What a difference a quadrupole makes?

Understand

We consider some implications of the departure from spherical symmetry for static solutions of the vacuum Einstein's equations describing black hole mimickers.

• In particular, we investigate how the presence of mass quadrupole moment affects the collision energy of test particles.
• We show that collision processes in the vicinity of such exotic compact sources with non vanishing mass quadrupole moment may be significantly different from those in the vicinity of black holes.