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The fundamental Group of the Torus is abelian

This video illustrates the proof of the Theorem in the title. The proof goes like this: Consider a rectangle. Then the path going up the left side of the rectangle and then along the top is homeo...  
 
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randomlaughingman (3 months ago) Show Hide
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not exactly related to what the vid. is about, but wouldn't it be something similar to two trapezoids short-side-joined-together are required to make a torus, otherwise when it wraps the inner area is going to have loads of excess overlaps. i don't do higher-dimensional toplogy i just find it fascinating how people can think of processes (formulas) that describe actual-size wrapping of surfaces. but then it's likely textiles and measure knew all that, in the old ways (proportions to each other).
sergiorgio2000 (5 months ago) Show Hide
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But this transformation isn't contunuous (as homotopy must be), it cut the connetion point and change the connect components (if get of a point) in the start
jedibill111 (6 months ago) Show Hide
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MMMM...Donuts....
2t22tornadosiren (6 months ago) Show Hide
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That is not a donut. That is a torus.
musambajama (11 months ago) Show Hide
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Nice!
bushyblowfish (1 year ago) Show Hide
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don't you mean homotopic rather than homeomorphic in your info.
copernicus633 (1 year ago) Show Hide
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The video would be more effective if it had audio which: Defines what a group is; Then shows what the group elements are for this topological situation; Then points out that it is an Abelian (commutative) group
sorrysonofa (1 year ago) Show Hide
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I thought the torus' fundamental group was the free product of Z with it self... and so is noncommutative. is it the direct product?
robthomp47 (11 months ago) Show Hide
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You may be thinking of the figure eight space -- two circles joined together at a point. The fundamental group of a figure eight space is the free product of Z with itself. BTW, if you puncture the torus, i.e. delete a point, then the result is homotopy equivalent to a figure eight space, and so has the same fundamental group. You can see how the "missing point" would get in the way of the homotopy in the video.
kolomgorov (1 year ago) Show Hide
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Much easier to show that the torus is homeomorphic to S^1*S^1 and then remember that the fundamental group is a topological property. I like these videos though, I'm so bad at picturing this stuff.

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