| dc.description.abstract | In this thesis some aspects of temperature corrections in string theory are analyzed: in
particular, we study the thermal contributions to the 4 dimensional effective potential
arising from string theory compactifications.
String theory predicts that the spacetime has more than 4 dimensions; in particular,
supersymmetric string theories are consistent only if the spacetime has 10 dimensions,
1 time plus 9 space directions. In order to describe the physics of our Universe
with string theory we make 6 spatial directions very small, namely, we curl them
into a 6-dimensional space. The resulting 4-dimensional theory depends on a large
number of parameters which are massless scalar fields called moduli. The different
values that the moduli can take represent both the possible deformations of the 6-
dimensional compact space and the values of the coupling constants and masses in
the 4-dimensional spacetime. Allowing them to have arbitrary values leads to a lack
of predictability of various 4D physical quantities, to a huge vacuum degeneracy and
to unobserved long range fifth forces.
In the thesis we review some methods established in the literature in order to fix the moduli values and hence to fix a particular geometry and we investigate how
the inclusion of temperature corrections alter their values and affect the geometry
of the compact space. The analysis seems to suggest that at least in the specific
compactification scenarios considered in this thesis, temperature corrections do not
alter substantially the zero temperature results.
In the final part of this work, we analyze instead an example in which the inclusion
of temperature corrections alters dramatically the picture at zero temperature. In
particular, we study an unstable system constituted by a pair of Dirichlet (D) and
anti-D brane that, although being unstable at zero temperature, it can become stable
once finite temperature corrections are switched on. | en_US |
