{"paper":{"title":"The Cosmic Linear Anisotropy Solving System (CLASS) II: Approximation schemes","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"CLASS Boltzmann code uses three approximations for faster and more precise cosmology calculations.","cross_cats":[],"primary_cat":"astro-ph.CO","authors_text":"Diego Blas, Julien Lesgourgues, Thomas Tram","submitted_at":"2011-04-14T22:06:43Z","abstract_excerpt":"Boltzmann codes are used extensively by several groups for constraining cosmological parameters with Cosmic Microwave Background and Large Scale Structure data. This activity is computationally expensive, since a typical project requires from 10'000 to 100'000 Boltzmann code executions. The newly released code CLASS (Cosmic Linear Anisotropy Solving System) incorporates improved approximation schemes leading to a simultaneous gain in speed and precision. We describe here the three approximations used by CLASS for basic LambdaCDM models, namely: a baryon-photon tight-coupling approximation whic"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"The newly released code CLASS incorporates improved approximation schemes leading to a simultaneous gain in speed and precision.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"The approximations remain sufficiently accurate for the full range of scales, redshifts, and parameter values relevant to current and near-future CMB and LSS analyses without introducing uncontrolled errors.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"CLASS implements a tunable baryon-photon tight-coupling approximation, a new ultra-relativistic fluid approximation, and a radiation streaming approximation that accounts for reionization, yielding simultaneous gains in speed and precision.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"CLASS Boltzmann code uses three approximations for faster and more precise cosmology calculations.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"683e39ece2d5f668574a663316abace55d8ccf792ecdf67dc921c1f090d2dff9"},"source":{"id":"1104.2933","kind":"arxiv","version":3},"verdict":{"id":"a27eb4fc-7611-4883-b321-e6edc52ad74b","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-13T19:00:14.272950Z","strongest_claim":"The newly released code CLASS incorporates improved approximation schemes leading to a simultaneous gain in speed and precision.","one_line_summary":"CLASS implements a tunable baryon-photon tight-coupling approximation, a new ultra-relativistic fluid approximation, and a radiation streaming approximation that accounts for reionization, yielding simultaneous gains in speed and precision.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"The approximations remain sufficiently accurate for the full range of scales, redshifts, and parameter values relevant to current and near-future CMB and LSS analyses without introducing uncontrolled errors.","pith_extraction_headline":"CLASS Boltzmann code uses three approximations for faster and more precise cosmology calculations."},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/1104.2933/integrity.json","findings":[],"available":true,"detectors_run":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938"},"references":{"count":20,"sample":[{"doi":"","year":null,"title":"COSMICS: Cosmological Initial Conditions and Microwave Anisotropy Codes","work_id":"4c52b86b-2d50-41ed-bf0b-b330cdfd9c5f","ref_index":1,"cited_arxiv_id":"astro-ph/9506070","is_internal_anchor":false},{"doi":"","year":1996,"title":"A Line of Sight Approach to Cosmic Microwave Background Anisotropies","work_id":"eb4f33ca-6cd1-4748-85be-88cf587b721a","ref_index":2,"cited_arxiv_id":"astro-ph/9603033","is_internal_anchor":false},{"doi":"","year":2000,"title":"Efficient Computation of CMB anisotropies in closed FRW models","work_id":"366015e5-cd86-4996-8a5e-81ec18d1971c","ref_index":3,"cited_arxiv_id":"astro-ph/9911177","is_internal_anchor":false},{"doi":"","year":2005,"title":"Doran, JCAP 0510 (2005) 011","work_id":"dca75ff7-695f-4f15-a2f3-0aa383c76b69","ref_index":4,"cited_arxiv_id":"astro-ph/0302138","is_internal_anchor":true},{"doi":"","year":2009,"title":"J. Hamann, A. Balbi, J. Lesgourgues, C. Quercellini, JCAP 0904 (2009) 011. [arXiv:0903.0382 [astro-ph.CO]]","work_id":"682f652f-019e-49a9-8fbd-a67a209f1518","ref_index":5,"cited_arxiv_id":"0903.0382","is_internal_anchor":true}],"resolved_work":20,"snapshot_sha256":"dac9d981b1c5d1b882a5f7b966b883c796aec9380ae43516d1353e512ae81f11","internal_anchors":8},"formal_canon":{"evidence_count":1,"snapshot_sha256":"f97d114ac2daf924f38f18278125467b6631e5ba36ea63574cda1331784abf03"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}