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two questions a question on the space of divisors on a curve

Let $X$ a complex curve and $x\in X$ a point.

We consider the space of effective divisors $D$ with fixed degree $d$, with no multiplicity outside the pointwhic we know is isomorphic to $x$ and with multiplicity less or equal than 2 at$X^{d}/S_{d}$ where $x$?

Why this space$S_{d}$ is not open?the symmetric group.

Now, we consider the same spacesubspace of divisors $D$ with fixed degree $d$ such that:

$\sum\limits_{x untransversal}m_{x}(D)\leq N.$

where the untransversal points means that $m_{x}(D)\geq 2$.

Is this space open in $X^{d}/S_{d}$?

two questions on the space of divisors on a curve

Let $X$ a complex curve and $x\in X$ a point.

We consider the space of divisors $D$ with fixed degree $d$, with no multiplicity outside the point $x$ and with multiplicity less or equal than 2 at $x$?

Why this space is not open?

Now, we consider the same space of divisors $D$ with fixed degree $d$ such that:

$\sum\limits_{x untransversal}m_{x}(D)\leq N.$

where the untransversal points means that $m_{x}(D)\geq 2$.

Is this space open?

a question on the space of divisors on a curve

Let $X$ a complex curve and $x\in X$ a point.

We consider the space of effective divisors $D$ with fixed degree $d$, whic we know is isomorphic to $X^{d}/S_{d}$ where $S_{d}$ is the symmetric group.

Now, we consider the subspace of divisors $D$ with fixed degree $d$ such that:

$\sum\limits_{x untransversal}m_{x}(D)\leq N.$

where the untransversal points means that $m_{x}(D)\geq 2$.

Is this space open in $X^{d}/S_{d}$?

Source Link
prochet
  • 3.5k
  • 1
  • 13
  • 20

two questions on the space of divisors on a curve

Let $X$ a complex curve and $x\in X$ a point.

We consider the space of divisors $D$ with fixed degree $d$, with no multiplicity outside the point $x$ and with multiplicity less or equal than 2 at $x$?

Why this space is not open?

Now, we consider the same space of divisors $D$ with fixed degree $d$ such that:

$\sum\limits_{x untransversal}m_{x}(D)\leq N.$

where the untransversal points means that $m_{x}(D)\geq 2$.

Is this space open?