Editing Theory of everything (section)

===Loop quantum gravity===
Current research on [[loop quantum gravity]] may eventually play a fundamental role in a theory of everything, but that is not its primary aim.<ref>{{cite web
 |last=Potter
 |first=Franklin
 |date=15 February 2005
 |url=http://www.sciencegems.com/discretespace.pdf
 |title=Leptons And Quarks In A Discrete Spacetime
 |work=Frank Potter's Science Gems
 |access-date=2009-12-01
 |archive-date=2021-03-09
 |archive-url=https://web.archive.org/web/20210309121814/http://www.sciencegems.com/discretespace.pdf
 |url-status=live
 }}</ref> Loop quantum gravity also introduces a lower bound on the possible length scales.

There have been recent claims that loop quantum gravity may be able to reproduce features resembling the [[Standard Model]]. So far only the first generation of [[fermion]]s ([[lepton]]s and [[quark]]s) with correct parity properties have been modelled by [[Sundance Bilson-Thompson]] using [[preon]]s constituted of braids of spacetime as the building blocks.<ref>{{cite journal |title=Quantum gravity and the standard model |last=Bilson-Thompson |first=Sundance O. |author2=Markopoulou, Fotini |author3=Smolin, Lee |doi=10.1088/0264-9381/24/16/002 |date=2007 |journal=Classical and Quantum Gravity |volume=24 |issue=16 |pages=3975–3994 |arxiv=hep-th/0603022 |bibcode=2007CQGra..24.3975B|s2cid=37406474 }}</ref> However, there is no derivation of the [[Lagrangian (field theory)|Lagrangian]] that would describe the interactions of such particles, nor is it possible to show that such particles are fermions, nor that the gauge groups or interactions of the Standard Model are realised. Use of [[quantum computing]] concepts made it possible to demonstrate that the particles are able to survive [[quantum fluctuation]]s.<ref>{{cite journal |url=https://www.newscientist.com/channel/fundamentals/mg19125645.800 |journal=New Scientist |title=You are made of space-time |first=Davide |last=Castelvecchi |author2=Valerie Jamieson |issue=2564 |date=August 12, 2006 |access-date=September 16, 2017 |archive-date=February 9, 2008 |archive-url=https://web.archive.org/web/20080209025208/http://www.newscientist.com/channel/fundamentals/mg19125645.800 |url-status=live }}</ref>

This model leads to an interpretation of electric and color charge as topological quantities (electric as number and chirality of twists carried on the individual ribbons and colour as variants of such twisting for fixed electric charge).

Bilson-Thompson's original paper suggested that the higher-generation fermions could be represented by more complicated braidings, although explicit constructions of these structures were not given. The electric charge, color, and parity properties of such fermions would arise in the same way as for the first generation. The model was expressly generalized for an infinite number of generations and for the weak force bosons (but not for photons or gluons) in a 2008 paper by Bilson-Thompson, Hackett, Kauffman and Smolin.<ref>{{cite arXiv |eprint=0804.0037 |class=hep-th |first1=Sundance |last1=Bilson-Thompson |first2=Jonathan |last2=Hackett |title=Particle Identifications from Symmetries of Braided Ribbon Network Invariants |date=2008 |author3=Kauffman, Lou |author4=Smolin, Lee}}</ref>