Representations and Nilpotent Orbits of Lie Algebraic Systems: In Honour of the 75th Birthday of Ton

Preface.- Singular Support of a Vertex Algebra and the Arc Space of its Associated Scheme.- On Cacti and Crystals.- Quotients for Sheets of Conjugacy Classes.- About Polynomiality of the Poisson Semicentre for Parabolic Subalgebras.- On Dynkin Gradings in Simple Lie Algebras.- Multiplicative Slices, Relativistic Toda, and Shifted Quantum Affine Algebras.- Some Properties of Orbital Varieties in Extremal Nilpotent Orbits.- On Involutions in the Weyl Group and B-Orbit Closures in the Orthogonal Case.- Proper Self-Similar Triangle Tiling and Representing Weight Diagrams in the Plane.- Closures of On-Orbits in the Flag Variety for GLn.- On the Spin Calogero-Sutherland Model at Infinity.- Semi-Direct Products Involving Sp2n or Spinn with Free Algebras of Symmetric Invariants.- Primitive Ideals of U(sl( )) and The Robinson-Schensted Algorithm at Infinity.- Prime Spectra of Abelian 2-Categories and Categorifications of Richardson Varieties.