Probing hidden sectors with early universe cosmology

Ralegankar, Pranjal

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https://hdl.handle.net/2142/117720 Copy

Description

Title

Probing hidden sectors with early universe cosmology

Author(s)

Ralegankar, Pranjal

Issue Date

2022-09-16

Director of Research (if dissertation) or Advisor (if thesis)

• Shelton, Jessie
• Adshead, Peter

Doctoral Committee Chair(s)

Holder, Gilbert

Committee Member(s)

Kahn, Yonatan

Department of Study

Physics

Discipline

Physics

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Cosmology
• Dark matter
• Dark radiation
• Early Universe

Abstract

There is no fundamental requirement for all particles to be charged under the Standard Model gauge symmetries. Consequently, there could naturally be a hidden sector of particles that have gone undetected and dark matter could reside in it. A hidden sector of particles could naturally have a different temperature than the plasma formed by the Standard Model particles in the early universe. Such a hidden sector can alter early universe cosmology from the assumed behavior in a variety of ways, which we explore in this thesis. First, we discuss how both hidden sector and Standard Model sector can be populated via inflaton decays after inflation. Next, we explore how thermally decoupled hidden sector with a massive lightest particle (m ≫ MeV) can enhance the abundance of sub-Earth mass dark matter microhalos today. We then explore how hidden sectors with a massless lightest particle can cause an inhomogeneous distribution of helium to hydrogen ratios if the hidden sector never had any interaction with the Standard Model sector. If instead the hidden sector had some interaction, then we show how the constraints on dark radiation energy density can be employed to constrain the interaction strength between the two sectors.

Graduation Semester

2022-12

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Pranjal Ralegankar

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