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I took a quick look because I'm aware of the work that has gone in to producing the best estimates of \Lambda CDM parameters from CMB data. This has been done
by mturmon 8y ago
I took a quick look because I'm aware of the work that has gone in to producing the best estimates of \Lambda CDM parameters from CMB data. This has been done by large-scale MCMC - not DL at all. But, the CMB signal really is Gaussian, so MCMC is well-suited.
By going to the trouble of making a principled forward model including error statistics, you get error bars on all reported parameters, such as the age of the universe - these error bars are critical to later analysis. ("This model requires a Hubble constant in the range ... which is not supported by current observational evidence.")
Parameter estimation from large scale structure is not as "easy". OTOH, I wonder about the accuracy of their map from (cosmological parameters) -> (Large scale structure), because that's what their system is inverting. That is, I wonder about their training data.
From sec. 4C of the current paper, and comparing to their reference to Ravanbakhsh et al 2017 (ICML, [1]), they seem to be using numerical simulations (N-body sims representing gravitational coalescence). These models might have large systematic errors, and their inverse may have its own problems.
Long way to say: I wonder how these estimates of Lambda CDM parameters are viewed by the astrophysics community? The present paper is more of a systems/methods paper than an astrophysics paper. The estimates will come with no error bars, and will be critically based on the simulations used, and the NN limitations.
[1] https://arxiv.org/pdf/1711.02033.pdf https://arxiv.org/pdf/1711.02033.pdf
- SiempreViernes 8y agoHonestly it seems a bit like stirring the linear algebra pile for the sake of stirring, I don’t think fitting parameters to observation is a space that needs deep neural nets. They talk about their method allowing fast experimentation with how to train dnn, but what is really needed computationally is fast n-body sims to explore the theory space not a fast classifier once you have a fully converged simulation. I just can’t see what role the trained network has in cosmology.
- grumpopotamus 8y agoRecently there was some very interesting work on solving ambiguous inverse problems with Invertible Neural Networks: https://hci.iwr.uni-heidelberg.de/vislearn/inverse-problems-invertible-neural-networks/ https://hci.iwr.uni-heidelberg.de/vislearn/inverse-problems-... >We can for example say that this specific observation y either corresponds to a young cluster with large expansion velocity, or to an older system that expands slowly.