Past exam of the mathematics course of the University of Cambridge 2021 iii Paper 307 2 Solution 2026-09-28
Let be a chiral gauge parameter. One consistent Abelian supergauge transformation convention isfor which is invariant. Wess-Zumino gauge uses the nonordinary components of to remove the superfluous scalar and spinor components of , leaving the photon, gauginos, complex scalar, and real auxiliary field of the two-dimensional vector multiplet. Ordinary gauge transformations remain.
Define the field-strength multiplet, up to conventional normalization, byGauge invariance follows because chirality, antichirality, , and annihilate the variation of . The same identities giveso is a twisted chiral superfield. The Fayet–Iliopoulos term is a twisted F-term. In the standard axial convention its measure has axial charge , so invariance requiresReversing all axial-charge conventions reverses both signs but leaves this statement unchanged: the field and measure have opposite charges.
The charged matter fermions are chiral with respect to the axial symmetry. In a background with gauge flux, their functional measure has the two-dimensional axial anomalyup to orientation and current normalization. Equivalently, a Fujikawa transformation multiplies the torus path integral by a phase proportional to . Since the background flux may be nonzero, the continuous axial survives quantum mechanically precisely when