Regge Gravity From Spinfoams

Magliaro, Elena; Perini, Claudio

doi:10.1142/s0218271813500016

Cited by 27 publications

(37 citation statements)

References 69 publications

(186 reference statements)

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“…In this article we calculate the asymptotic behaviour of the amplitude of a 4-simplex for both the DL model as well as the new model proposed in [20]. We find first that the DL model's asymptotics turn out to be the same as the EPRL-FK model [21][22][23][24][25][26][27][28][29][30], as was expected. Next, we study the asymptotics of the new model and find that due to non-trivial cancellations on-shell, it has the same 1st order behaviour, giving Regge Calculus [31].…”

Section: Introductionsupporting

confidence: 61%

Simpler way of imposing simplicity constraints

Banburski

Chen

2016

Phys. Rev. D

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We investigate a way of imposing simplicity constraints in a holomorphic Spin Foam model that we recently introduced. Rather than imposing the constraints on the boundary spin network, as is usually done, one can impose the constraints directly on the Spin Foam propagator. We find that the two approaches have the same leading asymptotic behaviour, with differences appearing at higher order. This allows us to obtain a model that greatly simplifies calculations, but still has Regge Calculus as its semi-classical limit. arXiv:1512.05331v1 [gr-qc]

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Section: Introductionsupporting

confidence: 61%

Simpler way of imposing simplicity constraints

Banburski

Chen

2016

Phys. Rev. D

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“…This symmetry is, however, broken in the 4d version of the theory [36,37]. Since the large j-limit of the EPRL-FK spin foam model is dominated by the Regge action [23,24,38], one would expect the same breaking to arise in spin foam quantum gravity in some form. This has been demonstrated for the large j-limit of the symmetryrestricted spin foam state sum [19], and we find its effect again here in the analysis of the RG flow.…”

Section: Diffeomorhism Symmetry In the Path Integralmentioning

confidence: 99%

Numerical Evidence for a Phase Transition in 4D Spin-Foam Quantum Gravity

2016

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Building on recent advances in defining Wilsonian renormalization group (RG) flows, and the notion of scales in particular, for background-independent theories, we present a first investigation of the renormalization of the 4D spin-foam path integral for quantum gravity, both analytically and numerically. Focusing on a specific truncation of the model using a hypercubic lattice, we compute the RG flow and find strong indications for a phase transition, as well as an interesting interplay between the different observed phases and the (broken) diffeomorphism symmetry of the model. Most notably, it appears that the critical point between the phases, which is a fixed point of the RG flow, is precisely where broken diffeomorphism symmetry is restored, which suggests that it might allow us to define a continuum limit of the quantum gravity theory.

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“…The recent studies of spinfoam asymptotics have made a significant progress on understanding the semiclassical limit of Loop Quantum Gravity (LQG) (see e.g. [1][2][3][4][5][6]) 1 . It has been understood that at least at the discrete level, classical 4d geometry emerges from spinfoam amplitude in the regime that the spins j f are uniformly large.…”

Section: Introductionmentioning

confidence: 99%

“…Although there has been earlier semiclassical analysis taking into account of the spin-sum (e.g. [4,6,14]), it seems to us that a sufficient understanding of the spin-sum in spinfoam amplitude still hasn't been achieved yet. One of the mysteries of the spin-sum comes from the dual role played by the spin j in the spinfoam amplitude.…”

Section: Introductionmentioning

confidence: 99%

Spinfoams near a classical curvature singularity

Han

Zhang

2016

Phys. Rev. D

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Abstract:We apply the technique of spinfoam to study the space-time which, classically, contains a curvature singularity. We derive from the full covariant Loop Quantum Gravity (LQG) that the region near curvature singularity has to be of strong quantum gravity effect. We show that the spinfoam configuration describing the near-singularity region has to be of small spins j, in order that its contribution to the full spinfoam amplitude is nontrivial. The spinfoams in low and high curvature regions of the space-time may be viewed as in two different phases of covariant LQG. There should be a phase transition as the space-time described by spinfoam becomes more and more curved. A candidate of order parameter is proposed for understanding the phase transition. Moreover, we also analyze the spinspin correlation function of spinfoam, and show the correlation is of long-range in the low curvature phase. This work is a first step toward understanding the physics of black hole and early universe from the full covariant LQG theory.

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Regge Gravity From Spinfoams

Cited by 27 publications

References 69 publications

Simpler way of imposing simplicity constraints

Simpler way of imposing simplicity constraints

Numerical Evidence for a Phase Transition in 4D Spin-Foam Quantum Gravity

Spinfoams near a classical curvature singularity

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