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Axions in a Dark Universe: Dark Matt...

Allali, Itamar J.

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Axions in a Dark Universe: Dark Matter Behavior and Novel Dynamics Inform Cosmological Observations.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Axions in a Dark Universe: Dark Matter Behavior and Novel Dynamics Inform Cosmological Observations./
Author:	Allali, Itamar J.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2023,
Description:	269 p.
Notes:	Source: Dissertations Abstracts International, Volume: 84-11, Section: B.
Contained By:	Dissertations Abstracts International84-11B.
Subject:	Theoretical physics. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30422977
ISBN:	9798379562823

Axions in a Dark Universe: Dark Matter Behavior and Novel Dynamics Inform Cosmological Observations.
Allali, Itamar J.

Axions in a Dark Universe: Dark Matter Behavior and Novel Dynamics Inform Cosmological Observations. - Ann Arbor : ProQuest Dissertations & Theses, 2023 - 269 p.

Source: Dissertations Abstracts International, Volume: 84-11, Section: B.

Thesis (Ph.D.)--Tufts University, 2023.

This item must not be sold to any third party vendors.

Despite its crucial role in cosmology, little is known about the precise nature of dark matter. This work investigates the nature of dark matter, primarily the QCD axion and other axion-like particles, which are motivated from particle physics. First, I explore the possibility of long-lived quantum superpositions of macroscopic dark matter states in the galaxy. Schrodinger cat states, which typically decohere rapidly from environmental interactions, may persist due to dark matter's infrequent interactions. In this work, I describe the decoherence of these states by gravitational interactions, considering Newtonian gravity and General Relativity. Axion dark matter superpositions of differing mass distributions may rapidly decohere, while those of the phase of axion oscillations are generally robust to decoherence in nonrelativistic scenarios. Next, new effective theories of the QCD axion are presented, which expand the viable range of axion masses. Coupling the axion to new scalars renders the effective PQ symmetry-breaking scale dynamical, allowing heavier axions to be compatible with the observed dark matter abundance and preventing the overproduction of lighter axions from overclosing the universe. These models are motivated by observational hints, such as anomalous cooling of horizontal branch stars, and by fundamental physics, including the possibility of a lighter axion from GUT-scale physics. Lastly, I study tensions in the measurements of (i) the Hubble rate of expansion of the universe today (H0) and (ii) matter clustering (S8), and I propose a dark sector model to address them. This adds a decaying dark energy and ultra-light axion to ΛCDM, accommodating a larger H0 and a smaller S8 while fitting CMB, BAO, and LSS data. The axion is rooted in particle physics, while the fundamental realization of the decaying dark energy needs further study. In summary, this work explores the behavior of dark matter axions in several contexts, examining the implications for observations and cosmology as a whole.

ISBN: 9798379562823Subjects--Topical Terms:

2144760
Theoretical physics.
Subjects--Index Terms:

Axions

Axions in a Dark Universe: Dark Matter Behavior and Novel Dynamics Inform Cosmological Observations.
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245 1 0 $a Axions in a Dark Universe: Dark Matter Behavior and Novel Dynamics Inform Cosmological Observations.
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300 $a 269 p.
500 $a Source: Dissertations Abstracts International, Volume: 84-11, Section: B.
500 $a Advisor: Hertzberg, Mark P.
502 $a Thesis (Ph.D.)--Tufts University, 2023.
506 $a This item must not be sold to any third party vendors.
520 $a Despite its crucial role in cosmology, little is known about the precise nature of dark matter. This work investigates the nature of dark matter, primarily the QCD axion and other axion-like particles, which are motivated from particle physics. First, I explore the possibility of long-lived quantum superpositions of macroscopic dark matter states in the galaxy. Schrodinger cat states, which typically decohere rapidly from environmental interactions, may persist due to dark matter's infrequent interactions. In this work, I describe the decoherence of these states by gravitational interactions, considering Newtonian gravity and General Relativity. Axion dark matter superpositions of differing mass distributions may rapidly decohere, while those of the phase of axion oscillations are generally robust to decoherence in nonrelativistic scenarios. Next, new effective theories of the QCD axion are presented, which expand the viable range of axion masses. Coupling the axion to new scalars renders the effective PQ symmetry-breaking scale dynamical, allowing heavier axions to be compatible with the observed dark matter abundance and preventing the overproduction of lighter axions from overclosing the universe. These models are motivated by observational hints, such as anomalous cooling of horizontal branch stars, and by fundamental physics, including the possibility of a lighter axion from GUT-scale physics. Lastly, I study tensions in the measurements of (i) the Hubble rate of expansion of the universe today (H0) and (ii) matter clustering (S8), and I propose a dark sector model to address them. This adds a decaying dark energy and ultra-light axion to ΛCDM, accommodating a larger H0 and a smaller S8 while fitting CMB, BAO, and LSS data. The axion is rooted in particle physics, while the fundamental realization of the decaying dark energy needs further study. In summary, this work explores the behavior of dark matter axions in several contexts, examining the implications for observations and cosmology as a whole.
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