Approximation algorithms for NP-hard optimization problems have been widely studied for over three decades. Most of these measure the quality of the solution produced by taking the ratio of the cost of the solution produced by the algorithm to the cost of an optimal solution. In certain cases, this ratio may not be very meaningful { for example , if the ratio of the worst solution to the best s...

in this article we introduce the concept of $z^circ$-filter on a topological space $x$. we study and investigate the behavior of $z^circ$-filters and compare them  with corresponding ideals, namely, $z^circ$-ideals of $c(x)$,  the ring of real-valued continuous functions on a completely regular hausdorff space $x$. it is observed that $x$ is a compact space if and only if every $z^circ$-filter ...

We present a new and homogeneous set of explosive yields for masses 13, 15, 20, 25, 30 and 35 M⊙ and metallicities Z = 0, 10 , 10, 10, 6 · 10, 2 · 10. A wide network extending up to Mo has been used in all the computation. We show that at low metallicities (Z ≤ 10) the final yields do not depend significantly on the initial chemical composition of the models so that a scaled solar distribution ...

Coset conformal field theories with abelian isotropy groups. Abstract Conformal field theories based on g/u(1) d coset constructions where g is a reductive algebra are studied.It is shown that the theories are equivalent to constrained WZNW models for g. Generators of extended symmetry algebras and primary fields are constructed. In a recent paper [1] currents, primary fields and generators of ...