{"paper":{"title":"Gauge-invariant cosmological perturbations in Type 3 New General Relativity and background-hierarchy bounds","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"Type 3 New General Relativity permits consistent linear cosmological perturbations only within specific parameter bounds.","cross_cats":["astro-ph.CO","hep-th"],"primary_cat":"gr-qc","authors_text":"Daniel Blixt, Kyosuke Tomonari, Sebastian Bahamonde","submitted_at":"2026-05-16T08:15:03Z","abstract_excerpt":"In this paper, we investigate background-hierarchy bounds in Type~3 of New General Relativity (NGR). These bounds arise when the contribution associated with the evolution of the background spacetime exceeds that of the quadratic kinetic term in the perturbed Lagrangian. Type~3 of NGR has two free parameters and preserves diffeomorphism invariance and spatial rotations, while breaking Lorentz-boost invariance. We first review Type~3 and identify preferable gauge choices for metric-affine gauge theories of gravity with Weitzenb\\\"ock connection, including NGR, from the viewpoint of symmetry in b"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"We derive the background-hierarchy bounds for the scalar, transverse-vector, and tensor modes around a flat FLRW background, and identify the region of parameter space in which the linear perturbation theory of Type 3 remains viable for cosmological applications.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"The central comparison that defines the bound assumes the background spacetime evolution contribution exceeds the quadratic kinetic term in the perturbed Lagrangian; if other higher-order or interaction terms become comparable at the same scale, the identified viability region would no longer guarantee a consistent linear theory.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"Derives background-hierarchy bounds on the two free parameters of Type 3 NGR to ensure linear cosmological perturbation theory remains viable around flat FLRW.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"Type 3 New General Relativity permits consistent linear cosmological perturbations only within specific parameter bounds.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"2b161c35f24c53a83819d8d7596ef8ae120e3f3587dbbb8db3b3011a24525ff4"},"source":{"id":"2605.16869","kind":"arxiv","version":1},"verdict":{"id":"20d9c81b-59db-4d5c-8ab3-d1ecae1b9c58","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-19T20:57:13.053085Z","strongest_claim":"We derive the background-hierarchy bounds for the scalar, transverse-vector, and tensor modes around a flat FLRW background, and identify the region of parameter space in which the linear perturbation theory of Type 3 remains viable for cosmological applications.","one_line_summary":"Derives background-hierarchy bounds on the two free parameters of Type 3 NGR to ensure linear cosmological perturbation theory remains viable around flat FLRW.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"The central comparison that defines the bound assumes the background spacetime evolution contribution exceeds the quadratic kinetic term in the perturbed Lagrangian; if other higher-order or interaction terms become comparable at the same scale, the identified viability region would no longer guarantee a consistent linear theory.","pith_extraction_headline":"Type 3 New General Relativity permits consistent linear cosmological perturbations only within specific parameter bounds."},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2605.16869/integrity.json","findings":[],"available":true,"detectors_run":[{"name":"doi_compliance","ran_at":"2026-05-19T21:11:39.552220Z","status":"completed","version":"1.0.0","findings_count":0},{"name":"doi_title_agreement","ran_at":"2026-05-19T21:01:19.227462Z","status":"completed","version":"1.0.0","findings_count":0},{"name":"claim_evidence","ran_at":"2026-05-19T18:41:56.299472Z","status":"completed","version":"1.0.0","findings_count":0},{"name":"ai_meta_artifact","ran_at":"2026-05-19T18:33:26.375745Z","status":"skipped","version":"1.0.0","findings_count":0}],"snapshot_sha256":"f68c2757d1c6d2e2e90f5c7a006785e7cbfebeebe7e63d2d6f76a9a8b3060166"},"references":{"count":78,"sample":[{"doi":"","year":null,"title":"second-order terms of perturbation fields are included in the torsion and metric tensor,","work_id":"84ea40fd-aff9-45f0-b3cf-1b721980ca88","ref_index":1,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":null,"title":"Our results in the previous work are summarized in Table I","work_id":"e2ad5a71-92d8-426f-acb1-118c9e9f9e30","ref_index":2,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":null,"title":"A first-class constraint disappears, giving rise to one new DOF","work_id":"31ae22d7-e15d-4a3c-9022-faa31ac0cb33","ref_index":3,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":null,"title":"Pattern II. 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