3,956 research outputs found
MSSM soft terms from supergravity with gauged R-symmetry in de Sitter vacuum
We work out the phenomenology of a model of supersymmetry breaking in the
presence of a tiny (tunable) positive cosmological constant, proposed by the
authors in arXiv:1403.1534. It utilises a single chiral multiplet with a gauged
shift symmetry, that can be identified with the string dilaton (or an
appropriate compactification modulus). The model is coupled to the MSSM,
leading to calculable soft supersymmetry breaking masses and a distinct low
energy phenomenology that allows to differentiate it from other models of
supersymmetry breaking and mediation mechanisms
Inflation from Supersymmetry Breaking
We explore the possibility that inflation is driven by supersymmetry breaking
with the superpartner of the goldstino (sgoldstino) playing the role of the
inflaton. Moreover, we impose an R-symmetry that allows to satisfy easily the
slow-roll conditions, avoiding the so-called -problem, and leads to two
different classes of small field inflation models; they are characterised by an
inflationary plateau around the maximum of the scalar potential, where
R-symmetry is either restored or spontaneously broken, with the inflaton
rolling down to a minimum describing the present phase of our Universe. To
avoid the Goldstone boson and remain with a single (real) scalar field (the
inflaton), R-symmetry is gauged with the corresponding gauge boson becoming
massive. This framework generalises a model studied recently by the present
authors, with the inflaton identified by the string dilaton and R-symmetry
together with supersymmetry restored at weak coupling, at infinity of the
dilaton potential. The presence of the D-term allows a tuning of the vacuum
energy at the minimum. The proposed models agree with cosmological observations
and predict a tensor-to-scalar ratio of primordial perturbations
and an inflation scale GeV
GeV. may be lowered up to electroweak
energies only at the expense of fine-tuning the scalar potential.Comment: 29 pages, 8 figure
Inflation from Supergravity with Gauged R-symmetry in de Sitter Vacuum
We study the cosmology of a recent model of supersymmetry breaking, in the
presence of a tuneable positive cosmological constant, based on a gauged shift
symmetry of a string modulus that can be identified with the string dilaton.
The minimal spectrum of the `hidden' supersymmetry breaking sector consists
then of a vector multiplet that gauges the shift symmetry of the dilaton
multiplet and when coupled to the MSSM leads to a distinct low energy
phenomenology depending on one parameter. Here we study the question if this
model can also lead to inflation by identifying the dilaton with the inflaton.
We find that this is possible if the K\"ahler potential is modified by a term
that has the form of NS5-brane instantons, leading to an appropriate
inflationary plateau around the maximum of the scalar potential, depending on
two extra parameters. This model is consistent with present cosmological
observations without modifying the low energy particle phenomenology associated
to the minimum of the scalar potential.Comment: 19 pages, 5 figures, References adde
A microscopic model for inflation from supersymmetry breaking
We have proposed recently a framework for inflation driven by supersymmetry
breaking with the inflaton being a superpartner of the goldstino, that avoids
the main problems of supergravity inflation, allowing for: naturally small
slow-roll parameters, small field initial conditions, absence of a
(pseudo)scalar companion of the inflation, and a nearby minimum with tuneable
cosmological constant. It contains a chiral multiplet charged under a gauged
R-symmetry which is restored at the maximum of the scalar potential with a
plateau where inflation takes place. The effective field theory relies on two
phenomenological parameters corresponding to corrections to the K\"ahler
potential up to second order around the origin. The first guarantees the
maximum at the origin and the second allows the tuning of the vacuum energy
between the F- and D-term contributions. Here, we provide a microscopic model
leading to the required effective theory. It is a Fayet-Iliopoulos model with
two charged chiral multiplets under a second U(1) R-symmetry coupled to
supergravity. In the Brout-Englert-Higgs phase of this U(1), the gauge field
becomes massive and can be integrated out in the limit of small supersymmetry
breaking scale. In this work, we perform this integration and we show that
there is a region of parameter space where the effective supergravity realises
our proposal of small field inflation from supersymmetry breaking consistently
with observations and with a minimum of tuneable energy that can describe the
present phase of our Universe.Comment: 39 pages, v2: typos corrected, references added, published versio
Phenomenological aspects of supergravity theories in de Sitter vacua
We introduce an supergravity model based on the gauged shift symmetry
of a single chiral multiplet, which can be identified with the string dilaton
or a compactification modulus. The model allows for a tunably small and
positive value of the cosmological constant. The gravitino mass parameter and
the dilaton Vacuum Expectation Value are separately tunable.
In a second part we analyze the quantum consistency of these models. Recent
work on anomalies in supergravity theories with Fayet-Iliopoulos terms was
extended, such that their results can be interpreted from a field-theoretic
point of view. We show that for certain values of the parameters the anomaly
cancellation conditions are inconsistent with a TeV gravitino mass.
In the third part the above model is used as a hidden sector for
supersymmetry breaking. In its minimal version, the model leads to tachyonic
scalar soft masses. This problem can however be circumvented by the
introduction of an extra Pol\'onyi-like hidden sector field, or by allowing for
non-canonical kinetic terms for the Standard Model fields, while maintaining
the desirable features of the model. The resulting low energy spectrum consists
of very light neutralinos, charginos and gluinos, while the squarks remain
heavy, with the exception of the stop squark which can be as light as 2 TeV.
Finally, we discus possibility that the shift symmetry is identified with
known global symmetries of the MSSM. The particular cases where this global
symmetry is Baryon minus Lepton number (), or , which contain the
known R-parity or matter parity of the MSSM, are analyzed in great detail. It
is shown that the phenomenology is similar to the above case where the MSSM
fields are inert, with the exception of the stop squark, which can be as light
as TeV.Comment: 160 pages, 14 figures, Ph.D. Thesi
- …