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Nomenclature question

  1. Dec 8, 2009 #1
    Hello everyone,

    I have a question about nomenclature and it may be a bit more than simple nomenclature as I am not quite sure I understand it:

    So, I am reading a paper and going through it very slowly as it is quite intense. But one of the line is as follows:

    Suppose the transformation s maps a point p to the point s(p). Let u = s - I be the displacement field associated with the transformation s.

    I am confused as to what s - I represents. The subtracting of the identity from a transformation seems strange to me.

    I always thought the displacement field can be simply represented for each particle by associating a vector with each particle...

    I hope someone can clarify this doubt for me.

    Many thanks,

  2. jcsd
  3. Dec 8, 2009 #2
    I guess, they try to describe the vector by saying the vector is defined by its starting point and end point [itex]u = (x_2-x_1, y_2-y_1)[/itex] and [itex] s((x_1,y_1)) = (x_2,y_2)[/itex].

    They probably used the notation [itex](s-I)(p)[/itex]
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