Fundamental Group of Genus 2 Surface

In summary, the fundamental group of the two-holed torus can be computed by removing the interior of a small disk from each torus and identifying the boundaries. This can also be approached by considering the connected sum of two tori, which results in the same fundamental group of $\mathbb{Z} \times \mathbb{Z}$.
  • #1
jgens
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Homework Statement



Given two tori, the two-holed torus can be formed by removing the interior of a small disk from each and identifying the boundaries. Compute the fundamental group of the two torus.

Homework Equations



[tex]\pi_1(T^2) = \mathbb{Z} \times \mathbb{Z}[/tex]

The van Kampen Theorem

The Attempt at a Solution



So, I know the standard way of tackling this problem, by decomposing the torus into a fundamental polygon and applying van Kampen's Theorem from there. However, I was wondering if there was some way to tackle the problem which appealed more to the definition of the connected sum, rather than the fundamental polygon.

For example, since the disk is homotopy equivalent to a point, would we obtain a homotopy equivalent structure by simply removing a point from each torus and identifying these points?
 
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  • #2
If so, then would the fundamental group be that of a connected sum of two tori, i.e. $\pi_1(T^2 \# T^2) = \mathbb{Z} \times \mathbb{Z}$? I am looking for any insight on this approach, and whether or not it is valid. Thanks!
 

FAQ: Fundamental Group of Genus 2 Surface

1. What is the Fundamental Group of Genus 2 Surface?

The Fundamental Group of Genus 2 Surface refers to the group of all possible closed loops on a surface with two holes, also known as a genus 2 surface. It is denoted by π1(Sg), where Sg represents the genus 2 surface.

2. How is the Fundamental Group of Genus 2 Surface calculated?

The Fundamental Group of Genus 2 Surface can be calculated using the Van Kampen theorem, which states that the fundamental group of a space is the amalgamated free product of the fundamental groups of its overlapping subspaces. In simpler terms, it involves breaking down the surface into smaller, simpler shapes and combining their fundamental groups to determine the overall group.

3. What are the applications of the Fundamental Group of Genus 2 Surface?

The Fundamental Group of Genus 2 Surface has many applications in topology, geometry, and physics. It is used to classify surfaces and understand their properties, such as orientability and curvature. It also has applications in knot theory and the study of 3-dimensional manifolds.

4. Can the Fundamental Group of Genus 2 Surface be visualized?

Yes, the Fundamental Group of Genus 2 Surface can be visualized using a fundamental polygon. This is a polygon with edges labeled by generators of the fundamental group, and vertices labeled by relations between these generators. By identifying and gluing the edges of this polygon, we can construct the surface and visualize its fundamental group.

5. How is the Fundamental Group of Genus 2 Surface related to other fundamental groups?

The Fundamental Group of Genus 2 Surface is a special case of the more general concept of fundamental group. It can also be related to the fundamental group of a sphere with g handles, which is equivalent to the fundamental group of a genus g surface. Additionally, the Fundamental Group of Genus 2 Surface is a subgroup of the fundamental group of any higher genus surface.

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