59 research outputs found
Black Holes with Weyl Charge and Non-Riemannian Waves
A simple modification to Einstein's theory of gravity in terms of a
non-Riemannian connection is examined. A new tensor-variational approach yields
field equations that possess a covariance similar to the gauge covariance of
electromagnetism. These equations are shown to possess solutions analogous to
those found in the Einstein-Maxwell system. In particular one finds
gravi-electric and gravi-magnetic charges contributing to a spherically
symmetric static Reissner-Nordstr\"om metric. Such Weyl ``charges'' provide a
source for the non-Riemannian torsion and metric gradient fields instead of the
electromagnetic field. The theory suggests that matter may be endowed with
gravitational charges that couple to gravity in a manner analogous to
electromagnetic couplings in an electromagnetic field. The nature of
gravitational coupling to spinor matter in this theory is also investigated and
a solution exhibiting a plane-symmetric gravitational metric wave coupled via
non-Riemannian waves to a propagating spinor field is presented.Comment: 18 pages Plain Tex (No Figures), Classical and Quantum Gravit
Octonionic representations of Clifford algebras and triality
The theory of representations of Clifford algebras is extended to employ the
division algebra of the octonions or Cayley numbers. In particular, questions
that arise from the non-associativity and non-commutativity of this division
algebra are answered. Octonionic representations for Clifford algebras lead to
a notion of octonionic spinors and are used to give octonionic representations
of the respective orthogonal groups. Finally, the triality automorphisms are
shown to exhibit a manifest \perm_3 \times SO(8) structure in this framework.Comment: 33 page
Optical integration and verification of LINC-NIRVANA
The LBT (Large Binocular Telescope) located in Mount Graham near Tucson/Arizona at an altitude of about 3200m, is an innovative project being undertaken by institutions from Europe and USA. The structure of the telescope incorporates two 8.4-meter telescopes on a 14.4 center-to-center common mount. This configuration provides the equivalent collecting area of a 12m single-dish telescope. LINC-NIRVANA is an instrument to combine the light from both LBT primary mirrors in an imaging Fizeau interferometer. Many requirements must be fulfilled in order to get a good interferometric combination of the beams, being among the most important plane wavefronts, parallel input beams, homotheticity and zero optical path difference (OPD) required for interferometry. The philosophy is to have an internally aligned instrument first, and then align the telescope to match the instrument. The sum of different subsystems leads to a quite ambitious system, which requires a well-defined strategy for alignment and testing. In this paper I introduce and describe the followed strategy, as well as the different solutions, procedures and tools used during integration. Results are presented at every step
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