7 research outputs found
Quantum Corrections in Two-Dimensional Non-Supersymmetric Heterotic Strings
We study quantum corrections for a family of 24 non-supersymmetric heterotic
strings in two dimensions. We compute their genus two cosmological constant
using the hyperelliptic formalism and the genus one two-point functions for the
massless states. From here we get the mass corrections to the states in the
massless sector and discuss the role of the infrared divergences that appear in
the computation. We also study some tree-level aspects of these theories and
find that they are classified not only by the corresponding Niemeier lattice
but also by their {\it hidden} right-moving gauge symmetry.Comment: Minor changes. The discussion on the infrared divergences has been
expanded and typos have been corrected. Final version to be published in
Nucl. Phys. B. 40 pages. LaTeX, epsf. 4 Postscript figures in uuencoded fil
Tomographic Representation of Minisuperspace Quantum Cosmology and Noether Symmetries
The probability representation, in which cosmological quantum states are
described by a standard positive probability distribution, is constructed for
minisuperspace models selected by Noether symmetries. In such a case, the
tomographic probability distribution provides the classical evolution for the
models and can be considered an approach to select "observable" universes. Some
specific examples, derived from Extended Theories of Gravity, are worked out.
We discuss also how to connect tomograms, symmetries and cosmological
parameters.Comment: 15 page