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

Penrose zigzag model of Higgs-electron interaction

  1. Jul 21, 2012 #1
    Roger Penrose in Chapter 25 of his book The Road to Reality describes a "zigzag" model of the electron that consists of a pair of massless components one with a left-handed spin (the zig) and the other with a right-handed spin (the zag).

    He says that the Dirac equation can be written as a pair of equations which describe each component being continually transformed into the other. The strength of the coupling between these equations depends on the electron mass.

    Thus the electron is continually jittering between a massless zig and a zag particle. The energy in this vibrating motion provides the electron with its rest mass. (This is Penrose's explanation of the well-known electron "zitterbewegung")

    Penrose then goes on to say that one can think of the Higgs field as taking over the role of the electron mass. One imagines that it is the continual interaction with the Higgs field that causes the electron zig to be converted to the electron zag and vice-versa. Again it is the energy in this vibrating motion that gives rise to the electron's rest mass.

    I think this picture is better than the particle-in-molasses picture that one often hears. In my view the Higgs interaction explains the origin of the rest mass/energy of a particle (and therefore its gravitational mass) but not its inertia defined as its resistance to being accelerated. I think inertia might have a "Machian" gravitational cause as outlined in Dennis Sciama's "On the origin of inertia":
    Last edited: Jul 21, 2012
  2. jcsd
  3. Jul 21, 2012 #2


    User Avatar
    Science Advisor

    The "zig" and "zag" fields are apparently Penrose's terminology for the right- and left-handed components of the electron.
    Anything would be better than the Higgs-as-molasses picture.
    A pre-Einsteinian idea, intuitive but primitive, and long ago shown to be false.
  4. Jul 21, 2012 #3
    Are these right- left-handed components the same as the two components of the spinor?
  5. Jul 21, 2012 #4


    User Avatar
    Science Advisor

    Any Dirac spinor can be decomposed into right- and left-handed parts ψR and ψL using the chirality operators PR = (1 + γ5)/2 and PL = (1 - γ5)/2. For a massless particle, PR and PL commute with H and chirality is a good quantum number. But for a particle with mass, the mass term m(ψLψR + ψRψL) couples them together. The same holds true whether m is put in by hand or generated by the Higgs field.
  6. Jul 21, 2012 #5
    Ah, thanks. But what is γ5? I thought there were four gamma matrices? :confused:
  7. Jul 21, 2012 #6


    User Avatar
    Science Advisor
    Homework Helper

    γ5 is short for iγ0γ1γ2γ3 :wink:
  8. Jul 21, 2012 #7
    Penrose works with Pauli 2-spinors rather than the more usual Dirac 4-spinors.

    As I understand it a 2-spinor directly represents a spinning particle whereas the Dirac 4-spinor decribes a state with both spin and positive and negative energy components that can't be so easily visualised as a particle.
    Last edited: Jul 21, 2012
  9. Jul 21, 2012 #8


    User Avatar
    Science Advisor

    johne1618, Did Penrose say that, or is that your own interpretation? The massless Dirac equation decouples into two equations for two 2-component spinors. Although the equations contain the Pauli matrices, the spinors themselves are Weyl spinors. Also the solutions for each equation include both a positive energy solution and a negative energy solution.
  10. Jul 22, 2012 #9
    Sorry you're right this is largely my interpretation drawing from what Penrose writes in Chapter 24 and 25 of his book - I don't understand the mathematical details myself.

    However Penrose definitely does imply that his zigzag particle picture is more directly suggested by a superposition of Weyl 2-spinors rather than the more usual 4-spinor description using the Weyl or chiral basis.
    Last edited: Jul 22, 2012
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook