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Books in Mathematics

The Mathematics collection presents a range of foundational and advanced research content across applied and discrete mathematics, including fields such as Computational Mathematics; Differential Equations; Linear Algebra; Modelling & Simulation; Numerical Analysis; Probability & Statistics.

  • Singular Perturbations I

    Spaces and Singular Perturbations on Manifolds Without Boundary
    • 1st Edition
    • Volume 23
    • L.S. Frank
    • English
    Singular perturbations, one of the central topics in asymptotic analysis, also play a special role in describing physical phenomena such as the propagation of waves in media in the presence of small energy dissipations or dispersions, the appearance of boundary or interior layers in fluid and gas dynamics, as well as in elasticity theory, semi-classical asymptotic approximations in quantum mechanics etc. Elliptic and coercive singular perturbations are of special interest for the asymptotic solution of problems which are characterized by boundary layer phenomena, e.g. the theory of thin buckling plates, elastic rods and beams. This first volume deals with linear singular perturbations (on smooth manifolds without boundary) considered as equicontinuous linear mappings between corresponding families of Sobolev-Slobodetski'... type spaces of vectorial order.
  • Discrete Cosine Transform

    Algorithms, Advantages, Applications
    • 1st Edition
    • K. Ramamohan Rao + 1 more
    • English
    This is the first comprehensive treatment of the theoretical aspects of the discrete cosine transform (DCT), which is being recommended by various standards organizations, such as the CCITT, ISO etc., as the primary compression tool in digital image coding. The main purpose of the book is to provide a complete source for the user of this signal processing tool, where both the basics and the applications are detailed. An extensive bibliography covers both the theory and applications of the DCT. The novice will find the book useful in its self-contained treatment of the theory of the DCT, the detailed description of various algorithms supported by computer programs and the range of possible applications, including codecs used for teleconferencing, videophone, progressive image transmission, and broadcast TV. The more advanced user will appreciate the extensive references. Tables describing ASIC VLSI chips for implementing DCT, and motion estimation and details on image compression boards are also provided.
  • Matrix Perturbation Theory

    • 1st Edition
    • G. W. Stewart + 1 more
    • English
    This book is a comprehensive survey of matrix perturbation theory, a topic of interest to numerical analysts, statisticians, physical scientists, and engineers. In particular, the authors cover perturbation theory of linear systems and least square problems, the eignevalue problem, and the generalized eignevalue problem as wellas a complete treatment of vector and matrix norms, including the theory of unitary invariant norms.
  • Model Theory

    • 3rd Edition
    • Volume 73
    • C.C. Chang + 1 more
    • English
    Since the second edition of this book (1977), Model Theory has changed radically, and is now concerned with fields such as classification (or stability) theory, nonstandard analysis, model-theoretic algebra, recursive model theory, abstract model theory, and model theories for a host of nonfirst order logics. Model theoretic methods have also had a major impact on set theory, recursion theory, and proof theory.This new edition has been updated to take account of these changes, while preserving its usefulness as a first textbook in model theory. Whole new sections have been added, as well as new exercises and references. A number of updates, improvements and corrections have been made to the main text.
  • Principles of Real Analysis

    • 2nd Edition
    • Charalambos D. Aliprantis + 1 more
    • English
    This major textbook on real analysis is now available in a corrected and slightly amended reprint. It covers the basic theory of integration in a clear, well-organized manner using an imaginative and highly practical synthesis of the 'Daniell method' and the measure-theoretic approach. It is the ideal text for senior undergraduate and first-year graduate courses in real analysis, assuming student familiarity with advanced calculus and basic algebraic concepts.
  • Eulerian Graphs and Related Topics

    • 1st Edition
    • Volume 1
    • English
  • Almost Free Modules

    Set-Theoretic Methods
    • 1st Edition
    • Volume 46
    • P.C. Eklof + 1 more
    • English
    This is an extended treatment of the set-theoretic techniques which have transformed the study of abelian group and module theory over the last 15 years. Part of the book is new work which does not appear elsewhere in any form. In addition, a large body of material which has appeared previously (in scattered and sometimes inaccessible journal articles) has been extensively reworked and in many cases given new and improved proofs. The set theory required is carefully developed with algebraists in mind, and the independence results are derived from explicitly stated axioms. The book contains exercises and a guide to the literature and is suitable for use in graduate courses or seminars, as well as being of interest to researchers in algebra and logic.
  • Uniform Fréchet Algebras

    • 1st Edition
    • Volume 162
    • H. Goldmann
    • English
    The first part of this monograph is an elementary introduction to the theory of Fréchet algebras. Important examples of Fréchet algebras, which are among those considered, are the algebra of all holomorphic functions on a (hemicompact) reduced complex space, and the algebra of all continuous functions on a suitable topological space.The problem of finding analytic structure in the spectrum of a Fréchet algebra is the subject of the second part of the book. In particular, the author pays attention to function algebraic characterizations of certain Stein algebras (= algebras of holomorphic functions on Stein spaces) within the class of Fréchet algebras.
  • Spinors and Calibrations

    • 1st Edition
    • F. Reese Harvey
    • English
    Progress in mathematics is based on a thorough understanding of the mathematical objects under consideration, and yet many textbooks and monographs proceed to discuss general statements and assume that the reader can and will provide the mathematical infrastructure of examples and counterexamples. This book makes a deliberate effort to correct this situation: it is a collection of examples. The following table of contents describes its breadth and reveals the underlying motivation--differen... geometry--in its many facets: Riemannian, symplectic, K*adahler, hyperK*adahler, as well as complex and quaternionic.
  • Unitary Representations and Harmonic Analysis

    An Introduction
    • 2nd Edition
    • Volume 44
    • M. Sugiura
    • English
    The principal aim of this book is to give an introduction to harmonic analysis and the theory of unitary representations of Lie groups. The second edition has been brought up to date with a number of textual changes in each of the five chapters, a new appendix on Fatou's theorem has been added in connection with the limits of discrete series, and the bibliography has been tripled in length.
  • Induced Modules over Group Algebras

    • 1st Edition
    • Volume 161
    • G. Karpilovsky
    • English
    In 1898 Frobenius discovered a construction which, in present terminology, associates with every module of a subgroup the induced module of a group. This construction proved to be of fundamental importance and is one of the basic tools in the entire theory of group representations.This monograph is designed for research mathematicians and advanced graduate students and gives a picture of the general theory of induced modules as it exists at present. Much of the material has until now been available only in research articles. The approach is not intended to be encyclopedic, rather each topic is considered in sufficient depth that the reader may obtain a clear idea of the major results in the area.After establishing algebraic preliminaries, the general facts about induced modules are provided, as well as some of their formal properties, annihilators and applications. The remaining chapters include detailed information on the process of induction from normal subgroups, projective summands of induced modules, some basic results of the Green theory with refinements and extensions, simple induction and restriction pairs and permutation modules. The final chapter is based exclusively on the work of Weiss, presenting a number of applications to the isomorphism problem for group rings.
  • Scattering Theory, Revised Edition

    • 1st Edition
    • Volume 26
    • Peter D. Lax + 1 more
    • English
    This revised edition of a classic book, which established scattering theory as an important and fruitful area of research, reflects the wealth of new results discovered in the intervening years. This new, revised edition should continue to inspire researchers to expand the application of the original ideas proposed by the authors.
  • An Introduction to Complex Analysis in Several Variables

    • 3rd Edition
    • Volume 7
    • L. Hormander
    • English
    A number of monographs of various aspects of complex analysis in several variables have appeared since the first version of this book was published, but none of them uses the analytic techniques based on the solution of the Neumann Problem as the main tool. The additions made in this third, revised edition place additional stress on results where these methods are particularly important. Thus, a section has been added presenting Ehrenpreis' ``fundamental principle'' in full. The local arguments in this section are closely related to the proof of the coherence of the sheaf of germs of functions vanishing on an analytic set. Also added is a discussion of the theorem of Siu on the Lelong numbers of plurisubharmonic functions. Since the L2 techniques are essential in the proof and plurisubharmonic functions play such an important role in this book, it seems natural to discuss their main singularities.
  • Automorphic Forms, Shimura Varieties, and L-functions

    Proceedings of a Conference held at the University of Michigan, Ann Arbor, July 6-16, 1988
    • 1st Edition
    • Laurent Clozel + 1 more
    • English
  • Using Disk and RAM Utilities

    • 1st Edition
    • Ian Sinclair
    • English
  • Students' Guide to Spreadsheets

    • 1st Edition
    • Ian Sinclair
    • English
  • Passive Components

    A User's Guide
    • 1st Edition
    • Ian Sinclair
    • English
  • Directory of Portable Databases

    Count on Cuadra/Elsevier for All Your Database Information Needs
    • 1st Edition
    • Sam Stuart
    • English
  • The VMS User's Guide

    • 1st Edition
    • James F. Peters + 1 more
    • English
    The VMS User's Guide
  • Institutions and Applications

    Proceedings of the Symposium on the History of Modern Mathematics, Vassar College, Poughkeepsie, New York, June 20-24, 1989
    • 1st Edition
    • David E. Rowe + 1 more
    • English
    The History of Modern Mathematics, Volume II: Institutions and Applications focuses on the history and progress of methodologies, techniques, principles, and approaches involved in modern mathematics. The selection first elaborates on crystallographic symmetry concepts and group theory, case of potential theory and electrodynamics, and geometrization of analytical mechanics. Discussions focus on differential geometry and least action, intrinsic differential geometry, physically-motivated research in potential theory, introduction of potentials in electrodynamics, and group theory and crystallography in the mid-19th century. The text then elaborates on Schouten, Levi-Civita, and emergence of tensor calculus, modes and manners of applied mathematics, and pure and applied mathematics in divergent institutional settings in Germany. Topics include function of mathematics within technical colleges, evolvement of the notion of applied mathematics, rise of technical colleges, and an engineering approach to mechanics. The publication examines the transformation of numerical analysis by the computer; mathematics at the Berlin Technische Hochschule/Technisch... Universität; and contribution of mathematical societies to promoting applications of mathematics in Germany. The selection is a valuable reference for mathematicians and researchers interested in the history of modern mathematics.
  • Scattering Theory for Hyperbolic Operators

    • 1st Edition
    • Volume 21
    • V. Petkov
    • English
    Scattering Theory for dissipative and time-dependent systems has been intensively studied in the last fifteen years. The results in this field, based on various tools and techniques, may be found in many published papers.This monograph presents an approach which can be applied to spaces of both even and odd dimension. The ideas on which the approach is based are connected with the RAGE type theorem, with Enss' decomposition of the phase space and with a time-dependent proof of the existence of the operator W which exploits the decay of the local energy of the perturbed and free systems. Some inverse scattering problems for time-dependent potentials, and moving obstacles with an arbitrary geometry, are also treated in the book.
  • Combinatorial Designs

    A Tribute to Haim Hanani
    • 1st Edition
    • Volume 42
    • A. Hartman
    • English
    Haim Hanani pioneered the techniques for constructing designs and the theory of pairwise balanced designs, leading directly to Wilson's Existence Theorem. He also led the way in the study of resolvable designs, covering and packing problems, latin squares, 3-designs and other combinatorial configurations.The Hanani volume is a collection of research and survey papers at the forefront of research in combinatorial design theory, including Professor Hanani's own latest work on Balanced Incomplete Block Designs. Other areas covered include Steiner systems, finite geometries, quasigroups, and t-designs.
  • Geometry of Manifolds

    • 1st Edition
    • K. Shiohama
    • English
    This volume contains the papers presented at a symposium on differential geometry at Shinshu University in July of 1988. Carefully reviewed by a panel of experts, the papers pertain to the following areas of research: dynamical systems, geometry of submanifolds and tensor geometry, lie sphere geometry, Riemannian geometry, Yang-Mills Connections, and geometry of the Laplace operator.
  • Logic, Methodology and Philosophy of Science VIII

    • 1st Edition
    • Volume 126
    • J.E. Fenstad + 2 more
    • English
    Logic, Methodology and Philosophy of Science VIII presents the results of recent research into the foundations of science. The volume contains 37 invited papers presented at the Congress, covering the areas of Logic, Mathematics, Physical Sciences, Biological Sciences and the Humanities.
  • Logic Colloquium '88

    • 1st Edition
    • Volume 127
    • R. Ferro + 3 more
    • English
    The result of the European Summer Meeting of the Association for Symbolic Logic, this volume gives an overview of the latest developments in most of the major fields of logic being actively pursued today.As well as selected papers, the two panel discussions are also included, on ``Trends in Logic'' and ``The Teaching of Logic''.
  • Topics in General Topology

    • 1st Edition
    • Volume 41
    • K. Morita + 1 more
    • English
    Being an advanced account of certain aspects of general topology, the primary purpose of this volume is to provide the reader with an overview of recent developments.The papers cover basic fields such as metrization and extension of maps, as well as newly-developed fields like categorical topology and topological dynamics. Each chapter may be read independently of the others, with a few exceptions. It is assumed that the reader has some knowledge of set theory, algebra, analysis and basic general topology.
  • Graph Theory and Combinatorics 1988

    • 1st Edition
    • Volume 43
    • B. Bollobás
    • English
    Combinatorics has not been an established branch of mathematics for very long: the last quarter of a century has seen an explosive growth in the subject. This growth has been largely due to the doyen of combinatorialists, Paul Erdős, whose penetrating insight and insatiable curiosity has provided a huge stimulus for workers in the field. There is hardly any branch of combinatorics that has not been greatly enriched by his ideas.This volume is dedicated to Paul Erdős on the occasion of his seventy-fifth birthday.
  • Computability, Complexity, Logic

    • 1st Edition
    • Volume 128
    • E. Börger
    • English
    The theme of this book is formed by a pair of concepts: the concept of formal language as carrier of the precise expression of meaning, facts and problems, and the concept of algorithm or calculus, i.e. a formally operating procedure for the solution of precisely described questions and problems.The book is a unified introduction to the modern theory of these concepts, to the way in which they developed first in mathematical logic and computability theory and later in automata theory, and to the theory of formal languages and complexity theory. Apart from considering the fundamental themes and classical aspects of these areas, the subject matter has been selected to give priority throughout to the new aspects of traditional questions, results and methods which have developed from the needs or knowledge of computer science and particularly of complexity theory.It is both a textbook for introductory courses in the above-mentioned disciplines as well as a monograph in which further results of new research are systematically presented and where an attempt is made to make explicit the connections and analogies between a variety of concepts and constructions.
  • Large Deviations

    • 1st Edition
    • Volume 137
    • English
    The first four chapters of this volume are based on lectures given by Stroock at MIT in 1987. They form an introduction to the basic ideas of the theory of large deviations and make a suitable package on which to base a semester-length course for advanced graduate students with a strong background in analysis and some probability theory. A large selection of exercises presents important material and many applications. The last two chapters present various non-uniform results (Chapter 5) and outline the analytic approach that allows one to test and compare techniques used in previous chapters (Chapter 6).
  • Topological Fields

    • 1st Edition
    • Volume 157
    • S. Warner
    • English
    Aimed at those acquainted with basic point-set topology and algebra, this text goes up to the frontiers of current research in topological fields (more precisely, topological rings that algebraically are fields).The reader is given enough background to tackle the current literature without undue additional preparation. Many results not in the text (and many illustrations by example of theorems in the text) are included among the exercises. Sufficient hints for the solution of the exercises are offered so that solving them does not become a major research effort for the reader. A comprehensive bibliography completes the volume.
  • Clifford Theory for Group Representations

    • 1st Edition
    • Volume 156
    • G. Karpilovsky
    • English
    Let N be a normal subgroup of a finite group G and let F be a field. An important method for constructing irreducible FG-modules consists of the application (perhaps repeated) of three basic operations: (i) restriction to FN. (ii) extension from FN. (iii) induction from FN. This is the `Clifford Theory' developed by Clifford in 1937. In the past twenty years, the theory has enjoyed a period of vigorous development. The foundations have been strengthened and reorganized from new points of view, especially from the viewpoint of graded rings and crossed products.The purpose of this monograph is to tie together various threads of the development in order to give a comprehensive picture of the current state of the subject. It is assumed that the reader has had the equivalent of a standard first-year graduate algebra course, i.e. familiarity with basic ring-theoretic, number-theoretic and group-theoretic concepts, and an understanding of elementary properties of modules, tensor products and fields.
  • Vertex Operator Algebras and the Monster

    • 1st Edition
    • Volume 134
    • Igor Frenkel + 2 more
    • English
    This work is motivated by and develops connections between several branches of mathematics and physics--the theories of Lie algebras, finite groups and modular functions in mathematics, and string theory in physics. The first part of the book presents a new mathematical theory of vertex operator algebras, the algebraic counterpart of two-dimensional holomorphic conformal quantum field theory. The remaining part constructs the Monster finite simple group as the automorphism group of a very special vertex operator algebra, called the "moonshine module" because of its relevance to "monstrous moonshine."
  • Variational Methods in Nonconservative Phenomena

    • 1st Edition
    • Volume 182
    • B. D. Vujanovic + 1 more
    • English
    This book provides a comprehensive survey of analytic and approximate solutions of problems of applied mechanics, with particular emphasis on nonconservative phenomena. Include
  • Handbook of Boolean Algebras

    • 1st Edition
    • Volume 2
    • Bozzano G Luisa
    • English
  • Infinite Crossed Products

    • 1st Edition
    • Volume 135
    • English
  • Topics in Field Theory

    • 1st Edition
    • Volume 155
    • G. Karpilovsky
    • English
    This monograph gives a systematic account of certain important topics pertaining to field theory, including the central ideas, basic results and fundamental methods.Avoiding excessive technical detail, the book is intended for the student who has completed the equivalent of a standard first-year graduate algebra course. Thus it is assumed that the reader is familiar with basic ring-theoretic and group-theoretic concepts. A chapter on algebraic preliminaries is included, as well as a fairly large bibliography of works which are either directly relevant to the text or offer supplementary material of interest.
  • Logic-Based Decision Support

    Mixed Integer Model Formulation
    • 1st Edition
    • Volume 40
    • R.G. Jeroslow
    • English
    This monograph is based on a series of lectures given by the author at the first Advanced Research Institute on Discrete Applied Mathematics, held at Rutgers University. It emphasizes connections between the representational aspects of mixed integer programming and applied logic, as well as discussing logic-based approaches to decision support which help to create more `intelligent' systems. Dividing naturally into two parts, the first four chapters are an overview of mixed-integer programming representability techniques. This is followed by five chapters on applied logic, expert systems, logic and databases, and complexity theory. It concludes with a summary of open research issues and an attempt to extrapolate trends in this rapidly developing area.
  • Recent Topics in Nonlinear PDE IV

    • 1st Edition
    • Volume 160
    • English
  • Graph Colouring and Variations

    • 1st Edition
    • Volume 39
    • D. de Werra + 1 more
    • English
  • Coordinating User Interfaces for Consistency

    • 1st Edition
    • Jakob Nielsen
    • English
  • The Psychology of Learning and Motivation

    Advances in Research and Theory
    • 1st Edition
    • Robert D. Hawkins + 1 more
    • English
  • Infinite-Dimensional Topology

    Prerequisites and Introduction
    • 1st Edition
    • Volume 43
    • J. van Mill
    • English
    The first part of this book is a text for graduate courses in topology. In chapters 1 - 5, part of the basic material of plane topology, combinatorial topology, dimension theory and ANR theory is presented. For a student who will go on in geometric or algebraic topology this material is a prerequisite for later work. Chapter 6 is an introduction to infinite-dimensional topology; it uses for the most part geometric methods, and gets to spectacular results fairly quickly. The second part of this book, chapters 7 & 8, is part of geometric topology and is meant for the more advanced mathematician interested in manifolds. The text is self-contained for readers with a modest knowledge of general topology and linear algebra; the necessary background material is collected in chapter 1, or developed as needed.One can look upon this book as a complete and self-contained proof of Toruńczyk's Hilbert cube manifold characterization theorem: a compact ANR X is a manifold modeled on the Hilbert cube if and only if X satisfies the disjoint-cells property. In the process of proving this result several interesting and useful detours are made.
  • Graph Theory in Memory of G.A. Dirac

    • 1st Edition
    • Volume 41
    • L. Døvling Andersen + 4 more
    • English
    This volume is a tribute to the life and mathematical work of G.A. Dirac (1925-1984). One of the leading graph theorists, he developed methods of great originality and made many fundamental discoveries.The forty-two papers are all concerned with (or related to) Dirac's main lines of research. A number of mathematicians pay tribute to his memory by presenting new results in different areas of graph theory. Among the topics included are paths and cycles, hamiltonian graphs, vertex colouring and critical graphs, graphs and surfaces, edge-colouring, and infinite graphs.Some of the papers were originally presented at a meeting held in Denmark in 1985. Attendance being by invitation only, some 55 mathematicians from 14 countries participated in various lectures and discussions on graph theory related to the work of Dirac. This volume contains contributions from others as well, so should not be regarded only as the proceedings of that meeting. A problems section is included, as well as a listing of Dirac's own publications.
  • Statistical Reasoning in Law and Public Policy

    Tort Law, Evidence and Health
    • 1st Edition
    • Volume 2
    • Joseph L. Gastwirth
    • English
    To reach reasoned decisions involving issues of public policy and law, statistical data and studies often need to be assessed for their accuracy and relevance. This two-volume set presents a unique and comprehensive treatment of statistical methods in legal practice. Designed to serve as a text or reference, the book presents basic concepts of probability and statistical inference applied to actual data arising from court cases concerning discrimination, trademark evidence, environmental and occupational exposure to toxic chemicals, and related health and safety topics. Substantial attention is devoted to assessing the strengths and weaknesses of statistical studies, with examples illustrating why some health studies may not have been properly designed at the outset and how actual decisions might have been reversed had more appropriate analysis of data been available to the court. This book will be of interest to lawyers and other practitioners of the law, as well as to students and researchers in the areas of statistics, statistical economics, political science, and law.
  • Constructivism in Mathematics, Vol 2

    • 1st Edition
    • Volume 123
    • A.S. Troelstra + 1 more
    • English
    Studies in Logic and the Foundations of Mathematics, Volume 123: Constructivism in Mathematics: An Introduction, Vol. II focuses on various studies in mathematics and logic, including metric spaces, polynomial rings, and Heyting algebras. The publication first takes a look at the topology of metric spaces, algebra, and finite-type arithmetic and theories of operators. Discussions focus on intuitionistic finite-type arithmetic, theories of operators and classes, rings and modules, linear algebra, polynomial rings, fields and local rings, complete separable metric spaces, and located sets. The text then examines proof theory of intuitionistic logic, theory of types and constructive set theory, and choice sequences. The book elaborates on semantical completeness, sheaves, sites, and higher-order logic, and applications of sheaf models. Topics include a derived rule of local continuity, axiom of countable choice, forcing over sites, sheaf models for higher-order logic, and complete Heyting algebras. The publication is a valuable reference for mathematicians and researchers interested in mathematics and logic.
  • General Theory of Markov Processes

    • 1st Edition
    • Volume 133
    • English
  • Introduction to Operator Theory and Invariant Subspaces

    • 1st Edition
    • Volume 42
    • B. Beauzamy
    • English
    This monograph only requires of the reader a basic knowledge of classical analysis: measure theory, analytic functions, Hilbert spaces, functional analysis. The book is self-contained, except for a few technical tools, for which precise references are given.Part I starts with finite-dimensional spaces and general spectral theory. But very soon (Chapter III), new material is presented, leading to new directions for research. Open questions are mentioned here. Part II concerns compactness and its applications, not only spectral theory for compact operators (Invariant Subspaces and Lomonossov's Theorem) but also duality between the space of nuclear operators and the space of all operators on a Hilbert space, a result which is seldom presented. Part III contains Algebra Techniques: Gelfand's Theory, and application to Normal Operators. Here again, directions for research are indicated. Part IV deals with analytic functions, and contains a few new developments. A simplified, operator-oriented, version is presented. Part V presents dilations and extensions: Nagy-Foias dilation theory, and the author's work about C1-contractions. Part VI deals with the Invariant Subspace Problem, with positive results and counter-examples.In general, much new material is presented. On the Invariant Subspace Problem, the level of research is reached, both in the positive and negative directions.
  • Extreme Value Theory in Engineering

    • 1st Edition
    • Enrique Castillo
    • English
    This book is a comprehensive guide to extreme value theory in engineering. Written for the end user with intermediate and advanced statistical knowledge, it covers classical methods as well as recent advances. A collection of 150 examples illustrates the theoretical results and takes the reader from simple applications through complex cases of dependence.
  • Unimodality, Convexity, and Applications

    • 1st Edition
    • English
    In this book, the basic notions and tools of unimodality as they relate to probability and statistics are presented. In addition, many applications are covered; these include the use of unimodality to obtain monotonicity properties of power functions of multivariate tests, minimum volume confidence regions, and recurrence of symmetric random walks. The diversity of the applications will convince the reader that unimodality and convexity form an important tool in the hands of a researcher in probability and statistics.