There have been a variety of papers by Aastrup, Marcolli, etc., to merge NCG with LQG, to peserve the NCG spectral triples and hence SM lagrangians and quantized geometry. LQG and NCG are both "geometrical", neither is a TOE. Would the merger of LQG with NCG be considered a TOE, and if so, how does it contrast/compare with string theory and GUT's as TOE? Perhaps Loop Quantum Gravity + Noncommutative geometry should be called Loop Quantum GEOMETRY or Noncommutative Loop Geometry. I'm surprised that thus far this project has very limited traction. references: http://arxiv.org/pdf/1005.1057 http://arxiv.org/abs/1005.1057 Spin Foams and Noncommutative Geometry Domenic Denicola (Caltech), Matilde Marcolli (Caltech), Ahmad Zainy alYasry (ICTP) 48 pages, 30 figures (Submitted on 6 May 2010) "We extend the formalism of embedded spin networks and spin foams to include topological data that encode the underlying threemanifold or fourmanifold as a branched cover. These data are expressed as monodromies, in a way similar to the encoding of the gravitational field via holonomies. We then describe convolution algebras of spin networks and spin foams, based on the different ways in which the same topology can be realized as a branched covering via covering moves, and on possible composition operations on spin foams. We illustrate the case of the groupoid algebra of the equivalence relation determined by covering moves and a 2semigroupoid algebra arising from a 2category of spin foams with composition operations corresponding to a fibered product of the branched coverings and the gluing of cobordisms. The spin foam amplitudes then give rise to dynamical flows on these algebras, and the existence of low temperature equilibrium states of Gibbs form is related to questions on the existence of topological invariants of embedded graphs and embedded twocomplexes with given properties. We end by sketching a possible approach to combining the spin network and spin foam formalism with matter within the framework of spectral triples in noncommutative geometry." http://arxiv.org/abs/0907.5510 On SemiClassical States of Quantum Gravity and Noncommutative Geometry Authors: Johannes Aastrup, Jesper M. Grimstrup, Mario Paschke, Ryszard Nest (Submitted on 31 Jul 2009) Abstract: We construct normalizable, semiclassical states for the previously proposed model of quantum gravity which is formulated as a spectral triple over holonomy loops. The semiclassical limit of the spectral triple gives the Dirac Hamiltonian in 3+1 dimensions. Also, timeindependent lapse and shift fields emerge from the semiclassical states. Our analysis shows that the model might contain fermionic matter degrees of freedom. The semiclassical analysis presented in this paper does away with most of the ambiguities found in the initial semifinite spectral triple construction. The cubic lattices play the role of a coordinate system and a divergent sequence of free parameters found in the Dirac type operator is identified as a certain inverse infinitesimal volume element. Intersecting Connes Noncommutative Geometry with Quantum Gravity Authors: Johannes Aastrup, Jesper M. Grimstrup (Submitted on 18 Jan 2006) Abstract: An intersection of Noncommutative Geometry and Loop Quantum Gravity is proposed. Alain Connes' Noncommutative Geometry provides a framework in which the Standard Model of particle physics coupled to general relativity is formulated as a unified, gravitational theory. However, to this day no quantization procedure compatible with this framework is known. In this paper we consider the noncommutative algebra of holonomy loops on a functional space of certain spinconnections. The construction of a spectral triple is outlined and ideas on interpretation and classical limit are presented. 


#2
May2510, 02:11 AM

P: 407

Thus, there are good reasons why by far the majority of professional particle physicists do not follow this route, but rather something that the armchair scientists over here don't like. 


#3
May2810, 10:37 PM

P: 716

Since in order for LQG to be a serious candidate of physics, it needs to incorporate SMQFT matter. The papers are to this effect, are there any reasons why this approach is not sound? http://arxiv.org/abs/0907.5510 On SemiClassical States of Quantum Gravity and Noncommutative Geometry Authors: Johannes Aastrup, Jesper M. Grimstrup, Mario Paschke, Ryszard Nest (Submitted on 31 Jul 2009) Abstract: We construct normalizable, semiclassical states for the previously proposed model of quantum gravity which is formulated as a spectral triple over holonomy loops. The semiclassical limit of the spectral triple gives the Dirac Hamiltonian in 3+1 dimensions. Also, timeindependent lapse and shift fields emerge from the semiclassical states. Our analysis shows that the model might contain fermionic matter degrees of freedom. http://arxiv.org/abs/hepth/0601127 Intersecting Connes Noncommutative Geometry with Quantum Gravity Authors: Johannes Aastrup, Jesper M. Grimstrup (Submitted on 18 Jan 2006) Abstract: An intersection of Noncommutative Geometry and Loop Quantum Gravity is proposed. Alain Connes' Noncommutative Geometry provides a framework in which the Standard Model of particle physics coupled to general relativity is formulated as a unified, gravitational theory. However, to this day no quantization procedure compatible with this framework is known. In this paper we consider the noncommutative algebra of holonomy loops on a functional space of certain spinconnections. The construction of a spectral triple is outlined and ideas on interpretation and classical limit are presented. The semiclassical analysis presented in this paper does away with most of the ambiguities found in the initial semifinite spectral triple construction. The cubic lattices play the role of a coordinate system and a divergent sequence of free parameters found in the Dirac type operator is identified as a certain inverse infinitesimal volume element. 


#4
May3110, 03:02 PM

Sci Advisor
P: 5,364

Would a successful merger of LQG + NCG SM be considered a TOE?



#5
May3110, 04:05 PM

P: 2,828

Connes has been very clear about what he puts in and what he gets out. It is quite unfair to read that his prediction is "moot" while most mainstream approach did not care/dare to come up with specific numbers.
The fair statement is that the majority of physicists do not follow Connes route because they do not understand it, and the main contribution of suprised is to illustrate this fact. 


#6
Jun310, 10:54 AM

Sci Advisor
P: 5,364




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