Compactified string theories — Generic predictions for particle physics

Abstract

In recent years it has been realized that in string/M theories compactified to four dimensions which satisfy cosmological constraints, it is possible to make some generic predictions for particle physics: a nonthermal cosmological history before primordial nucleosynthesis, a scale of supersymmetry breaking which is "high" as in gravity mediation, and scalar superpartners too heavy to be produced at the LHC (although gluino production is predicted in many cases). When the matter and gauge spectrum below the compactification scale is that of the MSSM, a robust prediction of about 125 GeV for the Higgs boson mass, as well as predictions for future precision measurements, can be made. As a prototypical example, M theory compactified on a manifold of G2 holonomy leads to a good candidate for our "string vacuum", with the TeV scale emerging from the Planck scale, a de Sitter vacuum, robust electroweak symmetry breaking, and solutions of the weak and strong CP problems. In this article we review how these and other results are derived, from the key theoretical ideas to the final phenomenological predictions.