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Douglas Stanford probes the chaos inside black holes

His black hole discovery could pave the way to a new theory of quantum gravity

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8:26am, September 26, 2018
Douglas Stanford

CHAOS REIGNS  Physicist Douglas Stanford’s research revealed that black holes are extremely chaotic, thanks to quantum mechanics.

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Douglas Stanford, 31
Theoretical physics
Institute for Advanced Study and Stanford University

Douglas Stanford’s fascination with black holes had its origins in an unlikely place: a sailboat.

Starting at age 10, Stanford spent five years sailing around the world with his parents and two sisters. Sailboats are “like a physics laboratory,” Stanford says. Keeping the boat on course requires balancing the forces induced by wind and water. “You can see really simple physics effects happening,” he says.

Today, Stanford, 31, applies his physics know-how to more abstract problems: Black holes, quantum mechanics and chaos.

His work as a theoretical physicist at the Institute for Advanced Study in Princeton, N.J., has already revealed new insights, including the discovery that black holes reach the pinnacle of chaos — nothing can be more chaotic than a black hole. That revelation reinforces the notion that black holes are some of the most extreme oddities in the universe and, importantly, it might aid the search for a new and improved theory of gravity.

In chaotic systems, a tiny tweak can have cascading effects that drastically alter the outcome. The most famous example is the butterfly effect, a hypothetical scenario in which a butterfly flaps its wings, and the tiny change in airflow affects when and where a tornado appears (SN Online: 9/16/13).

On a quantum level, Stanford and theoretical physicist Stephen Shenker showed in calculations that black holes exhibit similarly chaotic behavior. Changes to a black hole — as minor as throwing a single particle into the abyss — can drastically shift how the black hole behaves.

One key to understanding this chaos is that black holes aren’t fully black. The cosmic giants radiate a faint haze of particles, the result of pairs of quantum particles that are constantly blipping in and out of existence everywhere in space (SN: 11/26/16, p. 28). When this process occurs near a black hole’s edge, some of the particles can escape, producing what’s known as Hawking radiation (SN: 4/14/18, p. 12).

Studying this Hawking radiation reveals black holes’ chaotic nature, Stanford and Shenker, of Stanford University, reported in 2014 in the Journal of High Energy Physics.

Imagine throwing a single electron into a black hole — a tiny change for the behemoth. “It’s one particle and a huge, ginormous black hole,” Stanford says. But that minuscule change alters the Hawking radiation the black hole emits, like a butterfly flapping its wings and redirecting a distant sailboat.

Trapped inside

Imagine a black hole with a particle nearby, in danger of falling in (1). Sometime later, that particle may escape. But if another particle is tossed in (2), the black hole will expand, preventing the original particle from getting away. Making a minor change to the black hole changes the outcome — an indicator of chaos.

Adding a particle increases the black hole’s heft and slightly expands its event horizon, the boundary from within which nothing can escape (SN: 5/31/14, p. 16). Hawking radiation that would otherwise have been emitted gets stuck inside the expanding black hole. A seemingly insignificant alteration has ballooning effects — the definition of chaos.

Stanford then took this idea a step further. In 2016 in the Journal of High Energy Physics, he, Shenker and Juan Maldacena of the Institute for Advanced Study showed theoretically that the repercussions of a small tweak to a black hole snowballed as fast as physically possible. That snowballing makes black holes the most chaotic system allowed by the laws of nature.

Stanford’s colleagues say he’s poised to uncover even bigger insights. “He is a deep thinker and a powerful calculator, a rare, winning combination that one finds in the very best physicists,” says theoretical physicist Raphael Bousso of the University of California, Berkeley. Despite his young age, Stanford has secured a position as an associate professor at Stanford University, where he will move in April.

Maldacena says working with Stanford made him feel like a student again. “He corrected my mistakes and gave me good ideas.” That’s no small feat. Maldacena is a giant of quantum gravity and string theory known for discovering mathematical oddities that physicists are still pondering (SN: 10/17/15, p. 28).

By understanding the link between tiny particles and gigantic black holes, Stanford and others hope to tackle a knotty conflict between two of physics’ most important theories. The aim is to formulate a theory of quantum gravity, combining two theories that have long clashed, quantum mechanics and general relativity. The mismatch hints that something big is deeply wrong at the heart of physics. Stanford’s new ideas about black holes could help scientists find a solution.

“It’s possible that he is one of those rare individuals [who] will really change the direction of science,” Shenker says. “I look forward to seeing whether I’m right.”

Citations

J. Maldacena, S.H. Shenker and D. Stanford. A bound on chaos. Journal of High Energy Physics. Vol. 2016, August 17, 2016, p. 106. doi: 10.1007/JHEP08(2016)106.

S.H. Shenker and D. Stanford. Black holes and the butterfly effect. Journal of High Energy Physics. Vol. 2014, March 13, 2014, p. 67. doi: 10.1007/JHEP03(2014)067.

Further Reading

E. Conover. How physicists will remember Stephen Hawking. Science News. Vol. 193, April 14, 2018, p. 12.

E. Conover. Superfluid helium behaves like black holes. Science News. Vol. 191, April 15, 2017, p. 11.

T. Siegfried. A new ‘Einstein’ equation suggests wormholes hold key to quantum gravity. Science News Online, August 17, 2016.

A. Grant. Entanglement: Gravity's long-distance connection. Science News. Vol. 188, October 17, 2015, p. 28.

T. Siegfried. Holography entangles quantum physics with gravity. Science News Online, September 8, 2014.

A. Grant. The mysterious boundary. Science News. Vol. 185 May 31, 2014, p. 16.

T. Siegfried. Born half a century ago, chaos theory languished for years. Science News Online, September 16, 2013.

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