Einstein–Boltzmann hierarchy and convergence
Research context
research method · conditional · As of 2026-10-10
Angular moments of photon/neutrino distributions form a Boltzmann hierarchy coupled to metric and fluid equations.
Key knowledge
Angular moments of photon/neutrino distributions form a Boltzmann hierarchy coupled to metric and fluid equations. Ma–Bertschinger varied momentum/wavenumber/multipole grids and timesteps, reporting sub-0.1% agreement between their two gauge integrations. Tight coupling and truncation must be tested for each target observable.
Conditions and scope
- Their 1995 test cosmologies used up to 50 massive-neutrino and 2000 massless-particle moments in the stated examples; these settings do not guarantee modern survey accuracy.
- The reference treats linear scalar transport/polarization. Nonlinear lensing and foregrounds need additional models; retain energy–momentum constraints and explicit initial modes.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Cosmological perturbation theory in synchronous and conformal Newtonian gauges: Sections 2–5 and 7–8: metric, fluid/Boltzmann equations, initial data and convergence (selected source body inspected). Planck 2018 results VI: cosmological parameters: Sections 2 and 7: likelihoods, foregrounds, base ΛCDM and parameter degeneracies (selected source body inspected).
2026-10-10 · Bounded source check of the recorded statement and conditions. This does not certify a unique physical model, reproduce the cited study or replace independent branch review.
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- Postgraduate & research reference