Higher Dimensional Defects in Cosmology.
Abstract: Extra dimensions seem to be an important ingredient for unification
of gravity with quantum field theory. Our best candidate of quantum gravity, superstring
theory, requires ten-dimensional space-time for mathematical consistency. However, since
our world appears four-dimensional there must be a mechanism that "hides" extra dimensions
so that we do not experience them at low energy s... read morecale. There are several methods in
literature for concealing extra dimensions from our naked eye. In this thesis we only focus
on two of them: braneworld scenario and flux compactification, both of which require the
existence of the bulk fields. This thesis investigates the role topological defects can
play as bulk fields in higher-dimensional cosmology with different asymptotic topology. The
first part deals with the non-singular braneworld: Skyrme branes and its higher dimensional
generalizations. We show how these defects regularize the naked singularity around the core
while at the same time approach the same flat asymptotic behavior as the known thin-wall
solutions. The second part is devoted to study an exotic transition, tunneling to (and
from) nothing, in a landscape where the space-time vacua are direct products of X4 × S2,
with X4 can be: anti-de Sitter (AdS4), Minkowski (M4), or de Sitter (dS4). The tunneling is
mediated by instanton solutions, via bubble nucleation. The bubble wall is smooth and
magnetically-charged, and we show that this can be accomplished by having solitonic brane
possessing magnetic charge, i.e., magnetic-monopole branes.
Thesis (Ph.D.)--Tufts University, 2011.
Submitted to the Dept. of Physics.
Advisor: Jose Blanco-Pillado.
Committee: Alexander Vilenkin, Ken Olum, Krzysztof Sliwa, and Tanmay Vachaspati.
Keyword: Physics.read less