Encontrados 6 documentos, a visualizar página 1 de 1
Totally nonpositive completions on partial matrices
Araújo, C. Mendes; Torregrosa, Juan R.; Urbano, Ana M.An n £ n real matrix is said to be totally no positive if every minor is no positive. In this paper, we are interested in totally no positive completion problems, that is, does A partial totally no positive matrix have a totally no positive matrix completion? This Problem has, in general, a negative answer. Therefore, we analyze the question: for which Labelled graphs G does every partial totally no positive ma...
The symmetric N-matrix completion problem
Araújo, C. Mendes; Torregrosa, Juan R.; Urbano, Ana M.An $n\times n$ matrix is called an $N$-matrix if all its principal minors are negative. In this paper, we are interested in the symmetric $N$-matrix completion problem, that is, when a partial symmetric $N$-matrix has a symmetric $N$-matrix completion. Here, we prove that a partial symmetric $N$-matrix has a symmetric $N$-matrix completion if the graph of its specified entries is chordal. Furthermore, if this g...
The doubly negative matrix completion problem
Araújo, C. Mendes; Torregrosa, Juan R.; Urbano, Ana M.An $n\times n$ matrix over the field of real numbers is a doubly negative matrix if it is symmetric, negative definite and entry-wise negative. In this paper, we are interested in the doubly negative matrix completion problem, that is when does a partial matrix have a doubly negative matrix completion. In general, we cannot guarantee the existence of such a completion. In this paper, we prove that every partial...
The N-matrix completion problem under digraphs assumptions
Araújo, C. Mendes; Torregrosa, Juan R.; Urbano, Ana M.An $n \times n$ matrix is called an $N$--matrix if all principal minors are negative. In this paper, we are interested in the partial $N$--matrix completion problem, when the partial $N$--matrix is non-combinatorially symmetric. In general, this type of partial matrices does not have an $N$--matrix completion. We prove that a non-combinatorially symmetric partial $N$--matrix has an $N$--matrix completion if the...
N-matrix completion problem
Araújo, C. Mendes; Torregrosa, Juan R.; Urbano, Ana M.An n x n matrix is called an N-matrix if all principal minors are negative. In this paper, we are interested in N-matrix completion problems, that is, when a partial N-matrix hás an N-matrix completion. In general, a combinatorially or non-combinatorially symmetric partial N-matrix does not have an N-matrix completion. Here we prove that a combinatorially symmetric partial N-matrix has an N-matrix completion if...
Multinuclear magnetic resonance study of the structure and dynamics of lanthani...
Geraldes, Carlos F. G. C.; Urbano, Ana M.; Hoefnagel, Mattheus A.; Peters, Joop A.The structure and dynamics of the lanthanide(II1) complexes of the bis(propy1amide) of diethylenetriaminepentaacetate (DTPA-PA3 in aqueous solution have been investigated by I3C and I7O NMR. With the use of the longitudinal 13C relaxation times of the NdlI1 complex it is shown that the organic ligand is bound to the lanthanide(II1) ion in an octadentate fashion via the three nitrogens of the diethylenetriamine ...
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