This classic work in mathematical physics provides a clear and accessible introduction to the theory of one-parameter groups and their applications to the solution of differential equations. Written by Abraham Cohen, a leading mathematician of the early 20th century, this book is an essential resource for anyone interested in the mathematics of physics and engineering.This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it.This work is in the "public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work.Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.