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Publication . Article . Preprint . 2015

MULTIMODECODE: an efficient numerical solver for multifield inflation

Layne C. Price; Jonathan Frazer; Jiajun Xu; Hiranya V. Peiris; Richard Easther;
Open Access
Published: 02 Mar 2015 Journal: Journal of Cosmology and Astroparticle Physics, volume 2,015, pages 5-5 (eissn: 1475-7516, Copyright policy )
Publisher: IOP Publishing

We present MultiModeCode, a Fortran 95/2000 package for the numerical exploration of multifield inflation models. This program facilitates efficient Monte Carlo sampling of prior probabilities for inflationary model parameters and initial conditions and is the first publicly available code that can efficiently generate large sample-sets for inflation models with $\mathcal O(100)$ fields. The code numerically solves the equations of motion for the background and first-order perturbations of multi-field inflation models with canonical kinetic terms and arbitrary potentials, providing the adiabatic, isocurvature, and tensor power spectra at the end of inflation. For models with sum-separable potentials MultiModeCode also computes the slow-roll prediction via the $\delta N$ formalism for easy model exploration and validation. We pay particular attention to the isocurvature perturbations as the system approaches the adiabatic limit, showing how to avoid numerical instabilities that affect some other approaches to this problem. We demonstrate the use of MultiModeCode by exploring a few toy models. Finally, we give a concise review of multifield perturbation theory and a user's manual for the program.

Comment: 20 pages excluding Appendices, 3 figures. Code publicly available at

Subjects by Vocabulary

Microsoft Academic Graph classification: Eternal inflation Applied mathematics Fortran computer.programming_language computer Toy model Monte Carlo method Solver Equations of motion Adiabatic process Physics Cosmological perturbation theory


Astronomy and Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, High Energy Physics - Phenomenology, High Energy Physics - Theory, Cosmology and Nongalactic Astrophysics (astro-ph.CO), Instrumentation and Methods for Astrophysics (astro-ph.IM), High Energy Physics - Phenomenology (hep-ph), High Energy Physics - Theory (hep-th), FOS: Physical sciences

96 references, page 1 of 10

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[8] R. Easther and L. C. Price, Initial conditions and sampling for multi eld in ation, JCAP 1307 (2013) 027, [arXiv:1304.4244].

[9] R. Easther, L. C. Price, and J. Rasero, In ating an Inhomogeneous Universe, arXiv:1406.2869.

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Funded by
NSF| Programs on Critical Problems in Physics, Astrophysics and Biophysics at the Aspen Center for Physics
  • Funder: National Science Foundation (NSF)
  • Project Code: 1066293
  • Funding stream: Directorate for Mathematical & Physical Sciences | Division of Physics
Understanding the Origin of Cosmic Structure
  • Funder: European Commission (EC)
  • Project Code: 306478
  • Funding stream: FP7 | SP2 | ERC