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Non-Gaussianity after Planck

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If you have a question about this talk, please contact Camille Bonvin.

Testing the Gaussianity of the primordial perturbations provides a window on the early universe. Despite not detecting any new non-zero parameters, the Planck results have provided the most accurate measurements ever about the physics of the early universe.

I will reflect on these precision results and their implications for inflation, as well as the prospects for future measurements. In particular, I will focus on the implications of the results on non-Gaussianity, and what they might imply for the many other signatures that have not yet been searched for.

Finally I will discuss how one may probe the small scale perturbations. Even in the “precision era” of cosmology, measurements of the cosmic microwave background and large scale structure only cover around three orders of magnitude in length scales. Another 30 orders of magnitude in length scales must also have exited the horizon during inflation, but these smaller scales remain unobserved. Primordial Black Holes (PBHs) can form in the early universe from the collapse of large density fluctuations. Tight observational limits on their abundance provide the best upper limit on the size of the primordial fluctuations on small scales, with PBHs only forming from extremely large and rare density fluctuations. The number of PBHs formed is therefore highly sensitive to small changes in the tail of the fluctuations probability density function, which probes non-Gaussianity.

This talk is part of the Cosmology Lunch series.

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