English

An adjunction inequality for Real embedded surfaces

Geometric Topology 2026-03-06 v2 Differential Geometry

Abstract

A Real structure on a 44-manifold XX is an orientation preserving smooth involution σ\sigma. We say that an embedded surface ΣX\Sigma \subset X is Real if σ\sigma maps Σ\Sigma to itself orientation reversingly. We prove that a cohomology class uH2(X;Z)u \in H^2(X ; \mathbb{Z}) can be represented by a Real embedded surface if and only if uu can be lifted to a class in equivariant cohomology HZ22(X;Z)H^2_{\mathbb{Z}_2}(X ; \mathbb{Z}_-). We prove that if the Real Seiberg--Witten invariants of XX are non-zero then the genus of Real embedded surfaces in XX satisfy an adjunction inequality. We prove two versions of the adjunction inequality, one for non-negative self-intersection and one for arbitrary self-intersection. We show with examples that the minimal genus of Real embedded surfaces can be larger than the minimal genus of arbitrary embedded surfaces.

Keywords

Cite

@article{arxiv.2507.05667,
  title  = {An adjunction inequality for Real embedded surfaces},
  author = {David Baraglia},
  journal= {arXiv preprint arXiv:2507.05667},
  year   = {2026}
}

Comments

25 pages, minor corrections. To appear in Int. Math. Res. Not

R2 v1 2026-07-01T03:50:47.957Z