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Let $\overline{M}_{0,k}(\mathbb{P}^n,d)$

denote the moduli space of genus zero degree $d$ stable maps with $k$ marked points. This is an orbifold of expected dimension. Let $\overline{U}_{0,k}(\mathbb{P}^n,d)$ be the corresponding universal curve. Then we have two morphisms

$$\pi_1: \overline{U}{0,k}(\mathbb{P}^n,d) overline{U}_{0,k}(\mathbb{P}^n,d) \rightarrow \overline{M}{0,k}(\mathbb{P}^n,d)$$overline{M}_{0,k}(\mathbb{P}^n,d)$$

and

$$\pi_2: \overline{U}_{0,k}(\mathbb{P}^n,d) \rightarrow \mathbb{P}^n$$

So if we have a coherent sheaf $F$ on $\mathbb{P}^n$ we can pull it back to universal curve and push it forward to moduli space, i.e. we can consider $F_i=(R^i\pi_{1*})(\pi_2^*F)$ on moduli space.

Here are my questions:

1) Are $F_i$ zero for $i>0$ ? (is $\pi_{1*}$ exact )

2) If $F$ is equal to ideal sheaf of some smooth projective subvariety $X$, and $\beta \in H_2(X)$ is of degree $d$, then is there in general any relation between some component of support of $F_0$ and the moduli space $\overline{M}_{0,k}(X,\beta)$ ?

3) if the answer to question one is No, what is the interpretation of $F_i$, $i>0$, for the case when $F$ is the ideal sheaf of $X$ as in question two?

show/hide this revision's text 2 deleted 3 characters in body; added 4 characters in body

Let $\overline{M}_{0,k}(\mathbb{P}^n,d)$

denote the moduli space of genus zero degree $d$ stable maps with $k$ marked points. This is an orbifold of expected dimension. Let $\overline{U}_{0,k}(\mathbb{P}^n,d)$ be the corresponding universal curve. Then we have two morphisms

$$\pi_1: \overline{U}{0,k}(\mathbb{P}^n,d) \rightarrow \overline{M}{0,k}(\mathbb{P}^n,d)$$

and

$$\pi_2: \overline{U}_{0,k}(\mathbb{P}^n,d) \rightarrow \mathbb{P}^n$$

So if we have a coherent sheaf $F$ on $\mathbb{P}^n$ we can pull it back to universal curve and push it forward to moduli space, i.e. we can consider $F_i=(R^i\pi_{1*})(\pi_2^*F)$ on moduli space.

Here are my questions:

1) Are $F_i$ zero for $i>0$ ? (is $\pi_{1*}$ exact )

2) If $F$ is equal to ideal sheaf of some smooth projective subvariety $X$, and $\beta \in H_2(X)$ is of degree $d$, then is there in general any relation between some component of support of $F_0$ and the moduli space $\overline{M}_{0,k}(X,\beta)$ ?

3) if the answer to question one is No, what is the interpretation of $F_i$, $i>0$, for the case when $F$ is the ideal sheaf of $X$ as in question two?

show/hide this revision's text 1

Some questions on moduli of stable maps

Let $\overline{M}_{0,k}(\mathbb{P}^n,d)$

denote the moduli space of genus zero degree $d$ stable maps with $k$ marked points. This is an orbifold of expected dimension. Let $\overline{U}_{0,k}(\mathbb{P}^n,d)$ be the corresponding universal curve. Then we have two morphisms

$$\pi_1: \overline{U}{0,k}(\mathbb{P}^n,d) \rightarrow \overline{M}{0,k}(\mathbb{P}^n,d)$$

and

$$\pi_2: \overline{U}_{0,k}(\mathbb{P}^n,d) \rightarrow \mathbb{P}^n$$

So if we have a coherent sheaf $F$ on $\mathbb{P}^n$ we can pull it back to universal curve and push it forward to moduli space, i.e. we can consider $F_i=(R^i\pi_{1*})(\pi_2^*F)$ on moduli space.

Here are my questions:

1) Are $F_i$ zero for $i>0$ ? (is $\pi_{1*}$ exact )

2) If $F$ is equal to ideal sheaf of some smooth projective subvariety $X$, and $\beta \in H_2(X)$ is of degree $d$, then is there in general any relation between some component of support of $F_0$ and the moduli space $\overline{M}_{0,k}(X,\beta)$ ?

3) if the answer to question one is No, what is the interpretation of $F_i$, $i>0$, for the case when $F$ is the ideal sheaf of $X$ as in question two?