Quantum Physics: A Survivor’s Guide

A few days ago, I mentioned I felt like writing a new book: a sort of guidebook for amateur physicists like me. I realized that is actually fairly easy to do. I have three very basic papers – one on particles (both light and matter), one on fields, and one on the quantum-mechanical toolbox (amplitude math and all of that). But then there is a lot of nitty-gritty to be written about the technical stuff, of course: self-interference, superconductors, the behavior of semiconductors (as used in transistors), lasers, and so many other things – and all of the math that comes with it. However, for that, I can refer you to Feynman’s three volumes of lectures, of course. In fact, I should: it’s all there. So… Well… That’s it, then. I am done with the QED sector. Here is my summary of it all (links to the papers on Phil Gibbs’ site):

Paper I: Quantum behavior (the abstract should enrage the dark forces)

Paper II: Probability amplitudes (quantum math)

Paper III: The concept of a field (why you should not bother about QFT)

Paper IV: Survivor’s guide to all of the rest (keep smiling)

Paper V: Uncertainty and the meaning of the wavefunction (the final!)

Jean Louis Van Belle, 21 October 2020

Note: As for the QCD sector, that is a mess. We might have to wait another hundred years or so to see the smoke clear up there. Or, who knows, perhaps some visiting alien(s) will come and give us a decent alternative for the quark hypothesis and quantum field theories. One of my friends thinks so. Perhaps I should trust him more. 🙂

As for Phil Gibbs, I should really thank him for being one of the smartest people on Earth – and for his site, of course. Brilliant forum. Does what Feynman wanted everyone to do: look at the facts, and think for yourself. 🙂

Feynman’s religion

Perhaps I should have titled this post differently: the physicist’s worldview. We may, effectively, assume that Richard Feynman’s Lectures on Physics represent mainstream sentiment, and he does get into philosophy—less or more liberally depending on the topic. Hence, yes, Feynman’s worldview is pretty much that of most physicists, I would think. So what is it? One of his more succinct statements is this:

“Often, people in some unjustified fear of physics say you cannot write an equation for life. Well, perhaps we can. As a matter of fact, we very possibly already have an equation to a sufficient approximation when we write the equation of quantum mechanics.” (Feynman’s Lectures, p. II-41-11)

He then jots down that equation that Schrödinger has on his grave (shown below). It is a differential equation: it relates the wavefunction (ψ) to its time derivative through the Hamiltonian coefficients that describe how physical states change with time (Hij), the imaginary unit (i) and Planck’s quantum of action (ħ).

hl_alpb_3453_ptplr

Feynman, and all modern academic physicists in his wake, claim this equation cannot be understood. I don’t agree: the explanation is not easy, and requires quite some prerequisites, but it is not anymore difficult than, say, trying to understand Maxwell’s equations, or the Planck-Einstein relation (E = ħ·ω = h·f).

In fact, a good understanding of both allows you to not only understand Schrödinger’s equation but all of quantum physics. The basics are this: the presence of the imaginary unit tells us the wavefunction is cyclical, and that it is an oscillation in two dimensions. The presence of Planck’s quantum of action in this equation tells us that such oscillation comes in units of ħ. Schrödinger’s wave equation as a whole is, therefore, nothing but a succinct representation of the energy conservation principle. Hence, we can understand it.

At the same time, we cannot, of course. We can only grasp it to some extent. Indeed, Feynman concludes his philosophical remarks as follows:

“The next great era of awakening of human intellect may well produce a method of understanding the qualitative content of equations. Today we cannot. Today we cannot see that the water flow equations contain such things as the barber pole structure of turbulence that one sees between rotating cylinders. We cannot see whether Schrödinger’s equation contains frogs, musical composers, or morality—or whether it does not. We cannot say whether something beyond it like God is needed, or not. And so we can all hold strong opinions either way.” (Feynman’s Lectures, p. II-41-12)

I think that puts the matter to rest—for the time being, at least. 🙂

Planck’s quantum of action

I find it most amazing that – with few physical laws and geometry formulas – we are able to understand reality.

These laws – Maxwell’s equations, Einstein’s mass-energy equivalence relation, and the Planck-Einstein relation – are not easy. The geometry formulas – Euler’s formula, basically – are not easy either. But once you get them, all falls into place—like Enlightenment (or kensho, satori, nirvana, etc. if you’d happen to like Buddhist philosophy). 🙂

All has a resonant frequency: photons, electrons, protons, neutrons, atoms, molecules, complex systems—all that is stable. Unstable particles and systems do not obey the Planck-Einstein relation: ω = E/ħ. They die out: they are short-lived transients or even shorter-lived resonances. We should not refer to them as particles or particle-systems, and we need non-equilibrium math to analyze them.

It is all most beautiful. I will, therefore, not say anything more about it here. I’ve written about the nitty-gritty elsewhere.