# Looking beyond lambda

## TL;DR

This paper discusses the limitations of the standard $\\Lambda$CDM cosmological model, emphasizing the need to explore more complex dark sector physics as new data challenges existing assumptions.

## Contribution

It advocates for moving beyond the simple $w=-1$ paradigm, encouraging deeper investigation into dark matter, dark energy, and gravity with upcoming data and revised scientific practices.

## Key findings

- Current data shows cracks in the $\\Lambda$CDM model.
- Testing $w=-1$ is no longer sufficient for understanding dark energy.
- Future observations and methods are crucial for progress.

## Abstract

Widening cracks are appearing in the $\Lambda$CDM model and it is becoming increasingly clear that the standard cosmological model struggles to describe the full expansion history of the Universe as revealed by the Cosmic Microwave Background, Baryon Acoustic Oscillation measurements, and locally calibrated Type Ia supernovae. Taken at face value, recent results suggest a dark sector that may be more complex than commonly assumed. We must prepare for the possibility of moving beyond the $\Lambda$CDM era, where merely testing $w=-1$ is no longer sufficient, and embrace the challenge of unraveling the physics of dark matter, dark energy and gravity on cosmic scales. Guided by increasingly robust data - secured through considerable investment - we should pursue deeper understanding while being open to complexity in the dark sector, rather than settling for the simplest phenomenology. New data from new facilities and a new dark energy task force could help illuminate the path forward while changes to our scientific practices will be essential to navigate the potentially rocky road ahead.