{"paper":{"title":"Geodesic completion of big bangs from emergent geometry","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"A phantom Chaplygin gas forces the Einstein-frame lapse to cross zero smoothly, causing a time-reversal bounce that completes geodesics through the big bang.","cross_cats":["hep-th"],"primary_cat":"gr-qc","authors_text":"Benjamin Shlaer, Brooke Berrios, Cameron Corley, Jada Young, Sky O'Donnell","submitted_at":"2026-02-25T07:13:45Z","abstract_excerpt":"Chaplygin gas and other k-essence models exhibit emergent geometry, with perturbations propagating on an acoustic metric disformally related to the Einstein-frame metric. For superluminal sound speed, we identify the disformal metric as the \"causal frame,\" since choosing a finite causal-frame lapse yields hyperbolic equations of motion for fields propagating in either frame. We show that with a phantom Chaplygin gas, the Einstein-frame lapse is forced to pass smoothly through zero and change sign while the causal-frame lapse remains positive. As a result, Einstein-frame degrees of freedom (inc"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"with a phantom Chaplygin gas, the Einstein-frame lapse is forced to pass smoothly through zero and change sign while the causal-frame lapse remains positive. As a result, Einstein-frame degrees of freedom (including the scale factor) undergo spontaneous time-reversal while the Chaplygin gas evolves monotonically, enforcing a robust non-singular bounce even in the presence of additional matter canonically coupled to the Einstein frame.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"The model must be a phantom Chaplygin gas with superluminal sound speed so that the disformal acoustic metric defines a causal frame whose lapse stays positive while the Einstein-frame lapse crosses zero.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"Phantom Chaplygin gas forces the Einstein-frame lapse to change sign smoothly while the causal-frame lapse stays positive, yielding a robust non-singular bounce even with extra matter.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"A phantom Chaplygin gas forces the Einstein-frame lapse to cross zero smoothly, causing a time-reversal bounce that completes geodesics through the big bang.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"bcd975b33aa6a606959d7df08c2742b9004f4777232413e2c4671ef6ac9ffc1a"},"source":{"id":"2602.21642","kind":"arxiv","version":2},"verdict":{"id":"56911096-e82f-47cb-807a-7b137f5b9f94","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-15T19:53:30.903356Z","strongest_claim":"with a phantom Chaplygin gas, the Einstein-frame lapse is forced to pass smoothly through zero and change sign while the causal-frame lapse remains positive. As a result, Einstein-frame degrees of freedom (including the scale factor) undergo spontaneous time-reversal while the Chaplygin gas evolves monotonically, enforcing a robust non-singular bounce even in the presence of additional matter canonically coupled to the Einstein frame.","one_line_summary":"Phantom Chaplygin gas forces the Einstein-frame lapse to change sign smoothly while the causal-frame lapse stays positive, yielding a robust non-singular bounce even with extra matter.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"The model must be a phantom Chaplygin gas with superluminal sound speed so that the disformal acoustic metric defines a causal frame whose lapse stays positive while the Einstein-frame lapse crosses zero.","pith_extraction_headline":"A phantom Chaplygin gas forces the Einstein-frame lapse to cross zero smoothly, causing a time-reversal bounce that completes geodesics through the big bang."},"references":{"count":19,"sample":[{"doi":"","year":2022,"title":"U. Moschella and M. Novello, Int. J. Mod. Phys. D31, 2250010 (2022), arXiv:2103.10473 [gr-qc]","work_id":"16e9f84a-f5c9-4099-8995-a44808253834","ref_index":1,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":1993,"title":"J. D. Bekenstein, Phys. Rev. D48, 3641 (1993), arXiv:gr- qc/9211017","work_id":"9ba664dc-e662-4855-97c0-75c5b710183a","ref_index":2,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":null,"title":"k-Essence, superluminal propagation, causality and emergent geometry","work_id":"9504c7c9-761b-4c1f-b8d4-e8add2db7352","ref_index":3,"cited_arxiv_id":"0708.0561","is_internal_anchor":true},{"doi":"","year":2007,"title":"On causality and superluminal behavior in classical field theories. Applications to k-essence theories and MOND-like theories of gravity","work_id":"ba5d69d9-5a83-4fff-b789-6d70d1ce649f","ref_index":4,"cited_arxiv_id":"gr-qc/0607055","is_internal_anchor":true},{"doi":"","year":null,"title":"Null energy condition and superluminal propagation","work_id":"be2a4cd6-9bd9-4176-8a7c-72b54c0f51b4","ref_index":5,"cited_arxiv_id":"hep-th/0512260","is_internal_anchor":true}],"resolved_work":19,"snapshot_sha256":"b768053e659494c3514995eae0bf43834696f97281506a1ae81e8e934d088b3c","internal_anchors":11},"formal_canon":{"evidence_count":2,"snapshot_sha256":"3b22b373462593e24f27fc3d7ce45d035d957fdf1fd9e1c1f80b6b1a2b5271b5"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}