Q about black holes (split from Black Hole Energy Distribution)

[Airbrush]

If a black hole is not feeding, then would inside the event horizon be a total vacuum and all energy contained within the singularity?  A non-feeding black hole would be just a singularity and its' gravity?

[MigL]

A BH is always feeding.
If its temperature is lower than the CMB, it is feeding on that energy plus the virtual particles that give rise to the Hawking radiation mechanism, with the net effect being an uncrease in the mass-energy of the BH, and resultant increase in the area of the event horizon.
If the BH's temperature is higher than the temp of the CMB, then the Hawking radiation will dominate and it is only feeding on that (  Hawking radiation 'feeds' on one half of the virtual particle pair, technically, nothing is emitted from the BH ), and the net effect will be a loss of mass-energy, a constantly smaller area of the event horizon, leading to even higher temperature; IE evaporation of the BH.

There is no such thing as a naked singularity.
Although certain theories ( solutions of the field equations ), at the edge of applicability, predict the singularity 'shedding' its event horizon.
Such as Kerr ( rotating ) BHs at a certain critical spin, and R-N ( charged ) BH's above a critical charge.

[beecee]

2 hours ago, Airbrush said:

If a black hole is not feeding, then would inside the event horizon be a total vacuum and all energy contained within the singularity?  A non-feeding black hole would be just a singularity and its' gravity?

I was just about to answer and say yes to that, then I read MigL's well thought out answer which I see as essentially correct. 

But let me add that in the event Hawking radiation was invalid [I don't believe it is invalid] then essentially any BH not feeding is nothing more then critically curved spacetime,  with a mass at its core in some unknown form. Most cosmologists now don't accept the existence of any singularity with infinite spacetime curvature and density, just a region where our known laws of physics and GR are not evident.

Edited January 31, 2019 by beecee

[mathematic]

We really don't know what goes on inside a black hole.  Quantum theory and General relativity clash.

[Airbrush]

6 hours ago, mathematic said:

We really don't know what goes on inside a black hole.  Quantum theory and General relativity clash.

Yes, we really don't know, but what do you think goes on inside a black hole?

7 hours ago, MigL said:

A BH is always feeding.
If its temperature is lower than the CMB, it is feeding on that energy plus the virtual particles that give rise to the Hawking radiation mechanism, with the net effect being an uncrease in the mass-energy of the BH, and resultant increase in the area of the event horizon.

Very interesting, I had never heard that BH are always feeding on temperature and virtual particles.  Does everyone agree?  How much mass of "food" does that result in?  I thought the only virtual particles the BH eats are those located right next to the event horizon?  It also eats the surrounding temperature difference?  These are miniscule I would guess.

Do you mean "uncrease" or "increase"?  I thought that the Hawking radiation mechanism results in a net effect of evaporating the black hole.  The black hole shrinks in size.

Ok so there are no true "singularities" just states of density greater than the density of a neutron star?

Edited February 1, 2019 by Airbrush

[MigL]

Nothing comes out of a BH.

Virtual particles are a consequence of borrowed mass-energy with a time constraint according to Heisenberg's Uncertainty Principle, and originate outside the event horizon.
If the BH captures one of the pair, the other cannot annihilate with it anymore and must become a real particle and escape. That is the radiation part.
The one that is captured by the BH actually adds mass-energy equivalent to one virtual particle, but once time is up and the 2 particle virtual mass-energy debt must be repaid, the BH has a net loss of one virtual particle equivalent mass-energy. That is the evaporation part.

The temperature of a BH is due to entropy considerations. Large BHs have a very low temperature and radiate at the characteristic wavelength of a black body at that temperature. Very long wavelength, low energy radiation.
Small ( microscopic ) BH shave a very high temperature and radiate at very short wavelengths,  and high energy. They lose more equivalent mass-energy and so evaporate much faster.

There are also what are called 'active' BHs, which feed ravenously. Possibly because they are located in a gas/dust cloud, or are drawing mass from a companion star. These form an accretion disc of infalling plasma, accelerated to relativistic speeds, and the resulting 'cyclotron' radiation is emitted as polar jets. It is thought that in early epochs of the universe, as galaxies were forming, their large central BHs were feeding and growing at massive rates, and their polar jets were what we see as distant ( in time and distance ) quasars.

Edited February 1, 2019 by MigL

[Itoero]

22 hours ago, Airbrush said:

If a black hole is not feeding, then would inside the event horizon be a total vacuum and all energy contained within the singularity?  A non-feeding black hole would be just a singularity and its' gravity?

According to the No-hair theorem Info that enters a black hole doesn't leave 'quantum scars'. According to this theorem the event horizon doesn't alter when the black hole feeds.

Stephen Hawking thought differently. He suggested that black holes might have 'sot hairs' low-energy quantum excitations that release information when the black hole evaporates.

Edited February 1, 2019 by Itoero

[mathematic]

What goes on inside a black hole??  My guess - one big wave function.

[Itoero]

52 minutes ago, mathematic said:

What goes on inside a black hole??  My guess - one big wave function.

Hawking proposed that information is lost in black holes, and not preserved in Hawking radiation. Susskind disagreed, arguing that Hawking's conclusions violated one of the most basic scientific laws of the universe, the conservation of information. As Susskind depicts in his book, "The Black Hole War" was a "genuine scientific controversy" between scientists favoring an emphasis on the principles of relativity against those in favor of quantum mechanics. The debate led to the holographic principle, proposed by Gerard 't Hooft and refined by Susskind, which suggested that the information is in fact preserved, stored on the boundary of a system.https://en.wikipedia.org/wiki/The_Black_Hole_War

Their 'views' on what's inside:

http://www.hawking.org.uk/into-a-black-hole.html

 

[MigL]

To be fair L Susskind has changed his views also.
IIRC originally he favored the hot firewall hypothesis arising from entanglement break between interior  ( to the EH ) and exterior regions of space.
It was only later that he changed his views to the information being encoded in the radiation, thereby preserving the 'monogamous' entanglement.

Keep in mind also, that spatial entanglement and information conservation ( as well as Entropy and Hawking radiation ), as related to Black Holes, are 'hodge-podge' marriages between GR and QM, where their areas of applicability slightly overlap.
Any conclusions we may draw as to wider questions may be overturned by an actual Quantum Gravity theory

[Airbrush]

On ‎1‎/‎31‎/‎2019 at 10:13 PM, MigL said:

Nothing comes out of a BH.

Virtual particles are a consequence of borrowed mass-energy with a time constraint according to Heisenberg's Uncertainty Principle, and originate outside the event horizon.
If the BH captures one of the pair, the other cannot annihilate with it anymore and must become a real particle and escape. That is the radiation part.
The one that is captured by the BH actually adds mass-energy equivalent to one virtual particle, but once time is up and the 2 particle virtual mass-energy debt must be repaid, the BH has a net loss of one virtual particle equivalent mass-energy. That is the evaporation part.

The temperature of a BH is due to entropy considerations. Large BHs have a very low temperature and radiate at the characteristic wavelength of a black body at that temperature. Very long wavelength, low energy radiation.
Small ( microscopic ) BH shave a very high temperature and radiate at very short wavelengths,  and high energy. They lose more equivalent mass-energy and so evaporate much faster.

There are also what are called 'active' BHs, which feed ravenously. Possibly because they are located in a gas/dust cloud, or are drawing mass from a companion star. These form an accretion disc of infalling plasma, accelerated to relativistic speeds, and the resulting 'cyclotron' radiation is emitted as polar jets. It is thought that in early epochs of the universe, as galaxies were forming, their large central BHs were feeding and growing at massive rates, and their polar jets were what we see as distant ( in time and distance ) quasars.

Please help me visualize the interior of a black hole and virtual particles entering it.  What is the mass of a virtual particle?  Given a 3-solar-mass black hole, up to what distance outside the event horizon can one of a virtual pair be captured and the other escape?  In one year, how much mass in the form of virtual particles and heat are added to this black hole?

When you discuss BH temperature, WHERE exactly is that temperature located?  It would seem to me that the region inside the event horizon (above) is very near a vacuum so how can that have any temperature?

Suppose the only matter flowing into the black hole (given above) was virtual particles and surrounding temperature, can both virtual particles of the pair be captured?  Would the pair captured add mass to the black hole or just annihilate?  When such virtual particles, and heat, enter the black hole, they are accelerated to nearly light speed towards the center.  We don't know about true "singularities" so is it safe to say the center of the black hole is very small and very dense, denser than neutron star material?  Could we say the region inside the event horizon is a total vacuum, except for the center region, and except for occasional particles flying near light speed towards the center?

[swansont]

1 hour ago, Airbrush said:

Please help me visualize the interior of a black hole and virtual particles entering it. 

We don’t know anything about this.

1 hour ago, Airbrush said:

 When you discuss BH temperature, WHERE exactly is that temperature located?  It would seem to me that the region inside the event horizon (above) is very near a vacuum so how can that have any temperature?

The only temperature you can know about is the surface. Nothing about the interior.

[beecee]

2 hours ago, Airbrush said:

Please help me visualize the interior of a black hole and virtual particles entering it.  What is the mass of a virtual particle? 

For all intents and purposes, the interior of a BH is simply critical spacetime curvature with a one way path to the center in a finite time, where the mass in an unknown form probably exists. GR tells us that when the Schwarzchild radius is reached, further collapse is compulsory. 

Quote

Given a 3-solar-mass black hole, up to what distance outside the event horizon can one of a virtual pair be captured and the other escape?  In one year, how much mass in the form of virtual particles and heat are added to this black hole?

Virtual particle pairs would need to "pop into existence" just this side of the EH. A photon of light that is emitted directly radially away just this side of the EH, will appear to "hover" there for eternity, never quite getting away but always just escaping the BH's clutches. Assuming Hawking Radiation is valid [I have no reason to doubt that] all BH's will in the course of time evaporate, although that timeline will be the ultimate  timeline of the universe and its probable long cold death freeze scenario.

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When you discuss BH temperature, WHERE exactly is that temperature located?  It would seem to me that the region inside the event horizon (above) is very near a vacuum so how can that have any temperature?

OK, I'm now entering less then certain grounds as far as my limited knowledge and answers goes, but I believe from our FoR, we observe the EH as the source of the escaping virtual particle that has now become real, and as X-rays.

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Suppose the only matter flowing into the black hole (given above) was virtual particles and surrounding temperature, can both virtual particles of the pair be captured?  Would the pair captured add mass to the black hole or just annihilate?

If both virtual pairs fall in then the BH's mass is increased with no sign from our FoR of Hawking Radiation.

 

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When such virtual particles, and heat, enter the black hole, they are accelerated to nearly light speed towards the center.  We don't know about true "singularities" so is it safe to say the center of the black hole is very small and very dense, denser than neutron star material?  Could we say the region inside the event horizon is a total vacuum, except for the center region, and except for occasional particles flying near light speed towards the center?

Yes, the mass would be in an unknown state at or below the quantum/Planck level where GR and the laws of physics fail us.

26 minutes ago, swansont said:

We don’t know anything about this.

Obviously not with any 100% certainty, but we can "visualise" probable events, based on the predictions of GR, and one of the prime predictions of course is that when the Schwarzchild radius is reached, further collapse is compulsory.

OK, upon re-reading my post, I aint happy with my answer thus...."If both virtual pairs fall in then the BH's mass is increased with no sign from our FoR of Hawking Radiation".

 

The following may help with regards to BH temperatures and Hawking Radiation....

https://phys.org/news/2016-09-cold-black-holes.html

extract:

"The temperature of black holes is connected to this whole concept of Hawking Radiation. The idea that over vast periods of time, black holes will generate virtual particles right at the edge of their event horizons. The most common kind of particles are photons, aka light, aka heat.

Normally these virtual particles are able to recombine and disappear in a puff of annihilation as quickly as they appear. But when a pair of these virtual particles appear right at the event horizon, one half of the pair drops into the black hole, while the other is free to escape into the Universe.
 

From your perspective as an outside observer, you see these particles escaping from the black hole. You see photons, and therefore, you can measure the temperature of the black hole.

The temperature of the black hole is inversely proportional to the mass of the black hole and the size of the event horizon. Think of it this way. Imagine the curved surface of a black hole's event horizon. There are many paths that a photon could try to take to get away from the event horizon, and the vast majority of those are paths that take it back down into the black hole's gravity well.

But for a few rare paths, when the photon is traveling perfectly perpendicular to the event horizon, then the photon has a chance to escape. The larger the event horizon, the less paths there are that a photon could take.

Since energy is being released into the Universe at the black hole's event horizon, but energy can neither be created or destroyed, the black hole itself provides the mass that supplies the energy to release these photons."

Read more at: https://phys.org/news/2016-09-cold-black-holes.html#jCp

Edited February 2, 2019 by beecee

[MigL]

If you watch the L Susskind video, he does a pretty good job of describing how material falling into a BH ( as observed from a distant FoR ), adds domain(s) to the surface area of the EH. These domains are a measure of the Entropy of the BH/EH.
Now no-one has ever put a thermometer through an event horizon to measure the temperature, but we know ( from Thermodynamics ) that Entropy is related to temperature by  DeltaS = Q/T.
So we know that a BH /EH must have a temperature even if we can't measure it.

Any virtual particles must annihilate because they exist on 'borrowed' energy.
If they both escape, or they both cross the event horizon, there is no problem re-paying the mass-energy back to the 'universe', and there is NO mass increase to the BH. It is only when the virtual particle pair is separated by an EH that re-payment by annihilation becomes impossible, and we have the strange situation of one virtual particle forced to become real Hawking radiation, and the other effectively becoming 'negative' mass-energy, and causing the BH to lose an equivalent amount of mas-energy.

If two people, one slightly ahead of the other, cross an EH, the one following will not see the first ahead of him.
Neither of them will see anything in front of them, as light, and any information is restricted to travelling only towards the center. This means that, not only can you not see anything ahead of you inside the event horizon, but nothing ahead of you can ever affect you in any way, until you reach the 'edge' of space-time at the ( possible ) singularity.

[beecee]

22 minutes ago, MigL said:

So we know that a BH /EH must have a temperature even if we can't measure it.

Would I be correct in assuming that as we approach the centre of the BH [the gravitational singularity] the entropy and temperature approach 0 degrees K? And at the centre, reaches 0 degrees K totally?

Quote

Any virtual particles must annihilate because they exist on 'borrowed' energy.
If they both escape, or they both cross the event horizon, there is no problem re-paying the mass-energy back to the 'universe', and there is NO mass increase to the BH.

OK, that clears up my own answer of which I expressed uncertainty on...thanks.

[Mordred]

36 minutes ago, MigL said:

 These domains are a measure of the Entropy of the BH/EH.
Now no-one has ever put a thermometer through an event horizon to measure the temperature, but we know ( from Thermodynamics ) that Entropy is related to temperature by  DeltaS = Q/T.
So we know that a BH /EH must have a temperature even if we can't measure it.

 

Back years ago when I first started my studies, I once questioned :how can the (just slightly singularity radius have a temperature if time essentially stops" ? ) the answer was correctly applied, it stops or infinitely redshifts to certain observers. the point being based on the laws of thermodynamics all observers aside we can make the educated guess that after crossing the EH our laws of the universe still applies. An outside observer cannot measure this but an in-falling observer can. One of the primary laws is that higher density equates to higher temperatures. We can plot the graph until the Planck temperature which is of order [latex] 10^32[/latex] which is on similar scale to the point we can equate to the singularity of the BB initial temperature at [latex] 10^{-43}[/latex]. Higher than this temperature our math breaks down into further inconsistencies.

 Its a fairly safe bet that until you hit the actual singularity the laws of physics should be much the same as we now know it but there is no way to confirm this. One has to carefully examine the type of observer when making calculations.

the two key distinctions being an in-falling vs outside observer.

the answer to the last post should consider this key aspect... to the outside observer temperature infinitely redshifts (approaches zero Kelvin) this isn't necessarily true for the in-falling observer.

Hawking radiation is primarily shown using the Schwartzchild metric. The observer in this case is the one at infinity that sees the infinite redshift. (the metric doesn't delve into inside the EH hence its specifications to the surface boundary). now lets think about that a sec.... as an EH gets smaller it gets hotter why ? the answer is based on the above... and one must understand how "Observers" enter the picture. 

An EH is an apparent horizon as different coordinate changes can relocate the EH. Or in the case of the Kerr metric have multiple EH's. 

 

Edited February 2, 2019 by Mordred