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Quantum Spacetime and the Universe at the Big Bang, Vanishing Interactions and Fading Degrees of Freedom

Abstract

As discussed in Bahns et al. (2015) fundamental physical principles suggests that, close to cosmological singularities, the effective Planck length diverges, hence a “quantum point” becomes infinitely extended. We argue that, as a consequence, at the origin of times spacetime might reduce effectively to a single point and interactions disappear. This conclusion is supported by converging evidences in two different approaches to interacting quantum fields on Quantum Spacetime: (1) as the Planck length diverges, the field operators evaluated at a “quantum point” converge to zero, and so do the lowest order expressions for interacting fields in the Yang Feldman approach; (2) in the same limit, we find convergence of the interacting vacuum to the free one at all perturbative orders. The latter result is obtained using the adaptation, performed in Doplicher et al. (2020), of the methods of perturbative Algebraic Quantum Field Theory to Quantum Spacetime, through a novel picture of the effective Lagrangian, which maintains the ultraviolet finiteness of the perturbation expansion and allows one to prove also the existence of the adiabatic limit. It remains an open question whether the S matrix itself converges to unity and whether the limit in which the effective Planck length diverges is a unique initial condition or an unreachable limit, and only different asymptotics matter.

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Acknowledgments

G.M. is partially supported by the European Research Council Advanced Grant 669240 QUEST, the MIUR Excellence Department Project awarded to the Department of Mathematics, University of Rome Tor Vergata, CUP E83C18000100006, the INdAM-GNAMPA and the University of Rome Tor Vergata funding scheme “Beyond Borders”, CUP E84I19002200005.

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Open access funding provided by Università degli Studi di Roma Tor Vergata within the CRUI-CARE Agreement.

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Correspondence to Gerardo Morsella.

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Doplicher, S., Morsella, G. & Pinamonti, N. Quantum Spacetime and the Universe at the Big Bang, Vanishing Interactions and Fading Degrees of Freedom. Math Phys Anal Geom 23, 46 (2020). https://doi.org/10.1007/s11040-020-09369-9

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  • DOI: https://doi.org/10.1007/s11040-020-09369-9

Keywords

  • Quantum spacetime
  • Noncommutative field theories
  • Evolution of the Universe
  • Perturbation theory
  • Quantum cosmology

Mathematics Subject Classification (2010)

  • 81T75
  • 83C65
  • 81T15
  • 81R15