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2: Paper Source PDF document

Paper's Title:

Uniform Continuity and k-Convexity

Author(s):

Adel Afif Abdelkarim

Mathematics Department, Faculty of Science, J
erash University, Jerash
Jordan.

adelafifo_afifo@yahoo.com

Abstract:

A closed arcwise-connected subset A of Rn is called k-convex if for each positive number a and for all elements x and y in A there is a positive number b such that if the norm of x-y is less than or equal to b then the length of the shortest curve l(x,y) in A is less than k times the norm of x-y plus a. We show that a union of two non disjoint closed finite convex subsets need not be k-convex. Let f(x) be a uniformly continuous functions on a finite number of closed subsets A_{1},...,A_{n} of R^{n} such that the union of A_{j},...,A_{n},j=1,...,n-1 is k-convex. We show that f is uniformly continuous on the union of the sets A_{i},i=1,...,n. We give counter examples if this condition is not satisfied. As a corollary we show that if f(x) is uniformly continuous on each of two closed convex sets A,B then f(x) is uniformly continuous on the union of A and B.



1: Paper Source PDF document

Paper's Title:

On a Problem on Periodic Functions

Author(s):

Adel A. Abdelkarim

Mathematics Department, Faculty of Science,
Jerash Private University, Jerash,
Jordan.

E-mail: adelafifo_afifo@yahoo.com
 

Abstract:

Given a continuous periodic real function f with n translates  f1 ,..., fn , where fi(x)=f(x+ai), i=1,...,n. We solve a problem by Erdos and Chang and show that there are rational numbers r,s such that f(r)≥ fi(r), f(s)≤ fi(s), i=1,...,n. No restrictions on the constants or any further restriction on the function f are necessary as was imposed earlier.


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