WHITE HOLE

In astrophysics, a 'white hole' is the time reversal of a black hole. While
a black hole acts as an absorber for any matter that crosses the event horizon, a White Hole acts as a source that ejects matter from its event horizon. The sign of the
acceleration is invariant under time reversal, so both black and white holes attract
matter. The only potential difference between them is in the behavior at the horizon.
Hawking argued that white holes are the same as black holes, once quantum mechanics
is taken into account.

Contents

Relation to Quantum Mechanical Black Holes

Origin

Recent developments

See also

References

External links

Relation to Quantum Mechanical Black Holes

Black hole horizons can only absorb matter, while white hole horizons ostensibly recede from
any incoming matter at the local speed of light, so that the infalling matter never crosses.
The infalling matter is then scattered and reemitted at the death of the white hole, receding to infinity after having come very very close to the final singular point where the white
hole is destroyed. The total proper time until an infalling object encounters the singular endpoint is the same as the proper time to be swallowed by a black hole, so the white hole picture does not say what happens to the infalling matter. Ignoring the classically unpredictable emissions of the white hole, the white hole and black hole are indistinguishable for external observers.
In quantum mechanics, the black hole emits Hawking radiation, and so can come to thermal
equilibrium with a gas of radiation. Since a thermal equilbrium state is time reversal
invariant, Hawking argued that the time reverse of a black hole in thermal
equilibrium is again a black hole in thermal equilibrium.^[1] This implies that
black holes and white holes are the same object. The Hawking radiation from an
ordinary black hole is then identified with the white hole emission. Hawking's semi-classical
argument is reproduced in a quantum mechanical AdS/CFT treatment^[2], where a black hole
in Anti De Sitter space is described by a thermal gas in a gauge theory, whose time
reversal is the same as itself.

Origin

White holes appear as part of the vacuum solution to the Einstein field equations describing a Schwarzschild wormhole. One end of this type of wormhole is a black hole, drawing in matter, and the other is a white hole, emitting matter. While this gives the impression that black holes in this universe may connect to white holes elsewhere, this turns out not to be the case for two reasons. First, Schwarzschild wormholes are unstable, disconnecting as soon as they form. Second, Schwarzschild wormholes are only a solution to the Einstein field equations in vacuum (when no matter interacts with the hole). Real black holes are formed by the collapse of stars. When the infalling stellar matter is added to a diagram of a black hole's history, it removes the part of the diagram corresponding to the white hole [1].
The existence of white holes that are not part of a wormhole is doubtful, as they appear to violate the second law of thermodynamics.
Quasars and active galactic nuclei are observed to spew out jets of matter. This is now believed to be the result of polar jets formed when matter falls into supermassive black holes at the centers of these objects. Prior to this model, white holes emitting matter were one possible explanation proposed.

Recent developments

A more recently proposed view of white holes posits consideration to a revision of the standard model of the big bang theory which states that the big bang is an explosion that happens within a black hole, with the expansion that follows the traditional interpretation of the big bang, expanding into infinite space inside the black hole. In other words, a miniature universe is created at the core of the black hole, which expands into extra dimensions outside of this universe. The expansion taking place in this new miniature universe, if it could be perceived from an observer from this universe, could be looked at as a white hole. Matter that could not escape the intense gravitational pull of the black hole in this universe is instead sent speeding into the newly expanding baby universe. Using that logic, one could assume that our universe itself is a white hole. Hypothetically, this model could be used to explain the increasing rate of expansion of the universe: as matter from our parent universe is engulfed by our parent black hole (the black hole that created our universe), our own universe is fed this matter which could possibly have something to do with dark matter and dark energy, which currently is thought to contribute to the increase in the rate of our universe's expansion.¹

See also

★ Black Hole

★ Wormhole

★ White holes in fiction

References

★ Universes inside a Black Hole, , , , Physics Letters B,
1. Universes inside a Black Hole, Hawking, S. W., , , Physical Review D13, 1976
2.

External links

★ Ask an Astronomer: "What is a White Hole?"

★ Schwarzschild Wormholes

★ Schwarzschild Wormhole animation

★ New Theory: Universe Was Born in a Black Hole

★ Shockwave cosmology inside a Black Hole

★ Parallel Universes & Multiple Dimensions

★ Michio Kaku: Mr Parallel Universe