* Astronomy

Blobrana · L

RE: Event horizon

Blobrana · L

Title: Destroying the event horizon of regular black holes
Authors: Zilong Li, Cosimo Bambi

Recently, several authors have studied the possibility of overspinning or overcharging an existing black hole to destroy its event horizon and make the central singularity naked. When all the effects are properly taken into account, any attempt to destroy the black hole seems to be doomed to fail, in agreement with the weak cosmic censorship conjecture. In this letter, we study the possibility of destroying the event horizon of regular black holes. These objects have no central singularity and therefore they are not protected by the cosmic censorship hypothesis. Our results strongly support the conclusion that regular black holes can be destroyed. If we believe that the central singularity in astrophysical black holes is solved by quantum gravity effects, we might have a chance to see the black hole's internal region and observe quantum gravity phenomena. As our finding implies the violation of the black hole's area theorem, the collision of two black holes may release an amount of energy exceeding the Hawking bound, which can be experimentally tested by gravitational wave detectors.

Read more (227kb, PDF)

Blobrana · L

How a new black hole paradox has set the physics world ablaze.

Paradoxes in physics have a way of clarifying key issues. At the heart of this particular puzzle lies a conflict between three fundamental postulates beloved by many physicists. The first, based on the equivalence principle of general relativity, leads to the No Drama scenario: Because Alice is in free fall as she crosses the horizon, and there is no difference between free fall and inertial motion, she shouldn't feel extreme effects of gravity. The second postulate is unitarity, the assumption, in keeping with a fundamental tenet of quantum mechanics, that information that falls into a black hole is not irretrievably lost. Lastly, there is what might be best described as "normality," namely, that physics works as expected far away from a black hole even if it breaks down at some point within the black hole - either at the singularity or at the event horizon.
Read more

Ed ~ The size of the singularity may encompass the entire blackhole

Blobrana · L

Peering to the Edge of a Black Hole

Using a continent-spanning telescope, an international team of astronomers has peered to the edge of a black hole at the center of a distant galaxy. For the first time, they have measured the black hole's "point of no return" - the closest distance that matter can approach before being irretrievably pulled into the black hole.
A black hole is a region in space where the pull of gravity is so strong that nothing, not even light, can escape. Its boundary is known as the event horizon.
Read more

Blobrana · L

Title: A signature for the absence of event horizons
Authors: J. Barbieri, G. Chapline

A sharp dip in the spectrum of gamma rays coming from compact objects below 70 MeV would be an unambiguous signal that compact astrophysical objects have a physical surface, and there is no event horizon. Observation of this effect would open a window for the empirical study of Planck scale physics

Read more (717kb, PDF)