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Material Type: Notes; Professor: Solomyak; Class: COMPLEX ANALYSIS; Subject: Mathematics; University: University of Washington - Seattle; Term: Spring 2008;
Typology: Study notes
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(1) State and sketch the proof of Runge’s Theorem. (2) State and sketch the proof of Mittag-Leffler Theorem. (3) State the Weierstrass Product Theorem and sketch the proof in the case when the domain is the entire complex plane. (4) Give the definition of the Gamma Function and state its basic properties (meromorphic continuation, zeros, poles, functional equation, product formula). (5) Give the definition of the Riemann Zeta Function and state a few of its properties (at least, Euler’s product formula, meromorphic continuation, poles, and what is known about the zeros). (6) Give the definition of a subharmonic function on a domain D ⊂ C and sketch the proof of the Strict Maximum Principle. (7) State and sketch the proof of Harnack’s Principle (about a sequence of positive harmonic functions on a planar domain). (8) Describe the Perron procedure for solving the Dirichlet problem on a planar domain. (9) Give the definition of subharmonic barrier and state the consequences of its existence. Give an explicit example of a subharmonic barrier. (10) Give the definition of the Green’s function for planar domains with piecewise analytic boundary and state its basic properties. (11) Give the definition of the Green’s function for general planar domains and state its basic properties. (12) Give the definition of a Riemann surface and give an example (e.g. the torus or the Riemann surface of log z) explicitly defining the coordinate maps. (13) Give the definition of the Green’s function on a Riemann surface (include the definition of a Perron family). When does the Green’s function exist? (14) Define the analytic continuation along a path and state the Monodromy Theorem (either in the complex plane or on a Riemann surface; it’s your choice). (15) State the Uniformization Theorem and indicate the main steps of the proof in the case when the Green’s function exists. (16) Give the definition of a covering map, the universal covering map, and covering trans- formations, and state their basic properties.
1 Let R = H \ {i}, where H is the upper half plane. Find the value gR(2i, 3 i) of the Green’s function at z = 2i with pole at q = 3i.
2 Let S be the strip S = {x + iy : 0 < y < 1 } and let A be the annulus A = {z : 1 < |z| < 2 }. Find (explicitly) a covering map π : S → A and determine all covering transformations.
3 Let R be a Riemann surface and suppose that there is a non-constant bounded analytic function φ : R → C. Show that R possesses a Green’s function. 4 Show that
f (s) =
p
n=
npns
is analytic in {σ > 1 } and that ζ(s) = exp(f (s)).
5 Prove that isolated singularities are removable for bounded harmonic functions.
6 Let u be subharmonic in D. Show that ∫ (^2) π
0
u(reit)dt
is increasing as a function of r (0 ≤ r < 1).
7 Using basic principles (e.g. considerations of uniform convergence, periodicity and Liouville’s Theorem), show that π^2 sin^2 πz =
n=−∞
(z − n)^2.
8 Write down an infinite product that converges to an entire function f (z) with zeros of order 1 at the points zn =
n, n ≥ 1, and no other zeros. Prove the convergence of your product.