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I have to calculate symmetry factors for the following feynman diagrams for my qft class, and would be hugely grateful if anyone could point out any mistakes (I'm sure there are lots!) that I've made.

http://picasaweb.google.com/jessicagreerstanley/Physics#5259179071440262450" [Broken]

And here are my answers:

(a) Symmetry factor, S = 2^3 = 8. Interchange of 2 pairs of equivalent lines and swapping the ends of the bubble line

(b) S = 2^7 = 128. Swapping 5 pairs of equivalent lines, 2 pairs of equivalent vertices.

(c) S = 2 x 4! = 48. Swapping the two vertices, and interchanging the 4 internal lines.

(d) S = 2^4 = 16. Swapping the two internal lines, interchanging the ends of the two bubbles, interchanging the two vertices.

(e) S = 2^3 = 8. Swapping the two vertices attached to the external lines, interchanging the ends of the bubble, swapping the lines on the top of the bigger loop.

(f) This one has me very confused...

(g) S = 2^6 = 64. Exchanging 4 pairs of equivalent lines, swapping one pair of equivalent vertices, interchanging the ends of the bubble.

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# Symmetry factors for feynman diagrams

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