Heck, as a physicist let me clue you in: most physicists simply use single words or short phrases to describe a whole vague bunch of related concepts. What the hell is “entanglement”. Oh my if physicists from two different subfields would try to unpack each others conception they would spend a whole day arguing like those old theologians about the nature of the Holy Ghost. Another is the interchangeable usage of “Lie groups” and “Lie algebra.” It helps, I guess, to realize that these words are actually labels for certain heuristics or sequences of mathematical operations. They work more or less when everyone is taught to use the same techniques but a farce when squeezed for puns.. not looking forward to the emergence of “hair loss” in both professional and journalistic black hole discourse— and yes, another religious term, “emergence”. Bastards.
> most physicists simply use single words or short phrases to describe a whole vague bunch of related concepts. What the hell is “entanglement”.
Actually, "entanglement" has a precise meaning in QM (a state that cannot be expressed as a product of states of subsystems). It's just that that precise meaning won't make any sense to someone who hasn't already learned a fair bit of QM, so when asked to define the term by lay people, physicists have to wave their hands.
To quote:
“The crux of the problem lies in an assumption about the structure of entanglement across the event horizon, namely, that the Hilbert space factorizes. While valid in quantum mechanics, this fails drastically in quantum field theory”
https://arxiv.org/abs/1901.01149
> not looking forward to the emergence of "hair loss" in ... professional ... black hole discourse
That horse bolted from the barn so long ago that the door has rotted away.
The process of black hole "hair loss" has been in the jargon with "balding" for decades. Google scholar will find you baldness/bald/balding with respect to black holes in publications from the 1970s, and I would be far from surprised to find that Werner Israel has the first published use of the exact words "hair loss" in the mid 1960s in a paper on electrovacuum spacetimes.
Hair loss is an important feature of the dynamical spacetime around a black hole, and takes place on timescales of approximately the light-crossing time of the event horizon diameter. Can balding encode the difference between one (classical) shell of test matter of mass M dropped into a black hole versus two shells of 1/2 M each? Good question! Can balding encode quantum numbers? Also good question! These are questions which go back to the early 1970s: https://journals.aps.org/prd/abstract/10.1103/PhysRevD.5.243...
(Hair loss continues to an area of current active research. A random recent paper: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.12... preprint <https://arxiv.org/abs/2109.14620v1>, "... In vacuum non-zero ∇ × (αB) is quickly radiated away or swallowed by the BH (α is the lapse). However, when plasma is present nonzero ∇ × (αB) drives currents which slows down the balding process.")
Emergence seems far from religious, at least as far as I understand the context of your complaint. If you can derive theory B from theory A, B emerges from A. If, for the same theories, you cannot derive A from B, then A is the more fundamental. That's all that's meant, at least in the basement foundations of theoretical physics, in the weak field limit of quantum gravity theories, and likely most places where one must deal in effective theories. I'm sure you know this, as a physicist. I can't speak to how the term might or might not be used in theology.
I do take your point though that physicists from different areas of physics, and of course mathematicians, might not use a jargon word in the same way. Emergence might be one of those, for all I know.
Emergence is widely used to describe the behaviour of complex systems that you would have a hard time to guess from first principles. One simple example would be convection cells. (Note how "hard time to guess" is quite subjective as criteria go.)
Yea, “religious” in the context of physics means, for me at least, more like “metaphysical” (with a nod to Brian Green & a caveat that nowhere near a professional unnatural philosopher am I). Should I say metatheoretical? As you both reveal, we have already here from 2 fields of physics each an equally promising definite sounding but potentially hairy (even divergent) description of ”emergence”. One seemingly about logic and the other about ..computational complexity(?)
Thanks for the hair loss tip! Have been glancing thru the recent lit (admittedly thanks to the quantacoverage)—- it was all “no-hair” and no “hair-loss”. Seems like the term “hair loss” went out of fashion before i was born?
Might be not so divergent if this emergence of new theories is in any way "surprising".
Potentially related : the concept of "surprisal", and how entropy is a superfluous concept - since it's just the lack of information that an observer has about a system.
