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A New Area Law in General Relativity, questions.


beecee

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https://arxiv.org/pdf/1504.07627.pdf

A New Area Law in General Relativity:

"We report a new area law in General Relativity. A future holographic screen is a hypersurface foliated by marginally trapped surfaces. We show that their area increases monotonically along the foliation. Future holographic screens can easily be found in collapsing stars and near a big crunch. Past holographic screens exist in any expanding universe and obey a similar theorem, yielding the first rigorous area law in big bang cosmology. Unlike event horizons, these objects can be identified at finite time and without reference to an asymptotic boundary. The Bousso bound is not used, but it naturally suggests a thermodynamic interpretation of our result".

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OK, Can someone explain exactly [and simply of course] what this means....                                And while we are at it, the highlighted part in the following ......

https://phys.org/news/2019-07-einstein-relativity-theory.html

More than 100 years after Albert Einstein published his iconic theory of general relativity, it is beginning to fray at the edges, said Andrea Ghez, UCLA professor of physics and astronomy. Now, in the most comprehensive test of general relativity near the monstrous black hole at the center of our galaxy, Ghez and her research team report July 25 in the journal Science that Einstein's theory of general relativity holds up.

absolutely rule out Newton's law of gravity. Our observations are consistent with Einstein's theory of general relativity. However, his theory is definitely showing vulnerability. It cannot fully explain gravity inside a black hole, and at some point we will need to move beyond Einstein's theory to a more comprehensive theory of gravity that explains what a black hole is."

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My guess is the statement is taken out of context, or poor journalism. What I'm saying is that GR tells us that once the Schwarzchild radius is reached, further collapse is compulsory, and while we will never be able to  check inside, and convey our observational results to the outside world, GR isn't such a bad model to fall back on. Or is Andrea Ghez simply referring to conditions at the singularity as defined by the failure of GR at the quantum/Planck region?

7 minutes ago, beecee said:

https://phys.org/news/2019-07-einstein-relativity-theory.html

More than 100 years after Albert Einstein published his iconic theory of general relativity, it is beginning to fray at the edges, said Andrea Ghez, UCLA professor of physics and astronomy. Now, in the most comprehensive test of general relativity near the monstrous black hole at the center of our galaxy, Ghez and her research team report July 25 in the journal Science that Einstein's theory of general relativity holds up.

absolutely rule out Newton's law of gravity. Our observations are consistent with Einstein's theory of general relativity. However, his theory is definitely showing vulnerability. It cannot fully explain gravity inside a black hole, and at some point we will need to move beyond Einstein's theory to a more comprehensive theory of gravity that explains what a black hole is."

:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

My guess is the statement is taken out of context, or poor journalism. What I'm saying is that GR tells us that once the Schwarzchild radius is reached, further collapse is compulsory, and while we will never be able to  check inside, and convey our observational results to the outside world, GR isn't such a bad model to fall back on. Or is Andrea Ghez simply referring to conditions at the singularity as defined by the failure of GR at the quantum/Planck region?

The paper for the above is at https://science.sciencemag.org/content/early/2019/07/24/science.aav8137

Relativistic redshift of the star S0-2 orbiting the Galactic center supermassive black hole

Abstract

"General Relativity predicts that a star passing close to a supermassive black hole should exhibit a relativistic redshift. We test this using observations of the Galactic center star S0-2. We combine existing spectroscopic and astrometric measurements from 1995-2017, which cover S0-2’s 16-year orbit, with measurements in 2018 March to September which cover three events during its closest approach to the black hole. We detect the combination of special relativistic- and gravitational-redshift, quantified using a redshift parameter, ϒ. Our result, ϒ = 0.88 ± 0.17, is consistent with General Relativity (ϒ = 1) and excludes a Newtonian model (ϒ = 0) with a statistical significance of 5σ."

 

Edited by beecee
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10 minutes ago, StringJunky said:

Beecee: Isn't your bolded bit on GR's limits in that domain a long known fact? Isn't the same issue as when it gets close to the BB scenario?

Yep, agreed, but it still seems to be worded wrongly. From what little I know, we know gravity is spacetime curvature and its effects. What we don't know is the actual state of the mass/energy [and for that matter, space and time] at the quantum/Planck level, both at the BH and BB singularities....noting of course that most cosmologists now reject any physical singularity as defined by infinite spacetime curvature and density. The singularity terminology applies to where our laws of physics and GR fail us. At least that's the way I see it. So in effect, there is probably a surface of sorts at or below the quantum/Planck level?

Edited by beecee
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28 minutes ago, Mordred said:

I will read it later looks intriguing from a quick read. I will let you know what I think after I get a chance to properly study it. Be with family hehe RL...

:) Terrific! 

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The paper is an interesting read however I wish it had detailed the relevant mathematics. I know the mathematics exist that can support the paper but I wish they included it in the paper itself.

 GR doesn't restrict FTL but can work with future light cones and the resultant time reversal of entropy  as described by the paper. However you still have the singularity conditions under both states.

 In this solution all observers must also be FTL. I recall a news blip back in the late 80's of a paper that presented this solution if I recall originated by Australian physicists. Can't recall too much more than that lol.

 Anyways the paper is applying the holographic surface as the boundary between two sides of the light cone. 

However the surface is an apparent horizon ( section included in said article )

Edited by Mordred
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