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Rouchdi Bahloul

Publications and source records attributed to Rouchdi Bahloul.

11 recordsLinked to original sources
arXiv2010

Parametric standard basis, degree bound and local Hilbert-Samuel function

We propose a general study of standard bases of polynomial ideals with parameters in the case where the monomial order is arbitrary. We give an application to the computation of the stratification by the local Hilbert-Samuel function. Moreover, we give an explicit upper bound for the degree of a standard basis for an arbitrary order and also for the number of the possible affine or local Hilbert-Samuel functions depending on the number of variables and the maximal degree of the given generators.

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arXiv2008

Algorithm for computing local Bernstein-Sato ideals

Given $p$ polynomials of $n$ variables over a field $k$ of characteristic 0 and a point $a \in k^n$, we propose an algorithm computing the local Bernstein-Sato ideal at $a$. Moreover with the same algorithm we compute a constructible stratification of $k^n$ such that the local Bernstein-Sato ideal is constant along each stratum. Finally, we present non-trivial examples computed with our algorithm.

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arXiv2006

Local Gröbner fan: polyhedral and computational approach

The goal of this paper is to show that the local Gröbner fan is a polyhedral fan for ideals in the ring of power series and the homogenized ring of analytic differential operators. We will also discuss about relations between the local Gröbner fan and the (global) Gröbner fan for a given ideal and algorithms of computing local Gröbner fans. In rings of differential operators, finiteness and convexity of local Gröbner fans were firstly proved by Assi, Castro-Jiménez and Granger. But they did not prove that they are polyhedral fans.

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arXiv2006

Grobner fan for analytic D-modules with parameters

This is the first part of a work dedicated to the study of Bernstein-Sato polynomials for several analytic functions depending on parameters. The main result of this part is a constructibility result for the analytic Gröbner fan of a parametric ideal in the ring of analytic differential operators. In this part, the main tool is the notion of generic reduced standard basis.

math.RA↗
arXiv2006

Some results on Bernstein-Sato polynomials for parametric analytic functions

This is the second part of a work dedicated to the study of Bernstein-Sato polynomials for several analytic functions depending on parameters. In this part, we give constructive results generalizing previous ones obtained by the author in the case of one function. We also make an extensive study of an example for which we give an expression of a generic (and under some conditions, a relative) Bernstein-Sato polynomial.

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arXiv2005

Polynome de Bernstein-Sato generique local

Given a family of analytic functions near 0 \in C^n parametrized by a smooth space, we study the Bernstein polynomial of the fiber on an irreducible variety V of the space of parameters and we show that it is generically constant. We prove that this polynomial b(s) satisfies a functional equation on V from which we derive a contructible stratification of the space of parameters by the Bernstein polynomial of the fiber. When the hypersurface admits generically a unique singularity at 0 \in C^n, we prove that b(s) is the generic Bernstein polynomial in the sense of Briançon-Geandier-Maisonobe. The tools for the proofs are a formal generalization of an algorithm by Oaku and the generic standard bases studied by the author.

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arXiv2005

Construction d'un element remarquable de l'ideal de Bernstein-Sato associe a deux courbes planes analytiques

Let $f_1$ and $f_2$ be two semi-universal deformations of quasi homogeneous polynomials in two variables respectively for the weight vectors $ρ_1$ and $ρ_2$ such that they satisfy similar conditions to that of semi quasi homogeneous singularities for one weight. By methods inspired by H. Maynadier's, we give an explicit formula for a Bernstein-Sato polynomial involving two affine forms $ρ_i(f_1) s_1 + ρ_i(f_2) s_2 +k$, $i=1,2$. In the particular case $(f_1, f_2)=(x_1^a+x_2^b, x_1^c+x_2^d)$, we calculate the space $\mathcal{H}_f$ recently studied by J. Briançon, Ph. Maisonobe and M. Merle and we show that it is equal to the zero set of $s_1 s_2 (ab s_1+ ad s_2)(ad s_1+ cd s_2)$.

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arXiv2004

Generic and comprehensive standard bases

Parametric Gröbner bases have been studied for more than 15 years and are now a further developed subject. Here we propose a general study of parametric standard bases, that is with local orders. We mainly focus on the commutative case but we also treat the case of differential operators rings. We will be concerned by two aspects: a theoretical aspect with existence theorems and a practical aspect devoted to how we can explicitely compute such objects when the given data are algebraic. We believe that parametric standard bases are important for both aspects. From a theoretical point of view, they constitute a strong tool for proving constructive results. From a practical one, they provide a tool for studying explicitely local objects associated with parametric algebraic ideals.

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arXiv2003

Generic Bernstein-Sato polynomial on an irreducible affine scheme

Given $p$ polynomials with coefficients in a commutative unitary integral ring $\mathcal{C}$ containing $\mathbb{Q}$, we define the notion of a generic Bernstein-Sato polynomial on an irreducible affine scheme $V \subset \text{Spec}(\mathcal{C})$. We prove the existence of such a non zero rational polynomial which covers and generalizes previous existing results by H. Biosca. When $\mathcal{C}$ is the ring of an algebraic or analytic space, we deduce a stratification of the space of the parameters such that on each stratum, there is a non zero rational polynomial which is a Bernstein-Sato polynomial for any point of the stratum. This generalizes a result of A. Leykin obtained in the case $p=1$.

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