Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2015/iii/paper-48/2/e/solution

In four spacetime dimensions, canonical mass dimensions are
Since a Lagrangian has mass dimension four, a power-counting renormalizable quantum field theory requires and , with couplings of nonnegative mass dimension. Up to a positive constant kinetic matrix, field redefinitions and Kähler transformations, the renormalizable ungauged kinetic term is canonical. Holomorphic additions to integrate to a boundary term. The general renormalizable superpotential is
The coefficients have dimensions , respectively; and may be taken symmetric. The constant does not affect a global chiral theory. Higher polynomial degree in , nontrivial higher-degree terms in , or higher-derivative interactions are nonrenormalizable interactions and can instead be retained in an effective field theory.

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