Decay of Oscillating Universes
Mithani, Audrey.
2016
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Abstract: It has been suggested by Ellis {\emph{et al}} \cite{EM2004,Murugan}
that the universe could be eternal in the past, without beginning. In their model, the
``emergent universe'' exists forever in the past, in an ``eternal'' phase before inflation
begins. We will show that in general, such an ``eternal'' phase is not possible, because of
an instability due to quantum tunneling. One ... read morecandidate model, the ``simple harmonic
universe'' has been shown by Graham {\emph{et al}} \cite{Graham} to be perturbatively
stable; we find that it is unstable with respect to quantum tunneling. We also investigate
the stability of a distinct oscillating model in loop quantum cosmology with respect to
small perturbations and to quantum collapse. We find that the model has perturbatively
stable and unstable solutions, with both types of solutions occupying significant regions
of the parameter space. All solutions are unstable with respect to collapse by quantum
tunneling to zero size. In addition, we investigate the effect of vacuum corrections, due
to the trace anomaly and the Casimir effect, on the stability of an oscillating universe
with respect to decay by tunneling to the singularity. We find that these corrections do
not generally stabilize an oscillating universe. Finally, we determine the decay rate of
the oscillating universe. Although the wave function of the universe lacks explicit time
dependence in canonical quantum cosmology, time evolution may be present implicitly through
the semiclassical superspace variables, which themselves depend on time in classical
dynamics. Here, we apply this approach to the simple harmonic universe, by extending the
model to include a massless, minimally coupled scalar field $\phi$ which has little effect
on the dynamics but can play the role of a ``clock''.
Thesis (Ph.D.)--Tufts University, 2016.
Submitted to the Dept. of Physics.
Advisor: Alexander Vilenkin.
Committee: Krzysztof Sliwa, Jaume Garriga, Ken Olum, and Lawrence Ford.
Keywords: Physics, Theoretical physics, and Astrophysics.read less - ID:
- g445cr73t
- Component ID:
- tufts:21261
- To Cite:
- TARC Citation Guide EndNote
