Nav: Home

Nearly extreme black holes which attempt to regrow hair become bald again

November 15, 2019

The black holes of Einstein's theory of relativity can be completely described by just three parameters: their mass, spin angular momentum, and electric charge. Since two black holes that share these parameters cannot be distinguished, regardless of how they were made, black holes are said to "have no hair": they have no additional attributes that can be used to tell them apart.

In the early 1970s the late Jacob Bekenstein provided a proof for the nonexistence of hair made of scalar fields given a set of assumptions on the properties of the latter. Researcher Lior Burko of Theiss Research said, "Since Bekenstein's proof, several papers found examples for scalar hair, and all these examples violate one or another of the assumptions made by Bekenstein. But in all cases, the hair was made of the scalar field itself."

Recently, it was shown that black holes that are charged by the maximum possible electric charge ("extreme black holes") can have an additional property, permanent hair that is made of a massless scalar field, and that this newly found hair can be observed from a great distance. "A massless scalar hair does not violate any of the assumptions underlying Bekenstein's proof. It was a big surprise for me when this new hair was found by Angelopoulos, Aretakis, and Gajic, so I wanted to look at it in greater detail. It is hair in a different sense than the kinds of hair that were found before. It is not the scalar field itself, but a certain integral on a derivative of the scalar field that is to be calculated on the surface of the black hole, on its event horizon," said Burko. The new hair can be observed at a great distance, by calculating a different quantity there. "The measurement at a great distance that Angelopoulos, Aretakis, and Gajic found is strictly speaking precise only at infinitely late time," added Burko. "These would be observers who are very distant from the black hole, and who make the measurements in the infinite future. We wanted to see what happens at late but finite times, to see the time dependence of the measurement and how it approaches its asymptotic value. Another special thing about this new hair is that it is applies only for exactly extreme black holes, and we wanted to understand what happens when the black hole is nearly extreme, but not exactly extreme."

Burko and his colleagues Gaurav Khanna of the University of Massachusetts Dartmouth and his former student Subir Sabharwal, currently with the Eastamore Group, showed in a paper just published in Physical Review Research that measurements from a great distance are approaching the hair value, with the difference between them decaying with inverse time. But then they went beyond the original model used by Angelopoulos, Aretakis, and Gajic, and generalized the hair to black holes that rotate at the maximum possible spin rate or just close to it. "In addition to a maximal value of charge, there is also a limit for how fast a black hole can spin. Black holes that spin at the maximal allowed rate are therefore also called extreme black holes. We describe both maximally charged and maximally spinning black holes by the name extreme black holes, as there are many similarities between the two. The new hair was originally found for a very useful toy model for black holes, specifically black holes that are spherically symmetric and electrically charged. But black holes in reality are neither. Instead, we wanted to find out if this hair can be found also for spinning black holes," said Burko. "In the movie Interstellar the monster black hole is nearly extreme. We wanted to see if Gargantua has hair."

The team used very intensive numerical simulations to generate their results. The simulations involved using dozens of the highest-end Nvidia graphics-processing-units (GPUs) with over 5,000 cores each, in parallel. "Each of these GPUs can perform as many as 7 trillion calculations per second; however, even with such computational capacity the simulations took many weeks to complete" said Khanna.

The team showed that for the nearly extreme spinning black holes the hair is a transient behavior. At intermediate times nearly extreme black holes behave like extreme black holes would, but at late times they behave like regular, non-extreme black holes. "Nearly extreme black holes can pretend that they are extreme for only so long. But eventually their non-extremality becomes manifest," Burko summarized. "Nearly extreme black holes that attempt to regrow hair will lose it and become bald again." The team also discusses the observational features, e.g., with gravitational waves observatories such as LIGO/VIRGO or LISA, of the smoking-gun detection of nearly extreme black holes.
-end-
The research was partially funded by the National Science Foundation and the Office of Naval Research. Computational resources of UMass Dartmouth's Center for Scientific Computing & Visualization Research (CSCVR) were utilized for the research work. The CSCVR promotes the mission of UMass Dartmouth by providing undergraduate and graduate students with high quality discovery-based educational experiences that transcend the traditional boundaries of academic field or department, and foster collaborative research in the computational sciences within the University and with researchers at other universities, National Labs, and industry. Khanna serves as the Director of the Center.

This open-access paper was published Friday, 11/15/2019 as PHYSICAL REVIEW RESEARCH 1, 033106 (2019), DOI:10.1103/PhysRevResearch.1.033106.

For more information, please contact Lucas Franca, Tel.: (858) 336-5461, Email: l.franca@theissresearch.org

Theiss Research

Related Black Hole Articles:

Black hole team discovers path to razor-sharp black hole images
A team of researchers have published new calculations that predict a striking and intricate substructure within black hole images from extreme gravitational light bending.
Planets around a black hole?
Theoreticians in two different fields defied the common knowledge that planets orbit stars like the Sun.
Black hole mergers: Cooking with gas
Gravitational wave detectors are finding black hole mergers in the universe at the rate of one per week.
Going against the flow around a supermassive black hole
At the center of a galaxy called NGC 1068, a supermassive black hole hides within a thick doughnut-shaped cloud of dust and gas.
Eyeballing a black hole's mass
There are no scales for weighing black holes. Yet astrophysicists from the Moscow Institute of Physics and Technology have devised a new way for indirectly measuring the mass of a black hole, while also confirming its existence.
First 'overtones' heard in the ringing of a black hole
By listening for specific tones in the gravitational waves of black hole mergers, researchers are putting Albert Einstein's theories to new tests.
Black hole holograms
Japanese researchers show how a holographic tabletop experiment can be used to simulate the physics of a black hole.
Where in the universe can you find a black hole nursery?
Gravitational wave researchers at the University of Birmingham have developed a new model that could help astronomers track down the origin of heavy black hole systems in the universe.
Astronomers capture first image of a black hole
The Event Horizon Telescope (EHT) -- a planet-scale array of eight ground-based radio telescopes forged through international collaboration -- was designed to capture images of a black hole.
Hiding black hole found
Astronomers have detected a stealthy black hole from its effects on an interstellar gas cloud.
More Black Hole News and Black Hole Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.