6 research outputs found
Type IIB orientifolds on Gepner points
We study various aspects of orientifold projections of Type IIB closed string
theory on Gepner points in different dimensions. The open string sector is
introduced, in the usual constructive way, in order to cancel RR charges
carried by orientifold planes. Moddings by cyclic permutations of the internal
N=2 superconformal blocks as well as by discrete phase symmetries are
implemented. Reduction in the number of generations, breaking or enhancements
of gauge symmetries and topology changes are shown to be induced by such
moddings. Antibranes sector is also considered; in particular we show how non
supersymmetric models with antibranes and free of closed and open tachyons do
appear in this context. A systematic study of consistent models in D=8
dimensions and some illustrative examples in D=6 and D=4 dimensions are
presented.Comment: 67 pages, no figures References added, typos correcte
Fluxbranes: Moduli Stabilisation and Inflation
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 eta-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.Comment: In section 3 an improved model is discusse