Absolute points of correlations of $PG(3,q^n)$

The sets of the absolute points of (possibly degenerate) polarities of a projective space are well known. The sets of the absolute points of (possibly degenerate) correlations, different from polarities, of PG(2, qn), have been completely determined by B.C. Kestenband in 11 papers from 1990 to 2014, for non-degenerate correlations and by D’haeseleer and Durante (Electron J Combin 27(2):2–32, 2020) for degenerate correlations. In this paper, we completely determine the sets of the absolute points of degenerate correlations, different from degenerate polarities, of a projective space PG(3, qn). As an application we show that, for q even, some of these sets are related to the Segre’s (2h +1)-arc of PG(3, 2n) and to the Lüneburg spread of PG(3, 22h+1).