Neutron Star to Black Hole

Just on the subject of angular momentum of BH's.....
I found the following......contributed by professor Pankaj S. Joshi

http://www.researchgate.net/publica...n_over-spinning_body_be_in_general_relativity
Physical Review D (Impact Factor: 4.86). 06/2014; 90(12):124079. DOI: 10.1103/PhysRevD.90.124079
Source: arXiv
ABSTRACT :
Abstract The angular momentum of the Kerr singularity should not be larger than a threshold value so that it is enclosed by an event horizon: The Kerr singularity with the angular momentum exceeding the threshold value is naked. This fact suggests that if the cosmic censorship exists in our universe, an over-spinning body without releasing its angular momentum cannot collapse to spacetime singularities. A simple kinematical estimate of two particles approaching each other supports this expectation and suggest the existence of a minimum size of an over-spinning body. But this does not imply that the geometry near the naked singularity cannot appear. By analyzing initial data, i.e., a snapshot of a spinning body, we see that an over-spinning body may produce a geometry close to the Kerr naked singularity around itself at least as a transient configuration. PACS numbers: 04.20.-q, 04.20.Cv, 04.20.Dw, 04.20.Ex, 04.25.D- ∗Electronic address: knakao@sci.osaka-cu.ac.jp †Electronic address: M.Kimura@damtp.cam.ac.uk ‡Electronic address: harada@rikkyo.ac.jp §Electronic address: mandar@iucaa.ernet.in ¶Electronic address: psj@tifr.res.in 1

 

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Thanks for linking that paper. Probably pretty interesting for me.

 

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Quite Interesting most certainly for all that have followed this thread, especially for anyone who was claiming that professor Joshi was saying mass/singularities DONT SPIN.
A quick and painless death to that stupid interpretation I must say.

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Paddoboy and Brucep seem to have taken this singularity business well into their hearts !! Chill guys, no professor or physicist or mathematician has ever assigned any spin to singularity.

Dr Joshi has worked on the cosmic censorship and naked singularities (without the shroud of Event Horizon), and his efforts are to demonstrate some geometry associated with naked singularity. Kerr singularity spinning is a term loosely used for spinning Kerr BH and does not convey that singularity per say is spinning.......You guys need to publish your own paper to make singularity spin....like Paddoboy has to publish his own paper to associate singularity with Planck's level (whatever that means).

 

Perhaps its you who needs to "chill out" and start reading relevant posts.
Let me remind you again, "No professor, and no one else except you has said the mass/singularity in a Kerr BH does not spin.
All that's been insinuated is that we are unable to "legally" assign any spin to it due to break down of models.
And considering that your original claim is that nothing spins within the Kerr metric to allow for frame dragging, its still you who must see the light and learn some BH cosmology.
Or perhaps you are going to write a scientific paper for peer review, stating where all the professors and mainstream are wrong in their accepted ideas. [nudge, nudge, wink, wink]

Well since the online evidence says you are the one that was going to write a scientific paper, your statement just continues the dishonesty, misunderstandings, and invalid interpretations you must manufacture for your own satisfaction.

The term spinning singularity is far from a loose term, and in essence is a logical first requirement for any Kerr BH, by definition.
But since you fail to accept BH's anyway, you are behind the eight ball from the outset.

 

Perhaps at this stage, with the total utter confusion Rajesh has shown with the many accepted aspects of BH's and their types, [ should I list them all again? ] it is worth mentioning that the only physical part of a black hole is the mass/singularity. The other parts mentioned are mathematical boundaries. There is no physical barrier called an EH!!! it is just a parameter of spacetime where the curvature marks an escape velocity that is equal to "c" and which is governed by the mass/singularity.

 

Is it a late realisation or you are just summarising ?

 

For your benefit, so don't be too putout. Just trying to help.

 

Thanks !!

 

The maths will tell you that you can carpet a 16m² square room with a carpet measuring -4m by -4m. You can't, the "negative carpet" is a "non-real solution". Ditto for what supposedly goes on inside the event horizon. The reality is that the "coordinate" speed of light varies with gravitational potential, that the light doesn't get out because it's stopped, and that light can't go slower than stopped.

I can't. Maths doesn't show it. I can show you a sonar wave curving because the density of water varies. I can show you a light wave curving because the energy-density of space varies. I can show you the wave nature of matter. But maths doesn't show the why of it.

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That Chicken-Little metric doesn't correspond to reality. A gravitational field is NOT a place where space is falling inwards. It's a place where space is inhomogeneous. The energy-density varies. The waterfall analogy is fatally flawed because it doesn't correspond with anything Einstein said, it flatly contradicts Einstein and the evidence.

The space around you isn't falling down. And light doesn't curve down because it's moving through curved spacetime. It curves down because it's moving through inhomogeneous space, like Einstein said. You can think of this as "tilted spacetime" if it makes you feel happier. But don't get too happy, because as Quarkhead will tell you, there is no motion through spacetime.

I'm telling you what Einstein said, and Shapiro, and Don Koks and Ned Wright and so on, and I'm giving you the evidence. That isn't garbage. The waterfall analogy is garbage.

No, it conditions the surrounding space, making it inhomogeneous, such that the speed of light is spatially variable, this effect diminishing with distance in a non-linear fashion. When you plot this with say equatorial light clocks, the result is this:

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It's just \(t_0 = t_f \sqrt{1 - \frac{2GM}{rc^2}} = t_f \sqrt{1 - \frac{r_0}{r}} \). The light clocks run faster further from the Earth, the plot is shown higher there to represent this. What you think of as curved spacetime is just a plot derived from a "metric" which is in essence just a bunch of clock readings. Clocks don't run slower when they're lower because spacetime is curved, because that's just a plot of clock readings.

Because we define the second and the metre using the local motion of light. Then we use them to measure the local speed of light. Duh!

It's the CMB rest frame, which is the preferred frame of the universe. It isn't an absolute frame in the relativity sense, but it tells you your motion with respect to the universe. And the motion of light at the event horizon, is, with respect to the universe, zero.

Yeah. But don't confuse coordinate-independence with no coordinates at all.

Because he's slowed too. And he's made of electrons etc. Which are made of light. Literally, in pair production. And we can diffract electrons, de dah de dah.

Correct. And when he's slowed to a stop, he doesn't experience that either.

It's preferred. Because the buck stops with the universe.

I absolutely have. A gravitational field is only there because the speed of light is spatially variable. You know that's what Einstein said. And that light can't get out because it's stopped. And that it can't go slower than stopped. You must surely know all this by now? And therefore that what you've been taught is a cargo-cult pastiche of general relativity that utterly contradicts Einstein.

You mean you wouldn't be the first person to totally dismiss Einstein in favour of some cargo-cult Chicken-Little crap that totally contradicts him.

Yeah. It's what Susskind was telling me too with the elephant and the event horizon.

Because time travel is science fiction. Because that proper time is merely the cumulative measure of the local motion of light inside a light clock. And when the light-clock is moving at c or sitting at the event horizon, there isn't any. And by the way, it's about time you moved my threads back into the physics and maths section.

Continued.

 

The difference is that I know chirality is handedness, as do you. And that you know that if you tried to explain that interior region, I'd rip it to shreds.

They're clock readings. Remember we plotted the Riemann curvature with optical clocks? They tell you the relationship between the "coordinate" speed of light at two different locations.

The Schwarzschild radius.

It isn't a mathematical artefact. You can't change coordinates because to have a coordinate system light has to move, and it doesn't. It all comes back to a stopped observer and his stopped clock at a place where light is stopped. He doesn't see it ticking as normal. He's like the gedanken observer SR moving at c. He's a popsicle. He sees nothing.

In a place where light doesn't move, you have no way to measure time and distance. Whereupon your Eddington-Finkelstein coordinates collapse like a castle in the air. Ooh, I see somebody has sanitized the Wikipedia article, see an old version where you can read this: "They are named for Arthur Stanley Eddington[1] and David Finkelstein,[2], even though neither ever wrote down these coordinates or the metric in these coordinates. They seem to have been given this name by Misner, Thorne, and Wheeler in their book Gravitation." Talk about appealing to authority. You know that Thorne peddles time travel, and Wheeler did too? Jesus H Christ.

I've explained it enough. At r0 you get an undefined result that tallies with infinite time dilation and the chart going up to the end of time. There's no getting past that. A hoppity-skippety jump to the end of time and back is a "non real solution". Just like that negative carpet.

 

To the question, "Show me the maths that shows why a pencil falls down due to the variable speed of light. Or post a link, if you prefer.," Farsight replies:

There we have it: Farsight is rejecting the entire methodology of Einstein and every physicist after Newton. The definitive evidence that Einstein gave for his theories was the mathematics and how the mathematical results of his theory accorded with measurements derived from observations.

Those who want to do Farsight-Physics have a choice: either follow the church of Farsight or do the kind of physics that can make things and do things.

 

Paddo, I sent your post to Prof. Joshi, and asked him to please explain the apparent contradiction to his previous response. Here's what he wrote back:

 

How can a singularity not be spining , if not now , then at some point in its existence ?

 

Thanks tashja, great job as usual. I'm sure I already stated it, with the professor's previous reply.....He seems to be enforcing the premise that because we know nothing about the Singularity [even though we infer the BH/ergosphere to be spinning] we cannot really assign anything to the singularity. I accept his reasoning and I really don't see any contradiction in the paper I posted of his. I was just trying to impress on Rajesh my following take on his interpretation
In essence he does not say it does not spin, just that we are not able to stringently assign anything to it.
And worth noting, other professors have not taken exactly the stringent definition as he has applied. Not that anyone of them is wrong. I respect all for their knowledge and their replies
To illustrate how ridiculous the debate has been at times, he also says that he would not take strong objection to anyone claiming it does spin.

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Thanks again.

 

Reason it out pad

 

Paddoboy,

You want some musical words from me ?? Ideally I/Mods should blast you for your continued juvenile nonsense, still I leave it up to you to understand the point made by professor..

 

Thanks Tashja, but it appears you gave too much importance to Paddoboy's nonsensical interpretation.

 

Why don't you just for a change grow up?
And while you are at it, show me where the professor EVER says Singularities never spin.
You are without doubt, being deliberately obtuse.