RECENT ARTICLES

A radical theory replaces the cosmic crunchers with fuzzy quantum spheres, potentially solving the black-hole information paradox and explaining away the Big Bang and the origin of time.

Why physics and astronomy communities must take diversity issues seriously in order to do good science.

Einstein’s relativity pushes physicists towards a picture of the universe as a block, in which the past, present, and future all exist on the same footing; but maybe that shift in thinking has gone too far.

Resolving the black hole firewall paradox—by calculating what a real astronaut would compute at the black hole's edge.

Defining a ‘quantum clock’ and a 'quantum ruler' could help those attempting to unify physics—and solve the mystery of vanishing time.

FQXI ARTICLE

May 24, 2018

Fuzzballs v Black Holes

A radical theory replaces the cosmic crunchers with fuzzy quantum spheres, potentially solving the black-hole information paradox and explaining away the Big Bang and the origin of time.

FQXi Awardees: Samir Mathur

May 11, 2018

Samir Mathur

Ohio State University

Under the current paradigm, the core of a black hole is a tantalising mystery, where an incredibly dense, infinitesimally small, and poorly understood "singularity" is believed to lurk. Our universe is also thought to have burst forth from such a singularity, some 13.8 billion years ago, although it’s not clear how. Physicists have struggled to explain exactly what happens inside a singularity for decades. Both quantum effects, which play an important role in the behaviour of tiny objects, and gravity, which governs the motion of immensely heavy things, should be at play. However, attempts to combine the two theories into a model of "quantum gravity" have so far failed and new physics to describe what is happening is desperately needed.

If the core of a black hole isn’t confusing enough, things get worse when you consider its surface—or "event horizon"—which marks an imaginary boundary surrounding the black hole. Anything that crosses the event horizon, even light, will be sucked in towards the black hole’s core and crushed into the singularity. At first it was thought that nothing that falls in to a black hole can ever escape. But in 1974, Stephen Hawking calculated that, thanks to quantum effects, black holes can slowly radiate energy from their horizon. As they do so, they gradually shrink, until eventually they will evaporate entirely. The trouble is, if they vanish from the universe, so too does all the information about the objects that they swallowed over their lifetimes. This, Hawking realized, would violate a fundamental rule of quantum theory, which states that information can never be completely destroyed. He had hit upon the now famous, and still unresolved, black-hole information paradox.

A Fuzzball Compared to a Conventional Black Hole

Fuzzballs (left) contain a tangle of quantum matter and energy throughout,

while matter is concentrated in the core of a conventional black hole (right),

with a featureless event horizon at its surface.

Credit: Fuzzball image courtesy of Samir Mathur

The idea behind fuzzballs goes back to 1997, when Mathur was working as an assistant professor at MIT. He was considering the scales at which quantum gravity acts using string theory—a theoretical framework that makes gravity more compatible with quantum theory, and describes elementary particles as one-dimensional strings that can join onto one another to form new particles.

The ability to form new types of particles is particularly helpful if you are dealing with something as exotic as a black hole. Mathur noted that a black hole must be made of not just one or two particles, but a billion particles colliding. Remarkably, his calculations revealed that when these particles come together, the resulting object does not have a smooth surface, but a fluffy, textured one. By contrast, conventional black holes are thought to be featureless at the horizon. Hence, Mathur coined the name "fuzzball." Unlike mysterious singularities, where conventional physics appears to breakdown, the goings-on within fuzzballs can be understood using string theory. Mathur’s formulation also seems to match well with physical reality; his early calculations show that fuzzball sizes always corresponded to the exact size of the black hole event horizons, computed using Einstein’s theory of gravity, which depend on their mass.

Astronauts and Fuzzballs

But what about the other major problem with black holes, the information paradox? To solve this, Mathur imagined the fate of an astronaut falling on to a fuzzball, rather than a conventional black hole. In the traditional view, the astronaut is pulled to the heart of the black hole, where she and all information about her are crushed into the singularity. But in the fuzzball picture, Mathur conjectured, information about the astronaut is absorbed into the fuzzball in the form of vibrations. The fuzzball perfectly encodes her information content and motion. "Even though the astronaut has actually been broken up into the fuzzball vibrations, you can reassemble those vibrations in a certain way to make her think that she’s still smoothly moving through the horizon into the interior of the black hole," says Mathur.

Cosmic Ripples

Could gravitational waves reveal whether fuzzballs are real?

Credit: LIGO Caltech/MIT

Although still a contentious idea, the fuzzball paradigm has gained a prominent platform at international conferences, and fans say that it has the potential to have a remarkable impact on physics long-term. "If the fuzzball proposal is true, it would revolutionize quantum gravity and the way we think about black holes and spacetime in general," says string theorist Iosif Bena, of the IPHT, in France. Ironically, Bena had set out to prove fuzzballs wrong, a dozen years ago, but after conducting a series of consistency checks, he became convinced that the idea has real merit.

Likewise, Nicholas Warner, a string theorist at the University of Southern California, originally set out to kick fuzzballs into the metaphorical long grass, hoping to show that you couldn’t solve the problem in the black hole context using current mathematical techniques. "I ended up proving the exact opposite," says Warner. "It turned out to be much simpler than I ever had a right to believe, so I moved from being a sceptic to a convert."

By providing a mechanism for structure at the horizon of a black hole, says Warner, there’s even a faint possibility of an observational test that could distinguish between traditional black holes and fuzzballs. When black holes collide, they produce ripples in spacetime, or gravitational waves, such as those recently detected by LIGO. These ripples could be subtly different for fuzzballs compared to conventional black holes. Although, Warner notes, LIGO may not be sensitive enough to pick up fuzzball signatures, this is something to watch out for in the future.

Softening the Big Bang

Recently, Mathur has been applying his fuzzball picture to an even more challenging frontier in physics: the Big Bang. With the help of two FQXi grants, totalling over $100,000, and working with Ali Musomi at Tufts University, in Medford, Massachusetts, he has applied the fuzzball calculations in reverse. This enables him to track the universe backwards in time to its birth from a small object. No one knows what initiated the Big Bang, but the general view is that it started from some sort of singularity, which marks the origin of both space and time. Out of this singularity, spacetime exploded into existence. But the fuzzball paradigm paints a different picture.

If the fuzzball

proposal is

true, it would

revolutionize

quantum gravity.

proposal is

true, it would

revolutionize

quantum gravity.

- Iosif Bena

So, does this mean that time didn’t originate at the Big Bang? Rather, mini fuzzballs have always existed—and what we interpret as the beginning of time at the Big Bang explosion is just the result of their collision? "This is indeed a deep question," says Mathur. Their preliminary studies suggest that we should be thinking of the Big Bang as a softer sort of process, where smaller fuzzballs coalesce into larger ones to ultimately make the universe we see today.

Applying the fuzzball picture to the Big Bang is extremely ambitious, according to Warner. He "jibbers" to think of the complexity of the calculations Mathur and Musomi are undertaking: this requires hundreds of pages of meticulous algebra in string theory. But, if anyone can do it, Mathur can, says Warner: "Mathur is a remarkable guy, probably one of the deepest thinkers around and most respected in the field."

Comment on this Article

Please read the important Introduction that governs your participation in this community. Inappropriate language will not be tolerated and posts containing such language will be deleted. Otherwise, this is a free speech Forum and all are welcome!

function ValidatePostText_main () {
form = document.addPostForm_main;
var recaptcha = $("#g-recaptcha-response").val();
if (recaptcha === "") {
event.preventDefault();
alert("The reCaptcha Box below must be checked before you submit the form");
}
else if (form.postText_main.value == '') {
alert ("The post contains no text");
return false;
}
else {
return true;
}
}

**Your name:**
(optional)

Recent Comments

read all article comments

Please read the important Introduction that governs your participation in this community. Inappropriate language will not be tolerated and posts containing such language will be deleted. Otherwise, this is a free speech Forum and all are welcome!

Please enter the text of your post, then click the "Submit New Post" button below. You may also optionally add file attachments below before submitting your edits.

HTML tags are not permitted in posts, and will automatically be stripped out. Links to other web sites are permitted. For instructions on how to add links, please read the link help page.

You may use superscript (10

^{100}) and subscript (A_{2}) using [sup]...[/sup] and [sub]...[/sub] tags.You may use bold (

**important**) and italics (*emphasize*) using [b]...[/b] and [i]...[/i] tags.You may also include LateX equations into your post.

Insert LaTeX Equation
[hide]

LaTeX equations may be displayed in FQXi Forum posts by including them within [equation]...[/equation] tags. You may type your equation directly into your post, or use the LaTeX Equation Preview feature below to see how your equation will render (this is recommended).

For more help on LaTeX, please see the LaTeX Project Home Page.

LaTeX Equation Preview

preview equation

clear equation

insert equation into post at cursor

LaTeX equations may be displayed in FQXi Forum posts by including them within [equation]...[/equation] tags. You may type your equation directly into your post, or use the LaTeX Equation Preview feature below to see how your equation will render (this is recommended).

For more help on LaTeX, please see the LaTeX Project Home Page.

LaTeX Equation Preview

preview equation

clear equation

insert equation into post at cursor

Attachments
[hide]

You may optionally attach up to two documents to your post. To add an attachment, use the following feature to browse your computer and select the file to attach. The maximum file size for attachments is 1MB.

Once you're done adding file attachments, click the "Submit New Post" button to add your post.

You may optionally attach up to two documents to your post. To add an attachment, use the following feature to browse your computer and select the file to attach. The maximum file size for attachments is 1MB.

Once you're done adding file attachments, click the "Submit New Post" button to add your post.

JIM H wrote on May 13, 2018

A new version of the classic circularity: "nothing happened for a long time, then something happened, and time began."

A new version of the classic circularity: "nothing happened for a long time, then something happened, and time began."

JOE FISHER wrote on May 12, 2018

Dear FQXi.org Article Readers.

Irrefutable evidence exists that conclusively proves that the earth had a visible surface for millions of regular Gregorian calendar years BEFORE Newton and Einstein ever appeared on that surface and began their unrealistic physics FINITE informational guesswork, and before any timepieces were ever manufactured, and well before quantum physics were ever even thought of.

All of the Popes who have ever lived and all of the theoretical physicists that...

Dear FQXi.org Article Readers.

Irrefutable evidence exists that conclusively proves that the earth had a visible surface for millions of regular Gregorian calendar years BEFORE Newton and Einstein ever appeared on that surface and began their unrealistic physics FINITE informational guesswork, and before any timepieces were ever manufactured, and well before quantum physics were ever even thought of.

All of the Popes who have ever lived and all of the theoretical physicists that...

ROBERT H MCEACHERN wrote on May 12, 2018

The blackhole information paradox is based upon several dubious assumptions:

(1) That quantum theory describes everything that exists, rather than merely describing the detection process itself, and thus only the things being detected.

(2) That the information content of an emitter, like a blackhole, is indicative of the information content of the emissions emanating from the emitter. This is generally not true in the classical realm, and there is no reason to suppose it is true in...

The blackhole information paradox is based upon several dubious assumptions:

(1) That quantum theory describes everything that exists, rather than merely describing the detection process itself, and thus only the things being detected.

(2) That the information content of an emitter, like a blackhole, is indicative of the information content of the emissions emanating from the emitter. This is generally not true in the classical realm, and there is no reason to suppose it is true in...

read all article comments