On variations on quasi Cauchy sequences in metric spaces
For a fixed positive integer p. a sequence (x(n)) in a metric space X is called p-quasi-Cauchy if (Delta(p)x(n)) is a null sequence where Delta(p)x(n) = d(x(n+p), x(n)) for each positive integer n. A subset E of X is called p-ward compact if any sequence (x(n)) of points in E has a p-quasi-Cauchy subsequence. A subset of X is totally bounded if and only if it is p-ward compact. A function f from a subset E of X into a metric space Y is called p-ward continuous if it preserves p-quasi Cauchy sequences, i.e. (f(x(n))) is a p-quasi Cauchy sequence in Y whenever (x(n)) is a p-quasi Cauchy sequence of points of E. A function f from a totally bounded subset of X into Y preserves p-quasi Cauchy sequences if and only if it is uniformly continuous. If a function is uniformly continuous on a subset E of X into Y, then (f(x(n))) is p-quasi Cauchy in Y whenever (x(n)) is a quasi cauchy sequence of points in E.