  We study the case of multi-component dark matter, in particular how direct
detection signals are modified in the presence of several stable
weakly-interacting-massive particles. Assuming a positive signal in a future
direct detection experiment, stemming from two dark matter components, we study
the region in parameter space where it is possible to distinguish a one from a
two-component dark matter spectrum. First, we leave as free parameters the two
dark matter masses and show that the two hypotheses can be significantly
discriminated for a range of dark matter masses with their splitting being the
critical factor. We then investigate how including the effects of different
interaction strengths, local densities or velocity dispersions for the two
components modifies these conclusions. We also consider the case of
isospin-violating couplings. In all scenarios, we show results for various
types of nuclei both for elastic spin-independent and spin-dependent
interactions. Finally, assuming that the two-component hypothesis is confirmed,
we quantify the accuracy with which the parameters can be extracted and discuss
the different degeneracies that occur. This includes studying the case in which
only a single experiment observes a signal, and also the scenario of having two
signals from two different experiments, in which case the ratios of the
couplings to neutrons and protons may also be extracted.
