I’ll just be doing a short post this week, I’ve been busy at a workshop on Flux Tubes here at Perimeter.
If you’ve ever heard someone tell the history of string theory, you’ve probably heard that it was first proposed not as a quantum theory of gravity, but as a way to describe the strong nuclear force. Colliders of the time had discovered particles, called mesons, that seemed to have a key role in the strong nuclear force that held protons and neutrons together. These mesons had an unusual property: the faster they spun, the higher their mass, following a very simple and regular pattern known as a Regge trajectory. Researchers found that they could predict this kind of behavior if, rather than particles, these mesons were short lengths of “string”, and with this discovery they invented string theory.
As it turned out, these early researchers were wrong. Mesons are not lengths of string, rather, they are pairs of quarks. The discovery of quarks explained how the strong force acted on protons and neutrons, each made of three quarks, and it also explained why mesons acted a bit like strings: in each meson, the two quarks are linked by a flux tube, a roughly cylindrical area filled with the gluons that carry the strong nuclear force. So rather than strings, mesons turned out to be more like bolas.
If you’ve heard this story before, you probably think it’s ancient history. We know about quarks and gluons now, and string theory has moved on to bigger and better things. You might be surprised to hear that at this week’s workshop, several presenters have been talking about modeling flux tubes between quarks in terms of string theory!
The thing is, science never forgets a good idea. String theory was superseded by quarks in describing the strong force, but it was only proposed in the first place because it matched the data fairly well. Now, with string theory-inspired techniques, people are calculating the first corrections to the string-like behavior of these flux tubes, comparing them with simulations of quarks and gluons, and finding surprisingly good agreement!
Science isn’t a linear story, where the past falls away to the shiny new theories of the future. It’s a marketplace. Some ideas are traded more widely, some less…but if a product works, even only sometimes, chances are someone out there will have a reason to buy it.