Schedule by Session
Abstract
Early-Universe Cosmology and Gravitational Waves
Future detection of the chiral gravitational wave background of an SU(2)-axion inflationary model
Kavli IPMU, University of Tokyo
A detection of B-mode polarization of the Cosmic Microwave Background (CMB) anisotropies would confirm the presence of a primordial gravitational wave background (GWB).
In the inflation paradigm this would be an unprecedented probe of the energy scale of inflation as it is directly proportional to the power spectrum of GWB.
However, similar tensor perturbations can be produced by the matter fields present during inflation, breaking the simple relationship between energy scale and the tensor-to-scalar ratio. It is therefore important to find ways of distinguishing between the generation mechanisms of GWB.
In this paper we analyse the detectability of a new SU(2)-axion gauge
field model using its chiral, scale-dependent tensor spectrum.
We forecast the detectability of the resulting CMB temperature and B-mode (TB) or E-mode and B-mode (EB) cross-correlation by the LiteBIRD satellite, considering the effects of residual foregrounds, gravitational lensing, and for the first time assess the ability of such an experiment to jointly detect primordial TB and EB spectra and self-calibrate its polarimeter. We find that LiteBIRD will be able to detect
the chiral signal for a peak tensor-to-scalar ratio greater than 0.03, and that the maximum signal-to-noise for peak tensor-to-scalar ratio less than 0.07 is 2.
We go on to consider an advanced stage of a LISA-like mission, which is designed to be sensitive to the intensity and polarization of the gravitational wave background. We find that such experiments would complement CMB observations as they would be able to detect the
gravitational wave background's chirality with high significance on scales inaccessible to the CMB.
We conclude that in order to use CMB observations to distinguish this model from a conventional vacuum fluctuation of GWB the two-point statistics
provide some power, especially if able to constrain the tilt of the tensor spectrum, but to achieve high statistical significance we would
require higher order statistics which take advantage of the model's non-Gaussianity. On the other hand, in the case of a spectrum peaked
at very small scales inaccessible using the CMB, a highly significant detection could be made using space-based interferometers.
In the inflation paradigm this would be an unprecedented probe of the energy scale of inflation as it is directly proportional to the power spectrum of GWB.
However, similar tensor perturbations can be produced by the matter fields present during inflation, breaking the simple relationship between energy scale and the tensor-to-scalar ratio. It is therefore important to find ways of distinguishing between the generation mechanisms of GWB.
In this paper we analyse the detectability of a new SU(2)-axion gauge
field model using its chiral, scale-dependent tensor spectrum.
We forecast the detectability of the resulting CMB temperature and B-mode (TB) or E-mode and B-mode (EB) cross-correlation by the LiteBIRD satellite, considering the effects of residual foregrounds, gravitational lensing, and for the first time assess the ability of such an experiment to jointly detect primordial TB and EB spectra and self-calibrate its polarimeter. We find that LiteBIRD will be able to detect
the chiral signal for a peak tensor-to-scalar ratio greater than 0.03, and that the maximum signal-to-noise for peak tensor-to-scalar ratio less than 0.07 is 2.
We go on to consider an advanced stage of a LISA-like mission, which is designed to be sensitive to the intensity and polarization of the gravitational wave background. We find that such experiments would complement CMB observations as they would be able to detect the
gravitational wave background's chirality with high significance on scales inaccessible to the CMB.
We conclude that in order to use CMB observations to distinguish this model from a conventional vacuum fluctuation of GWB the two-point statistics
provide some power, especially if able to constrain the tilt of the tensor spectrum, but to achieve high statistical significance we would
require higher order statistics which take advantage of the model's non-Gaussianity. On the other hand, in the case of a spectrum peaked
at very small scales inaccessible using the CMB, a highly significant detection could be made using space-based interferometers.
Schedule
Monday
09:00 - 10:30
09:40
Wilberforce LT-28
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