148,563 research outputs found
Comment on "Summing One-Loop Graphs at Multi-Particle Threshold"
The propagator of a virtual -field with emission of on-mass-shell
particles all being exactly at rest is calculated at the tree-level in theory by directly solving recursion equations for the sum of Feynman
graphs. It is shown that the generating function for these propagators is
equivalent to a Fourier transform of the recently found Green's function within
the background-field technique for summing graphs at threshold suggested by
Lowell Brown. Also the derivation of the result that the tree-level
on-mass-shell scattering amplitudes of the processes are exactly
vanishing at threshold for is thus given in the more conventional
Feynman diagram technique.Comment: 7 pages, LaTeX, TPI-MINN-92/46-
Selfadjoint and sectorial extensions of Sturm-Liouville operators
The self-adjoint and -sectorial extensions of coercive Sturm-Liouville
operators are characterised, under minimal smoothness conditions on the
coefficients of the differential expression.Comment: accepted by IEOT, in IEOT 201
Nuclear Structure Aspects of Neutrinoless Double Beta Decay
We decompose the neutrinoless double-beta decay matrix elements into sums of
products over the intermediate nucleus with two less nucleons. We find that the
sum is dominated by the J^pi=0^+ ground state of this intermediate nucleus for
both the light and heavy neutrino decay processes. This provides a new
theoretical tool for comparing and improving nuclear structure models. It also
provides the connection to two-nucleon transfer experiments.Comment: 5 pages, 6 figure
Operations with the special purpose dextrous manipulator on Space Station Freedom
SPAR Canada is actively participating in the Space Station Freedom Program by contributing the Mobile Servicing System (MSS) which will be involved in assembly, maintenance and servicing of both the Space Station and the MSS itself. Part of the MSS is the Special Purpose Dextrous Manipulator (SPDM), a two armed dextrous robot with advanced vision and manipulative capabilities. In addition to Space Station and payload servicing activities the SPDM will be designed to perform self maintenance on the MSS itself. The majority of Space Station equipment will be on orbit for the anticipated 30 year lifespan and the maintenance philosophy will be to repair by the exchange of Orbit Replacement Units or ORUs. The present concept, configuration, and operation of the SPDM and the detailed simulations associated with the maintenance of part of the MSS are described. The Design Reference Mission is the replacement of a Joint Drive Module on the Canadian large payload manipulator, the Space Station Remote Manipulator System. Other Design Reference Missions that were investigated are briefly described, and future operations activity to support the definition of SPDM requirements are discussed
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