Physicists Found String Theory Without Even Looking for It

The title, due to a necessary brevity in how titling works on social media these days, doesn’t convey the actual meaning of the finding - they aren’t saying they found the theory in their data or observations or calculations, they’re saying in their data and observations and calculations emerged a core, defining feature of string theory. They didn’t find the theory, they found a very specific feature that is found in string theories, and that’s pretty neat.

“In a string theory framework, as you increase the energy transfer between particles, you will see a swift fall off in the probability that the particles will scatter. It’s like the particles don’t even want to scatter off one another, but rather pass freely,” Cheung says. “The scattering amplitudes don’t go to infinity. It’s better behaved.”

The researchers used this ultrasoft behavior as one of their core assumptions. They also assumed a property called “minimal zeros,” which limits the number of special points where scattering probabilities vanish.

“Remarkably, consistency requires scattering amplitudes not only to interact but also to not interact at special kinematic points called ‘zeros.’ The assumption of ‘minimal zeros’ demands the sparsest number of such vanishing points mathematically allowed by the equations,” Cheung says.

From only these assumptions, the researchers demonstrated mathematically that the resulting solutions naturally reproduced the central features of string theory, including its characteristic spectrum of particles and interaction strengths.

“The precise details of string theory emerged automatically, including the infinite tower of massive spinning particles that form the ‘harmonics’ of the string that the theory is famous for,” says co-author Grant N. Remmen (PhD ’17), the James Arthur Postdoctoral Fellow at New York University.