{"artifact_id":"L1-913","layer":"L1","title":"Dark Energy — Cosmic Expansion History w(z)","domain":"Cosmology","sub_domain":"Accelerating Universe","physics_fingerprint":{"intro":"The universe's expansion is accelerating, driven by 'dark energy.' Is it a cosmological constant (w = −1) or evolving? Reconstructing the equation of state w(z) from supernovae, BAO and cosmic chronometers is the decisive test.","title":"Dark Energy — Cosmic Expansion History w(z)","domain":"Cosmology","chapter":"Ch.11 Physics & Cosmology","why_hard":"w(z) is recovered from integrated distances — a smoothing inverse problem; systematics across probes must be jointly modeled; tiny deviations from −1 matter enormously.","agent_idea":"An agent that ingests new cosmological datasets and updates the w(z) posterior with systematics-aware inference.","approaches":["Gaussian-process / nonparametric w(z) reconstruction","Joint SNe + BAO + chronometer simulation-based inference","Model comparison: ΛCDM vs w0wa vs quintessence"],"sub_domain":"Accelerating Universe","forward_model":"H(z)²=H₀²[Ω_m(1+z)³+Ω_DE·exp(3∫₀ᶻ(1+w(z'))/(1+z')dz')]; luminosity distance d_L(z) fits SNe Ia + BAO.","benchmark_goal":"Reconstruct w(z) from distance–redshift data with RMS error ≲ 0.08 and H0 within ~1 km/s/Mpc.","challenge_blurb":"Measure whether dark energy is a constant or evolving — reconstruct the equation of state w(z) from the expansion history.","challenge_group":"physics","challenge_short":"Dark Energy","grand_challenge":true,"governing_equation":"H(z)² = H₀²[Ω_m(1+z)³ + Ω_DE·e^{3∫(1+w)/(1+z)dz}]"},"observable_profile":{"unit":"RMS error on reconstructed w(z) (lower better)","floor":0.1,"metric":"w_recon_err","sota_reference":"DESI + Pantheon+ w₀wₐ constraints"},"size_tiers":{"sne":[200,1500,20000],"z_bins":[5,20,60]},"hardness_fn":{"type":"grand_challenge","metric":"w_recon_err","baseline":"ΛCDM two-parameter fit","delta_tier":50},"initiator_dataset":[{"name":"Pantheon+ Type-Ia supernovae","weight":0.5,"ipfs_cid":null,"license_hash":null},{"name":"DESI BAO distance measurements","weight":0.3,"ipfs_cid":null,"license_hash":null},{"name":"Cosmic-chronometer H(z) set","weight":0.2,"ipfs_cid":null,"license_hash":null}],"status":"testnet","staked_pwm":5000.0,"chain_hash":null,"chain_tx_hash":null,"chain_block":null,"wp":{},"plain_intro":"Dark Energy — Cosmic Expansion History w(z) (Accelerating Universe) is a problem in Cosmology. The forward model maps the hidden the unknown quantity to a measurement. The inverse goal is to recover the the unknown quantity from the observed data."}