January 30, 2026:
Ioannis Liodis
Affiliation: Deutsches Electron Syncrotron (DESY), and University of Potsdam, and Deutches Zentrum fur Astrophysik (DZA)
Title: Gravitational Wave Cosmology: From Standard to Biased Sirens
Abstract: Conventionally, compact binary mergers are used as standard sirens to infer cosmological parameters, since they may allow for joint measurements of their luminosity distance (D_L) and redshift (z). The most common assumption at the very first step of this process is that the binary evolves in vacuum. However, there is strong evidence that a significant fraction of mergers originate in Active Galactic Nucleus (AGN) disks, meaning that there will be a gaseous environment and third body contribution to the binary evolution. We show that neglecting these, so called, environmental effects in the waveform, leads to biased cosmological inference, severely limiting the prospects for alleviating the Hubble tension with standard sirens.
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