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dyn
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Hi. I am just starting to self-study QFT. Have been looking at the non-relativistic case of particles in a box. Have come across creation operators in the occupation number representation which create a particle in specific momentum state. But I thought in a rigid box there are no momentum eigenstates so how can a particle be created in a specific momentum state ?
Also when describing a state in position coordinates which is done by taking the inverse Fourier transform of the state in momentum coordinates the integral is replaced by a sum as the momentum is quantized. I have never seen this before in QM. Is it sometimes assumed or ignored or should it always be written with a sum if the momentum is discrete ?
Thanks
Also when describing a state in position coordinates which is done by taking the inverse Fourier transform of the state in momentum coordinates the integral is replaced by a sum as the momentum is quantized. I have never seen this before in QM. Is it sometimes assumed or ignored or should it always be written with a sum if the momentum is discrete ?
Thanks