A new solution to the so-called Black Hole Information Paradox has been presented. It involves a peculiar solution of general relativity: wormholes, special bridges between two space-time locations.
This theoretical framework provides intriguing hints at what might really be going on inside black holes.
To understand the exciting implications of this work, presented in the Journal of High Energy Physics, we ought to go back to the 1970s. During that decade, Stephen Hawking discovered that black holes are such extreme objects that their properties can be reduced to just a few numbers – and that those numbers are independent of how the black hole started.
This is a problem – if the conditions after a certain point don’t matter, then a physical state could turn into many and not be unique anymore. That means that information that enters the black hole is lost forever, and this is forbidden by the laws of quantum mechanics.
A solution provided by Hawking himself is that general relativity ought to be corrected and that information is saved by an emission from the black hole known now as Hawking radiation. However, the way it is corrected is a matter of debate.
A key factor that comes into play is entropy, the measure of how disordered a system is. As the black hole emits Hawking radiation, it evaporates and shrinks. But simple combinations of quantum mechanics and relativity have the entropy growing as the black hole shrinks, leading to the loss of at least some information. Thus, we are back in a paradox.
In 1993, Don Page worked out that entropy must first grow but then go to zero to not violate the conservation of information. This new work is a way to get Page’s calculation into a model – and that’s where the wormhole comes in.
Wormholes are special solutions in relativity, although just because the math works it doesn’t mean that they are real.
The team has the same approach, using the math to create a connection from the inside of the black hole to the radiation emitted that looks like a wormhole. They are not implying that black holes are riddled with wormholes, but that the theory that unifies general relativity and quantum mechanics – the fabled quantum gravity – might look like this as it is in agreement with Page’s expectation.
“We discovered a new spacetime geometry with a wormhole-like structure that had been overlooked in conventional computations,” lead author Kanato Goto of the RIKEN Interdisciplinary Theoretical and Mathematical Sciences, said in a statement. “Entropy computed using this new geometry gives a completely different result.”
While the theory is intriguing, the physics of it all continues to baffle. Once something crosses the event horizon of a black hole, it can no longer escape as it would have to move faster than the speed of light. There is something that sits beyond our current understanding at work when it comes to the true solution of the Information Paradox.
“We still don’t know the basic mechanism of how information is carried away by the radiation,” Goto added. “We need a theory of quantum gravity.”