Optimal normal projections in Krein spaces

JUAN IGNACIO GIRIBET; ALEJANDRA MAESTRIPIERI; FRANCISCO MARTÍNEZ PERÍA

LINEAR ALGEBRA AND ITS APPLICATIONS

ELSEVIER SCIENCE INC

Lugar: Amsterdam; Año: 2016 vol. 490 p. 77 - 101

0024-3795

Given a pseudo-regular subspace $St$ of a Krein space $HH$ with fundamental symmetry $J$, if its isotropic part $St^circ$ is not trivial the set $Q_St$ of $J$-normal projections onto $St$ has infinitely many elements. The aim of this work is to distinguish a projection $Q_0in Q_St$ according to a suitable criterion. When $HH$ is finite-dimensional, $Q_0$ turns out to be the unique minimal norm projection in $Q_St$ respect to the Schatten $p$-norm for $1leq p