What's the fundamental group of a punctured torus?

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Discussion Overview

The discussion revolves around the fundamental group of a punctured torus, exploring different interpretations and representations of its topology. Participants examine the implications of various topological transformations and their effects on the fundamental group, engaging in a debate about the correct characterization of this mathematical concept.

Discussion Character

  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant claims the fundamental group of a punctured torus is Z*Z*Z, based on the fundamental group of a torus being Z*Z.
  • Another participant suggests that a punctured torus can be continuously deformed into two cylinders glued to a square patch, implying that the fundamental group could be Z*Z.
  • A different participant acknowledges the existence of an extra loop related to the punctured hole but ultimately aligns with the idea that the fundamental group is Z*Z.
  • One participant challenges the initial claim about the fundamental group of the torus, stating it is ZxZ instead of Z*Z.

Areas of Agreement / Disagreement

Participants express conflicting views regarding the fundamental group of a punctured torus, with no consensus reached on the correct characterization. Multiple competing interpretations are presented.

Contextual Notes

There are unresolved assumptions regarding the definitions and transformations applied to the punctured torus, as well as the implications of different representations of the fundamental group.

kakarotyjn
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The fundamental group of a torus is Z*Z,then the fundamental group of a punctured torus is Z*Z*Z.

But I've ever done a problem,it said a punctured torus can be continuously deformed into two cylinders glued to a square patch.Really?

If that is right,then the fundamental group of punctured torus is Z*Z.

Which is right?Need help:smile:
 

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Yes, it's true... imagine making the hole bigger and bigger.. make it as big as you can withouth changing the topology. You're left with the two strips glued on a square patch.
 
oh,i see.the fundamental group should be Z*Z. i consider an extra loop,which is the edge circle of the punctured hole. but now I know it's the 2 power of a generator.
 
The fundamental group of the torus is not Z*Z though, it is ZxZ.
 

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