Sagbi Bases in Rings of Multiplicative Invariants
نویسندگان
چکیده
Let k be a field and G be a finite subgroup of GLn(Z). We show that the ring of multiplicative invariants k[x±1 1 , . . . , x ±1 n ] G has a finite SAGBI basis if and only if G is generated by reflections.
منابع مشابه
New Algorithm For Computing Secondary Invariants of Invariant Rings of Monomial Groups
In this paper, a new algorithm for computing secondary invariants of invariant rings of monomial groups is presented. The main idea is to compute simultaneously a truncated SAGBI-G basis and the standard invariants of the ideal generated by the set of primary invariants. The advantage of the presented algorithm lies in the fact that it is well-suited to complexity analysis and very easy to i...
متن کاملSagbi Bases for Rings of Invariant Laurent Polynomials
Let k be a field, Ln = k[x ±1 1 , . . . , x ±1 n ] be the Laurent polynomial ring in n variables and G be a group of k-algebra automorphisms of Ln. We give a necessary and sufficient condition for the ring of invariants Ln to have a SAGBI basis. We show that if this condition is satisfied then Ln has a SAGBI basis relative to any choice of coordinates in Ln and any term order.
متن کاملOptimal Lower Bound for Generators of Invariant Rings without Finite SAGBI Bases with Respect to Any Admissible Order
)( was investigated. It turned out that only invariant rings of direct products of symmetric groups have a finite SAGBI basis, which is then, in addition, multilinear. Of course, it would be of interest to have such a strong characterization with respect to any other admissible order [4, 6]. To achieve this seems to be all but trivial. One step towards the understanding of the behavior of SAGBI...
متن کاملSagbi Bases of Cox-Nagata Rings
We degenerate Cox–Nagata rings to toric algebras by means of sagbi bases induced by configurations over the rational function field. For del Pezzo surfaces, this degeneration implies the Batyrev–Popov conjecture that these rings are presented by ideals of quadrics. For the blow-up of projective n-space at n + 3 points, sagbi bases of Cox–Nagata rings establish a link between the Verlinde formul...
متن کاملSymmetric Functions and the Phase Problem in Crystallography
The calculation of crystal structure from X-ray diffraction data requires that the phases of the “structure factors” (Fourier coefficients) determined by scattering be deduced from the absolute values of those structure factors. Motivated by a question of Herbert Hauptman, we consider the problem of determining phases by direct algebraic means in the case of crystal structures with n equal atom...
متن کامل