A The "electroweak eta meson"

[mitchell porter]

TL;DR Summary

New standard model particle, or illusion of theorists?

This is an alert about a claim regarding the standard model, that got a burst of attention in the past two weeks.

The original paper came out last year:

"The electroweak η_W meson" by Gia Dvali, Archil Kobakhidze, Otari Sakhelashvili (2024)

The recent follow-up and other responses are

"η_W-meson from topological properties of the electroweak vacuum" by Dvali et al

"Hiding in Plain Sight, the electroweak η_W" by Giacomo Cacciapaglia, Francesco Sannino, Jessica Turner

"Astrophysical Consequences of an Electroweak η_W Pseudo-Scalar" by Hooman Davoudiasl

You can see the usual approach to the "electroweak theta term" in discussions here:

https://physics.stackexchange.com/search?q=electroweak+theta

If I was, say, a Quanta Magazine journalist writing about this, I'd want to start with an exposition of the theta or vacuum angle in QCD, the idea of topological susceptibility, and how it complicates the masses of the light-quark mesons. Specifically, all those mesons should themselves be light - as the Goldstone bosons of chiral symmetry breaking they should be massless, with some mass then coming from the quark masses. But one of them, the η' meson (eta prime), is heavy, and the reason is that it is the Goldstone boson of the axial part of chiral symmetry, and that symmetry is anomalous, i.e. does not actually hold, so the η' mass is not kept light by the symmetry. 't Hooft, Veneziano, and Witten all developed more detailed descriptions of where the mass comes from, in terms of the potentially CP-violating "theta term" of QCD, and the "topological susceptibility" which measures the sensitivity of the vacuum state to changes in the theta coupling.

The issue behind these new papers is whether there is a theta term in the electroweak interactions as well. The conventional view seems to be that it would somehow be rendered redundant by CP violation that already exists elsewhere in the electroweak sector. The idea that it might be there after all is at least thirty years old. This version is somehow an outgrowth of older ideas by Dvali on a gravitational theta term, and by Dvali and Funcke on the "gravi-majoron", an η_ν meson produced by the gravitational chiral anomaly and a neutrino condensate (work that I thought I had posted about here, years ago, but I can't find it now).

Of the two new papers by Dvali et al, one uses gravity to argue for an η_W meson, the other just uses the electroweak interaction. This may even be another occasion in which the possibility of a gauged SU(2) formulation of gravity hints at obscure relationships with the electroweak sector, but I would need to check that. Of the other two papers linked above, the one from Sannino's group claims that the η_W state is a superposition of a hydrogen atom and an antihydrogen atom (?!); while Davoudiasl sidesteps the theory issues and asks whether an η_W meson could explain dark matter or dark energy (as quintessence). He concludes, no.

 

[mad mathematician]

I wonder a state which is in a superposition that should annihilate itself before the wave function collapses...
Maybe this can also answer the seemingly interesting problem of why there's more matter than anti matter in the universe...

 

[mitchell porter]

I wonder a state which is in a superposition that should annihilate itself before the wave function collapses...
Maybe this can also answer the seemingly interesting problem of why there's more matter than anti matter in the universe...

It's not a state that leads to self-annihilation because it's not about having an atom and an anti-atom in the same branch of the wavefunction, it's about having a quantum state which has some probability to be an atom and some probability to be an anti-atom. It seems very weird to me, but if it does make sense and is moreover connected to all these chiral gravitational anomalies and so on, then absolutely it could lead to some new ideas about the early universe.

 

[mad mathematician]

It's not a state that leads to self-annihilation because it's not about having an atom and an anti-atom in the same branch of the wavefunction, it's about having a quantum state which has some probability to be an atom and some probability to be an anti-atom. It seems very weird to me, but if it does make sense and is moreover connected to all these chiral gravitational anomalies and so on, then absolutely it could lead to some new ideas about the early universe.

You mean as vectors the states are independent of eachother (i.e one is not a linear combination of the other).
Theoretically every particle should have an anti particle (unless they have no electric charge like the photon).

You said this paper was launched last year, it does take time to make a disturbance in the fabric of WWW...

 

[sbrothy]

Sorry for my dumb questions ans I’m obviously out of my depth here but it seems there’s an awful lot of talk about symmetry breaking yet the potential new symmetry seems to be buried under a heap of math looking suspiciously like string theory.

Is that what this is?

 

[mitchell porter]

Could you point to one or two examples, of the math you think looks like string theory?

 

[sbrothy]

Could you point to one or two examples, of the math you think looks like string theory?

Thank you for the rope. I’ll make good use of it. I think it was the mention of Yang-Mills and membranes that got me barking up a wrong tree. But in your laconic way you actually did answer my question. I’ll try to keep out of stuff I obviously don’t understand in the future. The big A should have been a dead giveaway.

Carry on.

 

[mitchell porter]

Yang-Mills is just ordinary quantum field theory; the strong and weak nuclear force are both Yang-Mills forces. But the reference to a membrane is peculiar and I didn't notice it myself. So far as I can tell, it is not meant to be anything real. It is analogous to the concept of a "test particle" employed elsewhere in physics, which is a fictitious entity used mathematically to probe force fields and so forth (e.g. one calculates the force that a particle would experience at a given location). 3-form fields naturally coupled to 2-dimensional objects and so here you get a "test membrane" instead.

 

[sbrothy]

Yang-Mills is just ordinary quantum field theory; the strong and weak nuclear force are both Yang-Mills forces. But the reference to a membrane is peculiar and I didn't notice it myself. So far as I can tell, it is not meant to be anything real. It is analogous to the concept of a "test particle" employed elsewhere in physics, which is a fictitious entity used mathematically to probe force fields and so forth (e.g. one calculates the force that a particle would experience at a given location). 3-form fields naturally coupled to 2-dimensional objects and so here you get a "test membrane" instead.

I have a suspicion it’s because I read the text in detail while the math is way beyond me, while you read the math and skim the text.