Dark energy in the swampland

Lavinia Heisenberg, Matthias Bartelmann, Robert Brandenberger, and Alexandre Refregier
Phys. Rev. D 98, 123502 – Published 6 December 2018

Abstract

In this article, we study the implications of string swampland criteria for dark energy in view of ongoing and future cosmological observations. If string theory should be the ultimate quantum gravity theory, there is evidence that exact de Sitter solutions with a positive cosmological constant cannot describe the fate of the late-time universe. Even though cosmological models with dark energy given by a scalar field π evolving in time are not in direct tension with string theory, they have to satisfy the swampland criteria |Δπ|<dO(1) and |V|/V>cO(1), where V is the scalar field potential. In view of the restrictive implications that the swampland criteria have on dark energy, we investigate the accuracy needed for future observations to tightly constrain standard dark-energy models. We find that current 3σ constraints with c1.35 are still well in agreement with the string swampland criteria. However, stage-4 surveys such as Euclid, LSST, and DESI, tightly constraining the equation of state w(z), will start putting surviving quintessence models into tensions with the string swampland criteria by demanding c<0.4. We further investigate whether any idealized futuristic survey will ever be able to give a decisive answer to the question whether the cosmological constant would be preferred over a time-evolving dark-energy model within the swampland criteria. Hypothetical surveys with a reduction in the uncertainties by a factor of 20 compared to Euclid would be necessary to reveal strong tension between quintessence models obeying the string swampland criteria and observations by pushing the allowed values down to c<0.1. In view of such perspectives, there will be fundamental observational limitations with future surveys.

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  • Received 7 September 2018

DOI:https://doi.org/10.1103/PhysRevD.98.123502

© 2018 American Physical Society

Physics Subject Headings (PhySH)

Gravitation, Cosmology & Astrophysics

Authors & Affiliations

Lavinia Heisenberg1,*, Matthias Bartelmann2,†, Robert Brandenberger3,‡, and Alexandre Refregier4,§

  • 1Institute for Theoretical Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland
  • 2Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik, 69120 Heidelberg, Germany
  • 3Physics Department, McGill University, Montreal, Quebec H3A 2T8, Canada
  • 4Institute for Particle Physics and Astrophysics, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland

  • *lavinia.heisenberg@phys.ethz.ch
  • bartelmann@uni-heidelberg.de
  • rhb@hep.physics.mcgill.ca
  • §alexandre.refregier@phys.ethz.ch

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Issue

Vol. 98, Iss. 12 — 15 December 2018

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