Thursday, May 26, 2016

How can we test quantum gravity?












[From arXiv:1602.07539, for details, see here]







[This post previously appeared on Starts With A Bang.]


Uncle Al said...

"That’s another 16 orders of magnitude to go." 60 MHz (5 meters) NMR views femtometer nuclei. 2-D airplane wings are Bernoulli effect, planes fly inverted; footnotes! Gravitational radiation is not observed to be quantized or diffractive.

Vacuum may lack an exact symmetry. Lorentz invariance removes baryogenesis. An exact postulate isn't. Test geometric vacuum chiral symmetry breaking six different ways, all arising outside physics. Observe an empirical answer.

Spacetime is exactly mirror symmetric toward massless boson photons: no vacuum refraction, dispersion, dissipation, dichroism, or gyrotropy in the lab and across the universe. Gravitation requires hadronic matter tests.

piein skee said...


In fact the correct lesson to takeaway - because it's the only invariant component across all instances - is that whether forbears imagined it was impossible, or that it wasn't, the terms on which they envisaged were completely naïve and inadequate and did not begin to approach the scientifically resolved object, or anything at all usefully accurate about the future.

This really is every single instance. Not just corresponding to predicting future developments in technology, but also in abstract theory. See if you can think of an instance in which something was envisaged that it must be there, and it must be like this or like that, such that designing tests became feasible.

See if you can think of a an instance, because I can't. It's obviously easy to suppose all kinds of instances, but that's just because context is hard correspondingly hard. It is easy I think to demonstrate why a given instance is illegitimate, either due to being out-of-context, or being an artefact of some other kind. So it's worth having a go.

Needless to say, there are stark implications for quantum gravity as currently conceptualized. I think you'd have to take account if the measure of optimism from weighing the balance of things, is to have real world usefulness

akidbelle said...

Hi Sabine,

I understand that all this is based on the assumption that the existing physico-mathematical framework is fundamental (QM, QFT, gauge fields, whatever is on the scene at a given epoch) and therefore the same framework also applies to gravitation. Is that so?

If not fundamental, what would that mean for gravitation?
(Second question, related to your previous post, what would that mean about crackpots filtering?)


Sabine Hossenfelder said...


No, it certainly does not mean that. OFT, gauge fields and so on might be fundamental, but most people in the field believe they are "emergent" in a low-energy limit. Actually, the question what is fundamental and what isn't can be difficult to even answer if you have dualities. (I wrote about this here.)

Uncle Al said...

@piein skee Fundamental science usually begins as anomalous observation or "unsound" imaginings. Baryogenesis happened. That is where you begin - by allowing(demanding!) it. Elegantly derived quantum gravitations to the contrary are empirically sterile.

akidbelle said...

Dear Sabine,

thanks; I read the post in reference, but the question it raises can only be tested on humans - and maybe duality actually test humans (just our love for concepts).

The question I had is almost equivalent to saying "can we have gravitation and QFT/gauge fields without a graviton". I mean why would the "thing that carries gravitation" be a particle? (A particle being the consequence of a framework, or at least of interpretation/understanding of it.) Why would everything that exists be either a particle (or a field), or space and curvature?


piein skee said...

Hi Uncle Al - I think I agree with you but it's hard to tell. I'd like to hear more if you're willing.

Uncle Al said...

This is Bee's party, quantum gravitation, I'm an organic chemist. General relativity? Newton terrifically fails (SR, GR; QM, Stat Mech.: c; h, k_B). A rigorously derived axiomatic system can fail as science for a postulate not being empirically complete.

After 45 years of astounding effort, gravitation resists quantization. What solution is excluded from physics? Vacuum is mirror symmetric (Noether's theorems, spatial isotropy, conservation of angular momentum). Baryogenesis, the Weak interaction, and many other things demand added mirror-asymmetry. A footnote exists.

Chemistry offers novel chiral tests carefully excluded from physics. Look anyway. The Varian brothers' klystron may bear upon hostile peer review until reduction to practice. Look up "clyster." Kary Mullis was Nobel Prize/Chemistry for driving up a switchback mountain road while stoned. It was...DNA, and he was a zipper.

akidbelle said...

Hi Uncle Al,

Newton does not fail so much; just assume the potential at the infinite is c^2 and modify the Compton wavelength according to the local potential. You get the Schwarzshild metric - the only thing tested in GRT. So it may be possible to unify QM and gravity, but for this one can either assume a curvature or try to understand what energy is - which is heresy!

The vacuum is mirror symmetric only if considered independent of its content - which is necessarily sterile if one tries to unify some things...


piein skee said...

Hi Uncle Al - Newton did not fail to see the character of relativism. He explored it extensively and realized it was impossible to get to the bottom sufficiciently for any hope of finalizing a self-consistent theory in his lifetime. In fact there is now a large body of historical fact that supports his intuition. Not only was relativism not available from 17th century knowledge, but it would not ever have become available were it not for the scientific revolution including engineering and technology. And that would not have been possible without Newton's theory.

There are a number of bogus charges levelled at Newton at the moment. You suggest he failed Relativism, when his theory was necessary to derive it. His theory has not been disproven, it has been bounded, it's limits identified precisely. That is the highest possible standard a scientific can attain. It's when the term 'true' becomes legitimate. True within a bound.

I've been aware of your chirality related apparent belief that there is information available there that physicists need to know about. You are very persistent, but you also obscure through language what precisely you think people should do and why.

I've speculated what could be driving the apparent contradiction in play there. I think it's possibly that you have worked hard for what may be important discoveries, but that for whatever reason you do not wish to progress yourself, but you are torn between a desire for your knowledge be put to good use on the one hand, while on the other an understandable reluctance to give away to others what you had to work for.
If that's it, then my council would be that semi-hinting encased in a linguistic tactic of obscuration, is not a good compromise. Unless you really can't bear to let others have your knowledge and probably take credit, but cannot bear to never speak of it. If that's the balance and your ultimate goal is to mention it but keep it for yourself, then your strategy is excellent. Because no one is picking up, and it's been quite a long time :o)

Robin Morrison said...

IT would be too cool if on the way down, we found some intermediate form of energy/particle small enough to see PLanck objects. Like Feynman said in a different context, There's PLenty of Room at the Bottom.