Is Any Closed Curve Homotopic to a Constant Curve in a Simply Connected Region?

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In the discussion, the concept of null homotopy is explored, specifically regarding closed rectifiable curves in simply connected regions. According to the definition from John B. Conway's "Functions of One Complex Variable I," a curve γ is homotopic to zero if it can be continuously deformed to a constant curve. The conversation clarifies that while γ can be homotopic to a constant curve in a simply connected region G, it may not be homotopic to every constant curve, as demonstrated with the example of curves in the union of disks D0 and D3. This highlights the importance of path connectivity in the definition of simply connected regions.

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  • Understanding of homotopy theory
  • Familiarity with the concept of simply connected spaces
  • Knowledge of rectifiable curves
  • Basic principles of complex analysis
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  • Study the properties of simply connected spaces in topology
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  • Explore examples of null homotopic curves in various regions
  • Investigate the relationship between path connectivity and homotopy
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Mathematicians, topology students, and anyone interested in the properties of homotopy and complex analysis will benefit from this discussion.

variety
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I have a question about the definition of null homotopic. My textbook (Functions of one Complex Variable I by John B. Conway) defines it as follows: If \gamma is a closed rectifiable curve in a region G, then \gamma is homotopic to zero if \gamma is homotopic to a constant curve. My question is, if G is simply connected, then is \gamma homotopic to ANY constant curve in G? This seems obvious to me, but I'm not sure if I should prove it or just state it.
 
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Here's my joke: When is a curve that is homotopic to zero not homotopic to zero?

Answer: Let Dn be the open disk of radius 1 centered at n, and let G = union of D0 and D3. Then G is simply connected but not connected.

Let gamma be a curve in D3. Then gamma is homotopic to zero because it is homotopic to the constant curve alpha(t)=3.

However, gamma is not homotopic to the constant curve beta(t)=0, so one might say that gamma is not homotopic to "zero."
 
Your G would not be simply connected :/ It has to be path connected and therefore connected to be simply connected.
 
variety said:
I have a question about the definition of null homotopic. My textbook (Functions of one Complex Variable I by John B. Conway) defines it as follows: If \gamma is a closed rectifiable curve in a region G, then \gamma is homotopic to zero if \gamma is homotopic to a constant curve. My question is, if G is simply connected, then is \gamma homotopic to ANY constant curve in G? This seems obvious to me, but I'm not sure if I should prove it or just state it.
If G~c and G~c', then you would need to have c~c'...
 

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