Prioritising modified gravity models

Just a brief note this week. One thing looming on the horizon is the LSST Dark Energy Science Collaboration meeting in Stanford, where we’ll spend a couple of sessions discussing which models beyond the standard LambdaCDM model we should prioritise to be tested when the first data arrive.

In an ideal world, we’d test everything that seemed interesting, for a very loose and inclusive definition of the word interesting. Wouldn’t want to miss out that crazy theory that might just be the answer to all the big problems in physics now, would we? The problem is, testing models takes a lot of time and effort, with the effort required becoming increasingly prohibitive as we begin to push to sub-1% precision on cosmological parameters. Modern survey data are incredibly complex, and so it takes a lot to ensure that the analysis you’re doing is robust – a lot of computing time, a lot of validation, a lot of simulations, a lot of model complexity… It’s just hard.

So, we need to prioritise. I think the best bet for now would be to whittle down the vast array of possible models into a very short but diverse list. This could cover some neat examples of very different physics, but without any attempt at being comprehensive. The diversity will give us a handful of “example” implementations of testable models that can be used as templates for future, more comprehensive, analyses. Sticking to a short list is crucial for now however, as it will allow us to focus our development and simulation effort without overreaching.

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About Phil Bull

I'm a theoretical cosmologist, currently working as a NASA NPP fellow at JPL/Caltech in Pasadena, CA. My research focuses on the effects of inhomogeneities on the evolution of the Universe and how we measure it. I'm also keen on stochastic processes, scientific computing, the philosophy of science, and open source stuff. View all posts by Phil Bull

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