If no singularity, what’s inside a big black hole?

Bernie G

"The motion of a particle close to a star depends on the absorbed information and there are many different motions." I'm not evaluating particles close to the star or from the event horizon to the surface of the star; orbital mechanics are important there. I'm saying motion is random below the surface of a non-rotating star.

Bernie G

At a talk someone said they thought the pressure would be slightly higher than (rho)(c^2)/3 in a quark/radiation mixture ...... maybe because the quark component can generate a pressure higher than (rho)(c^2)/3.

czes

According to Rueda, inertial mass is not intrinsic to a body at all. It is extrinsic, bestowed on a body from outside. Specifically, it arises from the interaction between the basic building blocks of matter and the great roiling ferment of virtual particles that make up the quantum vacuum .
http://www.calphysics.org/articles/gravity_arxiv.pdf
http://www.hologram1.glt.pl/

Therefore there isn't a random motion but the motion (oscillation) is due to absorbed information which is hidden in the superposition and contained in the vacuum.

Bernie G

Whatever theory you use for motion, when a non-rotating neutron star collapses it makes no sense to think that all particles start orbital motion, so using equations of orbital motion tell us little of whats going on in the collapsed star. Orbital motion does not determine the pressure in the collapsed star.

czes

You are rigt. Therefore the most fundamental is an exchange of the information. The particle oscillates and moves because it absorbs and emits the information from and into an environment. If it absorbs more than emits it accelerates. It is Unruh-Davies effect.
http://en.wikipedia.org/wiki/Unruh_effect

The orbiting motion is an effect if the amount of the absorbed and emitted information is balanced but it isn't always as you see it inside a star. It is more complicated there because all particles are in motion and there is not a simple gradient of the density of the information. A particle is carrying many information and if it is in a relation with an another particle in the vicinity it overcomes the quantity of the information from the gravitational field of the distant particles. You observe the brownian motion then but it is always the exchange of the information as well.

marcus

In a certain sense this thread is kind of funny because very early on one of the top researchers in non-singular BH pointed out to us what is one of the most interesting recent answers to Jim's question ("what's inside") and nobody in the thread picked up on it!It still may be a surprise! In that listing 3 of the top 10 are by Leonardo Modesto, and
if you take a larger sample it is 5 of the top 20. His are numbers 1, 3, 5, 11, 19 in citation ranking.
Recently Leonardo has co-authored about self-dual BH with Sabine Hossenfelder of NORDITA in Stockholm and with Bernard Carr of Queen Mary U. London. Modesto and Premont-Schwarz are at Perimeter.

And Leonardo showed up early on in the thread and pointed these papers out to us.

What brought my attention finally to Loop self-dual BH was not the high rate of citation (which I somehow had not registered) but seeing something similar going on in Asymptotic Safety gravity---papers by Cai and Easson where you also get very long lifetimes of primordial BH and can make a testable hypothesis that they constitute Dark Matter.

It's interesting that researchers coming from both directions find that (totally reversing Hawking) tiny BH have very long lives rather than very brief ones, and that both Loop and Safe gravity researchers propose DM to be clouds of tiny BH.

Both research lines converge on finding tiny BH to be very cold instead of very hot (as Hawking would have it.) Good stuff.

phasl001

So, to my understanding from what I have read (considering all possible theories), a Blackhole "appears" to be a super dense ball of compressed matter where gravity is beyond our comprehension and so strong that light/time cannot escape (Imagine: Our galaxy squeezed and compressed to a size as small as an atom). What is inside a blackhole? Nothing, in theory, matter doesn't exist and its appropriate to say the laws of physics do not apply inside this phenomenon (and therefore doesn't exist?), but outside the event horizon it still holds the laws in tact. These are just my thoughts, as I am not a scientist of any sort, just an average Joe Schmoe interested and curious of the unknown.

jimgraber

Hi Marcus,
Thanks for the post. I will try to read some of those papers and post a slightly informed response in a week or two. I have noticed several papers that suggest black holes should have a discrete spectrum, rather than a continuous or thermal one. But this primarily applies to small black holes, not big ones. And it only indirectly tells you what is inside the black hole, big or small. But I will read some of these papers and see what I learn. Thanks again for the informative and helpful response. Jim Graber

marcus

Hi Jim, good thread! I did not see your post when I was typing this and meant it as a response to the guy just before:
Here's how I read the question: If no singularity, what’s inside a big black hole?

He's asking what, in quantum gravity, takes the place of the classical GR singularity?
What actually is there where (in old classical GR) the "singularity" mistake used to be?

We assume the known laws of physics hold as usual inside the event horizon, except in one very tiny region in the center. A singularity is a place where a theory breaks down so it does not apply and we need an improved theory to describe what goes on. That is what QG is about.

So to get a handle on it the obvious thing to do is to read QG papers that deal with black holes. Particularly ones that get rid of the singularity, and hopefully are testable as well (that's hard but has to be done.)

Here's a good overview introductory paragraph from a 2009 paper. Google "hossenfelder non-singular collapse" and you get http://arxiv.org/abs/0912.1823
It gives a quantum gravity model for "non-singular black hole collapse and evaporation"
This is a model of stuff collapsing to form a black hole, but something else besides a singularity down in the heart of it, and it turns out that the model is testable to some extent by looking for certain kinds of radiation which BHs like this would make (if the model is right.)

Here's a short quote from the introduction that explains the motivation and philosophy behind the research:

From the perspective of quantum gravity, black holes are of interest because of the infinite curvature towards their center which signals a breakdown of General Relativity. It is an area where effects of quantum gravity are strong, and it is generally expected that these effects prevent the formation of the singularity. Since the black hole emits particles in the process of Hawking radiation [1], the horizon radius decreases. In the standard case it approaches the singularity until both, the singularity and the horizon, vanish in the endpoint of evaporation [2]. However, if the singularity does not exist, this scenario cannot be correct. Since the singularity plays a central role for the causal space-time diagram, its absence in the presence of quantum gravitational effects has consequences for the entire global structure [3], and the removal of the singularity is essential for resolving the black hole information loss problem [4]. To understand the dynamics of the gravitational and matter fields, it is then necessary to have a concrete model.

It is thus promising that it has been shown in a simplified version of loop quantum gravity, known as loop quantum cosmology (LQC) [5], a resolution of singularities, the big bang as well as the black hole singularity [6–8], can be achieved. The regular static black hole metric was recently derived in [9], and studied more closely in [10]...

czes

If I understand physics, the problem of the singularity appears in General Relativity because of the continuous space-time.
In Quantum Gravity the problem disappears because the space (vacuum) is discrete.
Therefore the main problem is to find the structure of the space:
1. Continuous space and singularity.
2. Discrete space without singularity:
- 2.1. Physical polarized space changing polarization of the photon.
- 2.2. Non-material (holographic) Information Space conserving original photon.

marcus

I like the term "non-material information space"! You do not need the word "holographic", I think, because there are various ways to present the information.

For example, in Loop you do not even need a "holographic screen". A spin network represents information and is completely non-material.

jimgraber

The old orthodoxy: There’s a singularity in there.
The new orthodoxy: There’s no singularity, but there is a Planck scale wormhole, which acts almost like a singularity FAPP.
It’s interesting that ST and LQG come to almost exactly the same conclusion.
More later.

czes

Yes. Holographic is too specific. There was a time of the fascination.

MTd2

So, quantum gravity is becoming Sartre now?

marcus

Geometry = information. Relational. I think some Greeks already knew this. Not what it "is" but how it responds to measurement.

What interests me especially:

Hoping to see more about this.

tom.stoer

not like a singularity, but like the smooth geometry far away from the "would-be-singularity" and outside the event horizon is the same.

marcus

Yes, that is what I understood Jim to mean when he said "which acts almost like a singularity FAPP."

FAPP is abbr. "for all practical purposes." so same geometry away from the wormhole or whatever--the would-be singularity as you say.

I think the interesting differences come when you consider small holes evaporating. Or not evaporating entirely. Or doing so more slowly than Hawking's picture allows.

Intuitively for large BH it seems to make no difference whether the singularity is resolved and replaced by something else, or not.