Neutron Star

I resent the implication....

 

Log in or Sign up to hide all adverts.

That is one of the problems. The fossil field idea requires that the field be self propagating. Meaning that it is self sustaining once the initial mass crosses the event horizon. We have no evidence, aside from an unknown dark matter, that any gravitational field exists in the abscence of a gravitationally significant mass. We even describe black holes, where we cannot see or measure the mass, in terms of their mass.., working backwards from the field which can be, at least indirectly observed.

If you remember from an earlier thread one of the professors tashja quoted, even stated that frame dragging in the Kerr solution was connected across the event horizon... I think he did make that an intuitive or logical conclusion, but still...

 

Log in or Sign up to hide all adverts.

Isn't that explained by the fact that gravity/spacetime is nonlinear?
http://www.einstein-online.info/spotlights/gravity_of_gravity

 

Log in or Sign up to hide all adverts.

You need to explain yourself more clearly or at least provide a specific reference in the link.., it covers a lot of ground.

 

http://www.einstein-online.info/spotlights/gravity_of_gravity
One reason why the physics of general relativity is much more difficult than that of Newton's theory of gravity or the theory of electrodynamicsis a property called non-linearity. In short, gravity can beget further gravity - where gravitational systems are concerned, the whole is not the sum of its parts.

This has been done before, with some strong words between myself and Q-reeus....Can't remember which thread, but at least three professional replies basically supported the above, which is what I was taught.

 

Hi OnlyMe.....
To explain myself even more fully, can I give a reply by a GR theorist expert on a previous, now defunct form I was a part of.
James can vouch for this bloke's credibility and expertise if needed.
It was in reply to a question I had asked....
Now let me explain my reasoning carefully: GR is a local theory - and this is why I chose to answer the question this way, because we know a lot about the local workings of GR. You can only tell what's going on here and now by looking at space-times which can naturally communicate with here and now. In terms of the theory, any event can only be described meaningfully in terms of other events in its past light cone.

The immediate example which springs to mind is the space-time between the singularity and event horizon of a Schwarzschild black hole. We know there is space-time there, there is gravitational curvature. But the mass at the hole's singularity is in the future light cone of all events in this space-time, so it can't communicate with them. The gravitational field will only communicate with any infalling masses, but it would still exist if no mass were infalling. This is an undisputable example of a local space-time which exists without any mass. (And a real, plausible one, Greg).

Now Thorne, as one of the world's leading relativists, will understand the difference between local and global applications of the theory, and will see my point. As the question was asked by Blacky, the answer I gave is kinda definitive (ie it is a real example which proves the possibility).

If on the other hand we want to ask whether it is possible to have a global solution with space-time but without mass, this is a different question. I don't really think we should include discussions of the quantum vacuum in the answer because we don't yet understand what that has to do with space-time or gravity. I think GR is still probably the best tool to use to answer that question.

So let's look at cosmological models. The de Sitter model describes an expanding universe of constant curvature which is homogenous and isotropic because the global density is zero - ie all the mass has been removed from the universe. In this model the universal radius grows exponentially and the hubble constant (which helps define the expansion with time) is related to a non-zero cosmological constant (Lambda). Now it might be possible to equate Lambda with a quantum vacuum energy, but this has not yet been performed and so we're guessing to add that factor.

Basically what I've done here is give one local example and global example of space-times which can exist without mass. It seems those who disagree with me are largely talking philosophically. I'd like anyone who disagrees with me to show me where my examples are wrong (I think I'd have to have both examples shown to be wrong to be convinced).


Hope this helps!
Chris
or this one...To think about the situation in more detail, let's consider the spatial regions of a normal schwarzschild black hole. Given that gravitational information can't travel from the singularity outwards, how does the hole maintain its gravitational field? Remember that GR is a strictly local field, we can only discuss the gravity at a point two thirds of Rs from the centre in terms of what can be locally communicated there. In that sense, then, the bulk of the curvature of space-time at that point is due to a mass which can't communicate with it at all! Locally there is no mass in that particular space-time which is responsible for the shape there. In fact, it is the nonlinearity of space-time which is holding the curvature and providing the field at this point. I would argue that space-time and the associated gravity can exist in GR without gravitating masses.

Now BC you're faced with a conundrum. You've had reasonable sounding answers from two sources you (probably) trust. You're going to have to come up with what you believe to be the right answer for the right reasons. Remember to question everything you read regardless of source.

Please Register or Log in to view the hidden image!

)
The above answer was given in reply to my question re the following "answer" given by Sten Odenwald.
https://einstein.stanford.edu/content/relativity/a11332.html
Can space exist by itself without matter or energy around?
No. Experiments continue to show that there is no 'space' that stands apart from space-time itself...no arena in which matter, energy and gravity operate which is not affected by matter, energy and gravity. General relativity tells us that what we call space is just another feature of the gravitational field of the universe, so space and space-time can and do not exist apart from the matter and energy that creates the gravitational field. This is not speculation, but sound observation.

I don't believe I had a conundrum as Chris suggested. I see both experts as correct, Chris within the applicibility of GR, and Sten by extending into quantum gravity territory.
Please forgive the rather long-winded way of explaining with examples, the non linearity of gravity.

Please Register or Log in to view the hidden image!

 

This is interesting response from prof......

1. Few posts ago, in response to Q-reeus post, I had mentioned that the stability limit is (1.3 Rs) on account of sound speed getting higher than the speed of light even at that point (see pt# 2 below). So the star must become unstable even at 1.3 Rs and should explode or broken down there itself implying that even Rs would never reach and hence star getting unstable even before EH is formed....so formation of EH itself contradicts GR, how prof Hamilton is silent on that ??

2. Professor is forgetting one more thing for smaller stellar cores (around 1.5 - 3 Solar Mass), the condition of very high density causing sound speed higher than light speed thus contradicting GR, appears outside EH.......but for high mass star core this condition appears inside EH, after the NDP is overcome.....I am suggesting that NDP will not be overcome even inside EH, thus the question of density becoming much higher to enable sound speed higher than light speed will not come.......so professor's this argument is unsustainable, he can take the standard line that is once core is inside EH it must go to r= 0 as per GR.....But GR itself is weirdo inside EH...and when the star is collapsing GR equations inside core are a disconnect solution with boundary, not very useful leading to infinities.

 

OnlyMe, this is how you responded to that classical point singularity at Planck's level issue.

Your response suggests that you agree with Paddoboy !!

And how can you say that " No one can answer it. "

Its pretty simple, look at any invariant parameter, I have given one example long back, or you can take curvature, this becomes infinite at r = 0, suggesting singularity only at r = 0, it has a finite value at Planck's level...so no singularity at Planck's level.

 

Please Register or Log in to view the hidden image!

excuses, excuses, excuses, It's my theory, and I'm not letting go!....You are all ganging up on me, I'm right, I'm never wrong, your links are no good, more excuses, excuses, excuses, GR is wrong, I'm right... BHs don't exist, just BNS,...I'm the expert...I've been at it for 12 months...you're all crazy......I don't need any references, it's my word and I'm right....I'm right I tell ya!!!!!

Please Register or Log in to view the hidden image!

hohum..............

 

How does this childish nonsense contribute to the discussion ??

 

It brings far more to the discussion [like truth] then the following innane remarks..........

But that's OK, I don't believe in laying in the boot when someone is down, so I'll leave it at that...seeya!

 

To those who know better it is a cardinal sin to argue from authority or simply side with a majority of hands. Anyway, this diversion started in #162, the topic in a thread of which you cannot remember was thrashed out (beginning at #32) here:
http://www.sciforums.com/threads/black-hole-not-so-black.142702/
with further comment at:
http://www.sciforums.com/threads/neutron-star-to-black-hole.143965/page-31#post-3275449
and lastly in #616 there.
Given all participants this thread were participants in both above ones, it signifies Rajish is not the only one with psychological or at best memory issues to have it brought up here - as though it were somehow a fresh topic. I suggest either let it alone (recommended) or start a new one IF there is something genuinely new to bring to the table.

 

While responding to others recent posts you conveniently ignored my #155. Don't bother responding though, I only expect more contorted circular illogic.
Mitch Begelman's point in #158 was made and further added to (role of pressure), way back in #48. No sensible response then, so what would change that now? Oh wait, you did in a roundabout way respond in #66 and your #167 above. By actually arguing for inevitable material failure at r =< 1.3 r_s owing to implied sound speed >= c. Which against all logic supposedly would set off an explosion rather than unconstrained collapse to inside EH (standard GR scenario). Somehow invalidating EH formation?! But why then do you continue to hold to notion of BNS - existing stable and static inside, yes, an EH, as sensible and consistent! Your remaining blue texted point 2 is too incoherent to warrant comment. Such irrationality signifies deep psychological issues not physics issues. A refusal to let go, like that of for a precious and only (dead) child.

 

In a neutron, even one produced by electron degeneracy as would be the case in a neutron star, color charge is still exchanged by the single 'up', double 'down' quarks, and although other neutrons, and not protons, hold this massive nucleus together, there is no good reason I know that anyone should expect that this structure is much closer to an ideal rigid body than ordinary matter is. Quarks still have mass, and neutrons are made of quarks and gluons, and still have mass, so 'FTL' sound waves are a definite NO for a neutron star of any size that is composed of neutrons. Neutrons themselves cannot move FTL. Neither can sound waves transmitted by means of them.

Have observations of neutron stars been done that suggest otherwise?

This discussion has no good reason to heat up over this issue, at any rate.

Gravity may 'escape' as long as the Higgs mechanism works, which caused the collapse in the first place, and is essential for the quarks inside of neutrons, and the neutrons themselves, to have mass and continue to exist. Any other ideas?

 

danshawen - your #174 raises new speculative connections that e.g. somehow tie BH 'fossil' gravitational fields to Higgs field/mechanism. Please start a new thread if you really want to pursue it. I at least want this one dead and buried asap. As for sound speed in a NS, I recall seeing a figure of ~ %80-90 c as upper limit. Relativity forbids any material medium to have %100.

 

Done. Outtahere.

 

Thanks, and btw I just Googled (or better re privacy - StartPaged) "sound speed in a neutron star". First few hits will likely give you all you need re evidence for sound speed in NS's.

 

First, sorry it took so long to get back on this...

Both of the above prove my point, because they both require that you exclude anything that is not specifically an interpretation of GR and a modern interpretation at that. They also require that even where solutions to GR return predictions that are not consistent with experience, those predictions be accepted as real! The last sentence in paragraph two above, is maybe a little over the top.

He is referring to the spacetime inside of an event horizon. Yes, his point is consistent with predictions based on a solution to EFE, but it is anything but, an undisputable example of local spacetime.., the spacetime as predicted in the Schwarzschild black hole is theoretical. And it is separated from the mass that the black hole was form from, by two significant deviations from SR and experience.., an FTL escape velocity inside the event horizon which implies an FTL slide or fall into the singularity.., and the singularity itself, which few if any of the authorities we have heard from in the last several threads on Black Holes, believe represents anything real. Given that the mathematical singularity is not expected to represent anything real and the Schwarzschild solution itself is a simplification, that is not likely to exist anywhere in reality, while the example quoted in your post above has merit in a discussion of the theoretical implications, it cannot be seriously thought of as an undisputable example of a local spacetime.., a phrasing that implies that the conclusions are descriptive of experience and/or observations, rather than a theoretical extension of EFE, to an extreme that cannot be proven.

But this is getting way to critical of quotes which may be out of context in the current discussion. The author(s?) self limit their comment as theoretical with the following two lines early in each, the first and second distinct comments,

In the first paragraph and as the last comment begins...

​

I am pretty sure you introduced these same quotes in another thread. The problem I have with them is that for anything suggested in the above to have any merit, there has to be a starting agreement that the discussion is limited to GR and even then a modern interpretation of GR. As clarification, consider two conceptual interpretations of GR; a modern interpretation that assumes the spacetime geometry of a gravitational field is the cause of gravitation, and the more historical interpretation where the spacetime geometry is a dynamic description of how massive objects interact gravitationally, but makes no assumption that gravity itself emerges from that geometric description.

So back to the discussion here and your question,

Responding to my post,

The fossil field interpretation of GR, inherent in the theoretical arguments you cited, is not supported by any observation and/or experience (aside from theoretical) and requires that you set aside any consideration of the vacuum or possible QTG, and limit the discussion to a modern interpretation of GR.

Again few have any real objections, to a statement that asserts that the mathematical singularity predicted by these solutions, does not represent anything that exists in reality, all agree that GR breaks down at that point or shortly before. What I added is that there are unresolved issues that are raised by the event horizon, that cannot be removed except theoretically, while we have no means to confirm that those predictions, like the singularity.., represent anything real. All we know, is that there is a location in the spacetime around a gravitational field, externally consistent with what we expect a black hole to look like from outside the event horizon, that can be observed... Which only proves that the orbits of stars around an invisible location in space is consistent with a massive gravitational field and we cannot see anything at the center of that field.

The concept of a fossil field is a work around one of the implications of a theoretical FTL escape velocity, inside an event horizon. A work around that requires that we accept.., as real, theoretical predications about extreme gravitational fields, based on local observation of week fields... And by local here I mean what we can observe more directly in the relationship between massive objects in our own solar system.., which is what GR began as a description of...

Almost all of these discussions have intermingled GR and speculations involving some future QTG, so it is unrealistic to keep returning to arguments from authority that depend on limiting the discussion to single theoretical interpretation, especially when you add pack scale exceptions that are not compatible with the references above.

 

Rajesh, I don't have to agree or disagree, with anyone to request that you stop asking the same unanswerable question over and over!

And yes it is unanswerable. GR says nothing about about quantum mechanics and the Planck scale... And QM has not yet been reconciled with GR where Gravity is concerned, so no one can answer the question you are spamming the thread with. That fact that you cannot see that only proves that you have no idea about the physics, and validates the professor's comment in post #158.

 

To argue from authority is something we all have done, and as long as that authority is expert in the matter at hand, it can never be a cardinal sin and is always desirable and sometimes necessary as in this thread.
Secondly my argument in this thread and any thread is never based on a "majority of hands" as you suggest, and incidentlly as Rajesh has so childishly suggested a few times, especially since the first 3 replies in this thread at posts 2, 3, and 4 were mine, and it appears the "majority of hands" actually agree with me with regards to the larger picture.

My raising of the issue was in reply to OnlyMe, who it seems has given quite a lengthy appreciated answer.
Yep my memory was foggy on the thread and time, so? Maybe I'm getting old, but just as certainly, I certainly do not have any psychological problem over the issue as Rajesh has, and incidentally that you still seem quite touchy about.
Again the particular issue was in reply to my querie re a comment by OnlyMe at post 159, that carried forward in more precise details at posts163, 164, 165, and 166...nothing more, nothing less.
And by the way, your contribution to the main matter in this thread has been excellent and a worthwhile contribution.