Degree Level

A Continuous, Nowhere-Differentiable Function with a Dense Set of Proper Local Extrema (open access)

A Continuous, Nowhere-Differentiable Function with a Dense Set of Proper Local Extrema

In this paper, we use the following scheme to construct a continuous, nowhere-differentiable function ๐‘“ which is the uniform limit of a sequence of sawtooth functions ๐‘“โ‚™ : [0, 1] โ†’ [0, 1] with increasingly sharp teeth. Let ๐‘‹ = [0, 1] x [0, 1] and ๐น(๐‘‹) be the Hausdorff metric space determined by ๐‘‹. We define contraction maps ๐‘คโ‚ , ๐‘คโ‚‚ , ๐‘คโ‚ƒ on ๐‘‹. These maps define a contraction map ๐‘ค on ๐น(๐‘‹) via ๐‘ค(๐ด) = ๐‘คโ‚(๐ด) โ‹ƒ ๐‘คโ‚‚(๐ด) โ‹ƒ ๐‘คโ‚ƒ(๐ด). The iteration under ๐‘ค of the diagonal in ๐‘‹ defines a sequence of graphs of continuous functions ๐‘“โ‚™. Since ๐‘ค is a contraction map in the compact metric space ๐น(๐‘‹), ๐‘ค has a unique fixed point. Hence, these iterations converge to the fixed point-which turns out to be the graph of our continuous, nowhere-differentiable function ๐‘“. Chapter 2 contains the background we will need to engage our task. Chapter 3 includes two results from the Baire Category Theorem. The first is the well known fact that the set of continuous, nowhere-differentiable functions on [0,1] is a residual set in ๐ถ[0,1]. The second fact is that the set of continuous functions on [0,1] which have a dense set โ€ฆ
Date: December 1993
Creator: Huggins, Mark C. (Mark Christopher)
System: The UNT Digital Library
Weak and Norm Convergence of Sequences in Banach Spaces (open access)

Weak and Norm Convergence of Sequences in Banach Spaces

We study weak convergence of sequences in Banach spaces. In particular, we compare the notions of weak and norm convergence. Although these modes of convergence usually differ, we show that in โ„“ยน they coincide. We then show a theorem of Rosenthal's which states that if {๐“โ‚™} is a bounded sequence in a Banach space, then {๐“โ‚™} has a subsequence {๐“'โ‚™} satisfying one of the following two mutually exclusive alternatives; (i) {๐“'โ‚™} is weakly Cauchy, or (ii) {๐“'โ‚™} is equivalent to the unit vector basis of โ„“ยน.
Date: December 1993
Creator: Hymel, Arthur J. (Arthur Joseph)
System: The UNT Digital Library