In this paper we introduce a class of right S-acts called retractable S-acts which are right S-acts with homomorphisms into their all subacts. We also give some
First,we give a module estimation of the singular integral with a differential element.Then by proving the existences of Cauchy principal value we obtain the tr
An acyclic edge coloring of a graph G is a proper edge coloring such that there are no bichromatic cycles.The acyclic edge chromatic number of a graph G is the
Let M be a 3-manifold, F= {F1 , F2 , . . . , Fn } be a collection of essential closed surfaces in M (for any i, j ∈ {1, ..., n}, ifi≠j, Fi is not parallel to
In this paper,we study upper bounds of the first eigenvalue of a complete noncompact submanifold in an(n + p)-dimensional hyperbolic space Hn+p.In particular,we