Geometric Theory of Singular Phenomena in Partial Differential Equations

Download Geometric Theory of Singular Phenomena in Partial Differential Equations PDF Online Free

Author :
Publisher : Cambridge University Press
ISBN 13 : 9780521632461
Total Pages : 198 pages
Book Rating : 4.6/5 (324 download)

DOWNLOAD NOW!


Book Synopsis Geometric Theory of Singular Phenomena in Partial Differential Equations by : Jean Pierre Bourguignon

Download or read book Geometric Theory of Singular Phenomena in Partial Differential Equations written by Jean Pierre Bourguignon and published by Cambridge University Press. This book was released on 1998-05-28 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gathers together papers from a workshop held in Cortona, Italy. The contributions come from a group of outstanding mathematicians and together they cover the most recent advances in the geometric theory of singular phenomena of partial differential equations occurring in real and complex differential geometry. This volume will be of great interest to all those whose research interests lie in real and complex differential geometry, partial differential equations, and gauge theory.

Variational Problems in Riemannian Geometry

Download Variational Problems in Riemannian Geometry PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 9783764324322
Total Pages : 176 pages
Book Rating : 4.3/5 (243 download)

DOWNLOAD NOW!


Book Synopsis Variational Problems in Riemannian Geometry by : Paul Baird

Download or read book Variational Problems in Riemannian Geometry written by Paul Baird and published by Springer Science & Business Media. This book was released on 2004-03-26 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book collects invited contributions by specialists in the domain of elliptic partial differential equations and geometric flows. The articles provide a balance between introductory surveys and the most recent research, with a unique perspective on singular phenomena. Notions such as scans and the study of the evolution by curvature of networks of curves are completely new and lead the reader to the frontiers of the domain. The intended readership are postgraduate students and researchers in the fields of elliptic and parabolic partial differential equations that arise from variational problems, as well as researchers in related fields such as particle physics and optimization.

Glimpses of Soliton Theory

Download Glimpses of Soliton Theory PDF Online Free

Author :
Publisher : American Mathematical Society
ISBN 13 : 1470472627
Total Pages : 366 pages
Book Rating : 4.4/5 (74 download)

DOWNLOAD NOW!


Book Synopsis Glimpses of Soliton Theory by : Alex Kasman

Download or read book Glimpses of Soliton Theory written by Alex Kasman and published by American Mathematical Society. This book was released on 2023-03-30 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book challenges and intrigues from beginning to end. It would be a treat to use for a capstone course or senior seminar. —William J. Satzer, MAA Reviews on Glimpses of Soliton Theory (First Edition) Solitons are nonlinear waves which behave like interacting particles. When first proposed in the 19th century, leading mathematical physicists denied that such a thing could exist. Now they are regularly observed in nature, shedding light on phenomena like rogue waves and DNA transcription. Solitons of light are even used by engineers for data transmission and optical switches. Furthermore, unlike most nonlinear partial differential equations, soliton equations have the remarkable property of being exactly solvable. Explicit solutions to those equations provide a rare window into what is possible in the realm of nonlinearity. Glimpses of Soliton Theory reveals the hidden connections discovered over the last half-century that explain the existence of these mysterious mathematical objects. It aims to convince the reader that, like the mirrors and hidden pockets used by magicians, the underlying algebro-geometric structure of soliton equations provides an elegant explanation of something seemingly miraculous. Assuming only multivariable calculus and linear algebra, the book introduces the reader to the KdV Equation and its multisoliton solutions, elliptic curves and Weierstrass $wp$-functions, the algebra of differential operators, Lax Pairs and their use in discovering other soliton equations, wedge products and decomposability, the KP Hierarchy, and Sato's theory relating the Bilinear KP Equation to the geometry of Grassmannians. Notable features of the book include: careful selection of topics and detailed explanations to make the subject accessible to undergraduates, numerous worked examples and thought-provoking exercises, footnotes and lists of suggested readings to guide the interested reader to more information, and use of Mathematica® to facilitate computation and animate solutions. The second edition refines the exposition in every chapter, adds more homework exercises and projects, updates references, and includes new examples involving non-commutative integrable systems. Moreover, the chapter on KdV multisolitons has been greatly expanded with new theorems providing a thorough analysis of their behavior and decomposition.

Directions in Partial Differential Equations

Download Directions in Partial Differential Equations PDF Online Free

Author :
Publisher : Academic Press
ISBN 13 : 1483269248
Total Pages : 259 pages
Book Rating : 4.4/5 (832 download)

DOWNLOAD NOW!


Book Synopsis Directions in Partial Differential Equations by : Michael G. Crandall

Download or read book Directions in Partial Differential Equations written by Michael G. Crandall and published by Academic Press. This book was released on 2014-05-10 with total page 259 pages. Available in PDF, EPUB and Kindle. Book excerpt: Directions in Partial Differential Equations covers the proceedings of the 1985 Symposium by the same title, conducted by the Mathematics Research Center, held at the University of Wisconsin, Madison. This book is composed of 13 chapters and begins with reviews of the calculus of variations and differential geometry. The subsequent chapters deal with the study of development of singularities, regularity theory, hydrodynamics, mathematical physics, asymptotic behavior, and critical point theory. Other chapters discuss the use of probabilistic methods, the modern theory of Hamilton-Jacobi equations, the interaction between theory and numerical methods for partial differential equations. The remaining chapters explore attempts to understand oscillatory phenomena in solutions of nonlinear equations. This book will be of great value to mathematicians and engineers.

Geometric Analysis and Nonlinear Partial Differential Equations

Download Geometric Analysis and Nonlinear Partial Differential Equations PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 3642556272
Total Pages : 663 pages
Book Rating : 4.6/5 (425 download)

DOWNLOAD NOW!


Book Synopsis Geometric Analysis and Nonlinear Partial Differential Equations by : Stefan Hildebrandt

Download or read book Geometric Analysis and Nonlinear Partial Differential Equations written by Stefan Hildebrandt and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 663 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is not a textbook, but rather a coherent collection of papers from the field of partial differential equations. Nevertheless we believe that it may very well serve as a good introduction into some topics of this classical field of analysis which, despite of its long history, is highly modem and well prospering. Richard Courant wrote in 1950: "It has always been a temptationfor mathematicians to present the crystallized product of their thought as a deductive general theory and to relegate the individual mathematical phenomenon into the role of an example. The reader who submits to the dogmatic form will be easily indoctrinated. Enlightenment, however, must come from an understanding of motives; live mathematical development springs from specific natural problems which can be easily understood, but whose solutions are difficult and demand new methods or more general significance. " We think that many, if not all, papers of this book are written in this spirit and will give the reader access to an important branch of analysis by exhibiting interest ing problems worth to be studied. Most of the collected articles have an extensive introductory part describing the history of the presented problems as well as the state of the art and offer a well chosen guide to the literature. This way the papers became lengthier than customary these days, but the level of presentation is such that an advanced graduate student should find the various articles both readable and stimulating.

Qualitative Analysis of Nonlinear Elliptic Partial Differential Equations

Download Qualitative Analysis of Nonlinear Elliptic Partial Differential Equations PDF Online Free

Author :
Publisher : Hindawi Publishing Corporation
ISBN 13 : 9774540395
Total Pages : 205 pages
Book Rating : 4.7/5 (745 download)

DOWNLOAD NOW!


Book Synopsis Qualitative Analysis of Nonlinear Elliptic Partial Differential Equations by : Vicentiu D. Radulescu

Download or read book Qualitative Analysis of Nonlinear Elliptic Partial Differential Equations written by Vicentiu D. Radulescu and published by Hindawi Publishing Corporation. This book was released on 2008 with total page 205 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive introduction to the mathematical theory of nonlinear problems described by elliptic partial differential equations. These equations can be seen as nonlinear versions of the classical Laplace equation, and they appear as mathematical models in different branches of physics, chemistry, biology, genetics, and engineering and are also relevant in differential geometry and relativistic physics. Much of the modern theory of such equations is based on the calculus of variations and functional analysis. Concentrating on single-valued or multivalued elliptic equations with nonlinearities of various types, the aim of this volume is to obtain sharp existence or nonexistence results, as well as decay rates for general classes of solutions. Many technically relevant questions are presented and analyzed in detail. A systematic picture of the most relevant phenomena is obtained for the equations under study, including bifurcation, stability, asymptotic analysis, and optimal regularity of solutions. The method of presentation should appeal to readers with different backgrounds in functional analysis and nonlinear partial differential equations. All chapters include detailed heuristic arguments providing thorough motivation of the study developed later on in the text, in relationship with concrete processes arising in applied sciences. A systematic description of the most relevant singular phenomena described in this volume includes existence (or nonexistence) of solutions, unicity or multiplicity properties, bifurcation and asymptotic analysis, and optimal regularity. The book includes an extensive bibliography and a rich index, thus allowing for quick orientation among the vast collection of literature on the mathematical theory of nonlinear phenomena described by elliptic partial differential equations.

Partial Differential Equations

Download Partial Differential Equations PDF Online Free

Author :
Publisher : John Wiley & Sons
ISBN 13 : 0470054565
Total Pages : 467 pages
Book Rating : 4.4/5 (7 download)

DOWNLOAD NOW!


Book Synopsis Partial Differential Equations by : Walter A. Strauss

Download or read book Partial Differential Equations written by Walter A. Strauss and published by John Wiley & Sons. This book was released on 2007-12-21 with total page 467 pages. Available in PDF, EPUB and Kindle. Book excerpt: Our understanding of the fundamental processes of the natural world is based to a large extent on partial differential equations (PDEs). The second edition of Partial Differential Equations provides an introduction to the basic properties of PDEs and the ideas and techniques that have proven useful in analyzing them. It provides the student a broad perspective on the subject, illustrates the incredibly rich variety of phenomena encompassed by it, and imparts a working knowledge of the most important techniques of analysis of the solutions of the equations. In this book mathematical jargon is minimized. Our focus is on the three most classical PDEs: the wave, heat and Laplace equations. Advanced concepts are introduced frequently but with the least possible technicalities. The book is flexibly designed for juniors, seniors or beginning graduate students in science, engineering or mathematics.

Singular Elliptic Problems

Download Singular Elliptic Problems PDF Online Free

Author :
Publisher :
ISBN 13 :
Total Pages : 322 pages
Book Rating : 4.F/5 ( download)

DOWNLOAD NOW!


Book Synopsis Singular Elliptic Problems by : Marius Ghergu

Download or read book Singular Elliptic Problems written by Marius Ghergu and published by . This book was released on 2008-04-24 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive introduction to the mathematical theory of nonlinear problems described by singular elliptic equations. There are carefully analyzed logistic type equations with boundary blow-up solutions and generalized Lane-Emden-Fowler equations or Gierer-Meinhardt systems with singular nonlinearity in anisotropic media. These nonlinear problems appear as mathematical models in various branches of Physics, Mechanics, Genetics, Economics, Engineering, and they are also relevant in Quantum Physics and Differential Geometry. One of the main purposes of this volume is to deduce decay rates for general classes of solutions in terms of estimates of particular problems. Much of the material included in this volume is devoted to the asymptotic analysis of solutions and to the qualitative study of related bifurcation problems. Numerical approximations illustrate many abstract results of this volume. A systematic description of the most relevant singular phenomena described in these lecture notes includes existence (or nonexistence) of solutions, unicity or multiplicity properties, bifurcation and asymptotic analysis, and optimal regularity. The method of presentation should appeal to readers with different backgrounds in functional analysis and nonlinear partial differential equations. All chapters include detailed heuristic arguments providing thorough motivation of the study developed later on in the text, in relationship with concrete processes arising in applied sciences. The book includes an extensive bibliography and a rich index, thus allowing for quick orientation among the vast collection of literature on the mathematical theory of nonlinear singular phenomena

Linear and Nonlinear Aspects of Vortices

Download Linear and Nonlinear Aspects of Vortices PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 146121386X
Total Pages : 342 pages
Book Rating : 4.4/5 (612 download)

DOWNLOAD NOW!


Book Synopsis Linear and Nonlinear Aspects of Vortices by : Frank Pacard

Download or read book Linear and Nonlinear Aspects of Vortices written by Frank Pacard and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aimed at mathematicians, physicists, engineers, and grad students, this monograph will be useful for the nonlinear analysis of problems arising in geometry or mathematical physics. The material presented covers recent and original results by the authors, and serves as an excellent classroom text or a valuable self-study resource.

Proceedings Of The International Congress Of Mathematicians 2010 (Icm 2010) (In 4 Volumes) - Vol. I: Plenary Lectures And Ceremonies, Vols. Ii-iv: Invited Lectures

Download Proceedings Of The International Congress Of Mathematicians 2010 (Icm 2010) (In 4 Volumes) - Vol. I: Plenary Lectures And Ceremonies, Vols. Ii-iv: Invited Lectures PDF Online Free

Author :
Publisher : World Scientific
ISBN 13 : 9814462934
Total Pages : 4137 pages
Book Rating : 4.8/5 (144 download)

DOWNLOAD NOW!


Book Synopsis Proceedings Of The International Congress Of Mathematicians 2010 (Icm 2010) (In 4 Volumes) - Vol. I: Plenary Lectures And Ceremonies, Vols. Ii-iv: Invited Lectures by : Rajendra Bhatia

Download or read book Proceedings Of The International Congress Of Mathematicians 2010 (Icm 2010) (In 4 Volumes) - Vol. I: Plenary Lectures And Ceremonies, Vols. Ii-iv: Invited Lectures written by Rajendra Bhatia and published by World Scientific. This book was released on 2011-06-06 with total page 4137 pages. Available in PDF, EPUB and Kindle. Book excerpt: ICM 2010 proceedings comprises a four-volume set containing articles based on plenary lectures and invited section lectures, the Abel and Noether lectures, as well as contributions based on lectures delivered by the recipients of the Fields Medal, the Nevanlinna, and Chern Prizes. The first volume will also contain the speeches at the opening and closing ceremonies and other highlights of the Congress.

Nonlinear Partial Differential Equations and Hyperbolic Wave Phenomena

Download Nonlinear Partial Differential Equations and Hyperbolic Wave Phenomena PDF Online Free

Author :
Publisher : American Mathematical Soc.
ISBN 13 : 082184976X
Total Pages : 402 pages
Book Rating : 4.8/5 (218 download)

DOWNLOAD NOW!


Book Synopsis Nonlinear Partial Differential Equations and Hyperbolic Wave Phenomena by : Norske videnskaps-akademi. Research Program on Nonlinear Partial Differential Equations

Download or read book Nonlinear Partial Differential Equations and Hyperbolic Wave Phenomena written by Norske videnskaps-akademi. Research Program on Nonlinear Partial Differential Equations and published by American Mathematical Soc.. This book was released on 2010-10-01 with total page 402 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents the state of the art in several directions of research conducted by renowned mathematicians who participated in the research program on Nonlinear Partial Differential Equations at the Centre for Advanced Study at the Norwegian Academy of Science and Letters, Oslo, Norway, during the academic year 2008-09. The main theme of the volume is nonlinear partial differential equations that model a wide variety of wave phenomena. Topics discussed include systems of conservation laws, compressible Navier-Stokes equations, Navier-Stokes-Korteweg type systems in models for phase transitions, nonlinear evolution equations, degenerate/mixed type equations in fluid mechanics and differential geometry, nonlinear dispersive wave equations (Korteweg-de Vries, Camassa-Holm type, etc.), and Poisson interface problems and level set formulations.

Geometric and Spectral Analysis

Download Geometric and Spectral Analysis PDF Online Free

Author :
Publisher : American Mathematical Soc.
ISBN 13 : 1470410435
Total Pages : 378 pages
Book Rating : 4.4/5 (74 download)

DOWNLOAD NOW!


Book Synopsis Geometric and Spectral Analysis by : Pierre Albin

Download or read book Geometric and Spectral Analysis written by Pierre Albin and published by American Mathematical Soc.. This book was released on 2014-12-01 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 2012, the Centre de Recherches Mathématiques was at the center of many interesting developments in geometric and spectral analysis, with a thematic program on Geometric Analysis and Spectral Theory followed by a thematic year on Moduli Spaces, Extremality and Global Invariants. This volume contains original contributions as well as useful survey articles of recent developments by participants from three of the workshops organized during these programs: Geometry of Eigenvalues and Eigenfunctions, held from June 4-8, 2012; Manifolds of Metrics and Probabilistic Methods in Geometry and Analysis, held from July 2-6, 2012; and Spectral Invariants on Non-compact and Singular Spaces, held from July 23-27, 2012. The topics covered in this volume include Fourier integral operators, eigenfunctions, probability and analysis on singular spaces, complex geometry, Kähler-Einstein metrics, analytic torsion, and Strichartz estimates. This book is co-published with the Centre de Recherches Mathématiques.

Hyperbolic Equations and Frequency Interactions

Download Hyperbolic Equations and Frequency Interactions PDF Online Free

Author :
Publisher : American Mathematical Soc.
ISBN 13 : 0821805924
Total Pages : 480 pages
Book Rating : 4.8/5 (218 download)

DOWNLOAD NOW!


Book Synopsis Hyperbolic Equations and Frequency Interactions by : Luis A. Caffarelli

Download or read book Hyperbolic Equations and Frequency Interactions written by Luis A. Caffarelli and published by American Mathematical Soc.. This book was released on 1999 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: The research topic for this IAS/PCMS Summer Session was nonlinear wave phenomena. Mathematicians from the more theoretical areas of PDEs were brought together with those involved in applications. The goal was to share ideas, knowledge, and perspectives. How waves, or "frequencies", interact in nonlinear phenomena has been a central issue in many of the recent developments in pure and applied analysis. It is believed that wavelet theory--with its simultaneous localization in both physical and frequency space and its lacunarity--is and will be a fundamental new tool in the treatment of the phenomena. Included in this volume are write-ups of the "general methods and tools" courses held by Jeff Rauch and Ingrid Daubechies. Rauch's article discusses geometric optics as an asymptotic limit of high-frequency phenomena. He shows how nonlinear effects are reflected in the asymptotic theory. In the article "Harmonic Analysis, Wavelets and Applications" by Daubechies and Gilbert the main structure of the wavelet theory is presented. Also included are articles on the more "specialized" courses that were presented, such as "Nonlinear Schrödinger Equations" by Jean Bourgain and "Waves and Transport" by George Papanicolaou and Leonid Ryzhik. Susan Friedlander provides a written version of her lecture series "Stability and Instability of an Ideal Fluid", given at the Mentoring Program for Women in Mathematics, a preliminary program to the Summer Session. This Summer Session brought together students, fellows, and established mathematicians from all over the globe to share ideas in a vibrant and exciting atmosphere. This book presents the compelling results. Members of the Mathematical Association of America (MAA) and the National Council of Teachers of Mathematics (NCTM) receive a 20% discount from list price.

Singularities and Groups in Bifurcation Theory

Download Singularities and Groups in Bifurcation Theory PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 1461245745
Total Pages : 551 pages
Book Rating : 4.4/5 (612 download)

DOWNLOAD NOW!


Book Synopsis Singularities and Groups in Bifurcation Theory by : Martin Golubitsky

Download or read book Singularities and Groups in Bifurcation Theory written by Martin Golubitsky and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 551 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bifurcation theory studies how the structure of solutions to equations changes as parameters are varied. The nature of these changes depends both on the number of parameters and on the symmetries of the equations. Volume I discusses how singularity-theoretic techniques aid the understanding of transitions in multiparameter systems. This volume focuses on bifurcation problems with symmetry and shows how group-theoretic techniques aid the understanding of transitions in symmetric systems. Four broad topics are covered: group theory and steady-state bifurcation, equicariant singularity theory, Hopf bifurcation with symmetry, and mode interactions. The opening chapter provides an introduction to these subjects and motivates the study of systems with symmetry. Detailed case studies illustrate how group-theoretic methods can be used to analyze specific problems arising in applications.

New Developments in Singularity Theory

Download New Developments in Singularity Theory PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 9401008345
Total Pages : 470 pages
Book Rating : 4.4/5 (1 download)

DOWNLOAD NOW!


Book Synopsis New Developments in Singularity Theory by : Dirk Wiersma

Download or read book New Developments in Singularity Theory written by Dirk Wiersma and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt: Singularities arise naturally in a huge number of different areas of mathematics and science. As a consequence, singularity theory lies at the crossroads of paths that connect many of the most important areas of applications of mathematics with some of its most abstract regions. The main goal in most problems of singularity theory is to understand the dependence of some objects of analysis, geometry, physics, or other science (functions, varieties, mappings, vector or tensor fields, differential equations, models, etc.) on parameters. The articles collected here can be grouped under three headings. (A) Singularities of real maps; (B) Singular complex variables; and (C) Singularities of homomorphic maps.

Inverse Acoustic and Electromagnetic Scattering Theory

Download Inverse Acoustic and Electromagnetic Scattering Theory PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 3662035375
Total Pages : 347 pages
Book Rating : 4.6/5 (62 download)

DOWNLOAD NOW!


Book Synopsis Inverse Acoustic and Electromagnetic Scattering Theory by : David Colton

Download or read book Inverse Acoustic and Electromagnetic Scattering Theory written by David Colton and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 347 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is devoted to the mathematical and numerical analysis of the inverse scattering problem for acoustic and electromagnetic waves. The second edition includes material on Newton’s method for the inverse obstacle problem, an elegant proof of uniqueness for the inverse medium problem, a discussion of the spectral theory of the far field operator and a method for determining the support of an inhomogeneous medium from far field data.

An Introduction to the Mathematical Theory of Inverse Problems

Download An Introduction to the Mathematical Theory of Inverse Problems PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 9780387945309
Total Pages : 304 pages
Book Rating : 4.9/5 (453 download)

DOWNLOAD NOW!


Book Synopsis An Introduction to the Mathematical Theory of Inverse Problems by : Andreas Kirsch

Download or read book An Introduction to the Mathematical Theory of Inverse Problems written by Andreas Kirsch and published by Springer Science & Business Media. This book was released on 1996-09-26 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: Following Keller [119] we call two problems inverse to each other if the for mulation of each of them requires full or partial knowledge of the other. By this definition, it is obviously arbitrary which of the two problems we call the direct and which we call the inverse problem. But usually, one of the problems has been studied earlier and, perhaps, in more detail. This one is usually called the direct problem, whereas the other is the inverse problem. However, there is often another, more important difference between these two problems. Hadamard (see [91]) introduced the concept of a well-posed problem, originating from the philosophy that the mathematical model of a physical problem has to have the properties of uniqueness, existence, and stability of the solution. If one of the properties fails to hold, he called the problem ill-posed. It turns out that many interesting and important inverse in science lead to ill-posed problems, while the corresponding di problems rect problems are well-posed. Often, existence and uniqueness can be forced by enlarging or reducing the solution space (the space of "models"). For restoring stability, however, one has to change the topology of the spaces, which is in many cases impossible because of the presence of measurement errors. At first glance, it seems to be impossible to compute the solution of a problem numerically if the solution of the problem does not depend continuously on the data, i. e. , for the case of ill-posed problems.