324 research outputs found
Toward Higgs inflation in the MSSM
Adopting a recently proposed single-superfield framework of supergravity
inflation, we consider large field inflationary models in which MSSM Higgs-like
fields play the role of the inflaton. In the simplest cases, the inflaton
potential has a fractional power, which is different from that of the original
Higgs inflation, and it can be tested by cosmological observations in near
future. We find difficulties in identifying the inflaton with the MSSM Higgses
and discuss possible candidates of the inflaton.Comment: 4 pages, 1 figure; a contribution to the proceedings of The 2nd
Toyama International Workshop on "Higgs as a Probe of New Physics 2015"
(HPNP2015), based on a poster presentation given ther
Generalized Pole Inflation: Hilltop, Natural, and Chaotic Inflationary Attractors
A reformulation of inflationary model analyses appeared recently, in which
inflationary observables are determined by the structure of a pole in the
inflaton kinetic term rather than the shape of the inflaton potential. We
comprehensively study this framework with an arbitrary order of the pole taking
into account possible additional poles in the kinetic term or in the potential.
Depending on the setup, the canonical potential becomes the form of hilltop or
plateau models, variants of natural inflation, power-law inflation, or
monomial/polynomial chaotic inflation. We demonstrate attractor behaviors of
these models and compute corrections from the additional poles to the
inflationary observables.Comment: 22 pages, 5 figures; v3 published version (minor revision) +
additional materials (Figures 1, 4 and Table 1). A one-minute introductory
movie is available at https://youtu.be/pLod18Z0EV
Inflation in Supergravity with a Single Chiral Superfield
We propose new supergravity models describing chaotic Linde- and
Starobinsky-like inflation in terms of a single chiral superfield. The key
ideas to obtain a positive vacuum energy during large field inflation are (i)
stabilization of the real or imaginary partner of the inflaton by modifying a
Kahler potential, and (ii) use of the crossing terms in the scalar potential
originating from a polynomial superpotential. Our inflationary models are
constructed by starting from the minimal Kahler potential with a shift
symmetry, and are extended to the no-scale case. Our methods can be applied to
more general inflationary models in supergravity with only one chiral
superfield.Comment: 12 pages, 2 figures, published version; See http://neko2.net/ssi/ for
a short movie of this wor
Single-Superfield Helical-Phase Inflation
Large-field inflation in supergravity requires the approximate global
symmetry needed to protect flatness of the scalar potential. In helical-phase
inflation, the U(1) symmetry of the Kahler potential is assumed, the phase part
of the complex scalar of a chiral superfield plays the role of inflaton, and
the radial part is strongly stabilized. The original model of helical phase
inflation, proposed by Li, Li and Nanopoulos (LLN), employs an extra
(stabilizer) superfield. We propose a more economical new class of the helical
phase inflationary models without a stabilizer superfield. As the specific
examples, the quadratic, the natural, and the Starobinsky-type inflationary
models are studied in our approach.Comment: 11 pages, 3 figures (published version); more explanations and
references added, typos corrected, and figures improve
Unitarity constraint on the K\"ahler curvature
In supersymmetric theories, the signs of quartic terms in the K\"ahler
potential control the stability of non-supersymmetric field configurations. In
particular, in supersymmetric inflation models, the signs are important for the
stability of an inflationary trajectory as well as for the prediction of the
spectral index. In this paper, we clarify what properties of a UV theory
determine the sign from unitarity arguments of scattering amplitudes. As
non-trivial examples, we discuss the sign of a four-meson term in large
supersymmetric gauge theories and also those of the quartic terms obtained in
the intersecting D-brane models in superstring theory. The UV origins of
inflationary models and supersymmetry breaking models are constrained by this
discussion.Comment: 20 pages, 2 figures; published version, minor changes, references
adde
Complexified Starobinsky Inflation in Supergravity in the Light of Recent BICEP2 Result
Motivated by the recent observation of the B-mode signal in the cosmic
microwave background by BICEP2, we stuty the Starobinsky-type inflation model
in the framework of old-minimal supergravity, where the inflaton field in the
original (non-supersymmetric) Starobinsky inflation model becomes a complex
field. We study how the inflaton evolves on the two-dimensional field space,
varying the initial condition. We show that (i) one of the scalar fields has a
very steep potential once the trajectory is off from that of the original
Starobinsky inflation, and that (ii) the B-mode signal observed by BICEP2 is
too large to be consistent with the prediction of the model irrespective of the
initial condition. Thus, the BICEP2 result strongly disfavors the complexified
Starobinsky inflation in supergravity.Comment: 8 pages, 2 figures, the published versio
Enhancement of Gravitational Waves Induced by Scalar Perturbations due to a Sudden Transition from an Early Matter Era to the Radiation Era
We study gravitational waves induced from the primordial scalar perturbations
at second order around the reheating of the Universe. We consider reheating
scenarios in which a transition from an early matter dominated era to the
radiation dominated era completes within a timescale much shorter than the
Hubble time at that time. We find that an enhanced production of induced
gravitational waves occurs just after the reheating transition because of fast
oscillations of scalar modes well inside the Hubble horizon. This enhancement
mechanism just after an early matter-dominated era is much more efficient than
a previously known enhancement mechanism during an early matter era, and we
show that the induced gravitational waves could be detectable by future
observations if the reheating temperature is in the range
GeV or . This is the case even if the
scalar perturbations on small scales are not enhanced relative to those on
large scales, probed by the observations of the cosmic microwave background.Comment: 13 pages, 5 figures, v2: minor changes, version accepted for
publication in PR
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