Ran across this article today.
Haven't read a copy of the actual paper yet but supposedly promising and re-normalizable.

https://www.aalto.fi/en/news/new-theory-of-gravity-brings-long-sought-theory-of-everything-a-crucial-step-closer

And the paper

https://iopscience.iop.org/article/10.1088/1361-6633/adc82e

Keeping my fingers crossed ...

Keeping my

Edited May 6May 6 by MigL

Very interesting. Thank you.

I remember having thought time ago something along the lines of "what if the honest-to-business symmetry group of GR is not as humongous as the group of all differentiable transformations of the coordinates, but something smaller and in a sense less unwieldy"? The diffeomorphisms would be a mathematical convenience, but the physical group, being rather about classes of valid systems of accelerated observers.

Not sure if the starting point of this proposal stems from a similar motivation, but it seems to go in a similar direction.

Seems to be re-normalizable for first order loops, and further work is needed to make sure infinities don't arise from higher order loops.
But even after establishing consistency of the mathematics, of course, there are predictions to test its viability, and since it reduces to standard GR at low energies/large separations, any tests will necessarily be at energies and separations we may not be able to reach.

Would be interesting to get @Markus Hanke take on this, as frankly, the maths involved are way above my pay scale.

10 hours ago, MigL said:

Would be interesting to get @Markus Hanke take on this, as frankly, the maths involved are way above my pay scale.

I think it’s an interesting approach, that may very well turn out to be quite viable. The huge advantage here is of course that this model directly integrates into the Standard Model, since it’s build on the same paradigm from the ground up.

The basic idea here is that you start with flat Minkowski spacetime, and then define a suitable gauge field on it that has the same degrees of freedom as ordinary GR, so that the observables cleanly map into each other. It turns out that this works if you use a collection of spinors as the fundamental mathematical object. You can then simply apply all the well established techniques of quantisation and renormalisation, since we’re just working with a field on ordinary Minkowski space. The authors have shown that the resulting model is renormalisable to first order, which is a great start. Much of the technical details are kind of over my head too, but I get the main ideas, and I think it’s very promising. I don’t see any obvious reason why the renormalisation shouldn’t work to higher orders too, but we’ll have to see.

It’s also interesting to note that this model contains no new free parameters, it works entirely with already known fundamental constants.

Just out of interest, how would this knowledge benefit our society?

14 hours ago, dimreepr said:

Just out of interest, how would this knowledge benefit our society?

The job of physics is exclusively to develop descriptive models of aspects of how the universe works on a fundamental level - it is simply about knowledge and understanding. What people do with this knowledge is a whole different question, which lies outside the domain of physics itself. For example, quantum physics has given us the MRI machine at your local hospital, but also the nuclear bomb.

As for the specific model on this thread, it’s too early to ask about potential implications, because no final fully renormalised version exists yet. Only once the mathematical groundwork has been done, can we judge whether this is worth investigating further, and what the model actually tells us about the world, if anything.

7 hours ago, Markus Hanke said:

The job of physics is exclusively to develop descriptive models of aspects of how the universe works on a fundamental level - it is simply about knowledge and understanding. What people do with this knowledge is a whole different question, which lies outside the domain of physics itself. For example, quantum physics has given us the MRI machine at your local hospital, but also the nuclear bomb.

As for the specific model on this thread, it’s too early to ask about potential implications, because no final fully renormalised version exists yet. Only once the mathematical groundwork has been done, can we judge whether this is worth investigating further, and what the model actually tells us about the world, if anything.

Thank you, for both, not assuming it was anything other than a genuine question and your answer. +1