Physics
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006phdt........36m&link_type=abstract
Proquest Dissertations And Theses 2006. Section 0171, Part 0606 80 pages; [Ph.D. dissertation].United States -- Oregon: Univers
Physics
Universe, Cosmology, Dark Energy
Scientific paper
Some have argued that, we have entered an era of precision cosmology. Results from a number of different types of astronomical observation in recent years suggest that the expansion rate of the universe is currently increasing. Perhaps the most likely candidate to explain this late-time acceleration is a mysterious form of matter, the dark energy, one example of which is a class of scalar field models, referred to as quintessence. We investigate the effects of thermal interactions on tracking models of quintessence. We show that the dark energy equation of state is in many cases strongly affected by matter couplings, and obtain a bound on the coupling between quintessence and relativistic relic particles such as the photon or neutrino.
This is not the only aspect of the dark energy that we explore. We also extend previous work showing that violation of the null energy condition implies instability in a broad class of models, including gauge theories with scalar and fermionic matter as well as any perfect fluid. When applied to the dark energy, our results imply that w = p /[rho] is unlikely to be less than -1.
Additionally, we investigate a more speculative topic with relevance to the early universe: Black hole entropy. Taking seriously the interpretation of black hole entropy as the logarithm of the number of microstates, we argue that thermal gravitons may undergo a phase transition to a kind of black hole condensate. The phase transition proceeds via nucleation of black holes at a rate governed by a saddlepoint configuration whose free energy is of order the inverse temperature in Planck units. Our results may clarify an old observation of Penrose regarding the very low entropy state of the universe.
The topic of this dissertation is the physics of the very early and the very late universe. These are two very interesting epochs for cosmology; the nature of black hole entropy and dark energy are but two of many unresolved issues for future cosmologists to address. This dissertation includes both my previously published and my coauthored materials.
Murray Brian M.
No associations
LandOfFree
Early and late universe cosmology does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Early and late universe cosmology, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Early and late universe cosmology will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1551556