froeb

Alright fair enough, I'm not an expert on how those work. I was under the impression that there is quite a bit of work that has to be done to turn a path integral into something amenable to Monte Carlo though.

This is a pretty common misconception of path integrals from how Feynman explains them to a non-physicist audience. The path integral formulation cannot work from a particle-based approach, where you integrate over all possible trajectories of electrons, photons... . Instead, you are actually integrating over all possible configurations of fields, the electron field, the photon field... . As far as I know, there is no way to view the universe as being fundamentally made of particles that is compatible with our modern understanding of QFTs.

Also, the path integral really shouldn't be taken too literally. It's not reality, it's just an equation.

It isn't the only way. I would argue that the "sum over paths" is more of a convenient language for categorizing QFTs than an actual statement of physical reality. Path integrals have the benefit that they can be easily connected to correlation functions by a Wick rotation, are naturally invariant under relativity, and work (kinda) well with gauge theories (well better than any other way we know).

However, in practice they are not used directly. Instead, the path integral is either treated perturbatively giving you Feynman diagrams, or by working out the Hamiltonian prescription (probably closest to what you are thinking of), or by using Monte Carlo approaches (there are probably other approaches I don't know of too). All of these approaches are easier to calculate with, but are a less natural language for abstractly describing a QFT.

The textbook black hole is unphysical though, it assumes spacetime is asymptotically flat. As far as I can tell, the paper's claim is that if you do black holes more realistically, including better boundary conditions, then you can find solutions that have dark energy inside them, purely from GR. I wouldn't call that new physics exactly, I would call that a better understanding of physics we already have.

In physics at least, it's been my experience that even though the percentage of women physics professors is low, almost every one is an above-average researcher. They are certainly harder working on average. Meanwhile, there will be several men in the department who have just coasted. This isn't among new profs, but among those who have been around long enough that they definitely experienced gender discrimination in hiring. I don't think this is a biological thing, just an interesting side effect of strong gender discrimination, where the women who make it in have to be exceptional to do so.

Supernova simulations are especially interesting too. I have heard them described as the only time in physics when all 4 of the fundamental forces are important. The explosion can be quite finicky too. If I remember right, you can't get supernova to explode properly in 1D simulations, only in higher dimensions. This was a mystery until the realization that turbulence is necessary for supernova to trigger--there is no turbulent flow in 1D.

A lot of crazy sounding physics theories involve some non-trivial tweak to the laws of physics as we know them (e.g. the Alcubierre drive, many exotic dark matter theories, ...) so I usually dismiss them as unlikely. However, from what I have read about this so far, it seems to a natural consequence of black hole solutions in an expanding spacetime, no new physics needed. Am I missing something? If that's really the case, the odds of this being real are much higher than most typical hyped up physics fare. Would love an expert take.

Her criticism doesn't have much substance though, she says explicitly she can't follow one of the main arguments of the paper. I skimmed the paper myself, and it is quite esoteric, but it doesn't seem like nonsense to me. I wish she would react with more curiosity about it, and actually dig into it a little!

I took some time to skim the original paper and learned about cosmological coupling for the first time! My understanding is that black hole solutions in an expanding spacetime have way more freedom than the regular Kerr solution, because Birkhoff's theorem doesn't apply anymore. This means you can get time varying black hole solutions, one of which involves "cosmological coupling" where the mass of the black hole increases with the expansion of the universe.

I think this is just a possibility allowed by GR though, I think you would need a theory of quantum gravity to say whether such "cosmologically coupled" mass actually exists in a black hole.

I suppose this research group is claiming to have experimental evidence of it though? That is very interesting if true.

Also, I am not sure how you go from cosmological coupling to saying that black holes are the "source" of dark energy. I need to read further

This is a pretty confusing article. I think the conventional understanding is that dark energy is associated with empty space itself. Is this article discussing a proposed mechanism for dark energy, or an alternate explanation altogether? What is cosmological coupling, is that new physics or an emergent phenomenon from more realistic black hole solutions?