# Compare three tangent vectors constructed via parallel transport, exponential map and Jacobi vector field respectively

Given a Riemannian manifold $X$, a point $x\in X$ and $u,v\in T_xX$, I wanted to compare the following three vectors in $T_{\exp_x(v)}X$.

$u_1=$ The parallel transport of $u$ along the geodesic $\exp_x(tv)$ at $t=1$;

$u_2=(d\exp_x)|_{\exp_x(v)}u$, the push-forward of $u$ under the exponential map $T_xX\rightarrow X$ at $\exp_x(v)$;

$u_3$: Consider the vector field $v_\tau$ along the geodesic $\exp_x(\tau u)$ by parallel transport of $v$, then take the geodesic $\gamma_\tau(t)$ determined by $v_\tau$, thus we have a family of geodesics. Now take the Jacobi vector field at $t=1$ to be $u_3$, i.e. $\frac{d}{d\tau}|_{\tau=0}(\gamma_\tau(1))$.

My question is

Does $\sup\limits_{\|u\|=1}\|u_i-u_j\|^2\leq o(\|v\|^2)$ hold near $x$?

If it is not true in general, what conditions should one put on the metric to ensure this?

• Can you clarify the definition of $u_3$? What's $w$ and how is $u$ involved? – Anthony Carapetis Oct 19 '14 at 6:55
• @AnthonyCarapetis, sorry that was a typo, $w$ meant $u$. I just corrected it. – Xin Jin Oct 19 '14 at 15:52