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Showing 1471–1500 of 1709 reference entries

Earth & cosmosCoupled photoionization, cooling and planetary escape

A photoheated atmosphere couples fluid transport, ionization/recombination, absorption and radiative cooling.

Method
Earth & cosmosCosmological continuity and constant-w density scaling

For an independently conserved homogeneous component with constant equation-of-state w, density scales with a as a^-3(1+w).

Method
Earth & cosmosMatter, radiation and vacuum expansion solutions

Combining a conserved component with flat single-component Friedmann expansion yields matter a∝t^(2/3), radiation a∝t^(1/2) and vacuum exponential expansion.

Method
Earth & cosmosJoint cosmological likelihoods and nuisance degeneracies

Cosmological parameter inference combines data likelihoods with model priors and nuisance parameters for foregrounds, calibration and selection.

Method
Earth & cosmos2026 preprint: DESI Lyman-alpha geometry and dark-energy inference

DESI DR2 Lyman-alpha Alcock–Paczyński measurements add redshift-dependent geometry information with blinded validation and contaminant controls.

Method
Earth & cosmosDeclared isotope reaction networks and stiff abundance balance

A reaction network lists its species and reactions, evolves abundances with a stoichiometric matrix and couples nuclear energy release and escaping neutrino losses to stellar energy.

Method
Earth & cosmosCross-section, resonance and screening uncertainty

Thermal rates average microscopic cross sections over a specified particle distribution.

Method
Earth & cosmosCore-collapse neutrino transport and closure

Core-collapse models couple dense-matter EOS, fluid motion and flavor/energy-dependent neutrino radiation.

Method
Earth & cosmosCompact-star EOS inference across messengers

Dense-matter inference combines nuclear constraints, pulse-profile models and gravitational-wave likelihoods with an EOS parameterization.

Method
Earth & cosmosGRMHD conservation and declared boundary data

Ideal GRMHD evolves rest-mass and stress-energy conservation with magnetic induction in a specified spacetime.

Method
Earth & cosmosMagnetorotational transport and magnetic-flux dependence

Weak well-coupled magnetic fields can destabilize outwardly decreasing differential rotation and drive angular-momentum transport.

Method
Earth & cosmosKinetic reconnection and particle-population limits

Particle-in-cell reconnection experiments evolve fields and particle distributions rather than assume a thermal fluid closure.

Method
Earth & cosmosPolarized synchrotron and self-absorption

For isotropic power-law electrons in a uniform field, optically thin synchrotron has a conditional spectral slope and maximum linear polarization.

Method
Earth & cosmosInverse Compton angular kernels and Klein–Nishina regime

Inverse Compton energy gain depends on incident angle and the photon energy in the electron rest frame.

Method
Earth & cosmosPhoton-pair threshold, opacity and cascades

Two photons can produce an electron–positron pair only above an angle-dependent invariant threshold.

Method
Earth & cosmosCollisionless N-body force and resolution tests

A particle realization approximates a smooth collisionless distribution; force softening and time integration control numerical encounters and force error.

Method
Earth & cosmosGalaxy gas dynamics and matched-solver comparisons

Finite-volume hydrodynamics updates conserved quantities using fluxes across cell boundaries; moving faces require fluxes in the face frame.

Method
Earth & cosmosBar and spiral orbital resonances

Rotating nonaxisymmetric potentials exchange angular momentum at corotation and Lindblad resonances.

Method
Earth & cosmosElement-resolved delayed recycling and gas flows

Chemical evolution follows an element's removal into stars, delayed stellar returns and inflow/outflow.

Method
Earth & cosmosFeedback calibration and survey selection

Unresolved star formation, cooling and feedback need declared subgrid closures and calibrated parameter ranges.

Method
Earth & cosmosPerturbed metric, gauge and physical observables

Relativistic perturbation variables depend on the coordinate gauge.

Method
Earth & cosmosEinstein–Boltzmann hierarchy and convergence

Angular moments of photon/neutrino distributions form a Boltzmann hierarchy coupled to metric and fluid equations.

Method
Earth & cosmosPrimordial models, scalar spectra and tensor tests

Inflationary models relate a stated field action and reheating history to scalar/tensor predictions; observations constrain those predictions rather than identify one unique inflaton.

Method
Earth & cosmosOpen question: unique primordial mechanism

A unique microscopic origin of primordial perturbations is not established by the inspected evidence.

Open question
Earth & cosmosDark-matter evidence and candidate tests

Gravitational evidence constrains additional matter or modified gravitational descriptions under declared assumptions; it does not name a particle.

Method
Earth & cosmosOpen question: dark-matter identity

The dominant dark-matter identity remains unresolved in the inspected evidence.

Open question
Earth & cosmosCosmic acceleration: Λ, dynamical fields and modified gravity

Acceleration is inferred through a framework relating expansion and structure to observations.

Method
Earth & cosmosOpen question: physical cause of acceleration

The physical cause of cosmic acceleration remains unresolved in the inspected sources.

Open question
Earth & cosmosLinear poroelastic storage and deformation coupling

A quasi-static poroelastic model couples elastic displacement to pore pressure and fluid storage.

Method
Earth & cosmosElectromagnetic parameter maps and primary-secondary sensitivities

EM inversion links conductivity/permeability parameters to source, fields and receiver response.

Method
MethodSource checked

Perturbed metric, gauge and physical observables

Earth & cosmos

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.

  1. Cosmological perturbation theory in synchronous and conformal Newtonian gaugesMa and Bertschinger (1995)Research paperarxiv.orgRead source

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 detailsPermanent link to this entry ↗
Record identity
research-earth-metric-gauge
Revision
research.1
Structured reference record
Postgraduate & research reference