Probing hidden sectors with early universe cosmology

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Ralegankar, Pranjal

Contributors dc:contributor

• Shelton, Jessie
• Adshead, Peter
• Holder, Gilbert
• Kahn, Yonatan

• Cosmology
• Dark Matter
• Dark Radiation
• Early Universe

Statement dc:rights

• Copyright 2022 Pranjal Ralegankar

Language dc:language

en, eng

Handle dc:identifier

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

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F117720