A no-pure-boost uncertainty principle from spacetime noncommutativity

We study boost and space-rotation transformations in κ-Minkowski noncommutative spacetime, using the techniques that some of us had previously developed [A. Agostini, G. Amelino-Camelia, M. Arzano, A. Marciano, R.A. Tacchi, hep-th/0607221] for a description of translations in κ-Minkowski, which in particular led to the introduction of translation transformation parameters that do not commute with the spacetime coordinates. We find a similar description of boosts and space rotations, which allows us to identify some associated conserved charges, but the form of the commutators between transformation parameters and spacetime coordinates is incompatible with the possibility of a pure boost.