Published online by Cambridge University Press: 05 January 2015
Abstract
We survey some recent progress in the classification of three-dimensional divisorial contractions to cE points. In particular, we introduce a new structure of three-dimensional cE singularity and use this structure to explain the work of Hayakawa. We also provide some new examples.
Dedicated to Rob Lazarsfeld on the occasion of his sixtieth birthday
1 Introduction
The minimal model program has been one of the main tools in the study of birational algebraic geometry. After some recent advances in the study of the geometry of complex 3-folds, one might hope to build up an explicit classification theory for 3-folds similar to the theory of surfaces by using the minimal model program.
In the minimal model program, divisorial contractions, flips, and flops are considered to be elementary maps. Any birational map obtained from the minimal model program consists of a combination of the above-mentioned maps. Let us briefly recall some known results about three-dimensional birational maps. First of all, Mori and then Cutkosky classified birational maps from nonsingular 3-folds and Gorenstein 3-folds respectively [4, 20]. Tziolas has produced a series of work on divisorial contractions to curves passing through Gorenstein singularities (cf. [23-25]). The recent project of Mori and Prokhorov (cf. [21, 22]) on extremal contractions provides a treatment which is valid for divisorial contractions to curves and for conic bundles. They classified completely divisorial contractions to curves of type IA, IC, and IIB. Flops are studied in Kollár's article [16]. Flips are still quite mysterious, except for some examples in [2, 18].
Divisorial contractions to points are probably the best understood, due mainly to the works of Kawamata, Hayakawa, Markushevich, and Kawakita (cf. [5-7, 10-15, 19]). Divisorial contractions to points of index > 1 are now completely classified and realized as weighted blow-ups. Therefore, it remains to consider contractions to points of index 1, i.e., terminal Gorenstein singularities. The description of contractions to index 1 points can be found in [13]. In fact, contractions to cA points are classified completely in [13]. Recently, Hayakawa started a project to classify contractions to cD and cE points [8, 9].
To save this book to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.