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## An application of global Weyl modules of sl(n+1)[t] to invariant theory

We identify the *sl(n*+1) isotypical components of the global Weyl modules *W*(*k**ω*1) with certain natural subspaces of the polynomial ring in *k* variables. We then apply the representation theory of current algebras to classical problems in invariant theory.

We study the category of graded representations with finite--dimensional graded pieces for the current algebra associated to a simple Lie algebra. This category has many similarities with the category O of modules for g and in this paper, we use the combinatorics of Macdonald polynomials to prove an analogue of the famous BGG duality in the case of sl(n+1)

This proceedings publication is a compilation of selected contributions from the “Third International Conference on the Dynamics of Information Systems” which took place at the University of Florida, Gainesville, February 16–18, 2011. The purpose of this conference was to bring together scientists and engineers from industry, government, and academia in order to exchange new discoveries and results in a broad range of topics relevant to the theory and practice of dynamics of information systems. Dynamics of Information Systems: Mathematical Foundation presents state-of-the art research and is intended for graduate students and researchers interested in some of the most recent discoveries in information theory and dynamical systems. Scientists in other disciplines may also benefit from the applications of new developments to their own area of study.

It is more than 10 years ago that the first edition of this book has appeared. Since then, the field of computational invariant theory has been enjoying a lot of attention and activity, resulting in some important and, to us, exciting developments. This is why we think that it is time for a second enlarged and revised edition. Apart from correcting some mistakes and reorganizing the presentation here and there, we have added the following material: further results about separating invariants and their computation (Sects. 2.4 and 4.9.1), Symonds’ degree bound (Sect. 3.3.2), Hughes’ and Kemper’s extension of Molien’s formula (Sect. 3.4.2), King’s algorithm for computing fundamental invariants (Sect. 3.8.2), Broer’s criterion for the quasi- Gorenstein property (Sect. 3.9.11), Dufresne’s generalization of Serre’s result on polynomial invariant rings and her result with Jeffries (Sect. 3.12.2), Kamke’s algorithm for computing invariants of finite groups acting on algebras (Sect. 3.13), Kemper’s and Derksen’s algorithm for computing invariants of reductive groups in positive characteristic (Sect. 3.13), algorithms by Müller-Quade and Beth, Hubert and Kogan, and Kamke and Kemper for computing invariant fields and localizations of invariant rings (Sect. 4.10.1), and work by van den Essen, Freudenburg, Greuel and Pfister, Kemper, Sancho de Salas, and Tanimoto on invariants of the additive group and of connected solvable groups (Sect. 4.10.5).

Last but not least, this edition contains two new appendices, written by Vladimir Popov, on algorithms for deciding the containment of orbit closures and on a stratification of Hilbert’s nullcone. The second appendix has an addendum, authored by Norbert A’Campo and Vladimir Popov, containing the source code of a program for computing this stratification. We would like to thank Bram Broer, Emilie Dufresne, Vladimir Popov, Jim Shank, and Peter Symonds for valuable comments on a pre-circulated version of this edition, Vladimir Popov and Norbert A’Campo for their contributions to the book, and Ruth Allewelt at Springer-Verlag for managing the production process and for gently pushing us to finally finish our work and hand over the files. Ann Arbor,MI, USA Harm Derksen Munich, Germany Gregor Kemper July 2015

We construct a filtration on an integrable highest weight module of an affine Lie algebra whose adjoint graded quotient is a direct sum of global Weyl modules. We show that the graded multiplicity of each global Weyl module there is given by the corresponding level-restricted Kostka polynomial. This leads to an interpretation of level-restricted Kostka polynomials as the graded dimension of the space of conformal coinvariants. In addition, as an application of the level one case of the main result, we realize global Weyl modules of current algebras of type ADEADE in terms of Schubert subvarieties of thick affine Grassmanian, as predicted by Boris Feigin.

A model for organizing cargo transportation between two node stations connected by a railway line which contains a certain number of intermediate stations is considered. The movement of cargo is in one direction. Such a situation may occur, for example, if one of the node stations is located in a region which produce raw material for manufacturing industry located in another region, and there is another node station. The organization of freight traﬃc is performed by means of a number of technologies. These technologies determine the rules for taking on cargo at the initial node station, the rules of interaction between neighboring stations, as well as the rule of distribution of cargo to the ﬁnal node stations. The process of cargo transportation is followed by the set rule of control. For such a model, one must determine possible modes of cargo transportation and describe their properties. This model is described by a ﬁnite-dimensional system of diﬀerential equations with nonlocal linear restrictions. The class of the solution satisfying nonlocal linear restrictions is extremely narrow. It results in the need for the “correct” extension of solutions of a system of diﬀerential equations to a class of quasi-solutions having the distinctive feature of gaps in a countable number of points. It was possible numerically using the Runge–Kutta method of the fourth order to build these quasi-solutions and determine their rate of growth. Let us note that in the technical plan the main complexity consisted in obtaining quasi-solutions satisfying the nonlocal linear restrictions. Furthermore, we investigated the dependence of quasi-solutions and, in particular, sizes of gaps (jumps) of solutions on a number of parameters of the model characterizing a rule of control, technologies for transportation of cargo and intensity of giving of cargo on a node station.

A form for an unbiased estimate of the coefficient of determination of a linear regression model is obtained. It is calculated by using a sample from a multivariate normal distribution. This estimate is proposed as an alternative criterion for a choice of regression factors.