Bücher der Reihe Developments in Mathematics

From the 28th of February through the 3rd of March, 2001, the Department of Math ematics of the University of Florida hosted a conference on the many aspects of the field of Ordered Algebraic Structures.

The contents of this volume range from expository papers on several aspects of number theory, intended for general readers (Steinhaus property of planar regions; Thus, Number Theory and Its Applications leads the reader in many ways not only to the state of the art of number theory but also to its rich garden.

In reproducing Volume 23 of The Ramanujan Journal in this book form, we have included two papers-one by Hei-Chi Chan and Shaun Cooper, and another by Ole Warnaar-which were intended for Volume 23 of The Ramanujan Journal, but appeared in other issues.

Covering leading-edge research, and with a focus on new developments in non-linear functional analysis, this is a vital addition to the literature that details theory as well as applications, providing relevant academics with a trusty guide to the field.

In the spirit of Ehrenpreis's contribution to mathematics, the papers in this volume, written by prominent mathematicians, represent the wide breadth of subjects that Ehrenpreis traversed in his career, including partial differential equations, combinatorics, number theory, complex analysis and a bit of applied mathematics.

This is devoted to exploration of the existence and uniqueness of solutions for various classes of Darboux problems for hyperbolic differential equations or inclusions involving the Caputo fractional derivative.