Particle theory

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.

Abstract:

We reduce M theory on a G2 orbifold with codimension four singularities, taking explicitly into account the additional gauge fields at the singularities. As a starting point, we use 11-dimensional supergravity coupled to seven-dimensional super-Yang-Mills theory, as derived in a previous paper. The resulting four-dimensional theory has N=1 supersymmetry with non-Abelian N=4 gauge theory subsectors. We present explicit formulas for the Kähler potential, gauge-kinetic function and superpotential. In the four-dimensional theory, blowing up of the orbifold is described by a Higgs effect induced by continuation along D-flat directions. Using this interpretation, we show that our results are consistent with the corresponding ones obtained for smooth G2 spaces. In addition, we consider the effects of switching on flux and Wilson lines on singular loci of the G2 space, and we discuss the relation to N=4 super-Yang-Mills theory. © 2006 The American Physical Society.