Embedding the axio-chameleon screening of fifth-forces into string theory

Light scalar fields are ubiquitous in beyond the Standard Model and string constructions, but they naively induce unobserved fifth-forces. Axio-chameleon screening has recently been proposed as a promising mechanism to explain the absence of these fifth-forces, and the goal of this thesis is to embed it in String Theory. In particular, a good contender seems to be a D3/anti-D3-brane moving on a warped deformed conifold along both the radial and some angular directions. In the model presented here, the Standard Model is assumed to live on the brane and the radial brane-position modulus couples to it as a Quasi-Brans-Dicke scalar through the warp factor. This can be interpreted as a Quintessence field and the screening mechanism provides justification for the lack of observable fifth-forces in solar-system experiments.