9 papers
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…