Generalized MICZ-Kepler Problems and Unitary Highest Weight Modules

For each integer $n\ge 1$, we demonstrate that a $(2n+1)$-dimensional generalized MICZ-Kepler problem has an \mr{Spin}(2, 2n+2) dynamical symmetry which extends the manifest \mr{Spin}(2n+1) symmetry. The Hilbert space of bound states is shown to form a unitary highest weight \mr{Spin}(2, 2n+2)-module which occurs at the first reduction point in the Enright-Howe-Wallach classification diagram for the unitary highest weight modules. As a byproduct, we get a simple geometric realization for such a unitary highest weight \mr{Spin}(2, 2n+2)-module.Comment: 27 pages, Refs. update

Can fusion coefficients be calculated from the depth rule ?

The depth rule is a level truncation of tensor product coefficients expected to be sufficient for the evaluation of fusion coefficients. We reformulate the depth rule in a precise way, and show how, in principle, it can be used to calculate fusion coefficients. However, we argue that the computation of the depth itself, in terms of which the constraints on tensor product coefficients is formulated, is problematic. Indeed, the elements of the basis of states convenient for calculating tensor product coefficients do not have a well-defined depth! We proceed by showing how one can calculate the depth in an `approximate' way and derive accurate lower bounds for the minimum level at which a coupling appears. It turns out that this method yields exact results for $\widehat{su}(3)$ and constitutes an efficient and simple algorithm for computing $\widehat{su}(3)$ fusion coefficients.Comment: 27 page

Compact Lie groups and their representations

The content of this book is somewhat different from that of traditional books on representation theory. First, bearing in mind the needs of physicists, the author has tried to make the exposition as elementary as possible. The need for an elementary exposition has influenced the distribution of the material. The book is divided into three largely independent parts, arranged in order of increasing difficulty. Besides compact Lie groups, groups with other topological structure ("similar" to compact groups in some sense) are considered. Prominent among these are reductive complex Lie groups (including semisimple groups), obtained from compact Lie groups by analytic continuation, and also their real forms (reductive real Lie groups). The theory of finite-dimensional representation for these classes of groups is developed, striving whenever possible to emphasize the "compact origin" of these representations, i.e., their analytic relationship to representations of compact Lie groups. In conclusion, the author briefly presents some aspects of infinite-dimensional representations of semisimple complex Lie algebras and Lie groups