Deformations of M-theory Killing superalgebras

We classify the Lie superalgebra deformations of the Killing superalgebras of some M-theory backgrounds. We show that the Killing superalgebras of the Minkowski, Freund–Rubin and M5-brane backgrounds are rigid, whereas the ones for the M-wave, the Kaluza–Klein monopole and the M2-brane admit deformations, which we give explicitly.