Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Covariant Derivatives

  1. May 24, 2009 #1
    I'm teaching myself about connections and came across something I am not completely sure about. The text I am using defines a connection as taking in two vector fields and outputting a vector field. However, later when discussing covariant derivatives along a curve I see this equation:

    D_t V(t) = \nabla_{\dot{\gamma}(t)} W,

    where V is a vector field along the curve [tex]\gamma[/tex], W is an extension field of V, [tex]\nabla[/tex] is the connection and D_t takes in a vector field along [tex]\gamma[/tex] and gives a vector field along [tex]\gamma[/tex].

    I understand that the left hand side is the value of the vector field D_t V at time t (a tangent vector at [tex]\gamma(t)[/tex]). However, the right hand side is confusing me since [tex]\dot{\gamma}(t)[/tex] is a tangent vector at [tex]\gamma(t)[/tex] and not a vector field. Since the value of a covariant derivative at a point p depends only on the value at p of the vector field we are differentiating along, is the right hand side the same as [tex](\nabla_X W) (\gamma(t))[/tex] where X is any vector field such that [tex]X(\gamma(t)) = \dot{\gamma}(t)[/tex]?

  2. jcsd
  3. May 24, 2009 #2


    User Avatar
    Science Advisor

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook