# Our picks for fourth quarter 2009 MIP (most important QG paper)

## Which papers (see titles below) will prove most valuable to future research?

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12. ### Percacci Narain

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1. Dec 31, 2009

### marcus

Of these twelve candidates, please indicate the paper or papers which you think will contibute most significantly to future research in 4D quantum gravity. Multiple choice is possible in the poll, so pick several if you wish.

Barrett Fairbairn Hellmann http://arxiv.org/abs/0912.4907
Quantum gravity asymptotics from the SU(2) 15j symbol

Ashtekar Sloan http://arxiv.org/abs/0912.4093
Loop quantum cosmology and slow roll inflation

Bianchi Magliaro Perini http://arxiv.org/abs/0912.4054
Coherent spin-networks

Dittrich Höhn http://arxiv.org/abs/0912.1817
From covariant to canonical formulations of discrete gravity

Lewandowski Kamiński Kisielowski http://arxiv.org/abs/0912.0540
The EPRL intertwiners and corrected partition function

Shaposhnikov Wetterich http://arxiv.org/abs/0912.0208
Asymptotic safety of gravity and the Higgs boson mass

Krasnov Torres http://arxiv.org/abs/0911.3793
Gravity-Yang-Mills-Higgs unification by enlarging the gauge group

Freidel Livine http://arxiv.org/abs/0911.3553
The Fine Structure of SU(2) Intertwiners from U(N) Representations

Thiemann Engle Han http://arxiv.org/abs/0911.3433
Canonical path integral measures for Holst and Plebanski gravity. I. Reduced Phase Space Derivation

Weinberg http://arxiv.org/abs/0911.3165
Asymptotically Safe Inflation

Rovelli Ding http://arxiv.org/abs/0911.0543
The volume operator in covariant quantum gravity

Percacci Narain http://arxiv.org/abs/0911.0386
Renormalization Group Flow in Scalar-Tensor Theories. I

2. Dec 31, 2009

### tom.stoer

You should perhaps add the complete series of the Tiemann papers (I have to admit that I am disappointed - Thiemann is defintitly on the right track in bringing together canonical and PI LQG - but it is still in a preliminary stage)

3. Dec 31, 2009

### marcus

Tom, thanks for your comment and suggestion! In the past the poll has sometimes been set up for choosing between bundles of papers. Instead of a single representative paper for each main author, there would be a bundle of papers that appeared during the given quarter.

It's really an arbitrary judgement, how to keep the poll a manageable size and approximately fair to the different ideas.

I hope you will take the Thiemann Engle Han paper as a representative (one standing for many that appeared from Thiemann's group) and cast a vote for it.

4. Jan 1, 2010

### marcus

Let's see if any of the papers have been cited yet. It's pretty early but a prominent one might have been referenced already in other resarch.

Barrett Fairbairn Hellmann http://arxiv.org/abs/0912.4907
Quantum gravity asymptotics from the SU(2) 15j symbol
http://arxiv.org/cits/0912.4907

Ashtekar Sloan http://arxiv.org/abs/0912.4093
Loop quantum cosmology and slow roll inflation
http://arxiv.org/cits/0912.4093

Bianchi Magliaro Perini http://arxiv.org/abs/0912.4054
Coherent spin-networks
http://arxiv.org/cits/0912.4054

Dittrich Höhn http://arxiv.org/abs/0912.1817
From covariant to canonical formulations of discrete gravity
http://arxiv.org/cits/0912.1817

Lewandowski Kamiński Kisielowski http://arxiv.org/abs/0912.0540
The EPRL intertwiners and corrected partition function
http://arxiv.org/cits/0912.0540

Shaposhnikov Wetterich http://arxiv.org/abs/0912.0208
Asymptotic safety of gravity and the Higgs boson mass
http://arxiv.org/cits/0912.0208

Krasnov Torres http://arxiv.org/abs/0911.3793
Gravity-Yang-Mills-Higgs unification by enlarging the gauge group
http://arxiv.org/cits/0911.3793

Freidel Livine http://arxiv.org/abs/0911.3553
The Fine Structure of SU(2) Intertwiners from U(N) Representations
http://arxiv.org/cits/0911.3553

Thiemann Engle Han http://arxiv.org/abs/0911.3433
Canonical path integral measures for Holst and Plebanski gravity. I. Reduced Phase Space Derivation
http://arxiv.org/cits/0911.3433

Weinberg http://arxiv.org/abs/0911.3165
Asymptotically Safe Inflation
http://arxiv.org/cits/0911.3165

Rovelli Ding http://arxiv.org/abs/0911.0543
The volume operator in covariant quantum gravity
http://arxiv.org/cits/0911.0543

Percacci Narain http://arxiv.org/abs/0911.0386
Renormalization Group Flow in Scalar-Tensor Theories. I
http://arxiv.org/cits/0911.0386

So far the research community interest (as shown by citations) seem to be in agreement with Finbar, Tom Stoer, Atyy and Dr Chinese!

The Dr. picked just one paper and that one has now already been cited. (It's still early, only 4 out of the 12 have been cited as yet. So that's good.)
Tom Stoer put in a voice vote for Thiemann's paper and Atyy also selected that one on the poll. It has done well.
Atyy moreover picked another that has garnered a citation already.
The one Finbar picked has already gotten two cites.

Last edited: Jan 2, 2010
5. Jan 2, 2010

### marcus

Here are links to the first three quarterly polls in 2009

We should start assembling candidates for the best of the year. Here are some from first quarter

http://arxiv.org/abs/0902.4630
Taming perturbative divergences in asymptotically safe gravity
"We use functional renormalization group methods to study gravity minimally coupled to a free scalar field. This setup provides the prototype of a gravitational theory which is perturbatively non-renormalizable at one-loop level, but may possess a non-trivial renormalization group fixed point controlling its UV behavior. We show that such a fixed point indeed exists within the truncations considered, lending strong support to the conjectured asymptotic safety of the theory. In particular, we demonstrate that the counterterms responsible for its perturbative non-renormalizability have no qualitative effect on this feature."

http://arxiv.org/abs/0902.0351
Quantum geometry from phase space reduction
"In this work we give an explicit isomorphism between the usual spin network basis and the direct quantization of the reduced phase space of tetrahedra. The main outcome is a formula that describes the space of SU(2) invariant states by an integral over coherent states satisfying the closure constraint exactly, or equivalently, as an integral over the space of classical tetrahedra. This provides an explicit realization of theorems by Guillemin--Sternberg and Hall that describe the commutation of quantization and reduction. In the final part of the paper, we use our result to express the FK spin foam model as an integral over classical tetrahedra and the asymptotics of the vertex amplitude is determined."

Horava
http://arxiv.org/abs/0901.3775
Quantum Gravity at a Lifgarbagez Point
"We present a candidate quantum field theory of gravity with dynamical critical exponent equal to z=3 in the UV. (As in condensed matter systems, z measures the degree of anisotropy between space and time.) This theory, which at short distances describes interacting nonrelativistic gravitons, is power-counting renormalizable in 3+1 dimensions. When restricted to satisfy the condition of detailed balance, this theory is intimately related to topologically massive gravity in three dimensions, and the geometry of the Cotton tensor. At long distances, this theory flows naturally to the relativistic value z=1, and could therefore serve as a possible candidate for a UV completion of Einstein's general relativity or an infrared modification thereof. The effective speed of light, the Newton constant and the cosmological constant all emerge from relevant deformations of the deeply nonrelativistic z=3 theory at short distances."

Here are some from second quarter:

Magnen Noui Rivasseau Smerlak
http://arxiv.org/abs/0906.5477
Scaling behaviour of three-dimensional group field theory
"Group field theory is a generalization of matrix models, with triangulated pseudomanifolds as Feynman diagrams and state sum invariants as Feynman amplitudes. In this paper, we consider Boulatov's three-dimensional model and its Freidel-Louapre positive regularization (hereafter the BFL model) with a 'ultraviolet' cutoff, and study rigorously their scaling behavior in the large cutoff limit. We prove an optimal bound on large order Feynman amplitudes, which shows that the BFL model is perturbatively more divergent than the former. We then upgrade this result to the constructive level, using, in a self-contained way, the modern tools of constructive field theory: we construct the Borel sum of the BFL perturbative series via a convergent ?cactus' expansion, and establish the 'ultraviolet' scaling of its Borel radius. Our method shows how the 'sum over triangulations' in quantum gravity can be tamed rigorously, and paves the way for the renormalization program in group field theory."

Ambjorn Jurkiewicz Loll
http://arxiv.org/abs/0906.3947
Quantum gravity as sum over spacetimes
"A major unsolved problem in theoretical physics is to reconcile the classical theory of general relativity with quantum mechanics. These lectures will deal with an attempt to describe quantum gravity as a path integral over geometries known as 'Causal Dynamical Triangulations' (CDT)."

Freidel Gurau Oriti
http://arxiv.org/abs/0905.3772
Group field theory renormalization - the 3d case: power counting of divergences
"We take the first steps in a systematic study of Group Field Theory renormalization, focusing on the Boulatov model for 3D quantum gravity. We define an algorithm for constructing the 2D triangulations that characterize the boundary of the 3D bubbles, where divergences are located, of an arbitrary 3D GFT Feynman diagram. We then identify a special class of graphs for which a complete contraction procedure is possible, and prove, for these, a complete power counting. These results represent important progress towards understanding the origin of the continuum and manifold-like appearance of quantum spacetime at low energies, and of its topology, in a GFT framework."

Engle Noui Perez
http://arxiv.org/abs/0905.3168
Black hole entropy and SU(2) Chern-Simons theory
"We show that the isolated horizon boundary condition can be treated in a manifestly SU(2) invariant manner. The symplectic structure of gravity with the isolated horizon boundary condition has an SU(2) Chern-Simons symplectic structure contribution at the horizon with level $$k=a_H/ (4\pi \beta \ell^2_p)$$. Upon quantization, state counting is expressed in terms of the dimension of Chern-Simons Hilbert spaces on a sphere with marked points (defects). In the large black hole limit quantum horizon degrees of freedom can be modelled by a single intertwiner. The coupling constant of the defects with the Chern Simons theory on the horizon is precisely given by the ratio of the area contribution of the defect to the macroscopic area $$a_H$$, namely $$\lambda= 16\pi^2 \beta \ell^2_p (j(j+1))^{1/2}/a_H$$."

Here are some from third quarter (instead of copying the authors' abstracts, I added brief thumbnail review comments):

Lewandowski Kamiński Kisielowski
http://arxiv.org/abs/0909.0939
Spin-Foams for All Loop Quantum Gravity
Rigorously confirms the fit between spin foams and the spin networks of canonical LQG.

Dittrich Bahr
http://arxiv.org/abs/0907.4323
Improved and Perfect Actions in Discrete Gravity
Introduces Regge with curved blocks. Exact (not merely approximate) lattice quantum gravity.

Barrett Dowdall Fairbairn Hellmann Pereira
http://arxiv.org/abs/0907.2440
Lorentzian Spin Foam Amplitudes: Graphical Calculus and Asymptotics
Graphic calculus means inventing something like Feynman diagrams to organize and conceptualize spin foam amplitude calculations. Authors prove that the set of Lorentz rep labels which EPRL chose is actually forced. It would seem to be the only right set of representations to use for labeling spin foams! Firms up the new model's formula for amplitudes.

Here are some from fourth quarter:

Krasnov Torres
http://arxiv.org/abs/0911.3793
Gravity-Yang-Mills-Higgs unification by enlarging the gauge group

Thiemann Engle Han
http://arxiv.org/abs/0911.3433
Canonical path integral measures for Holst and Plebanski gravity. I. Reduced Phase Space Derivation

Percacci Narain
http://arxiv.org/abs/0911.0386
Renormalization Group Flow in Scalar-Tensor Theories. I

Last edited: Jan 3, 2010
6. Jan 3, 2010

7. Jan 3, 2010

### marcus

Those are good suggestions! On reconsideration I put them in.
We now have 13 items, which begins to look a bit cumbersome. But I don't see any to drop.

I'm having second thoughts about the Freidel Gurau Oriti (one of your two suggestions) because as a 3D case study it is preliminary---a kind of temporary way-station for the authors. Or so I think. It represents an initiative which, if successful, will be produce a 4D treatment---and that will be the one that gets people's attention.

Last edited: Jan 3, 2010
8. Jan 3, 2010

### marcus

I've shortened the listing by eliminating the abstracts, to make it easier to eye-ball, and added some additional links for convenience.

first quarter:

http://arxiv.org/abs/0902.4630
http://arxiv.org/cits/0902.4630
Taming perturbative divergences in asymptotically safe gravity

http://arxiv.org/abs/0902.0351
http://arxiv.org/cits/0902.0351
Quantum geometry from phase space reduction

Horava
http://arxiv.org/abs/0901.3775
http://arxiv.org/cits/0901.3775
Quantum Gravity at a Lifgarbagez Point

second quarter:

Magnen Noui Rivasseau Smerlak
http://arxiv.org/abs/0906.5477
http://arxiv.org/cits/0906.5477
Scaling behaviour of three-dimensional group field theory

Ambjorn Jurkiewicz Loll
http://arxiv.org/abs/0906.3947
http://arxiv.org/cits/0906.3947
Quantum gravity as sum over spacetimes

Freidel Gurau Oriti
http://arxiv.org/abs/0905.3772
http://arxiv.org/cits/0906.3772
Group field theory renormalization - the 3d case: power counting of divergences

Engle Noui Perez
http://arxiv.org/abs/0905.3168
http://arxiv.org/cits/0905.3168
Black hole entropy and SU(2) Chern-Simons theory

third quarter:

Lewandowski Kamiński Kisielowski
http://arxiv.org/abs/0909.0939
http://arxiv.org/cits/0909.0939
Spin-Foams for All Loop Quantum Gravity

Dittrich Bahr
http://arxiv.org/abs/0907.4323
http://arxiv.org/cits/0907.4323
Improved and Perfect Actions in Discrete Gravity

Barrett Dowdall Fairbairn Hellmann Pereira
http://arxiv.org/abs/0907.2440
http://arxiv.org/cits/0907.2440
Lorentzian Spin Foam Amplitudes: Graphical Calculus and Asymptotics

fourth quarter:

Krasnov Torres
http://arxiv.org/abs/0911.3793
http://arxiv.org/cits/0911.3793
Gravity-Yang-Mills-Higgs unification by enlarging the gauge group

Thiemann Engle Han
http://arxiv.org/abs/0911.3433
http://arxiv.org/cits/0911.3433
Canonical path integral measures for Holst and Plebanski gravity. I. Reduced Phase Space Derivation

Percacci Narain
http://arxiv.org/abs/0911.0386
http://arxiv.org/cits/0911.0386
Renormalization Group Flow in Scalar-Tensor Theories. I

9. Jan 3, 2010

### atyy

Yes, just either one, as a representative of a possibly interesting new direction. I'd keep Freidel because it's the earlier, on the other hand you already have Freidel on the list, which would argue for Magnen et al.