307 research outputs found
D-brane instantons and the effective field theory of flux compactifications
We provide a description of the effects of fluxes on euclidean D-brane
instantons purely in terms of the 4d effective action. The effect corresponds
to the dressing of the effective non-perturbative 4d effective vertex with 4d
flux superpotential interactions, generated when the moduli fields made massive
by the flux are integrated out. The description in terms of effective field
theory allows a unified description of non-perturbative effects in all flux
compactifications of a given underlying fluxless model, globally in the moduli
space of the latter. It also allows us to describe explicitly the effects on
D-brane instantons of fluxes with no microscopic description, like
non-geometric fluxes. At the more formal level, the description has interesting
connections with the bulk-boundary map of open-closed two-dimensional
topological string theory, and with the \NN=1 special geometry.Comment: 33 page
Four-modulus "Swiss Cheese" chiral models
We study the 'Large Volume Scenario' on explicit, new, compact, four-modulus
Calabi-Yau manifolds. We pay special attention to the chirality problem pointed
out by Blumenhagen, Moster and Plauschinn. Namely, we thoroughly analyze the
possibility of generating neutral, non-perturbative superpotentials from
Euclidean D3-branes in the presence of chirally intersecting D7-branes. We find
that taking proper account of the Freed-Witten anomaly on non-spin cycles and
of the Kaehler cone conditions imposes severe constraints on the models.
Nevertheless, we are able to create setups where the constraints are solved,
and up to three moduli are stabilized.Comment: 40 pages, 10 figures, clarifying comments added, minor mistakes
correcte
FIELD TRIP TO THE YPRESIAN/LUTETIAN BOUNDARY AT THE GORRONDATXE BEACH SECTION (BASQUE COUNTRY, W PYRENEES)
One of the Paleogene Stage boundaries still needing official definition is the Ypresian/Lutetain (Early-
Middle Eocene) boundary. With the aim of contributing to attain this definition, a high-resolution multidisciplinary
study, including physical stratigraphy (lithostratigraphy, sequence stratigraphy and
magnetostratigraphy) and biostratigraphy (calcareous nannofossil, planktic foraminifer and larger
foraminifer), has been carried out over the 700 m thick uppermost Ypresian – lower Lutetian Gorrondatxe
section. The results show that the different events traditionally used to place the Ypresian/Lutetian
boundary, hitherto thought to be simultaneous (i.e., the planktic foraminifer P9 (=E7) / P10 (=E8) Zone
boundary; the calcareous nannofossil CP12a / CP12b Subzone boundary; the larger foraminifer SBZ12 /
SBZ13 Zone boundary; and the boundary between magnetic polarity chrons C22n and C21r), actually
occur at very different levels. Therefore, before considering any section to place the Ypresian/Lutetian
boundary stratotype, the criterion to precisely define this boundary should be selected. To this end, the
succession of events pinpointed in the Ypresian/Lutetian boundary interval of the Gorrondatxe beach
section might prove a useful database.
The Gorrondatxe section fulfils most of the requirements demanded of a prospective stratotype section. In
addition, the great sedimentary thickness, which implies a very high deep-marine sedimentation rate,
provides the Gorrondatxe section an additional value, as it offers the opportunity to chronologically order
successive biomagnetostratigraphic events more precisely than elsewhere. Therefore, we consider that,
once the criterion to define the Ypresian/Lutetian boundary is selected, the Gorrondatxe beach section
should be deemed a firm candidate to place the Global Stratotype Section and Point of the base of the
Lutetian Stage
Cyclostratigraphy of the Early/Middle Eocene transition: a Pyrenean perspective
An integrated bio-, magneto- and cyclostratigraphic study of the Ypresian/Lutetian (Early/Middle Eocene)
transition along the Pyrenean Otsakar section (Payros et al., 2011) resulted in the identification of the
C22n/C21r chron boundary and of the calcareous nannofossil CP12a/b zonal boundary; the latter is the
main correlation criterion of the Lutetian Global Stratotype Section and Point (GSSP) recently defined
at Gorrondatxe (Basque Country). By counting precession-related mudstone-marl couplets of 21 ka,
the time lapse between both events was calculated to be of 819 ka. This suggests that the age of the
CP12a/b boundary, and hence that of the Early/Middle Eocene boundary, is 47.76 Ma, 250 ka younger
than previously thought. This age agrees with, and is supported by, estimates from Gorrondatxe based
on the time lapse between the Lutetian GSSP and the C21r/C21n boundary. The duration of Chron
C21r is estimated at 1.326 Ma. Given that the base of the Eocene is dated at 55.8 Ma, the duration of
the Early Eocene is of 8 Ma, 0.8 Ma longer than in current time scales. The Otsakar results further show
that the bases of planktic foraminiferal zones E8 and P10 are younger than the CP12a/b boundary. The
first occurrence of Turborotalia frontosa, being approximately 550 ka older that the CP12a/b boundary,
is the planktic foraminiferal event that lies closest to the Early/Middle Eocene boundary. The larger
foraminiferal SBZ12/13 boundary is located close to the CP12a/b boundary and correlates with Chron
C21r, not with the C22n/C21r boundary
SU(5) D-brane realizations, Yukawa couplings and proton stability
We discuss SU(5) Grand Unified Theories in the context of orientifold
compactifications. Specifically, we investigate two and three D-brane stack
realizations of the Georgi-Glashow and the flipped SU(5) model and analyze them
with respect to their Yukawa couplings. As pointed out in arXiv:0909.0271 the
most economical Georgi-Glashow realization based on two stacks generically
suffers from a disastrous large proton decay rate. We show that allowing for an
additional U(1) D-brane stack this as well as other phenomenological problems
can be resolved. We exemplify with globally consistent Georgi-Glashow models
based on RCFT that these D-brane quivers can be indeed embedded in a global
setting. These globally consistent realizations admit rigid O(1) instantons
inducing the perturbatively missing coupling 10105^H. Finally we show that
flipped SU(5) D-brane realizations even with multiple U(1) D-brane stacks are
plagued by severe phenomenological drawbacks which generically cannot be
overcome.Comment: 34 pages v2 minor correction
D-brane Instantons as Gauge Instantons in Orientifolds of Chiral Quiver Theories
Systems of D3-branes at orientifold singularities can receive
non-perturbative D-brane instanton corrections, inducing field theory operators
in the 4d effective theory. In certain non-chiral examples, these systems have
been realized as the infrared endpoint of a Seiberg duality cascade, in which
the D-brane instanton effects arise from strong gauge theory dynamics. We
present the first UV duality cascade completion of chiral D3-brane theories, in
which the D-brane instantons arise from gauge theory dynamics. Chiral examples
are interesting because the instanton fermion zero mode sector is topologically
protected, and therefore lead to more robust setups. As an application of our
results, we provide a UV completion of certain D-brane orientifold systems
recently claimed to produce conformal field theories with conformal invariance
broken only by D-brane instantons.Comment: 50 pages, 32 figures. v2: version published in JHEP with references
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Toric AdS4/CFT3 duals and M-theory Crystals
We study the recently proposed crystal model for three dimensional
superconformal field theories arising from M2-branes probing toric Calabi-Yau
four-fold singularities. We explain the algorithms mapping a toric Calabi-Yau
to a crystal and vice versa, and show how the spectrum of BPS meson states fits
into the crystal model.Comment: 24 pages, 24 figure
Meta-Stable Brane Configurations by Adding an Orientifold-Plane to Giveon-Kutasov
In hep-th/0703135, they have found the type IIA intersecting brane
configuration where there exist three NS5-branes, D4-branes and anti-D4-branes.
By analyzing the gravitational interaction for the D4-branes in the background
of the NS5-branes, the phase structures in different regions of the parameter
space were studied in the context of classical string theory. In this paper, by
adding the orientifold 4-plane and 6-plane to the above brane configuration, we
describe the intersecting brane configurations of type IIA string theory
corresponding to the meta-stable nonsupersymmetric vacua of these gauge
theories.Comment: 21 pp, 6 figures; reduced bytes of figures, DBI action analysis added
and to appear in JHE
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