I recently pointed out that there are unfamiliar types of standing waves that violate the rules of the standing waves that we most often encounter in life (typically through musical instruments, or when playing with ropes and Slinkys) and in school (typically in a first-year physics class.) I’ve given you some animations here and here, along with some verbal explanation, that show how the two types of standing waves behave.
Today I’ll show you what lies “under the hood” — and how you yourself could make these unfamiliar standing waves with a perfectly ordinary physical system. (Another example, along with the relevance of this whole subject to the Higgs field, is discussed in chapter 20 of the book.)
This year marks a half-century since the discovery that a quantum field theory, now known as QCD (quantum chromodynamics), could be the underlying explanation for the strong nuclear force. That’s the force that holds quarks and gluons inside of protons and neutrons, and keeps protons and neutrons clumped together in atomic nuclei. This major step in theoretical physics occurred just a couple of years after it was discovered that a similar quantum field theory for the weak nuclear force (which includes W bosons, a Z boson and a Higgs boson) is mathematically consistent.
With these two breakthroughs came the sudden and unexpected triumph of quantum field theory, emerging as the basic mathematical and conceptual language for understanding the cosmos. It came after two decades in which most experts were convinced that quantum field theory was inconsistent, and only a stepping stone to something deeper.
This week I am in New York City attending two attached scientific meetings, both focused on QCD and other quantum field theories that share its key property, known as “confinement.” One meeting is hosted by New York University, and the other, the Annual Meeting of the Simons Collaboration on Confinement and QCD Strings, by the Simons Foundation. Many luminaries who have spent time on this subject are here together, ranging from David Gross, who co-invented the subject (and was a winner of the 2004 Nobel Prize), to brilliant graduate students who are hoping to reinvent it.
I’ve explained in earlier posts how we can calculate many things in the quantum field theory that is known as the “Standard Model” of particle physics, itself an amalgam of three, simpler quantum field theories.
the weak nuclear force and the electromagnetic force are turned off,
the electron, muon, tau, neutrinos, W, Z and Higgs particles are ignored
the three heavier types of quarks are also ignored
(See Figure 4 of Part 4 for more details.) This makes the calculations a lot simpler. And their results allow us, for instance, to understand why quarks and anti-quarks and gluons form the more complex particles called hadrons, of which protons and neutrons are just a couple of examples. Unfortunately, computer simulations still are nowhere near powerful enough for the calculation of some of the most interesting processes in nature… and won’t be for a long time.
Fig 1: The idealized, imaginary world whose quantum field theory is used to make computer simulations of the real-world strong-nuclear force.
This brings us to today’s story. Our success with the Standard Model might give you the impression that we basically understand quantum field theory and how to make predictions using it, with a few exceptions. But this would be far, far from the truth. As far as we can tell, much (if not most) of quantum field theory remains deeply mysterious. (more…)
As I think most of us in the field expected, professor Alexander Polyakov was selected from among the nominees as the winner of a cool $3 million checkFundamental Physics Prize today. (more…)
