A full relativistic model suggests that the signature of EMRIs – inward spirals of a small black hole into a supermassive black hole – will carry “fingerprints” of dark matter concentrations, which future detectors like LISA could measure over months and years.
A new study by scientists at the University of Amsterdam describes how gravitational waves generated by black holes could provide a way to detect dark matter and learn more about its behavior. The study presents a sophisticated method for predicting how dark matter near a black hole could affect the gravitational waves these systems generate. A central role is played by a model based on Einstein's general theory of relativity that describes, with great precision, how a black hole and nearby matter interact.
Future space missions like the European Space Agency's LISA space antenna, scheduled for launch in 2035, are expected to record these signals for months or even years, tracking hundreds of thousands to millions of laps. If the models are built correctly, these cosmic "fingerprints" could reveal how matter—especially the mysterious dark matter thought to make up most of the matter in the universe—is distributed in the immediate vicinity of massive black holes.
Relativistic point of view
Before missions like LISA can start collecting data, it is essential to predict in detail the kind of data we should expect and how to extract the most information from them. Until now, most studies have relied on simplified descriptions of how the environment affects EMRIs. The new study closes this gap for a wide range of environments. It provides the first fully relativistic framework—that is, using Einstein's theory of gravity in its entirety, rather than simpler approximations based on Newtonian gravity—to describe how the environment of a massive black hole alters the trajectory of EMRIs and the resulting gravitational waves.
The study focuses specifically on dense concentrations of dark matter – also known as “spikelets” or “wires” – that may form around massive black holes. By combining their new relativistic description with state-of-the-art wave-form models, the authors show how such structures will leave a measurable imprint on the signals recorded by future detectors. This research is a major step in a long-term plan to use gravitational waves to map the distribution of dark matter in the universe and shed light on its fundamental nature.
More of the topic in Hayadan:
