Physicists have shown that the key signatures of string theory can arise naturally from a handful of simple rules about particle behavior at extreme energies. Researchers from Caltech, New York University, and a Barcelona institute reached this result using a bootstrap approach that starts with minimal assumptions rather than presupposing strings. The work has been accepted for publication in Physical Review Letters.
The team began with two conditions on how particles scatter in high-energy collisions. One requires the scattering probabilities to drop off rapidly at very high energies, a property known as ultrasoftness. The second imposes the fewest possible points where those probabilities reach zero. From these constraints alone, the mathematics produced the infinite tower of particle masses and spins that define the string spectrum, along with other hallmarks of the theory.