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8 votes
1 answer
789 views

What is the smallest and "best" 27 lines configuration? And what is its symmetry group?

I was this past year working with a bright high-schooler on algebraic geometry following Reid's book Undergraduate Algebraic Geometry, and we got all the way to proving that there is at least one line ...
David Roberts's user avatar
  • 35.5k
2 votes
0 answers
671 views

description of very ample bundle of Hirzebruch surface

I learned some basic properties of Hirzebruch surface mainly from Vakil's notes "the rising sea", section 20.2.9. the Hirzebruch surface is defined as $\mathbb{F}_n:=\operatorname{Proj} (\...
zxx's user avatar
  • 343
3 votes
1 answer
276 views

Mumford-Ramanujam examples in characteristic p [and in Arakelov geometry]

For a compact Riemann surface $B$ of genus $\geq 2$, it is a consequence of the Narasimhan-Seshadri theorem that there exist rank-$2$ vector bundles $E \to B$ of degree zero, all of whose symmetric ...
Vesselin Dimitrov's user avatar
11 votes
3 answers
2k views

Nonprojective Surface

Let k be an algebraically closed field. It's well known that every complete curve, period, is projective. Also, that every smooth surface is, and that there are smooth 3-folds which are not, and ...
Charles Siegel's user avatar