This volume contains the proceedings of the conference on Formal and Analytic Solutions of Diff. Equations, held from June 28–July 2, 2021, and hosted by University of Alcalá, Alcalá de Henares, Spain. The manuscripts cover recent advances in the study of formal and analytic solutions of different kinds of equations such as ordinary differential equations, difference equations, $q$-difference equations, partial differential equations, moment differential equations, etc. Also discussed are related topics such as summability of formal solutions and the asymptotic study of their solutions. The volume is intended not only for researchers in this field of knowledge but also for students who aim to acquire new techniques and learn recent results.

These proceedings provide methods, techniques, different mathematical tools and recent results in the study of formal and analytic solutions to Diff. (differential, partial differential, difference, q-difference, q-difference-differential.... ) Equations. They consist of selected contributions from the conference "Formal and Analytic Solutions of Diff. Equations", held at Alcalá de Henares, Spain during September 4-8, 2017. Their topics include summability and asymptotic study of both ordinary and partial differential equations. The volume is divided into four parts. The first paper is a survey of the elements of nonlinear analysis. It describes the algorithms to obtain asymptotic expansion of solutions of nonlinear algebraic, ordinary differential, partial differential equations, and of systems of such equations. Five works on formal and analytic solutions of PDEs are followed by five papers on the study of solutions of ODEs. The proceedings conclude with five works on related topics, generalizations and applications. All contributions have been peer reviewed by anonymous referees chosen among the experts on the subject. The volume will be of interest to graduate students and researchers in theoretical and applied mathematics, physics and engineering seeking an overview of the recent trends in the theory of formal and analytic solutions of functional (differential, partial differential, difference, q-difference, q-difference-differential) equations in the complex domain.

The book provides the reader with an overview of the actual state of research in ordinary and partial differential equations in the complex domain. Topics include summability and asymptotic study of both ordinary and partial differential equations, and also q-difference and differential-difference equations. This book will be of interest to researchers and students who wish to expand their knowledge of these fields.With the latest results and research developments and contributions from experts in their field, Formal and Analytic Solutions of Differential Equations provides a valuable contribution to methods, techniques, different mathematical tools, and study calculations.

This series aims at reporting new developments of a high mathematical standard and of current interest. Each volume in the series shall be devoted to mathematical analysis that has been applied, or potentially applicable to the solutions of scientific, engineering, and social problems. The first volume of WSSIAA contains 42 research articles on differential equations by leading mathematicians from all over the world. This volume has been dedicated to V Lakshmikantham on his 65th birthday for his significant contributions in the field of differential equations. Contents:Semilinear and Quasilinear Stochastic Differential Equations in Banach Spaces (N U Ahmed)Asymptotic Behaviour of the Nonoscillating Solutions of First Order Linear Nonautonomous Neutral Equations (D Bainov & V Petrov)Boundary and Angular Layer Behavior in Singularly Perturbed Quasilinear Systems (K W Chang & G X Liu)Singular Perturbation for a System of Differential-Difference Equations (S-N Chow & W Huang)Bounds for Solutions Sets of Multivalued ODES (K Deimling)Comparison of Eigenvalues for a Class of Multipoint Boundary Value Problems (P W Eloe & J Henderson)A Solution to the General Bessel Moment Problem (W D Evans et al.)Boundedness in Linear Functional Differential Equations with Infinite Delay (J Kato)Foundation of Invariant Manifold Theory for Ordinary Differential Equations (H W Knobloch)and other papers Readership: Mathematicians and engineers. keywords:Differential Equations

In this volume which honors Professors W A Harris, Jr, M Iwano  Y Sibuya, active researchers from around the world report on their latest research results. Topics include Analytic Theory of Linear and Nonlinear Differential Equations, Asymptotic Expansions, Turning Points Theory, Special Functions, Delay Equations, Boundary Value Problems, Sturm-Liouville Eigenvalues, Periodic Solutions, Numerical Solutions and other areas of Applied Mathematics. Contents:Recent Developments in Complex Oscillation Theory (S B Bank)Multisummability and Stokes Phenomenon for Linear Meromorphic Differential Equations (B L J Braaksma)On a Generalization of Bessel Functions Satisfying Higher-Order Differential Equations (W N Everitt & C Markett)Distribution of Real Eigenvalues in Sturm-Liouville Problems with Infinitely Many Turning Points (H Gingold & T J Hempleman)A Generalized Singularity of the First Kind (W A Harris, Jr & Y Sibuya)Persistence of Singular Perturbation Solutions in Noisy Environments (F C Hoppensteadt)A New Method for a System of Two Nonlinear Equations without Poincaré's Conditions (M Iwano)On Regularizing Differential-Algebraic Equations (L V Kalachev ' R E O'Malley, Jr)Synthesizing Optimal Controls for Nonlinear Systems with Nonquadratic Cost Criteria (D L Russell)A Majorant Method for Differential Equations with a Singular Parameter (R Schäfke)On the Double Confluent Heun Equation (D Schmidt & G Wolf)The Gevrey Asymptotics and Exact Asymptotics (Y Sibuya)Universal Shapes of Rotating Incompressible Fluid Drops (D R Smith ' J E Ross)Computing Continuous Spectrum (A Zettl)and other papers Readership: Pure and applied mathematicians. keywords:

This volume consists of invited lecture notes, survey papers and original research papers from the AAGADE school and conference held in Będlewo, Poland in September 2015. The contributions provide an overview of the current level of interaction between algebra, geometry and analysis and demonstrate the manifold aspects of the theory of ordinary and partial differential equations, while also pointing out the highly fruitful interrelations between those aspects. These interactions continue to yield new developments, not only in the theory of differential equations but also in several related areas of mathematics and physics such as differential geometry, representation theory, number theory and mathematical physics. The main goal of the volume is to introduce basic concepts, techniques, detailed and illustrative examples and theorems (in a manner suitable for non-specialists), and to present recent developments in the field, together with open problems for more advanced and experienced readers. It will be of interest to graduate students, early-career researchers and specialists in analysis, geometry, algebra and related areas, as well as anyone interested in learning new methods and techniques.