URL: https://physikseminar.desy.de/zeuthen/past_colloquia/colloquia_in_2014/april_23_2014/@@siteview
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Gravitational Waves from the Big Bang - Inflation in String Theory after BICEP2
Alexander Westphal (DESY)
Seminar room 3, 3.00 pm
BICEP2 from Antarctica has given us the first clear evidence for primordial gravitational waves causing B-mode polarization at degree angular scales ℓ<100. If interpreted in the context of inflation, their signal corresponds to a tensor-to-scalar ratio r=0.16^{+0.06}_{-0.05}, which disfavors r<0.01 at about 5σ. We will discuss the implications of this result for models of single-field slow-roll inflation. Due to the Lyth bound, the new data represent strong evidence against virtually all small-field models of inflation. We will discuss the need for protective symmetries such as shift symmetries in large-field inflation models which are now favored, and review the situation of string inflation and its large-field version of (axion) monodromy.
