String theory could be real? A bootstrap model reveals solid hint

String theory suggests that the most fundamental building blocks of the universe are not particles like electrons or quarks, but tiny, vibrating strings of energy.

It is the vibration and arrangement of these strings that then gives rise to particles, matter, energy, and other natural forces. The theory suggests that everything in this universe is interconnected and particles are not point-like objects but, in fact, strings.

However, string theory remains unproven to this date, but a new study reveals a bootstrap approach that strengthens its case.

Using scattering amplitudes to detect strings

Some previous studies estimate that a string is about 10⁻³⁵ m in size. The reason why scientists haven’t been able to detect strings is that even the world’s most powerful accelerator, the Large Hadron Collider can detect objects up to a size of 10^-20 m.

So confirming the presence of strings in an experimental setup is impossible for now. This is why the study authors adopted a theoretical bootstrap approach.

“A bootstrap is a mathematical construction in which insight into the physical properties of a system can be obtained without having to know its underlying fundamental dynamics,” said Remmen, one of the study authors and a postdoctoral fellow at New York University.

Instead of building everything from scratch, the approach calls for starting with basic rules that a system must follow. These rules are usually related to symmetry, cause-and-effect (causality), and mathematical consistency.

For instance, to describe the interaction of strings, the study authors employed scattering amplitudes, mathematical expressions that describe the likelihood of particles interacting and scattering off each other in a collision.

They used amplitudes called locality, and unitarity. The former means that nothing can affect something far away instantly—forces take time to travel, so causality stays consistent.

The latter, on the other hand, describes that in quantum mechanics, the chances of ‘all possible outcomes must always add up to 100%’, and those chances can’t be negative. This rule also limits how particles can interact with each other.

Surprisingly, when locality and unitarity were applied, the result of the bootstrap equation came out to be Veneziano amplitude, the same formula that describes string scattering.

Compelling evidence but not proof

The study reveals another interesting framework that hints towards the presence of strings and favors the string theory. It suggests that the big idea of string theory can be reduced to a smaller, simpler starting point that still leads to the same conclusions.

However, “this work can’t verify the validity of string theory, which like all questions about nature is a question for experiment to resolve,” stated Clifford Cheung, first author and a professor of theoretical physics at Caltech.

While scientists develop a particle accelerator powerful enough to detect strings, there is still a lot that theoretical models can reveal. For instance, the researchers plan to test a bootstrap approach involving multiple particles (the current study focuses on only two particles). Hopefully, these efforts will soon bring scientists closer to finding the strings they have been searching for decades.

The study has been published in the journal Physical Review Letters.