11 research outputs found
Noncommutative deformation of four dimensional Einstein gravity
We construct a model for noncommutative gravity in four dimensions, which
reduces to the Einstein-Hilbert action in the commutative limit. Our proposal
is based on a gauge formulation of gravity with constraints. While the action
is metric independent, the constraints insure that it is not topological. We
find that the choice of the gauge group and of the constraints are crucial to
recover a correct deformation of standard gravity. Using the Seiberg-Witten map
the whole theory is described in terms of the vierbeins and of the Lorentz
transformations of its commutative counterpart. We solve explicitly the
constraints and exhibit the first order noncommutative corrections to the
Einstein-Hilbert action.Comment: LaTex, 11 pages, comments added, to appear in Classical and Quantum
Gravit
Variable rest masses in 5-dimensional gravitation confronted with experimental data
Cosmological solutions of Einstein equation for a \mbox{5-dimensional}
space-time, in the case of a dust-filled universe, are presented. With these
solutions we are able to test a hypothetical relation between the rest mass of
a particle and the dimension. Comparison with experiment strongly
refutes the implied dependence of the rest mass on the cosmological time.Comment: Some references adde
Vertex Operators for Closed Superstrings
We construct an iterative procedure to compute the vertex operators of the
closed superstring in the covariant formalism given a solution of IIA/IIB
supergravity. The manifest supersymmetry allows us to construct vertex
operators for any generic background in presence of Ramond-Ramond (RR) fields.
We extend the procedure to all massive states of open and closed superstrings
and we identify two new nilpotent charges which are used to impose the gauge
fixing on the physical states. We solve iteratively the equations of the vertex
for linear x-dependent RR field strengths. This vertex plays a role in studying
non-constant C-deformations of superspace. Finally, we construct an action for
the free massless sector of closed strings, and we propose a form for the
kinetic term for closed string field theory in the pure spinor formalism.Comment: TeX, harvmac, amssym.tex, 41 pp; references adde
Construction of an SO(10) x U(1)_F Model of the Yukawa Interactions
We construct a supersymmetric model of the Yukawa
interactions at the grand unification scale from knowledge of a
phenomenological set of mass matrices obtained by a previous bottom-up
approach. The family symmetry determines the textures for the Majorana
and generic Dirac mass matrices, while the symmetry relates each
particular element of the up, down, neutrino and charged lepton Dirac matrices.
The dominant second and third family contributions in the Dirac sector are
renormalizable, while the remaining contributions to the Dirac mass matrices
are of higher order, restricted by the family symmetry to a small set
of tree diagrams, and mainly complex-symmetric. The tree diagrams for the
Majorana mass matrix are all non-renormalizable and of progressively
higher-order, leading to a nearly geometrical structure. Pairs of and Higgs representations enter with those having large vacuum
expectation values breaking the symmetry down to near the grand unification scale. In terms of 12 parameters expressed
as the Yukawa couplings times vacuum expectation values for the Higgs
representations employed, a realistic set of 15 quark and lepton masses
(including those for the 3 heavy righthanded Majorana neutrinos) and 8 mixing
parameters emerges for the neutrino scenario involving the non-adiabatic
conversion of solar neutrinos and the depletion of atmospheric muon-neutrinos
through oscillations into tau-neutrinos.Comment: 32 pages, latex with style files attached, 1 figure in uuencoded
postscript fil