# Could dark energy be emitted by black holes? [closed]

I'm a total amateur so please ignore any blatant ignorance that follows.

We don't understand the physics of circumstances within a black hole and we cannot observe dark energy or dark matter but only infer their presence. Might it be possible that black holes could 'recycle' absorbed matter-energy by emitting dark energy?

The amount of non-primordial black holes in the universe has increased over time and the amount of dark energy as a percentage of total energy in the universe, has also increased over time. Ok, so my waistline has also increased over time, but I'm just thinking out loud: We have dark energy, dark matter and black holes themselves are also......well,....dark.

What properties would an emitted dark energy need to have to end up residing uniformly in the vacuum of space?

I know they say there's no such thing as a stupid question but apologies if I've offended anyone!

## closed as unclear what you're asking by ACuriousMind♦, Jon Custer, user36790, John Rennie, honeste_vivereSep 13 '16 at 12:56

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• Disclaimer: I am no expert. We don't know what dark energy is so anything's possible, but we would expect black holes to show some effect if they did emit dark energy and as far as I know, we haven't seen anything different/obvious. But it's black holes and dark energy, amongst the things we know least about, so.....I wouldn't worry about offending anyone, it's a hypothesis that might have some validity in my personal (decidedly non expert) opinion. It's finding proof, that's the part that's a tad difficult to obtain. – user108787 Sep 11 '16 at 23:14
• in simulation, dark matter is needed to constitute galaxies ( and clusters ) with a ratio greater than one can expect from the BH outputs. Now, all is possible. Basic datas being ready to download, it is possible to test such idea if you have a powerful computer network. – user46925 Sep 12 '16 at 14:11
• VtC: 1) I think it is not a bad question 2) Maybe a "we don't know, there isn't any sign of it" is also an acceptable answer (if it is correct). See @CountTo10's comment before. – peterh Sep 12 '16 at 14:58

To start off the observations of the accelerated expansion of the universe so far demonstrates that dark energy is homogeneous in space. There do not appear to be local regions where it is accumulated. Dark energy most likely is a manifestation of the quantum vacuum. For a quantum zero point energy density $\rho$ the FLRW energy condition for a flat space is $$\left(\frac{\dot a}{a}\right)^2~=~\frac{8\pi G\rho}{3c^2},$$ where the cosmological constant is $\Lambda~=~\frac{8\pi G\rho}{3}$. Now one might then question whether black holes might then pull in quantum vacuum energy and grow in mass. This would appear to be a conundrum but for the $w~=~-1$ condition with $\rho~=~wpc$, for $p$ the pressure, this means there is a negative pressure term. So for energy taken into the black hole from the vacuum there is a corresponding "negative work" from the pressure that is opposite. In that way black holes do not grow endlessly by devouring the quantum vacuum.
The generation of quantum vacuum energy would occur for $w~<~-1$, which is the big rip scenario. I wrote this post on physics Stack Exchange on the big rip if you want to read on this further. This situation would be strange with respect to black holes. In the big rip the vacuum energy keeps increasing, thus driving the accelerated expansion far more. This would mean the black holes perform more negative work than the vacuum energy they absorb and so would decrease in mass.
The case $w~=~-1$ is special and suits physics best as far as can be seen. So far the data is pretty close to this. As a result it is unlikely that black holes generate dark energy or convert their mass into such by absorbing negative pressure that is greater than the vacuum energy they absorb.