Planckian Birth of a Quantum de Sitter Universe

Ambjørn, J.; Görlich, Andrzej; Jurkiewicz, J.; Loll, R.

doi:10.1103/physrevlett.100.091304

Cited by 147 publications

(278 citation statements)

References 12 publications

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“…where i denotes (integer) lattice time, N 4 the total number of four-simplices and N 3 (i) the number of tetrahedra at time i [31,32], and s 0 is a constant. 10 Can the functional form of the expectation value found in (26) be obtained directly from an action principle?…”

Section: The Effective Actionmentioning

confidence: 99%

Quantum Gravity via Causal Dynamical Triangulations

Ambjørn¹,

Görlich²,

Jurkiewicz³

et al. 2014

Springer Handbook of Spacetime

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Abstract"Causal Dynamical Triangulations" (CDT) represent a lattice regularization of the sum over spacetime histories, providing us with a non-perturbative formulation of quantum gravity. The ultraviolet fixed points of the lattice theory can be used to define a continuum quantum field theory, potentially making contact with quantum gravity defined via asymptotic safety. We describe the formalism of CDT, its phase diagram, and the quantum geometries emerging from it. We also argue that the formalism should be able to describe a more general class of quantum-gravitational models of Hořava-Lifshitz type.

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Section: The Effective Actionmentioning

confidence: 99%

Quantum Gravity via Causal Dynamical Triangulations

Ambjørn¹,

Görlich²,

Jurkiewicz³

et al. 2014

Springer Handbook of Spacetime

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“…Many steps in this construction must be formulated in terms of observables, which in a diffeomorphism-invariant theory are notoriously hard to come by. In this article, we focus on a particular class of observables, involving gravitational Wilson loops, and a particular candidate theory of nonperturbative quantum gravity, causal dynamical triangulations (CDT) [1][2][3]. In this theory, the challenges mentioned above pose themselves in very concrete terms and can also be addressed concretely, including the use of powerful numerical methods.…”

Section: Introductionmentioning

confidence: 99%

“…Only a few observables are known in CDT quantum gravity and have been investigated quantitatively, including the volume profile of the dynamically generated quantum universe [3,7], as well as its Hausdorff and spectral dimensions [2,8]. Note that all of them involve measurements of lengths and volumes.…”

Section: Introductionmentioning

confidence: 99%

“…VI the discussion focuses on a specific class of Wilson loops, associated with the world line of a point particle, and their concrete implementation in the full, nonperturbative CDT path integral. After a brief description 3 We note in passing that the analogous averaging problem in classical general relativity has not been resolved (see, for example, [15]). 4 Theoretical arguments were put forward in a different formulation of lattice gravity based on Regge calculus, promoting large Wilson loops as carriers of nonperturbative information [16].…”

Section: Introductionmentioning

confidence: 99%

“…As explained earlier, they should also provide us with a notion of averaging or coarse-graining, 3 to allow for a comparison with ordinary macroscopic curvature in a semiclassical limit. We do not know a priori whether such observables exist, and we are not aware of an explicit construction in any approach to nonperturbative quantum gravity.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Wilson loops in nonperturbative quantum gravity

Ambjørn¹,

Görlich²,

Jurkiewicz³

et al. 2015

Phys. Rev. D

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By explicit construction, we show that one can in a simple way introduce and measure gravitational holonomies and Wilson loops in lattice formulations of nonperturbative quantum gravity based on (causal) dynamical triangulations. We use this setup to investigate a class of Wilson line observables associated with the world line of a point particle coupled to quantum gravity, and deduce from their expectation values that the underlying holonomies cover the group manifold of SO(4) uniformly.

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Deriving spacetime from first principles

Ambjørn

Jurkiewicz

Loll³

2010

Ann. Phys.

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Causal Dynamical Triangulation is a back-to-basics approach to nonperturbative, background-independent quantum gravity, which relies on few ingredients and initial assumptions, has few free parameters andcrucially -is amenable to numerical simulations. After putting the approach in context, we briefly describe its set-up and highlight some of its major, and sometimes unexpected findings. Prominent among them is the dynamical generation of a classical de Sitter universe from Planckian quantum fluctuations. Quantum gravity -back to basicsMany fundamental questions about the nature of space, time and gravitational interactions are not answered by the classical theory of general relativity, but lie in the realm of the still searched-for theory of quantum gravity: What is the quantum theory underlying general relativity, and what does it say about the quantum origins of space, time and our universe? What is the microstructure of spacetime at the shortest scale usually considered, the Planck scale Pl = 10 −35 m, and what are the relevant degrees of freedom determining the dynamics there? Are they the geometric dynamical variables of the classical theory (or some short-scale version thereof), or do they also include the topology and/or dimensionality of spacetime, quantities that classically are considered fixed? Can the dynamics of these microscopic degrees of freedom explain the observed large-scale structure of our own universe, which resembles a de Sitter universe at late times? Do notions like "space", "time" and "causality" remain meaningful on short scales, or are they merely macroscopically emergent from more fundamental, underlying Planck-scale principles?Despite considerable efforts over the last several decades, it has so far proven difficult to come up with a consistent and quantitative theory of quantum gravity, which would be able to address and answer such questions [1]. In the process, researchers in high-energy theory have been led to consider ever more radical possibilities in order to resolve this apparent impasse, from postulating the existence of extra structures unobservable at low energies to invoking ill-defined ensembles of multiverses and anthropic principles [2]. A grand unified picture has quantum gravity inextricably linked with the quantum dynamics of the three other known fundamental interactions, which requires a new unifying principle. Superstring theory is an example of such a framework, which needs the existence of an as yet unseen symmetry (supersymmetry) and ingredients (strings, branes, fundamental scalar fields). Loop quantum gravity, a non-unified approach, postulates the existence of certain fundamental quantum variables of Wilson loop type. Even more daring souls contemplate -inspired by quantum-gravitational problems -the abandonment of locality [3] or substituting quantum mechanics by a more fundamental, deterministic theory [4]. *

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Planckian Birth of a Quantum de Sitter Universe

Cited by 147 publications

References 12 publications

Quantum Gravity via Causal Dynamical Triangulations

Quantum Gravity via Causal Dynamical Triangulations

Wilson loops in nonperturbative quantum gravity

Deriving spacetime from first principles

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