Black hole singularity

  • Thread starter DLuckyE
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  • #26
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Wikipedia said:
The main idea behind the quantum theory of a Big Bounce is that, as density approaches infinity, the behavior of the quantum foam changes. All the so-called fundamental physical constants, including the speed of light in a vacuum, were not so constant during the Big Crunch, especially in the interval stretching 10−43 seconds before and after the point of inflection. (One unit of Planck time is about 10−43 seconds.)

If the fundamental physical constants were determined in a quantum-mechanical manner during the Big Crunch, then their apparently inexplicable values in this universe would not be so surprising, it being understood here that a universe is that which exists between a Big Bang and its Big Crunch.

One of the main problems with the Big Bang theory is that at the moment of the Big Bang, there is a singularity of zero volume and infinite energy. This is normally interpreted as the end of the physics as we know it; in this case, of the theory of General Relativity. This is why one expects quantum effects to become important and avoid the singularity.

However, research in loop quantum cosmology purported to show that a previously existing universe collapsed, not to the point of singularity, but to a point before that where the quantum effects of gravity become so strongly repulsive that the universe rebounds back out, forming a new branch. Throughout this collapse and bounce, the evolution is unitary.

Reference:
http://en.wikipedia.org/wiki/Big_Bounce" [Broken]
http://en.wikipedia.org/wiki/Big_Crunch" [Broken]
http://en.wikipedia.org/wiki/Planck_time" [Broken]
http://en.wikipedia.org/wiki/Loop_quantum_cosmology" [Broken]
 
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  • #27
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Well, sure. Quantum effects are something we don't understand yet.
Is this why people on here say virtual parties are not real? And what about the BH hawking radiation & the casimir effect? Very confused. :(
 
  • #28
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I think the singularities inside the black holes do not exist; nobody proved them anyway.
How the density inside the black hole is higher than Planck density to form a singularity?
The word "singularity" is a mathematical term that means that the function is non-analytic. Generally this comes about due to the fact that some law is applied where it is not defined. An example is the very singularity we are talking about:

g[0,0]=-(1-Rs/r)
where Rs=dthe Schwarzschild radius of the black hole

When r=0, then we are at the singularity: we are dividing by zero. This arises because of two problems. First, division by zero is not defined. Secondly, the metric associated with the exterior coordinates doesn't apply to the interior of the event horizon. We can cure the second case by switching to interior coordinates, but the first case still remains.

The only way out of the dilemma is to realize that something else must happen when r=0 (or its equivalent). Perhaps the very nature of the black hole changes. Perhaps the interior of the black hole is actually a quark-star, or made of bosonic matter. Who knows?
 
  • #29
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Is this why people on here say virtual parties are not real? And what about the BH hawking radiation & the casimir effect? Very confused. :(
Virtual particles are particles that seem to violate Heisenberg's Uncertainty Principle. That is because the distance over which they act is smaller than the wavelength corresponding to their momentum. As a result, they are particles that must exist due to the requirements of conservation laws, but can't be measured to exist.

Hawking radiation results from the fact that particle-antiparticle pairs always spontaneously appear in free space. Near a black hole there is a chance that one particle will fall into the black hole while the other escapes. Since the energy of the system must be conserved, according to Hawking some of the mass of the black hole must be radiated away with the escaping particle.

Casimir force results from the fact that we can associate a wavelength with each component of energy, which presumably consists of photons or photon-like quanta.When two conducting plates are parallel, some waves will fit inside the separation between the plates and others will not. The net result is that inside the separation of the plates will have less energy than the outside. As the plates are brought closer together, they will exhibit a force that arises completely due to this energy difference in the vacuum. Aparently this effect is real and has been observed.
 
  • #30
780
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It is easy to calculate the mass density required to generate an event horizon. The formula is R = 2GM/c^2 where R is the radius, G is the gravitational constant, M is mass and c is the speed of light. Plugging in the mass of the sun, for example [2e30 kilograms], yields a value of 3000 meters as the radius at which its density would be sufficient to generate an event horizon. No singularity required.
And what is goin to force that mass of particles to get so small? Gravity is opposed by degeneracy pressure - first by the electrons and then the nucleons - but pressure is energy per unit volume, which produces gravity too. A runaway into the conditions of a singularity occurs because the particles themselves are pushing too hard in opposition to their own gravity. There's an implied point of no return at which no known force can oppose runaway collapse, but whether that is at neutron star or quark star size no one presently knows. The properties of large balls of naked quarks isn't well constrained by current knowledge.
 
  • #31
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And what is goin to force that mass of particles to get so small?
I'm under the impression that collapse is inevitable once inside 2M because the matter now exists in space-like spacetime (i.e. r is temporal) and regardless of the forces involved, no stable radius is possible and matter will keep collapsing until r=0 or spacetime ceases to exist (which is suppose to be the case at Planck scale) or time-like spacetime is reinstated as in the case of rotating or charged black holes.
 
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  • #32
970
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Any model with a radius less than the Planck radius no longer obeys General Relativity and according to cosmologists, virtual particle turbulent Quantum Foam is encountered, and there is no evidence that Planck scale dimensions are capable of being exceeded without completely replacing General Relativity with Quantum Gravity. Also, the Planck radius is a stable radius.

Also, there may be other degeneracy conditions based upon degenerate quark matter and Quantum Gravity and other conservation laws that may exist inside a black hole to prevent the collapse to Planck and sub-Planck scales.

According to Loop Quantum Cosmology which is based upon Loop Quantum Gravity, all wave packets that reach a classical singularity as 'a crunch', 'bounce off'. The result is a state that oscillates between bouncing off the core singularity as 'a bounce' and rebounding back to the event horizon as 'a bang'. I have included a link to a video and references from Wikipedia that demonstrates this:
"[URL [Broken]
[PLAIN]http://relativity.livingreviews.org/Articles/lrr-2005-11/tn_bouncestill.png [Broken]

Reference:
http://en.wikipedia.org/wiki/Loop_quantum_gravity" [Broken]
http://en.wikipedia.org/wiki/Loop_quantum_cosmology" [Broken]
http://en.wikipedia.org/wiki/Quantum_foam" [Broken]
http://en.wikipedia.org/wiki/Big_Crunch" [Broken]
http://en.wikipedia.org/wiki/Big_Bounce" [Broken]
http://en.wikipedia.org/wiki/Big_Bang" [Broken]
http://en.wikipedia.org/wiki/Oscillatory_universe" [Broken]
http://www.humnet.ucla.edu/humnet/phil/faculty/Smeenk/Bojowald_LQC.pdf"
http://relativity.livingreviews.org/Articles/lrr-2005-11/articlesu50.html" [Broken]
 
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  • #33
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While a radius (or reduced circumference) can be deemed a stable radius for matter that has collapsed to Planck density/pressure, r=0 would still apply to the outer edge of this radius as this would be the end of spacetime (though some kind of bounce would probably stop this occuring, the collapsed matter oscillating close to Planck properties), the volume of matter with Planck density/pressure contained within the radius would be without dimension, as with these properties, the energies that distinguish matter and space are supposed to combine. I'm tempted to say that the Planck matter would be supersymmetric but this would be speculating. It's also fair to say that no matter how little, spin would have some effect on the final collapse of the singularity which may go some way of stopping the matter from reaching absolute Plank properties, and as stated, high energy virtual particles would probably play some part also.

The following paper is a good overview of the different types of singularity-

http://www.unc.edu/~mgood/research/Singularity.pdf [Broken]

The following papers are a bit maths heavy but insightful-

Singularities and Quantum Gravity
Authors: Martin Bojowald
http://arxiv.org/abs/gr-qc/0702144

Loop quantum gravity and black hole singularity
Authors: Leonardo Modesto
http://arxiv.org/abs/hep-th/0701239

On the black hole singularity issue in loop quantum gravity
Authors: A. DeBenedictis
http://arxiv.org/abs/0907.0826

The following isn't in a user friendly format but is also insightful-

Quantum Foam and de Sitter-like universe
Authors: P. A. Zizzi
http://arxiv.org/abs/hep-th/9808180

There's also the matter of the weak singularity at the inner horizon of rotating or charged BH's which if applies may render GR mute before even reaching the centre of the black hole.
 
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  • #34
Chronos
Science Advisor
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We already know GR is mute before the singularity.
 
  • #35
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Why so many physicists for years accepted GR beyond the Planck wall?
 
  • #36
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Why so many physicists for years accepted GR beyond the Planck wall?

Can you cite a paper where GR is used at sub-Planck scales?
 

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