Determining Gauge Field Induced Primordial Non-Gaussianity by Calculation of the Bispectrum employing Green’s Functions

Belleri, Giacomo (2024) Determining Gauge Field Induced Primordial Non-Gaussianity by Calculation of the Bispectrum employing Green’s Functions. Bachelor's Thesis, Physics.

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Abstract

Cosmological late-time observables are characterized by small deviations from homogeneity and isotropy. These originate in quantum fluctuations produced during inflation, a period of rapid expansion during the earliest moments of the universe. The nature of this process depends on its field content. More than one field may have been present and their interactions often result in sourced quantum fluctuations. These generally introduce non-Gaussian features in the distribution of the anisotropies. Therefore, non-Gaussianity is often used as a probe of inflation. This paper analyzes the effects and evolution of sourced quantum fluctuations originating from interactions of the inflaton with Gauge fields. After a discussion of the mechanism involved, the power spectrum and bispectrum related to these interactions are computed using Green’s functions. For most configurations of parameters, the bispectrum exhibits an equilateral shape with large non-Gaussianities. The application of PLANCK constraints (−73 ≤ f equilNL ≤ 21) imposes ξ ≤ 2.5 and H(α/ f ) ≤ 1.44 · 10−3. These correspond to configurations in which Gauge interaction effects are small. In fact, for these values, the primordial amplitude deviates from its inflaton-only counterpart by a maximum of 1.98%. In addition, a comparison with the self-interaction bispectrum ( fNL ≪ 1) suggests that self-interactions are minor corrections to the larger contribution produced by interactions with Gauge fields

Item Type:	Thesis (Bachelor's Thesis)
Supervisor name:	Dimastrogiovanni, E. and Mazumdar, A.
Degree programme:	Physics
Thesis type:	Bachelor's Thesis
Language:	English
Date Deposited:	10 Jul 2024 11:34
Last Modified:	10 Jul 2024 11:34
URI:	https://fse.studenttheses.ub.rug.nl/id/eprint/33195

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