Torus Excluding Disc: Boundary of RP^2 X RP^2

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In summary, the boundary of a torus excluding a disc is homeomorphic to a ball. This can be seen by slicing out a disk from the torus, leaving a simply connected surface that resembles a ball. While there are infinitely many objects that the boundary of the torus could be homeomorphic to, the more interesting question is what it is homotopic to. Without the removed disc, the boundary of the torus has no boundary, making it homeomorphic to a ball.
  • #1
pivoxa15
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Homework Statement


What is the torus excluding a disc homeomorphic to?

What is the boundary of a torus (excluding a disc)?

The Attempt at a Solution


RP^2 X RP^2?

As a guess.
 
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  • #2
Excluding a disk? You mean you slice a disk out of the torus? What's left is simply connected and looks to me like it is homeomorhic to a ball.
 
  • #3
Yes, slice out a disk. A torus is a surface so it hollow? A ball is a solid. The torus still has a hole in it. How can it be homeomorphic to a ball?

I'd say it is homeomorphic to a proper torous which is homeomorphic to what?
 
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  • #4
What is the boundary of a torus excluding a disc?
 
  • #5
What is it homeorphic to? Infinitely many things, obviously. But I don't immediately see them as being interesting. Now, what is it homotopic to, there is an interesting question.

The boundary of a torus excluding a (closed) disc is obvious, surely. What do you think happens to an object without a boundary if we remove something like a disc?
 

1. What is a Torus Excluding Disc?

A Torus Excluding Disc is a mathematical shape that is created by taking a torus (doughnut shape) and removing a disc from the center of the torus, leaving a hole. This creates a boundary between the inside and outside of the torus.

2. What is the boundary of RP^2 X RP^2?

The boundary of RP^2 X RP^2 is a Torus Excluding Disc. This means that the shape is a product of two real projective planes (RP^2), with a boundary that is a torus with a disc removed from the center.

3. How is the Torus Excluding Disc related to topology?

The Torus Excluding Disc is a topological space, meaning it is a mathematical object that can be studied using topology. Topology is a branch of mathematics that focuses on the study of geometric properties that are preserved under continuous deformations. The Torus Excluding Disc is a common object of study in topology due to its interesting shape and properties.

4. What are some real-world applications of the Torus Excluding Disc?

The Torus Excluding Disc has many real-world applications, particularly in the fields of physics and engineering. It is used to model magnetic fields and fluid dynamics, as well as in computer graphics and 3D printing. It also has applications in knot theory and the study of three-dimensional manifolds.

5. How is the Torus Excluding Disc different from a regular torus?

The main difference between a Torus Excluding Disc and a regular torus is the presence of a boundary. A regular torus has no boundary, while the Torus Excluding Disc has a boundary that is a torus with a disc removed from the center. This difference leads to different properties and behaviors in the two shapes, making the Torus Excluding Disc a unique and interesting object of study in mathematics and science.

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