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Ivancevic_Applied-Diff-Geom

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<strong>Applied</strong> Bundle <strong>Geom</strong>etry 751Φ. Breaking N = 2 down to N = 1, one can add a superpotential W =mTr(Φ 2 ) for the chiral multiplet. This gives a bare mass to Φ, reducing thetheory at low energies to a pure N = 1 gauge theory. The low energy theoryhas a Z 4 chiral symmetry. This theory is strongly believed to generate amass gap, with confinement of charge and spontaneous breaking of Z 4 toZ 2 . Furthermore, there is no vacuum degeneracy except what is producedby this symmetry breaking, so that there are precisely two vacuum states.How can this be mimicked in the low energy effective N = 2 theory?That theory has a moduli space M of quantum vacua. The massless spectrumat least semiclassically consists solely of the Abelian chiral multipletA of the unbroken U(1) subgroup of SU(2). If those are indeed the onlymassless particles, the effect in the low energy theory of turning on m canbe analyzed as follows. The operator Tr( Φ 2 ) is represented in the low energytheory by a chiral superfield U. Its first component is the scalar fieldu whose expectation value is〈u〉 = 〈Tr( φ 2 )〉,where φ is the θ = 0 component of the superfield Φ. This is a holomorphicfunction on the moduli space. At least for small m we should add to ourlow energy Lagrangian an effective superpotential W eff = mU.Turning on the superpotential mU would perhaps eliminate almost all ofthe vacua and in the surviving vacua give a mass to the scalar componentsof A. But if there are no extra degrees of freedom in the discussion, thegauge field in Awould remain massless. To get a mass for the gauge field,as is needed since the microscopic theory has a mass gap for m ≠ 0, oneneeds either(i) extra light gauge fields, giving a non–Abelian gauge theory and possiblestrong coupling effects, or(ii) light charged fields, making possible a Higgs mechanism.Thus we learn, as we did in discussing the monodromies, that somewhereon Mextra massless states must appear. The option (i) does not seemattractive, for reasons that we have already discussed. Instead we consideroption (ii), with the further proviso, from our earlier discussion, that thelight charged fields in question are monopoles and dyons.Near the point at which there are massless monopoles, the monopolescan be represented in an N = 1language by ordinary (local) chiral superfieldsMand ˜M, as long as we describe the gauge field by the dual to the

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