We prove two theorems which imply that any stationary nonlinear electromagnetic field obeying a dominant energy condition in strictly stationary, everywhere regular, asymptotically flat spacetime must be either trivial or stealth field. The first theorem holds static spacetimes and is independent of the gravitational part action, as long coupling to minimal. second assumes Einstein--Hilbert act...

Abstract We study (strictly) join irreducible varieties in the lattice of subvarieties residuated lattices. explore connections with well-connected algebras and suitable generalizations, focusing particular on representable varieties. Moreover, we find weakened notions Halldén completeness that characterize irreducibility. strictly basic hoops use generalized rotation construction to $\mathsf{M...