Density contrast
Definition: The fractional matter-density perturbation relative to the cosmic mean.
Why it matters here: It is required to answer How does gravity build structure after the CMB? and to distinguish direct observation from cosmological inference.
Relationships: Read it with Growth factor, the model \(delta'' + (2+H'/H)delta' - 3 Omega_m(a) delta/2 = 0\), and the evidence statement Growth curves in this package are model calculations, not measured galaxy power spectra; published DES S8 is used only as a separate summary constraint.
Boundary or common confusion: The scale-independent growth equation assumes linear perturbations and general relativity with smooth dark energy; massive neutrinos and modified gravity alter the picture.
Growth factor
Definition: The time-dependent amplitude of the linear growing mode, usually normalized at a chosen epoch.
Why it matters here: It is required to answer How does gravity build structure after the CMB? and to distinguish direct observation from cosmological inference.
Relationships: Read it with Growth rate, the model \(delta'' + (2+H'/H)delta' - 3 Omega_m(a) delta/2 = 0\), and the evidence statement Growth curves in this package are model calculations, not measured galaxy power spectra; published DES S8 is used only as a separate summary constraint.
Boundary or common confusion: The scale-independent growth equation assumes linear perturbations and general relativity with smooth dark energy; massive neutrinos and modified gravity alter the picture.
Growth rate
Definition: The logarithmic derivative f=d ln D/d ln a.
Why it matters here: It is required to answer How does gravity build structure after the CMB? and to distinguish direct observation from cosmological inference.
Relationships: Read it with Redshift-space distortion, the model \(delta'' + (2+H'/H)delta' - 3 Omega_m(a) delta/2 = 0\), and the evidence statement Growth curves in this package are model calculations, not measured galaxy power spectra; published DES S8 is used only as a separate summary constraint.
Boundary or common confusion: The scale-independent growth equation assumes linear perturbations and general relativity with smooth dark energy; massive neutrinos and modified gravity alter the picture.
Redshift-space distortion
Definition: Anisotropy in observed clustering caused by line-of-sight peculiar velocities.
Why it matters here: It is required to answer How does gravity build structure after the CMB? and to distinguish direct observation from cosmological inference.
Relationships: Read it with f sigma8, the model \(delta'' + (2+H'/H)delta' - 3 Omega_m(a) delta/2 = 0\), and the evidence statement Growth curves in this package are model calculations, not measured galaxy power spectra; published DES S8 is used only as a separate summary constraint.
Boundary or common confusion: The scale-independent growth equation assumes linear perturbations and general relativity with smooth dark energy; massive neutrinos and modified gravity alter the picture.
f sigma8
Definition: A growth observable combining the logarithmic growth rate with fluctuation amplitude.
Why it matters here: It is required to answer How does gravity build structure after the CMB? and to distinguish direct observation from cosmological inference.
Relationships: Read it with Density contrast, the model \(delta'' + (2+H'/H)delta' - 3 Omega_m(a) delta/2 = 0\), and the evidence statement Growth curves in this package are model calculations, not measured galaxy power spectra; published DES S8 is used only as a separate summary constraint.
Boundary or common confusion: The scale-independent growth equation assumes linear perturbations and general relativity with smooth dark energy; massive neutrinos and modified gravity alter the picture.