Update on the search for topological dark matter using the GPS atomic clocks.

We use the Global Positioning System (GPS), comprised of nominally 32 atomic microwave clocks, as a 50,000 km-diameter network of quantum sensors capable of searching for exotic physics, such as "clumpy" dark matter (DM). We search for ultralight, self-interacting quantum fields that form macroscopic DM objects, e.g., 2D domain walls. Encounters between the GPS constellation and 2D domain walls would cause a sequence of atomic clock perturbations, imprinting a certain sweeping signature across the network. Recently, we have performed a search for these DM signatures, investigating 20 years of archival GPS atomic clock data. The search algorithm flagged about 600 candidate events. However, the velocity distribution of the candidate events is not consistent with the expected dark matter velocity distribution. We found that a large fraction of candidate events correspond to several potential events occurring nearly simultaneously. We are working on implementing a more sophisticated search algorithm to filter out these overlapping events.