Chiral primordial blue tensor spectra from the axiongauge couplings
Abstract
We suggest the new feature of primordial gravitational waves sourced by the axiongauge couplings, whose forms are motivated by the dimensional reduction of the form field in the string theory. In our inflationary model, as an inflaton we adopt two types of axion, dubbed the modelindependent axion and the modeldependent axion, which couple with two gauge groups with different sign combination each other. Due to these forms both polarization modes of gauge fields are amplified and enhance both helicies of tensor modes during inflation. We point out the possibility that a primordial bluetilted tensor power spectra with small chirality are provided by the combination of these axiongauge couplings, intriguingly both amplitudes and chirality are potentially testable by future spacebased gravitational wave interferometers such as DECIGO and BBO project.
 Authors:
 Department of Physics, Kyoto University, Kyoto, 6068502 (Japan)
 Publication Date:
 OSTI Identifier:
 22676137
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2017; Journal Issue: 06; Other Information: Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; AMPLITUDES; AXIONS; CHIRALITY; COUPLING; GRAVITATIONAL WAVES; INFLATIONARY UNIVERSE; INFLATONS; INTERFEROMETERS; POLARIZATION; SPACE; SPECTRA; STRING THEORY
Citation Formats
Obata, Ippei, Email: obata@tap.scphys.kyotou.ac.jp. Chiral primordial blue tensor spectra from the axiongauge couplings. United States: N. p., 2017.
Web. doi:10.1088/14757516/2017/06/050.
Obata, Ippei, Email: obata@tap.scphys.kyotou.ac.jp. Chiral primordial blue tensor spectra from the axiongauge couplings. United States. doi:10.1088/14757516/2017/06/050.
Obata, Ippei, Email: obata@tap.scphys.kyotou.ac.jp. Thu .
"Chiral primordial blue tensor spectra from the axiongauge couplings". United States.
doi:10.1088/14757516/2017/06/050.
@article{osti_22676137,
title = {Chiral primordial blue tensor spectra from the axiongauge couplings},
author = {Obata, Ippei, Email: obata@tap.scphys.kyotou.ac.jp},
abstractNote = {We suggest the new feature of primordial gravitational waves sourced by the axiongauge couplings, whose forms are motivated by the dimensional reduction of the form field in the string theory. In our inflationary model, as an inflaton we adopt two types of axion, dubbed the modelindependent axion and the modeldependent axion, which couple with two gauge groups with different sign combination each other. Due to these forms both polarization modes of gauge fields are amplified and enhance both helicies of tensor modes during inflation. We point out the possibility that a primordial bluetilted tensor power spectra with small chirality are provided by the combination of these axiongauge couplings, intriguingly both amplitudes and chirality are potentially testable by future spacebased gravitational wave interferometers such as DECIGO and BBO project.},
doi = {10.1088/14757516/2017/06/050},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 06,
volume = 2017,
place = {United States},
year = {Thu Jun 01 00:00:00 EDT 2017},
month = {Thu Jun 01 00:00:00 EDT 2017}
}

Inspired by the chromonatural inflation model of Adshead and Wyman, we reshape its scalar content to relax the tension with current observational bounds. Besides an inflaton, the setup includes a spectator sector in which an axion and SU(2) gauge fields are coupled via a ChernSimonstype term. The result is a viable theory endowed with an alternative production mechanism for gravitational waves during inflation. The gravitational wave signal sourced by the spectator fields can be much larger than the contribution from standard vacuum fluctuations, it is distinguishable from the latter on the basis of its chirality and, depending on the theorymore »

Blue running of the primordial tensor spectrum
We examine the possibility of positive spectral index of the power spectrum of the primordial tensor perturbation produced during inflation in the light of the detection of the Bmode polarization by the BICEP2 collaboration. We find a blue tilt is in general possible when the slowroll parameter decays rapidly. We present two known examples in which a positive spectral index for the tensor power spectrum can be obtained. We also briefly discuss other consistency tests for further studies on inflationary dynamics. 
Currents and energymomentum tensor in the chiral Schwinger model with general vector and axialvector couplings
Using the pointsplitting procedure and the method of functional integration, we define currents in the chiral Schwinger model and compute the correlation funtions of currents with themselves and with the fundamental fields. We show that the ambiguities in the choice of the phase factor employed in the pointsplitting procedure can be compensated by mixing of the currents with the gauge potential {ital A}{sub {mu}} and {epsilon}{sub {mu}{nu}}{ital A}{sup {nu}}. A threeparameter family of conserved currents is found and the transformations they generate are identified. In order to construct the conserved energymomentum tensor, it is necessary to allow for mixings withmore »