889 research outputs found
Maximal Sfermion Flavor Violation in Super-GUTs
We consider supersymmetric grand unified theories with soft
supersymmetry-breaking scalar masses specified above the GUT scale
(super-GUTs) and patterns of Yukawa couplings motivated by upper limits on
flavour-changing interactions beyond the Standard Model. If the scalar masses
are smaller than the gaugino masses , as is expected in no-scale
models, the dominant effects of renormalization between the input scale and the
GUT scale are generally expected to be those due to the gauge couplings, which
are proportional to and generation-independent. In this case, the
input scalar masses may violate flavour maximally, a scenario we call
MaxSFV, and there is no supersymmetric flavour problem. We illustrate this
possibility within various specific super-GUT scenarios that are deformations
of no-scale gravity.Comment: 38 pp, 16 figures. Change of title to describe better the scope of
the work, minor comments added, one reference added, matches published
versio
Tracking down the route to the SM with inflation and gravitational waves
We explore supersymmetric SO(10) models predicting observable proton decay and various topological defects which produce different shapes and strengths of gravitational wave backgrounds depending on the scales of intermediate symmetry breaking and inflation as well. We compare these to their nonsupersymmetric counterparts. By identifying the scales at which gravitational wave signals appear, we would be able to track down a particular breaking chain and discern if it has a supersymmetric origin or not. It would also be useful to observe gravitational waves from more than one source among all possible topological defects and first order phase transitions for a realistic breaking chain. For these purposes, we work out specific examples in which the grand unification and relevant intermediate scales are calculable explicitly. It turns out that examples with gravitational waves from different sources are quite difficult to obtain, and the predicted gravitational wave profiles from domain walls and first order phase transitions obtained in some examples will require detectors in the kHz to MHz region.publishedVersio
Swampland de Sitter conjectures in no-scale supergravity models
It is challenging to construct explicit and controllable models that realize de Sitter solutions in string compactifications. This difficulty is the main motivation for the refined de Sitter conjecture and the trans-Planckian censorship conjecture which forbid stable de Sitter solutions but allow metastable, unstable and rolling solutions in a theory consistent with quantum gravity. Inspired by this, we first study a toy de Sitter no-scale supergravity model and show that for particular choices of parameters it can be consistent with the refined de Sitter conjecture and the trans-Planckian censorship conjecture. Then we modify the model by adding rolling dynamics and show that the theory can become stable along the imaginary direction, where it would otherwise be unstable. We extend the model to multifield rolling and de Sitter fields, finding the parameter space where they can be compatible with the refined de Sitter conjecture. The modified models with rolling fields can be used to construct quintessence models to accommodate the accelerating expansion of the Universe.publishedVersio
Supersymmetric Musings on the Predictivity of Family Symmetries
We discuss the predictivity of family symmetries for the soft supersymmetry
breaking parameters in the framework of supergravity. We show that unknown
details of the messenger sector and the supersymmetry breaking hidden sector
enter into the soft parameters, making it difficult to obtain robust
predictions. We find that there are specific choices of messenger fields which
can improve the predictivity for the soft parameters.Comment: 20 pages, 5 figure
Flavour issues for string-motivated heavy scalar spectra with a low gluino mass: the G2-MSSM case
In recent years it has been learned that scalar superpartner masses and
trilinear couplings should both generically be larger than about 20 TeV at the
short distance string scale if our world is described by a compactified string
or M-theory with supersymmetry breaking and stabilized moduli. Here we study
implications of this, somewhat generally and also in detail for a particular
realization (compactification of M-theory on a G_2 manifold) where there is
significant knowledge of the superpotential and gauge kinetic function, and a
light gluino. In a certain sense this yields an ultraviolet completion of
minimal flavour violation. Flavour violation stems from off-diagonal and
non-universal diagonal elements of scalar mass matrices and trilinear
couplings, and from renormalization group running. We also examine stability
bounds on the scalar potential. While heavy scalars alone do not guarantee the
absence of flavour problems, our studies show that models with heavy scalars
and light gluinos can be free from such problems.Comment: 22 pages + references, 5 figures; v2: corrected calculation of
epsilon_K (SUSY contribution is always harmless), improved presentation,
added references; v3: further minor improvements, matches version to appear
in EPJ
Understanding the correlation between and in the MSSM
The supersymmetric contributions to the muon anomalous magnetic moment
and to the decay are given by very similar Feynman
diagrams. Previous works reported correlations in specific scenarios, in
particular if is dominated by a single diagram. In this work we give an
extensive survey of the possible correlations. We discuss examples of
single-diagram domination with particularly strong correlations, and provide
corresponding benchmark parameter points. We show how the correlations are
weakened by significant cancellations between diagrams in large parts of the
MSSM parameter space. Nevertheless, the order of magnitude of for a fixed flavor-violating parameter can often be predicted.
We summarize the behavior by plotting the correlations as well as resulting
bounds on the flavor-violating parameters under various assumptions on the MSSM
spectrum.Comment: 30 pages, 16 figures. v2 matches published version: modified two
figures for clarification, corrected typos and clarified parts of the text,
added reference
Late-time Cosmology without Dark Sector but with Closed String Massless Sector
We propose to solve the dark energy problem by postulating the massless
sector of closed strings. This sector constitutes the gravitational multiplet
of string theory and, when applied to four-dimensional cosmology, predicts that
the expansion of an open Universe defined in string frame is readily
accelerating. We confront the prediction with the late-time cosmological data
of Type Ia supernovae and quasar absorption spectrum, which probe the
evolutions of the Hubble parameter and possibly the fine-structure constant. We
report that the observations are in admirable agreement with the prediction
without any dark sector. We estimate the Hubble constant, .Comment: 8+9 pages, 5+8 figure
Quantifying Limits on CP Violating Phases from EDMs in Supersymmetry
We revisit the calculation of the electron, neutron, and proton electric
dipole moments (EDMs) in the constrained minimal supersymmetric standard model
(CMSSM). The relatively large mass of the Higgs boson, GeV
coupled with the (as yet) lack of discovery of any supersymmetric particle at
the LHC, has pushed the supersymmetry breaking scale to several TeV or higher.
Though one might expect this decoupling to have relaxed completely any bounds
on the two CP violating phases in the CMSSM ( and ), the
impressive experimental improvements in the limits on the EDMs (particularly
the electron EDM) still allow us to set constraints of order
on and on . We also discuss the
impact of future improvements in the experimental limits on supersymmetric
models.Comment: 34 pages, 8 figure
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