The Memory Effect of Gravitational Waves in General Relativity

A major goal of General Relativity (GR) is to precisely describe and finally observe gravitational radiation, one of the predictions of GR. In order to do so, one has to study the spacetimes for typical sources. Among the latter we find binary neutron stars and binary black hole mergers or core-collapse supernovae. In these processes typically mass and momenta are radiated away in form of gravitational waves. These waves leave a footprint in the spacetime, that is they displace test masses permanently. This effect is called the memory. In this talk, I will explore the gravitational memory. We will see that there are two types of memory, one going back to Ya. B. Zel'dovich and A. G. Polnarev and one to D. Christodoulou. Then I will discuss recent work in collaboration with D. Garfinkle, S.-T. Yau, P. Chen, focusing on how neutrinos or electromagnetic fields contribute to the memory effect. Moreover, recent results on memory in other fields will be mentioned such as my collaboration with D. Garfinkle concerning electromagnetic radiation, and A. Strominger with A. Zhiboedov in quantum field theory.