Right now, in cosmology, emulators are all the rage: Cosmological simulations are slow and expensive, and we need to speed them up! But I'm concerned: What if we use emulators in all our Euclid and LSST pipelines, and then we find something very surprising? What then? Do we check it all using full-blown simulations? But then, if so, why not do full-blown from the outset? Or do our standards of care depend on our results? They aren't supposed to, but maybe they do?
Worried about all this, I have been thinking about how to make emulators better, and give them provably better properties. It's why I've been working on building methods that exactly obey symmetries. But from an epistemological perspective, emulators might be the Worst Idea EverTM.
In detail, I'm working out how we might build emulators that are trained on one simulation suite but can be tested on another, made with a different cosmology and at a different mass resolution. I think work I've been doing with Villar (JHU) on the exact symmetries imposed by geometry and units might make this possible. I'm trying to figure out the scope of an achievable paper on this.
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