Gravity: We might have been getting it wrong this whole time

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From Phys.org:

https://phys.org/news/2020-01-gravity-wrong.html

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[notFritzArgelander]

It's remarkable how innocent of content this article is. Might have to dig a little more.... Thanks in any case.

[smp]

It's remarkable how innocent of content this article is. Might have to dig a little more.... Thanks in any case.

Thanks, nFA. I was afraid of that. A reputable source, so I thought it was worth a look.

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[notFritzArgelander]

It's remarkable how innocent of content this article is. Might have to dig a little more.... Thanks in any case.

Thanks, nFA. I was afraid of that. A reputable source, so I thought it was worth a look.

smp

I have a vague recollection of an older post on this work here or back at the "old sod". I'll refresh memory before commenting.

[notFritzArgelander]

Well, a trip down memory lane for sure.

The older article pn phys.org rang bells and is much more informative:

https://phys.org/news/2019-05-constrain ... raphy.html

A pair of researchers, one at the Massachusetts Institute of Technology (MIT) and another at California Institute of Technology (Caltech) and the University of Tokyo, have recently investigated a set of old conjectures about symmetries in quantum gravity. The specific conjectures of focus: (1) Quantum gravity does not allow for global symmetries; (2) For gauge symmetry, all possible charges must be realized; (3) Internal gauge groups must be compact. Their paper, published in Physical Review Letters, shows that these old assumptions hold within the anti-de Sitter/conformal field theory (AdS-CFT) correspondence.

Translation of (3): the field theories of interest have a locally adjustable gauge which gives rise to gauge bosons when quantized like photons in EM, the W and Z bosons in weak fields, and gluons in the strong interaction, gravitons in gravity. (I'll buy that.)

Translation of (2): all permitted charges must exist. Skepticism starts here. It's a problematic assertion. EM permits magnetic monopoles yet the duality symmetry of Maxwell's equations permit us to choose EM units such that magnetic monopoles are transformed away. Now magnetic monopoles would be nice to exist in some form that isn't eliminatable by our choice of units. Then charge quantization would be easy to show as per Dirac. But so for no one's found one! Caveat: "there need be only one". (Nod to Highlander there. )

Translation of (1): is easy, there are no global symmetries in QGravity. It is the claimed result. The main issue is that they prove all this inside the framework of the AdS/CFT.

https://en.wikipedia.org/wiki/AdS/CFT_correspondence

Now I am warm to the idea of the AdS/CFT correspondence, it enabled the first experimental use of string theory in interpreting quark-gluon plasma results at RHIC. However I don't swallow it entire since the universe we live in is NOT an AdS universe. An AdS space has constant negative curvature. Flat universe is not the same as one of constant negative curvature.

Anyway previous discussion can be found on TSS at

viewtopic.php?f=74&t=1438

and at viewtopic.php?f=74&t=2122&p=17986&hilit ... CFT#p17986

BTW I checked at AF and there's nothing there that's relevant.

[notFritzArgelander]

If you follow the links to the previous discussions on TSS you'll find some additional material that casts further doubt on the value of this work.

The researchers do not believe in conservation of energy in GR. This is a widespread error that many workers in GR and cosmology make. Erwin Schrödinger introduced this error into the physics community and folks like Ethan Siegel and company persist. They insist wrongly that energy-momentum must be a tensor. But the Landau-Lifschitz pseudotensor is widely recognized by folks as "good enough". It's certainly better than Einstein's pseudotensor.

https://en.m.wikipedia.org/wiki/Stress% ... eudotensor

Anyway, without global symmetries, including conservation of energy-momentum, Noether's Theorem is lost and physics is dead.