Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2011/paper-2/11/a/ii/solution

The curl of a gradient vanishes because the mixed second partial derivatives of the smooth function agree. Therefore everywhere, and
Unlike part (i), this integrand does not involve the problematic auxiliary field.

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