### Contents

, 2013

"... We investigate viable scenarios with various axions in the context of super-symmetric field theory and in globally consistent D-brane models. The Peccei-Quinn symmetry is associated with an anomalous U(1) symmetry, which ac-quires mass at the string scale but remains as a perturbative global symmetr ..."

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We investigate viable scenarios with various axions in the context of super-symmetric field theory and in globally consistent D-brane models. The Peccei-Quinn symmetry is associated with an anomalous U(1) symmetry, which ac-quires mass at the string scale but remains as a perturbative global symmetry at low energies. The origin of the scalar Higgs-axion potential from F-, D- and soft breaking terms is derived, and two Standard Model examples of global in-tersecting D6-brane models in Type II orientifolds are presented, which differ in the realisation of the Higgs sector and in the hidden sector, the latter of which is of particluar importance for the soft supersymmetry breaking terms. ar X iv

### LMU-ASC 47/12 Fluxbranes: Moduli Stabilisation and Inflation

, 2012

"... Abstract: Fluxbrane inflation is a stringy version of D-term inflation in which two fluxed D7-branes move towards each other until their (relative) gauge flux annihilates. Compared to brane-antibrane inflation, the leading-order inflationary potential of this scenario is much flatter. In the present ..."

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Abstract: Fluxbrane inflation is a stringy version of D-term inflation in which two fluxed D7-branes move towards each other until their (relative) gauge flux annihilates. Compared to brane-antibrane inflation, the leading-order inflationary potential of this scenario is much flatter. In the present paper we first discuss a new explicit moduli stabilisation procedure combining the F- and D-term scalar potentials: It is based on fluxed D7-branes in a geometry with three large four-cycles of hierarchically different volumes. Subsequently, we combine this moduli stabilisation with the fluxbrane inflation idea, demonstrating in particular that CMB data (including cosmic string constraints) can be explained within our setup of hierarchical large volume CY compactifications. We also indicate how the η-problem is expected to re-emerge through higher-order corrections and how it might be overcome by further refinements of our model. Finally, we explain why recently raised concerns about constant FI terms do not affect the consistent, string-derived variant of D-term inflation discussed in this paper.