Particle theory

Abstract:

We study a number of realizations of axions existing in a multi-`throat' generalization of the warped throat geometry of a Randall-Sundrum slice of $AdS_5$. As argued by previous authors, the problem of generating a suitable, phenomenologically allowed Peccei-Quinn scale is simply and elegantly solved by the warping. In compactifications with two or more throats it is possible to simultaneously solve the Standard Model hierarchy problem by the Randall-Sundrum mechanism while implementing interesting warped axion models. The constructions discussed are related to holographic duals of previously studied models of composite axions arising from strongly coupled four-dimensional dynamics.

Abstract:

We present an argument in which the scale ~ 0.1 eV associated with neutrino masses naturally appears in a a class of (very) large volume compactifications, being tied to a supersymmetry scale of 10^3 GeV and a string scale of 10^11 GeV. The masses are of Majorana type and there is no right-handed neutrino within the low-energy field theory. The suppression scale 10^14 GeV is independent of the masses of the heavy states that are integrated out. These kind of constructions appear naturally in Type IIB flux compactifications. However, the arguments that lead to this result rely only on a few geometrical features of the compactification manifold, and hence can be used independently of string theory.

Abstract:

This article represents the author's PhD thesis. It describes moduli stabilisation in IIB string theory and applications to phenomenological topics. The first half of the thesis starts with an introductory review. It continues with an account of the statistics of complex structure moduli stabilisation before moving to Kahler moduli stabilisation. It describes in detail the large-volumes models and justifies the assumptions used in their construction. The second half of the thesis is concerned with applications to phenomenological topics. These include supersymmetry breaking and soft terms, inflationary model building and axions.