Professor Paul Bracken is currently a Professor in the Department of Mathematics, at the University of Texas RGV in Edinburg, TX. He obtained his BSc degree from the University of Toronto and holds a Ph.D. from the University of Waterloo in Canada. His research interests include mathematical problems from the area of quantum mechanics and quantum field theory, differential geometry, a study of partial differential equations as well as their overlap with other problems in physics. He has published more than 160 papers in journals and books and has given many talks at different levels over the years. This is the seventh volume he has worked on with IntechOpen publishers.