An Update on the Classification of Rank 2 Weak Fano Threefolds

Abstract

In this paper, an update on the classification of smooth weak Fano threefolds with Picard number two and small anti-canonical maps is given. Geometric constructions are provided for previously open numerical cases by blowing up certain curves on smooth Fano threefolds of Picard number one. This paper provides updated tables in the Appendix and reduces the 14 remaining E1-E* open cases to four.

Minor edits for clarity from referee comments made from prior version; accepted to Taiwanese J. of Math