Signatures of New Physics from the Primordial Universe

[摘要] During inflation quantum fluctuations of the field drivinginflation, known as inflaton, were stretched by inflationaryexpansion to galactic size scales or even larger. A possibleimplication of inflation -- if it is correct -- is that ourobservable universe was once of sub-Planckian size. Thus inflationcould act as a magnifier to probe the short distance structure ofspace-time. General arguments about the quantum theory of gravitysuggest that the short distance structure of space-time can bemodeled as arising from some corrections to the well-knownuncertainty relation between the position and momentum operators.Such modifications have been predicted by more fundamental theoriessuch as string theory. This modified commutation relation has beenimplemented at the first quantized level to the theory ofcosmological perturbations. In this thesis, we will show that theaforementioned scenario of implementing the minimal length to theaction has an ambiguity: total time derivatives that in continuousspace-time could be neglected and do not contribute to the equationsof motion, cease to remain total time derivatives as we implementminimal length. Such an ambiguity opens up the possibility fortrans-Planckian physics to leave an imprint on the ratio of tensorto scalar fluctuations. In near de-Sitter space, we obtain theexplicit dependence of the tensor/scalar on the minimal length. Alsothe first consistency relation is examined in a power-lawbackground, where it is found that despite the ambiguity that existsin choosing the action, Planck scale physics modifies theconsistency relation considerably as it leads to large oscillationsin the scalar spectral index in the observable range of scales. Inthe second part of the thesis, I demonstrate how the assumption ofexistence of invariant minimal length can assist us to explain theorigin of cosmic magnetic fields. The third part of the thesis isdedicated to the study of signatures of M-theory Cascade inflation.

[发布机构] University of Waterloo

[效力级别] Trans-Planckian

[关键词] Inflation;Trans-Planckian;M-theory;String Theory;M5-Brane;Cosmic Magnetic Fields;Physics