Negative Energy -- Are QI/QEI's Real?

[cgreeleybsu]

TL;DR Summary

There is a lot of theoretical work and mathematical work on QI/QEI's however, there seems to be some, limited, experimental evidence that they do not exist. Is it probable I am being "led down the garden path" if I were to consider throwing out the idea of QI's given?

Hello all

I wasent sure if I should post this here or in GR. I was wondering anyone could help clear something up. In my research of negative energy, the idea of QI or QEI (Quantum Energy Inequalities) has come up, limits on negative energy. I have seen many papers showing mathematical descriptions (which I admittedly don't understand), and I never had a reason to question them (except the absence of physical observation) until I saw this paper entitled: "Experimental Concepts for Generating Negative Energy in the Laboratory" DOI: 10.1063/1.2169321 quote from the paper

The Quantum Inequalities (QI) conjecture is an ad hoc extension of the Heisenberg Uncertainty Principle. They were essentially derived by a small group of curved spacetime quantum field theory specialists for the purpose of making the universe look rational and uninteresting (Pfenning, 1998; see also the excellent review by Ford and Roman, 2003)

I later found this paper by chance: Testing a Quantum Inequality with a Meta-analysis of Data for Squeezed Light DOI: 10.1007/s10701-019-00286-8

which claims to analyze several sets of experimental data to show QI's to be false.

This paper as well: "Static Negative Energies Near a Domain Wall" gr-qc/0205134

We show that a system of a domain wall coupled to a scalar field has static negative energydensity at certain distances from the domain wall. This system provides a simple, explicit exampleof violation of the averaged weak energy condition and the quantum inequalities by interactingquantum fields. Unlike idealized systems with boundary conditions or external background fields,this calculation is implemented precisely in renormalized quantum field theory with the energynecessary to support the background field included self-consistently.

Davis & Puthof (first paper) also state:

This actually sounds quite reasonable on energy conservation grounds
until one finds out that the Casimir Effect (a squeezed vacuum state by virtue of its cavity boundary conditions) violates all three conditions

Which seems to be somewhat in agreement with "Some Thoughts on Energy Conditions and Wormholes" DOI 10.1142/9789812704030_0236

QIs don’t hold for the Casimir effect [48]. If the sampling time is chosen to be
small compared to the proper distance between the Casimir plates, then one does get
a QI bound [49]. Furthermore, the difference between the expectation value of the
energy density in an arbitrary state and in the Casimir vacuum state does satisfy a
QI bound [25, 50]. The physical interpretation of this “difference inequality” is that,
although it is possible to depress the energy density below the vacuum Casimir value,
it cannot be made arbitrarily negative for an arbitrarily long time. In the infinite
sampling time limit one finds that this difference of expectation values satisfies the
AWEC, even though the Casimir vacuum energy by itself does not"

(as well as QIs don’t hold for the Boulware vacuum state)Interestingly enough at the end of this paper it Roman states

The QIs have been proven to date only for free fields. It would be rather surprising
if the inclusion of interactions drastically modified the current picture. Otherwise,
one might worry that this might lead to instabilities in the free field theory as well.
However, given the Olum-Graham results, further study of interacting fields is needed."

And I did find this: "Quantum Energy Inequality for the Massive Ising Model" DOI 10.1103/PhysRevD.88.025019

A quantum energy inequality is derived for the massive Ising model, giving a state-independent lower bound on suitable averages of the energy density, the first quantum energy inequality to be established for an interacting quantum field theory with nontrivial S-matrix. It is shown that the Ising model has one-particle states with locally negative energy densities and that the energy density operator is not additive with respect to the combination of one-particle states into multiparticle configurations.

On every paper I have seen for QI's, no experimental evidence is given except for the existence of the effects mentioned (Casimir, squeezed light, etc.) search for the word "experiment" or "measure": The Generally Covariant Locality Principle
– A New Paradigm for Local Quantum Field Theory arXiv:gr-qc/9805037v1 this paper has the most mentions of actual data I have found.

Roman also says:

There is evidence that non-trivial spacetime-averaged QIs exist in 4D, although no simple analytic forms have yet been written down

Need to dig a little deeper to find out what that is (unless anyone here knows?)My question is, am I probably being "led down the garden path" if I were to consider throwing out the idea of QI's given:

A: The experimental evidence against (even though its just a couple of papers)
B: The lack of "pro" experimental evidence
C: They might not/do not apply to the Casimir Effect & Boulware vacuum state strangely as well as a number of spacetimes

vs. the pro reasons:

A: Lots of math and established work
B: There is a theory of an "interacting" QI
C: The "Static Negative Energies Near a Domain Wall" measures the Casimir effect which given the quasi agreement from some of the other sources, may not have QI apply hear and subtracts from the "against" evidence

Thank you
- Christopher A. Greeley

 

[PeterDonis]

the idea of QI or QEI (Quantum Energy Inequalities)

This paper will probably be helpful in understanding the context of those inequalities:

https://arxiv.org/abs/1208.5399

am I probably being "led down the garden path" if I were to consider throwing out the idea of QI's

It depends on what you want. If you want to try to build an FTL travel device or a time machine, you have no choice but to assume that the QI's can be violated, since if they can't FTL travel devices and time machines are impossible.

If you want something else, you need to be more specific about what it is you want before your question can be answered. For example: why do you care whether QI's are violated or not? If you're not actually trying to build an FTL device or a time machine, what difference does it make to you?

 

[cgreeleybsu]

This paper will probably be helpful in understanding the context of those inequalities:

https://arxiv.org/abs/1208.5399

Thank you, I did see this, but I really don't see anything experimental in there though.

It depends on what you want. If you want to try to build an FTL travel device or a time machine, you have no choice but to assume that the QI's can be violated, since if they can't FTL travel devices and time machines are impossible.

If you want something else, you need to be more specific about what it is you want before your question can be answered. For example: why do you care whether QI's are violated or not? If you're not actually trying to build an FTL device or a time machine, what difference does it make to you?

Yes I am interested in FTL travel, I really don't think that it necessarily means no FTL travel if QI's are correct (especially with the lack of limits in the Casimir effect). But I just want to know what the "safe bet" is without regard to weather or not I want FTL travel, I have tried to be unbiased in my research.

 

[PeterDonis]

I did see this, but I really don't see anything experimental in there though.

I'm not aware of any experimental demonstration of violations of QIs.

I really don't think that it necessarily means no FTL travel if QI's are correct

Then you are wrong. That's one of the points made in the paper I linked to. It's also the main reason why the authors of those other references you give are so interested in finding any evidence that QIs can be violated--because, like you, they are interested in FTL travel, and they know that violation of QIs is the only way for it to be possible.

I just want to know what the "safe bet" is

First, asking for a "safe bet" in an area at the frontier of science is kind of missing the whole point. But if you really want a safe bet, it's to assume that any proposal that violates our currently known laws of physics is not going to work.

Second, once again, why do you care? Is there a betting site somewhere where you can make money on bets with others about whether FTL travel is going to happen by a certain date? (If you know of one, please tell me so I can go there and make money.)

The point I'm trying to make is that, very often in science, the correct response is to have no opinion at all until more evidence is in. But a lot of people have a problem with that. Carl Sagan used to tell about all the people who asked him whether he thought there was intelligent life elsewhere in the universe. The answer he gave was always "we don't have enough evidence yet, so I don't know". And they were never satisfied with that, but would always press him: "But what do you think?" The correct response of a scientist is not to think anything in the absence of evidence. He might have hypotheses, he might try out various theoretical possibilities, but until the experiments are done and the evidence is in, he has no opinion one way or the other.

 

[PeterDonis]

especially with the lack of limits in the Casimir effect

What lack of limits are you talking about? The paper I linked to shows that the Casimir Effect is indeed within the bounds imposed by QIs.

 

[cgreeleybsu]

I'm not aware of any experimental demonstration of violations of QIs.

This paper:
Testing a Quantum Inequality with a Meta-analysis of Data for Squeezed Light DOI: 10.1007/s10701-019-00286-8
And to a degree this paper: "Static Negative Energies Near a Domain Wall" gr-qc/0205134
I would think, but I am not sure how strong they are

Then you are wrong. That's one of the points made in the paper I linked to. It's also the main reason why the authors of those other references you give are so interested in finding any evidence that QIs can be violated--because, like you, they are interested in FTL travel, and they know that violation of QIs is the only way for it to be possible.

Cant dig it up right now, but there are some things that lead me to think it may be possible within the context of QI, in general though I would bet on the side of human ingenuity.

First, asking for a "safe bet" in an area at the frontier of science is kind of missing the whole point. But if you really want a safe bet, it's to assume that any proposal that violates our currently known laws of physics is not going to work.

Sure.

Second, once again, why do you care? Is there a betting site somewhere where you can make money on bets with others about whether FTL travel is going to happen by a certain date? (If you know of one, please tell me so I can go there and make money.)

I have a project I am doing for school, for the purposes of it, I want to pick a direction.

The point I'm trying to make is that, very often in science, the correct response is to have no opinion at all until more evidence is in. But a lot of people have a problem with that. Carl Sagan used to tell about all the people who asked him whether he thought there was intelligent life elsewhere in the universe. The answer he gave was always "we don't have enough evidence yet, so I don't know". And they were never satisfied with that, but would always press him: "But what do you think?" The correct response of a scientist is not to think anything in the absence of evidence. He might have hypotheses, he might try out various theoretical possibilities, but until the experiments are done and the evidence is in, he has no opinion one way or the other.

I would agree with that (though I would say Sagan himself definitely had opinions on unproven matters such as string theory), like I said, purposes of the project I want to pick a direction. If it weren't for a project, I would probably want to design a test for QI, or I would have to pick a direction. If I were in a real lab and had to pick a direction where I was going to spend money, or I was going to spend hours/years designing something to generate negative energy I may also want to consider the "safe bet" there too

What lack of limits are you talking about? The paper I linked to shows that the Casimir Effect is indeed within the bounds imposed by QIs.

"Static Negative Energies Near a Domain Wall" gr-qc/0205134

We show that a system of a domain wall coupled to a scalar field has static negative energy density at certain distances from the domain wall. This system provides a simple, explicit example of violation of the averaged weak energy condition and the quantum inequalities by interacting quantum fields. Unlike idealized systems with boundary conditions or external background fields, this calculation is implemented precisely in renormalized quantum field theory with the energy necessary to support the background field included self-consistently.

Affirmed here https://arxiv.org/pdf/gr-qc/0409090.pdf in a quasi manner

QIs don’t hold for the Casimir effect [48]. If the sampling time is chosen to be small compared to the proper distance between the Casimir plates, then one does get a QI bound [49]. Furthermore, the difference between the expectation value of the energy density in an arbitrary state and in the Casimir vacuum state does satisfy a QI bound [25, 50]. The physical interpretation of this “difference inequality” is that, although it is possible to depress the energy density below the vacuum Casimir value, it cannot be made arbitrarily negative for an arbitrarily long time. In the infinite sampling time limit one finds that this difference of expectation values satisfies the AWEC, even though the Casimir vacuum energy by itself does not.

"Experimental Concepts for Generating Negative Energy in the Laboratory" DOI: 10.1063/1.2169321 quote from the paper

When generating negative energy via squeezed quantum states the QI postulates that: a) the longer the pulse of negative energy lasts, the weaker it must be, b) a pulse of positive energy must follow and the magnitude of the positive pulse must exceed that of the initial negative pulse, c) the longer the time interval between the two pulses, the larger the positive pulse must be. This actually sounds quite reasonable on energy conservation grounds until one finds out that the Casimir Effect (a squeezed vacuum state by virtue of its cavity boundary conditions) violates all three conditions

 

[PeterDonis]

Im not sure how strong they are

The first one is a meta-analysis, which, while interesting, is not really the same as "we ran an experiment to test a QI and found it to be violated".

The second one is not an experiment, it's a theoretical calculation.

Affirmed here https://arxiv.org/pdf/gr-qc/0409090.pdf in a quasi manner

Where "in a quasi manner" means "not really". The paper I linked to discusses this fine point: yes, you can find isolated points where a QI is violated in cases like the Casimir effect, but you cannot find sustained violations of QIs over a significant region. Things always average out so that QIs are satisfied over any region of significant size (where "significant" means "large enough to have a practical effect").

I have a project I am doing for school, for the purposes of it, I want to pick a direction.

What kind of project? Are you supposed to just pick an interesting hypothesis and explore its consequences? If so, it's much more interesting to hypothesize that QIs can be violated, than that they can't.

But if you're supposed to actually summarize our best current scientific knowledge, our best current scientific knowledge is that QI's can't be violated. You could add that there is research being done to try to test this more explicitly, but it's ongoing and cannot claim any generally accepted results yet.

 

[cgreeleybsu]

The first one is a meta-analysis, which, while interesting, is not really the same as "we ran an experiment to test a QI and found it to be violated".

Yes

The second one is not an experiment, it's a theoretical calculation.

Sorry my mistake, I had read a lot of papers that day

Where "in a quasi manner" means "not really". The paper I linked to discusses this fine point: yes, you can find isolated points where a QI is violated in cases like the Casimir effect, but you cannot find sustained violations of QIs over a significant region.

Yes (and its a bit ad hoc but Boulware vacuum state, as well as certain spacetime geometries). I just find the inconsistency interesting.

Things always average out so that QIs are satisfied over any region of significant size (where "significant" means "large enough to have a practical effect").

I would say that's a bit relative, and possibly a question of problem solving and engineering rather than a killer for FTL. Not saying you can necessarily doge it (the theory paper from before thinks you can, but who knows), but I am saying you may be able to work with the constraints.

What kind of project?

We are designing an experiment on a subject of our choice (relevant within GR).

Are you supposed to just pick an interesting hypothesis and explore its consequences? If so, it's much more interesting to hypothesize that QIs can be violated, than that they can't.

But if you're supposed to actually summarize our best current scientific knowledge, our best current scientific knowledge is that QI's can't be violated. You could add that there is research being done to try to test this more explicitly, but it's ongoing and cannot claim any generally accepted results yet.

I think this helps me a little get somewhat of a gauge on it (how accepted it is), thank you (that is not to say I accept based on what is accepted because its accepted [authority]).

 

[PeterDonis]

I am saying you may be able to work with the constraints.

If QIs are satisfied over any region of significant size, then they're satisfied over any region large enough to hypothetically allow, say, a human to travel FTL. Which means the human won't be able to travel FTL.

Even the cleverest engineering still has to abide by the laws of physics. So if the laws of physics are that QIs are satisfied over any region of significant size, even the cleverest engineering won't let a human travel FTL.

We are designing an experiment on a subject of our choice (relevant within GR).

So you want to design an experiment that tests QIs?

 

[cgreeleybsu]

If QIs are satisfied over any region of significant size, then they're satisfied over any region large enough to hypothetically allow, say, a human to travel FTL. Which means the human won't be able to travel FTL.

Even the cleverest engineering still has to abide by the laws of physics. So if the laws of physics are that QIs are satisfied over any region of significant size, even the cleverest engineering won't let a human travel FTL.

true, but in general, it seems we are dealing with questions of practicality and volume. Even if we could only send small things through say a worm hole, it might lend itself to all kinds of shenanigans. I did manage to dig up one of the sources I saw that suggest this is possible https://arxiv.org/abs/gr-qc/0207057 .

The first one is a meta-analysis, which, while interesting, is not really the same as "we ran an experiment to test a QI and found it to be violated".

I thought about this statement more, and while the people writing an experiment weren't there with the nitty gritty details of the experiment, they are basically doing the same thing as the experimenters, using the data, doing some math, and drawing some conclusions based on their knowledge of the setup and the data. Why isen't this almost as good if not as good as an experiment (assuming the results are repeatable)?

So you want to design an experiment that tests QIs?

That and the effect negative energy has on surrounding space time. The two have overlap.So far what I have got is a satellite at the L2 Lagrange point (behind the moon). A test bed inside the satellite (which acts as a faraday cage) detaches from the exterior hull to "inertially confine" it. This eliminates as many forms of interference both kinetic and electromagnetic as feasibly possible. As a matter of fact I go so far as to suggest the thrust unit and power source be attached to a structure element remotely attached to the craft via a cable (the craft would be towed, slight concerns over gravitational difference between one end of the craft and another, but it could be retracted if needed -- not the most important thing)

On the test bed there are several 4 blade neutron interferometer set ups https://core.ac.uk/download/pdf/35090668.pdf , (2:30), https://arxiv.org/abs/1910.14271

The first 3 have a plate on plate Casimir setup at 3 different planar orientations based on this paper https://arxiv.org/abs/quant-ph/0203002 that are within the sample area of the neutron interferometer.

I want to reduce as many sources of EM interference as possible, so I think I am going to modify it by taking as many servos out of the setup as possible (leaving only the nano servos) and instead opting for a retractable robotic arm that can be moved away from the setup.

Everything would be adjustable so the spacetime in different regions of the effect can be measured.Second, I have another neutron interferometer, this time a beam of squeezed light is produced via LiNbO₃ crystal, the beam can be adjusted (via retractable robotic arm) and will go through the sample area (detecting what happens with the negative energy when it occurs).

That is the first test with the squeezed light, the next one is based on these two papers https://www.researchgate.net/publication/228623774_Experimental_Concepts_for_Generating_Negative_Energy_in_the_Laboratory , https://www.researchgate.net/publication/45920800_Emitting_solitonized_laser_beams_to_boost_the_negative_energy_density_of_squeezed_regions_of_the_vacuumA sodium gas chamber is inserted into the beam path (with induction heating source) with an attached laser beam of its own, to act as a "multiplexer" to sort out the negative energy portions of the beam from the positive ones (newer better way to do this?).

However something about these two sources concern's me, Mansouryar paper was never published in a journal and Davis & Puthoff never cite Mansouryar in theirs but nab his drawing from his introduction.

This is to test if indeed we can create such a beam of negative energy, this is where we start to rub against QEI's.

Next there is another beam source, also from the Davis & Puthoff paper, 3 quantum dots perfectly timed and synchronized to fire a 1, 2, and 3 photon beam in close proximity, have all their beams merged via combined via filled-aperture combining through a diffraction grating (I wasen't exactly sure how Davis & Puthoff wanted these beams to be "classically lensed/combined" they don't really say, I also am not sure if Quantum Dots can produce 2 and 3 photon beams via timing, the only other methods I am aware of would to be either: have some really complicated setup to try to align the photons from 6 quantum dots in this way OR deal with the non-antibunching of a low powered laser).

This again would rub against QEI.The last thing to be tested are QEI's for interacting states, Roman in this paper https://arxiv.org/abs/gr-qc/0409090 asserts that there are no QEI's for interacting states. I am not too familiar with what interacting states are, however this paper claims it found one in the Ising model https://arxiv.org/abs/1304.7682 which AFAIK has to do with dipoles and Brillouin Scattering. The results of performing Brillouin Scattering on Carbonate are known, so the next step is to fire any of the squeezed light beams (combind, multiplexed, plain) at a sample of carbonate with an attached compact Fabry–P´erot interferometer to see what the results are and test Bostelmann and colleagues predictions.

Next a toriodal ferromagnet can also be targeted by the beams so the Debye model can be tested for QEI's via the Faraday Effect, another "interacting state" model. Once again, I don't quite understand the Debye model, but I know it has to do with electromagnetisim. I am only vaugely familiar with statmech for quantum mechanics.

Finally these tests can also be conducted by a squeezed light x-ray/neutron beam going through a LiNbO₃ crystal (by redirecting half the beam via beam splitter).

 

[PeterDonis]

I did manage to dig up one of the sources I saw that suggest this is possible

You can dig up sources that speculate that all kinds of things are possible. But those are just speculations. There's not much point in discussing speculations unless there is experimental data that can be used to test them.

Why isen't this almost as good if not as good as an experiment (assuming the results are repeatable)?

Your parenthetical comment at the end answers the question. A meta-analysis generates no new data. So it literally cannot tell you whether new data would show that the effect that is claimed in the existing data is repeatable. To test that, you have to go out and get new data.

Meta-analyses can be useful in cases where there are mountains of data from many different experiments that have not been pulled together into a single picture, usually because each individual group of experimenters was focused on their particular piece and no one has taken a step back to get a broader view.

In the case under discussion, by contrast, we have very little data, and if there's one thing that isn't lacking in everyone who is speculating in this field, it's a broader view. Everybody is all excited about any possibility of FTL or time travel, so even the tiniest ripple in the data is going to be seized on by somebody. The history of science is replete with examples of hypothetical effects that would be very exciting if they were real, which were claimed to be seen in tiny hints from tiny bits of data, and which turned out to be nothing as more data came in.

What you choose to spend your time and effort on is, of course, up to you, just as is the case with the experimenters that continue to try things in this field even if, in some cases they have been trying for decades with no real results (e.g., Puthoff, who has been working on this stuff since the 1970s, IIRC). But trying new experiments in this field, like those you describe, is original research, and original research is not what PF is for.

 

[PeterDonis]

The OP question has been answered, and original research is out of bounds for discussion. Thread closed.