Unified Quantum Field: Is it Possible?

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Discussion Overview

The discussion revolves around the concept of unifying all known forces in physics into a single field, particularly before the Planck Epoch. Participants explore the mathematical and logical possibilities of such unification, referencing theories like electroweak unification and grand unification models.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Some participants question whether all forces could have been unified into one field before the Planck Epoch and if this is mathematically and logically feasible.
  • Others highlight the lack of a comprehensive theory for quantum gravity and the existing gaps in knowledge regarding force unification.
  • Electroweak unification is discussed as an example, with some noting that it illustrates how one field can appear as multiple fields due to spontaneous symmetry breaking.
  • Participants debate the interpretation of fields and forces, suggesting that the number of fields does not necessarily equate to the number of forces, and that different models can represent the same underlying physics.
  • Grand unification theories, such as SU5, are mentioned, with discussions on how they propose a single force while introducing additional gauge bosons that do not correspond to the Standard Model forces.
  • Questions arise about the nature of the unified force and its role in particle interactions, with some participants seeking clarification on the processes involved in such unification.
  • There is a discussion on whether electroweak unification was achieved without a complete theoretical framework, with varying opinions on what constitutes a "full proper theory."
  • Some participants express skepticism about the feasibility of achieving the necessary conditions for unification in the universe, questioning if such energies could ever be realized.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the nature of unification, the adequacy of current theories, or the feasibility of achieving the necessary conditions for such unification. Multiple competing views and uncertainties remain throughout the discussion.

Contextual Notes

Limitations include the unresolved status of grand unification theories and quantum gravity, as well as the dependence on specific interpretations of gauge theories and the definitions of forces and fields.

  • #31
Wikipedia says that Glashow graduated from Cornell in 1954 (before 1957 parity violation) and received his PhD from Harvard in 1959 (after parity violation). AFAIRecall the topic for Glashow's dissertation was supplied by Schwinger to extend the then familiar U(1) gauge symmetry which generates electromagnetism to now perform the more complicated version of this calculation for SU(2) symmetry. (Motivated by the 1954 Yang-Mills models then recently proposed?) If this work was completed in 1959 it was then a few years later in 1961 when Glashow proposed SU(2)xU(1) to which Weinberg later added the Higgs mechanism (1964) to arrive at the 1967 model cited today.

Performing this same gauge symmetry calculation for the SU(3) group delivers QCD and the 8 gluon (performed by others Gell-Mann?)
 
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  • #32
David Neves said:
The U(1) of electromagnetism is still there. It's sitting diagonally inside SU(2).

I don't think this is quite correct. It is true that the U(1) in SU(2) x U(1) (the electroweak gauge group) is not the U(1) of electromagnetism, it's hypercharge. But the U(1) of electromagnetism is not "inside" the electroweak SU(2) (which is weak isospin). It's a combination of part of weak isospin and part of hypercharge.
 
  • #33
  • #34
David Neves said:
I was just trying to respond to his post

Yes, you're right, I was being sloppy in that post. It should really be "SU3 is strong, SU2 is weak isospin, U1 is weak hypercharge", at least if we talk about the fundamental Lagrangian before electroweak symmetry breaking. After electroweak symmetry breaking we have a more complicated situation, where we have two charged weak gauge bosons that take up two of the SU2 degrees of freedom, and a neutral weak gauge boson and electromagnetic gauge boson (the photon) that are each linear combinations of the remaining SU2 degree of freedom and the U1 hypercharge degree of freedom.
 

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