Quantum vacuum: Less than zero energy

quantum
Credit: CC0 Public Domain

Energy is a quantity that must always be positive—at least that's what our intuition tells us. If every single particle is removed from a certain volume until there is nothing left that could possibly carry energy, then a limit has been reached. Or has it? Is it still possible to extract energy even from empty space?

Quantum physics has shown time and again that it contradicts our intuition, which is also true in this case. Under certain conditions, negative energies are allowed, at least in a certain range of space and time. An international research team at the TU Vienna, the Université libre de Bruxelles (Belgium) and the IIT Kanpur (India) have now investigated the extent to which negative is possible. It turns out that no matter which quantum theories are considered, no matter what symmetries are assumed to hold in the universe, there are always certain limits to "borrowing" energy. Locally, the energy can be less than zero, but like money borrowed from a bank, this energy must be "paid back" in the end.

Repulsive Gravity

"In the theory of General Relativity, we usually assume that the energy is greater than zero, at all times and everywhere in the universe," says Prof. Daniel Grumiller from the Institute for Theoretical Physics at the TU Wien (Vienna). This has a very important consequence for gravity: Energy is linked to mass via the formula E=mc². Negative energy would therefore also mean negative mass. Positive masses attract each other, but with a negative mass, gravity could suddenly become a repulsive force.

Quantum theory, however, allows negative energy. "According to quantum physics, it is possible to borrow energy from a vacuum at a certain location, like money from a bank," says Daniel Grumiller. "For a long time, we did not now about the maximum amount of this kind of energy credit and about possible interest rates that have to be paid. Various assumptions about this "interest" (known in the literature as "Quantum Interest") have been published, but no comprehensive result has been agreed upon.

The so-called "quantum null energy condition" (QNEC), which was proven in 2017, prescribes certain limits for the "borrowing" of energy by linking relativity theory and quantum physics: An energy smaller than zero is thus permitted, but only in a certain range and only for a certain time. How much energy can be
borrowed from a vacuum before the energetic credit limit has been exhausted depends on a quantum physical quantity, the so-called entanglement entropy.

"In a certain sense, entanglement entropy is a measure of how strongly the behavior of a system is governed by ," says Daniel Grumiller. "If quantum entanglement plays a crucial role at some point in space, for example close to the edge of a black hole, then a negative energy flow can occur for a certain time, and negative energies become possible in that region."

Grumiller was now able to generalize these special calculations together with Max Riegler and Pulastya Parekh. Max Riegler completed his dissertation in the research group of Daniel Grumiller at the TU Wien and is now working as a postdoc in Harvard. Pulastya Parekh from the IIT in Kanpur (India) was a guest at the Erwin Schrödinger Institute and at the TU Wien.

"All previous considerations have always referred to quantum theories that follow the symmetries of Special Relativity. But we have now been able to show that this connection between negative energy and quantum entanglement is a much more general phenomenon," says Grumiller. The energy conditions that clearly prohibit the extraction of infinite amounts of energy from a vacuum are valid for very different quantum theories, regardless of symmetries.

The law of energy conservation cannot be outwitted

Of course, this has nothing to do with mystical "over unity machines" that allegedly generate energy out of nothing, as they are repeatedly presented in esoteric circles. "The fact that nature allows an energy smaller than zero for a certain period of time at a certain place does not mean that the law of conservation of energy is violated," stresses Daniel Grumiller. "In order to enable negative energy flows at a certain location, there must be compensating positive energy flows in the immediate vicinity."

Even if the matter is somewhat more complicated than previously thought, energy cannot be obtained from nothing, even though it can become negative. The new research results now place tight bounds on negative energy, thereby connecting it with quintessential properties of quantum mechanics.


Explore further

Is the universe a hologram?

More information: Daniel Grumiller et al. Local Quantum Energy Conditions in Non-Lorentz-Invariant Quantum Field Theories, Physical Review Letters (2019). DOI: 10.1103/PhysRevLett.123.121602
Journal information: Physical Review Letters

Citation: Quantum vacuum: Less than zero energy (2019, October 2) retrieved 20 October 2019 from https://phys.org/news/2019-10-quantum-vacuum-energy.html
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Oct 02, 2019
dE.dT =>hbar/2 ?

Oct 02, 2019
This is yet another context where the NULL (or ZERO) is misunderstood as to its meaning in REALITY PHYSICS terms. That is, the null/zero quantum energy state actually represents the UNIVERSAL *AVERAGE* ENERGY DENSITY STATE of the underlying energy-space 'fabric' which everything forms in/from and propagates along. Hence the "NEGATIVE ENERGY" state in Quantum Vacuum is merely a "below average" energy state in that particular location; and hence any "borrowing" merely transiently REDUCES that local quantum energy density while INCREASING the energy density of the adjacent location. Moreover, that also means that the Universe DOES have ABSOLUTE POINTS OF REFERENCE by consequence of ALL LOCATIONS being thus effectively manifested ALL THE TIME across infinite energy-space quantum vacuum totality of all locations. Just because our measurements/theories have so far not been able to fully encompass such an infinite totality of locations, it doesn't mean it is not there. :)

Oct 02, 2019
If you consider gravity affected space as compressed, then the density can be lower and therefore considered "negative", but you can not have a "negative distance" in E=MC^2

Oct 03, 2019
Or it may well be that E=mc^2 is wrong, that the definition of energy is wrong & that the definition of mass is wrong.

Question everything, always expecting a better answer.

Oct 03, 2019
Experiments have proven that these things are not true. That's data, not theory.

If you're denying data, you're a crank. It's just that simple.

Oct 03, 2019
Experiments merely "suggest" that it's true, NOT that it's some absolute god-given omniscient truth. You really seem to have trouble with this distinction.

Also, remember that while one's data may be accurate & precise, the conclusions/theories one makes about the data may be utter trash. You appear to have trouble with this distinction too.

Why is it that no matter the scientific topic, you treat current knowledge of the topic as gospel truth that will never be invalidated? You seem to be religious about science, quite frankly, and I find that awfully disturbing.

Oct 03, 2019
If you consider gravity affected space as compressed, then the density can be lower and therefore considered "negative", but you can not have a "negative distance" in E=MC^2
E=mc² is an equation derived from special relativity. It is about the potential energy contained in matter and has noting to do with gravity.

Oct 03, 2019
Experiments don't "suggest" anything. They make it apparent what's real and what is not.

They build one on another and produce things like jet aircraft, refrigerators, and the very computer you are using to make idiotic comments on the Intertubes with.

Oct 03, 2019
"No amount of experimentation can ever prove me right; a single experiment can prove me wrong" - Einstein

...But your version, Da Schneib, is that Einstein has been proven right & that nothing can ever prove him wrong.

Oct 03, 2019
How many trials do you want? I wouldn't even care to estimate the number of trials Einstein has been put to but it would be beyond the tens of thousands. I'm not saying quit looking; but everywhere we've looked so far, over an enormous number of checks, we've gotten the same answers.

If you don't have a viable (that is, experimentally demonstrable) alternative, I'll stick with the one that has the best track record. You've had a hundred years and you're still wrong. What do you want?

Oct 03, 2019
@Da Schneib
"Experiments don't "suggest" anything. They make it apparent what's real and what is not"

If that were true, then quantum experiments which scientists said only "suggested" that objective reality doesn't exist, would have instead said that those experiments showed that it definitely doesn't exist, or that it definitely does exist.

https://www.techn...reality/

Oct 03, 2019
How many trials do you want?

It works.

Get over it.

Oct 03, 2019
Da Schneib, my original point was that even if thousands of experiments support it, even if everywhere we've looked so far supports it, even if an enormous number of checks have been done, even if we've gotten the same answers, and even if there's no major contender for replacing the theory... IT CAN STILL BE WRONG!!!

All I want you to do is ADMIT that and have some of that "objectivity" I harp on about. Why is that so hard for you? You seem obsessed with treating science like a religion, where certain theories are absolute god-given utterly infallible and unquestionable truths. You need to have some damn humility and realise that we don't have all the answers and that it is arrogant to think that we do.

Oct 03, 2019
No amount of trials can ever prove anything. That's why science is a "never-ending" search for the truth.

Oct 03, 2019
It is about the potential energy contained in matter and has noting to do with gravity.


LOL!

Potential energy is negative, and the mass = E/C**2 determines in part the strength of the gravitational field associated with M.


Oct 03, 2019
Compressed space is Mass ... Compressed space is gravity.
The speed of light is a distance in space i.e Energy=Distance squared multiplied by mass.
On the G space (Weight) scale you replace the Mass with C to get the C^3 scale.
General Relativity is all about the time dilation required to make the mass persist

Oct 03, 2019
You've had a hundred years and you're still wrong. What do you want?


They want something that they can understand.

I don't blame them.

Prediction is not sufficient, but it may be the best that can be done.

Insufficient effort has been expended in the area of explanation IMO.

Oct 03, 2019
As Reality Check says.. the thing is a misunderstanding issue for many.. and as-so.. the fact is mere.. this kind of a thing..: modulation and the horizon of event never having meant to to have reached the speed of light tells us that Einstein's Relativity is real or proven or proving. And at the moment zero opposing arrows in a streched bow aswhere do indicate -1 &+1 values for potential due to spatial direction .. the total 0/zero |0|.. moment has a two opposites like |1|=(-1) or (+1).. there is a twin of (-0) and a (+0).. and no need to guess how many values might √0 on its own universally indicate as both sets and elements! Consider 0db.. +db.. -db.. in audio and radiology.. so as you reach the speed of light then only you get the mass! Unrelatedly!..: 0=0 => E=mc^2=0 & empty set!

Oct 03, 2019
Compressed space is Mass ... Compressed space is gravity.
The speed of light is a distance in space i.e


Your statements are completely meaningless.

You can't compress space. At least not locally. Can you tell me why that is true for local space and why it isn't true for extended regions of space?


Oct 03, 2019
So was all of the mass/energy in our universe "borrowed" from the vacuum during inflation in some manner that it couldn't be repaid, then?

@Da Schneib, was hoping to discuss the 121 decimal place vacuum energy discrepancy on the quantum foam article's thread if you want.

Oct 03, 2019
@VendicarKhan
If the fabric of the thing we call space is the superstring.. and if there is explosion.. there(-it-by) happens to be deplosions and implosions aswhere |E|mplosions like as that explosions do occur.. {I guess.. :-)..}.

Oct 03, 2019
Velocity and Gravity cause time dilation.
Velocity and Gravity cause compressed space.
In a compressed space light appears to travel slower (I.E. Time Dilation), assuming the observer is outside the compression.
Yet inside the compressed space everything appears normal.
Special Relativity bud.

Oct 03, 2019
Da Schneib, my original point was that even if thousands of experiments support it, even if everywhere we've looked so far supports it, even if an enormous number of checks have been done, even if we've gotten the same answers, and even if there's no major contender for replacing the theory... IT CAN STILL BE WRONG!!!


For example, Newtonian physics, which was believed to be Absolute Truth by virtually everyone--- until Einstein.

Oct 03, 2019
"Is it still possible to extract energy even from empty space?"

What a stupid way to put it. The author appears to be stuck in the 19th century. If space is empty, then obviously the answer is no. But if energy is extracted, then obviously it's not empty. I'm just a humble crank, but it's my understanding that quantum physics posits an energetic "void" and that all matter is condensed energy exchanged from it. There is no place in the Universe that is "empty space."

Oct 03, 2019
Compressed space is Mass ... Compressed space is gravity.
The speed of light is a distance in space i.e


Your statements are completely meaningless.

You can't compress space. At least not locally. Can you tell me why that is true for local space and why it isn't true for extended regions of space?

While you cannot "compress" space, you can still move it...

Oct 03, 2019
Energy tied to mass is energy tied to gravity. If the gravity field is not a potential field but a vector field instead, then, for the moment here at least, the energy tied to mass is energy tied to a vector field. Vector fields are mathematically much richer in variety than potential fields. Electricity and electromagnetism are vector fields. Some people nonetheless prefer to visualize space or gravity effects through a curvature formed by a gravitational potential surface.

Oct 03, 2019
People say gravity is a tensor, seems they might as well be looking at a jello cube - gravity is causing it to compress vertically and spread out horizontally, viola - a tensor, vectors covering the top push things sideways. Surely that must be the trivial case from which to build everything, fill space with jello cubes of different densities maybe. Frame dragging seems to bring out the vector character of gravity a little, maybe it's just me. My point about vectors before is really a generalization of the "zero is relative" point of view and also kind of a reaction to trampoline-gravity fanatics.

Oct 03, 2019
There are vector fields and there are ultra-microscopic vector fields, my preference is for radiated ultra-microscopic vectors with one ultra-ultra-microscopic vector rotational rate when it comes to the force of gravity. Use E/G for protons as a starting point (meaning galaxy scale) for a fundamental full oscillation.
Mass should have a natural tendency to "reward" incoming gravity directions with outgoing gravity radiation, extended structures exploiting any delay in such a mutual-reinforcement type of effect would be encouraged, symmetric galaxy arms often give me that impression anyway.

Oct 03, 2019
"No amount of experimentation can ever prove me right; a single experiment can prove me wrong" - Einstein

...But your version, Da Schneib, is that Einstein has been proven right & that nothing can ever prove him wrong.

Seriously, the name Einstein is synonymous with GENIUS, so why the hell are you invoking it in the same sentence with DaSchitebo?

Oct 03, 2019
If you are speaking about negative gravity, does it mean that we would be capable of creating lift due to anti-gravity as per your research

Oct 03, 2019
While you cannot "compress" space, you can still move it...

So, you think that's space you're moving?...oh...wait...matrix flashback..

Oct 03, 2019
If you are speaking about negative gravity, does it mean that we would be capable of creating lift due to anti-gravity as per your research

Actually, gravity has only one opposite - none, regardless of the gravitational field strength. It is monopolar in its nature. No such thing as "anti" gravity. There IS such a thing as null (as in no or none) gravity, however.
"Lift" could be created using dipolarity nature of magnetic fields...

Oct 03, 2019
"Lift" could be created using dipolarity nature of magnetic fields...
It should be possible to warp spacetime such that you fall (accelerate) in the desired direction. One example that apparently requires exotic matter is the Alcubierre drive -- the wiki page has a good 2d visualization of what the spacetime curvature would look like, see https://en.wikipe...re_drive

Oct 03, 2019
FFS, I give up, why can't the education systems of the world teach the standard model properly ?
Thieving maggot cunts is why.

Oct 03, 2019
Since relativistic quantum field theory contains non-resonant excitations that are so called "off shell" in having mathematically imaginary mass - mislabeled "virtual particles" despite not showing the particle property of a definite mass - it is easy to think of them as having negative energies (as well as negative conditional likelihoods) to some extent.

The interesting generalization is that all theories that have laws (symmetries) can have it too. And the interesting find is that this property is maximized ("saturated") in flat space of LCDM-like cosmologies (i.e. with small cosmological constant), since the imposed constraints on symmetries are maximally relaxed. (The boundary conditions that a diffeomorphistic spacetime see has to be constrained for finiteness of solutions. I think. At that point the paper refers to the Hill equation https://en.wikipe...equation .)

Oct 03, 2019
It is about the potential energy contained in matter and has nothing to do with gravity.


LOL!

Potential energy is negative
Indeed it is, Bravo!
and the mass = E/C**2 determines in part the strength of the gravitational field associated with M.


Where in Einstein GR field equation do you see E=mc²

Rμν − ½Rgμν = (8πG/c⁴)Tμ
space-time curvature = stress from matter

Oct 03, 2019
So was all of the mass/energy in our universe "borrowed" from the vacuum during inflation in some manner that it couldn't be repaid, then?


The mass/energy of a flat (inflationary) eternal universe is zero, or it would be curved (and of finite time).

The potential energy of the inflation field dominates the internal energy of the universe except in the local universes such as ours. There the field ended and the energy instead went into radiation (dominated early) and (mostly dark) matter (dominated later) and a smidgen of remaining vacuum energy (dominates now).

Still amounts to zero - on average flat space - on scales larger than the local group, though.

So rather than energy borrowed I would say that it all balances out, because it has to: the universe is not "is not" but observationally it continues in all directions including time directions. It just is.

Oct 03, 2019
So to a rant, not entirely mine: :-)

Experiments merely "suggest" that it's true, ... Why is it that no matter the scientific topic, you treat current knowledge of the topic as gospel truth that will never be invalidated? You seem to be religious about science, quite frankly, and I find that awfully disturbing.


Da Schneib, my original point was that even if thousands of experiments support it, even if everywhere we've looked so far supports it, even if an enormous number of checks have been done, even if we've gotten the same answers, and even if there's no major contender for replacing the theory... IT CAN STILL BE WRONG!!! ... You need to have some damn humility and realise that we don't have all the answers and that it is arrogant to think that we do.


No amount of trials can ever prove anything. That's why science is a "never-ending" search for the truth.


- tbctd -

Oct 03, 2019
- ctd-

It is - painfully - clear that you don't understand science and scientists. No scientist claim that results are set in stone or can't be wrong. What we do know is that observational facts can be, routinely are, well tested beyond reasonable doubt and that when such robust theories are continuously improved on these facts are never overturned.

In the last quote you confuse that well tested property of science and reality with the fact that no experiment can show every fact at once, which is why science is never ending.

The idea that science can never achieve the quality of "robust beyond reasonable doubt, unlikely to be wrong" is AFAIK a philosophic/theological buffoonery put forward in the 18th century. Philosophers and theologians were both threatened, by not having achieved correct results respectively achieved wrong results for 3 [!] millenniums. While science had succeeded within a few centuries as the only known way to achieve knowledge. "It works." ;-)

- tbctd -

Oct 03, 2019
- ctd -

You talk of different things. Meanwhile I see hard working, humble scientists as experts on what they do. While I see arrogant do-nothing know-nothings complain about not getting it and about scientists being "arrogant".

And I also see that, despite we have a potential infinitude of detail to work out, science has succeeded in the last few decades to know 99.99 % of the general answer (standard particle physics and LCDM cosmology): "The Laws Underlying The Physics of Everyday Life Are Completely Understood ... But there's no question that the human goal of figuring out the basic rules by which the easily observable world works was one that was achieved once and for all in the twentieth century.

You might question the "once and for all" part of that formulation, but it's solid. Of course revolutions can always happen, but there's every reason to believe that our current understanding is complete within the everyday realm."

- tbctd -

Oct 03, 2019
- ctd -
[ http://blogs.disc...erstood/ ].

IT CAN STILL BE WRONG!!!

For example, Newtonian physics, which was believed to be Absolute Truth by virtually everyone--- until Einstein.

humble crank


Point in case. Cranks [now blocked by me] are never 'humble' since they opinionate based on nothing, against experts in the field (i.e. the scientists).

And no, Newtonian physics are still fact, we use it in rocket science (but not in electronics). What changed is that classical physicists thought that classical mechanics applied at every velocity or energy (or scale, re quantum field physics).

Oct 03, 2019
Thanks, @torbjorn. This is what happens when philosophy tries to pretend to be physics. Navel staring is supposed to trump real repeatable observations.

See the Sokal Affair.

Oct 06, 2019
What becomes of the photon's energy as it passes through the double slit and its waves, destructively interfere?

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