Time travelers
The Living Receiver
The choice of Donnie as a Living Receiver seems to follow a principle of proximity.
The Tangent Universe occurs right above Donnie's house. However, it is worthwhile to interrogate ourselves whether this choice may be fortified by his mental health condition, as schizophrenia and the psychotic component thereof would seem to malleate the sufferer's perception to the possibility of otherworldly phenomena, including the divine.
However, every living creature on Earth dies alone and Donnie struggles with this notion incredibly - we may go as far as to perceive it to be the devastating reason for Donnie's actions thereafter up until the very end of the narrative.
Finally, Donnie's interest in physics seems to predispose him to an affinity for the scientific logic of time-travel.
