Infinite intersection of open sets in C that is closed

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SUMMARY

The discussion focuses on finding an infinite intersection of open sets in the complex plane (ℂ) that results in a closed set. The sets defined are A_n = (-1/n, 1/n), which are open intervals in the real numbers (ℝ) that converge to the point 0. The intersection of these sets, ∩A_n, contains only the point 0, demonstrating that it is closed in ℝ. The conversation highlights the need to understand whether the proof for ℝ can be directly applied to ℂ or if a different approach is necessary.

PREREQUISITES
  • Understanding of open sets in topology
  • Familiarity with the concept of closed sets in metric spaces
  • Knowledge of the properties of real numbers (ℝ) and complex numbers (ℂ)
  • Basic principles of convergence in sequences
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  • Learn about the concept of open balls in metric spaces
  • Explore the differences between real analysis and complex analysis
  • Investigate examples of infinite intersections of sets in different topological spaces
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Homework Statement



Find an infinite intersection of open sets in C that is closed.

The Attempt at a Solution



Consider the sets A_n = (-1/n,1/n). Since 0 in A_n for all n, 0 in \bigcap A_{n}. Here I'm a little stuck -- is the proof in R analogous to the proof in C, or do I need a different example?
 
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I can't discern whether the example you give for ℝ is drawn from the book, or whether you're attempting to construct the proof first for ℝ and then generalize to ℂ. If it's the former then skip to the second paragraph, if it's the latter then try assuming there was another point in the infinite intersection and see if you can't derive a contradiction.

Your open interval (-1/n,1/n) in ℝ can more generally be called an open ball in ℝ centered at zero. There's a reason they call them open balls, think about it in ℂ.
 
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