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Coordinate tetrads

  1. Dec 19, 2012 #1
    Dear Friends
    Is there any coordinate tetrad in spacetime except Cartesian basis ?
    since tetrad basis should be orthogonal (( In Lorentzian description ))and the only orthogonal basis is Cartesian ( the metric is (+1,-1,-1,-1 ) but in any other coordinate basis like Spherical metric is ( +1,-1,-r,-rsino ) and they aren't coordiante tetrad .
     
  2. jcsd
  3. Dec 19, 2012 #2
    The tetrad refers to the coordinate basis vectors, rather than the coordinates. The 4 coordinate basis vectors for Spherical coordinates are all orthogonal to one another, as are the coordinate basis vectors for cylindrical coordinates. But, in cylindrical and spherical coordinates, some of the 3 spatial coordinate basis vectors vary with spatial location.
     
  4. Dec 19, 2012 #3
    I know that but i mean are the only holonomic tetrad basis Cartesian basis ?
    unit vector basis in spherical coordinate are tetrads but coordiante basis isn't .and the relations between tetrads and basis coordiante are :
    e[itex]_{r}[/itex]=∂[itex]_{r}[/itex]
    e[itex]_{\theta}[/itex]=[itex]\frac{1}{r}[/itex]∂[itex]_{\theta}[/itex]
    e[itex]_{\varphi}[/itex]=[itex]\frac{1}{rsin\varphi}[/itex]∂[itex]_{\varphi}[/itex]
    e[itex]_{0}[/itex]=∂[itex]_{r}[/itex]=[itex]\frac{∂}{∂t}[/itex]
    and we can see those unit vectors have non vanishing Lie's bracket (( so they are anholonomic or non coordiante basis ))
    so i thought the cartecian basis are the only the coordinate tetrads (( or holonomic tetrads ))
     
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