Consistent initial conditions for early modified gravity in effective field theory

Physical review. D/Physical review. D., vol. 112

Abstract

Precise initial conditions (ICs) are crucial for accurate computation in cosmological perturbation theory. We derive the consistent ICs for Horndeski theory in the effective field theory (EFT) approach, assuming constant EFT functions at early times. We implement the ICs into the public Boltzmann code eftcamb, and demonstrate that the expected early-time behavior of perturbations and Weyl potential can be obtained with theory-consistent modified gravity (MG) ICs. We identify significant deviations when comparing cosmic microwave background angular power spectra in MG models obtained with consistent MG ICs versus inconsistent GR ICs. Our findings underline the importance of using accurate, theory-consistent MG ICs to ensure robust cosmological constraints on early MG models.

Authors 5

1. Jiaming Pan corresponding

   University of Michigan

   Affiliation as printed

   University of Michigan

   Department of Physics and Leinweber Center for Theoretical Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109, USA

2. Mengxiang Lin

   University of Pennsylvania

   Affiliation as printed

   University of Pennsylvania

   Center for Particle Cosmology, Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA

3. Gen Ye Aachen Institute Lorentz

   Leiden University

   Affiliation as printed

   Leiden University

   Institute Lorentz, Leiden University, PO Box 9506, Leiden 2300 RA, The Netherlands

4. Marco Raveri

   Istituto Nazionale di Fisica Nucleare · Istituto Nazionale di Fisica Nucleare, Sezione di Genova · University of Genoa

   Affiliation as printed

   INFN

   University of Genova

   Department of Physics and INFN, University of Genova, Via Dodecaneso 33, 16146, Italy

5. Alessandra Silvestri Aachen Institute Lorentz

   Leiden University

   Affiliation as printed

   Leiden University

   Institute Lorentz, Leiden University, PO Box 9506, Leiden 2300 RA, The Netherlands