Reuter(Loops 07) no inflaton needed, no horizon problem

[Martin]

One of the most important talks at Loops 07 last month.

 

doesnt need to put in einstein-hilbert action, gets it out as a prediction

see page 12

 

background independent, page 12

 

gets inflation in early universe without inflaton (no fine tune, no exotics) page 16

 

gets scale invariant fluctuations in largescale structure as observed in CMB for free without fine tune, see page 28

 

REUTER. he has a minimalist direct quantization of Gen Rel

no extra dimensions, no exra NOTHING

where we used to think it was non-renormalizable

and where Weinberg TRIED to prove it was asymptotically safe but failed in 4D case, Reuter has succeeded in showing asymptotic safety

 

he does this by understanding the renormalization group flow (varying G and Lambda) better than his predecessors and finding a non-gauss fixed point,

that was 1998, a bunch of people have been verifying it since then checking and rechecking---and in the last few years Reuter has been applying it to cosmology.

 

Lots of interesting results.

 

Reuter's talk is stand-alone. So if you want to follow only one talk from Loops 07----the big international LQG conference that happened last month---I would recommend that one. Reuter epitomizes the aims and mindset of the LQG community----no-frills direct quantization of Gen Rel, background independent of course---his approach is only one of halfadozen similarly motivated approaches that are being pursued---for me it exemplifies the common shared features.

 

dowload the slides PDF first and get ready to scroll thru them in synch with the talk---then click on the audio

the following list is alphabetical so you can easily find Reuter slides and audio links here:

http://www.matmor.unam.mx/eventos/loops07/plen_abs.html

 

slides:

http://www.matmor.unam.mx/eventos/loops07/talks/PL3/Reuter.pdf

 

audio:

http://www.matmor.unam.mx/eventos/loops07/talks/PL3/Reuter.mp3

 

===

 

===============

out of curiosity I checked Reuter's citation trackrecord and found 5 paper that were 100+ cites

and 17 papers that were 50+ cites

 

FIND A REUTER, MARTIN AND AFF DESY AND TOPCITE 50+

http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+A+REUTER%2C+MARTIN+AND+AFF+DESY++and+Topcite+50%2B&FORMAT=www&SEQUENCE=citecount%28d%29

FIND A REUTER, MARTIN AND AFF CERN AND TOPCITE 50+

http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+A+REUTER%2C+MARTIN+AND+aff+CERn+AND+TOPCITE+50%2B&FORMAT=www&SEQUENCE=citecount%28d%29

FIND A REUTER, MARTIN AND AFF MAINZ U., INST. PHYS. AND TOPCITE 50+

http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+A+REUTER%2C+MARTIN+AND+AFF+MAINZ+U.%2C+INST.+PHYS.+AND+TOPCITE+50%2B&FORMAT=www&SEQUENCE=citecount%28d%29

FIND A REUTER, MARTIN AND AFF HANNOVER U. AND TOPCITE 50+

[Reaper]

Very interesting.

 

I have a few questions though. First, understand that a lot of this is over my head, so don't be surprised if I ask what might seem to be "basic questions".

 

1. Why the need for a non-perturbative solution?

 

2. On page 13, it mentions that gravity doesn't have to be unified with the other 3 fundamental forces. If that is so, then what does that imply for GUT? It seems to me that this implies that when the Big Bang occurred, the Universe wasn't in perfect symmetry to begin with.

 

3. Can you explain the RG Trajectory please? (page 14)

 

Those are my questions so far. I'm going to keep re-reading it to see if I can understand it better.

 

Very interesting read, and its nice to see that there are serious alternatives to String Theory!

[Martin]

Very interesting.

 

I have a few questions though. First, understand that a lot of this is over my head, so don't be surprised if I ask what might seem to be "basic questions".

Thanks for your response, Lockheed! It helps when you ask questions. the more basic the better. helps get me thinking. also simple comments help.

 

I just listened to Ambjorn's talk at the same conference. It turns out that Ambjorn's simplicial path-integral approach (uses computer to generate random spacetimes out of tetrahedron-like building blocks) is COMPATIBLE with Reuter Assymptotically Safe approach. Reuter supplies the context or framework in which Ambjorn says his path-integral should be understood.

They each referenced the other's talk.

1. Why the need for a non-perturbative solution?

 

First off, I think that Reuter's approach can be applied to perturbative calculations around flat Minkowski space. I think his approach has the potential to be BOTH perturbative and non.

 

Perturbative calculations are what everything runs on so this is a good question. Why ever bother to work out the non-perturbative version of a theory?

 

I will take a shot at that and say that one of the goals of quantum gravity is to resolve the breakdowns and failures (SINGULARITIES) of classical gen rel.

If you want to apply your theory to the pit of a black hole or right around the big bang then you need it to be nonperturb. Because perturb is best when the geometry is approximately flat. It isnt so good where there are violent extremes of curvature.

 

2. On page 13, it mentions that gravity doesn't have to be unified with the other 3 fundamental forces. If that is so, then what does that imply for GUT? It seems to me that this implies that when the Big Bang occurred, the Universe wasn't in perfect symmetry to begin with.

 

I don't know how to interpret the implications for GUT. Maybe you can find out. He has graphs showing the RUNNING OF NEWTON'S CONSTANT and you can read off a value for the BARE newton's constant. I havent done this but it might be interesting to see how it stacks up compared with the other 3 forces! Look at the values he has for G and for the cosmological constant Lambda (or their dimensionless versions little g and little lambda) at or near the nongaussian fixedpoint of the flow.

 

3. Can you explain the RG Trajectory please? (page 14)

 

Are you listening to Reuter's audio when he talks about the RG?

I have listened over again several times.

Getting a better grasp is going to take work. he cites some papers and gives arxiv numbers.

 

Keep asking me and I will try to fill in progressively more, if I can.

Here's for starters.

 

the theory space is infinite dimensional, he takes a 2D slice of it parametrized by G and Lambda.

 

He and Frank Saueressig (postdoc at Utrecht last time I saw) then calculate all the flow trajectories on this 2D slice. They get that pretty picture with a nongauss fixed point swirl, and some long nearly straight classical portions.

 

He finds "the trajectory that Nature uses". It is the one that goes thru the right values of G and Lambda in the long nearly straight portion.

 

this trajectory is parametrized by a scaleparameter k, actually not a length but a "wavenumber". the arrows point in directon of DECREASING k.

the reciprocal of k is a length, the arrows point in direction of increasing length.

on one of the plots you can see that at one point along the trajectory k^-1 is about 10 microns.

 

At some place along the plot, he indicates the relevant scale: "solar system....galaxy....universe.." That is in the direction of the arrows---so increasing scale and decreasing k.

 

Shucks, it is late. I could explain everything about this anyway. Maybe you can help. I will get back to it tomorrow. really interesting. will take a while to assimilate.

[Reaper]

Thanks for answering my questions.

 

I only listened to the audio twice so I'm still trying to get it around my mind here. I have to listen to the audio separately, I find it hard to follow it if I have to read and listen at the same time.

 

I think I'm understanding it better now.

 

Another question:

 

Page 17 describes a modified Friedmann equation. What exactly does this do, and how does this help predict how the expansion of the universe might go?

 

and

 

You said that k has a decreasing value. But if k does have a non-zero value, wouldn't that mean that spacetime has some sort of curvature, or had one in the beginning?

 

Given that WMAP and COBE data indicate that the universe is flat....

[Martin]

You said that k has a decreasing value. But if k does have a non-zero value, wouldn't that mean that spacetime has some sort of curvature, or had one in the beginning?

 

 

 

the alphabet is too small. cosmologists use k to stand for curvature in the standard Friedmann model. you have probably seen this k>0 for positive curvature, k=0 for flat

 

but that is not this k. the k that Reuter is using is something else----an inverse length serving as an alias for energy

 

physicists use k to stand for a wavenumber. Like 10 per meter.

by planck's constant, wavenumber is proportional to momentum.

with an extra factor of the speed of light you can use k to keep track of energy.

 

basically k here is inverse scale----smaller means higher energy

 

in QUANTUM FIELD THEORY several of the important constants have been discovered to VARY with k. the fine structure constant we know as alpha or about 1/137, which tells the strength of the electromag'tic force, actually varies. As k goes to infinity (as you get infinitely close to the charged particle) the value of alpha increases. What we are used to is only the limit for small k. The "Infrared" or low energy limit. It is good for almost everything down to atoms and even smaller! Physicists call it the "RUNNING" of alpha.

 

what Reuter and his co-workers have found is evidence that newton G RUNS. but in the opposite direction----that is at very tiny distances which we are unable to observe G is smaller----and then for a broad range encompassing our experience with earth gravity and solar system it varies imperceptibly if at all----and then at galactic scale it is a bit larger---maybe that can explain some phenoms we associate with "dark matter", beyond that we don't know

 

So he has G depend on k (the scale, or rather the inverse scale)

the limit of G as k goes to infinity (i.e. smallest possible scale) is called the

BARE value of G. He talks about "screening" and "anti-screening"---the EM force is weakened by screening at large distance, vacuum polarization---and the G force is antiscreened by distance, strengthened. It's tough. I'm struggling to understand too. It's new stuff.

 

he also has Lambda the cosmo constant RUN, i.e. depend on k.

Lambda makes expansion accelerate. the BARE Lambda applies for high k, high energy, small scale, and the bare Lambda is very large---like in early universe---so there was extremely rapid accelerating expansion we call inflation

 

I don't want to suggest that k decreases with TIME. At any one given time there are processes occurring at all different scales. Galaxy rotation may be governed by a different G_k from solar system orbits because different k.

 

I know this sounds crazy. I've been watching Reuter papers for 3 years and it is beginning to sink in that it is not so crazy----no more crazy than QED and QCD where coupling constants run----differ at differnt scales---and those theories are very successful.

 

anyway the running is not in TIME (unless by coincidence there is some process in which scale changes regularly with time like the expansion of spatial distance)

 

so I should not have said k has a decreasing value in time---except by coincidence in some special circumstance

 

 

Another question:

 

Page 17 describes a modified Friedmann equation. What exactly does this do, and how does this help predict how the expansion of the universe might go?

.

 

Do you know the ordinary Friedmann equations? They are the backbone of cosmology. Friedmann got them around 1923 by simplifying the Einstein equation of Gen Rel down to the homog and isotrop case.

The Friedmann equations define a(t) the "size of universe" scalefactor that goes into the Friedmann Robertson Walker metric, which is the metric used in 99 percent of all cosmology. You may know all this. In which case you know that standard model cosmology is LambdaCDM model, and it is the Friedmann equation (with nonzero Lambda) which is used to predict the whole expansion history of the universe.

 

It is a simple differential equation involving the scalefactor a(t). the a(t) coefficient is plugged into the metric, therefore as it increases all spatial distances increase---that is all that is meant by "expansion of space"---distances as measured by the metric increase because the a(t) increases, because of this simple (Friedmann) equation.

 

You may know it so I won't copy it down. But if you don't know it, tell me and I will write it in and/or get a link

 

the whole thing in quantum cosmology is you want to QUANTIZE the classical Friedmann equation so that it shows the evolution of the WAVEFUNCTION of the scalefactor a(t)-----the wavefunction of the size of the universe----instead of the exact value a(t) itself.

 

since the Friedmann equation is simple, it will turn out in any decent quantum cosmology that the quantized version is also very simple---just a few symbols. It's nice. You can calculate with it. The is one reason cosmology is such a nice field.

 

Im not sure what your question is, so I am risking telling you stuff you already know. sorry if it's inadvertently confusing

 

here is another thing. the HUBBLE PARAMETER H(t) IS DEFINED TO BE the ratio a'(t)/a(t).

If you cut out all the babble that is all it is. The timederivative of a(t) divided by a(t) itself. If you plug in t=present, then you get the present value of the hubble parameter which they are always quoting as 71 km/second per Megaparsec.

Well the more important of the two Friedmann equations, the one they call THE Friedmann equation, just gives you a simple way to calculate that ratio. In other words it tells you hoe the Hubble parameter is evolving, based on things like the density of matter.

Maybe you can find something about it in Wikipedia.

[bascule]

So as someone who flies by intuition on high-level metadata... what is "it" (beyond "Reuter's talk")? Judging from the context it appears to be some LQG formulation, but what? Does "it" have a name? Is "it" predictive beyond Einstein-Hilbert action?

[Martin]

Bascule, I'm pleased that you are interested in this

there's an idea from greek drama---*peripateia*---surprise, reversal, sudden change of fortune

science goes thru similar plot elements as other historical story lines

some element of comedy here also

 

in classic Gen Rel the geometry of spacetime is represented by a METRIC or distance function---so the obvious way to quantize is to quantize the metric---perhaps as a series expansion around the flat (special rel) metric.

But if you do this it blows up---you get infinities and as soon as you plug one another one appears.

 

 

In 1970s everybody thought any theory of gravity must be NON-RENORMALIZABLE (at least if you took the obvious approach.)

 

the quantum theories of electromagn'ism (q.e.d.) and strongforce (q.c.d)

had infinities but you could control them by adjusting a finite set of numbers

which, moreover, had reasonable physical interpretations

so those theories were called "renormalizable"

 

but in the 1970s people's naive attempt to do gravity the same way failed

because they kept getting infinities and it looked like they would need to adjust an INFINITE set of numbers to control them

 

in 1979 Weinberg tried a clever idea he called "asymptotic safety" in a final attempt to make gravity renormalizable. He succeeded in lower dimension and failed in D=4. So everybody GAVE UP the direct frontal approach.

 

That is essentially why in all the years after 1980 there was so much fuss about quantum gravity. People thought some extraordinary apocalyptic new departure in theory would be needed because the obvious approach didnt work and it was "non-renormalizable".

 

However in 1996 Reuter found suggestive but inconclusive evidence that gravity was "asymptotically safe" and thus WAS RENORMALIZABLE AFTER ALL.

Asympt. safety means that you can use a flow provided by Nature in the infinite dimensional space of versions of the theory----use this flow to take care of the infinities. You only have to choose a finite set of numbers (physically meaningful, as in the qed and qcd cases) and that gets you on the right flow trajectory and nature does the rest---it sweeps your theory to a fixed point in the space of theories. Essentially nature has chosen all the rest of the numbers for you.

 

But asymptotic safety is VERY HARD TO PROVE because you are trying to sense the existence of an ATTRACTOR in an infinite-dimensional space and determine the existence of this fixed point attractor by taking finite dimensional slices thru the infinite dimension space of theories. It almost requires luck. It is like tossing twigs into the ocean to map out its currents, and its almost too dark to see. they spent on the order of ten years confirming that it really exists.

 

Reuter and half a dozen other people including a young fellow named Saueressig worked on this. they were looking for more and more confirmation that this attractor-point in the infinite dimension space really existed (and really did correspond to the Einstein-Hilbert action functional which was kind of a weird coincidence, almost too good to be true, Einstein was right after all you gotta be kidding!!!)

Essig means vinegar in German. so Saueressig means "sour vinegar"

He helped Reuter plot the rather beautiful pictures of the flow, like what you see on page 10 of the slides.

 

After a lot of study of many different cases and a lot of numerical work, Reuter can say with confidence that in some sense people were wrong in 1980 to give up and say gravity was non-renormalizable. And he can say that the PREMISE of a lot of work was prematurely taken.

 

So we are at a kind of cusp now, Reuter gave a plenary talk at Loops 05 and then again a stronger talk at Loops 07, and the natural question is ....well there are a lot of questions.

 

I suspect it means that LQG and several other non-string QG approaches will turn out to be RIGHT, just alternative ways of doing the same thing, and they will CONVERGE. And also I think probably LQG, Spinfoam and such will be UTTERLY RENOVATED AND TRANSFORMED by this, because for one thing it involves a SCALE-DEPENDENT NEWTON'S constant G. Newton's constant isnt really constant. It is constant or very very slowly changing over a very wide range from like a centimeter to the edge of the solarsystem. But if you span halfway across a galaxy you might detect, MIGHT detect, some small percentage variation. I am not sure about the magnitudes. But it is pretty radical to have a constant which isnt constant and this will be a shock to the QG people. So they will be staying up nights rebuilding their theories.

 

Greek plays were built around plot elements like this, surprise surprise it is all different from what you thought. hah. hah. nature seems to be playing with us.

====================

 

You want to know what to call IT. The technical terms are opaque. Reuter calls it "Asymptotically Safe Quantum Gravity" or sometimes he calls it

"Quantum Einstein Gravity" to remind people that it is the original approach of quantizing the metric tensor in einstein original theory---the obvious approach that people gave up circa 1980.

 

I don't know what to call it. It is a quantum theory of geometry. spacetime geometry is the main thing. the METRIC tells the geometry. the metric is the gravitational field. shape = gravity.

IF Reuter is right---and it is by no means certain, but looking more likely---then the outcome is in some sense the most boring possible.

 

something like QMD quantum metro dynamics just goes up on the shelf to sit beside QED (quantum electro dynamics) and QCD (quantum chromo dynamics)

[Reaper]

Do you know the ordinary Friedmann equations? They are the backbone of cosmology. Friedmann got them around 1923 by simplifying the Einstein equation of Gen Rel down to the homog and isotrop case.

The Friedmann equations define a(t) the "size of universe" scalefactor that goes into the Friedmann Robertson Walker metric, which is the metric used in 99 percent of all cosmology. You may know all this. In which case you know that standard model cosmology is LambdaCDM model, and it is the Friedmann equation (with nonzero Lambda) which is used to predict the whole expansion history of the universe.

 

 

I know the ordinary ones. I don't have a great grasp of them yet though.

 

 

What I was asking was what does modifying them accomplish, sorry if the question was ambiguous. I'm sure its in the audio somewhere, but either didn't catch it or quite understand it....

 

cosmologists use k to stand for curvature in the standard Friedmann model. you have probably seen this k>0 for positive curvature, k=0 for flat

 

but that is not this k. the k that Reuter is using is something else----an inverse length serving as an alias for energy

 

physicists use k to stand for a wavenumber. Like 10 per meter.

by planck's constant, wavenumber is proportional to momentum.

with an extra factor of the speed of light you can use k to keep track of energy.

 

basically k here is inverse scale----smaller means higher energy

 

Oh, ok then. The one I was familiar with was the one from the friedmann model. Now it makes more sense.

 

the alphabet is too small....

 

 

Maybe we should start using Chinese symbols . They have about 5000+ characters...

 

I suspect it means that LQG and several other non-string QG approaches will turn out to be RIGHT, just alternative ways of doing the same thing, and they will CONVERGE. And also I think probably LQG, Spinfoam and such will be UTTERLY RENOVATED AND TRANSFORMED by this, because for one thing it involves a SCALE-DEPENDENT NEWTON'S constant G. Newton's constant isnt really constant. It is constant or very very slowly changing over a very wide range from like a centimeter to the edge of the solarsystem. But if you span halfway across a galaxy you might detect, MIGHT detect, some small percentage variation. I am not sure about the magnitudes. But it is pretty radical to have a constant which isnt constant and this will be a shock to the QG people. So they will be staying up nights rebuilding their theories.

 

I always found string theory to be suspicious. I remember reading Brian Greene's "Elegant Universe" not too long ago (yes I know its a popularization, but hey, you gotta start somewhere!), and when he was describing Bosonic Strings, I was wondering what those other 22 dimensions were supposed to be! Never mind a ten dimensional universe.

 

Do you know what those other dimensions are? I know string theory isn't your thing, but I'm sure you have a better understanding of it then I do. I hope they aren't making it up....

 

 

---------------------------------------------------------------------

 

If G does indeed strengthens over large distances, that would probably eliminate the need for dark matter all together. Interesting.

 

But how does that account for the observed phenomenon that the expansion of the universe is accelerating? To me, a variable G would imply that we should see more blue shifted galaxies. Or is that something else all together?

[Martin]

If G does indeed strengthens over large distances, that would probably eliminate the need for dark matter all together. Interesting.

 

interesting possibility but still very iffy. there might still be dark matter, just not so much of it. too early to judge. I'm completely in the dark:-)

 

I may have given you the wrong idea about something yesterday. Look at page 15. He only has dotted lines in the "far infrared" long distance portion. Those plots are about high k, approaching the fixed point. It would concern early universe and small distances.

 

Page 15 seems to be saying that in early universe situations G is small and Lambda is very large. That would be great for an inflationary era.

 

but it seems to say that except for this "ultraviolet" section, G and Lambda are CONSTANT. they have long flat sections.

 

But how does that account for the observed phenomenon that the expansion of the universe is accelerating? To me, a variable G would imply that we should see more blue shifted galaxies. Or is that something else all together?

What I see him saying is that the "running" of G and Lambda only occurs, and has a significant effect, in the early universe.

 

In later times, e.g. in the present, his theory just REPRODUCES the success of the standard LambdaCDM model which fits the supernova data reasonalbly well so far. In later times Reuter's picture has G and Lambda essentially CONSTANT, so everything is normal and the observed mild acceleration is explained by the small positive Lambda.

 

Sorry if I gave you the idea that he might be offering an explanation of the "dark matter" effect. He could have said something about dark matter in another paper, or in some other part of this talk, which I was remembering. I'll see that there's time today to make a bit more progress understanding this talk.

 

===========================

About the RG improved Friedmann equation on page 18. It is just the ordinary Friedmann except that there is time dependence of G(t) and Lambda(t).

 

Ordinary Friedmann would just have them constant G and Lambda with no "(t)" tacked on to show time dependence.

 

He draws a rough picture of how k(t) might go in early universe----monotone decreasing

he already has that G and Lambda RUN, i.e. they depend on k. so if he can estimate a rough time dependence for k = k(t) then he can PLUG THAT IN and have a time dependent G(t) and Lambda(t).

 

Then when he solves the differential equation step by step he can plug in the appropriate G and Lambda for that moment in time---that will make the solution more realistic, so it is an improvement.

I would add that the solution to the improved Friedman gives an expansion history, so that would FEED BACK to one's estimate of how k(t) goes, so one could do successive approximation and gradually improve both the expansion history and the plot of k(t).

==========================

 

I had time to look back to see where I imagined that Reuter model might possibly explain part of the "dark matter" effect. There is really just one sentence and it is very vague and tentative. I'd erase it if I could edit, because it is too speculative. But as it is, it is not too bad.

Screening and antiscreening only happen in very close quarters AFAIK. I only expect running of constants at very small scale and high energy.

To imagine effects in the far infrared is extremely speculative, although even Reuter must occasionally think about the possibility.

[bascule]

Bascule, I'm pleased that you are interested in this

there's an idea from greek drama---*peripateia*---surprise, reversal, sudden change of fortune

science goes thru similar plot elements as other historical story lines

some element of comedy here also

 

I'm certainly interested in whatever revolutions may stem outside of what seems from outward appearances to be a near monoculture (i.e. string theory) in modern physics. Hopefully you can relay to me that that's not the case, but it's the gist of what I got from Smolin.

 

In 1970s everybody thought any theory of gravity must be NON-RENORMALIZABLE (at least if you took the obvious approach.)

 

[...]

 

I thank you for the technical description but I'm afraid most of it is lost on me

 

So we are at a kind of cusp now, Reuter gave a plenary talk at Loops 05 and then again a stronger talk at Loops 07, and the natural question is ....well there are a lot of questions.

 

I suspect it means that LQG and several other non-string QG approaches will turn out to be RIGHT, just alternative ways of doing the same thing, and they will CONVERGE. And also I think probably LQG, Spinfoam and such will be UTTERLY RENOVATED AND TRANSFORMED by this, because for one thing it involves a SCALE-DEPENDENT NEWTON'S constant G. Newton's constant isnt really constant. It is constant or very very slowly changing over a very wide range from like a centimeter to the edge of the solarsystem. But if you span halfway across a galaxy you might detect, MIGHT detect, some small percentage variation. I am not sure about the magnitudes. But it is pretty radical to have a constant which isnt constant and this will be a shock to the QG people. So they will be staying up nights rebuilding their theories.

 

This idea greatly appeals to me. I was first exposed to it by Brian Greene describing dualities in string theory, then by Lee Smolin when he described how LQG and string theory could both be approximations of the same underlying theory.

 

As I understand it the best way to approach to realizing the the reality of the situation is to pick out the best bits and pieces of several different theories and attempt to assemble them into a single, coherent model (this works for all domains of life, by the way)

 

Greek plays were built around plot elements like this, surprise surprise it is all different from what you thought. hah. hah. nature seems to be playing with us.

 

From my intuition-based layman's perspective my sense is that reality and the structures it comprises are actually emergent effects of a completely different underlying system. Realism as we understand it is dead, and modern physics is attempting to re-realize realism (wow) from an entirely different (background independent) perspective on how reality actually operates. Getting over the hump, so to speak, seems to be insurmountably difficult.

 

You want to know what to call IT. The technical terms are opaque. Reuter calls it "Asymptotically Safe Quantum Gravity" or sometimes he calls it

"Quantum Einstein Gravity" to remind people that it is the original approach of quantizing the metric tensor in einstein original theory---the obvious approach that people gave up circa 1980.

 

I don't know what to call it. It is a quantum theory of geometry. spacetime geometry is the main thing. the METRIC tells the geometry. the metric is the gravitational field. shape = gravity.

IF Reuter is right---and it is by no means certain, but looking more likely---then the outcome is in some sense the most boring possible.

 

something like QMD quantum metro dynamics just goes up on the shelf to sit beside QED (quantum electro dynamics) and QCD (quantum chromo dynamics)

 

All right, well I'll count on you to keep us apprised