{"paper":{"title":"Phase-Space Constraints on a General Class of Eckart-like Viscous Cosmologies","arxiv_id":"2610.35405","primary_cat":"gr-qc","submitted_at":"2026-10-26T13:19:35+00:00","version_compiled":"v1"},"notice":"Every quoted sentence is the authors' text from the arXiv listing abstract. Labels and probabilities are the outputs of classifier-1.13.0 on the question bank abstract-p1-20260923, exactly as returned. No sentence in this record was written by a language model.","schema":"pith.compiled-record/v0","status":"compiled","abstract":{"source":"arXiv listing abstract v1","sentences":[{"i":0,"p":0.96,"id":"s0","own":true,"role":"contribution","text":"We study the cosmological dynamics of a general class of viscous dark matter models using a dynamical system analysis.","hedge":{"p":0.85,"label":"asserted"},"own_p":0.94,"main_claim_p":0.03,"quantitative":false,"quantitative_p":0.03,"role_probabilities":{"gap":0.0,"method":0.04,"result":0.0,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.96,"interpretation":0.0}},{"i":1,"p":0.61,"id":"s1","own":false,"role":"background","text":"In the Eckart formalism, these viscous cosmologies are characterized by a dimensionless bulk viscous pressure $\\Omega_\\Pi \\equiv \\Omega_\\Pi(\\Omega_m)$, where $\\Omega_m$ is the matter density parameter.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.12,"main_claim_p":0.02,"quantitative":false,"quantitative_p":0.09,"role_probabilities":{"gap":0.0,"method":0.35,"result":0.0,"background":0.61,"limitation":0.0,"future_work":0.0,"contribution":0.04,"interpretation":0.0}},{"i":2,"p":0.98,"id":"s2","own":true,"role":"result","text":"Our analysis demonstrates that a viable early radiation era requires the complete absence of viscosity, a proper matter-dominated epoch demands a small viscous pressure, and the only physically admissible late-time attractor is the cosmological constant-dominated fixed point; consequently, the background expansion must closely track standard $\\Lambda$CDM evolution.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.94,"main_claim_p":0.84,"quantitative":true,"quantitative_p":0.59,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.98,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.02}},{"i":3,"p":0.73,"id":"s3","own":true,"role":"result","text":"We validate these general results using the power-law parameterization $\\Omega_\\Pi = -\\hat{\\xi}_0 \\Omega_m^s$, where $\\hat{\\xi}_0$ and $s$ are real parameters; for $s \\geq 1$ and $\\hat{\\xi}_0 \\ll 1$, the model reproduces the $\\Lambda$CDM background, while for $s < 1$ the system encounters a past-time integration boundary where the dark matter density transitions into negative values and its viscous pressure evaluates to nonphysical complex numbers.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.93,"main_claim_p":0.14,"quantitative":true,"quantitative_p":0.97,"role_probabilities":{"gap":0.0,"method":0.19,"result":0.73,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.08,"interpretation":0.0}},{"i":4,"p":0.93,"id":"s4","own":true,"role":"interpretation","text":"Since the background expansion essentially duplicates $\\Lambda$CDM, the model is unlikely to resolve the $H_0$ tension.","hedge":{"p":0.95,"label":"hedged_possibility"},"own_p":0.73,"main_claim_p":0.25,"quantitative":false,"quantitative_p":0.33,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.01,"background":0.0,"limitation":0.06,"future_work":0.0,"contribution":0.0,"interpretation":0.93}},{"i":5,"p":0.95,"id":"s5","own":true,"role":"result","text":"However, large differences arise at the linear perturbative level; indeed, on sub-horizon scales, bulk viscosity causes a scale-dependent dissipative drag on the matter density fluctuations; this increases the Hubble friction, offering a channel to suppress structure growth.","hedge":{"p":0.84,"label":"asserted"},"own_p":0.83,"main_claim_p":0.1,"quantitative":false,"quantitative_p":0.32,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.95,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.05}}]},"compiled":{"main_claim":{"p":0.91,"text":"Our analysis demonstrates that a viable early radiation era requires the complete absence of viscosity, a proper matter-dominated epoch demands a small viscous pressure, and the only physically admissible late-time attractor is the cosmological constant-dominated fixed point; consequently, the background expansion must closely track standard $\\Lambda$CDM evolution.","location":"abstract s2","hedge_strength":{"p":1.0,"label":"asserted"}},"provenance":{"route":{"via":"TypeSafe API","model":"classifier-1.13.0","endpoint":"https://api.typesafe.ai/v1/systemone","provider":"TypeSafe"},"packing":"one request per paper","requests":1,"input_tokens":5347,"cost_usd_reported":0.0},"compiled_at":"2026-10-27","bank_version":"abstract-p1-20260923","model_version":"classifier-1.13.0","abstract_states":{"claims_first":0.03,"states_limitation":0.91,"human_participants":0.01,"controlled_comparison":0.32,"randomized_assignment":0.01,"states_quantitative_result":0.38,"compares_with_prior_results":0.7,"mentions_code_or_data_availability":0.02},"evidential_basis":{"p":0.98,"value":"proof or derivation","probabilities":{"argument":0.01,"literature":0.0,"proof_or_derivation":0.98,"analysis_of_existing_data":0.0,"observation_or_experiment":0.0,"simulation_or_computation":0.01}},"contribution_type":{"p":1.0,"value":"theoretical result","probabilities":{"review":0.0,"method_or_tool":0.0,"empirical_study":0.0,"simulation_study":0.0,"theoretical_result":1.0,"dataset_or_benchmark":0.0,"position_or_commentary":0.0}},"contribution_statement":{"p":0.63,"text":"Our analysis demonstrates that a viable early radiation era requires the complete absence of viscosity, a proper matter-dominated epoch demands a small viscous pressure, and the only physically admissible late-time attractor is the cosmological constant-dominated fixed point; 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