Spacetime surgery for black hole fireworks

We construct an explicit model for the black hole to white hole transition (known as the black hole fireworks scenario) using the cut-and-paste technique. We model a black hole collapse using the evolution of a time-like shell in the background of the loop quantum gravity inspired metric. We then use the space-like shell analysis to construct the firework geometry. Our simple and well defined analysis removes some subtle issues that were present in the previous literature. In particular, we demonstrate that the null energy condition must be violated for the bounce. We also calculate the proper time scales required for the black to white hole transition, which in any valid scenario must be shorter than the evaporation time scale. In contrast, we show that the bouncing time for the distant observer can be chosen arbitrarily, since it is determined by how one cuts and pastes the spacetimes outside the event horizon, and thus does not have any obvious connection to quantum gravity effects.Comment: 16 pages, 8 figure

Tako-tsubo cardiomyopathy after a quarrel.

Objective: To report a case of Tako-tsubo cardiomyopathy in a blind woman.Case presentation: We report a confirmed case of Tako-tsubo cardiomyopathy in a 55-year-old blind woman with past medical history of ocular trauma. The patient suffered from sudden chest pain after a quarrel. Transthoracic echocardiogram (TTE) showed regional wall motion abnormalities. Coronary angiogram showed no significant coronary stenosis, but ventriculogram demonstrated apical ballooning akinesis and hypercontraction in the basal segments. The follow-up TTE revealed a recovery of systolic function 6 weeks later.Conclusion: We report a case of Tako-tsubo cardiomyopathy after a quarrel, implicating that severe emotional or physical stress could trigger myocardial stunning.Keywords: Tako-tsubo cardiomyopathy, ocular trauma, blindness, postmenopaus

First-principles calculations of phase transition, low elastic modulus, and superconductivity for zirconium

The elasticity, dynamic properties, and superconductivity of $\alpha$, $\omega$, and $\beta$ Zr are investigated by using first-principles methods. Our calculated elastic constants, elastic moduli, and Debye temperatures of $\alpha$ and $\omega$ phases are in excellent agreement with experiments. Electron-phonon coupling constant $\lambda$ and electronic density of states at the Fermi level $N$(\emph{E}$_{\rm{F}}$) are found to increase with pressure for these two hexagonal structures. For cubic $\beta$ phase, the critical pressure for mechanical stability is predicted to be 3.13 GPa and at \emph{P}=4 GPa the low elastic modulus ($E$=31.97 GPa) can be obtained. Besides, the critical pressure for dynamic stability of $\beta$ phase is achieved by phonon dispersion calculations to be $\mathtt{\sim}$26 GPa. Over this pressure, $\lambda$ and $N$(\emph{E}$_{\rm{F}}$) of $\beta$ phase decrease upon further compression. Our calculations show that the large value of superconducting transition temperature \emph{T}_{\rm{c}} at 30 GPa for $\beta$ Zr is mainly due to the TA1 soft mode. Under further compression, the soft vibrational mode will gradually fade away.Comment: 15 pages, 5 figure