{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"8f5e46e13b0cf4a3c3d67ec9e7736228017585e8a2d8f4102c2ee7083f826fb1","created":"2026-10-03T07:18:07Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"58c529bd40260f4a0ab0d04fceff588cc83e7ff556c78b81b319225cc2050615","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"nuc.neutron-star-matter.sound-speed-peak","kind":"well-posed","literature_status":"partially-resolved","n":"1","parents":[],"plain":"In matter made of free quarks at very high density, sound travels at the speed of light divided by the square root of 3. Neutron-star data suggest sound travels faster than this somewhere inside, but the evidence depends on modeling assumptions.","posed_since":"","precise":"Determine whether $c_s^{2} = \\mathrm{d}P/\\mathrm{d}\\epsilon$ exceeds $c^2/3$ (the value for free massless quarks) at some density below the central density of a maximum-mass star. Answer: yes or no, with posterior probability given pulsar masses, NICER radii, tidal deformabilities, chiral EFT below about $2 n_0$ and perturbative QCD limits.","problem_ref":null,"references":"","settled_by":"Equation-of-state inference using 2 percent radius measurements across masses from 1.2 to 2.1 solar masses.","status_note":"Bayesian analyses including two-solar-mass pulsars and NICER radii have found $c_{s}^{2} > c^{2}/3$ in most posteriors since about 2018, with the probability depending on the priors as of 2026.","title":"Does the sound speed exceed the conformal bound inside neutron stars?","topic_ref":"dc9703fcc2930752e3222472fa4f0774fcc6cb72d19c4033b77e3e2b58d0fcb3"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"4cb0a6f8827ec2141657f4461447e521ff1f75abb99e27db618281eabe4128c9","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"957b1ad11ba6f9452574dce5cc4d55a247076c4d4a116f8fde48a06b9a5fc73f","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"dm8pAQABiDPoGXqpiuWJdPT4IQwf1j-edTKYvcQ-ETJyS3qoT_IGBLdP8Ro8mgS5qGIsqd5_TLAXUsrjePYXAA"},"schema":"pubphys.envelope/1"},"record_hash":"4cb0a6f8827ec2141657f4461447e521ff1f75abb99e27db618281eabe4128c9","leaf_index":1782}