TY - JOUR

T1 - A measurement of the scale of homogeneity in the early Universe

AU - Camacho-Quevedo, Benjamin

AU - Gaztañaga, Enrique

N1 - Publisher Copyright:
© 2022 IOP Publishing Ltd and Sissa Medialab.

PY - 2022/4/21

Y1 - 2022/4/21

N2 - We present the first measurement of the homogeneity index, H, a fractal or Hausdorff dimension of the early Universe from the Planck CMB temperature variations δT in the sky. This characterization of the isotropy scale is model-free and purely geometrical, independent of the amplitude of δT. We find evidence of homogeneity (H = 0) for scales larger than θH = 65.9 ± 9.2 deg on the CMB sky. This finding is at odds with the ΛCDM prediction, which assumes a scale invariant infinite universe. Such anomaly is consistent with the well known low quadrupule amplitude in the angular δT spectrum, but quantified in a direct and model independent way. We estimate the significance of our finding for H = 0 using a principal component analysis from the sampling variations of the observed sky. This analysis is validated with theoretical prediction of the covariance matrix and simulations, booth base purely on data or in the ΛCDM prediction. Assuming translation invariance (and flat geometry) we can convert the isotropy scale θH into a (comoving) homogeneity scale which is very close to the trapped surface generated by the observed cosmological constant Λ.

AB - We present the first measurement of the homogeneity index, H, a fractal or Hausdorff dimension of the early Universe from the Planck CMB temperature variations δT in the sky. This characterization of the isotropy scale is model-free and purely geometrical, independent of the amplitude of δT. We find evidence of homogeneity (H = 0) for scales larger than θH = 65.9 ± 9.2 deg on the CMB sky. This finding is at odds with the ΛCDM prediction, which assumes a scale invariant infinite universe. Such anomaly is consistent with the well known low quadrupule amplitude in the angular δT spectrum, but quantified in a direct and model independent way. We estimate the significance of our finding for H = 0 using a principal component analysis from the sampling variations of the observed sky. This analysis is validated with theoretical prediction of the covariance matrix and simulations, booth base purely on data or in the ΛCDM prediction. Assuming translation invariance (and flat geometry) we can convert the isotropy scale θH into a (comoving) homogeneity scale which is very close to the trapped surface generated by the observed cosmological constant Λ.

KW - CMBR experiments

KW - dark energy experiments

KW - physics of the early universe

KW - Statistical sampling techniques

UR - http://www.scopus.com/inward/record.url?scp=85129520720&partnerID=8YFLogxK

U2 - 10.1088/1475-7516/2022/04/044

DO - 10.1088/1475-7516/2022/04/044

M3 - Article

AN - SCOPUS:85129520720

SN - 1475-7516

VL - 2022

JO - Journal of Cosmology and Astroparticle Physics

JF - Journal of Cosmology and Astroparticle Physics

IS - 4

M1 - 044

ER -