Past exam of the mathematics course of the University of Cambridge 2008 ii Paper 3 32D Solution Created 2026-09-24 Updated 2026-09-24
Past exam of the mathematics course of the University of Cambridge 2012 iii Paper 45 1 Solution 2026-10-07
Write and . In the Jacobi-consistent convention just fixed,Applying the commutator product rule twice givesHere produces the constant term; moving the to the right accounts for it. ConsequentlyThus the physically consistent numerical coefficients areIf one mechanically retains the literal positive-sign column transformation instead, the coefficient tuple would be . It cannot describe a unitary multiplet with the supplied rotation algebra, by the explicit Jacobi counterexample in part (a).
Take the spin-zero Clifford vacuum , normalized to one and annihilated by the two annihilation charges. This is a lowest Fock state of a positive-mass representation, not a zero-energy vacuum annihilated by every charge. For the first one-charge state,The ladder commutators are , , , . Therefore these two states are the pair. A phase choice makes the usual positive ladder coefficient hold.
Raising the dotted index only changes the oscillator basis by the unitary antisymmetric epsilon matrix, so . Since ,The positive convention would formally label this state with while acts nontrivially on it, contradicting the highest-weight ladder rule. This supplies an independent state-level check of the needed sign correction.
The two-charge state is a rotation singlet. Indeed, using and , the product rule gives for every : only the sum of the two diagonal spinor coefficients survives, and their trace is zero. Hence the requested commutators and quantum numbers areIts squared norm is before multiplication by , by the two oscillator anticommutators.
The spin-zero massive N=1 supermultiplet therefore consists of , , and . Their spins are , all with the same mass . Starting with an even vacuum, the two spin-zero states are bosonic and the two one-charge states fermionic. They are the two real scalar degrees of freedom and the two on-shell fermion polarizations of a massive chiral multiplet. Any product of three creation charges repeats an index and vanishes; annihilation charges reduce to these four states by the canonical anticommutation relations. There are exactly four independent states.
Past exam of the mathematics course of the University of Cambridge 2012 iii Paper 45 2 g Solution Created 2026-10-03 Updated 2026-10-07
The remaining non-derivative component term in the Lagrangian is the Yukawa interactionEquivalently the interaction Hamiltonian has the opposite displayed sign. The first term is the two-component fermion mass, and the second its scalar-fermion interaction. A phase redefinition of makes the mass coefficient nonnegative, so the physical Weyl spinor mass isIt is again independent of , the choice of root and any sign of a real . This distinguishes the complex bilinear coefficient from the nonnegative physical mass. In the pure-linear supersymmetry-breaking branch , the fermion is the massless Goldstino.