5 research outputs found
Classical and Quantum Considerations of Two-dimensional Gravity
The two-dimensional theory of gravity describing a graviton-dilaton system is
considered. The graviton-dilaton coupling can be fixed such that the quantum
theory remains free of the conformal anomaly for any conformal dimension of the
coupled matter system, even if the dilaton does not appear as Lagrange
multiplier. Interaction terms are introduced and the system is analyzed and
solutions are given at the classical level and at the quantum level by using
canonical quantization.Comment: 18 page
Avoiding degenerate coframes in an affine gauge approach to quantum gravity
In quantum models of gravity, it is surmized that configurations with
degenerate coframes could occur during topology change of the underlying
spacetime structure. However, the coframe is not the true Yang--Mills type
gauge field of the translations, since it lacks the inhomogeneous gradient term
in the gauge transformations. By explicitly restoring this ``hidden" piece
within the framework of the affine gauge approach to gravity, one can avoid the
metric or coframe degeneracy which would otherwise interfere with the
integrations within the path integral. This is an important advantage for
quantization.Comment: 14 pages, Preprint Cologne-thp-1993-H
On 'Light' Fermions and Proton Stability in 'Big Divisor' D3/D7 Swiss Cheese Phenomenology
Building up on our earlier work [1,2], we show the possibility of generating
"light" fermion mass scales of MeV-GeV range (possibly related to first two
generations of quarks/leptons) as well as eV (possibly related to first two
generations of neutrinos) in type IIB string theory compactified on
Swiss-Cheese orientifolds in the presence of a mobile space-time filling
D3-$brane restricted to (in principle) stacks of fluxed D7-branes wrapping the
"big" divisor \Sigma_B. This part of the paper is an expanded version of the
latter half of section 3 of a published short invited review [3] written up by
one of the authors [AM]. Further, we also show that there are no SUSY GUT-type
dimension-five operators corresponding to proton decay, as well as estimate the
proton lifetime from a SUSY GUT-type four-fermion dimension-six operator to be
10^{61} years. Based on GLSM calculations in [1] for obtaining the geometric
Kaehler potential for the "big divisor", using further the Donaldson's
algorithm, we also briefly discuss in the first of the two appendices,
obtaining a metric for the Swiss-Cheese Calabi-Yau used, that becomes Ricci
flat in the large volume limit.Comment: v2: 1+25 pages, Title modified and text thoroughly expanded including
a brief discussion on obtaining Ricci-flat Swiss Cheese Calabi-Yau metrics
using the Donaldson's algorithm, references added, to appear in EPJ
Fermion Masses and Mixing in Intersecting Branes Scenarios
We study the structure of Yukawa couplings in intersecting D6-branes wrapping
a factorizable 6-torus compact space T^6. Models with MSSM-like spectrum are
analyzed and found to fail in predicting the quark mass spectrum because of the
way in which the family structure for the left-handed, right-handed quarks and,
eventually, the Higgses is `factorized' among the different tori. In order to
circumvent this, we present a model with three supersymmetric Higgs doublets
which satisfies the anomaly cancellation condition in a more natural way than
the previous models, where quarks were not treated universally regarding their
branes assignments, or some particular branes were singled out being invariant
under orientifold projection. In our model, the family structures for the left,
right quarks, left leptons and the Higgses arise from one of the tori and can
naturally lead to universal strength Yukawa couplings which accommodate the
quark mass hierarchy and the mixing angles.Comment: 21 pages, latex, matches the Phys. Rev. D versio