CUBO, A Mathematical Journal <p align="justify">CUBO, A Mathematical Journal is a scientific journal founded in 1985, published by the Universidad de La Frontera, Temuco - Chile.&nbsp;The journal publishes original papers containing substantial results in areas of pure and applied mathematics.&nbsp;CUBO appears in three issues per year and is indexed in ZentralBlatt Math., Mathematical Reviews, MathSciNet and Latindex.</p> Universidad de La Frontera. Temuco, Chile. en-US CUBO, A Mathematical Journal 0716-7776 Approximation by Shift Invariant Univariate Sublinear-Shilkret Operators <p align="justify">A very general positive sublinear Shilkret integral type operator is given through a convolution-like iteration of another general positive sublinear operator with a scaling type function.For it sufficient conditions are given for shift invariance, preservation of global smoothness, convergence to the unit with rates. Additionally, two examples of very general specialized operators are presented fulfilling all the above properties, the higher order of approximation of these operators is also considered.</p> George A. Anastassiou ##submission.copyrightStatement## 2018-10-19 2018-10-19 20 1 01 16 10.4067/S0719-06462018000100001 W2-Curvature Tensor on Generalized Sasakian Space Forms <p>In this paper, we study W<sub>2</sub>-pseudosymmetric, W<sub>2</sub>-locally symmetric, W<sub>2</sub>-locally φ- symmetric and W<sub>2</sub>-φ-recurrent generalized Sasakian space form. Further, illustrative examples are given.</p> Venkatesha . Shanmukha B. ##submission.copyrightStatement## 2018-10-19 2018-10-19 20 1 17–29 17–29 10.4067/S0719-06462018000100017 Pre-regular sp-Open Sets in Topological Spaces <p>In this paper, a new class of generalized open sets in a topological space, called pre- regular sp-open sets, is introduced and studied. This class is contained in the class of semi-preclopen sets and cotains all pre-clopen sets. We obtain decompositions of regular open sets by using pre-regular sp-open sets.</p> P. Jeyanthi P. Nalayini T. Noiri ##submission.copyrightStatement## 2018-10-19 2018-10-19 20 1 31–39 31–39 10.4067/S0719-06462018000100031 Common Fixed Point Results in C∗-Algebra Valued b-Metric Spaces Via Digraphs <p>We discuss the existence and uniqueness of points of coincidence and common fixed points for a pair of self-mappings defined on a C<sup>∗</sup>-algebra valued b-metric space endowed with a graph. Our results extend and supplement several recent results in the literature. Strength of hypotheses made in the first result have been weighted through illustrative examples.</p> Sushanta Kumar Mohanta ##submission.copyrightStatement## 2018-10-19 2018-10-19 20 1 41–64 41–64 10.4067/S0719-06462018000100041 On rigid Hermitean lattices, II <p>We study the indexed Hermitean lattice of type 0 generated by a single element a subjected to the relation <em>a</em> ≤ <em>b</em><sup>⊥</sup> ∧ <em>bb</em><sup>⊥</sup>= 0. We prove that it is finite, provided that two crucial indices are finite. We show that index relations imply algebraic relations and describe the lattice by means of its subdirectly irreducible factors. We finally use the results to confirm a conjecture appeared in 2000.</p> Ana Cecilia de la Maza Remo Moresi ##submission.copyrightStatement## 2018-10-19 2018-10-19 20 1 65–78 65–78 10.4067/S0719-06462018000100065 Anti-invariant ξ⊥-Riemannian Submersions From Hyperbolic β-Kenmotsu Manifolds <p>In this paper, we introduce anti-invariant ξ⊥-Riemannian submersions from Hyperbolic β-Kenmotsu Manifolds onto Riemannian manifolds. Necessary and sufficient conditions for a special anti-invariant ξ⊥-Riemannian submersion to be totally geodesic are studied. Moreover, we obtain decomposition theorems for the total manifold of such submersions.</p> Mohd Danish Siddiqi Mehmet Akif Akyol ##submission.copyrightStatement## 2018-10-19 2018-10-19 20 1 79–94 79–94 10.4067/S0719-06462018000100079