114 research outputs found
Finding the chiral gravitational wave background of an axion-SU(2) inflationary model using CMB observations and laser interferometers
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 the GWB. However, similar tensor perturbations can be
produced by the matter fields present during inflation, breaking this simple
relationship. It is therefore important to be able to distinguish between
different generation mechanisms of the GWB. In this paper, we analyse the
detectability of a new axion-SU(2) gauge field model using its chiral,
scale-dependent tensor spectrum. We forecast the detectability of the resulting
CMB TB and EB cross-correlations 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 with denoting the
tensor-to-scalar ratio at the peak scale, and that the maximum signal-to-noise
for is . We go on to consider an advanced stage of a
LISA-like mission, and find that such experiments would complement CMB
observations by providing sensitivity to GWB chirality on scales inaccessible
to the CMB. We conclude that in order to use the CMB to distinguish this model
from a conventional vacuum fluctuation model two-point statistics provide some
power, 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
to the CMB, a highly significant detection could be made using space-based
laser interferometers.Comment: 24 pages, 12 figures, accepted by PhysRev
On the Change of Reversible Susceptibility of Ferromagnetic Substances Due to Tension
According to the internal stress theory on ferromagnetic substances given by Kersten and Doring, the authors have calculated the reversible susceptibility as a function of magnetization under various applied tensions. Theoretical reversible susceptibility thus obtained is constant at early stage of magnetization and decreases rapidly just before the magnetic saturation. But, if the magnitude of internal stress is larger than that applied, it has a maximum before sudden decrease, which occurs near magnetic saturation. These theoretical results explain experimental data qualitatively, but some quantitative differences are found between these
Simple foreground cleaning algorithm for detecting primordial B-mode polarization of the cosmic microwave background
We reconsider the pixel-based, "template" polarized foreground removal method
within the context of a next-generation, low-noise, low-resolution (0.5 degree
FWHM) space-borne experiment measuring the cosmological B-mode polarization
signal in the cosmic microwave background (CMB). This method was put forward by
the Wilkinson Microwave Anisotropy Probe (WMAP) team and further studied by
Efstathiou et al. We need at least 3 frequency channels: one is used for
extracting the CMB signal, whereas the other two are used to estimate the
spatial distribution of the polarized dust and synchrotron emission. No
external template maps are used. We extract the tensor-to-scalar ratio (r) from
simulated sky maps consisting of CMB, noise (2 micro K arcmin), and a
foreground model, and find that, even for the simplest 3-frequency
configuration with 60, 100, and 240 GHz, the residual bias in r is as small as
Delta r~0.002. This bias is dominated by the residual synchrotron emission due
to spatial variations of the synchrotron spectral index. With an extended mask
with fsky=0.5, the bias is reduced further down to <0.001.Comment: 12 pages, 11 figures, accepted by Ap
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