The Quest for B Modes from Inflationary Gravitational Waves
  The search for the curl component (B mode) in the cosmic microwave background
(CMB) polarization induced by inflationary gravitational waves is described.
The canonical single-field slow-roll model of inflation is presented, and we
explain the quantum production of primordial density perturbations and
gravitational waves. It is shown how these gravitational waves then give rise
to polarization in the CMB. We then describe the geometric decomposition of the
CMB polarization pattern into a curl-free component (E mode) and curl component
(B mode) and show explicitly that gravitational waves induce B modes. We
discuss the B modes induced by gravitational lensing and by Galactic
foregrounds and show how both are distinguished from those induced by
inflationary gravitational waves. Issues involved in the experimental pursuit
of these B modes are described, and we summarize some of the strategies being
pursued. We close with a brief discussion of some other avenues toward
detecting/characterizing the inflationary gravitational-wave background.
