55 research outputs found
Duality Invariance of Cosmological Perturbation Spectra
I show that cosmological perturbation spectra produced from quantum
fluctuations in massless or self-interacting scalar fields during an
inflationary era remain invariant under a two parameter family of
transformations of the homogeneous background fields. This relates slow-roll
inflation models to solutions which may be far from the usual slow-roll limit.
For example, a scale-invariant spectrum of perturbations in a minimally
coupled, massless field can be produced by an exponential expansion with
, or by a collapsing universe with .Comment: 5 pages, Latex with Revtex. Hamiltonian formulation added and
discussion expanded. Version to appear in Phys Rev
Observational constraints on an inflation model with a running mass
We explore a model of inflation where the inflaton mass-squared is generated
at a high scale by gravity-mediated soft supersymmetry breaking, and runs at
lower scales to the small value required for slow-roll inflation. The running
is supposed to come from the coupling of the inflaton to a non-Abelian gauge
field. In contrast with earlier work, we do not constrain the magnitude of the
supersymmetry breaking scale, and we find that the model might work even if
squark and slepton masses come from gauge-mediated supersymmetry breaking. With
the inflaton and gaugino masses in the expected range, and
in the range to (all at the high scale) the model can give
the observed cosmic microwave anisotropy, and a spectral index in the observed
range. The latter has significant variation with scale, which can confirm or
rule out the model in the forseeable future.Comment: Latex, 19 pages, 14 figures, uses epsf.st
Natural Inflation From Fermion Loops
``Natural'' inflationary theories are a class of models in which inflation is
driven by a pseudo-Nambu-Goldstone boson. In this paper we consider two models,
one old and one new, in which the potential for inflation is generated by loop
effects from a fermion sector which explicitly breaks a global symmetry.
In both models, we retrieve the ``standard'' natural inflation potential,
, as a limiting case of the exact one-loop potential, but we
carry out a general analysis of the models including the limiting case.
Constraints from the COBE DMR observation and from theoretical consistency are
used to limit the parameters of the models, and successful inflation occurs
without the necessity of fine-tuning the parameters.Comment: (Revised) 15 pages, LaTeX (revTeX), 8 figures in uuencoded PostScript
format. Version accepted for publication in Phys. Rev. D 15. Corrected
definition of power spectrum and added three reference
Hybridized Affleck-Dine baryogenesis
We propose a novel scenario for Affleck-Dine baryogenesis in the braneworld,
considering the hybrid potential for the Affleck-Dine field. Destabilization of
the flat direction is not due to the Hubble parameter, but is induced by a
trigger field. The moduli for the brane distance plays the role of the trigger
field. Q-balls are unstable in models with large extra dimensions.Comment: 10pages, plain latex2e, references added, to appear in PR
D-terms and D-strings in open string models
We study the Fayet-Iliopoulos (FI) D-terms on D-branes in type II Calabi-Yau
backgrounds. We provide a simple worldsheet proof of the fact that, at tree
level, these terms only couple to scalars in closed string hypermultiplets. At
the one-loop level, the D-terms get corrections only if the gauge group has an
anomalous spectrum, with the anomaly cancelled by a Green-Schwarz mechanism. We
study the local type IIA model of D6-branes at SU(3) angles and show that, as
in field theory, the one-loop correction suffers from a quadratic divergence in
the open string channel. By studying the closed string channel, we show that
this divergence is related to a closed string tadpole, and is cancelled when
the tadpole is cancelled. Next, we study the cosmic strings that arise in the
supersymmetric phases of these systems in light of recent work of Dvali et. al.
In the type IIA intersecting D6-brane examples, we identify the D-term strings
as D4-branes ending on the D6-branes. Finally, we use N=1 dualities to relate
these results to previous work on the FI D-term of heterotic strings.Comment: 29 pages, 5 figures; v2: improved referencin
Monte Carlo reconstruction of the inflationary potential
We present Monte Carlo reconstruction, a new method for ``inverting''
observational data to constrain the form of the scalar field potential
responsible for inflation. This stochastic technique is based on the flow
equation formalism and has distinct advantages over reconstruction methods
based on a Taylor expansion of the potential. The primary ansatz required for
Monte Carlo reconstruction is simply that inflation is driven by a single
scalar field. We also require a very mild slow roll constraint, which can be
made arbitrarily weak since Monte Carlo reconstruction is implemented at
arbitrary order in the slow roll expansion. While our method cannot evade
fundamental limits on the accuracy of reconstruction, it can be simply and
consistently applied to poor data sets, and it takes advantage of the attractor
properties of single-field inflation models to constrain the potential outside
the small region directly probed by observations. We show examples of Monte
Carlo reconstruction for data sets similar to that expected from the Planck
satellite, and for a hypothetical measurement with a factor of five better
parameter discrimination than Planck.Comment: 10 pages, 5 figures (RevTeX 4) Version submitted to PRD: references
added, minor clarification
Inflation from Susy quantum cosmology
We propose a realization of inverted hybrid inflation scenario in the context
of n=2 supersymmetric quantum cosmology. The spectrum of density fluctuations
is calculated in the de Sitter regimen as a function of the gravitino and the
Planck mass, and explicit forms for the wave function of the universe are found
in the WKB regimen for a FRW closed and flat universes.Comment: 9 pages, one figure, to appear in Phys. Rev.
Particle physics models of inflation
Inflation models are compared with observation on the assumption that the
curvature perturbation is generated from the vacuum fluctuation of the inflaton
field. The focus is on single-field models with canonical kinetic terms,
classified as small- medium- and large-field according to the variation of the
inflaton field while cosmological scales leave the horizon. Small-field models
are constructed according to the usual paradigm for beyond Standard Model
physicsComment: Based on a talk given at the 22nd IAP Colloquium, ``Inflation +25'',
Paris, June 2006 Curve omitted from final Figur
The Detectability of Departures from the Inflationary Consistency Equation
We study the detectability, given CMB polarization maps, of departures from
the inflationary consistency equation, r \equiv T/S \simeq -5 n_T, where T and
S are the tensor and scalar contributions to the quadrupole variance,
respectively. The consistency equation holds if inflation is driven by a
slowly-rolling scalar field. Departures can be caused by: 1) higher-order terms
in the expansion in slow-roll parameters, 2) quantum loop corrections or 3)
multiple fields. Higher-order corrections in the first two slow-roll parameters
are undetectably small. Loop corrections are detectable if they are nearly
maximal and r \ga 0.1. Large departures (|\Delta n_T| \ga 0.1) can be seen if r
\ga 0.001. High angular resolution can be important for detecting non-zero
r+5n_T, even when not important for detecting non-zero r.Comment: 7 pages, 4 figures, submitted to PR
Inflation at Low Scales: General Analysis and a Detailed Model
Models of inflationary cosmology based on spontaneous symmetry breaking
typically suffer from the shortcoming that the symmetry breaking scale is
driven to nearly the Planck scale by observational constraints. In this paper
we investigate inflationary potentials in a general context, and show that this
difficulty is characteristic only of potentials dominated near their
maxima by terms of order . We find that potentials dominated by terms
of order with \hbox{} can satisfy observational constraints at
an arbitrary symmetry breaking scale. Of particular interest, the spectral
index of density fluctuations is shown to depend only on the order of the
lowest non-vanishing derivative of near the maximum. This result is
illustrated in the context of a specific model, with a broken
symmetry, in which the potential is generated by gauge boson loops.Comment: Submitted to Phys. Rev. D. 32 Pages, REVTeX. No figure
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