Perturbed metric, gauge and physical observables
Research context
research method · conditional · As of 2026-10-10
Relativistic perturbation variables depend on the coordinate gauge.
Key knowledge
Relativistic perturbation variables depend on the coordinate gauge. Synchronous and conformal Newtonian descriptions must transform consistently; comparing their raw density perturbations without transformation can manufacture a discrepancy. Observable angular spectra require a full consistent projection.
Values and equations
ds^2=a^2[-(1+2ψ)dτ^2+(1-2φ)δij dx^i dx^j]
- a
- Scale factor 1
- τ
- Conformal time in c=1 units
- ψ,φ
- Conformal Newtonian scalar metric potentials 1
- δij
- Euclidean background spatial metric 1
Conditions and scope
- Linear scalar perturbations about FLRW; the displayed conformal metric uses c=1.
- Do not set both scalar potentials equal when anisotropic stress is significant.
Sources · 1
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).
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.
Entry details
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- research-earth-metric-gauge
- Revision
- research.1
- Structured reference record
- Postgraduate & research reference