Black What ?

[Old_Geezer]

http://arxiv.org/abs/arXiv:1409.1837

I've been of the opinion that the amount of science in the recent threads here has been small, so I offer the above link for discussion. No real question, save maybe, does it have any validity ?

No axe to grind, I was just surfing and found a claim that Black Holes don't exist in reality. I have no idea if this is peer reviewed and taken seriously or not. Was hoping the more scientifically able could discuss in words I could understand :-)

It might get us around the uncomfortable belief in an infinitely dense singularity.

[janbee]

They were in Dr Who and that is good enough proof for me !

[ChillDoubt]

If Brian Cox and Stephen Hawking believe they do then I'll go with that.

[ToraToraTora]

This appears to be a mathmatical prediction based on the authors' understanding of hawking radiation during collapse we know that HR described a possible scenario for Black Hole decay and is anchored firmly in quantum theory and as such I will invoke the old addage, if you claim to understand quantum theory you have missed it entirely! Like the above, i'll go with Hawking and Cox.

[jim360]

TTT's dismissal is piffle.

[jim360]

I suppose really, I should just clarify that.

In the first place, that old adage was written by the past scientists (specifically Neils Bohr, if memory serves), who were just starting out in Quantum Mechanics, and whenever there's a transition from one school of thought to another the full implications of the "new school" are always likely to be difficult to take on board. These days QM is accepted and while its full implications aren't necessarily fully appreciated, the concept that an old quote can be drawn on to dismiss any modern paper on QM is, indeed, piffle.

With regards to the specific paper in question, I'm afraid it's way out of my area of study and I haven't really a hope of following it. I might pass it on to one of my colleagues who does work on GR and see if he has anything to say.

[ToraToraTora]

Ok jim fair enough, I was quoting an old curiosity.

[Old_Geezer]

The PDF is interesting, but quickly gives equations the like of which I've not had to play with since Uni, and graphs too. It just seemed to me to potentially be rather significant, when black holes seem invoked to explain so much and yet the implication is that they may be a figment of the imagination.

I must go find a Hawking Radiation for Dummies book somewhere. :-)

[jim360]

There are a number of caveats I think I can see at this point. In the first place Black Holes -- or, I suppose more accurately, black hole-like objects -- have been observed, so that there are things existing with black hole properties is not really in dispute. In the second place the paper considers only a specific and idealised model, so as per usual might not capture the real world precisely. This last is always a problem in Science, of course -- one just hopes that the approximation is "close enough". In this case a more accurate model may not display the explosive behaviour.

And in the third place all sorts of interesting stuff can go on mathematically that turns out to have no relevance to the physical world. What this paper shows, if it shows anything, is that the threshold between classical General Relativity and QM is even more bizarre than had previously been appreciated. It's possible -- indeed, almost certain -- that a more complete theory that fuses these two successfully would manage to find a way around this problem that allows black holes to form without approaching the singularity. In this sense, it's possible that this result is closer in nature to such papers as, say, the Rayleigh-Jeans paper of 1905.

I suppose I should briefly explain that one, although the story can be found in most popular histories of QM -- the result basically shows that in classical thermodynamics, the radiation of "black bodies" should blow up at high frequencies. Clearly it did not. The conclusion to be drawn from the paper, then, was that the then current understanding of physics was wrong. This was resolved five years earlier by Planck's work that laid the foundations for Quantum Theories (this timing is often forgotten -- Rayleigh's and Jeans' work proved the failure of old physics and was vital in allowing the new to be accepted).

If this paper is as ground-breaking, it will prove the failure of forced GR/ QM hybrid theories and provide a further reason to find a better understanding of Quantum Gravity.

[Old_Geezer]

Then even so it potentially has influence.

I searched further and found this that didn't seem to favour the new claim.

http://blogs.scientificamerican.com/cocktail-party-physics/2014/09/27/physics-week-in-review-september-27-2014/

"Physicist Laura Mersini-Houghton Claims to Have Proven Mathematically That Black Holes Do Not Exist in a (not yet peer reviewed) paper on the arXiv. Naturally, skepticism abounds. “The [paper] is nonsense,” [Bill] Unruh said in an email to IFLS. “Attempts like this to show that black holes never form have a very long history, and this is only the latest. They all misunderstand Hawking radiation, and assume that matter behaves in ways that are completely implausible.” So rumors of black holes’ death have been greatly exaggerated."

{sigh}

[jim360]

Yes, indeed a fourth caveat is the lack of peer-review. Bill Unruh's dismissal is interesting. Would have loved to be able to ask him about the whole thing... he's an interesting guy... but he's on the wrong side of the pond most of the time.

It should be said that despite this paper being beyond me I am rather surprised and indeed sceptical about its findings, although that shouldn't be taken to mean much.