Quantum field theory and pair creation/annihilation

The creation and annihilation of matter-antimatter pairs is usually taken as proof that, somehow, fields can condense into matter-particles or, conversely, that matter-particles can somehow turn into light-particles (photons), which are nothing but traveling electromagnetic fields. However, pair creation always requires the presence of another particle and one may, therefore, legitimately wonder whether the electron and positron were not already present, somehow.

Carl Anderson’s original discovery of the positron involved cosmic rays hitting atmospheric molecules, a process which involves the creation of unstable particles including pions. Cosmic rays themselves are, unlike what the name suggests, no rays – not like gamma rays, at least – but highly energetic protons and atomic nuclei. Hence, they consist of matter-particles, not of photons. The creation of electron-positron pairs from cosmic rays also involves pions as intermediate particles:

1. The π+ and π particles have net positive and negative charge of 1 e+ and 1 e respectively. According to mainstream theory, this is because they combine a u and d quark but – abandoning the quark hypothesis[1] – we may want to think their charge could be explained, perhaps, by the presence of an electron![2]

2. The neutral pion, in turn, might, perhaps, consist of an electron and a positron, which should annihilate but take some time to do so!

Neutral pions have a much shorter lifetime – in the order of 10-18 s only – than π+ and π particles, whose lifetime is a much more respectable 2.6 times 10-8 s. Something you can effectively measure, in order words.[3] In short, despite similar energies, neutral pions do not seem to have a lot in common with π+ and π particles. Even the energy difference is quite substantial when measured in terms of the electron mass: the neutral pion has an energy of about 135 MeV, while π+ and π particles have an energy of almost 140 MeV. To be precise, the difference is about 4.6 MeV. That is quite a lot: the electron rest energy is 0.511 MeV only.[4] So it is not stupid to think that π+ and π particles might carry an extra positron or electron, somehow. In our not-so-humble view, this is as legitimate as thinking – like Rutherford did – that a neutron should, somehow, combine a proton and an electron.[5]

The whole analysis – both in the QED as well as in the QCD sector of quantum physics – would radically alter when thinking of neutral particles – such as neutrons and π0 particles – not as consisting of quarks but of protons/antiprotons and/or electrons/positrons cancelling each other’s charges out. We have not seen much – if anything – which convinces us this cannot be correct. We, therefore, believe a more realist interpretation of quantum physics should be possible for high-energy phenomena as well. With a more realist theory, we mean one that does not involve quantum field and/or renormalization theory.

Such new theory would not be contradictory to the principle that, in Nature, the number of charged particles is no longer conserved, but that total (net) charge is actually being conserved, always. Hence, charged particles could appear and disappear, but they would be part of neutral particles. All particles in such processes are very short-lived anyway, so what is a particle here? We should probably think of these things as an unstable combination of various bits and bobs, isn’t it? 😊

So, yes, we did a paper on this. And we like it. Have a look: it’s on ResearchGate, academia.edu, and – as usual – Phil Gibb’s site (which has all of our papers, including our very early ones, which you might want to take with a pinch of salt). 🙂

[1] You may be so familiar with quarks that you do not want to question this hypothesis anymore. If so, let me ask you: where do the quarks go when a π± particle disintegrates into a muon-e±?

[2] They disintegrate into muons (muon-electrons or muon-positrons), which themselves then decay into an electron or a positron respectively.

[3] The point estimate of the lifetime of a neutral pion of the Particle Data Group (PDG) is about 8.5 times 10-17 s. Such short lifetimes cannot measured in a classical sense: such particles are usually referred to as resonances (rather than particles) and the lifetime is calculated from a so-called resonance width. We may discuss this approach in more detail later.

[4] Of course, it is much smaller when compared to the proton (rest) energy, which it is about 938 MeV.

[5] See our short history of quantum-mechanical ideas or our paper on protons and neutrons.

The concept of a field

I ended my post on particles as spacetime oscillations saying I should probably write something about the concept of a field too, and why and how many academic physicists abuse it so often. So I did that, but it became a rather lengthy paper, and so I will refer you to Phil Gibbs’ site, where I post such stuff. Here is the link. Let me know what you think of it.

As for how it fits in with the rest of my writing, I already jokingly rewrote two of Feynman’s introductory Lectures on quantum mechanics (see: Quantum Behavior and Probability Amplitudes). I consider this paper to be the third. 🙂

Post scriptum: Now that I am talking about Richard Feynman – again ! – I should add that I really think of him as a weird character. I think he himself got caught in that image of the ‘Great Teacher’ while, at the same (and, surely, as a Nobel laureate), he also had to be seen to a ‘Great Guru.’ Read: a Great Promoter of the ‘Grand Mystery of Quantum Mechanics’ – while he probably knew classical electromagnetism combined with the Planck-Einstein relation can explain it all… Indeed, his lecture on superconductivity starts off as an incoherent ensemble of ‘rocket science’ pieces, to then – in the very last paragraphs – manipulate Schrödinger’s equation (and a few others) to show superconducting currents are just what you would expect in a superconducting fluid. Let me quote him:

“Schrödinger’s equation for the electron pairs in a superconductor gives us the equations of motion of an electrically charged ideal fluid. Superconductivity is the same as the problem of the hydrodynamics of a charged liquid. If you want to solve any problem about superconductors you take these equations for the fluid [or the equivalent pair, Eqs. (21.32) and (21.33)], and combine them with Maxwell’s equations to get the fields.”

So… Well… Looks he too is all about impressing people with ‘rocket science models’ first, and then he simplifies it all to… Well… Something simple. 😊

Having said that, I still like Feynman more than modern science gurus, because the latter usually don’t get to the simplifying part. :-/

Gauge theories

Sean Carroll is currently wrapping up a series of videos about the Biggest Ideas in the Universe. All of the usual hocus-pocus around quantum fields and quarks. The last (?) in this series – Idea No. 15 – is about gauge theories. It is one of those things: the multiplication of theoretical and mathematical concepts after WW II has been absolutely mind-boggling !

Any case, as an antidote, it is good to remind ourselves that – unlike other field theories (quantum field theories, to be precise) – we have one gauge only in electromagnetism – the Lorenz gauge – and it is not some weird metaphysical concept resulting from equally weird redundant degrees of freedom in our theory. No. The Lorenz gauge just pops when re-writing Maxwell’s equations in terms of four-vector potentials. That’s all. Nothing more, nothing less.

For a change, the Wikipedia article on it is very readable and straightforward: it also usefully links the unique (Lorenz) gauge for the QED sector to the concept of retarded potentials: traveling fields – and changes in static fields – travel at the speed of light. Any signal, in fact, will travel at the speed of light. We wrote about the implications of this in regard to de Broglie‘s concept of the matter-wave in earlier papers, so we will refer you there. 🙂

So should you or should you not invest in studying gauge theories? I don’t think so, but I’ll keep reading myself. I will keep you informed about what I learn (or not).