3 research outputs found
Cosmic chronometers to calibrate the ladders and measure the curvature of the Universe. A model-independent study
We use the state-of-the-art data on cosmic chronometers (CCH) and the
Pantheon+ compilation of supernovae of Type Ia (SNIa) to test the constancy of
the SNIa absolute magnitude, , and the robustness of the cosmological
principle (CP) at with a model-agnostic approach. We do so by
reconstructing and the curvature parameter using
Gaussian Processes. Moreover, we use CCH in combination with radial and angular
data on baryon acoustic oscillations (BAO) from various galaxy surveys (6dFGS,
BOSS, eBOSS, WiggleZ, DES Y3) to measure the sound horizon at the baryon-drag
epoch, , from each BAO data point and check their consistency. Given the
precision allowed by the CCH data, we find that , and
are fully compatible (at C.L.) with constant values. This
justifies our final analyses, in which we put constraints on these constant
parameters under the validity of the CP, the metric description of gravity and
standard physics in the vicinity of the stellar objects, but otherwise in a
model-independent way. If we exclude the SNIa contained in the host galaxies
employed by SH0ES, our results read mag,
Mpc and ( C.L.).
These values have been obtained without using any information from the main
data sets involved in the tension, namely, the cosmic microwave
background and the first two rungs of the cosmic distance ladder. If, instead,
we also consider the SNIa in the host galaxies, calibrated with Cepheids, we
measure mag, Mpc
and .Comment: 17 pages, 10 figures, 5 table
Late-time phenomenology required to solve the tension in view of the cosmic ladders and the anisotropic and angular BAO data sets
The mismatch between the value of the Hubble parameter
measured by SH0ES and the one inferred from the inverse distance ladder (IDL)
constitutes the biggest tension afflicting the standard model of cosmology,
which could be pointing to the need of physics beyond CDM. In this
paper we study the background history required to solve the tension if we
consider standard prerecombination physics, paying special attention to the
role played by the data on baryon acoustic oscillations (BAO) employed to build
the IDL. We show that the anisotropic BAO data favor an ultra-late-time
(phantom-like) enhancement of at to solve the tension,
accompanied by a transition in the absolute magnitude of supernovae of Type Ia
in the same redshift range. The effective dark energy (DE) density must
be smaller than in the standard model at higher redshifts. Instead, when
angular BAO data (claimed to be less subject to model dependencies) is employed
in the analysis, we find that the increase of starts at much higher
redshifts, typically in the range . In this case, could
experience also a transition (although much smoother) and the effective DE
density becomes negative at . Both scenarios require a violation of
the weak energy condition (WEC), but leave an imprint on completely different
redshift ranges and might also have a different impact on the perturbed
observables. They allow for the effective crossing of the phantom divide.
Finally, we employ two alternative methods to show that current data from
cosmic chronometers do not exclude the violation of the WEC, but do not add any
strong evidence in its favor neither. Our work puts the accent on the utmost
importance of the choice of the BAO data set in the study of the possible
solutions to the tension.Comment: 20 pages, 13 figures, 3 table