0-Concordance of 2-knots
Nathan Sunukjian
In this paper we investigate the 0-concordance classes of 2-knots in $S^4$,
an equivalence relation that is related to understanding smooth structures on
4-manifolds. Using Rochlin's invariant, and invariants arising from
Heegaard-Floer homology, we will prove that there are infinitely many
0-concordance classes of 2-knots.