The principle of equivalence and projective structure in space-times

This paper discusses the extent to which one can determine the space-time metric from a knowledge of a certain subset of the (unparametrised) geodesics of its Levi-Civita connection, that is, from the experimental evidence of the equivalence principle. It is shown that, if the space-time concerned is known to be vacuum, then the Levi-Civita connection is uniquely determined and its associated metric is uniquely determined up to a choice of units of measurement, by the specification of these geodesics. It is further demonstrated that if two space-times share the same unparametrised geodesics and only one is assumed vacuum then their Levi-Civita connections are again equal (and so the other metric is also a vacuum metric) and the first result above is recovered.Comment: 23 pages, submitted to Classical and Quantum Gravit

On the Theory of Killing Orbits in Space-Time

This paper gives a theoretical discussion of the orbits and isotropies which arise in a space-time which admits a Lie algebra of Killing vector fields. The submanifold structure of the orbits is explored together with their induced Killing vector structure. A general decomposition of a space-time in terms of the nature and dimension of its orbits is given and the concept of stability and instability for orbits introduced. A general relation is shown linking the dimensions of the Killing algebra, the orbits and the isotropies. The well-behaved nature of "stable" orbits and the possible miss-behaviour of the "unstable" ones is pointed out and, in particular, the fact that independent Killing vector fields in space-time may not induce independent such vector fields on unstable orbits. Several examples are presented to exhibit these features. Finally, an appendix is given which revisits and attempts to clarify the well-known theorem of Fubini on the dimension of Killing orbits.Comment: Latex, 19 pages, no figur

Quality-weld parameters for microwelding techniques and equipment

Limited-amplitude, controlled-decay process improves the reliability of microwelding. The system consists in building a capacitor-discharge welder for control of the shape of the weld pulse. Standard welders may be modified

A low‐noise high‐speed diode laser current controller

We describe a new diode laser current controller which features low current noise, excellent dc stability, and the capacity for high‐speed modulation. While it is simple and inexpensive to construct, the controller compares favorably with the best presently available commercial diode laser current controllers

Recent Studies of Nonequilibrium Flows at the Cornell Aeronautical Laboratory

Vibrational relaxation in supersonic nozzle diatomic gas flow, nonequilibrium effects in high enthalpy airflow over thick wedge flat plates, and reentry nonequilibrium flow field

Quality weld parameters for microwelding techniques and equipment Final report

Amplitude controlled welding process for electronic circuit module

Self-similar static solutions admitting a two-space of constant curvature

A recent result by Haggag and Hajj-Boutros is reviewed within the framework of self-similar space-times, extending, in some sense, their results and presenting a family of metrics consisting of all the static spherically symmetric perfect fluid solutions admitting a homothety.Comment: 6 page

Psychological type and attitude towards Celtic Christianity among committed Churchgoers in the United Kingdom: an empirical study

This article takes the burgeoning interest in Celtic Christianity as a key example of the way in which churches may be responding to the changing spiritual and religious landscape in the United Kingdom today and examines the power of psychological type theory to account for variation in the attitude of committed churchgoers to this innovation. Data provided by a sample of 248 Anglican clergy and lay church officers (who completed the Francis Psychological Type Scales together with the Attitude toward Celtic Christianity Scale) demonstrated that intuitive types, feeling types, and perceiving types reported a more positive attitude towards Celtic Christianity than sensing types, thinking types, and judging types. These findings are interpreted to analyse the appeal of Celtic Christianity and to suggest why some committed churchgoers may find this innovation less attractive

Asymptotic iteration method for eigenvalue problems

An asymptotic interation method for solving second-order homogeneous linear differential equations of the form y'' = lambda(x) y' + s(x) y is introduced, where lambda(x) \neq 0 and s(x) are C-infinity functions. Applications to Schroedinger type problems, including some with highly singular potentials, are presented.Comment: 14 page

An effective singular oscillator for Duffin-Kemmer-Petiau particles with a nonminimal vector coupling: a two-fold degeneracy

Scalar and vector bosons in the background of one-dimensional nonminimal vector linear plus inversely linear potentials are explored in a unified way in the context of the Duffin-Kemmer-Petiau theory. The problem is mapped into a Sturm-Liouville problem with an effective singular oscillator. With boundary conditions emerging from the problem, exact bound-state solutions in the spin-0 sector are found in closed form and it is shown that the spectrum exhibits degeneracy. It is shown that, depending on the potential parameters, there may or may not exist bound-state solutions in the spin-1 sector.Comment: 1 figure. arXiv admin note: substantial text overlap with arXiv:1009.159