String Theory - the most compelling candidate for a unified "Theory of Everything" - is believed to have a huge number of possible four-dimensional solutions, giving rise to a multitude of universes (Multiverse) with all possible physical laws. This has led to the argument that the constants in the physical laws that we measure in our universe do not come from an underlying unified theory, but are environmental variables, determined by where we are in this Multiverse. Furthermore, this line of reasoning allows one to explain the enormous amount of fine-tuning observed in the physical laws governing our universe via anthropic arguments.
The purpose of this project is to unequivocally establish that a very large number of these solutions have to be discarded, either because they are inconsistent, unstable, or ruled out by experimental results from the Large Hadron Collider. I plan to do this by a thorough examination of the ingredients that enter in the construction of solutions with a positive cosmological constant and of extensions of the Standard Model in string theory.
This would establish that string theory does not have a Multiverse of vacua resembling our universe, which would shatter one of the cornerstones of the anthropic/multiverse paradigm, restore the quest for predictability of string theory, and - if supersymmetry is not found - for constructing new proposals to solve the hierarchy problem.