Challenges to the Lambda CDM Cosmology

TL;DR

This paper reviews current challenges and tensions faced by the Lambda CDM cosmology, especially regarding measurements of the Hubble constant, weak lensing, and evolving dark energy, highlighting unresolved fundamental questions.

Contribution

It provides a comprehensive review of observational tensions with Lambda CDM, emphasizing the need to understand dark matter, dark energy, and inflation at a fundamental level.

Findings

Tensions between CMB and local H_0 measurements.

Discrepancies in weak gravitational lensing data.

Hints of evolving dark energy from DESI observations.

Abstract

Observations of the cosmic microwave backgroundradiation are described to remarkable accuracy by the six-parameterLambda CDM cosmology. However, the key ingredients of this model, namely dark matter, dark energy and cosmic inflation are not understood at a fundamental level. It is therefore important to investigate tensions between the CMB and other cosmological probes. I will review aspects of tensions with direct measurements of the Hubble constant H_0, measurements of weak gravitational lensing, and the recent hints of evolving dark energy reported by the Dark Energy Spectroscopic Instrument (DESI) collaboration.