A question about Hawking radiation

Foundations of physics and/or philosophy of physics, and in particular, posts on unresolved or controversial issues

A question about Hawking radiation

Postby SEKI » Mon Apr 30, 2018 1:10 pm

Hawking radiation postulates that particles with negative energy fall into a black hole.

Einstein's gravitational equation is presented in terms of linear expression of energy-momentum tensor.
So, I suppose that particles with negative energy, if actually present, are to be repelled by the black hole.

Then, isn't Hawking radiation unrealistic?
SEKI
 
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Re: A question about Hawking radiation

Postby Q-reeus » Mon Apr 30, 2018 9:41 pm

SEKI wrote:Hawking radiation postulates that particles with negative energy fall into a black hole.

Einstein's gravitational equation is presented in terms of linear expression of energy-momentum tensor.
So, I suppose that particles with negative energy, if actually present, are to be repelled by the black hole.

Then, isn't Hawking radiation unrealistic?

I agree and have made that point among various others elsewhere but it never sinks in. GR has long been promoted as the Gold Standard among classical theories of gravity. Einstein's aesthetic choice that gravitational field was purely geometric led him to reject a more consistent foundation he knew about back in 1907. See Appendix A here: https://arxiv.org/abs/1606.01417
That exact redshift derivation has no room for any 'event horizons' such as GR's Schwarzschild metric predicts, and which pathology led to 'Hawking radiation'.

Also, by the same author, an arXiv article showing how Yilmaz gravity nicely resolves 'dark energy' issue without needing 'dark energy': http://arxiv.org/abs/1507.07809
Explains there at some length why previous theorists had botched analyses that allowed GR-centric critics of Yilmaz gravity to misguidedly 'disprove' it.
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Re: A question about Hawking radiation

Postby SEKI » Tue May 01, 2018 7:08 am

Q-reeus wrote:
SEKI wrote:Hawking radiation postulates that particles with negative energy fall into a black hole.

Einstein's gravitational equation is presented in terms of linear expression of energy-momentum tensor.
So, I suppose that particles with negative energy, if actually present, are to be repelled by the black hole.

Then, isn't Hawking radiation unrealistic?

I agree and have made that point among various others elsewhere but it never sinks in. GR has long been promoted as the Gold Standard among classical theories of gravity. Einstein's aesthetic choice that gravitational field was purely geometric led him to reject a more consistent foundation he knew about back in 1907. See Appendix A here: https://arxiv.org/abs/1606.01417
That exact redshift derivation has no room for any 'event horizons' such as GR's Schwarzschild metric predicts, and which pathology led to 'Hawking radiation'.

Also, by the same author, an arXiv article showing how Yilmaz gravity nicely resolves 'dark energy' issue without needing 'dark energy': http://arxiv.org/abs/1507.07809
Explains there at some length why previous theorists had botched analyses that allowed GR-centric critics of Yilmaz gravity to misguidedly 'disprove' it.

Thanks for your valuable feedback.
SEKI
 
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Re: A question about Hawking radiation

Postby minkwe » Tue May 08, 2018 1:33 pm

SEKI wrote:Hawking radiation postulates that particles with negative energy fall into a black hole.

Einstein's gravitational equation is presented in terms of linear expression of energy-momentum tensor.
So, I suppose that particles with negative energy, if actually present, are to be repelled by the black hole.

Then, isn't Hawking radiation unrealistic?

"Negative energy" is unrealistic.
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Re: A question about Hawking radiation

Postby SEKI » Wed May 09, 2018 12:39 am

minkwe wrote:
SEKI wrote:Hawking radiation postulates that particles with negative energy fall into a black hole.

Einstein's gravitational equation is presented in terms of linear expression of energy-momentum tensor.
So, I suppose that particles with negative energy, if actually present, are to be repelled by the black hole.

Then, isn't Hawking radiation unrealistic?

"Negative energy" is unrealistic.

I think so.

If particles with negative energy are unrealistic, Hawking radiation is also unrealistic.
SEKI
 
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Re: A question about Hawking radiation

Postby SEKI » Wed May 09, 2018 1:03 am

The following is a posting of Dr. Steve Carlip to a moderated newsgroup of sci.physics.research.
https://groups.google.com/forum/#!forum ... s.research

SEKI wrote:On 5/5/18 8:50 AM, SEKI wrote:
> On Friday, May 4, 2018 at 4:59:21 PM UTC+9, Steven Carlip wrote:
>> On 5/1/18 1:41 PM, SEKI wrote:

[...]
>> First of all, what you've described is not the actual derivation
>> of Hawking radiation, but rather a hand-waving after-the-fact
>> description of the mathematics. If you were right, it wouldn't
>> mean Hawking radiation was unrealistic, it would just mean that
>> the description isn't a very good one. You really can't dodge
>> the math; reading pop sci descriptions can sometimes lead to
>> good questions, but it won't give you answers.

> I am sorry, I am neither a professional physicist nor young to
> become one. I merely would like to carry out a thought experiment.

>> But your argument is wrong, too. According to the equivalence
>> principle, the trajectory of an object in a gravitational field
>> is independent of its mass. In a vacuum, a hammer falls with the
>> same acceleration as a feather; a negative mass hammer would do
>> the same. It's simply not true that a negative mass particle
>> would be repelled by a black hole, in either general relativity
>> or Newtonian gravity.

> I am not sure this argument is right or not.

What would it take to make you "sure"?

>> It *is* true that a particle, of positive or negative mass, would
>> be repelled by a negative mass black hole.

> Isn't this inconsistent with what you wrote above?

No. A positive mass attracts everything (including both positive
and negative mass objects); a negative mass repels everything.

> Anyway, I acknowledge that mathematical models of modern physics
> is based on Einstein's equation as far as gravitation is concerned.
> As I wrote previously, Einstein's gravitational equation is
> presented in terms of linear expression of energy-momentum tensor.
> So, negative energy is considered to curve the space-time in the
> opposite direction to positive one. And, I suppose that particles
> with negative energy, if actually present, are to be repelled by
> the black hole.

Spacetime is four dimensional, and its curvature can't really be
described in terms of a "direction." You guess is roughly right,
though -- a positive mass source produces an attractive gravitational
field, and a negative mass source produces a repulsive gravitational
field (up to some subtleties about what counts in "mass").

The point, though, is that an attractive gravitational field attracts
*everything*, and a repulsive gravitational field repels *everything*.
In Hawking radiation, in particular, the black hole mass is positive,
and it's simply not true that it repels negative energy particles.

> If you give me a proof that my supposition is wrong, my question
> is to be resolved and it is really appreciated.

Again, what kind of "proof" do you want?

-- You could take the word of people who actually know general
relativity. (I've been teaching GR for more than 25 years, have
a textbook coming out soon, and have more than 100 published
papers, including a recent review paper on Hawking radiation,
https://arxiv.org/abs/1410.1486, with more than 50 citations in
Google Scholar.)
-- You could learn enough GR to see for yourself.
-- You could... well, I don't know. What else would be a "proof"
you'd accept?

Steve Carlip

I cannot understand his argument.

If you give me an objective interpretation of it, I really appreciate it.
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Re: A question about Hawking radiation

Postby Q-reeus » Wed May 09, 2018 3:52 am

While absense of an event horizon in a correct theory of gravity kills ab initio the claimed basis for Hawking radiation, one could question the logic behind it in other ways.
In 'pop-sci' presentations, the intense gravitational tidal forces near a BH EH tears apart a virtual particle/anti-particle pair, lifting both to become real. Seemingly by magic, only one of the pair has positive energy, the other an equal amount of negative energy. See e.g. para adjacent to 3rd box insert in:
https://www.physicsoftheuniverse.com/to ... heory.html

"Hawking showed how the strong gravitational field around a black hole can affect the production of matching pairs of particles and anti-particles, as is happening all the time in apparently empty space according to quantum theory. If the particles are created just outside the event horizon of a black hole, then it is possible that the positive member of the pair (say, an electron) may escape - observed as thermal radiation emitting from the black hole - while the negative particle (say, a positron, with its negative energy and negative mass) may fall back into the black hole, and in this way the black hole would gradually lose mass. This was perhaps one of the first ever examples of a theory which synthesized, at least to some extent, quantum mechanics and general relativity."

Some fairly obvious issues:

1: Since when do real particle/anti-particle pairs consist of other than positive mass-energy for each partner? Certainly never observed in particle accelerator collisions.
There is indirect evidence and hope for near future direct evidence of electron-positron pair creation from vacuum owing to creation of intense electric fields at or above the Schwinger limit of E ~ 1.32 x 10^18 V/m : https://en.wikipedia.org/wiki/Schwinger_limit
Real pair production with all particles of positive mass-energy is certainly the unambiguous prediction in Schwinger process 'vacuum polarization' case. Each particle in a pair continues to separate owing to opposite signs of charge, thus no 'horizon' is invoked or needed. As the ensuing current partially neutralizing the E field source (for say a hypothetical charged capacitor), or destructively interferes with the partially standing E fields generated by crossed pulsed laser beams, there is no paradox in respect of an overall energy balance.

In the gravitational case, where is there any such way to achieve an energy balance, other than by mathematical fiat turn one particle partner into a 'negative energy' beast?
But then if the total real particle pair energy is zero, why is copious production not energetically possible at arbitrarily small tidal field strengths? Not observed!

And on what basis would real positron-electron pairs be tidally produced except for tiny 'BH's' whose Hawking temperature is predicted to be very high. For a typical ~ 10 Solar mass 'BH', surely any tidal 'ripping apart' would overwhelmingly act on the zero-point EM field, producing much lower energy, uncharged real photon pairs. It's well known photons are their own anti-particle. No room there for a 'negative energy partner' - by definition surely. Perpetuum mobile physics then - net outward radiation of real photons, plus a growing 'BH' mass as the 'partner anti-photons i.e. photons' fall in.

2: Despite 1 above, suppose the dubious existence of 'negative energy' partner particles is for some reason exclusively granted in the gravitational case. The OP observation of gravitational repulsion of -ve energy particles/wave-packets/whatever, thus means both +ve & -ve energy partners escape. Provided one reasonably assumes only that
inertial mass m_i = passive gravitational mass m_p = active gravitational mass m_a - (1)
applies to both positive and negative energy particles. Notwithstanding the medley of scenarios Wikipedia presents: https://en.wikipedia.org/wiki/Negative_mass.
[that in red, and following link, hopefully at least partly deals with the question in above post - that came in while this one was being readied to answer to the previous post.]
None of which imo are fully self-consistent. In my judgement (1) implies inherent dynamic instability for even isolated negative energy particles. Inertial reaction feeding into rather than opposing any acceleration means exponential self-acceleration. In turn implying unlimited exponential growth of negative KE, given even the slightest initial disturbance. Crazy enough?
[And you know what may 'save' that bizarre scenario? That the very existence of a stable particle of negative inertial mass is likely impossible. Certainly for a composite particle like a proton, -ve inertial mass quarks would have no configuration with stable dynamics. Just how crazy it gets would no doubt depend on whether the gluons are given +ve or -ve effective inertial mass. If anything like string theory is true, a similar dilemma would surely hold for even say an elementary 'point particle' negative inertial mass electron.]
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