BFL Ward's Resummed QG: Renormalizable Theory & Cosmological Constant

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In summary: B.F.L. Ward (1 and 2) ((1) Werner-Heisenberg-Institut, Max-Planck-Institut fuer Physik, Muenchen, Germany, (2) Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee, USA)We present a new approach to quantum gravity starting from Feynman's formulation for the simplest example, that of a scalar field as the representative matter. We show that we extend his treatment to a calculable framework using resummation techniques already well-tested in other problems. Phenomenological consequences for Newton's law are described.7 pages, 1 figure; published Mod.Phys.Lett
  • #1
erkokite
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Anyone have any thoughts on BFL Ward's work? He claims to have found a perturbatively renormalizable QG theory by using a resummation method. By treating the cosmological constant as a coupling constant, he was able to derive its observed value (or very close to it). There are connections to the Asymsafe models.

Anyone have any thoughts on this?
 
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  • #3
Demystifier said:
Can you give a link to the paper?
I think the main paper (which he headlined in a Perimeter conference presentation) is:
http://arxiv.org/abs/hep-ph/0204102
Quantum Corrections to Newton's Law
B.F.L. Ward (1 and 2) ((1) Werner-Heisenberg-Institut, Max-Planck-Institut fuer Physik, Muenchen, Germany, (2) Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee, USA)

We present a new approach to quantum gravity starting from Feynman's formulation for the simplest example, that of a scalar field as the representative matter. We show that we extend his treatment to a calculable framework using resummation techniques already well-tested in other problems. Phenomenological consequences for Newton's law are described. 7 pages, 1 figure; published Mod.Phys.Lett. A17 (2002) 2371-2382

This has been cited 7 times by others in the literature, plus 18 citations by Ward himself, for a total of 25. Here's a video of him explaining his ideas at Perimeter conference in November 2009.
http://pirsa.org/09110043/
Asymptotic Safety and Resummed Quantum Gravity
Speaker(s): B.F.L. Ward
Abstract: In Weinberg’s asymptotic safety approach to quantum gravity, one has a finite dimensional critical surface for a UV stable fixed point to generate a theory of quantum gravity with a finite number of physical parameters. The task is to demonstrate how this fixed point behavior actually arises. We argue that, in a recently formulated extension of Feynman’s original formulation of the theory, which we have called resummed quantum gravity, we recover this fixed-point UV behavior from an exact re-arrangement of the respective perturbative series. We argue that the results we obtain are consistent both with the exact field space Wilsonian renormalization group results of Reuter and Bonanno and with recent Hopf-algebraic Dyson-Schwinger renormalization theory results of Kreimer. We calculate the first "first principles" predictions of the respective dimensionless gravitational and cosmological constants and argue that they support the Planck scale cosmology advocated by Bonanno and Reuter as well. Comments on the prospects for actually predicting the currently observed value of the cosmological constant are also given.
Date: 05/11/2009 - 4:30 pm
Collection: Asymptotic Safety-30 Years After

On page 4 of the Perimeter slides he says he has a new approach and refers only to the 2002 paper of his published in Modern Physics Letters A17 page 2371
"We showed that resummation cures the UV problems of Einstein's theory."
This is the main citation he gives to his own work in this 2009 presentation.

However, towards the end of the presentation, around slide 34, he gives two arxiv numbers:
http://arxiv.org/abs/0808.3124
http://arxiv.org/abs/hep-ph/0607198
These are related to cosmology or a secondary issue, not his central message, but they would have citations to earlier work.
[Yes, 0808.3124 cites "[10] B.F.L. Ward, Mod. Phys. Lett. A17 (2002) 237; Mod. Phys. Lett. A19 (2004) 14; J. Cos. Astropart. Phys.0402 (2004) 011; hep-ph/0605054, hep-ph/0503189,0502104, hep-ph/0411050, 0411049, 0410273 and references therein."]

If I wanted a representative account, I would check out the 2002 paper that serves as the main reference in this conference talk.
(Or watch a few minutes of the video. The questions from the audience start at minute 48, ten minutes from the end. I thought I heard Steven Weinberg put in a comment or two.)
 
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  • #4
Another important paper:

An Estimate of Λin Resummed Quantum Gravity in the Context of Asymptotic Safety
B.F.L. Ward (1) ((1) Department of Physics, Baylor University, Waco, TX, USA)
(Submitted on 5 Aug 2010 (v1), last revised 18 Oct 2010 (this version, v3))

We show that, by using recently developed exact resummation techniques based on the extension of the methods of Yennie, Frautschi and Suura to Feynman's formulation of Einstein's theory, we get quantum field theoretic descriptions for the UV fixed-point behaviors of the dimensionless gravitational and cosmological constants postulated by Weinberg. Connecting our work to the attendant phenomenological asymptotic safety analysis of Planck scale cosmology by Bonanno and Reuter, we predict the value of the cosmological constant \Lambda. We find the encouraging estimate \rho_\Lambda\equiv \frac{\Lambda}{8\pi G_N} \simeq (2.400\times 10^{-3}eV)^4.

http://arxiv.org/abs/1008.1046" [Broken]
 
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  • #5
He gives the measured value of rhoLambda as around
(0.002368 eV)4

which makes his own theoretical estimate surprisingly close.

I tried parsing that with the Google calculator to get more conventional units. I am used to thinking of rhoLambda, the cosmo constant as energy density, as around 0.6 nanojoules per cubic meter.

So I put his figure into google window
0.002368^4 *(1 eV)^4 *(hbar*c)^-3
and indeed it did come out about right: 0.656 nanoPascal or 0.656 nanojoule per cubic meter.

0.002368^4 *(1 eV)^4 is what he said using particle physics vernacular and then I tacked on
(hbar*c)^-3 to make the units come out right (he would think of that as one.)

The source he quotes giving the observed value of the cosmo constant does not give it that way. It gives rho_Lambda as a fraction of the critical density, as I recall. Omega_Lambda.

So to convert that to some other energy density units you have to assume and insert a value for the cosmologists estimate of critical density. When that is not made explicit it can get confusing.

His theoretical Lambda value is not the same as what he said in 2009. As I recall in 2009 it was much smaller than the observed, now, in 2011 it is virtually identical to the observed. It seems almost too good to be true.
 
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1. What is BFL Ward's Resummed QG theory?

BFL Ward's Resummed QG theory is a theory of quantum gravity, which aims to unify the theories of general relativity and quantum mechanics. It proposes a new framework for understanding gravity at a fundamental level, by incorporating the concept of renormalization, which is a mathematical technique used to remove infinities from equations in quantum field theory.

2. How is BFL Ward's Resummed QG theory different from other theories of quantum gravity?

Unlike other theories of quantum gravity, BFL Ward's Resummed QG theory is renormalizable, which means that it can produce finite and meaningful results without the need for additional mathematical techniques. This makes it a more elegant and self-consistent theory, which is able to make testable predictions.

3. What is the role of the cosmological constant in BFL Ward's Resummed QG theory?

The cosmological constant is a term that Einstein introduced into his theory of general relativity to explain the expansion of the universe. In BFL Ward's Resummed QG theory, the cosmological constant is also included and plays a crucial role in the renormalization process. It is used to remove infinities and ensure that the theory produces finite and meaningful results.

4. What are the implications of BFL Ward's Resummed QG theory for cosmology?

BFL Ward's Resummed QG theory has important implications for our understanding of the early universe and the cosmic inflation that occurred in the first moments after the Big Bang. It provides a more complete and consistent framework for studying these phenomena, and could potentially help to resolve some of the current mysteries in cosmology, such as the nature of dark matter and dark energy.

5. Is there any experimental evidence for BFL Ward's Resummed QG theory?

Currently, there is no direct experimental evidence for BFL Ward's Resummed QG theory. However, there are ongoing experiments and observations that could potentially provide evidence for the predictions of this theory, such as gravitational wave detection and measurements of the cosmic microwave background radiation. Further research and experimentation are needed to fully test and validate this theory.

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