A database of invariant rings.
Algorithmische P-Zerlegungen und Anwendungen
An algorithm for primary decomposition in polynomial rings over the integers
We present an algorithm to compute a primary decomposition of an ideal in a polynomial ring over the integers. For this purpose we use algorithms for primary decomposition in polynomial rings over the rationals, resp. over finite fields, and the idea of Shimoyama-Yokoyama, resp. Eisenbud-Hunecke-Vasconcelos, to extract primary ideals from pseudo-primary ideals. A parallelized version of the algorithm is implemented in Singular. Examples and timings are given at the end of the article.
An algorithm to compute the kernel of a derivation up to a certain degree
An algorithm is described which computes generators of the kernel of derivations on k[X₁,...,Xₙ] up to a previously given bound. For w-homogeneous derivations it is shown that if the algorithm computes a generating set for the kernel then this set is minimal.
An effective procedure for minimal bases of ideals in Z[x]
We give an effective procedure to find minimal bases for ideals of the ring of polynomials over the integers.
Flatness testing over singular bases
We show that non-flatness of a morphism φ:X→ Y of complex-analytic spaces with a locally irreducible target of dimension n manifests in the existence of vertical components in the n-fold fibred power of the pull-back of φ to the desingularization of Y. An algebraic analogue follows: Let R be a locally (analytically) irreducible finite type ℂ-algebra and an integral domain of Krull dimension n, and let S be a regular n-dimensional algebra of finite type over R (but not necessarily a finite R-module),...
Hilbert-Poincaré series of bigraded algebras
Lo scopo di questo lavoro è la descrizione di alcune nuove tecniche per calcolare serie di Hilbert-Poincaré (HP-serie) di algebre standard, che possono essere viste come sottoalgebre di algebre bigraduate. In particolare mostriamo come calcolare in modo uniforme le HP-serie delle potenze di un idele omogeneo. Mostriamo anche come calcolare le HP-serie di prodotti di Segre e di alcune algebre di Blow-up, che sono di interesse in Geometria Algebrica. Per alcune classi siamo in grado di descrivere...
Ideal arithmetic and infrastructure in purely cubic function fields
This paper investigates the arithmetic of fractional ideals of a purely cubic function field and the infrastructure of the principal ideal class when the field has unit rank one. First, we describe how irreducible polynomials decompose into prime ideals in the maximal order of the field. We go on to compute so-called canonical bases of ideals; such bases are very suitable for computation. We state algorithms for ideal multiplication and, in the case of unit rank one and characteristic at least five,...
On the computation of the minimal resolution of smooth parametric varieties.
On the Graver complexity of codimension 2 matrices.
On the height of the Sylvester resultant.
On the Jacobian ideal of the binary discriminant.
Let Δ denote the discriminant of the generic binary d-ic. We show that for d ≥ 3, the Jacobian ideal of Δ is perfect of height 2. Moreover we describe its SL2-equivariant minimal resolution and the associated differential equations satisfied by Δ. A similar result is proved for the resultant of two forms of orders d, e whenever d ≥ e-1. If Φn denotes the locus of binary forms with total root multiplicity ≥ d-n, then we show that the ideal of Φn is also perfect, and we construct a covariant which...