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## Main Question or Discussion Point

Hi can anyone explain how to derive an expression for the Dirac Hamiltonian, I thought the procedure was to use [itex] \mathcal{H}= i\psi^{\dagger}\Pi -\mathcal{L}[/itex], but in these papers the have derived two different forms of the Dirac equation [itex] H=\int d^{3}x \psi^{\dagger}i\partial_{0}\psi[/itex]http://arxiv.org/abs/hep-ph/9905242 and [itex] H=\int d^{3}x -\psi^{\dagger}i\partial_{0}\psi[/itex]http://arxiv.org/abs/hep-ph/0003045v3 yet both use the (+,---) metric signature.

a) does anyone know how to derive a Hamiltonian that only contains the [itex] \partial_0[/itex] operator?

b) is it possible to have this - sign in place using the same metric tensor convention?

a) does anyone know how to derive a Hamiltonian that only contains the [itex] \partial_0[/itex] operator?

b) is it possible to have this - sign in place using the same metric tensor convention?