774 research outputs found
Lectures on Superstring Phenomenology
The phenomenological aspects of string theory are briefly reviewed. Emphasis
is given to the status of 4D string model building, effective Lagrangians,
model independent results, supersymmetry breaking and duality symmetries.Comment: 41 pages, latex, given at V Latin American Workshop on Particles and
Fields, Mexico, 1995 (typos corrected, a footnote changed and more references
added
On the Explicit Construction and Statistics of Calabi-Yau Flux Vacua
We explicitly construct and study the statistics of flux vacua for type IIB
string theory on an orientifold of the Calabi-Yau hypersurface
, parametrised by two relevant complex structure moduli. We
solve for these moduli and the dilaton field in terms of the set of integers
defining the 3-form fluxes and examine the distribution of vacua. We compare
our numerical results with the predictions of the Ashok-Douglas density , finding good overall agreement in different regions of moduli
space. The number of vacua are found to scale with the distance in flux space.
Vacua cluster in the region close to the conifold singularity. Large
supersymmetry breaking is more generic but supersymmetric and hierarchical
supersymmetry breaking vacua can also be obtained. In particular, the small
superpotentials and large dilaton VEVs needed to obtain de Sitter space in a
controllable approximation are possible but not generic. We argue that in a
general flux compactification, the rank of the gauge group coming from D3
branes could be statistically preferred to be very small.Comment: 26 pages, 9 figures; v2: references adde
De Sitter from T-branes
Hidden sector D7-branes with non-zero gauge flux are a generic feature of
type IIB compactifications. A non-vanishing Fayet-Iliopoulos term induced by
non-zero gauge flux leads to a T-brane configuration. Expanding the D7-brane
action around this T-brane background in the presence of three-form
supersymmetry breaking fluxes, we obtain a positive definite contribution to
the moduli scalar potential which can be used as an uplifting source for de
Sitter vacua. In this way we provide a higher-dimensional understanding of
known 4D mechanisms of de Sitter uplifting based on hidden sector F-terms which
are non-zero because of D-term stabilisation.Comment: 23 pages, 2 figure
Moduli Stabilisation with Nilpotent Goldstino: Vacuum Structure and SUSY Breaking
We study the effective field theory of KKLT and LVS moduli stabilisation
scenarios coupled to an anti-D3-brane at the tip of a warped throat. We
describe the presence of the anti-brane in terms of a nilpotent goldstino
superfield in a supersymmetric effective field theory. The introduction of this
superfield produces a term that can lead to a de Sitter minimum. We fix the
Kaehler moduli dependence of the nilpotent field couplings by matching this
term with the anti-D3-brane uplifting contribution. The main result of this
paper is the computation, within this EFT, of the soft supersymmetry breaking
terms in both KKLT and LVS for matter living on D3-brane (leaving the D7-brane
analysis to an appendix). A handful of distinct phenomenological scenarios
emerge that could have low energy implications, most of them having a split
spectrum of soft masses. Some cosmological and phenomenological properties of
these models are discussed. We also check that the attraction between the
D3-brane and the anti-D3-brane does not affect the leading contribution to the
soft masses and does not destabilise the system.Comment: 26+14 pages, 1 figure; references and clarifications added, typos
fixe
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