2 citations · 2 across the 8 of their papers we have counts for
12 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…
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…
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…
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…
Krein space unitary dilations of Hilbert space holomorphic semigroups
Stefania Marcantognini
The infinitesimal generator of a strongly continuous semigroup on a Hilbert space is assumed to satisfy that is a sectorial operator of angle less than f…
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…
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…
Interpolation in Semigroupoid Algebras
Michael A. Dritschel, Stefania Marcantognini, Scott McCullough
A seminal result of Agler characterizes the so-called Schur-Agler class of functions on the polydisk in terms of a unitary colligation transfer function representation. We generali…