# White holes as dark energy? [closed]

I apologise right away for the possibly incompetent question, but I am not a physicist, and this just came to my mind without really thinking much about it.

On one hand we struggle to find white holes which should be spitting out energy and on the other hand we have dark energy that can be imagined as space-time being fabricated everywhere in space (is that even true?). Could it be that there is a connection between the two? What if there is only one white hole (the whole universe), but it is too large to be white? Do we have a measurement of all the energy falling into all the black holes in the universe to compare it to the amount of dark energy?

• The formulas describing the white holes look very different as the formulas describing the Universe. But these are very theoretic things (i.e. nobody has seen a single white hole until now, probably they don't exist), thus maybe. Anyways, thinking on these is surely a good idea :-) I hope you get a good answer. Jul 30, 2016 at 7:29
• Here is a quite similar question. Here was asked, if we are in a black hole. Jul 30, 2016 at 8:00
• We don't know what dark energy is. That's a simple fact. It has a fairly homogenous distribution and a volume density on the order of 1J/km^2, if I am not mistaken. White holes would be compact objects that would be producing matter, not dark energy and they should probably be visible, if they were around. Jul 30, 2016 at 8:06
• It could also be mentioned that dark energy is thought to cause the expansion of the universe...it's already got a job. =) Jul 30, 2016 at 13:20
• black hole vs dark energy : think about the magnitudes. The whole ordinary matter is 13 to 15 times less than the dark energy and it includes the black holes.
– user46925
Jul 30, 2016 at 17:35

The question has a funny subtle level to it that probably escapes most. White holes as huge fountains of radiation or fields, inverses of black holes, probably do not exist. However, the white hole has a certain subtle meaning with respect to the quantum mechanics of black holes, in particular with Hawking radiation. This also connects ultimately with the quantum vacuum which plays the role of a constant energy density responsible for the accelerated expansion of the universe. The details and fundamental understanding of this are as yet unknown, but we can probably say with some confidence that dark energy is quantum zero point energy.

Before we charge into this question we need to be sure we understand what a white hole is. The Penrose conformal diagram for the Schwarzschild solution is shown below

There are four regions, where regions I and II correspond to timelike region in the exterior universe, and regions III and IV correspond to the black hole and while hole. The horizontal lines at the top and bottom are the singularity of the black hole and white hole. The $45^o$ lines are the event horizons of the black hole. If Bob were sitting in region I then he would observer quantum particles entering his region I from region IV and conversely quantum fields approaching the event horizon separating region I from III. Hence quantum fields are gushing out of region IV into I and then falling back into region III. The Eddington-Finkelstein diagram for the black hole below

pertains to a black holes with charge, but genetically the difference between region III and IV is that region IV is with this diagram upside down. The future light cones become past light cones.

The diagram illustrates in effect region I and II as having black holes that are completely entangled. The two $45^o$ angled lines are event horizons that separate these exterior regions from the entangled black holes. Quantum entanglement is however funny. If you have two quantum particles with spin states ${|\pm\rangle}$ the entangled singlet states formed from them is $$|\psi\rangle~=~\frac{1}{\sqrt 2}\left(|+,-\rangle~+~e^{i\phi}|-,~+\rangle\right)$$ The quantum mechanics of this is that this state is what is knowable, but absent some measurement that demolishes this entanglement the individual spin states are not knowable, or in fact simply do not exist. With entangled black holes it is similar. The region III is really less of a black hole and more of an entanglement between two black holes.

Ideally we may be able to make such entangled black holes, but preparing a vast number of entangled states that are then as pair collected in different regions of space. If these sets of EPR pairs are massive enough, say with large $N$ number of particles, they will form two entangled black holes. This may sound very idealized, and in some way it is. However, within a multiverse setting it is possible that black holes form in one region of space with quantum states that are entangled with pairs that enter black holes elsewhere.

Physically the Penrose diagrams above is somewhat problematic. First off there have been no white holes identified, at least as far as we can understand. In fact it has been common to think of the truncated diagram such as that below

This diagram cuts off the black hole at the moment Hawking radiation has converted it completely into radiation. This is a classical representation, or classical in that the black hole has no quantum entanglement properties.

Returning to the Penrose diagram at the top, I have drawn in a red circle at the origin. This represents a quantum fluctuation, or a loop. From the perspective of the observer in region I on one of the stationary radial lines this particle emerges from region IV across the horizon, rises up and then falls back down to approach the horizon. The observer in region II observes much the same, a particle crosses the horizon bounding region IV, rises up and then falls back to the black hole bounding region III. This loop intersects spatial regions, or regions of constant distance from the horizon. The diagram below is a nonconformal diagram, but the "spokes" of this are spatial regions of constant time, and the loop intersects them all

Assume this loop is at a distance $\rho$ from the origin. The near horizon condition has the metric $$ds^2~=~\rho^2dt^2~-~d\rho^2~-~dy^2~-~dz^2$$ such that the acceleration with $\rho~-~1/g$. The loop then have a propagator $$\langle\phi_1|e^{-2\pi/g}|\phi_2\rangle.$$ The argument in the exponent with units restored is $-2\pi\hbar c/g$. From this we can derive Unruh-Hawking radiation where the acceleration $g~\sim~T$ the temperature.

The white hole is then a sort of classical signature that general relativity has some quantum underlying meaning. It is possible that quantum mechanics and general relativity are in fact the same thing. If we return to the diagram at the top, there are two curved blue lines and two red dots connected by a bar. This represents Hawking radiation, where the observer in region I or region II has measured this loop as a real quantum particle. These particles in region I and II are entangled pairs. In addition, since these have mass it means the focusing of light by gravitation is such that the event horizons in region I and II are no longer coincident. Some part of the entanglement of the black holes has been replaced by entanglements of particles in region I and II. Again the blue lines illustrate that the horizon has shifted slightly, and this could be argued to be due to gravitational lensing of this exterior mass that reduces the area of the black holes horizons in regions I and II that separate off region III. We may think of this is a bit of a "white hole" from the black hole, and the white hole is then a gadget that shifts entanglement from black holes to radiation in the exterior.

• Amazing answer. I assume what you're saying is true and correct or, at least, on the right track. But I will live the entire remainder of my life, however long that may be, and never have a hope of understanding it. Jul 31, 2016 at 1:14
• I was going to expand into anti-de Sitter spacetimes, but realized this was getting a bit long. Look up Susskind's paper on ER=EPR. Jul 31, 2016 at 1:55
• Nice answer! But where are all the white holes? Well I have a suggestion, and I have made a long list of observational evidence that makes the suggested proposal pretty strong, and I can't find any observations which goes against it, and neither can others: physics.stackexchange.com/questions/207317/… Now I wonder if we put a black-white hole supermassive binary in the GC, like a Penrose diagram, could this explain both pulling dark matter and pushing dark energy? Acting by something like quantum/multidimensional force(s)? Oct 25, 2016 at 12:56
• And the suggestion above also give a fascinating possibility to the shape of the universe which wraps it all up and balances energy and momentum across time and space. It do require circular time on a large scale, and have problems with a Big Bang, but white holes make such problems anyway. It is a Moebius strip shape, with a lot of galaxies on the strip, and white hole black hole binaries in galactic centers go through the strip to the same galaxy as far away in time or space as the size of the universe allows. This model allows GC counter flowing wormhole binaries to be balanced and stable. Oct 25, 2016 at 13:45

A quick answer to the only question in your post that we have evidence for.

Do we have a measurement of all the energy falling into all the black holes in the universe to compare it to the amount of dark energy?

No, as we can't see the entire universe, as answered in Observable Universe by DilithiumMatrix:

There's lots of additional universe out there that we can't see, and we'll never be able to. In fact, because of expansion, more and more of the visible universe is actually leaving the region which we can see, which is called our 'light-cone'.

As CuriousOne says, it could be that, the so far unobserved white holes would be compact objects that would be producing matter, not dark energy. We have no evidence for them, or what they emit.

Finally, a white hole couldn't fill up the universe with an unlimited amount of energy/matter, it couldn't release anymore than the energy equivalent of it's inital mass. So unless there a cyclic aspect to the universe, (again, we don't know, although Roger Penrose has his own speculative ideas in his book Cycles Of Time ), the universe could not emerge from a white hole.