John Carlos Baez on Nostr: Here's a good talk by Ed Witten. It's so good that even Peter Woit, who hates string ...
Here's a good talk by Ed Witten. It's so good that even Peter Woit, who hates string theory, recommends it!
A remarkable feature of the strong force is that while quarks have something like electric charge, called 'color', except at very high temperatures quarks always come in bunches where the color cancels out - they're 'colorless'.
For example a quark and antiquark can form a meson, which is colorless. Also three quarks can form a baryon, which is colorless. (Yes, color charge behaves more subtly than electric charge.)
Why are all the particles we see colorless? This is the mystery of 'confinement'. While the ultimate proof of confinement may require massive computer calculations using 'lattice gauge theory', there have long been hopes that we can understand it more simply using approximate calculations.
Witten explains two approaches. One is the '1/N expansion'. While there are 3 different colors of quarks, we can imagine a world where there are N, and things simplify as N → ∞. Another is string theory.
They're connected: there's some evidence that as N → ∞, our theory of the strong force would behave more and more like a string theory. But Witten admits
"The string theory we want is probably quite unlike any that we actually know, as of now. We don’t know how to make a string theory with the short distance behavior [that we see]".
https://www.youtube.com/watch?v=TvIz-6YOdKs
A remarkable feature of the strong force is that while quarks have something like electric charge, called 'color', except at very high temperatures quarks always come in bunches where the color cancels out - they're 'colorless'.
For example a quark and antiquark can form a meson, which is colorless. Also three quarks can form a baryon, which is colorless. (Yes, color charge behaves more subtly than electric charge.)
Why are all the particles we see colorless? This is the mystery of 'confinement'. While the ultimate proof of confinement may require massive computer calculations using 'lattice gauge theory', there have long been hopes that we can understand it more simply using approximate calculations.
Witten explains two approaches. One is the '1/N expansion'. While there are 3 different colors of quarks, we can imagine a world where there are N, and things simplify as N → ∞. Another is string theory.
They're connected: there's some evidence that as N → ∞, our theory of the strong force would behave more and more like a string theory. But Witten admits
"The string theory we want is probably quite unlike any that we actually know, as of now. We don’t know how to make a string theory with the short distance behavior [that we see]".
https://www.youtube.com/watch?v=TvIz-6YOdKs