English

On the Stein framing number of a knot

Geometric Topology 2017-10-24 v1 Symplectic Geometry

Abstract

For an integer nn, write Xn(K)X_n(K) for the 4-manifold obtained by attaching a 2-handle to the 4-ball along the knot KS3K\subset S^3 with framing nn. It is known that if n<tb(K)n< \overline{\text{tb}}(K), then Xn(K)X_n(K) admits the structure of a Stein domain, and moreover the adjunction inequality implies there is an upper bound on the value of nn such that Xn(K)X_n(K) is Stein. We provide examples of knots KK and integers ntb(K)n\geq \overline{\text{tb}}(K) for which Xn(K)X_n(K) is Stein, answering an open question in the field. In fact, our family of examples shows that the largest framing such that the manifold Xn(K)X_n(K) admits a Stein structure can be arbitrarily larger than tb(K)\overline{\text{tb}}(K). We also provide an upper bound on the Stein framings for KK that is typically stronger than that coming from the adjunction inequality.

Keywords

Cite

@article{arxiv.1710.08346,
  title  = {On the Stein framing number of a knot},
  author = {Thomas E. Mark and Lisa Piccirillo and Faramarz Vafaee},
  journal= {arXiv preprint arXiv:1710.08346},
  year   = {2017}
}

Comments

21 pages, 15 figures