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The Big Bang ( possible ) singularity is in the past, while the Black Hole ( possible ) singularity is in the future.
Huge difference.

Temperature is easiest to understand by considering a gas. The more energetically the gas particles bump against each other, the higher the temperature.
Past a Black Hole's event horizon there is no 'compression'. Everything is moving in one direction. Nothing can move away from the ( possible ) singularity. Nothing can even slow down. So how can anything bump into anything else to give rise to a compression or temperature ?
Anything that crosses an event horizon encounters nothing ( nichts, nada, niente, rien, etc. ) on its way to its future encounter with the possible singularity. The interior of the event horizon is really 'empty' space. I'm not even sure if you can model virtual particles in there ( Mordred ?? ).

The only 'temperature' of a Black Hole is derived from the entropy ( area ) of its event horizon.
 

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22 minutes ago, MigL said:

. I'm not even sure if you can model virtual particles in there ( Mordred ?? ).

The only 'temperature' of a Black Hole is derived from the entropy ( area ) of its event horizon.
 

I've never come across any model that does. Though keep in mind some metrics can reflect changes to the boundary of the EH which is specifically an apparent singularity and not a true singularity.

https://en.m.wikipedia.org/wiki/Eddington–Finkelstein_coordinates

A true singularity breaks down regardless of whatever choice of metric you apply such as the singularity condition at the theoretical centre of the BH.

Edited by Mordred

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6 hours ago, MigL said:

Nothing can even slow down. So how can anything bump into anything else to give rise to a compression or temperature ?
Anything that crosses an event horizon encounters nothing ( nichts, nada, niente, rien, etc. ) on its way to its future encounter with the possible singularity. The interior of the event horizon is really 'empty' space. I'm not even sure if you can model virtual particles in there ( Mordred ?? ).

Galaxies are thought to have black holes at their centre. The centre of a stationery disc has a location and if you travel towards it you will reach it. The same is for a rotating disc except you are fighting against centripetal force. If everything is travelling at light speed towards the centre on arrival it will splat or smear over the surface adding to the mass.

Are you saying that inside a black hole contrary to all the normal pop science I read mass has not been shrunk down to the size of a walnut, it just vanishes and does not cause further compression of said walnut down to the plank length. If something enters a black hole and is accelerated by gravity to its centre, to increase the mass of the black hole but never reaches the singularity, are you effectively saying space is expanding inside the black hole. 

All things are quantum fluctuations and or excitations. They are the cause of gravity, without quantum fluctuations and or excitations there is no gravity, no forces nada, didly squat. 

Dark energy is thought by some to be caused by quantum fluctuations in space, gravity could also be caused by the absorption of quantum fluctuations by mass, ie a unidirectional flow towards mass. Could an absence of quantum fluctuations/virtual particles represent a black hole singularity. 

Further Mordred posted this earlier under quantum entanglement "

Let us look at a Feyman diagram which is a representation in and unto itself specifically thee amplitudes of particle reactions.

e+eγuu+

Not pretty but close enough. The inbound legs on the diagonal arrows is the particles we typically define as real ie not virtual. Same as the outbound diagonal lines. In th actual diagrams the lines are all connected."

Inside a black hole could the Feynman diagram give some insight. Could particles on collision with their anti particle or singularity not convert to radiation, but convert to a virtual particle and vanish.

 

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Um What did I previously describe mass as being defined as? to the first portion.

As to the Feyman diagram, particle decays must folllow numerous conservation laws otherwise they won't decay...

Conservation of lepton, charge, flavor, isospin, energy/momentum, color, partity etc. When matter and antimatter collide the energy from the collision will always give rise to new particles.

Anyways usually these other conservation laws are not very well known unless one studies particle physics. 

Edited by Mordred

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Anyways BH's are highly complex objects. The event horizon itself adds to the complexity. For example a Kerr Rotating BH has more than one event horizon. Each event horizon has two surfaces with boundary conditions and subsequently its own thickness if you will..

So each EH under treatments can literally represent trapped surfaces depending on observer and coordinate choices.

All motion is timelike within any of these boundaries so infalling matter switches roles between travelling to space to travelling through time which of course is an artifact of coordinate and observer choice. From the reference frame of the infalling body time runs normally. 

One can argue that infalling matter never reaches the centre from certain coordinate choices, yet counter argue that from the reference frame of the infalling body once you cross the initial Schwartzchild surface you will see two boundaries. One from our universe and an EH due to the interior of the singularity.

To make matters worse some of these event horizons are apparent while others are true.

Some of this is described via the Penrose diagrams as the Schwartzchild metric is only suitable for the non rotating case. The Kerr metric itself also leads to artifacts of the metric. The Findle Kruskal coordinates themselves don't address all the issues and it can be argued that neither does the Penrose diagrams. 

I haven't even mentioned the issues involved in causality connections from interior to exterior, there are arguments either way.

lol there was a paper roughlyv10 years back that showed that GR can be valid at greater than c if all observers are greater than c. The problem is that time reverses. They still run into the issue when v=c.

Edited by Mordred

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Interesting paper Mordred.
Very readable, even for a layman, as it has plenty of verbal explanations for any mathematics.

It should be pinned ( if it could ) as it would rid a lot of the misconceptions about BH theory.

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15 hours ago, Mordred said:

Excellent link, thank you very much.

With reference to things never reaching the centre of a black hole, what happens when two black holes merge, do they ever form a single singularity or core inside the new event horizon . 

I will go away and study the link, and google your other posts, before asking any more stupid questions.

 

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13 minutes ago, geordief said:

Can I post this question in this thread.?Is there a limit to the size a Black Hole can be?

I don't think there is any theoretical upper limit. On the other hand, it isn't known how the really big ones in the centres of galaxies get to be that big.

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Just now, Strange said:

I don't think there is any theoretical upper limit. On the other hand, it isn't known how the really big ones in the centres of galaxies get to be that big.

If they can increase without limit does that provide a mechanism to  prevent a singularity at the centre? Can  the density get "spread out" with increasing size?

 

Can all the matter in the universe be combined into one BH  under any circumstances?

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Just now, geordief said:

If they can increase without limit does that provide a mechanism to  prevent a singularity at the centre? Can  the density get "spread out" with increasing size?

However large they are, all the matter falls towards the centre (according to GR).

The average density (the mass of the black hole divided by the volume enclosed by the event horizon) of the black hole decreases with increasing size and mass. For large black holes, this can be less than water. But, as far as I know, this has no physical meaning.

4 minutes ago, geordief said:

Can all the matter in the universe be combined into one BH  under any circumstances?

Nothing I can imagine. I suppose that, in the very far distant future, it is possible that all the galaxies in a cluster could collide so their black holes merge and then absorb all the material from those galaxies. But as galaxy clusters move apart, it seems impossible that everything could be absorbed in one BH.

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1 minute ago, Strange said:

However large they are, all the matter falls towards the centre (according to GR).

The average density (the mass of the black hole divided by the volume enclosed by the event horizon) of the black hole decreases with increasing size and mass. For large black holes, this can be less than water. But, as far as I know, this has no physical meaning.

Nothing I can imagine. I suppose that, in the very far distant future, it is possible that all the galaxies in a cluster could collide so their black holes merge and then absorb all the material from those galaxies. But as galaxy clusters move apart, it seems impossible that everything could be absorbed in one BH.

If the expansion which seems irreversible now was in fact to reverse itself at some stage  (some unknown property of dark matter or dark energy or some other as yet unknown force) then we could end up with one aggregate BH?

 

As density increased  at the centre of that BH  (or even  a smaller  one) might  some limit be passed that would trigger a change in behaviour   and allow  matter to escape?

 

(If there were extra dimensions could they escape that way?)

 

Might  an event like that be very similar to what may have occurred  prior to the Big Bang?

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7 minutes ago, geordief said:

If the expansion which seems irreversible now was in fact to reverse itself at some stage  (some unknown property of dark matter or dark energy or some other as yet unknown force) then we could end up with one aggregate BH?

Possibly, I guess.

7 minutes ago, geordief said:

As density increased  at the centre of that BH  (or even  a smaller  one) might  some limit be passed that would trigger a change in behaviour   and allow  matter to escape?

Not from what we know at the moment. Although rotating black holes do appear to have a path through the singularity to another space (whether that is somewhere else in this universe or another universe, isn't known). Some people think this would form a white hole - but we have no evidence for such things. Others suggest it could form a new universe (https://www.insidescience.org/news/every-black-hole-contains-new-universe).

 

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3 minutes ago, Strange said:

Possibly, I guess.

Not from what we know at the moment. Although rotating black holes do appear to have a path through the singularity to another space (whether that is somewhere else in this universe or another universe, isn't known). Some people think this would form a white hole - but we have no evidence for such things. Others suggest it could form a new universe (https://www.insidescience.org/news/every-black-hole-contains-new-universe).

 

Thanks. I'll have a look at that.

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On 12/10/2017 at 6:04 PM, Mordred said:

Ok Dokey thanks for the link, the most interesting thing was the ring singularity at the centre of spinning black holes. Since galaxies spin I assume this ring singularity applies to all Black holes at the centre of all spinning galaxies. Other than that there was little speculation ref what goes on inside the event horizon, which is interesting. The maths for me was a trip down memory lane, a few 2nd order differential equations combined with some light trig, as MIGL said not too difficult.

I am guessing no one has speculations ref two event horizons converging, and whether their singularities would ever converge.

But thanks all for the input.

If any one wants to ask questions on any thread I have started please do. Dont be shy, shy kids get nowt. 

 

 

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I have really managed to confuse myself, by looking at anti de sitter space in black holes.  

De Sitter, Minkowski and Anti De Sitter I grasped, then things started going down hill.

Space is not just x,y,z,t space time with 4 coordinates. It has at least 4 spacial dimensions in some weird incomprehensible membrane or surface, that expands and wraps around everything, including all quantum fluctuations and excitations.  

Is there a idiots guide to anti de sitter space inside a black hole. I have found lots of very technical/philosophical papers full of jargon and barely comprehensible maths. Just how many dimensions can de sitter space have. I wound up with 10 space time dimensions, before my head exploded. Does it also apply to particles as well at the quantum level and the universe as a whole. 

ref the two singularities and event horizons merging I read that the singularities would merge along with their event horizons which has been observed. There seems to multiple ideas ref what is inside a black hole 

 

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 You must have been reading an ADS/CFT correspondance paper. Yeah it will make your head explode if you don't understand what is meant by dimensions under math ( independent variables).

Unfortunately there is no real idiots guide to properly explain it. 

Edited by Mordred

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11 hours ago, Mordred said:

 You must have been reading an ADS/CFT correspondance paper. Yeah it will make your head explode if you don't understand what is meant by dimensions under math ( independent variables).

Unfortunately there is no real idiots guide to properly explain it. 

Apologies for the question. I was reading several papers at once, and was being distracted by a mixture of string theory quantum theory and relativity whilst looking at similarities. Having taken a walk after asking the question, and slept I answered the question myself, I think!. Thanks for coming back. A question remains in my head on how many spacial dimensions could there be, I will keep reading until I form an opinion.

I was as you are aware trying to get a glimpse of what might lie beyond the event horizon of a black hole. I was getting a lot of conflicting answers re what I was looking at, which disagree with some of what has been written by others on this thread. I was struck by the similarity of black hole structure using space time, fundamental particles and quantum BH which sent me down a different line of thought on particle physics etc etc.

Clearly I need to focus on the small things first.

Quantum BH's are I understand only theoretical and about as small as they can get, does anyone have any insight into these and Quantum excitations, or interactions with quantum fluctuations? My view is a Quantum BH would be devoid of Quantum fluctuations is this correct? On the larger scale a BH having a theoretical singularity caused by quantum excitations would also be devoid of quantum fluctuations approaching the singularity, is this completely wrong? 

In string theory Quantum excitations are represented by oscillating strings. Do the oscillations speed up under higher gravity conditions?  Does the relative speed of a fermion, closed string affect its frequency? ie can a particle be blue or red shifted inside a black hole? 

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black hole merger noddies guide:D

It is interesting that all things being quantum fluctuations or excitations, that 3 solar masses of energy are given off at the merger in the form of ONE or MULTIPLE gravitational waves. I had previously thought that as the black hole event horizons merged gravity increased, and then was released with A gravitational wave radiating outwards containing the equivalent of 3 solar masses of energy. 

Other than the obvious Hawking radiation and gravitational energy escaping a black hole, nothing else gets out. 

Gravitational waves are on the large scale are fluctuations in space time, on the small scale they are quantum fluctuations travelling through space as a wave. Does this mean 3 solar masses were converted inside the black hole to Quantum fluctuations which were ejected as a wave into space? Does this further mean that mass is possible being decomposed into radiation quantum excitations and then down to just quantum fluctuations in space inside the black hole. Ie did the black hole decompose the 3 solar masses of matter/energy inside the BH's into Quantum fluctuations forming a gravitational wave?

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38 minutes ago, interested said:

Does this mean 3 solar masses were converted inside the black hole to Quantum fluctuations which were ejected as a wave into space?

No. The gravitational waves originate in the space-time between the orbiting black holes. (There is then a smaller post-merger oscillation as the event horizon settles down to a sphere again - the ringdown phase.)

This is an entirely classical theory so any mention of quantum fluctuations is stuff you have made up. 

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21 minutes ago, Strange said:

This is an entirely classical theory so any mention of quantum fluctuations is stuff you have made up. 

If all things are quantum fluctuations and or excitations (QFT) they cause the stressing of space time and the effect seen in classical theory as gravitational waves.  

Dark energy as you know could be due to quantum fluctuations in space, which could equally be described by Einsteins original equations according to this group of mathematicians https://phys.org/news/2017-12-dark-energy-mathematicians-alternative-explanation.html?utm_source=nwletter&utm_medium=email&utm_campaign=daily-nwletter

QFT and Relativity should if they are both correct be getting the same answers and both should apply. They are just different ways of looking at the same thing, as is string theory. I will grant you one theory may be more suitable or be a better fit to a problem at different scales or levels of complexity. However they all overlap and should be giving approximately the same answer. Obviously Relativity displaced Newtons ideas, but Newtons ideas are still applicable in almost all mechanical applications as you are aware. 

I make very little up. However I do read a lot, think and gather ideas, which I then ask questions about. Unless Mordred has been misleading me, all things are quantum fluctuations and or excitations, this includes gravity, or the stressing of space time. The theoretical graviton is a spin 2 boson and it is a quantum excitation is it not?   

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Phase transitions took place during the big bang, is it likely these are reversed inside a black hole due to pressure and temperature?

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  Interested you really must be careful where you apply fluctuations and excitations. There are numerous phenomena described by physics where these terms are not applicable.

For example in this thread the Chandreskar limit or the Black holes rotation isn't an excitation or fluctuation so it is incorrect to state everything is.

 The problem is you tend to take those terms out of context when examining different theories and models. They apply well to QM and QFT but one of the main reasons is these are schotastic treatments that include probability in their examination. Though not in every instance. You need to be careful to understand when those terms can be appropriately applied.

If your describing something that has no wavefunctions those terms are not applicable.

Now dark energy, if I examine a quantum space example DE under phase space which is extremely localized this is appropriate but if I examine a global space where these fluctuations are essentially washed out via a different examination ie the FRW metric itself and the difference in size scale under examination where DE is constant these terms are not appropriate.

Even under QFT and QM certain mathematical terms has no wavefunction example a manifold. It may be comprised of excitations but the manifold itself doesn't have a wavefunction.

10 hours ago, interested said:

Phase transitions took place during the big bang, is it likely these are reversed inside a black hole due to pressure and temperature?

Its questionable whether or not some of those phase transitions are reversible under compression as opposed to expansion. A large part of the reason being availability of the correct particle species during the transition stages.

 The process of nucleosynthesis coupled with inflation isn't nearly the same as compression. So the sequence of nucleosynthesis may not be reversible as you won't have the supercooling then reheating phase transitions via compression. That in and of itself will alter the applicable phase transitions

Edited by Mordred
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