ModeChord is a Fortran 95/2000 package that computes the primordial scalar and tensor power spectra for single field inflationary models. ModeChord solves the inflationary mode equations numerically, avoiding the slow roll approximation. It provides an efficient and robust numerical evaluation of the inflationary perturbation spectrum, and allows the free parameters in the inflationary potential to be estimated. ModeChord also allows the estimation of reheating uncertainties once a potential has been specified.


Constraints on natural inflation assuming instantaneous (red), restrictive (blue) and permissive (grey) entropy generation scenarios, computed using ModeCode (Planck Collaboration, 2014).

ModeChord consists of the ModeCode solver interfaced with CAMB and PolyChord via the CosmoChord plugin to CosmoMC, to compute cosmic microwave background angular power spectra, and perform parameter estimation and Bayesian model comparison.  ModeChord incorporates a module for implementing Slow Roll reconstruction of the inflationary dynamics. In addition, ModeChord can be run as a standalone code.


Constraints on generalised axion monodromy parameters, illustrating PolyChord sampling from non-trivial likelihood topologies (Planck Collaboration, 2015).

ModeChord is currently maintained by (alphabetical order): Richard Easther, Will HandleyHiranya Peiris. Please email them with any comments and bug reports. Co-authors Michael Mortonson, Jorge Noreña, Licia Verde, and  Christian Wagner have contributed to previous releases of ModeChord.

A bibliography is available here.

The latest version of ModeChord is available publicly on github here.

We make ModeChord available under a Modified BSD license. We hope that you find ModeChord useful. If you use it in a publication, please cite the ModeCode release papers [BibTexBibTexBibTex],  as well as the CAMB / CosmoMC and PolyChord bibliography.

An earlier version of ModeCode, which used the MultiNest sampler, is no longer maintained or supported, and a legacy version (compatible with pre-Planck versions of  CosmoMC) is available here.