127 research outputs found
Six-dimensional D_N theory and four-dimensional SO-USp quivers
We realize four-dimensional N=2 superconformal quiver gauge theories with
alternating SO and USp gauge groups as compactifications of the six-dimensional
D_N theory with defects. The construction can be used to analyze infinitely
strongly-coupled limits and S-dualities of such gauge theories, resulting in a
new class of isolated four-dimensional N=2 superconformal field theories with
SO(2N)^3 flavor symmetry.Comment: 30 pages, 12 figures; v2: published versio
The Standard Model quiver in de Sitter string compactifications
We argue that the Standard Model quiver can be embedded into compact Calabi-Yau geometries through orientifolded D3-branes at del Pezzo singularities dPn with n â„ 5 in a framework including moduli stabilisation. To illustrate our approach, we explicitly construct a local dP5 model via a combination of Higgsing and orientifolding. This procedure reduces the original dP5 quiver gauge theory to the Left-Right symmetric model with three families of quarks and leptons as well as a Higgs sector to further break the symmetries to the Standard Model gauge group. We embed this local model in a globally consistent Calabi-Yau flux compactification with tadpole and Freed-Witten anomaly cancellations. The model features closed string moduli stabilisation with a de Sitter minimum from T-branes, supersymmetry broken by the KĂ€hler moduli, and the MSSM as the low energy spectrum. We further discuss phenomenological and cosmological implications of this construction
A natural renormalizable model of metastable SUSY breaking
We propose a model of metastable dynamical supersymmetry breaking in which
all scales are generated dynamically. Our construction is a simple variant of
the Intriligator-Seiberg-Shih model, with quark masses induced by
renormalizable couplings to an auxiliary supersymmetric QCD sector. Since all
scales arise from dimensional transmutation, the model has no fundamental
dimensionful parameters. It also does not rely on higher-dimensional operators.Comment: 9 pages; v2: typos correcte
On 4d rank-one N=3 superconformal field theories
We study the properties of 4d N=3 superconformal field theories whose rank is
one, i.e. those that reduce to a single vector multiplet on their moduli space
of vacua. We find that the moduli space can only be of the form C^3/Z_k for
k=1,2,3,4,6, and that the supersymmetry automatically enhances to N=4 for
k=1,2. In addition, we determine the central charges a and c in terms of k, and
construct the associated 2d chiral algebras, which turn out to be exotic N=2
supersymmetric W-algebras.Comment: 24 page
Realistic Yukawa Structures from Orientifold Compactifications
We perform a systematic analysis of globally consistent D-brane quivers which
realize the MSSM, and analyze them with respect to their Yukawa couplings.
Often, desired couplings are perturbatively forbidden due to the presence of
global U(1) symmetries. We investigate the conditions under which D-brane
instantons will induce these missing couplings without generating other
phenomenological drawbacks, such as R-parity violating couplings or a mu-term
which is too large. Furthermore, we systematically analyze which quivers allow
for a mechanism that can account for the small neutrino masses and other
experimentally observed hierarchies. We show that only a small fraction of the
globally consistent D-brane quivers exhibits phenomenology compatible with
experimental observations.Comment: 42 pages, 3 figures. v2: R-parity constraints and Yukawa texture
analysis improved; typos corrected and references adde
Multifield Dynamics in Higgs-otic Inflation
In Higgs-otic inflation a complex neutral scalar combination of the and
MSSM Higgs fields plays the role of inflaton in a chaotic fashion. The
potential is protected from large trans-Planckian corrections at large inflaton
if the system is embedded in string theory so that the Higgs fields parametrize
a D-brane position. The inflaton potential is then given by a DBI+CS D-brane
action yielding an approximate linear behaviour at large field. The inflaton
scalar potential is a 2-field model with specific non-canonical kinetic terms.
Previous computations of the cosmological parameters (i.e. scalar and tensor
perturbations) did not take into account the full 2-field character of the
model, ignoring in particular the presence of isocurvature perturbations and
their coupling to the adiabatic modes. It is well known that for generic
2-field potentials such effects may significantly alter the observational
signatures of a given model. We perform a full analysis of adiabatic and
isocurvature perturbations in the Higgs-otic 2-field model. We show that the
predictivity of the model is increased compared to the adiabatic approximation.
Isocurvature perturbations moderately feed back into adiabatic fluctuations.
However, the isocurvature component is exponentially damped by the end of
inflation. The tensor to scalar ratio varies in a region ,
consistent with combined Planck/BICEP results.Comment: 35 pages, 11 figure
Transplanckian axions !?
We discuss quantum gravitational effects in Einstein theory coupled to
periodic axion scalars to analyze the viability of several proposals to achieve
superplanckian axion periods (aka decay constants) and their possible
application to large field inflation models. The effects we study correspond to
the nucleation of euclidean gravitational instantons charged under the axion,
and our results are essentially compatible with (but independent of) the Weak
Gravity Conjecture, as follows: Single axion theories with superplanckian
periods contain gravitational instantons inducing sizable higher harmonics in
the axion potential, which spoil superplanckian inflaton field range. A similar
result holds for multi-axion models with lattice alignment (like the
Kim-Nilles-Peloso model). Finally, theories with axions can still achieve a
moderately superplanckian periodicity (by a factor) with no higher
harmonics in the axion potential. The Weak Gravity Conjecture fails to hold in
this case due to the absence of some instantons, which are forbidden by a
discrete gauge symmetry. Finally we discuss the realization of
these instantons as euclidean D-branes in string compactifications.Comment: 46 pages, 6 figures. Added references, clarifications, and missing
factor of 1/2 to instanton action. Conclusions unchange
Yukawa hierarchies at the point of in F-theory
We analyse the structure of Yukawa couplings in local SU(5) F-theory models
with enhancement. In this setting the symmetry is broken down to
SU(5) by a 7-brane configuration described by T-branes, all the Yukawa
couplings are generated in the vicinity of a point and only one family of
quarks and leptons is massive at tree-level. The other two families obtain
their masses when non-perturbative effects are taken into account, being
hierarchically lighter than the third family. However, and contrary to previous
results, we find that this hierarchy of fermion masses is not always
appropriate to reproduce measured data. We find instead that different T-brane
configurations breaking to SU(5) give rise to distinct hierarchical
patterns for the holomorphic Yukawa couplings. Only some of these patterns
allow to fit the observed fermion masses with reasonable local model parameter
values, adding further constraints to the construction of F-theory GUTs. We
consider an model where such appropriate hierarchy is realised and
compute its physical Yukawas, showing that realistic charged fermions masses
can indeed be obtained in this case.Comment: 46 pages + appendices, 5 figures. v2, added references and typos
corrected, version accepted on JHEP. v3, typos correcte
Dimers, orientifolds and anomalies
We study 4dN = 1 gauge theories engineered via D-branes at orientifolds of toric singularities, where gauge anomalies are cancelled without the introduction of non-compact flavor branes. Using dimer model techniques, we derive geometric criteria for establishing whether a given singularity can admit anomaly-free D-brane configurations purely based on its toric data and the type of orientifold projection. Our results therefore extend the dictionary between geometric properties of singularities and physical properties of the corresponding gauge theories
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