String Phenomenology in an established and active area in string theory which faces the challenges of connecting it with the observed Particle Physics theories, like the Standard Model or its extensions at higher energies, as well as addressing issues related to the early inflationary epoch of the Universe and its ultimate fate, controlled by the nature of the dark energy.

One of the main goals of WG2, is the development of tools to enlarge the class of Particle Physics theories that can be constructed within string theory. This requires improving on different techniques in heterotic orbifolds and Calabi-Yau compactifications, and in constructing type II orientifolds, and their non-perturbative generalizations via F-theory.

Another line of research is the study of generalized flux compactifications, and the development of the relevant new mathematical tools, in order to address the question of moduli stabilization, i.e. the removal of the massless scalars that plague standard string compactifications (so as to improve the phenomenological virtues of the models). An important point in the analysis will also include the inclusion of non-perturbative D-brane instanton effects.

These ingredients will clarify the structure of phenomenologically viable constructions with full moduli stabilization, and will offer new insights into the string imprint on the most timely questions of micro- and macro-physics, including the electroweak Higgs sector, the existence and nature of supersymmetry and its breaking, early universe inflation, and the cosmological constant and dark energy.