{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"4965510eefafac862953fd5a142d22fdb9dbd7b3b1fd5353efed7c57f4c87fd5","created":"2026-10-03T07:17:56Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"b74d8ecff93cf84c60c17cd3b2d7d30671e18ae20ff97efdb421389c065a387b","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"classification","assisted_by":[],"external_id":"bio.active-matter.active-glass","kind":"phenomenon","literature_status":"open","n":"1","parents":[],"plain":"Dense crowds of self-propelled particles, such as packed cell layers or active colloids, become glassy and nearly stop moving, much like a cooling liquid. Whether this active glass follows the same physics as an ordinary glass with an effective temperature, or a different one, is not known.","posed_since":"","precise":"For dense active Brownian or active Ornstein-Uhlenbeck particles with active force $f_0$ and persistence time $\\tau_p$, determine the dynamical arrest line $\\phi_g(f_0, \\tau_p)$ and whether fragility, dynamic heterogeneity ($\\chi_4$) and the relaxation spectrum map onto those of the passive glass at an effective temperature, given reports that $\\tau_{\\alpha}$ depends non-monotonically on $\\tau_p$ at fixed effective temperature. An answer is the arrest diagram with a quantitative test of the effective-temperature mapping and a theory that predicts where it fails.","problem_ref":null,"references":"","settled_by":"Simulations over several decades of $\\tau_{\\alpha}$ and $\\tau_{p}$, compared with an active mode-coupling or other theory, and with measurements on dense active colloids or cell monolayers.","status_note":"Reviewed in 2019 (Janssen, Active glasses, J. Phys.: Condens. Matter, https://doi.org/10.1088/1361-648X/ab3e90); no consensus theory as of 2026.","title":"How self-propulsion changes the glass transition of dense active matter","topic_ref":"6a008dc19304a289e116a6d6e6371cc6de0ef3d1a904e572d5454f039b2ac217"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"a4adba3a5b38e876f60c32868a1f85eed9b25a74325433cf69d24b465e4e02b2","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"f019a49ae6e1094bc6cdbd471b40aea7df89cd258cfdcc6b5e02228ca6cd9440","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"XNbjkKnUIZsvgsI3Cyh2e6dTiB3N98w6ZOkP-zqmm2T_GmpCc6W8Q7fe_tIQ5pqUJj2z9SH_EZxuVlajzi9eDw"},"schema":"pubphys.envelope/1"},"record_hash":"a4adba3a5b38e876f60c32868a1f85eed9b25a74325433cf69d24b465e4e02b2","leaf_index":718}