Vortex String Formation in Black Hole Superradiance of a Dark Photon with the Higgs Mechanism.

Black hole superradiance, which only relies on gravitational interactions, can provide a powerful probe of the existence of ultralight bosons that are weakly coupled to ordinary matter. However, as a boson cloud grows through superradiance, nonlinear effects from interactions with itself or other fields may become important. As a representative example of this, we use nonlinear evolutions to study black hole superradiance of a vector boson that attains a mass, via a coupling to a complex scalar, through the Higgs mechanism. For the cases considered, we find that the superradiant instability can lead to a transient period where the scalar field reaches its symmetry restoration value, leading to the formation of closed vortex strings, the temporary disruption of the exponential growth of the cloud, and an explosive outburst of energy. After the cloud loses sufficient mass, the superradiant growth resumes, and the cycle repeats. Thus, the black hole will be spun down but, potentially, at a much lower rate compared to when nonlinear effects are unimportant and with the liberated energy going primarily into bosonic radiation instead of gravitational waves.

Dynamics of Spontaneous Black Hole Scalarization and Mergers in Einstein-Scalar-Gauss-Bonnet Gravity.

We study the dynamics of black holes in scalar Einstein-Gauss-Bonnet theories that exhibit spontaneous black hole scalarization using recently introduced methods for solving the full, nonperturbative equations of motion. For one sign of the coupling parameter, nonspinning vacuum black holes are unstable to developing scalar hair, while for the other, instability only sets in for black holes with sufficiently large spin. We study scalarization in both cases, demonstrating that there is a range of parameter space where the theory maintains hyperbolic evolution and for which the instability saturates in a scalarized black hole that is stable without symmetry assumptions. However, this parameter space range is significantly smaller than the range for which stationary scalarized black hole solutions exist. We show how different choices for the subleading behavior of the Gauss-Bonnet coupling affect the dynamics of the instability and the final state, or lack thereof. Finally, we present mergers of binary black holes and demonstrate the imprint of the scalar hair in the gravitational radiation.

Cosmic Censorship Upheld in Spheroidal Collapse of Collisionless Matter.

We study the collapse of spheroidal configurations of collisionless particles in full general relativity. This setup was originally considered by Shapiro and Teukolsky, where it was found that prolate configurations with a sufficiently large semimajor axis gave rise to diverging curvature, but no apparent horizon. This was taken as evidence for the formation of a naked singularity, in violation of cosmic censorship. We revisit such configurations using different coordinates and slicing, and considering a range of values for the semimajor axis and eccentricity of the initial matter distribution, and find that the final state in all cases studied is a black hole plus gravitational radiation. Though initially distorted, the proper circumferences of the apparent horizons that are found do not significantly exceed the hoop conjecture bound. Configurations with a larger semimajor axis can produce strong gravitational radiation, with luminosities up to P_{GW}∼2×10^{-3}c^{5}/G.

Massive Boson Superradiant Instability of Black Holes: Nonlinear Growth, Saturation, and Gravitational Radiation.

We study the superradiant instability of a massive boson around a spinning black hole in full general relativity without assuming spatial symmetries. We focus on the case of a rapidly spinning black hole in the presence of a vector boson with a Compton wavelength comparable to the black hole radius, which is the regime where relativistic effects are maximized. We follow the growth of the boson cloud through superradiance into the nonlinear regime as it spins down the black hole, reaches a maximum energy, and begins to dissipate through the emission of gravitational waves. We find that the superradiant instability can efficiently convert a significant fraction of a black hole's rotational energy into gravitational radiation.

Superradiant Instability and Backreaction of Massive Vector Fields around Kerr Black Holes.

We study the growth and saturation of the superradiant instability of a complex, massive vector (Proca) field as it extracts energy and angular momentum from a spinning black hole, using numerical solutions of the full Einstein-Proca equations. We concentrate on a rapidly spinning black hole (a=0.99) and the dominant m=1 azimuthal mode of the Proca field, with real and imaginary components of the field chosen to yield an axisymmetric stress-energy tensor and, hence, spacetime. We find that in excess of 9% of the black hole's mass can be transferred into the field. In all cases studied, the superradiant instability smoothly saturates when the black hole's horizon frequency decreases to match the frequency of the Proca cloud that spontaneously forms around the black hole.

Spontaneous Decay of Periodic Magnetostatic Equilibria.

In order to understand the conditions that lead to a highly magnetized, relativistic plasma becoming unstable, and in such cases how the plasma evolves, we study a prototypical class of magnetostatic equilibria in which the magnetic field satisfies ∇×B=αB, where α is spatially uniform, on a periodic domain. Using numerical solutions, we show that generic examples of such equilibria are unstable to ideal modes (including incompressible ones), which are marked by exponential growth in the linear phase. We characterize the unstable mode, showing how it can be understood in terms of merging magnetic and current structures, and explicitly demonstrate its instability using the energy principle. Following the nonlinear evolution of these solutions, we find that they rapidly develop regions with relativistic velocities and electric fields of comparable magnitude to the magnetic field, liberating magnetic energy on dynamical time scales and eventually settling into a configuration with the largest allowable wavelength. These properties make such solutions a promising setting for exploring the mechanisms behind extreme cosmic sources of gamma rays.

Ultrarelativistic black hole formation.

We study the head-on collision of fluid particles well within the kinetic energy dominated regime (γ = 8 to 12) by numerically solving the Einstein-hydrodynamic equations. We find that the threshold for black hole formation is lower (by a factor of a few) than simple hoop conjecture estimates, and, moreover, near this threshold two distinct apparent horizons first form postcollision and then merge. We argue that this can be understood in terms of a gravitational focusing effect. The gravitational radiation reaches luminosities of 0.014 c(5)/G, carrying 16 ± 2% of the total energy.

Locally administered ketorolac and bupivacaine for control of postoperative pain in breast augmentation patients: part II. 10-day follow-up.

BACKGROUND: Previously, it was shown that locally applied intraoperative ketorolac and bupivacaine significantly reduced pain in the recovery room. The objective of this study was to test the effectiveness of the same solution over the first 10 days. METHODS: This study was a prospective, randomized, double-blind clinical trial with ethical approval. Fifty submuscular breast augmentation patients were enrolled, and informed consent was obtained. Standard anesthetic and surgical protocols were followed. Either normal saline or ketorolac and bupivacaine (30 mg and 150 mg, respectively) were placed into the pocket. The power of this study to detect a 20 percent difference was 0.90, and values of p < 0.05 were considered significant. The primary outcome was pain measured with the visual analogue pain scale recorded in a take-home diary. The secondary outcome was codeine usage. RESULTS: Forty-five patients completed the study. Of the patients who did not, three were in the normal saline group (n = 22) and two were in the ketorolac-bupivacaine group (n = 23). The ketorolac-bupivacaine combination significantly reduced pain over the first 5 days. By the tenth day postoperatively, the effect had dissipated. These patients also used less codeine. There were no significant complications. CONCLUSION: Locally applied, intraoperative ketorolac and bupivacaine significantly reduced pain for 5 days after surgery in women who had undergone primary breast augmentation.

Locally administered ketorolac and bupivacaine for control of postoperative pain in breast augmentation patients.

With recent developments in the field of analgesia, the question arises whether there is a role for placing local anesthetics, nonsteroidal anti-inflammatory drugs, or both into the breast implant pocket. The objective of this study was to test the effectiveness of locally administered intraoperative ketorolac and bupivacaine with epinephrine at reducing pain in the postoperative period. The study was a prospective, randomized, double-blind clinical trial. One hundred consecutive retropectoral breast augmentation patients were enrolled, and informed consent was obtained. A standard anesthetic protocol and surgical procedure were followed. Normal saline, ketorolac alone (30 mg), bupivacaine alone (150 mg), or ketorolac and bupivacaine (30 mg and 150 mg respectively) were placed into the implant pocket before implant insertion. All patients completed the study. The power of this study to detect a 20 percent difference with respect to the primary outcome was 0.90 and confidence intervals of 95 percent were used to determine significance. The primary outcome was pain as measured by the visual analogue pain scale. The secondary outcome was time spent in the recovery room. Intraoperative placement of ketorolac combined with bupivacaine reduced pain in the postoperative period. It did not appear that anesthesiologist, anesthesia time, surgeon, operating room time, difficulty of dissection, breast incision, or implant size had a significant effect on postoperative pain. There was a trend that the ketorolac and bupivacaine patients spent less time in the recovery room and used fewer analgesics postoperatively than the other patients. There were no hematomas requiring reoperation and no complications. Locally administered intraoperative ketorolac and bupivacaine with epinephrine significantly reduced pain in the postoperative period.