  In phenomenological applications, time evolutions of Bloch-Redfield type are
widely adopted for modelling open system dynamics, despite their non-positive
preserving character: this physical inconsistency, that in general shows up at
small times, is usually cured by suitably restricting the space of allowed
initial states. Nevertheless, additional problems may arise in relation to
entanglement: specifically, we show that Redfield dynamics can generate
entanglement through a purely local action, and this unphysical effect can
persist for finite times.
