|dc.description.abstract||We study questions relating to quantum gravity.
The first part of this dissertation studies the degrees of freedom of
non-commutative field theories. This class of theories presents an interesting
playground for studying the UV-IR connection, a property assumed to hold in
any theory of quantum gravity. To study these degrees of freedom, we submit
the theories to a heat bath. We study a variety of theories with very different
UV behavior. In all cases, we find indications in the non-planar sector for a
reduced number of degrees of freedom at temperatures high with regard to the
non-commutativity scale. Furthermore, the free energy in this sector exhibits
a form which is suggestive of winding states in the spectrum.
The starting point of the second part are recent astronomical observations
that suggest that the universe is accelerating. Quintessence space-times
have been proposed as alternative to asymptotic de Sitter spaces in order to
accommodate these observations while bypassing the conceptual difficulties
the latter pose for string theory. We argue that generic quintessence models
that accommodate the present day acceleration tend to accelerate eternally.
This implies that they exhibit horizons and hence pose the same problems for
string theory as asymptotic de Sitter spaces.
In the final part of this dissertation, we use open string mirror symmetry
to calculate Ooguri-Vafa disk invariants of non-linear sigma models using
the mirror Landau-Ginzburg theories. The target spaces we consider are the
Calabi-Yau spaces obtained as the total space of the anticanonical line bundle
of multiple blowups of the toric varieties P
2 and F2. Checking the integrality
of the invariants requires calculating quantum corrections to the boundary
variables. We show that these can be completely determined by using discrete
symmetries of the superpotential of the mirror theory.||
|dc.rights||Copyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works.||en
|dc.title||Topics in gravity||en
|thesis.degree.grantor||The University of Texas at Austin||en
|thesis.degree.name||Doctor of Philosophy||en