| Abstract: |
The most appealing explanation for the origin of all structure in the Universe is that it came simply from quantum fluctuations stretched to macroscopic size during a period of exponential expansion at very early times, known as "inflation". Such an explanation is consistent with everything we have learned from cosmic microwave background (CMB) experiments, as well as other cosmological probes, such as galaxy clustering. A "proof" of inflation has been elusive, but could come from its prediction of primordial gravitational waves, which could be detected in a particular pattern in the polarization of the CMB, referred to as "B modes". Currently popular variants of inflation lead to a gravitational-wave fraction of r~0.01, and hence an experiment targeting an uncertainty of around 0.001 has the potential to tell us whether the inflationary paradigm is correct and hence to probe fundamental physics at nearly the Planck scale. LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a Japanese-led space mission planned to orbit the Sun-Earth Lagrangian point L2, where it will map the cosmic microwave background polarization over the entire sky for three years, in 15 frequency bands between 34 and 448 GHz, to achieve an unprecedented total sensitivity and ability to separate the CMB from Galactic foregrounds. The primary scientific objective of LiteBIRD is to search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with insight into other kinds of new physics beyond the standard models of particle physics and cosmology. |
