6 research outputs found
Non-Gaussianities in DBI inflation with angular motion
We study DBI spinflation models with angular potentials that are derived in
string theory. We analyse the background dynamics with different parameter sets
and study the impact of changing each parameter on inflationary dynamics. It is
known that the conversion of the entropy perturbation into the curvature
perturbation gives multi-field DBI inflation models a possibility of satisfying
the observational constraints by relaxing the stringent microphysical
constraint that disfavours single field DBI inflation models. we show that our
model is excluded by the Planck satellite observations even with the conversion
mechanism regardless of the parameter set.Comment: 23 pages, 11 figures, matches published versio
Cosmological signatures of brane inflation
Cosmology motivated by string theory has been studied extensively in the
recent literature. String theory is promising because it has interesting
features such as unifying gravity, electromagnetic, weak and strong nuclear
forces. However, even the energy scale of the experiments at the Large Hadron
Collider (~TeV) is too low to detect any strong evidence for string theory. The
energy scale of inflation can be above ~10^9 TeV. Therefore, it is expected to
find some signature of string theory in cosmology.
String theory predicts ten space-time dimensions. In the brane world
scenario, our four dimensional Universe is confined onto the higher dimensional
object called the Brane in the ten dimensional space time. The
Dirac-Born-Infeld (DBI) inflation is based on this idea. DBI inflation predicts
a characteristic statistical feature in the Cosmic Microwave Background (CMB)
temperature anisotropies. In this thesis, we study the predictions of the DBI
inflation models on the CMB temperature anisotropies.Comment: arXiv admin note: text overlap with arXiv:1403.668
Non-Gaussianities in multi-field DBI inflation with a waterfall phase transition
We study multi-field DBI inflation models with a waterfall phase transition.
This transition happens for a D3 brane moving in the warped conifold if there
is an instability along angular directions. The transition converts the angular
perturbations into the curvature perturbation. Thanks to this conversion,
multi-field models can evade the stringent constraints that strongly disfavour
single field ultra-violet DBI inflation models in string theory. We explicitly
demonstrate that our model satisfies current observational constraints on the
spectral index and equilateral non-Gaussianity as well as the bound on the
tensor to scalar ratio imposed in string theory models. In addition we show
that large local type non-Gaussianity is generated together with equilateral
non-Gaussianity in this model.Comment: 18 pages, 6 figure
Space Demonstration of Two-Layer Pop-Up Origami Deployable Membrane Reflectarray Antenna by 3U CubeSat OrigamiSat-2
3U CubeSat OrigamiSat-2 demonstrates a 50-cm × 50-cm two-layer pop-up Origami deployable membrane reflectarray antenna in space. The membrane has small stowage volume and high gain even though it has low flatness because of a large enough antenna area to cover its un-flatness. C-band transmitter is equipped in the CubeSat and offers 20-Mbps amateur satellite communication. In 3U size, a 1-m length deployable gravity gradient mast and magnetic torquer are equipped to stabilize and control its attitude. A camera is attached to the satellite to measure the shape of the membrane antenna. OrigamiSat-2 was selected as the Innovative Satellite Technology Demonstration-4 by Japan Aerospace Exploration Agency (JAXA) and is going to be launched in 2024 by Epsilon Launch Vehicle