FöRFATTARE
Sunhede, Daniel

DATUM
2003-10-23

INSTITUTION
Kiruna rymd- och miljöcampus

SAMMANFATTNING
Recent observations indicate that the majority of all matter in the universe is in the form of a dark energy component, causing the universe to accelerate. An attractrive solution to this scenario would be quintessence, i.e. a model in which the dark energy stems from a scalar field, causing an effective cosmological constant that accelerates the universe.

This master thesis begins with a review of the standard big bang scenario and the present observational situation. We continue with reviewing quintessence, in particular the natural quintessence scenario. Finally, we explore in detail a recent model by Albrecht, Burgess, Ravndal and Skordis, where the possible existence of two large extra dimensions give rise to a quintessence field in our 4-dimensional picture of the world [Phys. Rev. D65 (2002) 123507 and astro-ph/0207174]. We find that when astrophysical constraints are correctly accounted for, they seem to spoil the perturbative expansion employed by Albrecht et al. However, if one improves on these approximations, it turns out that the scenario is salvageable with the sacrifice of fine-tuning parameters to an anomalously large one-loop correction, while two and higher order loop corrections can be small.

ISSN 1402-1617 / ISRN LTU-EX--03/332--SE / NR 2003:332