We formulate matrix models for strings in ten dimensional pp-wave backgrounds and for particles in eleven dimensional ones. This is done by first characterizing the deformations of ten dimensional N=1 SYM which are induced by a constant bispinorial coupling ∫ Ψ̄HΨ plus a minimal purely bosonic completition and then by the appropriate dimensional reduction. We find a whole class of new models for...

We formulate matrix string models on a class of exact string backgrounds with non constant RR-flux parameterized by a holomorphic prepotential function and with manifest (2,2) supersymmetry. This lifts these string theories to M-theory exposing the non perturbative string interaction which is studied by generalizing the instanton asymptotic expansion, well established in the flat background cas...

A new fast algorithm for computing the zeros of a polynomial in O(n2) time using O(n) memory is developed. The eigenvalues of the Frobenius companion matrix are computed by applying a nonunitary analogue of Francis’s implicitly shifted QR algorithm to a factored form of the matrix. The algorithm achieves high speed and low memory use by preserving the factored form. It also provides a residual ...

In 1990, J.L. Krivine introduced the notion of storage operator to simulate, in λ-calculus, the ”call by value” in a context of a ”call by name”. J.L. Krivine has shown that, using Gődel translation from classical into intuitionistic logic, we can find a simple type for storage operators in AF2 type system. In this present paper, we give a general type for storage operators in a slight extensio...

A polynomial matrix G(z) = Izm −∑m−1 i=0 Ciz with complex coefficients is called discrete-time stable if its characteristic values (i.e. the zeros of detG(z) ) are in the unit disc. A corresponding block companion matrix C is used to study discrete-time stability of G(z) . The main tool is the construction of block diagonal solutions P of a discrete-time Lyapunov inequality P−C∗PC 0 .

In human relations engagement and continuous communication is promoted by the process of sharing experiences. This type of social behaviour plays an important role in the maintenance of relationships with our peers and it is grounded by cognitive features of memory. Aiming at creating agents that sustain long-term interactions, we developed MAY, a conversational virtual companion that gathers m...

This paper presents a qualitative study conducted to explore perceptions, attitudes and expectations for a virtual assistive companion designed to supplement human caregiving and facilitate an improved quality of life and long-term health benefits for older adults. The study was conducted adopting a human-centred approach; employing focus groups and individual interviews with older adults, prof...

In 1990, J.L. Krivine introduced the notion of storage operator to simulate ”call by value” in the ”call by name” strategy. J.L. Krivine has shown that, using Gődel translation of classical into intuitionitic logic, we can find a simple type for the storage operators in AF2 type system. This paper studies the ∀-positive types (the universal second order quantifier appears positively in these ty...

In this paper an implicit (double) shifted QR-method for computing the eigenvalues of companion and fellow matrices will be presented. Companion and fellow matrices are Hessenberg matrices, that can be decomposed into the sum of a unitary and a rank 1 matrix. The Hessenberg, the unitary as well as the rank 1 structures are preserved under a step of the QR-method. This makes these matrices suita...

The classical approach to investigating polynomial eigenvalue problems is linearization, where the polynomial is converted into a larger matrix pencil with the same eigenvalues. For any polynomial there are infinitely many linearizations with widely varying properties, but in practice the companion forms are typically used. However, these companion forms are not always entirely satisfactory, an...