COLLISION ENERGY IN THE CENTER-OF-MASS FRAME FOR ROTATING AND ACCELERATING BLACK HOLES

The center-of-mass (CM) energy of collision for two uncharged particles falling freely from rest at infinity is investigated in the background of charged, rotating and accelerating black hole. It is found that the CM energy of collision is unlimited at the acceleration horizon and at the event horizon (in the extremal case) if one of the colliding particles has critical angular momentum and the other one has a proper angular momentum such that the particle can reach the horizon.

ON SOME GRAVITOMAGNETIC SPIN–SPIN EFFECTS FOR ASTRONOMICAL BODIES

In this paper we look at the gravitational spin–spin interaction between macroscopic astronomical bodies. In particular, we calculate their post-Newtonian orbital effects of order [Formula: see text] on the trajectory of a spinning particle with proper angular momentum s moving in the external gravitomagnetic field generated by a central spinning mass with proper angular momentum J. It turns out that, at order [Formula: see text] in the orbiter's eccentricity, the eccentricity the pericenter and the mean anomaly rates of the moving particle are affected by long-term harmonic effects. If, on one hand, they are undetectable in the Solar System, on the other, maybe in an astrophysical context like that of the binary millisecond pulsars there will be some hopes of measuring them in the future, provided that substantial improvements in the accuracy of the detection of the periastron rate will occur.