Questions tagged [hilbert-function]
For questions on the Hilbert function and Hilbert polynomial of graded algebras over fields.
38 questions
Score of 4
0 answers
111 views
Is this rational function a Hilbert series?
This old MO question deserves renewed attention in my opinion. The original question defined
$$F_n(X) := \sum_{k=0}^n (-1)^k \binom{n}{k} X^{k(n-k)}$$
where $n=2m$ is an even integer, and asked for a ...
Score of 3
0 answers
115 views
Reference request: the Hilbert function is a piecewise quasi-polynomial function
Let $G$ be a finitely generated abelian group and $R$ a finitely generated $G$-graded ring. Then we can define the Hilbert function $H_R : G \to \mathbb{N}$ given by $g \mapsto \dim R_g$. I believe it ...
Score of 0
0 answers
134 views
Reconstructing a graded ring from its Hilbert function
Are there algorithmic procedures for constructing finitely-generated $\mathbb{Z}$-graded $\mathbb{C}$-algebras $R$, given knowledge of the Hilbert function?
That is, say I have a sequence $n_1, n_2, \...
Score of 2
0 answers
207 views
Index of regularity of zero-dimensional ideal
Let $I$ be a graded polynomial ideal of $\mathcal{S} = \mathbb{C}[x_1, \ldots, x_n]$, generated by homogeneous polynomials of degree $\leq d$.
As I understand, the Hilbert function of $I$ is the ...
Score of 3
0 answers
169 views
On multigraded Hilbert schemes
Recently I have come across the paper Multigraded Hilbert Schemes by Mark Haiman and Bernd Sturmfels, where they construct a very general object parametrizing homogeneous ideals with fixed Hilbert ...
Score of 1
1 answer
193 views
Existence of a regular sequence with degrees prescribed by the Hilbert series
Let $k$ be a field (assume $k=\mathbb{C}$ if necessary) and let $A=\bigoplus_{d=0}^\infty A_d$ be a finitely generated Gorenstein graded commutative $k$-algebra of Krull dimension $n$ with $A_0=k$. ...
Score of 4
1 answer
266 views
Order of pole of Poincaré series
Let $R = \bigoplus_{n \geq 0} R_n$ be a graded Noetherian ring and $M = \bigoplus_{n \geq 0} M_n$ a finitely generated graded $R$-module. Let $\lambda$ be an additive function on the class of all ...
Score of 2
1 answer
303 views
Hilbert–Samuel multiplicity under hypersurface sections
Let $\newcommand{\frakm}{\mathfrak{m}}(R,\frakm)$ be a reduced Noetherian local ring of dimension $d$ and $f\in\frakm^\alpha\setminus\frakm^{\alpha+1}$ a parameter of $R$, i.e. $\dim R/(f)=d-1$. Let $...
Score of 1
0 answers
87 views
Symmetric 0-dimensional schemes with generic Hilbert function and Grassmannians
I've came across this problem while thinking about some properties of fat schemes.
Let me give you an explicit (motivating) example:
We have $S=\mathbb{C}[x,y,z]$, the coordinate ring of $\mathbb{P}^2$...
Score of 12
2 answers
966 views
Hilbert polynomials of graded algebras evaluated at negative numbers
Let $k$ be a field and let $R$ be a commutative (standard) graded $k$-algebra, that is, $R=\bigoplus_{n=0}^\infty R_n$ with $R_0=k$ (and $R=k[R_1]$). The Hilbert function $h_R:\mathbb{N}\rightarrow \...
Score of 2
1 answer
578 views
When is Hilbert-Samuel multiplicity of a local ring non-increasing along localization at prime ideals?
For Noetherian local ring $(R,\mathfrak m)$, let $e(R)$ denote the Hilbert-Samuel multiplicity of $R$ with respect to $\mathfrak m$ (https://en.m.wikipedia.org/wiki/Hilbert%E2%80%93Samuel_function#...
Score of 3
1 answer
585 views
For a vector bundle over a curve, is there a condition on the Hilbert polynomial for no non-zero section?
Assume we are over $\mathbb C$. Let $C$ be a complete algebraic curve, and $E$ an algebraic vector bundle. Its Hilbert polynomial is
$$p(t)=rt+r(1-g)+d$$
where $r=\mathrm{rank}(E)$ and $d=\deg(E)$ and ...
Score of 3
0 answers
115 views
Growth of dimension of a good filtration on finitely generated modules over polynomial rings
Let $S=K[x_1,\cdots,x_s]$ be a polynomial ring over a characteristic zero field $K$.
For a partition $\{1, \cdots, s\} = I_1 \sqcup \cdots \sqcup I_r$ of the variable index, let $\mathbb{x}_i^{\mathbb{...
Score of 3
1 answer
243 views
On the degree of the Hilbert polynomial of a graded module over the Rees algebra
If $A=\oplus_{n=0}^\infty A_n$ is a Noetherian graded ring of finite dimension such that $A_0$ is local and $A=A_0[A_1]$, and if $M=\oplus_{n=0}^\infty M_n$ is a finitely generated graded $A$-module ...
Score of 4
0 answers
281 views
Computing the Hilbert series of an irreducible component of a complete intersection
There's a nice formula for the Hilbert series of any complete intersection of hypersurfaces $X_1\cap\cdots\cap X_i\subseteq\mathbb{P}^n$ in terms of the degrees of $X_1,\ldots,X_i$. Is there a way to ...