Can long-range forces can be mediated by continuous spin particles?

Perimeter researchers Natalia Toro and Philip Schuster are investigating whether long-range forces can be mediated by continuous spin particles. They've found more than they bargained for.

Perimeter Faculty members Philip Schuster and Natalia Toro ventured down a dark alley expecting to reach a dead end.
Instead, they found a wide-open field.

The figurative dark alley was the study of continuous spin particles – a study Schuster and Toro believed was headed nowhere. "Our goal in the beginning was to prove that continuous spin particles don't make sense," says Toro.

"We wanted to write a paper entitled 'We Can Stop Thinking About Continuous Spin,'" adds Schuster. "We tried, but so far we've failed." What they discovered, in fact, made them think it's time to start taking continuous spin more seriously.

Continuous spin particles require a bit of backstory. There are four known forces in nature. Two, the weak nuclear force and the strong nuclear force, work only over very short distances – we mostly see them inside atomic nuclei. The other two forces, electromagnetism and gravity, can reach across galaxies. This is because they're mediated by massless particles – the photon for electromagnetism, the as-yet-unobserved graviton for gravity.

Photons and gravitons (and many other particles) have an intrinsic quality called spin. It's an imperfect analogy, but you can think of spin as nature's smallest bar magnet: it gives the particles something like a north and a south pole, which can point in any direction.