  LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and
Inflation from cosmic background Radiation Detection, is a space mission for
primordial cosmology and fundamental physics. JAXA selected LiteBIRD in May
2019 as a strategic large-class (L-class) mission, with its expected launch in
the late 2020s using JAXA's H3 rocket. LiteBIRD plans to map the cosmic
microwave background (CMB) polarization over the full sky with unprecedented
precision. Its main scientific objective is to carry out a definitive 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 an insight into the quantum nature of gravity and other new
physics beyond the standard models of particle physics and cosmology. To this
end, LiteBIRD will perform full-sky surveys for three years at the Sun-Earth
Lagrangian point L2 for 15 frequency bands between 34 and 448 GHz with three
telescopes, to achieve a total sensitivity of 2.16 micro K-arcmin with a
typical angular resolution of 0.5 deg. at 100GHz. We provide an overview of the
LiteBIRD project, including scientific objectives, mission requirements,
top-level system requirements, operation concept, and expected scientific
outcomes.
