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Lattice Simulations of Non-minimally Coupled Scalar Fields in the Jordan Frame

by Daniel G. Figueroa, Adrien Florio, Toby Opferkuch, and Ben A. Stefanek

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Submission summary

Authors (as registered SciPost users): Toby Opferkuch
Submission information
Preprint Link: scipost_202209_00065v3  (pdf)
Date accepted: 2023-06-01
Date submitted: 2023-04-04 23:04
Submitted by: Opferkuch, Toby
Submitted to: SciPost Physics
Ontological classification
Academic field: Physics
  • Gravitation, Cosmology and Astroparticle Physics
  • High-Energy Physics - Phenomenology
Approaches: Theoretical, Computational, Phenomenological


The presence of scalar fields with non-minimal gravitational interactions of the form $\xi |\phi|^2 R$ may have important implications for the physics of the early universe. We propose a procedure to solve the dynamics of non-minimally coupled scalar fields directly in the Jordan frame, where the non-minimal couplings are maintained explicitly. Our algorithm can be applied to lattice simulations that include minimally coupled fields and an arbitrary number of non-minimally coupled scalars, with the expansion of the universe sourced by all fields present. This includes situations when the dynamics become fully inhomogeneous, fully non-linear (due to e.g. backreaction or mode rescattering effects), and/or when the expansion of the universe is dominated by non-minimally coupled species. As an example, we study geometric preheating with a non-minimally coupled scalar spectator field when the inflaton oscillates following the end of inflation.

Published as SciPost Phys. 15, 077 (2023)

Author comments upon resubmission

Dear Editor and Referees,

Thank you for the positive comments. Please see the list of changes made to the manuscript to better incorporate the previous reply to the referees. These changes include an expanded introduction, a more detailed discussion of the results (including reference to figure 3), and finally inclusion of the frame equivalence issues in the case of initial conditions driven by quantum fluctuations.

List of changes

- Lengthened the second last paragraph of the introduction (bottom of page 2), to explain cases where the conformal mapping between the Jordan and Einstein frames is not valid.
- Lengthened the paragraph beginning at the end of page 11 discussing the results of the geometric preheating model. Here a thorough discussion of the power spectrum is included.
- Added a paragraph at the bottom of page 13 beginning with``Before turning to the evolution''. Here we discuss the role of the quartic in modifying the resulting power spectrum.
- Significant modifications of the first and the final paragraph of the introduction to better include a discussion of the frame equivalence.

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