Days & Times Room Instructor Meeting Dates ------------------------------------------------------------------------ TBA DMS238 Eric Olson 08/27/2012 - 12/19/2012
Homework 1 for September 4 0. Finish analyzing the radius of convergence of the power series where 4a_2=-a_0, 12a_3=-a_1 and 4(k+2)a_k+2=(k-2)a_k. 1. Read chapter 4 from Boyce and DiPrima on power series solutions to linear second order ordinary differential equations. 2. Review the proof of the Cauchy integral formula from page 37 of Carrier Krook and Pearson. 3. Review the proof of the Maximum Modulus Theoarm from page 42 of Carrier Krook and Pearson. 4. Read about analytic continuation on page 64 of Carrier, Krook and Pearson. 5. Explain how easy or difficult it is to understand pages 55 - 65 in Carrier, Krook and Pearson. Homework 2 for September 11 1. Boyce and Diprima page 166 problem 16. 2-3. Read section 2.1.1 and 2.2.1 in Rogers and Renardy. 4. Carrier, Krook and Pearson page 56 exercise 1. 5. Boyce and DiPrima page 190 problem 2. 6-8. Try to find a power series solution of (4-x^2)y''+2y=0 expanded around the points x_0=1, x_0=2 and x_0=3. 9. Use problem8 on page 37 of Carrier, Krook and Pearson to prove the power series we obtained is really a solution to the ODE. Homework 3 for September 18 1. Use the technique of solving for r such that |a_n| <= Cr^n to work problem 8 from last week. In particular, find a lower bound on the power series solution of (4-x^2) y'' + 2 y = 0 expanded about x0 = 3. 2. Finish Carrier, Krook and Pearson page 56 problem 1 for the annulus pi < |z| < 2 pi. 3. The point x0 = 2 is a regular singular point of (4-x^4) y'' + 2 y = 0 Find a solution to this equation. Determine whether there are two linearly independent solutions at x0 = 2. 4. Continue working on page 190 problem 2 of Boyce and DiPrima. Check that a0<>0, a2=-a0/4!, a4=a0/6! give the first three non-zero terms the power series solution for r = 1. 5. First the first three terms of the power series solution to page 190 problem 2 of Boyce and DiPrima for r = -1. 6-7. Read sections 2.2.2 and 2.2.3 in Rogers and Renardy. Homework 4 for September 25 1. Let h:C->C be such that h'(z)->L as z->a. Prove or disprove the following claims: a. There exists M such that h(z)->M as z->a. b. Let H(z)=M for z=a and h(z) otherwise. Then H'(z) exists. c. H'(z)=L. Let h:R->R be such that h'(x)->L as x->a. Do any hypothesis need to be added so the claims in the previous question hold? 2. There is a theorem which states that if f has an isolated singularity at a in C then either a. the discontinuity is removable, or b. __________________________________. What goes in the box? 3. Suppose x0 is a singular point of the ordinary differential equation p(x)y''+q(x)y'+r(x)y=0. For s not equal x0 define x->y(x,s) to be the solution to this differential equation satisfying the initial conditions y(s,s)=a0 and y'(s,s)=a1. a. Is it possible to define a function f in a neighborhood of x0 by formula f(x) = lim y(x,s) s->x and, if not, is there an additional hypothesis that can be added so f is well defined? b. Does y=f(x) satisfy the differential equation? c. Does f(x)=a0 and f'(x)=a1? 4. Continue reading Renardy and Rogers 2.2.2 and 2.2.3. Homework 5 for October 2 1. What happens with the Laurent series if the curve C passes through the point z? 2. Consider question 1 when the curve is smooth. 3. Consider question 1 when z is a corner point of C. 4. What is a corner point? 5. Read about principle value integrals in Carrier, Krook and Pearson page 39 and pages 413-418. Homework 6 for October 11 1. Print my solution to to page 36 # 8 in Carrier, Krook and Pearson. Read it and check for errors. 2. Write out a proof of item 1 in Rogers and Renardy page 47. 3. Verify the that C_alpha=(1/alpha!) D^alpha f(x) in item 3 of Rogers and Renardy page 47. Homework 7 for October 18 1. Suppose K is compact, fn(x) are continuous and there is M so large that Sum {|fn(x)| n=1..infinity} <= M for all x in K Prove or disprove the claim that Sum {|fn(x)| n=1..N} converges uniformly for x in K as N -> infinity. 2. Suppose K is compact, Pn(x) are polynomials of degree n and there is M so large that Sum {|Pn(x)| n=1..infinity} <= M for all x in K Prove or disprove the claim that Sum {|Pn(x)| n=1..N} converges uniformly for x in K as N -> infinity. 3. Let f(x) = exp(-1/x^2) if x<>0 = 0 if x=0 Prove or disprove that f(x)>0 for x<>0 d^nf(x)/dx^n=0 for x=0 and n=1,2,3.... 4. Find another example of a function g(x) such that g(x)>0 for x<>0 d^ng(x)/dx^n=0 for x=0 and n=1,2,3.... 5. Can Theorem 2.17 in Rogers and Renardy be rewritten as w C (Omega) = Intersection Union Union Intersection Cm,r(y) compact S in Omega m>0 r>0 y in S 6. Read proof of 2.15 and 2.17 in Rogers and Renardy. 7. Think about conformal maps. 8. Look up the Ascoli theorem. Homework 8 for October 25 1. Work problem 3 of page 123 and problems 1 and 3 on page 134 of Carrier, Krook and Pearson. 2. Answer the following questions about the pictures: (i) Why do the black lines meet at perpendicular? (ii) Why does the green dot move backwards? Homework 9 for November 8 1. Page 44 problems 4, 5, 6 of Carrier, Krook and Pearson. 2. Read Theorem 2.17 on page 48 in Renardy and Rogers and rewrite in terms of a single complex variable. 3. Read pages 49 to 60 in Renardy and Rogers. Homwork 10 for November 15 1. Prove that a closed and bounded set in C^n is compact. That is, show that if W is closed and bounded, then any open cover admits a finite subcover. 2. Fill in details of the proof of Theorem 2.17 for the forward implication in Renardy and Rogers.