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MathGroup Archive 1997

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Possible problem with dimensions in matrix products

  • To: mathgroup at
  • Subject: [mg9211] Possible problem with dimensions in matrix products
  • From: slater at (Paul Slater)
  • Date: Tue, 21 Oct 1997 02:03:25 -0400
  • Sender: owner-wri-mathgroup at

I have two 4-vectors (x and y) and a 4 x 4 matrix (Z). I want to compute
x.Z.y, giving me a scalar. If I assign numerical values to the (three)
parameters in x, y and Z, I do get a scalar.
However, if I do not, then MATHEMATICA tells me that the product x.Z.y
is a 3-vector (!!!!)

The entries of the matrix and vectors are complex numbers.

Paul Slater

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