Superior properties of the PRESB preconditioner for operators on two-by-two block form with square blocks
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DOI: 10.1007/s00211-020-01143-x
Abstract: Matrices or operators in two-by-two block form with square blocks arise in numerous important applications, such as in optimal control problems for PDEs. The problems are normally of very large scale so iterative solution methods… read more here.
Keywords: block; operators two; two two; preconditioner ... See more keywords
Intertwining Operators between Two Orthogonal Projections
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DOI: 10.1080/01630563.2020.1813166
Abstract: Abstract Let P and Q be a pair of orthogonal projections. In this note we will prove that there exists a unitary such that UP = QU and UQ = PU if and only if read more here.
Keywords: intertwining operators; orthogonal projections; two orthogonal; operators two ... See more keywords
Inverse problems for differential operators with two delays larger than half the length of the interval and Dirichlet conditions
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DOI: 10.3906/mat-1903-112
Abstract: This paper deals with nonself-adjoint second-order differential operators with two constant delays from [ π 2 , π and two real-valued potentials from L2[0, π]. An inverse spectral problem of recovering operators from the spectra… read more here.
Keywords: operators two; delays larger; two delays; inverse problems ... See more keywords