{"paper":{"title":"Null Energy Condition and Dark Energy Models","license":"","headline":"","cross_cats":["astro-ph","hep-ph","hep-th"],"primary_cat":"gr-qc","authors_text":"Taotao Qiu, Xin-Min Zhang, Yi-Fu Cai","submitted_at":"2007-09-30T08:11:41Z","abstract_excerpt":"Null Energy Condition (NEC) requires the equation of state (EoS) of the universe $w_u$ satisfy $w_u\\geq-1$, which implies, for instance in a universe with matter and dark energy dominating $w_u=w_m\\Omega_m+w_{de}\\Omega_{de}=w_{de}\\Omega_{de}\\geq-1$. In this paper we study constraints on the dark energy models from the requirement of the NEC. We will show that with $\\Omega_{de}\\sim0.7$, $w_{de}<-1$ at present epoch is possible. However, NEC excludes the possibility of $w_{de}<-1$ forever as happened in the Phantom model, but if $w_{de}<-1$ stays for a short period of time as predicted in the Qu"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"0710.0115","kind":"arxiv","version":1},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/0710.0115/integrity.json","findings":[],"available":true,"detectors_run":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938"},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}