Modeling inflation in string theory
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Date
2019
Authors
Patel, Mitulkumar
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Abstract
The standard big bang theory (BB) is, at present, the best model one has to describe the evolution of our universe. Most of the predictions of the model have been verified to extraordinary precision. However, BB has some extreme fine-tuning problems. The inflationary theory was proposed as a way to resolve these problems. Inflation can be described as a period of very rapid expansion in the very early universe dominated mostly by some field(s) (known as inflaton field) potential energy V. For any successful inflationary model, the scalar potential has to be almost flat in some direction to drive inflation and so has to obey the slow-roll conditions. These conditions require that the slow-roll parameters be much less than unity.
In this thesis, we consider an approach to derive V for a specific toy model in the context of string theory. We study inflation in type IIB compactified on Calabi-Yau manifold since it comes with many classically flat moduli fields. Stabilization of these moduli fields is vital for any inflationary models in this context. Our starting point is to assume parts of the complex structure moduli and axio-dilation are stabilized by some classical mechanism such as flux compactification. The remaining unstabilized field(s) could then leave some almost flat directions after considering nonperturbative correction that could drive inflation. Thus, the resulting potential for these field(s) is derived. We show that the derived scalar potential in a toy model does indeed satisfy the slow-roll conditions, and so is a suitable candidate for inflation.
We also look at models of moduli stabilization in a region close to conifold singularity for different Kahler potentials. The masses and the warp factor for the complex structure moduli and axio-dilaton were calculated. We find evidence for runaway directions in the resulting scalar potential.
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Physics