Week 3: Fine-Tuning Analysis Metrics and Literature Review

This week I was debugging the Bayesian inference and reading more recent papers. There are two detector streams: the Hanford detector in Washington (H1) and the Livingston detector in Louisiana (L1). I changed the detector stream to L1 and shortened the ringdown window, and after that the power spectral density (PSD) weighted fast Fourier transform (FFT – which converts time to frequency) peak moved to about 250 Hz, which is much closer to the expected Kerr ringdown frequency for GW150914. Since the rest of the code could not run due to a temporary firewall, I moved to the theory side of the project.

I looked at islands and wormholes. An island is a region near or inside the black hole that must be included when calculating the entropy of Hawking radiation in these papers. Replica wormholes are additional geometries that emerge in the computation of replica entropy. In these calculations, the radiation entropy can follow a page curve, which means it goes up and reaches a peak, and then stops going up. That resulting shape is consistent with the unitary evolution (indicates that information does not disappear).

In “Replica Wormholes and Entanglement Islands in the Karch-Randall Braneworld,” Hao Geng studies a holographic Karch-Randall braneworld with a bath designed to collect radiation. He shows how the island contribution becomes important at late times, resulting in a Page curve.

In “Entanglement Island and Page Curve of Hawking Radiation in Rotating Kerr Black Holes,” Liqiang Wang and Ran Li apply the island framework to rotating Kerr black holes within a small-spin approximation. They still obtain a Page curve and demonstrate how rotation affects the Page time and the scrambling time.

In “Ringing out General Relativity: Quasinormal Mode Frequencies for Black Holes of Any Spin in Modified Gravity,” Adrian Chung and Nicolás Yunes developed METRICS, which is a spectral method for determining the frequencies and damping times of ringdown modes in spinning black holes under modified gravity. This paper shows that slow-spin approximations may fail when the black hole spin is not negligible, so any subsequent comparison between an extracted ringdown frequency and the Kerr-predicted frequency and damping time should use values computed for the correct remnant mass and spin.

Next week I’ll be visiting an aircraft maintenance engineering company. I’m looking forward to that.