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131.
Fabian Reimers 《代数通讯》2020,48(4):1584-1590
132.
133.
The perturbation of symmetries of the free Birkhoff system under small excitation is discussed. The concept of high-order
adiabatic invariant is presented, and the form of adiabatic invariants and the conditions for their existence are given. Then
these results are generalized to the constrained Birkhoff system. One example is presented to illustrate these results.
The project supported by the National Natural Science Foundation (19972010) and the Doctoral Program Foundation of Institution
of Higher Education of China and the Natural Science Foundation of Henan Province 相似文献
134.
Grzegorz Malara 《Mathematische Nachrichten》2023,296(4):1589-1615
Generic initial ideals (gins for short) were systematically introduced by Galligo in 1974 under the name of Grauert invariants since they appeared apparently first in works of Grauert and Hironaka. Ever since they have been of interest in commutative algebra and indirectly in algebraic geometry. Recently, Mayes in a series of articles associated with gins of graded families of ideals geometric objects called limiting shapes. The construction resembles that of Okunkov bodies but there are some differences as well. This work is motivated by Mayes articles and explores the connections between gins, limiting shapes, and some asymptotic invariants of homogeneous ideals which are associated with the gins, for example, asymptotic regularity, Waldschmidt constant and some new invariants, which seem relevant from geometric point of view. 相似文献
135.
While the Lorentzian and Riemannian metrics for which all polynomial scalar curvature invariants vanish (the VSI property) are well-studied, less is known about the four-dimensional neutral signature metrics with the VSI property. Recently it was shown that the neutral signature metrics belong to two distinct subclasses: the Walker and Kundt metrics. In this paper we have chosen an example from each of the two subcases of the Ricci-flat VSI Walker metrics respectively.To investigate the difference between the metrics we determine the existence of a null, geodesic, expansion-free, shear-free and vorticity-free vector, and classify these spaces using their holonomy algebras. The geometric implications of these algebras are further studied by identifying the recurrent or covariantly constant null vectors, whose existence is required by the holonomy structure in each example. We conclude the paper with a simple example of the equivalence algorithm for these pseudo-Riemannian manifolds, which is the only approach to classification that provides all necessary information to determine equivalence. 相似文献
136.
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138.
Benito Hernández-Bermejo 《Physics letters. A》2010,374(6):836-1975
The problem of characterizing all new-time transformations preserving the Poisson structure of a finite-dimensional Poisson system is completely solved in a constructive way. As a corollary, this leads to a broad generalization of previously known results. Examples are given. 相似文献
139.
We consider linear hyperbolic equations of the form
140.
A problem that arose in the study of the mass of the neutrino led us to the evaluation of a constant term with a variety of ramifications into several areas from Invariant Theory, Representation Theory, the Theory of Symmetric Functions and Combinatorics. A significant by-product of our evaluation is the construction of a trigraded Cohen Macaulay basis for the Invariants under an action of SLn(C) on a space of 2n+n2 variables. 相似文献