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Questions about K3 surfaces, which are smooth complex surfaces $X$ with trivial canonical bundle and vanishing $H^1(O_X)$. They are examples of Calabi-Yau varieties of dimension $2$.

0 votes
2 answers
500 views

K3 surface with a non-symplectic involution: a basic question

Let $X$ be a K3 surface (algebraic, complex). An involution $\sigma:X\rightarrow X$ is called non-symplectic if it acts trivially on $H^{2,0}(X)=\Bbb{C}\omega_X$ $\ $ (where $\omega_X$ is any nowhere …
Heitor's user avatar
  • 761
2 votes
2 answers
1k views

Nefness on a K3 surface

Let $D$ be a divisor on a (complex) K3 surface. Suppose $D^2\geq0$. In general, $D$ is nef if $D\cdot C\geq0$ for all irreducible curves on the surface. Is it sufficient in our case to check this for …
Heitor's user avatar
  • 761
1 vote
1 answer
179 views

Characterization of $d$-gonal curves on a K3 surface

Let $X$ be a K3 surface and $C$ a curve on $X$. We say that $C$ is $d$-gonal if it admits a pencil of degree $d$ (and none of smaller degree). I am wondering if there exist characterizations of $d$- …
Heitor's user avatar
  • 761
5 votes
1 answer
328 views

Positivity question on K3 surfaces

Let $X$ be a smooth projective complex K3 surface and $L, D$ two effective divisors, $L^2\geq0$ and $D^2\geq0$. (Q1). do we have $L\cdot D\geq0$ ? If either one has positive self-intersection, the …
Heitor's user avatar
  • 761
2 votes
1 answer
197 views

Weyl group of a K3 surface

I am wondering wether the action of the Weyl group $W_X$ of a K3 surface $X$ is transitive on the sets of curves of fixed genus. Suppose $W_X$ is non-trivial. Given two curves $C,C'$ of genus $g\geq …
Heitor's user avatar
  • 761
5 votes
2 answers
464 views

Reference for Automorphisms of K3 surfaces

I am looking for some introductory reference concerning Automorphisms (of finite order) on K3 surfaces. Any suggestion?
Heitor's user avatar
  • 761
5 votes
1 answer
301 views

Does $h^1(D)=0$ imply numerical connectedness on K3 surfaces?

Let $X$ be a complex K3 surface and $D$ an effective divisor on $X$. We shall say: $D$ is connected if its support is connected. $D$ is numerically connected if for any non-trivial effective decompo …
Heitor's user avatar
  • 761