Which of these first quarter 2008 papers/presentations do you expect to contribute most to future research?(adsbygoogle = window.adsbygoogle || []).push({});

1. http://cift.fuw.edu.pl/users/kostecki/zakopane08/rovelli.pdf

Looppy & Foammy: at long last, falling in love

Carlo Rovelli

This is Rovelli's report at the March 2008 Zakopane Workshop on the current state of LQG and Spinfoam research, and in particular their recent convergence on consistent results.

2. http://arxiv.org/abs/0802.1783

On Spectral Triples in Quantum Gravity I

Johannes Aastrup, Jesper M. Grimstrup, Ryszard Nest

84 pages, 8 figures

(Submitted on 13 Feb 2008)

"This paper establishes a link between Noncommutative Geometry and canonical quantum gravity. A semi-finite spectral triple over a space of connections is presented. The triple involves an algebra of holonomy loops and a Dirac type operator which resembles a global functional derivation operator. The interaction between the Dirac operator and the algebra reproduces the Poisson structure of General Relativity. Moreover, the associated Hilbert space corresponds, up to a discrete symmetry group, to the Hilbert space of diffeomorphism invariant states known from Loop Quantum Gravity. Correspondingly, the square of the Dirac operator has, in terms of canonical quantum gravity, the form of a global area-squared operator. Furthermore, the spectral action resembles a partition function of Quantum Gravity. The construction is background independent and is based on an inductive system of triangulations. This paper is the first of two papers on the subject."

Part II of the AGN paper, submitted simultaneously with Part I, is

http://arxiv.org/abs/0802.1784

On Spectral Triples in Quantum Gravity II

3. http://arxiv.org/abs/0802.4274

Loop Quantum Cosmology: Effective theories and oscillating universes

Martin Bojowald, Reza Tavakol

24 pages, 3 figures, Chapter contributed to:Beyond the Big Bang, edited by R. Vaas (Springer Verlag, 2008)

"Despite its great successes in accounting for the current observations, the so called 'standard' model of cosmology faces a number of fundamental unresolved questions. Paramount among these are those relating to the nature of the origin of the universe and its early evolution. Regarding the question of origin, the main difficulty has been the fact that within the classical general relativistic framework, the 'origin' is almost always a singular event at which the laws of physics break down, thus making it impossible for such an event, or epochs prior to it, to be studied. Recent studies have shown that Loop Quantum Cosmology may provide a non-singular framework where these questions can be addressed. The crucial role here is played by quantum effects, i.e. corrections to the classical equations of motion, which are incorporated in effective equations employed to develop cosmological scenarios.

In this chapter we shall consider the three main types of quantum effects expected to be present within such a framework and discuss some of their consequences for the effective equations. In particular we discuss how such corrections can allow the construction of non-singular emergent scenarios for the origin of the universe, which are past-eternal, oscillating and naturally emerge into an inflationary phase. These scenarios provide a physically plausible picture for the origin and early phases of the universe, which is in principle testable. We pay special attention to the interplay between these different types of correction terms. Given the absence, so far, of a complete derivation of such corrections in general settings, it is important to bear in mind the questions of consistency and robustness of scenarios based on partial inclusion of such effects."

Amazon is now taking advance orders on the new book Beyond the Big Bang, in which this is a chapter

https://www.amazon.com/Beyond-Big-Bang-Prospects-Collection/dp/3540714227

4. http://arxiv.org/abs/0803.2546

Primordial Entropy Production and Lambda-driven Inflation from Quantum Einstein Gravity

Alfio Bonanno, Martin Reuter

12 pages, 4 figures, IGCG-07 Pune

(Submitted on 17 Mar 2008)

"We review recent work on renormalization group (RG) improved cosmologies based upon a RG trajectory of Quantum Einstein Gravity (QEG) with realistic parameter values. In particular we argue that QEG effects can account for the entire entropy of the present Universe in the massless sector and give rise to a phase of inflationary expansion. This phase is a pure quantum effect and requires no classical inflaton field."

5. http://arxiv.org/abs/0803.2926

Matrix universality of gauge field and gravitational dynamics

Lee Smolin

21 pages,

(Submitted on 20 Mar 2008)

"A simple cubic matrix model is presented, which has truncations that, it is argued, lead at the classical level to a variety of theories of gauge fields and gravity. These include Yang-Mills theories and background independent theories of connections. The latter includes Chern-Simons theory in d=3, and BF theory and general relativity in d=4. General relativity coupled to Yang-mills theory for any SU(N) may also arise from quantum corrections.

On the basis of these results we conjecture that there are large universality classes of cut-off gauge and gravity theories, connected by transformations that mix up local and spacetime symmetries. If our universe is described by one of these theories then the question of the choice of the laws of physics is to a large extent subsumed in the problem of the choice of initial conditions in cosmology."

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