Seminario extraordinario IATE

Título: “Let us bury the prehistoric h: arguments against using Mpc/h units in cosmology”

Expositor: Dr. Ariel Sánchez (Max Planck Institute for Extraterrestrial Physics, Alemania)

Fecha: Miércoles 4 de marzo de 2020, 11 hs, Auditorio IATE.

Resumen: It is common to express cosmological measurements in units of Mpc/h. Here, we review some of the complications that originate from this practice. A crucial problem caused by these units is related to the normalization of the matter power spectrum, which is commonly characterized in terms of the linear-theory rms mass fluctuation in spheres of radius 8 Mpc/h, sigma_8. This parameter does not correctly capture the impact of h on the amplitude of density fluctuations. We show that the use of sigma_8 has caused critical misconceptions for both the so-called sigma_8 tension regarding the consistency between low-redshift probes and cosmic microwave background data, and the way in which growth-rate estimates inferred from redshift-space distortions are commonly expressed. We propose to abandon the use of Mpc/h units in cosmology and to characterize the amplitude of the matter power spectrum in terms of sigma_12, defined as the mass fluctuation in spheres of radius 12 Mpc, whose value is similar to the standard sigma_8 for h ~ 0.67.

Sobre el expositor: El Dr. Ariel Sánchez es graduado de la UNC en Astronomía. Trabaja en el Max Planck Institute for Extraterrestrial Physics, de Alemania, desde el año 2008. Participa de numerosos proyectos internacionales como el Baryon Oscillation Spectroscopic Survey (BOSS) del SDSS III, el Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) y la misión Euclid.