Imprints of massive black-hole binaries on neighbouring decihertz gravitational-wave sources.

The most massive black holes in our Universe form binaries at the centre of merging galaxies. The recent evidence for a gravitational-wave (GW) background from pulsar timing may constitute the first observation that these supermassive black-hole binaries (SMBHBs) merge. Yet, the most massive SMBHBs are out of reach of interferometric GW detectors and are exceedingly difficult to resolve individually with pulsar timing.

Searching for Scalar Field Dark Matter with LIGO.

We report on a direct search for scalar field dark matter using data from LIGO's third observing run. We analyze the coupling of size oscillations of the interferometer's beam splitter and arm test masses that may be caused by scalar field dark matter. Using new efficient search methods to maximize sensitivity for signatures of such oscillations, we set new upper limits for the coupling constants of scalar field dark matter as a function of its mass, which improve upon bounds from previous direct searches by up to four orders of magnitude in a frequency band from 10 to 180 Hz.

Constraints on Scalar Field Dark Matter from Colocated Michelson Interferometers.

Low-mass (sub-eV) scalar field dark matter may induce apparent oscillations of fundamental constants, resulting in corresponding oscillations of the size and the index of refraction of solids. Laser interferometers are highly sensitive to changes in the size and index of refraction of the main beam splitter. Using cross-correlated data of the Fermilab Holometer instrument, which consists of twin colocated 40-m arm length power-recycled interferometers, we investigate the possible existence of scalar field dark matter candidates in the mass range between 1.

Direct limits for scalar field dark matter from a gravitational-wave detector.

The nature of dark matter remains unknown to date, although several candidate particles are being considered in a dynamically changing research landscape. Scalar field dark matter is a prominent option that is being explored with precision instruments, such as atomic clocks and optical cavities. Here we describe a direct search for scalar field dark matter using a gravitational-wave detector, which operates beyond the quantum shot-noise limit.