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)
Understanding Stagnation point in pitot fluid
What is stagnation point in fluid mechanics. At the open end of the pitot tube the velocity of the fluid becomes zero.But that should result...
-
I am making a simple little program that needs to simulate a physics concept. However, I am not exactly sure how the physics concept actuall...
-
The gravitation formula says $$F = \frac{G m_1 m_2}{r^2} \, ,$$ so if the mass of a bob increases then the torque on it should also increase...
-
Sorry if this question is a bit broad but I can't find any info on this by just searching. The equation q = neAL where L is the length o...
-
I have an hydrogenic atom, knowing that its ground-state wavefunction has the standard form $$ \psi = A e^{-\beta r} $$ with $A = \frac{\bet...
-
I stand up and I look at two parallel railroad tracks. I find that converge away from me. Why? Can someone explain me why parallel lines s...
-
This image from NASA illustrates drag coefficients for several shapes: It is generally accepted that some variation of the teardrop/airfoil...
-
Sometimes I am born in silence, Other times, no. I am unseen, But I make my presence known. In time, I fade without a trace. I harm no one, ...
No comments:
Post a Comment