Detecting additional polarization modes with LISA

Within the frame of Einstein's General Relativity, gravitational waves are expected to possess two tensorial polarizations, namely the well-known h+ and h× modes, whereas more general metric theories of gravity however allow the existence of additional modes (up to two vector and two scalar modes). The (non-)observation of those additional polarizations could put constraints on alternative theories and consequently provide a further test for General Relativity. We address the question of whether a given LISA configuration can provide a sufficient sensitivity to detect additional polarization modes and then allow the extraction of the latter in order to determine the GW spectrum for each mode.