Farrar's primary research goal is discovering the identify of the Dark Matter which comprises more than 80% of the matter in the Universe, yet does not contain protons and neutrons making it fundamentally different than any known type of matter. She is currently investigating whether it can be composed of quarks in a hard-to-discern form that has eluded discovery, or must be evidence of an entirely new sub-nuclear world as usually assumed. Other interests are the origin of the excess of matter over anti-matter (without which the Universe would be devoid of galaxies, stars and life), the strong CP puzzle (why the neutron electric dipole moment is a billion times smaller than expected), the origin of the Galactic magnetic field and sources of Ultrahigh Energy Cosmic Rays (UHECRs).
Prof. Farrar has made seminal contributions to theoretical particle physics, including demonstrating that quarks are not just mathematical constructs but are actually physically present in matter (Brodsky-Farrar 1973) and pioneering the search for supersymmetry (Farrar-Fayet 1976), a prime objective of the Large Hadron Collider. With students she also made fundamental contributions to astrophysics: discovering the existence of an unexpected large-scale poloidal component of the magnetic field of the Milky Way (Jansson-Farrar 2012) and uncovering the first unambiguous examples of “stellar tidal disruption” when a supermassive black hole tears a passing star to shreds (vanVelzen-Farrar+ 2011). She proposed (with Gruzinov, 2009) that transient events may be the primary source of UHECRs, co-authored (as part of the Pierre Auger Collaboration) the influential paper on multi-messenger observations of the binary neutron star merger GW170817, and co-authored a paper (Stein et al, 2021) reporting the coincident arrival of an astrophysical neutrino with a tidal disruption event.
Farrar's current work centers on QCD, Dark Matter, Ultrahigh Energy Cosmic Rays, and the magnetic field of the Milky Way. Primariliy with students and postdocs, she has placed important indirect constraints on the sources of UHECRs (Ding, Globus, Farrar 2021; Muzio-Farrar 2023), interactions of DM with baryons (Xu, Wang, Farrar in various combinations, 2021-2023) and with KIT senior researcher Unger has developed a new suite of models of the Galactic magnetic field (Unger, Farrar 2023) .