Solution to the September 2018 Figuring Physics

Physics 215 B QFT Winter 2018 Assignment

(a) Consider scattering of an electron (e−) and a positron (e) into e−e+ (so a = b in the notation above). We wish to consider the contribution to the imaginary part of the amplitude for this process which is proportional to QeQ 2 μ where Qe and Qμ are the electric charges of the electron and muon (which are in fact numerically equal but never mind that). Draw the relevant Feynman diagram, and ...

Physics 215 B QFT Winter 2018

Physics 215 B QFT Winter 2018 Assignment 2 – Solutions

Physics 215 B QFT Winter 2018 Assignment 1 – Solutions

(a) Show that the (non-relativistic) mass parameter m can be eliminated by a multiplicative redefinition of the field r or of the time t. As a result, convince yourself that the physics of interest here should only depend on the combination mλ. Show that the coupling mλ is dimensionless: [mλ] = 0. As before in 0 + 1 dimensions, demanding that [Skinetic] = 0 = 1 − 2 + 2[r] implies [ √ mr] = 1 2 ...

Physics 215 B QFT Winter 2018 Assignment 6 – Solutions

n e−βEn 〈n| T O(x)O†(0) |n〉 . Here Zβ ≡ tre−βH is the thermal partition function. Check that the zero temperature (β →∞) limit reproduces our previous result. Assume that O = O† if you wish. The idea is again to insert a resolution of the identity in between the operators. All the steps as for the vacuum correlators go through, the only difference being that instead of arriving at a sum of squa...