Hilbert scheme of linearly normal curves in Pr\mathbb{P}^r with index of speciality five and beyond

We study the Hilbert scheme of smooth, irreducible, non-degenerate and linearly normal curves of degree $d$ and genus $g$ in $\mathbb{P}^r$ ($r\ge 3$) whose complete and very ample hyperplane linear series $\mathcal{D}$ have relatively small index of speciality $i(\mathcal{D})=g-d+r$. In particular we determine the existence as well as the non-existence of Hilbert schemes of linearly normal curves $\mathcal{H}^{\mathcal{L}}_{d,g,r}$ for every possible triples $(d,g,r)$ with $i(\mathcal{D})=5$ and $r\ge 3$. We also determine the irreducibility of the Hilbert scheme $\mathcal{H}^{\mathcal{L}}_{g+r-5,g,r}$ when the genus $g$ is near to the minimal possible value with respect to the dimension of the projective space $\mathbb{P}^r$ for which $\mathcal{H}^{\mathcal{L}}_{g+r-5,g,r}\neq\emptyset$, say $r+9\le g\le r+11$. In the course of proofs of key results, we show the existence of linearly normal curves of degree $d\ge g+1$ with arbitrarily given index of speciality with some mild restriction on the genus $g$.Comment: 60 pages, added two figures illustrating main results and corrected typo

On the Hilbert scheme of linearly normal curves in Pr\mathbb{P}^r with small index of speciality

We study the Hilbert scheme of smooth, irreducible, non-degenerate and linearly normal curves of degree $d$ and genus $g$ in $\mathbb{P}^r$ whose complete and very ample hyperplane linear series $\mathcal{D}$ have relatively small index of speciality $i(\mathcal{D})=g-d+r$. In particular we show the existence and the non-existence of certain Hilbert schemes with $i(\mathcal{D})=4$. We also determine the irreducibility of $\mathcal{H}^\mathcal{L}_{2r+4,r+8,r}$ for $3\le r\le 8$, which are rather peculiar families in some sense.Comment: 25 pages. Comments are very welcome. arXiv admin note: text overlap with arXiv:2101.0055

On the Hilbert scheme of smooth curves of degree 1515 and genus 1414 in P5\mathbb{P}^5

We denote by $\mathcal{H}_{d,g,r}$ the Hilbert scheme of smooth curves, which is the union of components whose general point corresponds to a smooth irreducible and non-degenerate curve of degree $d$ and genus $g$ in $\mathbb{P}^r$. In this article, we show that $\mathcal{H}_{15,14,5}$ is non empty and reducible with two components of the expected dimension hence generically reduced. We also study the birationality of the moduli map up to projective motion and several key properties such as gonality of a general element as well as specifying smooth elements of each components.Comment: Final version; corrected many typos in the exposition. To appear in Bollettino dell'Unione Matematica Italian

On the Hilbert scheme of smooth curves of degree d=15d=15 in P5\mathbb{P}^5

We denote by $\mathcal{H}_{d,g,r}$ the Hilbert scheme of smooth curves, which is the union of components whose general point corresponds to a smooth irreducible and non-degenerate curve of degree $d$ and genus $g$ in $\mathbb{P}^r$. In this article, we study $\mathcal{H}_{15,g,5}$ for every possible genus $g$ and determine their irreducibility. We also study the birationality of the moduli map up to projective equivalence and several key properties such as gonality of a general element as well as characterizing smooth elements of each component.Comment: Incorrect statement in Remark 3.8 has been corrected. Several typos has been fixe