Inflationary origin

Print edition : May 02, 2014

Figure 1: The dark sector lab, located about a kilometre from the South Pole, houses the BICEP2 telescope (left) and the South Pole Telescope (right). Photo: STEFFEN RICHTER, HARVARD UNIVERSITY

Figure 2: History of the universe with inflation: The bottom part of this illustration shows the scale of the universe versus time. The density waves appear as temperature and "E-mode" polarisation. The gravitational waves leave a characteristic signature in the CMB polarisation: the "B-modes". Both density and gravitational waves come from quantum fluctuations, which have been magnified by inflation to be present at the time when the CMB photons were emitted.

Figure 4: polarisation can be decomposed into E- and B-modes. The former are radial or tangential with no preferred handedness. B-modes do have handedness. This peculiar pattern can be produced only by gravitational waves, not by density fluctuations.

Figure 5: Gravitational waves from inflation generate a distinctive twisting pattern in the polarisation of the CMB, known as a "curl" or B-mode pattern. For the density fluctuations that generate most of the polarisation of the CMB, this part of the primordial pattern is zero. The figure shows the B-mode pattern observed with the BICEPS2 telescope, with the line segments showing the polarisation from different spots in the sky. The red and blue shading shows the degree of clockwise and anti-clockwise twisting of this B-mode pattern.

The sun rises behind the CMB telescopes at the National Science Foundation's South Pole station. Photo: Steffen Richter, Harvard University

The first detection of primordial gravitational waves could provide observational evidence of how the universe evolved.

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