Photons, as far as we know, don't decay to anything. Several fundamental quanta are thought to be the same, in particular, electrons and protons. There's an experiment looking for proton decay which would have expected to find one by now if it ever happens, and they haven't. All the others are...
I'll see what I can do...
Given the definition of the S matrix:
S=\sum_{x=0}^{\infty}\frac{(-i)^{n}}{n!}\int...\int d^{4}x_{1}...d^{4}x_{n}T\{H_{I}(x_{1})...H_{I}(x_{n})\}
and the interaction Hamiltonian being (for QED):
H_{I}(x)=-eN\{\overline{\psi}(x)\gamma_{i}A^{i}(x)\psi(x)\}
The...
Thanks arkajad, you are clearly a patient teacher. Spelled out explicitly, the dotted index rule makes perfect sense and it seems that as usual, there's a subset of authors who simply can't be bothered to express their derivations rigorously. I'm displaying my ignorance once again, though in my...
I thought I'd stick my oar in here since I also find these problems in general extremely challenging.
For one, I've never even seen these 'dotted indices' before. The author of my QFT textbook doesn't use them.
In reference to arkajad's second-to-last post: What is the reasoning behind moving...
I am not sure that spatial quantisation is really the right way of looking at it. My understanding is that quantisation of a field implies that propagating disturbances in the field, i.e. particles, come in discrete lumps, i.e. you can't have probability distribution of observed field strength...
Nobody?
If it helps, the difficulty I have is that in the first resultant expression, the indices on the second gamma and the first A don't match. As far as I knew, this didn't mean anything as summation is over repeated indices.
Ok, suppose we freeze you cryogenically and put you on a train. When the train moves, do you move?
Ridiculous example. But that shows what I'm trying to express here, which is that the question you asked is not a useful one. You've tried to project human assumptions onto a system which does not...
I have in front of me Quantum Field Theory, Mandl & Shaw. Chapter 7 deals with the theoretical basis of Feynman Diagrams using the Dyson-Wick formalism.
The chapter begins with applying Wick's Theorem to produce six S-Matrix components with a variety of no-equal-time contractions. It then...
I find it fiendishly difficult to get to sleep if there's any disturbance around me, but once I'm gone, I'm gone. I then wake up at sunrise whether or not I want to.
I was stating this in the context of what the Higgs does, as opposed to what the Higgs does not - the point being that being responsible for certain mass terms in certain particle interactions does not in any way imply that the Higgs is responsible for transmitting the gravitational force; and...
The quoted identity is for a general method comprising r fields - the case I'm applying it to is the one where the fields are A (r=1) and At (r=2). For r=1 the field is a three-component vector, and there is no escaping that.
The bar is 3-vector notation. Are you familiar with this method? The field A and the derivatives of the field are treated as being independent of one another, so the term you quoted from me and the term you equated it to do not infer one another.
RE Post #13: The piece you quoted from me is the...
It's a QFT problem so it's four-dimensional, but the four-vector \tilde{A} is decomposed into \overline{A} + A_{t}\overline{e}_{0}. The Lagrangian formulation of electromagnetism in the method I've been given is to apply the euler-lagrange equation to each of these components seperately.
Edit...