path integral

  1. S

    A Does Feynman's path integral ignore alternative histories?

    Summary: Does Richard Feynman's multiple histories ignore alternative histories? Did Richard Feynman's multiple histories (https://en.wikipedia.org/wiki/Multiple_histories) ignore the existence of other alternarive histories or paths? I ask this referring to this comment from this page...
  2. ErikZorkin

    I Counterpart of Feynman integral in de Broglie-Bohm theory

    I am looking for good references / clarifications on the subject. First of all, my question is concerned only with mathematical formulation of something that sort of plays the role of the Feynman path integral of the "standard" QFT. It is not concerned with the physical or philosophical...
  3. H

    A How to evaluate path integrals numerically?

    Since we only know Gaussian integration, could one get Green's function numerically with interacting action. Usual perturbation theory is tedious and limited, could one get high accurate result with PC beyond perturbation?
  4. BookWei

    I The Principle of Least Action

    Hello, When we applying the principle of least action, we require ##\delta S=0##, which corresponding to the action S being an extremum. I am just wondering why do we say that the action is a minimum instead of a maximum for a physical path? Can I use the path integral to explain this problem...
  5. rocdoc

    I A Proof of Kaku (8.18).

    In the following there is a proof, for positive values of ##a## only, of (8.18) of Kaku, reference 1, I quote' $$\int_{-\infty}^\infty~\mathrm{d}p~e^{iap^2+ibp}=\sqrt \frac{i\pi}{a}e^{-ib^2/4a}~~~~~~~~~~~~~(8.18)$$ '. Kaku says this result can be proved by completing the square. $$iap^2+ibp =...
  6. C

    Inelastic collision and the sum of internal forces

    1. Homework Statement Suppose I have a system which contains two bodies m1 and m2 with initial velocities v1 and v2 , respecitvely. they hurl toward each other and make an inelastic collision. such that they are now one body of mass m1 + m2 I know that the difference in momentum is...
  7. needved

    A Help to understand the derivation of the solution of this equation

    Please, help here people. Im reading this article Wave Optics in Gravitational Lensing (T. T. Nakamura, 1999) . In the article start work with \begin{equation} (\nabla ^2 +\omega)\tilde\phi = 4\omega^2U\tilde\phi \end{equation} where $$\tilde\phi = F(\vec r)\tilde\phi_{0}(r)$$. Using...
  8. Tbonewillsone

    Deriving an influence functional is deriving me mad! (Help)

    1. Homework Statement I am attempting to derive Caldeira-Leggett's influence functional found in their paper "Path Integral Approach To Quantum Brownian Motion". If you find my following statements confusing, then pages 16-18 of http://web.science.uu.nl/itf/Teaching/2006/MxWakker.pdf show the...
  9. J

    I Difference between statistical and dynamical properties

    Hi All, What are the main differences between statistical and dynamics properties in physics? Could you please explain the difference for problems in both classical and quantum mechanics. For instance, path integral molecular dynamics is supposed to give statistical properties of a quantum...
  10. B

    Spherical coordinates path integral and stokes theorem

    1. Homework Statement 2. Homework Equations The path integral equation, Stokes Theorem, the curl 3. The Attempt at a Solution sorry to put it in like this but it seemed easier than typing it all out. I have a couple of questions regarding this problem that I hope can be answered...
  11. nikosbak

    3-point function QFT

    1. Homework Statement I'm working on path integrals for fermions and I came across an exercise that ask to compute the three point functions , one of that is the: $$<0|J^{\mu}(x_1)J^{\nu}(x_2)J^{\rho}(x_3)|0> $$ where $$J^{\mu}$$ is the current $$J^{\mu}=\bar{\psi}\gamma^{\mu}\psi$$. ***Can...
  12. M

    Unitarity and locality on patgh integrals

    my question is this: you know than in feynman path integra, you integrate eiS/hbar along all the fields. you also know that S is real and that it is the integral of local functions (fields and derivatives of fields). you also know that path integral generates an unitary and local...
  13. Xiaomin Chu

    Path integral and discontinuous paths

    Somebody asked about this but that thread was closed very soon. In physics, discontinuous paths breaks locality so they must be 0; but mathematically, they causes some problems. Discontinuous functions must not be differentiable, so it's impossible to calculate the action over that path. However...
  14. S

    Action corresponding to photon emission

    Hi I am trying to write the probability of photon emission due to transition of electron in feynman's path integral formulation. I am stuck trying to figure out the action corresponding to the photon emission. Would anyone shed some light on this? Thanks
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