Please refer to http://www.tachyonics.com/, which says:
"There is no isolated negative mass as far as we know in our universe. But the mechanism of Dipole Anti-Gravity creates temporary negative mass in pair with the positive mass when there exists an angular momentum for a longitudinally asymmetric rotating object. This is the key of the secret of the universe."
"[The graphic diagram] means that when a spherical shell rotates, there appears the dynamic potential along the rotation axis within the shell. The force created by this potential is strongly attractive near the poles and then suddenly becomes repulsive as the particle gets closer toward the center. As they reach this repulsive potential region, the particles get ejected toward the poles and out of the shell until they reach the point where they have initially started to approach the shell. Therefore, each jet consists of a two-way stream of particles.
One may call them the linear trajectories. The length of the jet is determined by the height of the repulsive potential, which again depends on the rotational frequency of the object. The incoming and outgoing particles are colliding along their path and they create enormous amount of radiation.
When the speed of the rotation of the body is not large, the length of the linear trajectory will not be long. And the particles will rapidly oscillate back and forth which can create radio frequency spectrum since there can be ionization of the particles produced by collision in the process of collective oscillation.
What does the above graph mean? The force toward the side of the saddle looks certainly like the centrifugal force since it depends on the square of the distance from the axis. That's why Thirring called it the "Induced Centrifugal Force" in his paper. Bass and Pirani suspected the interpretation since it can be made to disappear formally by reducing the mass density of the shell of the amount increased by the special relativistic effect. They argued that this should not if the force were truly the centrifugal force. Their fatal mistake was in the fact that they regarded the dynamic mass increase as being the same as the permanent mass density increase.
Later, Cohen speculated intuitively that this force must be due to the quadrupole effect (note the bulging effect of the sphere toward the side) which was a very close observation. Thirring also had the force in the axial direction, which is basically the harmonic oscillator as you can read off from the above graph. Now as you can see, these forces are all due to the dipole effect superposed inside a rotating spherical mass shell and the cause for the jets."
http://xxx.lanl.gov/find/hep-ph/1/eue+jin+jeong/0/1/0/97/1/0 -- "Neutrinos Must Be Tachyons"
http://xxx.lanl.gov/find/gr-qc/1/Eue+Jin+Jeong/0/1/0/all/1/1 -- Dipole antigravity collection of papers