String Phenomenology

The main current focus of String phenomenology is the investigation of the general features that characterise effective field theories of consistent quantum gravity models. This means understanding the structure of low-energy supergravity models, their relations to string compactifications and their implications for the so-called swampland program.

The vacuum selection process is a longstanding problem of String Theory, whose solution is central for any attempt to extracting meaningful phenomenology. Most of the features of the effective 4-dimensional models one can generate from String Theory depend on the properties of the vacuum: the value of the cosmological constant, the effective particle content, their masses, couplings and most of their symmetries. Understanding the structure of low-energy supergravity models can be done by analyzing the allowed couplings, vacua and especially their supersymmetry breaking patterns. Time and again we have been explicitly constructing models in various dimensions that had not been previously analyzed, fully or in part. We have developed new techniques to find, study and classify vacua in gauged supergravities and we are currently understanding their relation to higher-dimensional theories.

Low energy supergravity models are plagued by a huge number of moduli (massless scalar fields), whose expectation values determine many couplings between the fields and the resulting physics. Flux compactifications provide a simple perturbative framework in which one can address this problem. We study how this affects the geometry of the allowed internal manifolds in compactifications to 4 dimensions and spell the dictionary between 4-dimensional couplings and higher dimensional properties. We are especially interested in cases where the reduction process uses locally geometric backgrounds, where duality symmetries play a prominent role and new mathematical tools are needed.

An interesting area where such studies can be usefully applied is string cosmology. Inflation could have happened at a very high energy scale. We are therefore interested in all sorts of imprints that could be related to low-energy effects deriving from string theory.