Today my first paper as first author came out on the arXiv! You can check it out here: https://arxiv.org/abs/2002.10449. In this work, we reconstruct a coupling function between dark matter and vacuum energy. Such models are generally motivated as solution to problems such as the Hubble tension, so we were keen to update our previous work (https://arxiv.org/abs/1902.10694) with the new Planck likelihood, as well as the Pantheon supernovae catalogue, along with various BAO and RSD datasets.

With the implementation of a correlation prior to help control rapid oscillations in the function , we were able to make the reconstruction, finding hints of an interesting feature around redshift 3. To determine whether this is a real signature of a peak in the coupling between vacuum and dark matter will require more data at that redshift or above, something which is lacking in current cosmology.

In the final part of the paper, we calculated the Bayesian evidence for each case we tested (we implemented two slightly different versions of the correlation prior), but we did not find any conclusive evidence for a deviation from LambdaCDM, which is recovered when the interaction is equal to zero.

I’m grateful to my collaborators for their hard work on this project, particularly Rob and Matteo for their technical advice and Simone, who wrote the code to add the correlation prior to CosmoMC. I’m excited to have this paper out in the world, and looking forward to focusing my efforts back on the forecasting work that I am here in Madrid to attempt.

This weekend, I get to celebrate the paper coming out by heading back to Portsmouth for a long weekend, where I’m planning to catch the University’s production of Offenbach’s Orpheus in the Underworld (he of Can Can fame). If you’re in the area, I highly recommend it, as the pit orchestra will certainly be superb! Tickets available here: https://www.newtheatreroyal.com/performances/updms-presents-orpheus-in-the-underworld/