New String Theory Model Incorporates Inflation

For years now, the Standard Model has been used by physicists as the main theory in studying the universe. After the electric and the magnetic mixed into the electromagnetic force, and after the release of Einstein's theory of relativity, scientists tried to unify the remaining forces - gravity, strong nuclear forces, and the weak nuclear forces into a theory that could explain everything.

Right from the beginning, they noticed something was wrong. Einstein's theory of relativity, that was explaining gravitational interactions and the quantum theory describing particle interactions, were not working together while trying to explain one of the most fascinating objects in the universe: the black hole. The gravitational force was too weak compared to the other forces, and the theory would not stand when trying to describe the singularity.

The Standard Model predicts that elementary particles such as electrons, protons, neutrinos are shaped like incredibly small spheres. A new theory emerged: String Theory. This new innovating theory says that particles are not sphere-like, but are rather like a vibrating string, closed or open. The frequency at which the string was vibrating determined the type of particles it defined. But this theory had its own glitches. In its infant state, there were about eleven variations on the same theory, each predicting extra spatial dimensions on top of the four observable ones, and parallel universes, and there was no known experiment that could demonstrate the theory.

The string theory is not the most popular candidate for a unified theory, but it is not completely understood. Physicists are still trying to create an experiment that would produce evidence, but are gaining crucial information about how accurately it can predict the observable universe.

The new model incorporates inflation, which is the most realistic model of the string theory. "They're complicated. They're fancy. They have a lot of 'moving parts,' and we need to fine-tune all of them, so we can't verify anything to a high degree of accuracy. It forces us to ask-are we confident that we really understand what's going on?", said Shamit Kachru.

Kachru investigated a total of three versions of the simplest formulation of string theory, and found that they are incompatible with inflation. But there are many more models that incorporate the string theory and inflation.

Kachru and his colleagues published their work in Physical Review Letters D, providing a framework for others in search of simple inflationary models of the string theory.