It has long been known that a maximally spinning black hole cannot be overspun by tossing in a test body. Here we show that if instead the black hole starts out with below maximal spin, then indeed overspinning can be achieved. We find that requirements on the size and internal structure of the test body can be met if the body carries in orbital but not spin angular momentum. Our analysis neglects radiative and self-force effects, which may prevent the overspinning.
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http://dx.doi.org/10.1103/PhysRevLett.103.141101 | DOI Listing |
Phys Rev Lett
December 2024
International Centre for Theoretical Sciences, Tata Institute of Fundamental Research, Bangalore 560089, India.
We consider an analytically tractable model that exhibits the main features of the Page curve characterizing the evolution of entanglement entropy during evaporation of a black hole. Our model is a gas of noninteracting fermions on a lattice that is released from a box into the vacuum. More precisely, our Hamiltonian is a tight-binding model with a defect at the junction between the filled box and the vacuum.
View Article and Find Full Text PDFPhys Rev Lett
December 2024
Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China.
As a key science project of the Square Kilometre Array (SKA), the discovery and timing observations of radio pulsars in the Galactic Center would provide high-precision measurements of the spacetime around the supermassive black hole, Sagittarius A* (Sgr A*), and initiate novel tests of general relativity. The spin of Sgr A* could be measured with a relative error of ≲1% by timing one pulsar with timing precision that is achievable for the SKA. However, the real measurements depend on the discovery of a pulsar in a very compact orbit, P_{b}≲0.
View Article and Find Full Text PDFNature
December 2024
NRC Herzberg, Victoria British Columbia, Canada.
Recent observations have found a large number of supermassive black holes already in place in the first few hundred million years after the Big Bang, many of which seem to be overmassive relative to their host galaxy stellar mass when compared with local relation. Several different models have been proposed to explain these findings, ranging from heavy seeds to light seeds experiencing bursts of high accretion rate. Yet, current datasets are unable to differentiate between these various scenarios.
View Article and Find Full Text PDFNat Commun
December 2024
Astronomical Institute, Czech Academy of Sciences, Boční II 1401, Prague, 141 00, Czech Republic.
High-velocity stars and peculiar G objects orbit the central supermassive black hole (SMBH) Sagittarius A* (Sgr A*). Together, the G objects and high-velocity stars constitute the S cluster. In contrast with theoretical predictions, no binary system near Sgr A* has been identified.
View Article and Find Full Text PDFPaediatr Child Health
November 2024
Department of Pediatrics and Child Health, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada.
Objectives: Waitlist times for adolescents to be seen for initial assessment for gender-affirming hormone therapy in Manitoba, Canada are often 2 years. The purpose of this study was to understand the experiences of waitlisted youth and to assess the impact of social work contact for accessing relevant resources.
Methods: A qualitative, semi-structured interview study was conducted.
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