# Axions as a new particle

1. Jan 12, 2016

### argus733

Just read an article on axions as a new particle. Neutrons that have an electrical field with their magnetic fields, and I was wondering how the two interact to produce a "neutralizing flow" collectively. [Gerard t' Hoofts loophole involving the T invariance.] Newb. Not trying to put on airs. Just trying to get the basic eletro dynamic, gravimetric, magnetic interactions if, where, and how they apply to better understand this article. https://www.quantamagazine.org/2016...geek&utm_medium=email&utm_campaign=newsletter

2. Jan 12, 2016

### Hornbein

It so happens I read that article yesterday. I think it works like this: a positive ion enters a metal. It attracts electrons until the ion's electric field is cancelled at a distance. (This is pretty obvious: if the electric field weren't cancelled, it would attract electrons ad infinitum. )

The proton's magnetic field induces an electrical current of electrons around it. This current produces a magnetic field that is almost equal and opposite to the magnetic field of the proton, hence canceling it out as well.

Last edited: Jan 13, 2016
3. Jan 13, 2016

### argus733

Thanks for the reply. Is the magnetic field a polar opposite of the electrical field?

4. Jan 13, 2016

### ChrisVer

I don't understand the question. I think what t' Hooft figured out (via the QCD vacuum) that there was an additional symmetry-respecting term in the Lagrangian which came with the $\theta$-term and would involve an electric dipole moment (EDM) of the neutron (which naturally) would be high enough to be measured by our experiments... the experiments showed that if there is really an EDM of the neutron, then the $\theta$ parameter should be way smaller than 1, and that's why the axion is used to cancel it out (from being naturally 1 to be smaller than $10^{-9}$) after getting a vev.

5. Jan 13, 2016

### argus733

My higher education is self taught, but after stumbling through your description, I believe you gave me not what I asked, but what I needed. Thank you.

6. Jan 25, 2016

### ohwilleke

They are more orthogonal than polar opposites, but that understates that extent to which they are interrelated. A magnetic field is induced by moving an electrical charge in space. Electrical fields arise from the existence of an electrical charge. Most electrical generators in daily life work by moving electrical charges (in a wire) through a magnetic field. Electrical fields and magnetic fields are different aspects of a single force, electromagnetism which is mediated by photons according to the laws of quantum electrodynamics (QED) which has as its classical limit, Maxwell's equations of electromagnetism.

The "unsolved problem of physics" which gives rise to the desire to hypothesize the existence of the axion contemplated by Pecci et al. and name shortly thereafter is the "strong CP problem" which is that strong interactions in practice do not appear to ever have a CP violation even tough it is easy to imagine a term with a coefficient theta that would allow for CP violation in strong interactions.

Like the "naturalness" problem, the strong CP problem is basically a case of physicists second guessing Nature's choice of physical constants.

One heuristic argument that the strong CP problem isn't a problem is that gluons are massless and hence do not experience time and hence shouldn't give rise to CP violation, and that the same is true of the massless photon which likewise doesn't give rise to CP violation in electromagnetism. In contrast, the carrier bosons of the weak force which does exhibit CP violation are massive, and hence experience time in their frame of reference, and hence are capable of giving rise to CP violating (which is to say, time symmetry violating) interactions.

Of course, if the strong CP problem isn't a problem, then there is no need to hypothesize the existence of axions to solve it.

7. Jan 26, 2016

### argus733

Thanks for your time. Is it true that there was less entropy in the past than what is current? And, if you could achieve a mass-less state would that be a timeless stasis? How are gluons measured from our point of view?