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Michael C.
Michael C.
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The fuzzballsfuzzball proposal intrigues me, but I doubt its ability to match up with semi-classical low energy physics. A variation of my question was asked by the awkwardly titled post:"At the instant of fuzzball creation, do all strings instantly pop to its face?". And an answer was provided with a link to an article by Samir D. Mathur called "Spacetime has a ‘thickness’",    arXiv:1705.06407 There, Mathur tries to reconcile fuzzballs with the scenario of a shell of matter falling through the smooth horizon of a black hole, where GR tells us nothing special happens.

While the article was relavent, I don't think it answered the original question about black hole creation. Mathur's article already assumes a horizon exists and examines the fate of matter falling towards it. I want to reformulate the question in a way that emphasizes the tension between fuzzballs and low energy physics.

Imagine you're in a spaceship floating in the center of an enormous spherical, homogenous cloud of a very clold, diffuse gas. The total mass of the cloud is about ~$3.9*10^9$ solar masses, and its initially radius is ~$1000 AU$, giving it a density of about ~$0.5 \frac{g}{m^3}$. Slowly, the cloud condenses around you. It eventually reaches a radius of ~$76 AU$, and a density of ~$1.25 \frac{kg}{m^3}$, or the average density of air on Earth.

Despite this mild density of ~$1.25 \frac{kg}{m^3}$, the cloud has collapsed into a black hole. Calculating the Schwarzschild radius

$$ R = \frac{2 G (3.9*10^9 M_☉)}{c^2} ≈ 76 AU$$

At the center of the cloud, you remain oblivious of your future demise, because the local physics around you is mild, and it will remain so for a while. But eventually the density will increase exponentially, and you'll get shredded by the singularity.

That's what would happen according to GR. But according to the fuzzball proposal, there is no interior to the black hole. There's only an extreme configuration of strings and D-branes at the location that is usually called the event horizon, and there's nothing beyond that.

But how would fuzzballs explain the scenario described above? According to GR, at the moment of the formation of the black hole, the local physics around an observer at the center of the gas cloud is simple low energy effective physics, it's table top stuff. But according to the fuzzballs proposal, the moment the cloud reaches the Schwarzschild radius then the entire interior instantly becomes a high energy mess of strings and D-branes that removes the interior from existence.

How does fuzzball proposal reconcile this?

The fuzzballs proposal intrigues me, but I doubt its ability to match up with semi-classical low energy physics. A variation of my question was asked by the awkwardly titled post:"At the instant of fuzzball creation, do all strings instantly pop to its face?". And an answer was provided with a link to an article by Samir D. Mathur called "Spacetime has a ‘thickness’",  arXiv:1705.06407 There, Mathur tries to reconcile fuzzballs with the scenario of a shell of matter falling through the smooth horizon of a black hole, where GR tells us nothing special happens.

While the article was relavent, I don't think it answered the original question about black hole creation. Mathur's article already assumes a horizon exists and examines the fate of matter falling towards it. I want to reformulate the question in a way that emphasizes the tension between fuzzballs and low energy physics.

Imagine you're in a spaceship floating in the center of an enormous spherical, homogenous cloud of a very clold, diffuse gas. The total mass of the cloud is about ~$3.9*10^9$ solar masses, and its initially radius is ~$1000 AU$, giving it a density of about ~$0.5 \frac{g}{m^3}$. Slowly, the cloud condenses around you. It eventually reaches a radius of ~$76 AU$, and a density of ~$1.25 \frac{kg}{m^3}$, or the average density of air on Earth.

Despite this mild density of ~$1.25 \frac{kg}{m^3}$, the cloud has collapsed into a black hole. Calculating the Schwarzschild radius

$$ R = \frac{2 G (3.9*10^9 M_☉)}{c^2} ≈ 76 AU$$

At the center of the cloud, you remain oblivious of your future demise, because the local physics around you is mild, and it will remain so for a while. But eventually the density will increase exponentially, and you'll get shredded by the singularity.

That's what would happen according to GR. But according to the fuzzball proposal, there is no interior to the black hole. There's only an extreme configuration of strings and D-branes at the location that is usually called the event horizon, and there's nothing beyond that.

But how would fuzzballs explain the scenario described above? According to GR, at the moment of the formation of the black hole, the local physics around an observer at the center of the gas cloud is simple low energy effective physics, it's table top stuff. But according to the fuzzballs proposal, the moment the cloud reaches the Schwarzschild radius then the entire interior instantly becomes a high energy mess of strings and D-branes that removes the interior from existence.

How does fuzzball proposal reconcile this?

The fuzzball proposal intrigues me, but I doubt its ability to match up with semi-classical low energy physics. A variation of my question was asked by the awkwardly titled post:"At the instant of fuzzball creation, do all strings instantly pop to its face?". And an answer was provided with a link to an article by Samir D. Mathur called "Spacetime has a ‘thickness’",   arXiv:1705.06407 There, Mathur tries to reconcile fuzzballs with the scenario of a shell of matter falling through the smooth horizon of a black hole, where GR tells us nothing special happens.

While the article was relavent, I don't think it answered the original question about black hole creation. Mathur's article already assumes a horizon exists and examines the fate of matter falling towards it. I want to reformulate the question in a way that emphasizes the tension between fuzzballs and low energy physics.

Imagine you're in a spaceship floating in the center of an enormous spherical, homogenous cloud of a very clold, diffuse gas. The total mass of the cloud is about ~$3.9*10^9$ solar masses, and its initially radius is ~$1000 AU$, giving it a density of about ~$0.5 \frac{g}{m^3}$. Slowly, the cloud condenses around you. It eventually reaches a radius of ~$76 AU$, and a density of ~$1.25 \frac{kg}{m^3}$, or the average density of air on Earth.

Despite this mild density of ~$1.25 \frac{kg}{m^3}$, the cloud has collapsed into a black hole. Calculating the Schwarzschild radius

$$ R = \frac{2 G (3.9*10^9 M_☉)}{c^2} ≈ 76 AU$$

At the center of the cloud, you remain oblivious of your future demise, because the local physics around you is mild, and it will remain so for a while. But eventually the density will increase exponentially, and you'll get shredded by the singularity.

That's what would happen according to GR. But according to the fuzzball proposal, there is no interior to the black hole. There's only an extreme configuration of strings and D-branes at the location that is usually called the event horizon, and there's nothing beyond that.

But how would fuzzballs explain the scenario described above? According to GR, at the moment of the formation of the black hole, the local physics around an observer at the center of the gas cloud is simple low energy effective physics, it's table top stuff. But according to the fuzzballs proposal, the moment the cloud reaches the Schwarzschild radius then the entire interior instantly becomes a high energy mess of strings and D-branes that removes the interior from existence.

How does fuzzball proposal reconcile this?

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Michael C.
Michael C.
  • 125
  • 9

Problems with fuzzball black hole creation and low energy physics

The fuzzballs proposal intrigues me, but I doubt its ability to match up with semi-classical low energy physics. A variation of my question was asked by the awkwardly titled post:"At the instant of fuzzball creation, do all strings instantly pop to its face?". And an answer was provided with a link to an article by Samir D. Mathur called "Spacetime has a ‘thickness’", arXiv:1705.06407 There, Mathur tries to reconcile fuzzballs with the scenario of a shell of matter falling through the smooth horizon of a black hole, where GR tells us nothing special happens.

While the article was relavent, I don't think it answered the original question about black hole creation. Mathur's article already assumes a horizon exists and examines the fate of matter falling towards it. I want to reformulate the question in a way that emphasizes the tension between fuzzballs and low energy physics.

Imagine you're in a spaceship floating in the center of an enormous spherical, homogenous cloud of a very clold, diffuse gas. The total mass of the cloud is about ~$3.9*10^9$ solar masses, and its initially radius is ~$1000 AU$, giving it a density of about ~$0.5 \frac{g}{m^3}$. Slowly, the cloud condenses around you. It eventually reaches a radius of ~$76 AU$, and a density of ~$1.25 \frac{kg}{m^3}$, or the average density of air on Earth.

Despite this mild density of ~$1.25 \frac{kg}{m^3}$, the cloud has collapsed into a black hole. Calculating the Schwarzschild radius

$$ R = \frac{2 G (3.9*10^9 M_☉)}{c^2} ≈ 76 AU$$

At the center of the cloud, you remain oblivious of your future demise, because the local physics around you is mild, and it will remain so for a while. But eventually the density will increase exponentially, and you'll get shredded by the singularity.

That's what would happen according to GR. But according to the fuzzball proposal, there is no interior to the black hole. There's only an extreme configuration of strings and D-branes at the location that is usually called the event horizon, and there's nothing beyond that.

But how would fuzzballs explain the scenario described above? According to GR, at the moment of the formation of the black hole, the local physics around an observer at the center of the gas cloud is simple low energy effective physics, it's table top stuff. But according to the fuzzballs proposal, the moment the cloud reaches the Schwarzschild radius then the entire interior instantly becomes a high energy mess of strings and D-branes that removes the interior from existence.

How does fuzzball proposal reconcile this?