2,502 research outputs found
A No-Scale Framework for Sub-Planckian Physics
We propose a minimal model framework for physics below the Planck scale with
the following features: (i) it is based on no-scale supergravity, as favoured
in many string compactifications, (ii) it incorporates Starobinsky-like
inflation, and hence is compatible with constraints from the Planck satellite,
(iii) the inflaton may be identified with a singlet field in a see-saw model
for neutrino masses, providing an efficient scenario for reheating and
leptogenesis, (iv) supersymmetry breaking occurs with an arbitrary scale and a
cosmological constant that vanishes before radiative corrections, (v) regions
of the model parameter space are compatible with all LHC, Higgs and dark matter
constraints.Comment: 6 pages, 2 figures, some minor corrections and additions. Final
versio
Starobinsky-like Inflationary Models as Avatars of No-Scale Supergravity
Models of cosmological inflation resembling the Starobinsky R + R^2 model
emerge naturally among the effective potentials derived from no-scale
SU(N,1)/SU(N) x U(1) supergravity when N > 1. We display several examples in
the SU(2,1)/SU(2) x U(1) case, in which the inflaton may be identified with
either a modulus field or a matter field. We discuss how the modulus field may
be stabilized in models in which a matter field plays the role of the inflaton.
We also discuss models that generalize the Starobinsky model but display
different relations between the tilt in the spectrum of scalar density
perturbations, n_s, the tensor-to-scalar ratio, r, and the number of e-folds,
N_*. Finally, we discuss how such models can be probed by present and future
CMB experiments.Comment: 23 pages, 3 figure
From Gravity to No-Scale Supergravity
We show that gravity coupled conformally to scalar fields is equivalent
to the real bosonic sector of SU(N,1)/SU(N)U(1) no-scale supergravity,
where the conformal factor can be identified with the K\"ahler potential, and
we review the construction of Starobinsky-like models of inflation within this
framework.Comment: 15 pages, version accepted for publicatio
What if the Higgs Boson Weighs 115 GeV?
If the Higgs boson indeed weighs about 114 to 115 GeV, there must be new
physics beyond the Standard Model at some scale \la 10^6 GeV. The most
plausible new physics is supersymmetry, which predicts a Higgs boson weighing
\la 130 GeV. In the CMSSM with R and CP conservation, the existence, production
and detection of a 114 or 115 GeV Higgs boson is possible if \tan\beta \ga 3.
However, for the radiatively-corrected Higgs mass to be this large, sparticles
should be relatively heavy: m_{1/2} \ga 250 GeV, probably not detectable at the
Tevatron collider and perhaps not at a low-energy e^+ e^- linear collider. In
much of the remaining CMSSM parameter space, neutralino-stau coannihilation is
important for calculating the relic neutralino density, and we explore
implications for the elastic neutralino-nucleon scattering cross section.Comment: 17 pages, 5 eps figure
De Sitter Vacua in No-Scale Supergravity
No-scale supergravity is the appropriate general framework for low-energy
effective field theories derived from string theory. The simplest no-scale
K\"ahler potential with a single chiral field corresponds to a compactification
to flat Minkowski space with a single volume modulus, but generalizations to
single-field no-scale models with de Sitter vacua are also known. In this paper
we generalize these de Sitter constructions to two- and multi-field models of
the types occurring in string compactifications with more than one relevant
modulus. We discuss the conditions for stability of the de Sitter solutions and
holomorphy of the superpotential, and give examples whose superpotential
contains only integer powers of the chiral fields.Comment: 22 pages, 7 figure
Orthogonal Decomposition of Some Affine Lie Algebras in Terms of their Heisenberg Subalgebras
In the present note we suggest an affinization of a theorem by Kostrikin
et.al. about the decomposition of some complex simple Lie algebras
into the algebraic sum of pairwise orthogonal Cartan subalgebras. We point out
that the untwisted affine Kac-Moody algebras of types ( prime,
), can be decomposed into
the algebraic sum of pairwise or\-tho\-go\-nal Heisenberg subalgebras. The
and cases are discussed in great detail. Some possible
applications of such decompositions are also discussed.Comment: 16 pages, LaTeX, no figure
No-Scale Inflation
Supersymmetry is the most natural framework for physics above the TeV scale,
and the corresponding framework for early-Universe cosmology, including
inflation, is supergravity. No-scale supergravity emerges from generic string
compactifications and yields a non-negative potential, and is therefore a
plausible framework for constructing models of inflation. No-scale inflation
yields naturally predictions similar to those of the Starobinsky model based on
gravity, with a tilted spectrum of scalar perturbations: , and small values of the tensor-to-scalar perturbation ratio ,
as favoured by Planck and other data on the cosmic microwave background (CMB).
Detailed measurements of the CMB may provide insights into the embedding of
inflation within string theory as well as its links to collider physics.Comment: Invited contribution to the forthcoming Classical and Quantum Gravity
focus issue on "Planck and the fundamentals of cosmology". 22 pages, 7
figures, uses psfra
Phenomenological Aspects of No-Scale Inflation Models
We discuss phenomenological aspects of no-scale supergravity inflationary
models motivated by compactified string models, in which the inflaton may be
identified either as a K\"ahler modulus or an untwisted matter field, focusing
on models that make predictions for the scalar spectral index and the
tensor-to-scalar ratio that are similar to the Starobinsky model. We
discuss possible patterns of soft supersymmetry breaking, exhibiting examples
of the pure no-scale type , of the CMSSM type with
universal and at a high scale, and of the mSUGRA type with
boundary conditions at the high input scale. These may be
combined with a non-trivial gauge kinetic function that generates gaugino
masses , or one may have a pure gravity mediation scenario where
trilinear terms and gaugino masses are generated through anomalies. We also
discuss inflaton decays and reheating, showing possible decay channels for the
inflaton when it is either an untwisted matter field or a K\"ahler modulus.
Reheating is very efficient if a matter field inflaton is directly coupled to
MSSM fields, and both candidates lead to sufficient reheating in the presence
of a non-trivial gauge kinetic function.Comment: 41 pages, 6 figure
A No-Scale Inflationary Model to Fit Them All
The magnitude of B-mode polarization in the cosmic microwave background as
measured by BICEP2 favours models of chaotic inflation with a quadratic potential, whereas data from the Planck satellite favour a small
value of the tensor-to-scalar perturbation ratio that is highly consistent
with the Starobinsky model. Reality may lie somewhere between these
two scenarios. In this paper we propose a minimal two-field no-scale
supergravity model that interpolates between quadratic and Starobinsky-like
inflation as limiting cases, while retaining the successful prediction .Comment: 25 pages, 12 figure
Calculations of Inflaton Decays and Reheating: with Applications to No-Scale Inflation Models
We discuss inflaton decays and reheating in no-scale Starobinsky-like models
of inflation, calculating the effective equation-of-state parameter, ,
during the epoch of inflaton decay, the reheating temperature, ,
and the number of inflationary e-folds, , comparing analytical
approximations with numerical calculations. We then illustrate these results
with applications to models based on no-scale supergravity and motivated by
generic string compactifications, including scenarios where the inflaton is
identified as an untwisted-sector matter field with direct Yukawa couplings to
MSSM fields, and where the inflaton decays via gravitational-strength
interactions. Finally, we use our results to discuss the constraints on these
models imposed by present measurements of the scalar spectral index and
the tensor-to-scalar perturbation ratio , converting them into constraints
on , the inflaton decay rate and other parameters of specific no-scale
inflationary models.Comment: 33 pages, 14 figure
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