If T is a piecewise linear fixed-point free involution on S, the orbit space Q = S/T is a PL-manifold homotopy equivalent to P»(JR) ~ P n [2J; the affirmative solution to the Poincaré conjecture implies that conversely for n&Z, 4 the double covering manifold of any such Q can be identified with S. Write In for the set of (oriented if n is even) PL-homeomorphism classes of manifolds Q homotopy e...

We study linear free divisors, that is, free divisors arising as discriminants in prehomogeneous vector spaces, and in particular in quiver representation spaces. We give a characterization of the prehomogeneous vector spaces containing such linear free divisors. For reductive linear free divisors, we prove that the numbers of geometric and representation theoretic irreducible components coinci...

In this paper, a new collocation method, which is based on Boubaker polynomials, is introduced for the approximate solutions of a class of two-dimensional linear Fredholm integral equationsof the second kind. The properties of two-dimensional Boubaker functions are presented. The fundamental matrices of integration with the collocation points are utilized to reduce the solution of the integral ...

Hierarchical phrase-based translation (Hiero) is a statistical machine translation (SMT) model that encodes translation as a synchronous context-free grammar derivation between source and target language strings (Chiang, 2005; Chiang, 2007). Hiero models are more powerful than phrase-based models in capturing complex source-target reordering as well as discontiguous phrases, while being easier ...

It is a long standing open problem to find an explicit description of the stable set polytope of clawfree graphs. Yet more than 20 years after the discovery of a polynomial algorithm for the maximum stable set problem for claw-free graphs, there is even no conjecture at hand today. Such a conjecture exists for the class of quasi-line graphs. This class of graphs is a proper superclass of line g...

Within the linear theory of the electromagnetism for the ionosphere we give a general closed expression for the minimum free energy in terms of Fourier-transformed quantities, when the integrated history of the electric field is chosen to characterize the state of the material. Another equivalent expression is derived and also used to study the particular case of a discrete spectrum model.

The free energy of a single-stranded RNA can be calculated by adding the free energies of the components: basepairs, bulges, and loops. Basepairs receive negative free energy while the unpaired bases receive positive free energy. The minimum free energy of a random RNA secondary structure with one domain has value Fn where the sequence length is n. Under simplifying assumptions, we show that fo...

We study context-free grammars whose generated language is bounded (that is, subset of some expression w ̊ 1 . . . w ̊ d called bounded expression). We investigate the underlying generating process of such language and show that there exists a bounded expression u1 . . . um over the production rules, such that the language is generated only by sequences of production rules conforming to the bound...

We investigate the global GRAMMAR constraint over restricted classes of context free grammars like deterministic and unambiguous context-free grammars. We show that detecting disentailment for the GRAMMAR constraint in these cases is as hard as parsing an unrestricted context free grammar. We also consider the class of linear grammars and give a propagator that runs in quadratic time. Finally, ...