9 citations · 11 across the 13 of their papers we have counts for
18 papers
Factorizations of linear relations by idempotents
M. Laura Arias, Maximiliano Contino, Stefania Marcantognini
We study the class of those linear relations that can be factorized as products of idempotent relations. We provide several characterizations of this class, extending known factori…
A note on a Halmos problem
Maximiliano Contino, Eva Gallardo-Gutierrez
We address the existence of non-trivial closed invariant subspaces of operators on Banach spaces whenever their square have or, more generally, whether there exists a pol…
Global solutions of approximation problems in Krein spaces
Maximiliano Contino
Three approximation problems in Krein spaces are studied, namely the indefinite weighted least squares problem and the related problems of indefinite abstract splines and smoothing…
Semiclosed multivalued projections
M. Laura Arias, Maximiliano Contino, Alejandra Maestripieri +1
A multivalued projection is an idempotent linear relation with invariant domain. We characterize multivalued projections that are operator ranges (called semiclosed) and provide se…
Matrix representations of multivalued projections and least squares problems
Maria Laura Arias, Maximiliano Contino, Alejandra Maestripieri +1
Multivalued projections are applied to the study of weighted least squares solutions of linear relations equations (or inclusions) and some of its applications. To this end a matri…
Idempotent linear relations
Maria Laura Arias, Maximiliano Contino, Alejandra Maestripieri +1
A linear relation acting on a Hilbert space is idempotent if A triplet of subspaces is needed to characterize a given idempotent: $(\mathrm{ran} \, E, \mathrm{ran}(I-E…
A matrix formula for Schur complements of nonnegative selfadjoint linear relations
Maximiliano Contino, Alejandra Maestripieri, Stefania Marcantognini
If a nonnegative selfadjoint linear relation in a Hilbert space and a closed subspace are assumed to satisfy that the domain of is invariant under the orthogo…
Polyak's theorem on Hilbert spaces
Maximiliano Contino, Guillermina Fongi, Santiago Muro
We extend to infinite dimensional Hilbert spaces a celebrated result, due to B. Polyak, about the convexity of the joint image of quadratic functions. We give sufficient conditions…
Total least squares problems on infinite dimensional spaces
Maximiliano Contino, Guillermina Fongi, Alejandra Maestripieri +1
In this work we study weighted total least squares problems on infinite dimensional spaces. We show that in most cases this problem does not admit a solution (except in the trivial…
Products of positive operators
Maximiliano Contino, Michael A. Dritschel, Alejandra Maestripieri +1
On finite dimensional spaces, it is apparent that an operator is the product of two positive operators if and only if it is similar to a positive operator. Here, the class ${\mathc…
Semiclosed projections and applications
Maximiliano Contino, Alejandra Maestripieri, Stefania Marcantognini
We characterize the semiclosed projections and apply them to compute the Schur complement of a selfadjoint operator with respect to a closed subspace. These projections occur natur…
Global solutions of approximation problems in Hilbert spaces
Maximiliano Contino, Maria Eugenia Di Iorio y Lucero, Guillermina Fongi
We study three well-known minimization problems in Hilbert spaces: the weighted least squares problem and the related problems of abstract splines and smoothing. In each case we an…
Weighted operator least squares problems and the J-trace in Krein spaces
Maximiliano Contino, Alejandra Maestripieri, Stefania Marcantognini
Given B, C and W operators in the algebra L(H) of bounded linear operators on the Krein space H, the minimization problem min (BX - C)^#W(BX - C), for X in L(H), is studied when th…
Schur complements of selfadjoint Krein space operators
Maximiliano Contino, Alejandra Maestripieri, Stefania Marcantognini
Given a bounded selfadjoint operator W on a Krein space H and a closed subspace S of H, the Schur complement of W to S is defined under the hypothesis of weak complementability. A…
Shorted operators and minus order
Maximiliano Contino, Juan Ignacio Giribet, Alejandra Maestripieri
Let be a Hilbert space, the algebra of bounded linear operators on and a positive operator. Given a closed subsp…
Operator least squares problems and Moore-Penrose inverses in Krein spaces
Maximiliano Contino, Alejandra Maestripieri, Stefania Marcantognini
A Krein space H and bounded linear operators B, C on H are given. Then, some min and max problems about the operators (BX - C)^{#}(BX -C), where X runs over the space of all bounde…
Weighted least square solutions of the equation AXB-C=0
Maximiliano Contino, Juan Giribet, Alejandra Maestripieri
Let be a Hilbert space, the algebra of bounded linear operators on and a positive operator such that i…
Weighted Procrustes problems
Maximiliano Contino, Juan Giribet, Alejandra Maestripieri
Let be a Hilbert space, the algebra of bounded linear operators on and a positive operator such that i…