The geometry of the octet
Let Ω be an open subset of ℝⁿ. Let L² = L²(Ω,dx) and H¹₀ = H¹₀(Ω) be the standard Lebesgue and Sobolev spaces of complex-valued functions. The aim of this paper is to study the group of invertible operators on H¹₀ which preserve the L²-inner product. When Ω is bounded and ∂Ω is smooth, this group acts as the intertwiner of the H¹₀ solutions of the non-homogeneous Helmholtz equation u - Δu = f, . We show that is a real Banach-Lie group, whose Lie algebra is (i times) the space of symmetrizable operators....
Let denote generic binary forms, and let denote their -th transvectant in the sense of classical invariant theory. In this paper we classify all the quadratic syzygies between the . As a consequence, we show that each of the higher transvectants is redundant in the sense that it can be completely recovered from and . This result can be geometrically interpreted in terms of the incomplete Segre imbedding. The calculations rely upon the Cauchy exact sequence of -representations, and the...
Sia un grupo di Lie compatto e semplice. Sia la più piccola orbita nilpotente non-banale nell'algebra di Lie complessa . Si presenta una costruzione diretta di teoria di Lie delle metriche iperKahler su con potenziale Kahleriano -invariante e compatibili con la forma simplettica complessa di Kostant-Kirillov-Souriau. In particolare si ottengono le metriche iperKahler dei fibrati associati sugli spazi di Wolf (spazi simmetrici quaternionali a curvatura scalare positiva).