Why is it interesting to consider quantum field theories where Lorentz symmetry is explicitly broken? The set of power-counting renormalizable theories is considerably"small Relaxing some assumptions can enlarge it, but often it enlarges it too much Without locality in principle every theory can be made finite Without unitarity even gravity can be renormalizedThe set of power-counting renormalizable theories is considerably “small” Relaxing some assumptions can enlarge it, but often it enlarges it too much Without locality in principle every theory can be made finite Without unitarity even gravity can be renormalized Why is it interesting to consider quantum field theories where Lorentz symmetry is explicitly broken?