Christian Byrnes

Non-Gaussianity from inflation

It is well known that multi field inflation can lead to large non-Gaussianity of the so called local type, however it is less well appreciated that in “many” cases multifield inflation does not lead to any observable deviation from single-field inflation. Non-Gaussianity is usually parametrised using the amplitude fNL and until now only values of fNL>>1 would be observable. However, galaxy surveys in the next decade promise to be able to probe the interesting regime of fNL~1 (provided systematics can be kept under control), which is arguably the value which should expected in several classes of multi field inflation such as the curvaton scenario or modulated reheating. 

 The broad goal of this PhD project would be to better understand which classes of models predict fNL~1, to what extent the prediction can be mode more accurate than an order of magnitude, and how “natural” these theories are compared to those which predict fNL<<1. Both analytical and numerical skills would be important. 

 For a review about primordial non-Gaussianity see https://arxiv.org/abs/1508.06740. Relevant reading of papers by the proposed supervisor include https://inspirehep.net/literature/1643257 and https://inspirehep.net/literature/1286295 and https://inspirehep.net/literature/790119.