Citation
Jenkins, Alejandro (2006) Topics in particle physics and cosmology beyond the standard model. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd06022006145211
Abstract
We review our understanding of spin1 and spin2 massless particles as mediators of longrange forces. We discuss how a quantum description of such particles that is compatible with Lorentz covariance leads to gauge invariance, a mathematical redundancy in the description of the physics. We discuss the WeinbergWitten theorem, which underlines the need for gauge invariance in relativistic theories with massless mediators of higher spin.
This leads us to consider a class of models in which longrange interactions are mediated by the Goldstone bosons of spontaneous Lorentz violation. Since the Lorentz symmetry is realized nonlinearly in the Goldstones, these models could evade the WeinbergWitten theorem and the need for gauge invariance. In the case of gravity, the broken symmetry would protect the theory from having nonzero cosmological constant, while the compositeness of the graviton could provide a solution to the perturbative nonrenormalizability of gravity.
Next we consider the phenomenology of spontaneous Lorentz violation and the experimental limits thereon. We find the general lowenergy effective action of the Goldstones of this kind of symmetry breaking minimally coupled to gravity. We compare this effective theory to the ghost condensate that has been proposed in the literature as a model for gravity in a Higgs phase. We compute the modification to Newton's law from this mechanism and discuss observational limits on this kind of Lorentz violation from solar system tests of gravity and from gravitational Cherenkov radiation of cosmic rays.
We then summarize the cosmological constant problems and show that models in which a scalar field causes superacceleration of the universe generally exhibit instabilities connected to violation of the nullenergy condition. We discuss how the equation of state evolves in a universe where the dark energy is caused by a ghost condensate. We comment on the anthropic argument for a small cosmological constant and how it is weakened if the inflaton selfcoupling varies over the landscape of possible universes.
Finally, we discuss the reverse sprinkler, a problem in elementary fluid mechanics that had eluded a definitive treatment for decades.
Item Type:  Thesis (Dissertation (Ph.D.)) 

Subject Keywords:  cosmological constant; cosmology; dark energy; gauge theories; Lorentz violation; reverse sprinkler; vectortensor theories 
Degree Grantor:  California Institute of Technology 
Division:  Physics, Mathematics and Astronomy 
Major Option:  Physics 
Thesis Availability:  Public (worldwide access) 
Research Advisor(s): 

Thesis Committee: 

Defense Date:  26 May 2006 
Author Email:  jenkins (AT) theory.caltech.edu 
Record Number:  CaltechETD:etd06022006145211 
Persistent URL:  http://resolver.caltech.edu/CaltechETD:etd06022006145211 
Default Usage Policy:  No commercial reproduction, distribution, display or performance rights in this work are provided. 
ID Code:  2403 
Collection:  CaltechTHESIS 
Deposited By:  Imported from ETDdb 
Deposited On:  05 Jun 2006 
Last Modified:  26 Dec 2012 02:50 
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