Posts Tagged ‘Quantum Field Theory’

BLACK HOLE RADIATION FROM SPLITTING PARTICLE PAIRS (Original Edition!)

July 21, 2020

Did Hawking “Lie” About Black Holes, As The Strident And Shallow Want Us To Believe? Or Was Hawking Honest and Deep?

Ethan Siegel, an astrophysicist who does a lot to disseminate physics to the masses, thinks valorous handicapped Hawking was a liar. Siegel, on fire, wrote:

Yes, Stephen Hawking Lied To Us All About How Black Holes Decay
The biggest error from ‘A Brief History of Time’ continues to misinform generations of aspiring physicists. Ethan Siegel wrote:

YES, STEPHEN HAWKING LIED TO US ALL ABOUT HOW BLACK HOLES DECAY

The biggest error from ‘A Brief History of Time’ continues to misinform generations of aspiring physicists. Ethan Siegel.”

Why is Siegel so insulting and furious? Is his daily bread threatened by the long dead Hawking? Well, maybe… I looked down on a quite a bit of Hawking physics, for reasons escaping common theoretical physicists, but I appreciated his courage. It was astonishing to see him zooming around, at jogging speed, along an extremely busy street full of indifferent American drivers. His physical condition was dreadful, truly horrible, and I never had much tolerance for those who were angry with him.    

Present day’s most advanced view of the material world (physics) is a mismatch of half baked theories, which is supposed to make sense and be experimentally confirmed, the Standard Model (SM). A more general framework is called QFT, Quantum Field Theory, Hawking’s crime? He broke ranks with the gravitas of the establishment, which prefer obscure computations full of hidden hypotheses, to bold conjectures.

…the funny part is that I always viewed Hawking as part of the establishment. So it is amusing to see Siegel furious at Hawking… for disrupting the establishment. Siegel wrote:

”in his landmark 1988 book, A Brief History Of Time, Hawking paints a picture of this radiation — of spontaneously created particle-antiparticle pairs where one member falls in and the other escapes — that’s egregiously incorrect. For 32 years, it’s misinformed physics students, laypersons, and even professionals alike.

Wow.

Why so much alarm, not to say hysteria? What is at stake? The ultimate picture of reality that we have, no less. Or more exactly the fact that we are supposed to respect the physics establishment for having figured out the nature of reality. In truth, they do not, they just want us to believe they did, because their way of life depends upon that. Hawking’s cavalier attitude is unbearable: it endangers an entire intellectual class of mandarins. 

An even funnier part of the whole thing is that the deus ex machina may turn out to have been no less than… yours truly. Yes, as far as I know, I originated the stupid idea which enrages Siegel so much. I generated the idea, not out of super-smartness necessarily, but because I couldn’t understand the more sophisticated mathematics and physics Hawking had originally used to demonstrate Hawking radiation… Moreover I like explicit mechanisms. Somehow, my stupid idea caught Hawking’s fancy (sorry to be that old…)

The alleged crime from yours truly, publicized by Hawking, villipended by Siegel: physics beyond the usual SM/QFT. (DEREK B. LEINWEBER)

The allegedly stupid idea is that, next to the Black Hole boundary, pairs of virtual particles may see one particle fall into the Black Hole, and the other escape to infinity. To this Siegel objects that: virtual particles are not real, so one of them can’t suddenly become real and escape. Even if that happened, as much anti-matter as matter would be emitted. 

The second point is silly: because of matter dominance, an antiparticle would quickly be neutralized by matter and turn to photons.

***

I sent the following to Siegel (which alludes to  metamathematics and (history of) mathematics most physicists are not familiar with):

Very interesting… And humbling. I may actually have been an originator of the problem, around 1980 (I knew very little QFT, but I thought that picture of the virtual pairs was cute at the time; I actually gave a Black Hole/Quantum seminar in Stanford then which Hawking and other world famous mathematicians and physicists whom I knew, attended; I presented that picture, nobody contradicted it, I didn’t think of some of the obvious objections above, nor did any of the prestigious assistance; on some other registers, I was accused of “meditating” too much when i presented some Quantum difficulties usually put under the carpet. The pair dividing “argument” gives an explicit mechanism… the curvature argument is more general… and vague, reminding me of Godel numbers; there are Gödel numbers, Gödel showed… but they can’t be computed. Only their existence can be demonstrated… Using the Axiom of Choice…)

As far as “virtual” particles are concerned, it’s not correct that they have no observable effects: Quantum Field Theory is all about those effects. Now people brandish “Green functions” and say, well, that’s what virtual particles are, that’s it. As laymen have no idea what “Green functions” are, that’s the triumph of the mystification. What I say is that, if it flies like a duck, walks like a duck and quacks like a duck, it’s got to be a duck.

The (real) central question in physics right now is related: whether wave functions are real, and, if so, in what sense (De Broglie’s theories, or something else).

If wavefunctions are real in the sense they can carry a tiny bit of mass-energy, they are not just “computational aids”, then all of physics will change. Big time (Dark Matter pops out immediately).

Many concepts once viewed as magical are now so much better understood that they are fully real. Remember that, for example, “imaginary” numbers (now “complex” numbers) were introduced in the 16C to solve some equations (by a surgeon, Cardano). Now, clearly they can be viewed as directly physical, since they depict so well basic… wavefunctions.

Anyway, thanks for the spirited, and informative essay…

***

The points I made are rather subtle (and require advanced knowledge, few mathematicians-physicists span the entire panorama). I suspect they may have motivated Hawking too. Because he obviously took great risks by contradicting the establishment. (A friend of mine, a Fields Medal, and expert in self-interested navigation, was all too ready to call Hawking a charlatan, I had to calm him down once.)

***

Black Hole 60 million light years away, as seen by the Earth spanning Event Horizon telescope. The radiation one sees in this picture is caused by classical, very well understood physics… The dotted line gives an idea of the size of this galactic size Black Hole…

Let’s quote the honorable Professor Siegel because he describes the situation well (even the non-fully enlightened have their uses…): 

“What Hawking would have had us imagine is a relatively simple picture. Start with a black hole: a region of space where so much mass has been concentrated into such a small volume that, within it, not even light can escape. Everything that ventures too close to it will inevitably be drawn into the central singularity, with the border between the escapable and inescapable regions known as the event horizon.

Now, let’s add in quantum physics. Space, at a fundamental level, can never be completely empty. Instead, there are entities inherent to the fabric of the Universe itself — quantum fields — that are always omnipresent. And, just like all quantum entities, there are uncertainties inherent to them: the energy of each field at any location will fluctuate with time. These field fluctuations are very real, and occur even in the absence of any particles.

A visualization of QCD illustrates how particle/antiparticle pairs pop out of the quantum vacuum for very small amounts of time as a consequence of Heisenberg uncertainty. The quantum vacuum is interesting because it demands that empty space itself isn’t so empty, but is filled with all the particles, antiparticles and fields in various states that are demanded by the quantum field theory that describes our Universe. Put this all together, and you find that empty space has a zero-point energy that’s actually greater than zero. 

In the context of quantum field theory, the lowest-energy state of a quantum field corresponds to no particles existing. But excited states, or states that correspond to higher-energies, correspond to either particles or antiparticles. One visualization that’s commonly used is to think about empty space as being truly empty, but populated by particle-antiparticle pairs (because of conservation laws) that briefly pop into existence, only to annihilate away back into the vacuum of nothingness after a short while.

It’s here that Hawking’s famous picture — his grossly incorrect picture — comes into play. All throughout space, he asserts, these particle-antiparticle pairs are popping in and out of existence. Inside the black hole, both members stay there, annihilate, and nothing happens. Far outside of the black hole, it’s the same deal. But right near the event horizon, one member can fall in while the other escapes, carrying real energy away. And that, he proclaims, is why black holes lose mass, decay, and where Hawking radiation comes from.”

Now for little Ethan Siegel’s hurt feelings:

That was the first explanation that I, myself a theoretical astrophysicist, ever heard for how black holes decay. If that explanation were true, then that would mean:

Hawking radiation was composed of a 50/50 mix of particles and antiparticles, since which member falls and which one escapes will be random,

that all of the Hawking radiation, which causes black holes to decay, will be emitted from the event horizon itself, and that every quantum of emitted radiation must have a tremendous amount of energy: enough to escape from almost, but not quite, being swallowed by the black hole.

Of course, all three of those points are not true. Hawking radiation is made almost exclusively of photons, not a mix of particles and antiparticles. It gets emitted from a large region outside the event horizon, not right at the surface. And the individual quanta emitted have tiny energies over quite a large range.”

*** 

When I first read this fulminating discourse from Siegel, I was taken aback that I had been that stupid for so long, by not seeing the splendid objections Siegel brandished. However, on second thoughts, there is nothing “of course” about any of these objections. Each of Siegel’s screams can be countered by cool rationality. And I had thought about them at the time, I had just forgotten them, as physicists and mathematicians seemed very uninterested by them at the time (I was surprised when Hawking used the argument). So here are my counter-arguments:

  1. Particles emitted at the event horizon, would be right away interacting with fields outside  of the event horizon, and soon half would turn into photons from antimatter annihilation, as I said already. Much of the rest of the energy would do the same, as most particles would stay gravitational prisoners… whereas photons, however shifted towards the red, would escape at the speed of light.
  2. The rest would have to climb out of the tremendous gravitational well, so would lose most of their energy… over quite a range, according to whatever collisions they experience. 

Another point is that the mechanism would become more prominent the smaller the Black Hole gets. So I stand by my cute idea, and command Hawking for his courage… To have presented it (implicitly) as his, at the risk of earning the contempt of his obscurantist peers. 

Patrice Ayme

***

***

P/S: I will develop this in other essays, but it’s no coincidence Einstein couldn’t learn Quantum Field Theory. The whole thing probably just looked to him like incantations with magic formulas. He tried for three weeks, taught by ehrenfest… Then gave up. Albert was smart enough to find the whole thing extremely fishy, with extremely deep errors hidden inside. Make no mistake: I am not saying QFT makes no sense. Neither to do I pretend Einstein was right in all ways. Far from it: QFT treats particles as extended, so does SQPR, and Einstein had made the error of believing otherwise

Large pieces of QFT make total sense, are glorious, obviously correct… Actually the whole point of my particle pairs-Black Hole imagery is to take some of QFT more seriously than the QFTists themselves take it…  Hey!

***

P/S 2: Sub Quantum Physical Reality SQPR fleshes out QFT. The spurious distinctions between virtual and non-virtual particles disappear… So does much of the over-inflated metaphysics of Relativity, and QFT.

 

Black Hole Paradox

September 1, 2015

Photons are the carriers of the electromagnetic field. Each single photon is endowed with a given energy, hf, where f is the frequency of said photon. In some circumstances, the energy a photon possesses is less than the one it needs to get out of a gravitational well. So it cannot get out: a black hole forms.

Essentially, this comes from the fact a photon’s energy is finite, whereas the energy of a gravitational field can grow infinitely… Or so I, and others, used to think, until I became skeptical.

No Doubt There Are Black Holes. Question: How Come?

No Doubt There Are Black Holes. Question: How Come?

Simulated view of a black hole in front of the Large Magellanic Cloud, one of many small galaxies satellite to the giant Milky Way. This Black Hole is assumed to be alone, without accretion disk (accretion would make the Black Hole very luminous!). The ratio between the black hole Schwarzschild radius and the observer distance to it is 1:9. Of note is the gravitational lensing effect known as an Einstein ring, which produces a set of two fairly bright and large but highly distorted images of the Cloud as compared to its actual angular size.

The two arcs of circle top and bottom are actually the Large Magellanic Cloud, appearing in two places, as light goes above and below the Black Hole. The Milky Way appears above, strongly distorted by gravitational lensing. [2006 image by French physicist Alain R.]

Gravitons are the (alleged) carriers of the gravitational field. Each of them has some energy. At some point the energy gravitons individually posses ought to be less than the potential energy needed to get out of a gravitational well. (The reasoning is the same as for photons.)

But then what?

In the case of photons, what is blocked is light the electromagnetic field: light, in another word.

What is blocked when gravitons get blocked? The gravitational field itself! Thus a black hole would not just then show up as a black, “frozen star”. A Black Hole should outright violate (apparent) matter conservation. It should disconnect gravitationally.

Following this simple logic, at some point a mass collapsing gravitationally should disappear, not just visually, but gravitationally.

Yet, astronomical observations reveal hyper massive black holes at the center of galaxies. This tends to indicate that physics may happen inside a black hole that we can neither observe, nor predict.

I presented these simple ideas a very long time ago in Stanford, a private university in California, personally or in seminars, to some of the household names in the field. The reaction of my iconoclasm was close to indignant anger. It’s easy to see why. We human beings live lives which are endowed with sense only by forgetting that we make little sense individually, absent others.

A way to make sense is by giving love and care. Another, mostly the obverse, by the will to power. A scientific, or, more generally, an intellectual career (philosopher, poet, writer, etc.)marries both love and power. Science, in particular, unites a potent hierarchy akin to priesthood, with the pretense of great magic vis-à-vis the public and being a gift to humanity. Or so it is perceived by its participants. Break the spell, and scientists feel as insects instead of semi-gods, and the absurdity of their position, that of thieves in full sight, exposed to the pillory, is too much to bear.

Yet, a quick glance at the history of science shows that great errors and lack of understanding, spectacularly erroneous theories could have been detected easily, with simple observations.

I am not saying that science is always simple. Far from it. For example, the heliocentric theory could be only demonstrated to be sure with 100% certainty, only after a careful study of the phases of Venus, through increasingly powerful telescopes, during the middle of the seventeenth century. Before that, geocentrism failed the smell test (it was too contrived, and the sun was so much bigger). True. The smell test is philosophical in nature. Before that, one could only say that it was un-scientific to rule out the most likely theory (heliocentrism), just because one could not prove it, and because it enraged so many people in high places.

It cannot be any different today: the very idea of the priesthood, scientific or not, is making some humans into quasi-gods. Out of this divine hierarchy comes the certainty that metaphysics has been solved.

Thus, when I suggested that, on the face of it, ultimately, Black Holes ought to disconnect gravitationally with the rest of the universe, I undermined the principle that the greatest scientists (I will not write their names as not to enrage them further), covered as they are with great medals, after all, do not understand much more about gravitation, than we did, say, three centuries ago.

I caused these people existential pain: no, you are not the greatest of the great, having achieved greater understanding than anyone did before you, colossally dominating history and humanity, and deservedly so. What you call greatest of the greatness, seems, after all, to be just errors of the smugly ignorant.

Einstein was not that way. He said:

All these fifty years of conscious brooding have brought me no nearer to the answer to the question, ‘What are light quanta?’ Nowadays every Tom, Dick and Harry thinks he knows it, but he is mistaken. (Albert Einstein, 1954)

Most importantly, Albert Einstein also suspected that Matter could not be described by field theory:

I consider it quite possible that physics cannot be based on the field concept, i.e., on continuous structures. In that case, nothing remains of my entire castle in the air, gravitation theory included, [and of] the rest of modern physics. (Albert Einstein, 1954)

In my theory, elementary particles are not only non-local (Einstein’s Error was to suppose that they were), but they break (giving rise to Dark Matter). But I will not go as far as to say that “nothing remains”. Far from it, my dear Uncle Albert. Quantum Field Theory remains, as an approximation. Just as the epicycle theory remains, as a sort of Fourier Analysis of a periodic motion.

Some physicists will laugh at the simplicity of the preceding reasoning, and just exasperatedly utter: “that’s ridiculous” as some of the most prestigious specialists of the field did to me, decades ago. Maybe it is. Just tell me why. I am humbly waiting.

Patrice Ayme’  


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