Our picks for fourth quarter 2012 MIP (most important QG paper)

marcus

Cordial thanks! to Adpc, Atyy, Chronos, Demystifier, Devils, Erkant, Julcab12, Nonlinear, and Skydive Phil. It can be instructive to see what others have identified as especially significant research. I often find myself taking a second look at a paper others of us pick, to better understand its potential importance.

Here's how the votes currently stack up:

Four votes:

http://arxiv.org/abs/1212.5183
On the Architecture of Spacetime Geometry
Eugenio Bianchi, Robert C. Myers

http://arxiv.org/abs/1212.4060
Black Hole Entropy from complex Ashtekar variables
Ernesto Frodden, Marc Geiller, Karim Noui, Alejandro Perez

http://arxiv.org/abs/1211.2166
The spin connection of twisted geometry
Hal M. Haggard, Carlo Rovelli, Francesca Vidotto, Wolfgang Wieland

Two votes:

http://lanl.arxiv.org/abs/1212.1930
A "Helium Atom" of Space: Dynamical Instability of the Isochoric Pentahedron
Christopher E. Coleman-Smith, Berndt Müller

http://arxiv.org/abs/1211.7311
Pentahedral volume, chaos, and quantum gravity
Hal M. Haggard

http://arxiv.org/abs/1211.6269
The Matter Bounce Scenario in Loop Quantum Cosmology
Edward Wilson-Ewing

http://arxiv.org/abs/1211.1354
An Extension of the Quantum Theory of Cosmological Perturbations to the Planck Era
Ivan Agullo, Abhay Ashtekar, William Nelson

http://arxiv.org/abs/1211.0522
Horizon entanglement entropy and universality of the graviton coupling
Eugenio Bianchi

http://arxiv.org/abs/1210.4504
A new perspective on cosmology in Loop Quantum Gravity
Emanuele Alesci, Francesco Cianfrani

http://arxiv.org/abs/1210.0418
Interpretation of the triad orientations in loop quantum cosmology
Claus Kiefer, Christian Schell

Plus six that I didn't list here, each of which only got ONE vote, so far.

marcus

Keeping the first quarter 2013 list up to date in view of the upcoming MIP poll, here are a few Loop and allied papers of special interest. For compactness I've omitted the abstracts of papers listed earlier. 17 papers so far. The list is provisional and may be shortened.

http://arxiv.org/abs/1303.3576
Cosmology from Group Field Theory
Steffen Gielen, Daniele Oriti, Lorenzo Sindoni
(Submitted on 14 Mar 2013)
We identify a class of condensate states in the group field theory (GFT) approach to quantum gravity that can be interpreted as macroscopic homogeneous spatial geometries. We then extract the dynamics of such condensate states directly from the fundamental quantum GFT dynamics, following the procedure used in ordinary quantum fluids. The effective dynamics is a non-linear and non-local extension of quantum cosmology. We also show that any GFT model with a kinetic term of Laplacian type gives rise, in a semi-classical (WKB) approximation and in the isotropic case, to a modified Friedmann equation. This is the first concrete, general procedure for extracting an effective cosmological dynamics directly from a fundamental theory of quantum geometry.
5 pages

http://arxiv.org/abs/1303.2773
BTZ Black Hole Entropy in Loop Quantum Gravity and in Spin Foam Models
J.Manuel Garcia-Islas
(Submitted on 12 Mar 2013)
We present a comparison of the calculation of BTZ black hole entropy in loop quantum gravity and in spin foam models. We see that both give the same answer.
6 pages, 3 figures

http://arxiv.org/abs/1303.1687
Quantum states of the bouncing universe
Jean Pierre Gazeau, Jakub Mielczarek, Wlodzimierz Piechocki
(Submitted on 7 Mar 2013)
In this paper we study quantum dynamics of the bouncing cosmological model. We focus on the model of the flat Friedman-Robertson-Walker universe with a free scalar field. The bouncing behavior, which replaces classical singularity, appears due to the modification of general relativity along the methods of loop quantum cosmology. We show that there exist a unitary transformation that enables to describe the system as a free particle with Hamiltonian equal to canonical momentum. We examine properties of the various quantum states of the Universe: boxcar state, standard coherent state, and soliton-like state, as well as Schrödinger's cat states constructed from these states. Characteristics of the states such as quantum moments and Wigner functions are investigated. We show that each of these states have, for some range of parameters, a proper semiclassical limit fulfilling the correspondence principle. Decoherence of the superposition of two universes is described and possible interpretations in terms of triad orientation and Belinsky-Khalatnikov-Lifshitz conjecture are given. Some interesting features regarding the area of the negative part of the Wigner function have emerged.
18 pages, 19 figures

http://arxiv.org/abs/1303.0752
Inclusion of matter in inhomogeneous loop quantum cosmology
Daniel Martín-de Blas, Mercedes Martín-Benito, Guillermo A. Mena Marugán
(Submitted on 4 Mar 2013)
We study the hybrid quantization of the linearly polarized Gowdy T³ model with a massless scalar field with the same symmetries as the metric. For simplicity, we quantize its restriction to the model with local rotational symmetry. Using this hybrid approach, the homogeneous degrees of freedom of the geometry are quantized à la loop, leading to the resolution of the cosmological singularity. A Fock quantization is employed both for the matter and the gravitational inhomogeneities. Owing to the inclusion of the massless scalar field this system allows us to modelize flat Friedmann-Robertson-Walker cosmologies filled with inhomogeneities propagating in one direction, providing a perfect scenario to study the quantum back-reaction of the inhomogeneities on the polymeric homogeneous and isotropic background.
4 pages

http://arxiv.org/abs/1303.0195
Living in Curved Momentum Space
J. Kowalski-Glikman

http://arxiv.org/abs/1302.7142
Holonomy Operator and Quantization Ambiguities on Spinor Space
Etera R. Livine

http://arxiv.org/abs/1302.7037
Loop Quantization of Shape Dynamics
Tim Koslowski

http://arxiv.org/abs/1302.5265
The loop quantum gravity black hole
Rodolfo Gambini, Jorge Pullin

http://arxiv.org/abs/1302.3833
Loop Quantum Cosmology
Ivan Agullo, Alejandro Corichi

http://arxiv.org/abs/1302.1781
Self-Energy in the Lorentzian ERPL-FK Spin Foam Model of Quantum Gravity
Aldo Riello

http://arxiv.org/abs/1302.0724
Death and resurrection of the zeroth principle of thermodynamics
Hal M. Haggard, Carlo Rovelli

http://arxiv.org/abs/1302.0254
The pre-inflationary dynamics of loop quantum cosmology: Confronting quantum gravity with observations
Ivan Agullo, Abhay Ashtekar, William Nelson

http://arxiv.org/abs/1301.6210
Embedding loop quantum cosmology without piecewise linearity
Jonathan Engle

http://arxiv.org/abs/1301.5859
Hamiltonian spinfoam gravity
Wolfgang M. Wieland

http://arxiv.org/abs/1301.3480
Gauge networks in noncommutative geometry
Matilde Marcolli, Walter D. van Suijlekom

http://arxiv.org/abs/1301.2245
Quantum-Reduced Loop Gravity: Cosmology
Emanuele Alesci, Francesco Cianfrani

http://arxiv.org/abs/1301.1264
Inflation as a prediction of loop quantum cosmology
Linda Linsefors, Aurelien Barrau

nitsuj

Hmmm, My choice is #2 On the Architecture of Spacetime Geometry. It has the most promising title imo.

Sorry to have skewed the results

marcus

Thanks for registering your choice, nitsuJ--however you arrived at your decision, I think it's a good pick!
In preparation for the upcoming MIP poll, here are a few Loop and allied papers of special interest. For compactness I've omitted the abstracts of papers listed earlier. The list of 19 papers is provisional and may be shortened.

http://arxiv.org/abs/1303.4989
Loop Quantum Gravity and the The Planck Regime of Cosmology
Abhay Ashtekar
(Submitted on 20 Mar 2013)
The very early universe provides the best arena we currently have to test quantum gravity theories. The success of the inflationary paradigm in accounting for the observed inhomogeneities in the cosmic microwave background already illustrates this point to a certain extent because the paradigm is based on quantum field theory on the curved cosmological space-times. However, this analysis excludes the Planck era because the background space-time satisfies Einstein's equations all the way back to the big bang singularity. Using techniques from loop quantum gravity, the paradigm has now been extended to a self-consistent theory from the Planck regime to the onset of inflation, covering some 11 orders of magnitude in curvature. In addition, for a narrow window of initial conditions, there are departures from the standard paradigm, with novel effects, such as a modification of the consistency relation involving the scalar and tensor power spectra and a new source for non-Gaussianities. Thus, the genesis of the large scale structure of the universe can be traced back to quantum gravity fluctuations in the Planck regime. This report provides a bird's eye view of these developments for the general relativity community.
23 pages, 4 figures. Plenary talk at the Conference: Relativity and Gravitation: 100 Years after Einstein in Prague. To appear in the Proceedings to be published by Edition Open Access. Summarizes results that appeared in journal articles [2-13]

http://arxiv.org/abs/1303.4752
Imaginary action, spinfoam asymptotics and the 'transplanckian' regime of loop quantum gravity
Norbert Bodendorfer, Yasha Neiman
(Submitted on 19 Mar 2013)
It was recently noted that the on-shell Einstein-Hilbert action with York-Gibbons-Hawking boundary term has an imaginary part, proportional to the area of the codimension-2 surfaces on which the boundary normal becomes null. We extend this result to first-order formulations of gravity, by generalizing a previously proposed boundary term to closed boundaries. As a side effect, we settle the issue of the Holst modification vs. the Nieh-Yan density by demanding a well-defined variational principle. We then set out to find the imaginary action in the large-spin 4-simplex limit of the Lorentzian EPRL/FK spinfoam. It turns out that the spinfoam's effective action indeed has the correct imaginary part, but only if the Barbero-Immirzi parameter γ is set to ± i after the quantum calculation. An interpretation and a connection to other recent results is discussed. In particular, we propose that the large-spin limit of loop quantum gravity can be viewed as a high-energy 'transplanckian' regime.
22 pages, 5 figures

http://arxiv.org/abs/1303.4636
Spin foams
Jonathan Engle
(Submitted on 19 Mar 2013)
The spin foam framework provides a way to define the dynamics of canonical loop quantum gravity in a spacetime covariant way, by using a path integral over histories of quantum states which can be interpreted as 'quantum space-times'. This chapter provides a basic introduction to spin foams aimed principally at beginning graduate students and, where possible, at broader audiences.
32 pages, 14 figures, 2 tables, to appear as a chapter of "The Springer Handbook of Spacetime," edited by A. Ashtekar and V. Petkov (Springer-Verlag 2013)

http://arxiv.org/abs/1303.3576
Cosmology from Group Field Theory
Steffen Gielen, Daniele Oriti, Lorenzo Sindoni

http://arxiv.org/abs/1303.2773
BTZ Black Hole Entropy in Loop Quantum Gravity and in Spin Foam Models
J.Manuel Garcia-Islas

http://arxiv.org/abs/1303.0752
Inclusion of matter in inhomogeneous loop quantum cosmology
Daniel Martín-de Blas, Mercedes Martín-Benito, Guillermo A. Mena Marugán

http://arxiv.org/abs/1303.0195
Living in Curved Momentum Space
J. Kowalski-Glikman

http://arxiv.org/abs/1302.7142
Holonomy Operator and Quantization Ambiguities on Spinor Space
Etera R. Livine

http://arxiv.org/abs/1302.7037
Loop Quantization of Shape Dynamics
Tim Koslowski

http://arxiv.org/abs/1302.5265
The loop quantum gravity black hole
Rodolfo Gambini, Jorge Pullin

http://arxiv.org/abs/1302.3833
Loop Quantum Cosmology
Ivan Agullo, Alejandro Corichi

http://arxiv.org/abs/1302.1781
Self-Energy in the Lorentzian ERPL-FK Spin Foam Model of Quantum Gravity
Aldo Riello

http://arxiv.org/abs/1302.0724
Death and resurrection of the zeroth principle of thermodynamics
Hal M. Haggard, Carlo Rovelli

http://arxiv.org/abs/1302.0254
The pre-inflationary dynamics of loop quantum cosmology: Confronting quantum gravity with observations
Ivan Agullo, Abhay Ashtekar, William Nelson

http://arxiv.org/abs/1301.6210
Embedding loop quantum cosmology without piecewise linearity
Jonathan Engle

http://arxiv.org/abs/1301.5859
Hamiltonian spinfoam gravity
Wolfgang M. Wieland

http://arxiv.org/abs/1301.3480
Gauge networks in noncommutative geometry
Matilde Marcolli, Walter D. van Suijlekom

http://arxiv.org/abs/1301.2245
Quantum-Reduced Loop Gravity: Cosmology
Emanuele Alesci, Francesco Cianfrani

http://arxiv.org/abs/1301.1264
Inflation as a prediction of loop quantum cosmology
Linda Linsefors, Aurelien Barrau

ftr

It would be nice if the voters justified their choice. My criteria are that the paper should explain the connection of quantum mechanics to general relativity in an unambiguous way. And if GR is a quantum phenomenon what does that say about QM of matter (can it shed some light).

It is not clear to me if any of the papers does that, but they express GR (without matter) in a statistical manner with emphasis on black hole entropy which seems like a very narrow goal. Even LQC looks very artificial.

At least in string theory you can see the connection much better.

atyy

String theory is forbidden. This is the losers' semi:)

BTW, Myers is a string theorist.

Myers gave a talk at the Simons meeting Quantum Entanglement: from Quantum Matter to String Theory. Here are his slides: http://qpt.physics.harvard.edu/simons/Myers.pdf.

marcus

Agreed! I sometimes do mention why I personally think certain of the papers are likely to prove especially important. But I usually do that in other threads because in the poll I'm really most interested in learning what other people think.
Here, for the upcoming first quarter 2013 MIP poll, I've listed 20 Loop and allied QG papers of special interest. For compactness I've omitted the abstracts shown earlier. The list is provisional and may be shortened.

http://arxiv.org/abs/1303.6157
Loop quantum dynamics of the gravitational collapse
Yaser Tavakoli, Joao Marto, Andrea Dapor
(Submitted on 25 Mar 2013)
We consider a quantum description for a spherically symmetric gravitational collapse of a massless scalar field. The effective scenario from loop quantum gravity is applied to a homogeneous interior spacetime. The classical singularity that arises at the final stage of our collapsing system is resolved and replaced by a quantum bounce. Our main purpose is to investigate the evolution of trapped surfaces during the collapse in semiclassical regime. We show that, in this regime, there exists a threshold scale below which no horizon can form as collapse evolves towards the bounce. By employing the matching conditions at the boundary shell, quantum effects are carried out to the exterior region, leading to an improved Vaidya geometry. In addition, the effective mass loss emerging in this model predicts an outward energy flux from the interior quantum geometry regime.
11 pages, 5 figures

http://arxiv.org/abs/1303.5612
A Gravitational Entropy Proposal
Timothy Clifton, George F R Ellis, Reza Tavakol
(Submitted on 22 Mar 2013)
We propose a thermodynamically motivated measure of gravitational entropy based on the Bel-Robinson tensor, which has a natural interpretation as the effective super-energy-momentum tensor of free gravitational fields. The specific form of this measure differs depending on whether the gravitational field is Coulomb-like or wave-like, and reduces to the Bekenstein-Hawking value when integrated over the interior of a Schwarzschild black hole. For scalar perturbations of a Robertson-Walker geometry we find that the entropy goes like the Hubble weighted anisotropy of the gravitational field, and therefore increases as structure formation occurs. This is in keeping with our expectations for the behaviour of gravitational entropy in cosmology, and provides a thermodynamically motivated arrow of time for cosmological solutions of Einstein's field equations. It is also in keeping with Penrose's Weyl curvature hypothesis.
17 pages

http://arxiv.org/abs/1303.4989
Loop Quantum Gravity and the The Planck Regime of Cosmology
Abhay Ashtekar

http://arxiv.org/abs/1303.4752
Imaginary action, spinfoam asymptotics and the 'transplanckian' regime of loop quantum gravity
Norbert Bodendorfer, Yasha Neiman

http://arxiv.org/abs/1303.4636
Spin foams
Jonathan Engle

http://arxiv.org/abs/1303.3576
Cosmology from Group Field Theory
Steffen Gielen, Daniele Oriti, Lorenzo Sindoni

http://arxiv.org/abs/1303.2773
BTZ Black Hole Entropy in Loop Quantum Gravity and in Spin Foam Models
J.Manuel Garcia-Islas

http://arxiv.org/abs/1303.0752
Inclusion of matter in inhomogeneous loop quantum cosmology
Daniel Martín-de Blas, Mercedes Martín-Benito, Guillermo A. Mena Marugán

http://arxiv.org/abs/1303.0195
Living in Curved Momentum Space
J. Kowalski-Glikman

http://arxiv.org/abs/1302.7142
Holonomy Operator and Quantization Ambiguities on Spinor Space
Etera R. Livine

http://arxiv.org/abs/1302.5265
The loop quantum gravity black hole
Rodolfo Gambini, Jorge Pullin

http://arxiv.org/abs/1302.3833
Loop Quantum Cosmology
Ivan Agullo, Alejandro Corichi

http://arxiv.org/abs/1302.1781
Self-Energy in the Lorentzian ERPL-FK Spin Foam Model of Quantum Gravity
Aldo Riello

http://arxiv.org/abs/1302.0724
Death and resurrection of the zeroth principle of thermodynamics
Hal M. Haggard, Carlo Rovelli

http://arxiv.org/abs/1302.0254
The pre-inflationary dynamics of loop quantum cosmology: Confronting quantum gravity with observations
Ivan Agullo, Abhay Ashtekar, William Nelson

http://arxiv.org/abs/1301.6210
Embedding loop quantum cosmology without piecewise linearity
Jonathan Engle

http://arxiv.org/abs/1301.5859
Hamiltonian spinfoam gravity
Wolfgang M. Wieland

http://arxiv.org/abs/1301.3480
Gauge networks in noncommutative geometry
Matilde Marcolli, Walter D. van Suijlekom

http://arxiv.org/abs/1301.2245
Quantum-Reduced Loop Gravity: Cosmology
Emanuele Alesci, Francesco Cianfrani

http://arxiv.org/abs/1301.1264
Inflation as a prediction of loop quantum cosmology
Linda Linsefors, Aurelien Barrau