100 research outputs found
Non-geometric fluxes as supergravity backgrounds
We consider examples of D=4 string theory vacua which, although globally
non-geometric, admit a local description in terms of D=10 supergravity
backgrounds. We analyze such backgrounds and find that the supersymmetry
spinors vary non-trivially along the internal manifold, reproducing the
interpolating supergravity solutions found by Frey and Grana. Finally, we
propose a simple, local expression for non-geometric fluxes in terms of the
internal spinors of the compactification.Comment: 5 pages. Further typos correcte
Non-perturbative effects on seven-brane Yukawa couplings
We analyze non-perturbative corrections to the superpotential of seven-brane
gauge theories on type IIB and F-theory warped Calabi-Yau compactifications. We
show in particular that such corrections modify the holomorphic Yukawa
couplings by an exponentially suppressed contribution, generically solving the
Yukawa rank-one problem present in F-theory local models. We provide explicit
expressions for the non-perturbative correction to the seven-brane
superpotential, and check that it is related to a non-commutative deformation
to the tree-level superpotential via the Seiberg-Witten map.Comment: 4 pages. v2: minor changes, footnotes and citations added. Version to
be published in PR
Type IIA Flux Vacua and -corrections
We analyse type IIA Calabi-Yau orientifolds with backgroud fluxes, taking
into account the effect of perturbative -corrections. In particular,
we consider the -corrections that modify the metrics in the K\"ahler
sector of the compactification. As it has been argued in the literature,
including such -corrections allows to construct the mirror duals of
type IIB Calabi-Yau flux compactifications, in which the effect of flux
backreaction is under control. We compute the -corrected scalar
potential generated by the presence of RR and NS fluxes, and reformulate it as
a bilinear of the flux-axion polynomials invariant under the discrete shift
symmetries of the compactification. The use of such invariants allows to
express in a compact and simple manner the conditions for Minkowski and AdS
flux vacua, and to extract the effect of -corrections on them.Comment: 40 pages, typos corrected and references adde
U(1) mixing and D-brane linear equivalence
Linear equivalence is a criterion that compares submanifolds in the same
homology class. We show that, in the context of type II compactifications with
D-branes, this concept translates to the kinetic mixing between U(1) gauge
symmetries arising in the open and closed string sectors. We argue that in
generic D-brane models such mixing is experimentally detectable through the
existence of milli-charged particles. We compute these gauge kinetic functions
by classifying the 4d monopoles of a compactification and analyzing the Witten
effect on them, finding agreement with previous results and extending them to
more general setups. In particular, we compute the gauge kinetic functions
mixing bulk and magnetized D-brane U(1)'s and derive a generalization of linear
equivalence for these objects. Finally, we apply our findings to F-theory SU(5)
models with hypercharge flux breaking.Comment: 43 pages+appendices, 1 figure; v2: typos corrected and references
adde
Challenges for D-brane large-field inflation with stabilizer fields
We study possible string theory compactifications which, in the low-energy
limit, describe chaotic inflation with a stabilizer field. We first analyze
type IIA setups where the inflationary potential arises from a D6-brane
wrapping an internal three-cycle, and where the stabilizer field is either an
open-string or bulk K\"ahler modulus. We find that after integrating out the
relevant closed-string moduli consistently, tachyonic directions arise during
inflation which cannot be lifted. This is ultimately due to the shift
symmetries of the type IIA K\"ahler potential at large compactification volume.
This motivates us to search for stabilizer candidates in the complex structure
sector of type IIB orientifolds, since these fields couple to D7-brane Wilson
lines and their shift symmetries are generically broken away from the large
complex structure limit. However, we find that in these setups the challenge is
to obtain the necessary hierarchy between the inflationary and Kaluza-Klein
scales.Comment: 26 pages, typos corrected and comments added. Published versio
Open string multi-branched and Kahler potentials
We consider type II string compactifications on Calabi-Yau orientifolds with
fluxes and D-branes, and analyse the F-term scalar potential that
simultaneously involves closed and open string modes. In type IIA models with
D6-branes such potential can be directly computed by integrating out Minkowski
three-forms. The result shows a multi-branched structure along the space of
lifted open string moduli, in which discrete shifts in special Lagrangian and
Wilson line deformations are compensated by changes in the RR flux quanta. The
same sort of discrete shift symmetries are present in the superpotential and
constrain the Kahler potential. As for the latter, inclusion of open string
moduli breaks the factorisation between complex structure and Kahler moduli
spaces. Nevertheless, the 4d Kahler metrics display a set of interesting
relations that allow to rederive the scalar potential analytically. Similar
results hold for type IIB flux compactifications with D7-brane Wilson lines.Comment: 60 pages, one figure. v2 minor corrections and references adde
Generalized non-supersymmetric flux vacua
We discuss a novel strategy to construct 4D N=0 stable flux vacua of type II
string theory, based on the existence of BPS bounds for probe D-branes in some
of these backgrounds. In particular, we consider compactifications where
D-branes filling the 4D space-time obey the same BPS bound as they would in an
N=1 compactification, while other D-branes, like those appearing as domain
walls from the 4D perspective, can no longer be BPS. We construct a subfamily
of such backgrounds giving rise to 4D N=0 Minkowski no-scale vacua,
generalizing the well-known case of type IIB on a warped Calabi-Yau. We provide
several explicit examples of these constructions, and compute quantities of
phenomenological interest like flux-induced soft terms on D-branes. Our results
have a natural, simple description in the language of Generalized Complex
Geometry, and in particular in terms of D-brane generalized calibrations.
Finally, we extend the integrability theorems for 10D supersymmetric type II
backgrounds to the N=0 case and use the results to construct a new class of N=0
AdS4 compactifications.Comment: 95 pages, minor change
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