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A simple integral formula as an iterated residue is presented for the Baker-Akhiezer function related to $A_n$ type root system both in the rational and trigonometric cases. We present also a formula for the Baker-Akhiezer function as a Selberg-type integral and generalise it to the deformed $A_{n,1}$-case. These formulas can be interpreted as new cases of explicit evaluation of Selberg-type integrals., 13 pages, 2 figures

Gaudin hamiltonians form families of r-dimensional abelian Lie subalgebras of the holonomy Lie algebra of the arrangement of reflection hyperplanes of a Coxeter group of rank r. We consider the set of principal Gaudin subalgebras, which is the closure in the appropriate Grassmannian of the set of spans of Gaudin hamiltonians. We show that principal Gaudin subalgebras form a smooth projective variety isomorphic to the De Concini-Procesi compactification of the projectivized complement of the arrangement of reflection hyperplanes., Comment: 13 pages, 2 figures; added detailed description of the B_2 and B_3 cases in the new version

We show that the orthogonal separation coordinates on the sphere $S^n$ are naturally parametrised by the real version of the Deligne-Mumford-Knudsen moduli space $\bar M_{0,n+2}(R)$ of stable curves of genus zero with $n+2$ marked points. We use the combinatorics of Stasheff polytopes tessellating $\bar M_{0,n+2}(R)$ to classify the different canonical forms of separation coordinates and deduce an explicit construction of separation coordinates and St\"ackel systems from the mosaic operad structure on $\bar M_{0,n+2}(R)$., Comment: Extended version, 20 pages, 4 figures

We introduce some discrete analogues of the Dirac magnetic monopole on a unit sphere S^2 and explain how to compute the corresponding spectrum using the representation theory of finite groups. The main examples are certain magnetic Laplacians on the regular polyhedral graphs, coming from induced representations of the binary polyhedral groups., Comment: 18 pages, 6 figures

We give a simple derivation of the spectrum of the Dirac magnetic monopole on a unit sphere based on geometric quantization and the Frobenius reciprocity formula. We also briefly discuss the generalisations of Dirac magnetic monopole to any coadjoint orbit of a compact Lie group., 8 pages, extended version with brief discussion of generilisations to coadjoint orbits of compact Lie groups