Following on from my own reasons to reject the claimed BH-DE linkage, two recent arXiv articles support that, but from very different perspectives:
Observational evidence against the supposed BH-DE 'connection':
https://arxiv.org/abs/2302.12386
[Submitted on 24 Feb 2023]
Constraints on the Cosmological Coupling of Black Holes from the Globular Cluster NGC 3201
Carl L. Rodriguez
Globular clusters are among the oldest stellar populations in the Milky Way; consequently, they also host some of the oldest known stellar-mass black holes, providing insight into black hole formation and evolution in the early (z≳2) Universe. Recent observations of supermassive black holes in elliptical galaxies have been invoked to suggest the possibility of a cosmological coupling between astrophysical black holes and the surrounding expanding Universe, offering a mechanism for black holes to grow over cosmic time, and potentially explaining the origin of dark energy. In this paper, I show that the mass functions of the two radial velocity black hole candidates in NGC 3201 place strong constraints on the cosmologically-coupled growth of black holes. In particular, the amount of coupling required to explain the origin of dark energy would either require both NGC 3201 black holes to be nearly face on (a configuration with probability of at most 10^−4) or one of the BHs would need to have formed with a mass below that of the most massive neutron stars (2.2M⊙). This emphasizes that these and other detached black hole-star binaries can serve not only as laboratories for compact object and binary astrophysics, but as constraints on the long-term evolution of astrophysical black holes.
Theoretical Rebuttal of a fundamental common sense nature:
https://arxiv.org/abs/2302.13333
[Submitted on 26 Feb 2023]
Can black holes be a source of dark energy?
S L Parnovsky
The hypothesis that the mass of BHs increases with time according to the same law as the volume of the part of the Universe containing it and therefore the population of BHs is similar to dark energy in its action was recently proposed. We demonstrate the reasons why it cannot be accepted, even if all the assumptions on which this hypothesis is based are considered true......
Can black holes be a source of dark energy? 4 Both MBH and the volume of this part increase proportionally to a^3. Therefore, the MBH density does not change with time. But this is not enough to ensure the properties of DE. It is also necessary to have a negative pressure with the equation of state (EoS) P = −ρ (it corresponds to the cosmological constant) or close to it. Here P is the pressure and ρ is the density of mass and energy (in units with c = 1). In the first case, the constancy of ρ and P is provided automatically if we proceed from the fact that DE cannot be transformed into something else and vice versa.
Within GR, both gravitational attraction and repulsion are possible. Everything is determined by the sign of the combination ρ + 3P. For ordinary matter, it is positive and attraction occurs. For the case of the cosmological constant or the more general case of DE, it is negative. This corresponds to gravitational repulsion or anti-gravity, which ensures the accelerated expansion of the Universe.
The black hole system does not have negative pressure. Therefore, it does not provide anti-gravity and accelerated expansion. It cannot be considered as something that works as an analogue of DE. Moreover, at present, the influence of DE prevails in the cosmological expansion, while the mass of black holes is a very small fraction of the mass of everything that fills our Universe.....
There is no mention in the article (Farrah et al, 2023a) of the reasons why the authors came to the conclusion that the BH population has a negative pressure, and it is huge in absolute value. Indeed, without the fulfillment of condition ρ + 3P < 0 there will be no antigravity and, accordingly, no accelerated expansion. Standard concept of the properties of black holes rule out this possibility.
Even if we assume that our knowledge of the BH properties will change significantly in the future, they are unlikely to include negative pressure. The reason is simple. Black holes do not uniformly fill the entire space, but are concentrated into small objects. Even if they would have a negative pressure capable of providing anti-gravity, then the gravitational repulsion would be observed primarily in the region around the black hole. In this case, instead of accretion of matter from the surrounding space onto the BH, we would observe its expansion, dispersion, or flying apart, which contradicts the astronomical observations.
Feb 23, 2023 02:34 AM
