LISA: Making sense of a Universe Full of Signals

Lorenzo Speri

ESA Research Fellow

The Laser Interferometer Space Antenna (LISA) will open a new window on the Universe by observing gravitational waves in the millihertz band. Its observations will span an extraordinary range of astrophysical phenomena, from compact binaries in our own Galaxy to massive black-hole mergers billions of light-years away. But these sources will not arrive as neatly separated signals: many will overlap, some will remain unresolved, and the instrumental noise itself will need to be understood.

How do we extract reliable scientific information when we do not know in advance how many signals are present, where they are, or how they overlap?

This talk explores how different astrophysical sources produce distinct signal morphologies that motivate different data-analysis strategies. We will look at matched filtering, semi-coherent searches for extreme mass-ratio inspirals, and Bayesian methods for jointly inferring signals when the number of sources is unknown. We will examine how these approaches work and how to quantify the astrophysical information that can be extracted from future LISA observations.

The challenge is not simply to detect more gravitational waves, but to develop reliable methods for turning complex observations into astrophysical knowledge.