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Abstract The collision of a primordial black hole with a neutron star results in the black hole eventually consuming the entire neutron star. However, if the black hole is magnetically charged, and therefore stable against decay by Hawking radiation, the consequences can be quite different. Upon colliding with a neutron star, a magnetic black hole very rapidly comes to a stop. For large enough magnetic charge, we show that this collision can be detected as a sudden change in the rotation period of the neutron star, a glitch or anti-glitch.We argue that the magnetic primordial black hole, which then settles to the core of the neutron star, does not necessarily devour the entire neutron star; the system can instead reach a long-lived, quasi-stable equilibrium. Because the black hole is microscopic compared to the neutron star, most stellar properties remain unchanged compared to before the collision. However, the neutron star will heat up and its surface magnetic field could potentially change, both effects potentially observable. 

A bstract We study a strongly interacting, fermionic fluid in the presence of an applied magnetic field using a holographic framework. At low temperatures, translation symmetry is spontaneously broken and the resulting phase is a striped Hall fluid. Due to the magnetic field, an electric field applied parallel to the stripes causes the stripes to slide, a phenomenon we coin “Hall sliding.” We also investigate the magneto-transport of the system in the presence of an explicit translation symmetry-breaking lattice which pins the stripes. Electrical properties are well represented by a hydrodynamical model, which gives us further insight into particle-like cyclotron and pseudo-Goldstone excitations we observe. The DC conductivities obey a novel semi-circle law, which we derive analytically in the translationally invariant ground state at low temperature.