This repository contains a set of results and tools to reproduce the results from:

L. Visinelli, N. Bolis, S. Vagnozzi, Brane-world extra dimensions in light of GW170817, Phys. Rev. D97 (2018) 064039 [arXiv: 1711.06628] (VBV17)

where constraints on the size of the AdS₅ radius of curvature within the Randall-Sundrum brane-world model are placed in light of the near-simultaneous detection of the gravitational wave event GW170817 and its optical counterpart, the short γ-ray burst event GRB170817A (Astrophys.J. 848 (2017) no.2, L13). The content of the folders is described below.

This folder contains a patch to the Montepython cosmological MCMC sampler to sample the posterior distribution of the 4-dimensional parameter space in VBV17 and obtain constraints on the parameters. You should therefore first of all download and install Montepython following the documentation provided.

The GW170817_braneworld/ folder implements the likelihood (Eq.(19) in VBV17), hence the name of the experiment you want to use in your run is "GW170817_braneworld" as per Montepython's philosophy. You should copy this folder into your montepython/montepython/likelihoods folder.

You should also copy the contents of the covmat/ folder into your montepython/covmat folder (assuming you want to supply an input covariance matrix to your runs, which is recommended).

The input .param file to do the MCMC run is braneworld.param. To run the MCMC you then want to do something like (customize your arguments as you prefer, see Montepython's documentation):

$ python montepython/MontePython.py run -p braneworld.param -o chains/braneworld -N 100000 --chain-num 1 --update 300 -c covmat/braneworld.covmat [optional arguments]

The supplied braneworld.sl file is a batch file which can be used to run the MCMC on the NERSC supercomputer Cori. To submit, type:

$ sbatch braneworld.sl

The script runs 8 chains in parallel on 1 node, using 4 cores/chain (Cori has 32 cores per node) for 40 minutes (which is more than enough to get a convergence R-1 way better than 0.01. If you want to run on the NERSC supercomputer Edison we recommend instead running 6 chains (i.e. change "-n 8" to "-n 6" in braneworld.sl). You can also use hyperthreading but you don't gain much in terms of running time.

This folder contains the scripts used the produce the 3 figures in VBV17. To run, simply type (directly from the plots/ folder):

$ python file_name.py

where file_name=fig1, fig2, or fig3. This will produce fig1.pdf, fig2.pdf, and fig3.pdf directly in the plots/ folder. Make sure you have installed the getdist Python package.

This folder contains the results of the MCMC analysis used to write VBV17. The MCMC chains we generated are contained in the folder chains/.

The folder plot_data/ contains the output of running getdist on these chains, and is needed to produce Fig.1.

The files braneworld.corr, braneworld.covmat, braneworld.likestats and braneworld.margestats are standard files produced by getdist when analysing the chains. You will need braneworld.corr to produce Fig.3, whereas the numbers in braneworld.margestats are those we actually quote in VBV17 (68% and 95% CL upper limits on the AdS₅ radius of curvature).

If you use these codes in your research, please cite the following paper (if you use Montepython, you should also cite the original work):

L. Visinelli, N. Bolis, S. Vagnozzi, Brane-world extra dimensions in light of GW170817, Phys. Rev. D97 (2018) 064039 [arXiv: 1711.06628]

%\cite{Visinelli:2017bny}
\bibitem{Visinelli:2017bny}
  L.~Visinelli, N.~Bolis and S.~Vagnozzi,
  %``Brane-world extra dimensions in light of GW170817,''
  Phys.\ Rev.\ D {\bf 97} (2018) 064039
  doi:10.1103/PhysRevD.97.064039
  [arXiv:1711.06628 [gr-qc]].
  %%CITATION = doi:10.1103/PhysRevD.97.064039;%%
  %3 citations counted in INSPIRE as of 01 Apr 2018

@article{Visinelli:2017bny,
      author         = "Visinelli, Luca and Bolis, Nadia and Vagnozzi, Sunny",
      title          = "{Brane-world extra dimensions in light of GW170817}",
      journal        = "Phys. Rev.",
      volume         = "D97",
      year           = "2018",
      pages          = "064039",
      doi            = "10.1103/PhysRevD.97.064039",
      eprint         = "1711.06628",
      archivePrefix  = "arXiv",
      primaryClass   = "gr-qc",
      SLACcitation   = "%%CITATION = ARXIV:1711.06628;%%"
}

If you experience any problems with the codes, or to report bugs, please email sunny.vagnozzi@fysik.su.se (unless you're a robot, of course)

This research was supported by: