# Tangent bundle

The triplet \left ( TM,M,\pi \right ) is a vector bundle called the tangent bundle TM such that M is its manifold basis, \pi : TM \rightarrow M the canonical projection. \left ( x^{i},y^{i} \right ) is a local coordinate system on a map \left ( \pi^{-1}(U),\varphi_{U} \right ).
x^{i} is the system of map coordinates \left ( U,\varphi \right ) of M and y^{i} are as
y= y^{i}\frac{\partial }{\partial x^{i}} , y \in T_{x}M .
Now if we take a new system of coordinates \left ( \tilde{x}^{i}, \tilde{y}^{i} \right )
on a map ( \pi^{-1}(V),\phi _{U} \right ) . \tilde{x}^{i} is the system of map coordinates \left ( V,\psi \right ) of M.
Then after the change of coordinates we have the following results :
( 1) \frac{\partial }{\partial \tilde{x}^{i}} = \frac{\partial x^{k}}{\partial \tilde{x}^{i}}\frac{\partial }{\partial x^{k}} .
(2) \tilde{y}^{j}= \frac{\partial x^{j}}{\partial \tilde{x}^{l}}y^{l}.

My question is this: It is clear from (1) that {x}^{i} depends \tilde{x}^{j} (and vice versa)
also {y}^{i} depends \tilde{y}^{j}. So \tilde{y}^{j} does it depend of {x}^{i} ?
What is the value then of \frac{\partial \tilde{y}^{j}}{\partial x^{i}} ?

In short, I seek the independence of variables \left ( x^{i},y^{i} \right ) and \left ( \tilde{x}^{i}, \tilde{y}^{i} \right ).

Fredrik
Staff Emeritus
Gold Member
Please put itex or tex tags around the LaTeX expressions. Use the preview feature to verify that they images look the way you intended. You need to refresh and resend after each preview (due to a bug).

Yes, use the features. Now, the whole point is that coordinates $x^i$ in a natural way coordinates on the tangent bundle. And normally this is how the tangent bundle is described. I am not sure from your post whether [itex]y^i[/tex] are the induced coordinates in this way, or "any coordinates", for instance referring to some selected "moving frame".

The triplet $$\left ( TM,M,\pi \right )$$ is a vector bundle called the tangent bundle $$TM$$ such that $$M$$ is its manifold basis, $$\pi : TM \rightarrow M$$ the canonical projection. $$\left ( x^{i},y^{i} \right )$$ is a local coordinate system on a map $$\left ( \pi^{-1}(U),\varphi_{U} \right )$$.
$$x^{i}$$ is the system of map coordinates $$\left ( U,\varphi \right )$$ of $$M$$ and $$y^{i}$$ are as
$$y= y^{i}\frac{\partial }{\partial x^{i}} , y \in T_{x}M$$ .
Now if we take a new system of coordinates $$\left ( \tilde{x}^{i}, \tilde{y}^{i} \right )$$
on a map $$( \pi^{-1}(V),\phi _{U} \right ),\tilde{x}^{i})$$ is the system of map coordinates $$\left ( V,\psi \right )$$ of $$M$$.
Then after the change of coordinates we have the following results :
(1) $$\frac{\partial }{\partial \tilde{x}^{i}} = \frac{\partial x^{k}}{\partial \tilde{x}^{i}}\frac{\partial }{\partial x^{k}}$$ .
(2) $$\tilde{y}^{j}= \frac{\partial x^{j}}{\partial \tilde{x}^{l}}y^{l}$$.

My question is this: It is clear from (1) that $${x}^{i}$$ depends $$\tilde{x}^{j}$$ (and vice versa)
also $${y}^{i}$$ depends $$\tilde{y}^{j}$$ So $$\tilde{y}^{j}$$ does it depend of $${x}^{i}$$ ?
What is the value then of $$\frac{\partial \tilde{y}^{j}}{\partial x^{i}}$$ ?

In short, I seek the independence of variables $$\left ( x^{i},y^{i} \right )$$ and $$\left ( \tilde{x}^{i}, \tilde{y}^{i} \right )$$