Baryon acoustic oscillation
Definition: The late-time clustering imprint of sound waves in the pre-recombination photon-baryon plasma.
Why it matters here: It is required to answer How do galaxy clustering measurements encode distance? and to distinguish direct observation from cosmological inference.
Relationships: Read it with Sound horizon, the model \(D_V(z)=[D_M(z)^2 c z/H(z)]^(1/3)\), and the evidence statement Three published BOSS DR12 consensus points at z=0.38, 0.51, and 0.61 are included as literature-summary measurements, not raw clustering data.
Boundary or common confusion: Do not compare D_V in Mpc directly to D_V r_d,fid/r_d unless explicitly setting r_d=r_d,fid; BAO does not measure an absolute ruler without early-universe calibration.
Sound horizon
Definition: The comoving distance an acoustic wave traveled before baryon drag ended.
Why it matters here: It is required to answer How do galaxy clustering measurements encode distance? and to distinguish direct observation from cosmological inference.
Relationships: Read it with Standard ruler, the model \(D_V(z)=[D_M(z)^2 c z/H(z)]^(1/3)\), and the evidence statement Three published BOSS DR12 consensus points at z=0.38, 0.51, and 0.61 are included as literature-summary measurements, not raw clustering data.
Boundary or common confusion: Do not compare D_V in Mpc directly to D_V r_d,fid/r_d unless explicitly setting r_d=r_d,fid; BAO does not measure an absolute ruler without early-universe calibration.
Standard ruler
Definition: A feature with calibrated physical length whose observed angular or redshift extent constrains geometry.
Why it matters here: It is required to answer How do galaxy clustering measurements encode distance? and to distinguish direct observation from cosmological inference.
Relationships: Read it with Volume-averaged distance, the model \(D_V(z)=[D_M(z)^2 c z/H(z)]^(1/3)\), and the evidence statement Three published BOSS DR12 consensus points at z=0.38, 0.51, and 0.61 are included as literature-summary measurements, not raw clustering data.
Boundary or common confusion: Do not compare D_V in Mpc directly to D_V r_d,fid/r_d unless explicitly setting r_d=r_d,fid; BAO does not measure an absolute ruler without early-universe calibration.
Volume-averaged distance
Definition: The isotropic BAO combination D_V that mixes transverse area and radial depth.
Why it matters here: It is required to answer How do galaxy clustering measurements encode distance? and to distinguish direct observation from cosmological inference.
Relationships: Read it with Anisotropic BAO, the model \(D_V(z)=[D_M(z)^2 c z/H(z)]^(1/3)\), and the evidence statement Three published BOSS DR12 consensus points at z=0.38, 0.51, and 0.61 are included as literature-summary measurements, not raw clustering data.
Boundary or common confusion: Do not compare D_V in Mpc directly to D_V r_d,fid/r_d unless explicitly setting r_d=r_d,fid; BAO does not measure an absolute ruler without early-universe calibration.
Anisotropic BAO
Definition: Separate use of transverse and radial clustering to constrain D_M/r_d and H r_d.
Why it matters here: It is required to answer How do galaxy clustering measurements encode distance? and to distinguish direct observation from cosmological inference.
Relationships: Read it with Baryon acoustic oscillation, the model \(D_V(z)=[D_M(z)^2 c z/H(z)]^(1/3)\), and the evidence statement Three published BOSS DR12 consensus points at z=0.38, 0.51, and 0.61 are included as literature-summary measurements, not raw clustering data.
Boundary or common confusion: Do not compare D_V in Mpc directly to D_V r_d,fid/r_d unless explicitly setting r_d=r_d,fid; BAO does not measure an absolute ruler without early-universe calibration.