As I understand it, the axion $a$ originates from the spontaenous symmetry breaking of $U(1)_{PQ}$. This symmetry being anomalous, and because of the QCD vacuum structure, a non vanishing term like $\frac{a}{f_a}Tr( G \tilde{G})$ is included in the Lagrangian, where $G$ is the gluon field strenght. This determines the axion couplings to gluons. Talking about a coupling to photons would mean to consider a term like $\frac{a}{f_a} F \tilde{F}$, where $F$ is the QED field strenght. I thought a term like $ F \tilde{F}$ could be expressed as a vanishing total derivative, unlike $Tr( G \tilde{G})$, so why are we talking about axion couplings to photons ?
Subscribe to:
Post Comments (Atom)
-
Why can't we use fissions products for electricity production ? As far has I know fissions products from current nuclear power plants cr...
-
How can we know the order of a Feynman diagram just from the pictorial representation? Is it the number of vertices divided by 2? For exampl...
-
As the title says. It is common sense that sharp things cut, but how do they work at the atomical level? Answer For organic matter, such a...
-
This image from NASA illustrates drag coefficients for several shapes: It is generally accepted that some variation of the teardrop/airfoil...
-
Problem Statement: Imagine a spherical ball is dropped from a height $h$, into a liquid. What is the maximum average height of the displaced...
-
In most books (like Cardy's) relations between critical exponents and scaling dimensions are given, for example $$ \alpha = 2-d/y_t, \;\...
-
I have been studying scattering theory in Sakurai's quantum mechanics. The phase shift in scattering theory has been a major conceptual ...
No comments:
Post a Comment