Probing the Anisotropic Universe with Gravitational Waves

Understand

Modern cosmology rests on the working assumption that the Universe is isotropic and homogeneous at large scales.

• Here, we document a number of anomalous observations pointing to an anisotropic Universe in a direction consistent with the CMB dipole.
• If physical, this should be confirmed by any cosmological probe with sufficient data quality.
• To that end, we perform the first hemispherical decomposition of bright and dark standard siren $H_0$ determinations, finding that the maximum of the $H_0$ posterior is larger in the CMB dipole direction for dark sirens, but including the bright siren posterior reverses this conclusion.