Theorems in complex analysis | Article proofs | Analytic functions
In complex analysis, a complex-valued function of a complex variable : * is said to be holomorphic at a point if it is differentiable at every point within some open disk centered at , and * is said to be analytic at if in some open disk centered at it can be expanded as a convergent power series (this implies that the radius of convergence is positive). One of the most important theorems of complex analysis is that holomorphic functions are analytic and vice versa. Among the corollaries of this theorem are * the identity theorem that two holomorphic functions that agree at every point of an infinite set with an accumulation point inside the intersection of their domains also agree everywhere in every connected open subset of their domains that contains the set , and * the fact that, since power series are infinitely differentiable, so are holomorphic functions (this is in contrast to the case of real differentiable functions), and * the fact that the radius of convergence is always the distance from the center to the nearest non-removable singularity; if there are no singularities (i.e., if is an entire function), then the radius of convergence is infinite. Strictly speaking, this is not a corollary of the theorem but rather a by-product of the proof. * no bump function on the complex plane can be entire. In particular, on any connected open subset of the complex plane, there can be no bump function defined on that set which is holomorphic on the set. This has important ramifications for the study of complex manifolds, as it precludes the use of partitions of unity. In contrast the partition of unity is a tool which can be used on any real manifold. (Wikipedia).
Complex analysis: Analytic continuation
This lecture is part of an online undergraduate course on complex analysis. We discuss analytic continuation, which is the extraordinary property that the values of a holomorphic function near one point determine its values at point far away. We give two examples of this: the gamma functi
From playlist Complex analysis
Complex analysis: Holomorphic functions
This lecture is part of an online undergraduate course on complex analysis. We define holomorphic (complex differentiable) functions, and discuss their basic properties, in particular the Cauchy-Riemann equations. For the other lectures in the course see https://www.youtube.com/playlist
From playlist Complex analysis
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From playlist Algebraic & Complex Geometry
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Recall: analytic functions are infinitely (term-by-term) differentiable. Relation of coefficients and values of derivatives. Remark: analytic functions completely determined by values on an arbitrarily small interval. Analytic functions: convergence at an endpoint implies continuity the
From playlist Math 131 Spring 2022 Principles of Mathematical Analysis (Rudin)
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This lecture is part of an online undergraduate course on complex analysis. We discuss the different sorts of singularities of a holomorphic function (removable singularities, poles, essential singularities, branch-points, limits of singularities, natural boundaries) and give examples of
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Find this video and other talks given by worldwide mathematicians on CIRM's Audiovisual Mathematics Library: http://library.cirm-math.fr. And discover all its functionalities: - Chapter markers and keywords to watch the parts of your choice in the video - Videos enriched with abstracts, b
From playlist Analysis and its Applications
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In this short lecture I will prove the Hartogs theorem stating that holomorphic functions can be continued across compacts subsets if the dimension is at least 2. The proof will use solution of the del bar problem with compact support. For more details see Section 2.3 in Hormander's "Intro
From playlist Several Complex Variables
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On local interdefinability of analytic functions - T. Servi - Workshop 3 - CEB T1 2018
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Holomorphic rigid geometric structures on compact manifolds by Sorin Dumitrescu
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From playlist Higgs Bundles
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We describe three compactifications of the complex numbers: The one point compactification, the Riemann Sphere and the complex projective line. In a subsequent video we explain the following facts: *Why all holomorphic functions on the compactification are constant. *Why endomorphism of PP
From playlist The Riemann Sphere
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We define domains of holomorphy in C^n. We introduce holomorphically convex domains. We state the Cartan-Thullen theorem, and list consequences. One if them provides the existence of a smallest domain of holomorphy containing a fixed domain. For more details see Hormander's "An introducti
From playlist Several Complex Variables
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From playlist Mathematics
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From playlist Analytic Number Theory
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