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Dusty Madison: Searching for the Universe's Memory: It Only Sounds Like a Crazy Idea

WVU Department of Physics and Astronomy

Gravitational waves (GWs) leave in their wake a permanent residual distortion of space referred to as “memory.” Formally, memory accumulates over the entire history of gravitationally radiating systems, but it grows especially rapidly during bright GW events like the final mergers of binary black holes. Such events are called bursts with memory (BWMs). From an observational perspective, BWMs generate long-lasting redshifts and permanent angular deflections in distant sources of light. Unlike purely transient GW events, BWMs can superpose and reinforce one another over cosmological time scales, leading to bigger and bigger perturbations in the appearance of more distant sources of light. The largest possible manifestation of this signal, built up over nearly the entire history of the Universe, will lie in the cosmic microwave background, the most ancient light in existence. I’ll discuss recent efforts to understand this problem and future projects to determine if this signature can be detected.