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Dmitri Panov
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Let us prove that any non-simply connected surface without curves of negative self-intersection provides a counterexampleThis answer is completely rewritten. This includes Abelian surfaces and generic products of curves of higher genusis not an actual answer but a thought related to the question. I decided to leave it hear since it is short.

Proof. Suppose Note first that $X$if there is a regular map from a surface with$X$ to $\mathbb P^3$ whose image has only isolated singularities in, then $\mathbb CP^3$. Then the sinuglarities of the surfaces are normal. Hence the minimal resolution of these singularities must have$X$ has curves with negative negative self-intersections (that project to singularity)intersection. SoIn particular, if the resolution does not have$X$ has no such curves, then its image in $X$$\mathbb P^3$ is non-singularsmooth. It follows that

Now, suppose we have a surface $X$ has trivial fundamental group.with isolated singularities in $\mathbb CP^3$, say of general type and consider the question:

CorrectionQuestion. I see now that in order for this reasoning to work one has to guarantee that onLet $X'$ be the minimal resolution of singularities ofon $X$ there are no rational $-1$-curves. I wonder if this holds indeed provided the degree of Can we say something about $X$ is high enough. Or maybe one can "classify" surfaces inif $\mathbb CP^3$ for which this statement fails. So I still believe this idea can work out...$X'$ contains rational $-1$ curves?

Let us prove that any non-simply connected surface without curves of negative self-intersection provides a counterexample. This includes Abelian surfaces and generic products of curves of higher genus.

Proof. Suppose that $X$ is a surface with isolated singularities in $\mathbb CP^3$. Then the sinuglarities of the surfaces are normal. Hence the minimal resolution of these singularities must have curves with negative self-intersections (that project to singularity). So if the resolution does not have such curves, $X$ is non-singular. It follows that $X$ has trivial fundamental group.

Correction. I see now that in order for this reasoning to work one has to guarantee that on the minimal resolution of singularities of $X$ there are no rational $-1$-curves. I wonder if this holds indeed provided the degree of $X$ is high enough. Or maybe one can "classify" surfaces in $\mathbb CP^3$ for which this statement fails. So I still believe this idea can work out...

This answer is completely rewritten. This is not an actual answer but a thought related to the question. I decided to leave it hear since it is short.

Note first that if there is a regular map from a surface $X$ to $\mathbb P^3$ whose image has only isolated singularities, then $X$ has curves with negative self-intersection. In particular, if $X$ has no such curves then its image in $\mathbb P^3$ is smooth.

Now, suppose we have a surface $X$ with isolated singularities in $\mathbb CP^3$, say of general type and consider the question:

Question. Let $X'$ be the minimal resolution of singularities on $X$. Can we say something about $X$ if $X'$ contains rational $-1$ curves?

added 365 characters in body; added 20 characters in body
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Dmitri Panov
  • 28.9k
  • 4
  • 92
  • 161

Let us prove that any non-simply connected surface without curves of negative self-intersection provides a counterexample. This includes Abelian surfaces and generic products of curves of higher genus.

Proof. Suppose that $X$ is a surface with isolated singularities in $\mathbb CP^3$. Then the sinuglarities of the surfaces are normal. Hence the minimal resolution of these singularities must have curves with negative self-intersections (that project to singularity). So if the resolution does not have such curves, $X$ is non-singular. It follows that $X$ has trivial fundamental group.

Correction. I see now that in order for this reasoning to work one has to guarantee that on the minimal resolution of singularities of $X$ there are no rational $-1$-curves. I wonder if this holds indeed provided the degree of $X$ is high enough. Or maybe one can "classify" surfaces in $\mathbb CP^3$ for which this statement fails. So I still believe this idea can work out...

Let us prove that any non-simply connected surface without curves of negative self-intersection provides a counterexample. This includes Abelian surfaces and generic products of curves of higher genus.

Proof. Suppose that $X$ is a surface with isolated singularities in $\mathbb CP^3$. Then the sinuglarities of the surfaces are normal. Hence the minimal resolution of these singularities must have curves with negative self-intersections (that project to singularity). So if the resolution does not have such curves, $X$ is non-singular. It follows that $X$ has trivial fundamental group.

Let us prove that any non-simply connected surface without curves of negative self-intersection provides a counterexample. This includes Abelian surfaces and generic products of curves of higher genus.

Proof. Suppose that $X$ is a surface with isolated singularities in $\mathbb CP^3$. Then the sinuglarities of the surfaces are normal. Hence the minimal resolution of these singularities must have curves with negative self-intersections (that project to singularity). So if the resolution does not have such curves, $X$ is non-singular. It follows that $X$ has trivial fundamental group.

Correction. I see now that in order for this reasoning to work one has to guarantee that on the minimal resolution of singularities of $X$ there are no rational $-1$-curves. I wonder if this holds indeed provided the degree of $X$ is high enough. Or maybe one can "classify" surfaces in $\mathbb CP^3$ for which this statement fails. So I still believe this idea can work out...

Source Link
Dmitri Panov
  • 28.9k
  • 4
  • 92
  • 161

Let us prove that any non-simply connected surface without curves of negative self-intersection provides a counterexample. This includes Abelian surfaces and generic products of curves of higher genus.

Proof. Suppose that $X$ is a surface with isolated singularities in $\mathbb CP^3$. Then the sinuglarities of the surfaces are normal. Hence the minimal resolution of these singularities must have curves with negative self-intersections (that project to singularity). So if the resolution does not have such curves, $X$ is non-singular. It follows that $X$ has trivial fundamental group.