candl: Cosmic Microwave Background Analysis with a Differentiable Likelihood

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Main Authors: Balkenhol, L., Trendafilova, C., Benabed, K., Galli, S.
Format: Preprint
Published: 2024
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author Balkenhol, L.
Trendafilova, C.
Benabed, K.
Galli, S.
author_facet Balkenhol, L.
Trendafilova, C.
Benabed, K.
Galli, S.
contents We present candl, an automatically differentiable python likelihood for analysing cosmic microwave background (CMB) power spectrum measurements. candl is powered by JAX, which makes it fast and easy to calculate derivatives of the likelihood. This facilitates, for example, robust Fisher matrices without finite-difference methods. We show the benefits of candl through a series of example calculations, covering forecasting, robustness tests, and gradient-based Markov chain Monte Carlo sampling. These also include optimising the band power bin width to minimise parameter errors of a realistic mock data set. Moreover, we calculate the correlation of parameter constraints from correlated and partially overlapping subsets of the SPT-3G 2018 $TT/TE/EE$ data release. In a traditional analysis framework, these tasks are slow and require careful fine-tuning to obtain stable results. As such, a fully differentiable pipeline allows for a higher level of scrutiny; we argue that this is the paradigm shift required to leverage incoming data from ground-based experiments, which will significantly improve the cosmological parameter constraints from the Planck mission. candl comes with the latest primary and lensing power spectrum data from the South Pole Telescope and Atacama Cosmology Telescope collaborations and will be used as part of the upcoming SPT-3G $TT/TE/EE$ and $ϕϕ$ data releases. Along with the core code, we release a series of auxiliary tools, which simplify common analysis tasks and interface the likelihood with other cosmological software. candl is pip-installable and publicly available at https://github.com/Lbalkenhol/candl .
format Preprint
id arxiv_https___arxiv_org_abs_2401_13433
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle candl: Cosmic Microwave Background Analysis with a Differentiable Likelihood
Balkenhol, L.
Trendafilova, C.
Benabed, K.
Galli, S.
Cosmology and Nongalactic Astrophysics
We present candl, an automatically differentiable python likelihood for analysing cosmic microwave background (CMB) power spectrum measurements. candl is powered by JAX, which makes it fast and easy to calculate derivatives of the likelihood. This facilitates, for example, robust Fisher matrices without finite-difference methods. We show the benefits of candl through a series of example calculations, covering forecasting, robustness tests, and gradient-based Markov chain Monte Carlo sampling. These also include optimising the band power bin width to minimise parameter errors of a realistic mock data set. Moreover, we calculate the correlation of parameter constraints from correlated and partially overlapping subsets of the SPT-3G 2018 $TT/TE/EE$ data release. In a traditional analysis framework, these tasks are slow and require careful fine-tuning to obtain stable results. As such, a fully differentiable pipeline allows for a higher level of scrutiny; we argue that this is the paradigm shift required to leverage incoming data from ground-based experiments, which will significantly improve the cosmological parameter constraints from the Planck mission. candl comes with the latest primary and lensing power spectrum data from the South Pole Telescope and Atacama Cosmology Telescope collaborations and will be used as part of the upcoming SPT-3G $TT/TE/EE$ and $ϕϕ$ data releases. Along with the core code, we release a series of auxiliary tools, which simplify common analysis tasks and interface the likelihood with other cosmological software. candl is pip-installable and publicly available at https://github.com/Lbalkenhol/candl .
title candl: Cosmic Microwave Background Analysis with a Differentiable Likelihood
topic Cosmology and Nongalactic Astrophysics
url https://arxiv.org/abs/2401.13433