Algebraic Topology: Showing Cone(L(X,x)) is Homeomorphic to P(X,x)

In summary: P(X,x) In summary, The space Cone(L(X,x)) is homeomorphic to P(X,x) where L(X,x) = {loops in X base point x} and P(X,x) = {paths in X base point x}
  • #1
nughret
45
0
I am trying to show that the space Cone(L(X,x)) is homeomorphic to P(X,x)
where L(X,x) = {loops in X base point x} and
P(X,x) = {paths in X base point x}

I firstly considered (L(X,x) x I) and tried to find a surjective map to P(X,x) that would quotient out right but i couldn't seem to find it. For example i considered
(l,t) -> p where p is the path such that p(1)=l(t) and they agree naturally before
i.e. F((l,t))(s) = l(ts)

I was wondering if anyone could point me roughly the right way or just chip in with their own thoughts
 
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  • #2
Why should this be true?

If I take the simplest case X={x} then L(X,x)=P(X,x)={the constant path at x}. Cone(L(X,x)) is just [0,1] which is not homeomorphic to a point.
 
  • #3
Yes your example is clear and i to was running into similar problems when trying to consider where to map (c(x),t) for different values of t on a general space. The task was set by someone who is knowledgeable about the subject so maybe if instead of the cone we consider

(Cone(L(X,x)))/~ where (c(x),a) ~ (c(x),b), c(x) is the function with constat value x. This would then clear up the problem of how to map the constant function and we would have F(c(x),t) = F(l,0) = c(x).(l any loop)

Then the problem remains the same, but if we consider the above identification made, it would appear natural to consider a method similar to my first post however i cannot manage to tweak it correctly
 
  • #4
Consider decomposing a path,p, into a loop,l, and a non looping part,n, and a time,t, at the point where we connect these paths: p = l (+t) n
where for two paths a,b such that a(1)=b(0) we have (for t not equal 1,0)
(a (+t) b) (s) = a(s/t) , 0<s<t
b((s-t)/(1-t)) , t<s<1
and (a (+0) b) (s) = a(0)
(a (+1) b) (s) = a(s)

Motivitated by this define the map from F: (L(X,x))x(N(X,x))xI -> P(X,x)
where N(X,x) is the set of non looping maps n belongs to N(X,x) => n(t) is not equal to n(0)=x for all t>0 (strictly)
Then F(l,t,n) = F(l',t',n') => l (+t) n = l' (+t') n' =>
(t and t' not equal to 0)
Then WlOG assume t is greater than or equal to t' then if t is strictly greater we would have that one path took the value x at this time whilst the other didn't a contradiction => t = t'
and it then follows l = l' , n = n'
Now let t = 0 , then F(l,0,n) = F(l',t',n') then it is clear t' =0 , we have no condition on l,n

Hence we can find a bijection from Cone(L(X,x)xN(X,x)) to P(X,x) as i don't wish to consider the different possible topologies let us assume this is a continuous map.
Then if the original statement (or its revised version) was true then we must have that
Cone(L(X,x)xN(X,x)) is homeomorphic to (Cone(L(X,x)))/~
Do the above constuctions appear correct?
 
  • #5
Re reading i see that we must also make the identification (l,1,n) ~' (l,1,n')
But then we will just get ; Cone(L(X,x)xN(X,x))/~'
 

1. What is algebraic topology?

Algebraic topology is a branch of mathematics that studies the properties of spaces and objects that are preserved under continuous deformations, such as stretching and twisting, but not tearing or gluing. It uses algebraic tools to study topological spaces and their properties.

2. What is a cone in algebraic topology?

In algebraic topology, a cone is a geometric structure formed by taking a given space and adding a new point, called the apex, and connecting every point in the original space to the apex with a straight line segment. This creates a conical shape and is used to study the properties of spaces and their deformations.

3. How is a cone homeomorphic to the space it is based on?

A cone is homeomorphic to the space it is based on because it is a continuous deformation of the original space. This means that the cone and the original space have the same topological properties, such as connectedness and compactness, and can be transformed into each other without tearing or gluing.

4. What is the significance of showing that Cone(L(X,x)) is homeomorphic to P(X,x)?

By showing that Cone(L(X,x)) is homeomorphic to P(X,x), we can prove that the cone can be transformed into the original space without changing its topological properties. This is important in algebraic topology as it allows us to study the properties of spaces by using simpler and more manageable structures, such as cones.

5. How is algebraic topology used in other fields of science?

Algebraic topology has applications in various fields of science, including physics, computer science, and biology. It is used to study the properties of spaces in a way that is independent of their specific geometric or topological representation. This allows for the analysis of complex systems and the discovery of patterns and relationships between different objects or spaces.

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