Recent content by sfn17

Hello, I am often designing math exams for students of engineering. What I ask is the following: Can I choose any real 3x3 symmetric matrix with positive eigenvalues as a realistic matrix of inertia? Possibly, there are secret connections between the off-diagonal elements (if not zero)...

Yes, this is right. There is some more to read in a math forum: http://math.stackexchange.com/questions/166244/determinant-of-an-n-times-n-complex-matrix-as-an-2n-times-2n-real-determinan

Some Fierz reshuffling of indices seems to be useful. I found for myself the following identity (not confirmed!): \epsilon_{\kappa\lambda\mu\nu}g_{\sigma\tau} -\epsilon_{\kappa\lambda\tau\nu}g_{\sigma\mu}= \epsilon_{\mu\tau\lambda\nu}g_{\sigma\kappa}...

Oh yes, you're right! Thank you very much! :smile: I was lost in the forest of TeX...

I'm preparing a little sketch on the irreps of the Poincaré group according to Wigner's classification. Unfortunately, this subject seems to be not too popular in the textbooks and in review articles. No author whom I found describes clearly and correctly the structure of the little group of the...