Phase Transitions in Frustrated Slightly Nonstoichiometric ErBaCo4O7 + x (x ≈ 0 and 0.03) Cobaltites

Photon Ring Astrometry for Superradiant Clouds

“…An important example of this rich phenomenology occurs when the boson Compton wavelength is comparable to the gravitational radius of a rotating black hole (BH). Then, a dense bound state can be formed via superradiant extraction of the BH rotational energy [11][12][13]. Through this process, a "boson cloud" can form outside the horizon, giving rise to a system also known as a gravitational atom [3,[14][15][16].…”

“…The eigenstates of the boson are characterized by an energy ω ∼ μ [13,14]. When the angular velocity Ω of the BH is larger than the angular phase velocity of the bosons, i.e., ω=m < Ω, where m is the azimuthal number of the boson, then a bound superradiant state is possible, which grows via extraction of rotational energy from the BH [12,13].…”