Physics Commons^™

Cosmological Vector Fields And Constraining The Neutrino Masses, Avery J. Tishue

Dartmouth College Ph.D Dissertations

In this thesis I explore two main topics: the role and consequences of cosmological vector fields, and new ideas for constraining fundamental physics with state-of-the-art experiments. These topics are disparate in content and technique but unified in their attempt to leverage novel approaches to better understand longstanding questions in cosmology. These questions, such as ``What is causing the universe to accelerate today?'' and ``What are the neutrino masses?'', underpin the modern cosmological paradigm. They play a key role in our understanding of cosmic history, the formation of structure, and the fate of our universe. Answers to or hints about these …

New Physics In The Age Of Precision Cosmology, Vivian I. Sabla

Dartmouth College Ph.D Dissertations

The Lambda-cold dark matter (LCDM) model has become the standard model of cosmology because of its ability to reproduce a vast array of cosmological observations, from the earliest moments of our Universe, to the current period of accelerated expansion, which it does with great accuracy. However, the success of this model only distracts from its inherent flaws and ambiguities. LCDM is purely phenomenological, providing no physical explanation for the nature of dark matter, responsible for the formation and evolution of large-scale structure, and giving an inconclusive explanation for dark energy, which drives the current period of accelerated expansion.

Furthermore, cracks …

Aspects On The Quantum Dynamics Of A System Coupled To A Bosonic Environment, Qidong Xu

Dartmouth College Ph.D Dissertations

In this work we study various aspects of the quantum dynamics for a system coupled to a Bosonic environment, which is described by a collection of quantum harmonic oscillators or a quantum field. We first consider two quantum mechanical oscillator system-bath models obtained by dimensionally truncating linearized gravity coupled to a massive scalar field and scalar QED, and we show that they separately map onto the phase damped oscillator model and the oscillator system subject to two-photon damping. The phase damped oscillator model also corresponds to the optomechanical system with an acoustic field environment, and we study the acoustic environment …

Class Of Nonperturbative Configurations In Abelian-Higgs Models: Complexity From Dynamical Symmetry Breaking, M. Gleiser, J. Thorarinson

Dartmouth Scholarship

We present a numerical investigation of the dynamics of symmetry breaking in both Abelian and non-Abelian [SU(2)] Higgs models in three spatial dimensions. We find a class of time-dependent, long-lived nonperturbative field configurations within the range of parameters corresponding to type-1 superconductors, that is, with vector masses (mv) larger than scalar masses (ms). We argue that these emergent nontopological configurations are related to oscillons found previously in other contexts. For the Abelian-Higgs model, our lattice implementation allows us to map the range of parameter space—the values of β=(ms/mv)2—where such configurations exist and to follow them for times t∼O(105)m−1. An investigation …

Cosmic Shear Of The Microwave Background: The Curl Diagnostic, Asantha Cooray, Marc Kamionkowski, Robert R. Caldwell

Dartmouth Scholarship

Weak-lensing distortions of the cosmic-microwave-background (CMB) temperature and polarization patterns can reveal important clues to the intervening large-scale structure. The effect of lensing is to deflect the primary temperature and polarization signal to slightly different locations on the sky. Deflections due to density fluctuations, gradient-type for the gradient of the projected gravitational potential, give a direct measure of the mass distribution. Curl-type deflections can be induced by, for example, a primordial background of gravitational waves from inflation or by second-order effects related to lensing by density perturbations. Whereas gradient-type deflections are expected to dominate, we show that curl-type deflections can …