Investigating new physics with high power lasers

Thesis

This thesis presents theoretical studies of different aspects of axion physics. First, we review the origin of axions from the Peccei-Quinn (PQ) solution to the problem of charge-parity (CP) non-violation in the quantum chromodynamics (QCD) sector of the standard model (SM) of particle physics. An overview of the most common direct and indirect detection efforts is then presented before three distinct, new methods are presented and put in perspective.

Chapter 2 proposes a stimulated version of light shining through wall (LSW) type searches which utilises the large photon numbers in high power laser beams to achieve strong bounds around axion masses of m_a ∼ 1 eV. The sensitivity is evaluated and special care is taken to consider stimulation effects stemming from the large number of photons present. In chapter 3 a new axion-photon parametric decay instability is found and analysed. The coupling of a strong pump and a weaker probe pulse is found to result in an exponentially growing axion mode. The prospect for direct detection experiments is discussed and put into perspective of ongoing searches. The axion's coupling to fermions is investigated in chapter 4 in which the decay of axions to electron-positron pairs in a strong background field is investigated. The chapter starts with a review of strong field quantum electrodynamics techniques and then proceeds by applying them to the axion coupling to identify different regimes based on the axion's mass and the background field strength.

The second part of the thesis investigates the cosmological implications of including axions into the SM. A review of the standard ΛCDM cosmology is followed by a discussion of the cosmological importance of the axion by an investigation of the energy density in a coherent axion field throughout the universe which could constitute the dark matter. An investigation of topological defects formed during the symmetry breaking stages of the axion then leads to the introduction of the domain wall problem. Chapter 6 is dedicated to the solution of the domain wall problem and finishes with a lookout onto avenues for future investigations and attempts at solutions.

Authors: Beyer, K

• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: Axion Detection; Axion Cosmology; Axion Physics
• Subjects: Phenomenological theory (Physics)