Fourier transform of vector potential

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SUMMARY

The discussion centers on the indefinite integral of the vector potential, specifically the expression $$\int{d^3x(\nabla^2A^{\mu}(x))e^{iq.x}}$$ as part of deriving the Rutherford scattering cross section from "Quarks and Leptons" by Halzen and Martin. Participants emphasize the necessity of using partial integration rather than vector calculus identities to simplify the integral. The key result derived is $$\int{d^3xA^{\mu}(x)(\nabla^2e^{iq.x})}$$, with the understanding that boundary terms vanish due to the fields approaching zero at infinity.

PREREQUISITES
  • Understanding of vector calculus identities, particularly the Laplacian operator.
  • Familiarity with the concept of partial integration in multiple dimensions.
  • Knowledge of quantum field theory, specifically the role of vector potentials.
  • Basic understanding of scattering theory and its mathematical formulations.
NEXT STEPS
  • Study the application of partial integration in quantum field theory calculations.
  • Explore the derivation of the Rutherford scattering cross section in detail.
  • Learn about the properties of vector potentials in quantum mechanics.
  • Investigate the implications of boundary conditions in field theory integrals.
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Students and researchers in quantum field theory, particularly those focusing on scattering processes, as well as physicists interested in the mathematical techniques used in theoretical physics.

Amith2006
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Homework Statement


I have question on doing the following indefinite integral:
$$\int{d^3x(\nabla^2A^{\mu}(x))e^{iq.x}}$$

Homework Equations


This is part of derivation for calculating the Rutherford scattering cross section from Quarks and Leptons by Halzen and Martin. This books gives the following result obtained by partial integration of the above integral:
$$\int{d^3xA^{\mu}(x)(\nabla^2e^{iq.x})}$$

The Attempt at a Solution


I tried to use the identity from vector calculus:
$$\nabla^2(\phi\psi) = \phi\nabla^2\psi + \psi\nabla^2\phi + 2\nabla\phi.\nabla\psi$$
But not sure how to get rid of the other terms.
Any help is most welcome.
 
Last edited:
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No, you need to use partial integration as mentioned by the authors and not vector identities. I suggest you start in one dimension and then see how it generalises. Also remember that the fields are assumed to go to zero at infinity such that the boundary terms from the partial integration vanishes.
 
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