arXiv subjects

Emanoil Theodorescu

Publications and source records attributed to Emanoil Theodorescu.

3 recordsLinked to original sources

arXiv2004

Derived Functors and Hilbert Polynomials

Let $R$ be a commutative Noetherian ring, $I$ an ideal, $M$ and $N$ finitely generated $R$-modules. Assume $V(I)\cap Supp(M)\cap Supp(N)$ consists of finitely many maximal ideals and let $ł(\e^i(N/I^nN,M))$ denote the length of $\e^i(N/I^nN,M)$. It is shown that $ł(\e^i(N/I^nN,M))$ agrees with a polynomial in $n$ for $n>>0$, and an upper bound for its degree is given. On the other hand, a simple example shows that some special assumption such as the support condition above is necessary in order to conclude that polynomial growth holds.

math.AC↗

arXiv2004

Bivariate Hilbert Functions for the Torsion Functor

Let $(R,P)$ be a commutative, local Noetherian ring, $I$, $J$ ideals, $M$ and $N$ finitely generated $R$-modules. Suppose $J + ann_R M + ann_R N$ is $P$-primary. The main result of this paper is Theorem 6, which gives necessary and sufficient conditions for the length of $\t_i(M/I^nM,N/J^mN)$, to agree with a polynomial, for $m$, $n \gg 0$. As a corollary, it is shown that the length of $\t_i(M/I^nM,N/I^nN))$ always agrees with a polynomial in $n$, for $n \gg 0$, provided $I + ann_R M + ann_R N$ is $P$-primary.

math.AC↗

arXiv2004

Asymptotic behaviour of the length of local cohomology

Let k be a field of characteristic 0, R = k[x_1, ..., x_d] be a polynomial ring, and m its maximal homogeneous ideal. Let I be a homogeneous ideal in R. In this paper we investigate asymptotic behaviour of the quotient between the length of local cohomology group H^0_m(R/I^n) and n^d. We show that this quantity always has a limit as n goes to infinity. We also give an example for which the limit is irrational; in particular, this proves that the length of H^0_m(R/I^n) is not asymptotically a polynomial in n.

math.AC↗