Cosmology Large Angular Scale Surveyor: Difference between revisions

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[[File:CLASS site annotated 2018-06.svg|thumbnail|200px|left|Overview of the CLASS site in 2018.]]

A primary science goal of CLASS is to test the theory of inflation. In [[physical cosmology]], [[cosmic inflation]] is the leading theory of the very early universe;<ref name=2014-Linde-Inflation-Overview/> however, observational evidence for inflation is still inconclusive. Inflationary models generically predict that a [[gravitational wave|gravitational-wave background]] (GWB) would have been produced along with the density perturbations that seed [[structure formation|large-scale structure]]. Such an inflationary GWB would leave an imprint on both the temperature and polarization of the CMB. In particular it would leave a very distinctive and unique pattern of polarization, called a [[B-modes|B-mode]] pattern, in the CMB polarization. A measurement of B-mode polarization in the CMB would be important confirmation of inflation and would provide a rare glimpse into physics at ultra-high energies.<ref name=Boyle-Inflation/><ref name=Tegmark-Inflation/>

CLASS will also improve our understanding of "cosmic dawn," when the first stars lit up the universe. Ultraviolet (UV) radiation from these stars stripped electrons from atoms in a process called "[[reionization]]." The freed electrons scatter CMB light, imparting a polarization that CLASS measures. In this way CLASS can improve our knowledge of when and how cosmic dawn occurred. A better understanding of cosmic dawn will also help other experiments measure the sum of the masses of the three known [[neutrino]] types using the [[gravitational lensing]] of the CMB.