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Spacetime singularities are problematic in quantum gravity. String theory offers a way to construct such a quantum gravity.

Do strings offer a solution to this problem in the sense that point-like particles are absent? Matter can't accumulate to a point which entails the singularity. Or will even strings contract to point-like structure?

Gerald
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    Does this answer your question? What does string theory predict for the singularity inside a black hole? – John Rennie Jul 19 '22 at 08:39
  • @JohnRennie Partly. I don't see why an horizon doesn't form, as all matter can be contained within a very small volume. – Gerald Jul 19 '22 at 16:01
  • Hi Gerald, see What keeps strings in their proper "shape" despite their enormous inherent tension?. The string cannot contract to a point due to the Heisenberg uncertainty principle. – John Rennie Jul 19 '22 at 16:13
  • @JohnRennie Yes, I understand. But if a huge number of them are contained inside a volume smaller than the accompanying Schwarzschild radius, why wouldn't that give rise to an horizon? – Gerald Jul 19 '22 at 16:36
  • @safesphere I think it depends which coordinates you use. A spherical distribution of mass will partially collapse to a point after which the rest will approach the horizon asymptotically. That is, as seen from afar. But if you fall in with the spherical gas, all particles will accumulate, towards a point, no matter how much they are torn apart by tidal forces. "In fact, one can give definitions to get both answers: a point and a 3-vomume" – Gerald Jul 20 '22 at 08:21
  • @safesphere The last quotation is from the second answer. Why will particles in a spherical distribution collapse to a line shape? – Gerald Jul 20 '22 at 17:00
  • @safesphere the particles accelerate away from each other due to tidal forces, and if particles are points will never touch, but what if the collapsing mass is a 2D spherical shell? – Gerald Jul 20 '22 at 17:07
  • @safesphere I think the singularity is litterally a hole in space. Why should a spherical 2d shell end up on a line? If the shell is 3d it will end up in a volume. Maybe a timelike line? – Gerald Jul 21 '22 at 23:57
  • @safesphere See also https://physics.stackexchange.com/questions/144447/is-a-black-hole-singularity-a-single-point – Gerald Jul 22 '22 at 00:12
  • @safesphere Hi! I can see where your argument goes. Okay, let's see. Let's consider a spherical 2D shell of particles as boundary condition. Seen from the outside they fall towards the center which is still there before the formation of the hole. When the shell reaches the Schwarzschild radius the radial spacecomponent becomes timelike. What was time becomes space. The angular components stay the same. So where does the shell end up? What does it mean the interior has become timelike? What does interior even mean. So, the 2D shell shrinks, time runs normal everywhere. And then, when SR... – Gerald Jul 24 '22 at 22:25
  • @safesphere ...is reached? The inside isappears to become what? Clocks? And the clock becomes the radial space? Where does the radial inside go? And what about the sight from a falling frame? Won't all particles meet? – Gerald Jul 24 '22 at 22:28

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