We show that finding a global optimal solution for the regularized Lq-minimization problem (q ≥ 1) is strongly NP-hard if the penalty function is concave but not linear in a neighborhood of zero and satisfies a very mild technical condition. This implies that it is impossible to have a fully polynomial-time approximation scheme (FPTAS) for such problems unless P = NP. This result clarifies the ...

Recently K. Murota has introduced concepts of L-convex function and Mconvex function as generalizations of those of submodular function and base polyhedron, respectively, and has shown separation theorems for L-convex/concave functions and for M-convex/concave functions. The present note gives short alternative proofs of the separation theorems by relating them to the ordinary separation theore...

In this paper,  fuzzy convergence theory in the framework of $L$-convex spaces is introduced. Firstly, the concept of $L$-convex remote-neighborhood spaces is introduced and it is shown that the  resulting category is isomorphic to that of $L$-convex spaces. Secondly, by means of $L$-convex ideals, the notion of $L$-convergence spaces is introduced and it is proved that the  category of $L$-con...

`-Graph, which learns a sparse graph over the data by sparse representation, has been demonstrated to be effective in clustering especially for high dimensional data. Although it achieves compelling performance, the sparse graph generated by `-Graph ignores the geometric information of the data by sparse representation for each datum separately. To obtain a sparse graph that is aligned to the u...

We consider the generalized Lorentz space L ;q dened via a continuous and concave function Fourier series of with respect to an unbounded orthonormal system. Some new Jackson-Nikol'skii type inequalities in this frame are stated, proved discussed. In particular, derived results generalize unify several well-known but also some applications pointed out.

Censored quantile regression models are very useful for the analysis of censored data when standard linear models are felt to be appropriate. However, fitting censored quantile regression is hard numerically due to the fact that the objective function that has to be minimized is not convex nor concave in regressors. The performance of standard methods is not satisfactory, in particular if a hig...

This paper is concerned with the existence of multiple positive‎ ‎solutions for a quasilinear elliptic system involving concave-convex‎ ‎nonlinearities‎ ‎and sign-changing weight functions‎. ‎With the help of the Nehari manifold and Palais-Smale condition‎, ‎we prove that the system has at least two nontrivial positive‎ ‎solutions‎, ‎when the pair of parameters $(lambda,mu)$ belongs to a c...

In this paper, we introduce a more general approach to the fuzzification of fuzzy concavity. More specifically, degree L , M -fuzzy concavity is introduced and characterized as generalization id="M2"> -concave structure id="M3"> conca...