Orateur
Description
Modern cosmology is entering a critical phase, as increasingly precise measurements from multiple standard probes have unveiled tensions that may hint at new physics. Whether these discrepancies arise from unaccounted systematics or signal a genuine crisis in our understanding of the Universe is still an open question. In this context, it becomes crucial to explore independent and complementary approaches to constrain cosmology.
In this talk, I will present two independent and novel ways to tackle the expansion history of the Universe without relying on distance ladder calibration, cosmic Chronometers (CC) and Gravitational Wave standard sirens (GW).
Cosmic Chronometers exploit the differential age evolution of passively evolving galaxies to directly measure the Hubble parameter H(z), providing a fully cosmology-independent reconstruction of the expansion history. Gravitational Wave standard sirens, on the other hand, offer an absolute measurement of luminosity distances through the direct observation of compact binary mergers, independently anchoring the cosmic distance scale.
I will discuss the current status of both methods, their individual strengths and limitations, and, crucially, their synergy: used in combination, CC and GW probe complementary aspects of cosmic expansion and offer a joint pathway to address the Hubble tension with minimal theoretical assumptions. Finally, I will explore how ongoing and upcoming surveys and observatories (such as Euclid, WST, and next-generation GW detectors like Einstein Telescope and LISA) will dramatically improve the constraining power of both probes, paving the way toward their full inclusion in the era of precision cosmology.