Cosmological evolution as squeezing: a toy model for group field cosmology

Adjei, Eugene; Gielen, Steffen; Wieland, Wolfgang

doi:10.1088/1361-6382/aaba11

Cited by 29 publications

(74 citation statements)

References 46 publications

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“…We refer to Refs. [62,63] where this point was further explored. 16 In the given picture, the cosmological dynamics expressed by the expansion of the volume is vastly driven by a growing occupation number [60,64].…”

Section: A Recovery Of Friedmann-like Dynamics and Bouncing Solutionsmentioning

confidence: 99%

Group Field Theory Condensate Cosmology: An Appetizer

Pithis

Sakellariadou

2019

Universe

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This contribution is an appetizer to the relatively young and fast evolving approach to quantum cosmology based on group field theory condensate states. We summarize the main assumptions and pillars of this approach which has revealed new perspectives on the long-standing question of how to recover the continuum from discrete geometric building blocks. Among others, we give a snapshot of recent work on isotropic cosmological solutions exhibiting an accelerated expansion, a bounce where anisotropies are shown to be under control and inhomogeneities with an approximately scaleinvariant power spectrum. Finally, we point to open issues in the condensate cosmology approach.Most important part of doing physics is the knowledge of approximation.Lev Davidovich Landau * andreas.pithis@kcl.ac.uk † mairi.sakellariadou@kcl.ac.uk 1 The introduction of discrete structures can be motivated to bypass the issue of perturbative non-renormalizability of GR within the continuum path integral formulation. Alternative points of view of dealing with this issue would be to assume the existence of a nonperturbative (i.e. interacting) fixed point for gravity in the UV as done by the asymptotic safety program [7] or to increase the amount of symmetries as compared to GR and QFT with the aim to regain perturbative renormalizability as proposed by string theory [8].Yet another view, as presented by non-commutative geometry, is that above the Planck scale the concept of geometry collapses and spacetime is replaced by a non-commutative manifold [9].arXiv:1904.00598v2 [gr-qc] 13 Jun 2019 4 Notice that by attributing an additional combinatorial degree of freedom named color to the fields, one can guarantee that the terms of the perturbative expansion are free of topological pathologies [38]. 5 A detailed discussion on the subtle differences in between the Fock space of GFT and the kinematical Hilbert space of LQG, which are mostly related to the absence of the so-called cylindrical consistency and equivalence in the former, is found in Ref. [42]. 6 The assumption of bosonic statistics is crucial for the condensate cosmology program where spacetime is thought to arise from a GFT condensate. To justify this choice of statistics from a fundamental point of view is an open problem, see Ref.[42] for a discussion and Refs. [38,43] for explorations into other statistics. 7 We refer e.g. to Appendix C of Ref.[32] for an extensive discussion of this matter for the case of the volume operator.

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Section: A Recovery Of Friedmann-like Dynamics and Bouncing Solutionsmentioning

confidence: 99%

Group Field Theory Condensate Cosmology: An Appetizer

Pithis

Sakellariadou

2019

Universe

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“…As shown in the following this leads to three algebraic conditions, thus leaving one integration constant undetermined. 18 In fact, globally, f (χ) itself is determined only up to a linear term in χ, since χ = ∇ µ u µ and the action (2.1) is defined up to boundary terms. We can fix such underdeterminacy by further requiring that f (χ) respects the symmetry of the dynamics under χ → −χ, i.e.…”

Section: Peak Expansion Ratementioning

confidence: 99%

“…Group field theory provides a second quantized reformulation of loop quantum gravity [15]; in this approach, cosmological dynamics is emergent and can be obtained by considering a particular class of quantum states (condensates) encoding data that are associated to homogeneous geometries [16,17]. The background dynamics obtained from group field theory condensates [4] generalizes the effective dynamics of LQC, which can indeed be recovered as a special case (see also [18,19]). In this work we determine the multi-valued function f corresponding to such a background evolution and analyze its properties in detail.…”

Section: Introductionmentioning

confidence: 99%

Limiting curvature mimetic gravity for group field theory condensates

Cesare

2019

Phys. Rev. D

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Nonsingular bouncing cosmologies are realized in limiting curvature mimetic gravity by means of a multivalued potential f ( φ) depending on the d'Alembertian of a scalar field φ. We determine the functional form of such a potential so as to exactly reproduce the cosmological background dynamics obtained in the group field theory approach to quantum gravity. The original proposal made by Chamseddine and Mukhanov [JCAP 1703[JCAP , no. 03, 009 (2017], which was shown to lead to a background dynamics reproducing the effective dynamics of loop quantum cosmology, is here recovered as a particular case for some specific choices of the parameters of our model. We also clarify some issues related to the multi-valuedness of the function f , showing in particular that its functional form can be unambiguously reconstructed by imposing appropriate matching conditions at the branching points.

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“…In [19], a toy model of group field theory has been derived that produces bouncing cosmological dynamics for the number observable of certain microscopic degrees of freedom.…”

Section: Model Of Group Field Theorymentioning

confidence: 99%

Equivalence of Models in Loop Quantum Cosmology and Group Field Theory

2019

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The paradigmatic models often used to highlight cosmological features of loop quantum gravity and group field theory are shown to be equivalent, in the sense that they are different realizations of the same model given by harmonic cosmology. The loop version of harmonic cosmology is a canonical realization, while the groupfield version is a bosonic realization. The existence of a large number of bosonic realizations suggests generalizations of models in group field cosmology.

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Cosmological evolution as squeezing: a toy model for group field cosmology

Cited by 29 publications

References 46 publications

Group Field Theory Condensate Cosmology: An Appetizer

Group Field Theory Condensate Cosmology: An Appetizer

Limiting curvature mimetic gravity for group field theory condensates

Equivalence of Models in Loop Quantum Cosmology and Group Field Theory

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