Saturday, 8 December 2018

Propagator of Chern-Simons Abelian gauge theory


I need to compute the "topologically massive photon" propagator.



I've started with :


$$ \mathcal{L}=-\frac{1}{4}F_{\mu\nu}F^{\mu\nu} + \frac{\mu}{4}\epsilon^{\mu\nu\lambda}A_\mu\partial_\nu A_\lambda $$ $$ =A_\mu\underbrace{[\frac{1}{2}g^{\mu\lambda}\partial^2+\frac{\mu}{2}\epsilon^{\mu\nu\lambda}\partial_\nu]}_{(\Delta^{-1})^{\mu\lambda}}A_{\lambda} $$


So how can I invert The under braced part which will yield the topologically massive photon propagator?



Answer



The following is a rough calculation. If the operator,


$$\triangle^{\mu\lambda} = \eta^{\mu \lambda} \partial^2 + \mu \epsilon^{\mu\nu\lambda}\partial_{\nu},$$ is the one you wish to invert, then we must solve the differential equation


$$ \triangle^{\mu\lambda} G = \left[\eta^{\mu \lambda} \partial^2 + \mu \epsilon^{\mu\nu\lambda}\partial_{\nu} \right] G = -i\delta^{(4)}(x-y)$$


where $(-i)$ is by convention. I think the momentum space equivalent is


$$\left[ \eta^{\mu \lambda}p^2 + i\mu \epsilon^{\mu\nu\lambda}p_{\nu}\right]\hat{G} = -i\mathrm{e}^{-ip\cdot y}.$$


To obtain $\hat{G}$ in position/physical space, you must perform an inverse fourier transform. Let me know what you get, I'm curious!



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