Complex Analysis (Princeton Lectures in Analysis, Volume
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2006 Annual Report
Contents Clay Mathematics Institute 2006 James A. Carlson Letter from the President 2 Recognizing Achievement Fields Medal Winner Terence Tao 3 Persi Diaconis Mathematics & Magic Tricks 4 Annual Meeting Clay Lectures at Cambridge University 6 Researchers, Workshops & Conferences Summary of 2006 Research Activities 8 Profile Interview with Research Fellow Ben Green 10 Davar Khoshnevisan Normal Numbers are Normal 15 Feature Article CMI—Göttingen Library Project: 16 Eugene Chislenko The Felix Klein Protocols Digitized The Klein Protokolle 18 Summer School Arithmetic Geometry at the Mathematisches Institut, Göttingen, Germany 22 Program Overview The Ross Program at Ohio State University 24 PROMYS at Boston University Institute News Awards & Honors 26 Deadlines Nominations, Proposals and Applications 32 Publications Selected Articles by Research Fellows 33 Books & Videos Activities 2007 Institute Calendar 36 2006 Another major change this year concerns the editorial board for the Clay Mathematics Institute Monograph Series, published jointly with the American Mathematical Society. Simon Donaldson and Andrew Wiles will serve as editors-in-chief, while I will serve as managing editor. Associate editors are Brian Conrad, Ingrid Daubechies, Charles Fefferman, János Kollár, Andrei Okounkov, David Morrison, Cliff Taubes, Peter Ozsváth, and Karen Smith. The Monograph Series publishes Letter from the president selected expositions of recent developments, both in emerging areas and in older subjects transformed by new insights or unifying ideas. The next volume in the series will be Ricci Flow and the Poincaré Conjecture, by John Morgan and Gang Tian. Their book will appear in the summer of 2007. In related publishing news, the Institute has had the complete record of the Göttingen seminars of Felix Klein, 1872–1912, digitized and made available on James Carlson. -
Informal Lecture Notes for Complex Analysis
Informal lecture notes for complex analysis Robert Neel I'll assume you're familiar with the review of complex numbers and their algebra as contained in Appendix G of Stewart's book, so we'll pick up where that leaves off. 1 Elementary complex functions In one-variable real calculus, we have a collection of basic functions, like poly- nomials, rational functions, the exponential and log functions, and the trig functions, which we understand well and which serve as the building blocks for more general functions. The same is true in one complex variable; in fact, the real functions we just listed can be extended to complex functions. 1.1 Polynomials and rational functions We start with polynomials and rational functions. We know how to multiply and add complex numbers, and thus we understand polynomial functions. To be specific, a degree n polynomial, for some non-negative integer n, is a function of the form n n−1 f(z) = cnz + cn−1z + ··· + c1z + c0; 3 where the ci are complex numbers with cn 6= 0. For example, f(z) = 2z + (1 − i)z + 2i is a degree three (complex) polynomial. Polynomials are clearly defined on all of C. A rational function is the quotient of two polynomials, and it is defined everywhere where the denominator is non-zero. z2+1 Example: The function f(z) = z2−1 is a rational function. The denomina- tor will be zero precisely when z2 = 1. We know that every non-zero complex number has n distinct nth roots, and thus there will be two points at which the denominator is zero. -
MATH 305 Complex Analysis, Spring 2016 Using Residues to Evaluate Improper Integrals Worksheet for Sections 78 and 79
MATH 305 Complex Analysis, Spring 2016 Using Residues to Evaluate Improper Integrals Worksheet for Sections 78 and 79 One of the interesting applications of Cauchy's Residue Theorem is to find exact values of real improper integrals. The idea is to integrate a complex rational function around a closed contour C that can be arbitrarily large. As the size of the contour becomes infinite, the piece in the complex plane (typically an arc of a circle) contributes 0 to the integral, while the part remaining covers the entire real axis (e.g., an improper integral from −∞ to 1). An Example Let us use residues to derive the formula p Z 1 x2 2 π 4 dx = : (1) 0 x + 1 4 Note the somewhat surprising appearance of π for the value of this integral. z2 First, let f(z) = and let C = L + C be the contour that consists of the line segment L z4 + 1 R R R on the real axis from −R to R, followed by the semi-circle CR of radius R traversed CCW (see figure below). Note that C is a positively oriented, simple, closed contour. We will assume that R > 1. Next, notice that f(z) has two singular points (simple poles) inside C. Call them z0 and z1, as shown in the figure. By Cauchy's Residue Theorem. we have I f(z) dz = 2πi Res f(z) + Res f(z) C z=z0 z=z1 On the other hand, we can parametrize the line segment LR by z = x; −R ≤ x ≤ R, so that I Z R x2 Z z2 f(z) dz = 4 dx + 4 dz; C −R x + 1 CR z + 1 since C = LR + CR. -
Arxiv:1207.1472V2 [Math.CV]
SOME SIMPLIFICATIONS IN THE PRESENTATIONS OF COMPLEX POWER SERIES AND UNORDERED SUMS OSWALDO RIO BRANCO DE OLIVEIRA Abstract. This text provides very easy and short proofs of some basic prop- erties of complex power series (addition, subtraction, multiplication, division, rearrangement, composition, differentiation, uniqueness, Taylor’s series, Prin- ciple of Identity, Principle of Isolated Zeros, and Binomial Series). This is done by simplifying the usual presentation of unordered sums of a (countable) family of complex numbers. All the proofs avoid formal power series, double series, iterated series, partial series, asymptotic arguments, complex integra- tion theory, and uniform continuity. The use of function continuity as well as epsilons and deltas is kept to a mininum. Mathematics Subject Classification: 30B10, 40B05, 40C15, 40-01, 97I30, 97I80 Key words and phrases: Power Series, Multiple Sequences, Series, Summability, Complex Analysis, Functions of a Complex Variable. Contents 1. Introduction 1 2. Preliminaries 2 3. Absolutely Convergent Series and Commutativity 3 4. Unordered Countable Sums and Commutativity 5 5. Unordered Countable Sums and Associativity. 9 6. Sum of a Double Sequence and The Cauchy Product 10 7. Power Series - Algebraic Properties 11 8. Power Series - Analytic Properties 14 References 17 arXiv:1207.1472v2 [math.CV] 27 Jul 2012 1. Introduction The objective of this work is to provide a simplification of the theory of un- ordered sums of a family of complex numbers (in particular, for a countable family of complex numbers) as well as very easy proofs of basic operations and properties concerning complex power series, such as addition, scalar multiplication, multipli- cation, division, rearrangement, composition, differentiation (see Apostol [2] and Vyborny [21]), Taylor’s formula, principle of isolated zeros, uniqueness, principle of identity, and binomial series. -
Complex Logarithm
Complex Analysis Math 214 Spring 2014 Fowler 307 MWF 3:00pm - 3:55pm c 2014 Ron Buckmire http://faculty.oxy.edu/ron/math/312/14/ Class 14: Monday February 24 TITLE The Complex Logarithm CURRENT READING Zill & Shanahan, Section 4.1 HOMEWORK Zill & Shanahan, §4.1.2 # 23,31,34,42 44*; SUMMARY We shall return to the murky world of branch cuts as we expand our repertoire of complex functions when we encounter the complex logarithm function. The Complex Logarithm log z Let us define w = log z as the inverse of z = ew. NOTE Your textbook (Zill & Shanahan) uses ln instead of log and Ln instead of Log . We know that exp[ln |z|+i(θ+2nπ)] = z, where n ∈ Z, from our knowledge of the exponential function. So we can define log z =ln|z| + i arg z =ln|z| + i Arg z +2nπi =lnr + iθ where r = |z| as usual, and θ is the argument of z If we only use the principal value of the argument, then we define the principal value of log z as Log z, where Log z =ln|z| + i Arg z = Log |z| + i Arg z Exercise Compute Log (−2) and log(−2), Log (2i), and log(2i), Log (−4) and log(−4) Logarithmic Identities z = elog z but log ez = z +2kπi (Is this a surprise?) log(z1z2) = log z1 + log z2 z1 log = log z1 − log z2 z2 However these do not neccessarily apply to the principal branch of the logarithm, written as Log z. (i.e. is Log (2) + Log (−2) = Log (−4)? 1 Complex Analysis Worksheet 14 Math 312 Spring 2014 Log z: the Principal Branch of log z Log z is a single-valued function and is analytic in the domain D∗ consisting of all points of the complex plane except for those lying on the nonpositive real axis, where d 1 Log z = dz z Sketch the set D∗ and convince yourself that it is an open connected set. -
Complex Analysis
Complex Analysis Andrew Kobin Fall 2010 Contents Contents Contents 0 Introduction 1 1 The Complex Plane 2 1.1 A Formal View of Complex Numbers . .2 1.2 Properties of Complex Numbers . .4 1.3 Subsets of the Complex Plane . .5 2 Complex-Valued Functions 7 2.1 Functions and Limits . .7 2.2 Infinite Series . 10 2.3 Exponential and Logarithmic Functions . 11 2.4 Trigonometric Functions . 14 3 Calculus in the Complex Plane 16 3.1 Line Integrals . 16 3.2 Differentiability . 19 3.3 Power Series . 23 3.4 Cauchy's Theorem . 25 3.5 Cauchy's Integral Formula . 27 3.6 Analytic Functions . 30 3.7 Harmonic Functions . 33 3.8 The Maximum Principle . 36 4 Meromorphic Functions and Singularities 37 4.1 Laurent Series . 37 4.2 Isolated Singularities . 40 4.3 The Residue Theorem . 42 4.4 Some Fourier Analysis . 45 4.5 The Argument Principle . 46 5 Complex Mappings 47 5.1 M¨obiusTransformations . 47 5.2 Conformal Mappings . 47 5.3 The Riemann Mapping Theorem . 47 6 Riemann Surfaces 48 6.1 Holomorphic and Meromorphic Maps . 48 6.2 Covering Spaces . 52 7 Elliptic Functions 55 7.1 Elliptic Functions . 55 7.2 Elliptic Curves . 61 7.3 The Classical Jacobian . 67 7.4 Jacobians of Higher Genus Curves . 72 i 0 Introduction 0 Introduction These notes come from a semester course on complex analysis taught by Dr. Richard Carmichael at Wake Forest University during the fall of 2010. The main topics covered include Complex numbers and their properties Complex-valued functions Line integrals Derivatives and power series Cauchy's Integral Formula Singularities and the Residue Theorem The primary reference for the course and throughout these notes is Fisher's Complex Vari- ables, 2nd edition. -
4 Complex Analysis
4 Complex Analysis “He is not a true man of science who does not bring some sympathy to his studies, and expect to learn something by behavior as well as by application. It is childish to rest in the discovery of mere coincidences, or of partial and extraneous laws. The study of geometry is a petty and idle exercise of the mind, if it is applied to no larger system than the starry one. Mathematics should be mixed not only with physics but with ethics; that is mixed mathematics. The fact which interests us most is the life of the naturalist. The purest science is still biographical.” Henry David Thoreau (1817 - 1862) We have seen that we can seek the frequency content of a signal f (t) defined on an interval [0, T] by looking for the the Fourier coefficients in the Fourier series expansion In this chapter we introduce complex numbers and complex functions. We a ¥ 2pnt 2pnt will later see that the rich structure of f (t) = 0 + a cos + b sin . 2 ∑ n T n T complex functions will lead to a deeper n=1 understanding of analysis, interesting techniques for computing integrals, and The coefficients can be written as integrals such as a natural way to express analog and dis- crete signals. 2 Z T 2pnt an = f (t) cos dt. T 0 T However, we have also seen that, using Euler’s Formula, trigonometric func- tions can be written in a complex exponential form, 2pnt e2pint/T + e−2pint/T cos = . T 2 We can use these ideas to rewrite the trigonometric Fourier series as a sum over complex exponentials in the form ¥ 2pint/T f (t) = ∑ cne , n=−¥ where the Fourier coefficients now take the form Z T −2pint/T cn = f (t)e dt. -
Chapter 2 Complex Analysis
Chapter 2 Complex Analysis In this part of the course we will study some basic complex analysis. This is an extremely useful and beautiful part of mathematics and forms the basis of many techniques employed in many branches of mathematics and physics. We will extend the notions of derivatives and integrals, familiar from calculus, to the case of complex functions of a complex variable. In so doing we will come across analytic functions, which form the centerpiece of this part of the course. In fact, to a large extent complex analysis is the study of analytic functions. After a brief review of complex numbers as points in the complex plane, we will ¯rst discuss analyticity and give plenty of examples of analytic functions. We will then discuss complex integration, culminating with the generalised Cauchy Integral Formula, and some of its applications. We then go on to discuss the power series representations of analytic functions and the residue calculus, which will allow us to compute many real integrals and in¯nite sums very easily via complex integration. 2.1 Analytic functions In this section we will study complex functions of a complex variable. We will see that di®erentiability of such a function is a non-trivial property, giving rise to the concept of an analytic function. We will then study many examples of analytic functions. In fact, the construction of analytic functions will form a basic leitmotif for this part of the course. 2.1.1 The complex plane We already discussed complex numbers briefly in Section 1.3.5. -
Fefferman and Schoen Awarded 2017 Wolf Prize in Mathematics
COMMUNICATION Fefferman and Schoen Awarded 2017 Wolf Prize in Mathematics Biographical Sketch: Charles Fefferman Charles Fefferman was born in Washington, DC, in 1949. Showing exceptional ability in mathematics as a child, he entered the University of Maryland in 1963, at the age of fourteen, having bypassed high school. He published his first mathematics paper in a journal at the age of fifteen. In 1966, at the age of seventeen, he received his BS in mathematics and physics and was awarded a three-year NSF fellowship for research. He received his PhD from Princeton University in 1969 under the direction of Elias Stein. After spending the year 1969–1970 as a lecturer at Princeton, he accepted an assistant professorship at the University of Chicago. He was promoted to full professor in 1971—the youngest full professor ever appointed in Charles Fefferman Richard Schoen the United States. He returned to Princeton in 1973. He has been the recipient of a Sloan Foundation Fellowship Charles Fefferman of Princeton University and Richard (1970) and a NATO Postdoctoral Fellowship (1971). He Schoen of the University of California, Irvine, have been was awarded the Fields Medal in 1978. His many awards awarded the 2017 Wolf Prize in Mathematics by the Wolf and prizes include the Salem Prize (1971); the inaugural Foundation. Alan T. Waterman Award (1976); the Bergman Prize (1992); The prize citation reads: “Charles Fefferman has made and the Bôcher Memorial Prize of the AMS (2008). He was major contributions to several fields, including several elected to the American Academy of Arts and Sciences in complex variables, partial differential equations and 1972, the National Academy of Sciences in 1979, and the subelliptic problems. -
Duality Results in Banach and Quasi-Banach Spaces Of
DUALITY RESULTS IN BANACH AND QUASI-BANACH SPACES OF HOMOGENEOUS POLYNOMIALS AND APPLICATIONS VIN´ICIUS V. FAVARO´ AND DANIEL PELLEGRINO Abstract. Spaces of homogeneous polynomials on a Banach space are frequently equipped with quasi- norms instead of norms. In this paper we develop a technique to replace the original quasi-norm by a norm in a dual preserving way, in the sense that the dual of the space with the new norm coincides with the dual of the space with the original quasi-norm. Applications to problems on the existence and approximation of solutions of convolution equations and on hypercyclic convolution operators on spaces of entire functions are provided. Contents 1. Introduction 1 2. Main results 2 3. Prerequisites for the applications 9 3.1. Hypercyclicity results 11 3.2. Existence and approximation results 12 4. Applications 12 4.1. Lorentz nuclear and summing polynomials: the basics 12 4.2. New hypercyclic, existence and approximation results 14 References 22 Mathematics Subject Classifications (2010): 46A20, 46G20, 46A16, 46G25, 47A16. Key words: Banach and quasi-Banach spaces, homogeneous polynomials, entire functions, convolution operators, Lorentz sequence spaces. 1. Introduction arXiv:1503.01079v2 [math.FA] 28 Jul 2016 In the 1960s, many researchers began the study of spaces of holomorphic functions defined on infinite dimensional complex Banach spaces. In this context spaces of n-homogeneous polynomials play a central role in the development of the theory. Several tools, such as topological tensor products and duality theory, are useful and important when we are working with spaces of homogeneous polynomials. Many duality results on spaces of homogeneous polynomials and their applications have appeared in the last decades (see for instance [5, 8, 9, 10, 11, 12, 15, 20, 22, 26, 28, 29, 33, 34, 41, 46] among others). -
Preserving the Unity of Mathematics CONTENTS
ICMAT Newsletter #13 Autumn 2016 CSIC - UAM - UC3M - UCM EDITORIAL After the last European Congress of Mathematics, held between July 18th and July 22nd in Berlin, Marta Sanz-Solé, professor at the University of Barcelona, speaks about the European Mathematical Society, of which she was the Chair person between 2010 a 2014. The ECM: Preserving the Unity of Mathematics Less than one year ago, in October, 2015, the European Mathe- matical Society (EMS) celebrated its 25th anniversary. The place chosen to commemorate the event was the Institut Henri Poin- caré, the home of mathematics and theoretical physics in Paris since 1928. In that same year, the London Mathematical Soci- ety, one of the oldest mathematical societies in Europe, cele- brated its 150th anniversary, while many other societies have recently commemorated their 100th anniversary or are about to Rascon Image: Fernando do so. This difference in age may give rise to certain complexes, although there is no reason why this should happen. The EMS has enjoyed great success during its short existence, thanks to the well-defined space it occupies in a world that is advancing rapidly towards globalization, and the exclusively international scenario in which it carries out its functions. The conception and creation of the EMS in 1990 is better under- stood in the political context of Europe that arose after the tragic experience of World War II. In 1958, the communitary structure that currently underpins the Europan Union (EU) was estab- CONTENTS lished, on the basis of which the identity of Europe has been con- solidated, and the project, initially focused on the economy, has evolved along all fronts that affect the lives of those belonging Editorial: Marta Sanz-Solé (University of to the member states; in particular, education, research and in- Barcelona)..............................................................1 novation. -
The Legacy of Norbert Wiener: a Centennial Symposium
http://dx.doi.org/10.1090/pspum/060 Selected Titles in This Series 60 David Jerison, I. M. Singer, and Daniel W. Stroock, Editors, The legacy of Norbert Wiener: A centennial symposium (Massachusetts Institute of Technology, Cambridge, October 1994) 59 William Arveson, Thomas Branson, and Irving Segal, Editors, Quantization, nonlinear partial differential equations, and operator algebra (Massachusetts Institute of Technology, Cambridge, June 1994) 58 Bill Jacob and Alex Rosenberg, Editors, K-theory and algebraic geometry: Connections with quadratic forms and division algebras (University of California, Santa Barbara, July 1992) 57 Michael C. Cranston and Mark A. Pinsky, Editors, Stochastic analysis (Cornell University, Ithaca, July 1993) 56 William J. Haboush and Brian J. Parshall, Editors, Algebraic groups and their generalizations (Pennsylvania State University, University Park, July 1991) 55 Uwe Jannsen, Steven L. Kleiman, and Jean-Pierre Serre, Editors, Motives (University of Washington, Seattle, July/August 1991) 54 Robert Greene and S. T. Yau, Editors, Differential geometry (University of California, Los Angeles, July 1990) 53 James A. Carlson, C. Herbert Clemens, and David R. Morrison, Editors, Complex geometry and Lie theory (Sundance, Utah, May 1989) 52 Eric Bedford, John P. D'Angelo, Robert E. Greene, and Steven G. Krantz, Editors, Several complex variables and complex geometry (University of California, Santa Cruz, July 1989) 51 William B. Arveson and Ronald G. Douglas, Editors, Operator theory/operator algebras and applications (University of New Hampshire, July 1988) 50 James Glimm, John Impagliazzo, and Isadore Singer, Editors, The legacy of John von Neumann (Hofstra University, Hempstead, New York, May/June 1988) 49 Robert C. Gunning and Leon Ehrenpreis, Editors, Theta functions - Bowdoin 1987 (Bowdoin College, Brunswick, Maine, July 1987) 48 R.