Understanding microscopic physics through gravity promises and challenges for properties of dense matter and mirror matter detection

Tan, Hung

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https://hdl.handle.net/2142/121518 Copy

Description

Title

Understanding microscopic physics through gravity promises and challenges for properties of dense matter and mirror matter detection

Author(s)

Tan, Hung

Issue Date

2023-07-13

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

Yunes, Nicolas

Doctoral Committee Chair(s)

Noronha-Hostler, Jacquelyn

Committee Member(s)

• Leite Noronha, Jorge
• Holder, Gilbert

Department of Study

Physics

Discipline

Physics

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• gravitational wave
• neutron star equation of state
• dark matter

Abstract

The detection of gravitational radiation opens a new era to gravitational wave astronomy. The event GW170817 is particularly exciting because it shows the potential for using gravitational wave observation to discover microscopic physics. Specifically, new degrees of freedom, such as hyperons or deconfined quarks, can emerge in a cold, dense environment, leading to phase transitions or crossovers. This environment exists at the core of a neutron star but cannot be reproduced in a terrestrial lab. Therefore, a neutron star core is potentially a natural lab to study these new degrees of freedom. As these new degrees of freedom appear at the core, they often soften the core, making the tidal deformability of the neutron star larger than expected. Gravitational wave signals encode the tidal deformability and, therefore, the microscopic information. However, to extract information on the deformability, one relies on either spectral parametrization of equations of state(EoSs) or the EoS insensitive relation. This dissertation points out that the two methods (spectral parametrization and EoS insensitive relation) can be misleading or smear out the microscopic information within a neutron star core. To utilize gravitational wave observations, one needs to parametrize phase transitions and crossovers due to new degrees of freedom. With the parametrization at hand, one can conduct a Bayesian analysis to see how these new degrees of freedom affect the wave signal. The parametrization is thoroughly studied in this dissertation and the Bayesian analysis is left for future work. The other microscopic physics this dissertation focuses on is the Twin Mirror Hiiggs model. This model is motivated as a solution to the hierarchy problem in particle physics, and the model predicts a sector of particles. This sector, referred to as the mirror sector, is a copy of the standard model sector except for the vacuum expectation value f. Once this model is motivated as a dark matter model, there can be dark planets, dark stars, and dark galaxies, filling our universe. This dissertation studies neutron stars composed of mirror dark matter or both mirror dark matter and standard model matter. We point out that these two stars can be observed using gravitational waves, and one can distinguish them from a neutron star or a black hole. If we were to detect them, we would find dark matter. However, the value of f must be in a certain range to solve the hierarchy problem. In this dissertation, we indicate that it is possible to confuse a mirror neutron star with a mirror-matter admixed neutron star, which leads to a false inference of f. A Bayesian analysis must be conducted to see whether gravitational wave observations can distinguish the two stars. This analysis is left for future work.

Graduation Semester

2023-08

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Hung Tan

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