Black hole-naked singularity dualism and the repulsion of two Kerr black holes due to spin-spin interaction

We report about the possibility for interacting Kerr sources to exist in two different states - black holes or naked singularities - both states characterized by the same masses and angular momenta. Another surprising discovery reported by us is that in spite of the absence of balance between two Kerr black holes, the latter nevertheless can repel each other, which provides a good opportunity for experimental detection of the spin-spin repulsive force through the observation of astrophysical black-hole binaries.Comment: 5 pages, 2 figures: a misprint in formula (3) rectified; published versio

On electromagnetic energy in Bardeen and ABG spacetimes

We demonstrate that the total energy of electromagnetic field in the Bardeen and Ay\'on-Beato-Garc\'ia singularity-free models is equal to the mass parameter $M$, being therefore independent of the charge parameter $Q$. Our result is fully congruent with the original idea of Born and Infeld to use nonlinear electrodynamics for proving the electromagnetic nature of mass.Comment: 10 pages, 3 figure

Precision heat forming of tetrafluoroethylene tubing

An invention that provides a method of altering the size of tetrafluoroethylene tubing which is only available in limited combination of wall thicknesses and diameter are discussed. The method includes the steps of sliding the tetrafluoroethylene tubing onto an aluminum mandrel and clamping the ends of the tubing to the mandrel by means of clamps. The tetrafluorethylene tubing and mandrel are then placed in a supporting coil which with the mandrel and tetrafluorethylene tubing are then positioned in a insulated steel pipe which is normally covered with a fiber glass insulator to smooth out temperature distribution therein. The entire structure is then placed in an event which heats the tetrafluorethylene tubing which is then shrunk by the heat to the outer dimension of the aluminum mandrel. After cooling the aluminum mandrel is removed from the newly sized tetrafluorethylene tubing by a conventional chemical milling process