or OUTER LIMITS / FRINGES / DISTANT CONFINES / BORDERLINE FIELDS

A simple definition of frontier research could be “research taking place at the frontiers of knowledge,” perhaps qualifying this definition with “in a particular area or field.” This definition is clearly somewhat imprecise, however. Indeed, argu­ably it dodges the question, as it pushes the definition back a step, to the question of the frontiers of knowledge, and fails to offer a distinguishing feature with which to identify frontier research as all research is about something unknown and can potentially contribute new knowledge.

Others have correctly pointed out there are at least two different definitions involved here. Overlapping fields of study is one of them but it looks to me that 'interdisziplinäre Forschung in Grenzbereichen' is mentioned first for a reason and points in a different direction.

Compare with example below:

"We are considering here the effects of democratizing research at the edges of our respective fields, a back to the future move as Strafford [29] suggests in her study of the beginnings of 17th century science."

Research in "boundary areas" also sounds appropriate but probably not "fringe areas" as many would associate that term with outlandish or discredited ideas...

'Grenzbereiche' may also include research at the "frontier of our knowledge" although the focus is more on the "edges" of scientific disciplines, IMO.