I'm not sure what you're looking for. EM fields so strong that they affect spacetime noticeably? We haven't observed any Reissner-Nordstrom/Kerr-Newman black h

I'm not sure what you're looking for. EM fields so strong that they affect spacetime noticeably? We haven't observed any Reissner-Nordstrom/Kerr-Newman black holes iirc. That said, _anything_ with stress-energy-momentum is held to affect spacetime curvature in GR.