Is it necessary for a traceless matrix to be even order?
Am working on Dirac equation and I wonder why gamma matrices should be even order and 4 by 4?

Is it necessary for a traceless matrix to be even order?
Am working on Dirac equation and I wonder why gamma matrices should be even order and 4 by 4?
No. Think of it this way: The trace is the sum of the eigenvalues. There's no necessity for evenness in order to have a zero eigenvalue sum. As a simple example, consider a thirdorder dynamical system with a symmetrical pair of eigenmodes (real, with values that are algebraic inverses), and a third eigenmode at zero.
Last edited by tk421; 01022014 at 06:09 PM. Reason: corrected wording
Simpler, perhaps, but to my tastes, less informative than it could be. The trace is certainly the sum of the main diagonal components, so it's easy enough to see how one could come up with an infinite variety of combinations that sum to zero. I just prefer physicallybased examples when possible, hence the connection to the eigenvalue sum. You say tomato, I say banana.
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