The quest for B modes from inflationary gravitational waves

Marc Kamionkowski, Ely D. Kovetz

Research output: Contribution to journalArticlepeer-review

256 Scopus citations


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.

Original languageEnglish
Pages (from-to)227-269
Number of pages43
JournalAnnual Review of Astronomy and Astrophysics
StatePublished - 19 Sep 2016
Externally publishedYes


  • Cosmic microwave background
  • Cosmology
  • Early Universe

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'The quest for B modes from inflationary gravitational waves'. Together they form a unique fingerprint.

Cite this