The baryon acoustic oscillation peak: a flexible standard ruler
  For about a decade, the baryon acoustic oscillation (BAO) peak at about 105
Mpc/h has provided a standard ruler test of the LCDM cosmological model, a
member of the Friedmann--Lemaitre--Robertson--Walker (FLRW) family of
cosmological models---according to which comoving space is rigid. However,
general relativity does not require comoving space to be rigid. During the
virialisation epoch, when the most massive structures form by gravitational
collapse, it should be expected that comoving space evolves inhomogeneous
curvature as structure grows. The BAO peak standard ruler should also follow
this inhomogeneous evolution if the comoving rigidity assumption is false. This
"standard" ruler has now been detected to be flexible, as expected under
general relativity.
