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The group of L²-isometries on H¹₀

Esteban Andruchow, Eduardo Chiumiento, Gabriel Larotonda (2013)

Studia Mathematica

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, u | Ω = 0 . We show that is a real Banach-Lie group, whose Lie algebra is (i times) the space of symmetrizable operators....

The higher transvectants are redundant

Abdelmalek Abdesselam, Jaydeep Chipalkatti (2009)

Annales de l’institut Fourier

Let A , B denote generic binary forms, and let 𝔲 r = ( A , B ) r denote their r -th transvectant in the sense of classical invariant theory. In this paper we classify all the quadratic syzygies between the { 𝔲 r } . As a consequence, we show that each of the higher transvectants { 𝔲 r : r 2 } is redundant in the sense that it can be completely recovered from 𝔲 0 and 𝔲 1 . This result can be geometrically interpreted in terms of the incomplete Segre imbedding. The calculations rely upon the Cauchy exact sequence of S L 2 -representations, and the...

The hyperKähler geometry associated to Wolf spaces

Piotr Kobak, Andrew Swann (2001)

Bollettino dell'Unione Matematica Italiana

Sia G un grupo di Lie compatto e semplice. Sia O min la più piccola orbita nilpotente non-banale nell'algebra di Lie complessa g C . Si presenta una costruzione diretta di teoria di Lie delle metriche iperKahler su O min con potenziale Kahleriano G -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).

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