Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Are there any graphene planck-scale quantum gravity?

  1. Mar 23, 2010 #1
    Are there any "graphene" planck-scale quantum gravity?

    I'm wondering if there is any QG or emergent structure that is "graphene" due to suggestions from this paper, specifically,

    does LQG, SF, CDT,M-theory, etc., suggest space consists of discrete points arranged in a non-cubic lattice?

    Spin and the Honeycomb Lattice: Lessons from Graphene
    Matthew Mecklenburg, B. C. Regan
    (Submitted on 19 Mar 2010)
    Spin-1/2 particles such as the electron are described by the Dirac equation, which allows for two spin eigenvalues (up or down) and two types of energy eigenvalues (positive or negative, corresponding to the electron and the positron). A model of electrons hopping from carbon atom to carbon atom in graphene's honeycomb lattice gives low-energy electronic excitations that obey a relation formally identical to a two-dimensional Dirac equation. In graphene the spin equivalent, termed pseudospin, arises from the degeneracy introduced by the honeycomb lattice's two inequivalent atomic sites per unit cell. Previously it has been thought that the usual electron spin and the pseudospin indexing the graphene sublattice state are merely analogues. Here we show that the pseudospin is also a real, intrinsic angular momentum. This identification explains the suppression of electron backscattering in carbon nanotubes and the angular dependence of light absorption by graphene. Furthermore, it suggests that the half-integer spin of the quarks and leptons could derive from hidden substructure, not of the particles themselves, but rather of the space in which these particles live. In other words, the existence of spin might be interpreted as evidence that space consists of discrete points arranged in a non-cubic lattice.
  2. jcsd
  3. Mar 23, 2010 #2


    User Avatar

    Re: Are there any "graphene" planck-scale quantum gravity?

    By non-cubic they suggest hex. packing.
  4. Mar 24, 2010 #3
    Re: Are there any "graphene" planck-scale quantum gravity?

    How is what they are proposing any different from the Feynmann checkerboard model (also 2-d)?

    As soon as I saw 2-d hopping reproducing Dirac, that is what pops to mind. And that doesn't require "two inequivalent atomic sites per unit cell".

    Anyway, in answer to your question:
    There are problems extending the checkboard models to 4-d spacetime. So that would have to be resolved confidently before people would start seriously considering curved spacetime and approaching a quantum gravity theory from this angle.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook