Bilinear Maps Complex Analysis

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SUMMARY

The discussion focuses on finding an analytic function g defined within the disk |z| ≤ 2, specifically with the condition g(2/3) = 0 and |g(z)| = 1 on the boundary |z| = 2. The relevant tool for this problem is the bilinear map, defined as Bα(z) = (z - α) / (1 - overline{α}z), which preserves the unit circle. Participants emphasize modifying this bilinear map to ensure it maps the circle |z| = 2 to |g(z)| = 1 while satisfying the zero condition at g(2/3).

PREREQUISITES
  • Understanding of analytic functions
  • Familiarity with bilinear maps
  • Knowledge of the maximum modulus theorem
  • Complex analysis concepts, particularly mapping properties
NEXT STEPS
  • Study the properties of bilinear maps in complex analysis
  • Learn how to apply the maximum modulus theorem effectively
  • Explore modifications of bilinear maps to achieve specific mapping conditions
  • Investigate analytic functions and their zeroes in complex domains
USEFUL FOR

Students and professionals in complex analysis, particularly those working on analytic functions and bilinear mappings, will benefit from this discussion.

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Homework Statement


Find a function [tex]g[/tex] analytic in [tex]|z|\leq 2[/tex], with [tex]g(2/3)=0[/tex] and [tex]|g(z)|= 1[/tex] on [tex]|z|=2[/tex]


Homework Equations


Bilinear maps

[tex]B_{\alpha}(z)=\frac{z-\alpha}{1-\overline{\alpha}z}[/tex]


[tex]|B_{\alpha}(z)|=1[/tex] on [tex]|z|=1[/tex]


The Attempt at a Solution


I tried using the maximum modulus theorem but I did not manage to find such a function.
 
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Why are you messing around with the maximum modulus theorem when your relevant equation is a bilinear map? Use the bilinear map. It maps the unit circle |z|=1 to the unit circle. Modify it so it maps the circle |z|=2 to |z|=1. Now you still have an 'a' in the function. Fix 'a' so that g(2/3)=0.
 

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