169 research outputs found
A Next-to-Minimal Supersymmetric Model of Hybrid Inflation
We propose a model of inflation based on a simple variant of the NMSSM,
called NMSSM, where the additional singlet plays the role of the
inflaton in hybrid (or inverted hybrid) type models. As in the original NMSSM,
the NMSSM solves the problem of the MSSM via the VEV of a gauge
singlet , but unlike the NMSSM does not suffer from domain wall problems
since the offending symmetry is replaced by an approximate Peccei-Quinn
symmetry which also solves the strong CP problem, and leads to an invisible
axion with interesting cosmological consequences. The PQ symmetry may arise
from a superstring model with an exact discrete symmetry after
compactification. The model predicts a spectral index to one part in
.Comment: 17 pages, Latex; note added, accepted for Phys. Lett.
F-term Hybrid Inflation in Effective Supergravity Theories
We show that the effective low energy supergravity theories which result from a generic string theory can provide a promising framework for models of hybrid inflation in which the potential energy which drives inflation originates from the F-term of the effective supergravity theory. In the class of models considered the inflaton is protected from receiving mass during inflation by a Heisenberg symmetry and the potential during inflation takes the positive definite form , which allows the possibility that . We discuss a toy example where this is realised, then describe the application of this result to realistic models focusing on a particular example in which the problem and the strong CP-problem are addressed
Leptogenesis in a Realistic Supersymmetric Model of Inflation with a Low Reheat Temperature
We discuss leptogenesis in a realistic supersymmetric model of inflation with
a low reheat temperature 1-10 GeV. The lepton asymmetry is generated by a
decaying right handed sneutrino, which is produced after inflation during
preheating. The inflationary model is based on a simple variant of the
Next-to-Minimal Supersymmetric Standard model (NMSSM) which solves the \mu
problem, called \phiNMSSM, where the additional singlet \phi plays the role of
the inflaton in hybrid (or inverted hybrid) type models. The model is invariant
under an approximate Peccei-Quinn symmetry which also solves the strong CP
problem, and leads to an invisible axion with interesting cosmological
consequences. We show how the baryon number of the universe and the nature of
cold dark matter are determined by the same parameters controlling the strong
CP problem, the \mu problem and the neutrino masses and mixing angles.Comment: 17 page, latex, 1 eps fi
Preheating in Supersymmetric Hybrid Inflation
We study preheating in a general class of supersymmetric hybrid inflation
model. Supersymmetry leads to only one coupling constant in the potential and
thus only one natural frequency of oscillation for the homogeneous fields,
whose classical evolution consequently differs from that of a general
(non-supersymmetric) hybrid model. We emphasise the importance of mixing
effects in these models which can significantly change the rate of production
of particles. We perform a general study of the rate of production of the
particles associated with the homogeneous fields, and show how preheating is
efficient in producing these quanta. Preheating of other particle species will
be model dependent, and in order to investigate this we consider a realistic
working model of supersymmetric hybrid inflation which solves the strong-CP
problem via an approximate Peccei-Quinn symmetry, which was proposed by us
previously. We study axion production in this model and show that properly
taking into account the mixing between the fields suppresses the axion
production, yet enhances the production of other particles. Finally we
demonstrate the importance of backreaction effects in this model which have the
effect of shutting off axion production, leaving the axion safely within
experimental bounds.Comment: 37 pages, Latex, 11 eps figures, 14 ps (colour) figure
Directional detection of meV dark photons with Dandelion
This paper presents Dandelion, a new dish antenna experiment searching for
dark photons (DPs) with masses around the meV that will start acquiring data by
the end of 2023. A spherical mirror acts as a conversion surface between DPs
and standard photons that converge to a matrix of 418 Kinetic Inductance
Detectors cooled down to 150 mK. A tilt of the mirror at 1 Hz moves the
expected signal over the pixels thus enabling a continuous background
measurement. The expected signal has two modulations: a spatial modulation
providing a directional signature for the unambiguous discovery of a DP, and an
intensity modulation allowing the determination of the polarization of the DP.
For masses near the meV, the inflationary production of longitudinal and
transverse DPs are mutually excluded, thus the polarization determination by
Dandelion could shed a new light on the inflation phase of the early universe.
A first Dandelion prototype operating for 30 days would improve by more than
one order of magnitude the current exclusion limits on DPs at the meV mass
scale and would probe this region with an unprecedented discovery potential
based on directional detection.Comment: 17 pages, 7 figure
Palatini versus metric formulation in higher curvature gravity
We compare the metric and the Palatini formalism to obtain the Einstein
equations in the presence of higher-order curvature corrections that consist of
contractions of the Riemann tensor, but not of its derivatives. We find that
there is a class of theories for which the two formalisms are equivalent. This
class contains the Palatini version of Lovelock theory, but also more
Lagrangians that are not Lovelock, but respect certain symmetries. For the
general case, we find that imposing the Levi-Civita connection as an Ansatz,
the Palatini formalism is contained within the metric formalism, in the sense
that any solution of the former also appears as a solution of the latter, but
not necessarily the other way around. Finally we give the conditions the
solutions of the metric equations should satisfy in order to solve the Palatini
equations.Comment: 13 pages, latex. V2: reference added, major changes in section 3,
conclusions partially correcte
A solution to the mu problem in the presence of a heavy gluino LSP
In this paper we present a solution to the problem in an SO(10)
supersymmetric grand unified model with gauge mediated and D-term supersymmetry
breaking. A Peccei-Quinn symmetry is broken at the messenger scale GeV and enables the generation of the term. The boundary
conditions defined at lead to a phenomenologically acceptable version of
the minimal supersymmetric standard model with novel particle phenomenology.
Either the gluino or the gravitino is the lightest supersymmetric particle
(LSP). If the gravitino is the LSP, then the gluino is the next-to-LSP (NLSP)
with a lifetime on the order of one month or longer. In either case this heavy
gluino, with mass in the range 25 - 35 GeV, can be treated as a stable particle
with respect to experiments at high energy accelerators. Given the extensive
phenomenological constraints we show that the model can only survive in a
narrow region of parameter space resulting in a light neutral Higgs with mass
GeV and . In addition the lightest stop
and neutralino have mass GeV and GeV,
respectively. Thus the model will soon be tested. Finally, the invisible axion
resulting from PQ symmetry breaking is a cold dark matter candidate.Comment: 30 pages, 9 figure
Quantum back-reaction of the superpartners in a large-N supersymmetric hybrid model
We study the supersymmetric hybrid model near and after the end of inflation.
As usual, we reduce the model to a purely scalar hybrid model on the level of
the classical fields. But on the level of quantum fluctuations and their
backreaction we take into account all superpartners of the waterfall field in a
large-N approximation. The evolution after slow roll displays two phases with a
different characteristic behaviour of the classical and fluctuation fields. We
find that the fluctuations of the pseudoscalar superpartner are of particular
importance in the late time phase. The motion of the waterfall field towards
its classical expectation value is found to be very slow and suggests a rather
flat potential and a stochastic force.Comment: 37 pages 19 figure
Naturalness and Fine Tuning in the NMSSM: Implications of Early LHC Results
We study the fine tuning in the parameter space of the semi-constrained
NMSSM, where most soft Susy breaking parameters are universal at the GUT scale.
We discuss the dependence of the fine tuning on the soft Susy breaking
parameters M_1/2 and m0, and on the Higgs masses in NMSSM specific scenarios
involving large singlet-doublet Higgs mixing or dominant Higgs-to-Higgs decays.
Whereas these latter scenarios allow a priori for considerably less fine tuning
than the constrained MSSM, the early LHC results rule out a large part of the
parameter space of the semi-constrained NMSSM corresponding to low values of
the fine tuning.Comment: 19 pages, 10 figures, bounds from Susy searches with ~1/fb include
- …