GR rebukes again + Quest for what bars Q superpositions from large scale objects

#1
C C Offline
Physicists keep trying to break the rules of gravity but this supermassive black hole just said 'no'
https://www.livescience.com/black-hole-i...again.html

EXCERPTS: A new test of Albert Einstein's theory of general relativity has proved the iconic physicist right again - this time by re-analyzing the famous first-ever picture of a black hole , which was released in April 2019.

That image of the supermassive black hole at the center of galaxy M87 was the first direct observation of a black hole's shadow - the imprint of the event horizon, a sphere around the black hole's singularity from which no light can escape. Einstein's theory predicts the size of the event horizon based on the mass of the black hole; and in April 2019, it was already clear that the shadow fits general relativity's prediction pretty well.

But now, using a new technique to analyze the image, the researchers who made the picture showed just how well the shadow fits the theory. The answer: 500 times better than any test of relativity done in our solar system. That result, in turn, puts tighter limits on any theory that would seek to reconcile general relativity, which describes the behavior of massive celestial objects, with quantum mechanics, which predicts the behavior of very small things.

[...] General relativity must be incomplete, physicists believe, because it contradicts quantum mechanics. Physicists believe that discrepancy signals the presence in our universe of some larger, all-encompassing mechanism describing both gravity and the quantum world that they have yet to uncover. Looking for cracks in relativity, they hope, might turn up clues to help them find that complete theory."We expect a complete theory of gravity to be different from general relativity, but there are many ways one can modify it," University of Arizona astrophysicist Dimitrios Psaltis said in a statement... (MORE - details)


Could Schrödinger's cat exist in real life? Our research may soon provide the answer
https://theconversation.com/could-schrod...wer-147752

EXCERPTS: Quantum systems are ruled by what’s called a “wave function”: a mathematical object that describes the probabilities of these different possible situations. And these different possibilities can coexist in the wave function as what is called a “superposition” of different states. For example, a particle existing in several different places at once is what we call “spatial superposition”.

It’s only when a measurement is carried out that the wave function “collapses” and the system ends up in one definite state. Generally, quantum mechanics applies to the tiny world of atoms and particles. The jury is still out on what it means for large-scale objects. In our research, published today in Optica, we propose an experiment that may resolve this thorny question once and for all.

[...] After much debate [in the past], the scientific community at the time reached a consensus with the “Copenhagen interpretation”. This basically says quantum mechanics can only apply to atoms and molecules, but can’t describe much larger objects. Turns out they were wrong. In the past two decades or so, physicists have created quantum states in objects made of trillions of atoms — large enough to be seen with the naked eye. Although, this has not yet included spatial superposition.

But how does the wave function become a “real” object? This is what physicists call the “quantum measurement problem”. It has puzzled scientists and philosophers for about a century. If there is a mechanism that removes the potential for quantum superposition from large-scale objects, it would require somehow “disturbing” the wave function — and this would create heat. If such heat is found, this implies large-scale quantum superposition is impossible. If such heat is ruled out, then it’s likely nature doesn’t mind “being quantum” at any size.

If the latter is the case, with advancing technology we could put large objects, maybe even sentient beings, into quantum states. Physicists don’t know what a mechanism preventing large-scale quantum superpositions would look like. According to some, it’s an unknown cosmological field. Others suspect gravity could have something to do with it. This year’s Nobel Prize winner for physics, Roger Penrose, thinks it could be a consequence of living beings’ consciousness.

Over the past decade or so, physicists have been feverishly seeking a trace amount of heat which would indicate a disturbance in the wave function. To find this out, we’d need a method that can suppress (as perfectly as is possible) all other sources of “excess” heat that may get in the way of an accurate measurement. We would also need to keep an effect called quantum “backaction” in check, in which the act of observing itself creates heat.

[...] The experiment we propose is challenging. It’s not the kind of thing you can casually set up on a Sunday afternoon. It may take years of development, millions of dollars and a whole bunch of skilled experimental physicists. Nonetheless, it could answer one of the most fascinating questions about our reality: is everything quantum? And so, we certainly think it’s worth the effort... (MORE - details)
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#2
Syne Offline
(Oct 15, 2020 10:41 PM)C C Wrote: Physicists keep trying to break the rules of gravity but this supermassive black hole just said 'no'
https://www.livescience.com/black-hole-i...again.html

[...] General relativity must be incomplete, physicists believe, because it contradicts quantum mechanics. Physicists believe that discrepancy signals the presence in our universe of some larger, all-encompassing mechanism describing both gravity and the quantum world that they have yet to uncover. Looking for cracks in relativity, they hope, might turn up clues to help them find that complete theory."We expect a complete theory of gravity to be different from general relativity, but there are many ways one can modify it," University of Arizona astrophysicist Dimitrios Psaltis said in a statement... (MORE - details)
They seem to miss the fairly obvious. "Some larger, all-encompassing mechanism describing both gravity and the quantum world" doesn't imply "a complete theory of gravity to be different from general relativity". Like Newtonian gravity before it, it's highly likely that any larger mechanism would still produce the same results as GR, within a certain domain of applicability.


Quote:Could Schrödinger's cat exist in real life? Our research may soon provide the answer
https://theconversation.com/could-schrod...wer-147752

[...] After much debate [in the past], the scientific community at the time reached a consensus with the “Copenhagen interpretation”. This basically says quantum mechanics can only apply to atoms and molecules, but can’t describe much larger objects. Turns out they were wrong. In the past two decades or so, physicists have created quantum states in objects made of trillions of atoms — large enough to be seen with the naked eye. Although, this has not yet included spatial superposition.
Well...

Here we report such an experimental demonstration, with the moving bodies being two massive micromechanical oscillators, each composed of about 1012 atoms, coupled to a microwave-frequency electromagnetic cavity that is used to create and stabilize the entanglement of their centre-of-mass motion15,16,17. We infer the existence of entanglement in the steady state by combining measurements of correlated mechanical fluctuations with an analysis of the microwaves emitted from the cavity.
https://www.nature.com/articles/s41586-018-0038-x

...I'm not so sure a center-of-mass really qualifies as an entangled state, and definitely not something that can be "seen with the naked eye". I mean, we don't really have to "infer the existence" of things we can plainly see. Seems they are seriously out over their skis on that one.

Quote:But how does the wave function become a “real” object? This is what physicists call the “quantum measurement problem”. It has puzzled scientists and philosophers for about a century. If there is a mechanism that removes the potential for quantum superposition from large-scale objects, it would require somehow “disturbing” the wave function — and this would create heat. If such heat is found, this implies large-scale quantum superposition is impossible. If such heat is ruled out, then it’s likely nature doesn’t mind “being quantum” at any size.
That seems like an unjustified assumption. Who says potential is "removed" from the wave function? The Copenhagen interpretation certainly doesn't make any such presumption. That would seem to presume, unfounded, that all the potential states of the wave function are particle energies (degrees of freedom) that would have to be shed as heat. Seems pretty fringe to me.
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#3
confused2 Offline
The Cat article which CC linked to seems to be a superposition of two papers
one of which is here; https://www.osapublishing.org/DirectPDFA...&mobile=no
and the other is unknown.
I haven't read my linked article in full but it looks interesting - I have to assume some of the ideas mentioned represent current thinking - there may have been some changes over the last 50 years.

The Continuous spontaneous localization model is new to me - see:
https://en.wikipedia.org/wiki/Continuous...tion_model
Entangled massive oscillators (arxiv) here:
https://arxiv.org/pdf/1711.01640.pdf
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