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Abstract The question of which partial Hermitian matrices (some entries specified, some free) may be completed to positive definite matrices is addressed. It is shown that if the diagonal entries are… (More)

- E. Marques De Sá
- 1979

Abstract We say that A (λ) is λ-imbeddable in B (λ) whenever B (λ) is equivalent to a λ-matrix having A (λ) as a submatrix. In this paper we solve the problem of finding a necessary and sufficient… (More)

In this paper we consider the problem of characterizing the invariant factors of three matrices A B, and C, such that AB — C Our matrices have entries over a principal ideal domain or over a local… (More)

Background: Human beings have an innate need to form close emotional bonds with significant others. Objective: The purpose of this research was to study the effect of domestic violence during… (More)

- E. Marques De Sá
- 1994

Abstract Let ψ be a unitarily invariant norm on the space of (real or complex) n × m matrices, and g the associated symmetric gauge function: thus ψ ( A ) g ( s ( A )), where s(A) is the decreasing… (More)

- E. Marques De Sá, Carolina Santos Veiga, +4 authors Sofia Viamonte Gonçalves
- 2005

Fibromyalgia constitutes a concept searching for consensus. This paper focuses on the definition of fibromyalgia as well as on the multiplicity of variables ...

- E. Marques De Sá
- 1994

Abstract Let ψ be a unitarily invariant norm on the space of all n × m complex matrices, and let g : R n → R be the symmetric gauge function associated with ψ. That is to say, we have ψ ( A ) g ( s… (More)

We study several bounds for the determinant of an n × n positive definite Hermitian matrix A. These bounds are the best possible given certain data about A. We find the best bounds in the cases that… (More)

Let A A be n×n matrices. We study the eigenvalues of when X runs over the set of n×n nonsingular matrices.

- Carlos M. da Fonseca, E. Marques De Sá
- Discrete Mathematics
- 2006

We determine the number of alternating parity sequences that are subsequences of an increasing m-tuple of integers. For this and other related counting problems we find formulas that are combinations… (More)