The author considers semilinear parabolic equations of the form u_t=u_xx+f(u),\quad x\in \mathbb R,t>0, where f a C^1 function. Assuming that 0 and \gamma >0 are constant steady states, the author investigates the large-time behavior of the front-like solutions, that is, solutions u whose initial values u(x,0) are near \gamma for x\approx -\infty and near 0 for x\approx \infty . If the steady states 0 and \gamma are both stable, the main theorem shows that at large times, the graph of u(\cdot ,t) is arbitrarily close to a propagating terrace (a system of stacked traveling fonts). The author.
The theory of travelling waves described by parabolic equations and systems is a rapidly developing branch of modern mathematics. This book presents a general picture of current results about wave solutions of parabolic systems, their existence, stability, and bifurcations. With introductory material accessible to non-mathematicians and a nearly complete bibliography of about 500 references, this book is an excellent resource on the subject.
This textbook presents a special solution to underdetermined linear systems where the number of nonzero entries in the solution is very small compared to the total number of entries. This is called a sparse solution. Since underdetermined linear systems can be very different, the authors explain how to compute a sparse solution using many approaches. Sparse Solutions of Underdetermined Linear Systems and Their Applications contains 64 algorithms for finding sparse solutions of underdetermined linear systems and their applications for matrix completion, graph clustering, and phase retrieval and provides a detailed explanation of these algorithms including derivations and convergence analysis. Exercises for each chapter help readers understand the material. This textbook is appropriate for graduate students in math and applied math, computer science, statistics, data science, and engineering. Advisors and postdoctoral scholars will also find the book interesting and useful.
This book gives an up-to-date exposition on the theory of oblique derivative problems for elliptic equations. The modern analysis of shock reflection was made possible by the theory of oblique derivative problems developed by the author. Such problems also arise in many other physical situations such as the shape of a capillary surface and problems of optimal transportation. The author begins the book with basic results for linear oblique derivative problems and work through the theory for quasilinear and nonlinear problems. The final chapter discusses some of the applications. In addition, notes to each chapter give a history of the topics in that chapter and suggestions for further reading.
This book deals with the ecological effect a species can have when it moves into an environment that it has not previously occupied (commonly referred to as an 'Invasion'). It is unique in presenting a clear and accessible introduction to a highly complex area - the modelling of biological invasions. The book presents the latest theories and models developed from studies into this crucial area. It includes data and examples from biological case studies showing how the models can be applied to the study of invasions, whether dealing with AIDS, the European rabbit, or prickly pear cactuses. - ;In nature, all organisms migrate or disperse to some extent, either by walking, swimming, flying, or being transported by wind or water. When a species succeeds in colonising an area that it has not previously inhabited, this is referred to as an `invasion'. Humans can precipitate biological invasions often spreading disease or pests by their travels around the world. Using the large amount of data that has been collected from studies worldwide, ranging from pest control to epidemiology, it has been possible to construct mathematical models that can predict which species will become an invader, what kind of habitat is susceptible to invasion by a particular species, and how fast an invasion will spread if it occurs. This book presents a clear and accessible introduction to this highly complex area. Included are data and examples from biological case studies showing how these models can be applied to the study of invasions, whether dealing with AIDS, the European rabbit, or prickly pear cactuses. -
Population dynamics is an important subject in mathematical biology. A cen tral problem is to study the long-term behavior of modeling systems. Most of these systems are governed by various evolutionary equations such as difference, ordinary, functional, and partial differential equations (see, e. g. , [165, 142, 218, 119, 55]). As we know, interactive populations often live in a fluctuating environment. For example, physical environmental conditions such as temperature and humidity and the availability of food, water, and other resources usually vary in time with seasonal or daily variations. Therefore, more realistic models should be nonautonomous systems. In particular, if the data in a model are periodic functions of time with commensurate period, a periodic system arises; if these periodic functions have different (minimal) periods, we get an almost periodic system. The existing reference books, from the dynamical systems point of view, mainly focus on autonomous biological systems. The book of Hess [106J is an excellent reference for periodic parabolic boundary value problems with applications to population dynamics. Since the publication of this book there have been extensive investigations on periodic, asymptotically periodic, almost periodic, and even general nonautonomous biological systems, which in turn have motivated further development of the theory of dynamical systems. In order to explain the dynamical systems approach to periodic population problems, let us consider, as an illustration, two species periodic competitive systems dUI dt = !I(t,Ul,U2), (0.
Theoretical advances in dynamical-systems theory and their applications to pattern-forming processes in the sciences and engineering are discussed in this volume that resulted from the conference Patterns in Dynamics held in honor of Bernold Fiedler, in Berlin, July 25-29, 2016.The contributions build and develop mathematical techniques, and use mathematical approaches for prediction and control of complex systems. The underlying mathematical theories help extract structures from experimental observations and, conversely, shed light on the formation, dynamics, and control of spatio-temporal patterns in applications. Theoretical areas covered include geometric analysis, spatial dynamics, spectral theory, traveling-wave theory, and topological data analysis; also discussed are their applications to chemotaxis, self-organization at interfaces, neuroscience, and transport processes.
In these notes we give a unified treatment of semilinear nonautonomous diffusion equations and systems thereof, which satisfy a comparison principle, and whose coefficient functions depend periodically on time. Such equations arise naturally, e. g. in biomathematics if one admits dependence of the data on daily, monthly, or seasonal variations. Typical examples considered are the logistic equation with diffusion, Fisher's equation of population genetics, and Volterra-Lotka systems (with diffusion) of competition and of the predator-prey type. The existence and qualitative properties of periodic solutions, and the asymptotic behaviour of solutions of the initial-value problem are studied. Basic underlying concepts are strongly order-preserving discrete semigroups and the principal eigenvalue of a periodic-parabolic operator.
The book is about reaction-diffusion equations in unbounded domains with a special emphasis on traveling waves and their generalizations as well as on different notions of propagation. It includes a general presentation of all the classical results in this area. Even for some well known results, in some cases, original proofs are included which are simpler and more elegant than the known ones. The book gives a fairly comprehensive and coherent account of the recent developments and current research in this active area. It also contains some of the basic results about elliptic and parabolic partial differential equations and a chapter on the different versions of the maximum principles. Thus, it also serves as an introduction to these topics. Each chapter is made as much autonomous as possible. Each one has a specific introduction as well as brief mentions of extensions or of related subjects. Some outstanding open problems are mentioned along the way. Each introduction states the goals of the chapter, some of its main results, the framework and indicates how the chapter is organized. The book is addressed to researchers and graduate students in mathematics, in particular in analysis, partial differential equations and applied mathematics. It will be of interest as well to researchers and graduate students concerned by mathematical modeling in physics and in biology. It is planed to be a reference book of lasting value with all the important results on a topic which is commonly used in these fields.
