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Ivancevic_Applied-Diff-Geom

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<strong>Applied</strong> Bundle <strong>Geom</strong>etry 735under U(1) R . Higher order perturbative corrections are absent. Instantonslead to new terms. The anomaly and the instanton action suggest thatF = i 12π A2 ln A2∞ Λ 2 + ∑( 4k ΛF k AA) 2 ,where the k’th term arises as a contribution of k instantons. A detailedcalculation of the k = 1 term indicates that F 1 ≠ 0. Also, corrections tothe classical formula 4.219 are related to the beta function, and for N =4 supersymmetric YM theory, whose beta function vanishes, the formula(4.219) is exact.k=14.14.4 QED With MatterFollowing the original SW approach [Seiberg and Witten (1994a); Seibergand Witten (1994b)], we first consider Abelian gauge theories with N = 2supersymmetry and charged matter hypermultiplets – that is, the N = 2analog of ordinary QED.The ‘photon’, A µ is accompanied by its N = 2 superpartners – twoneutral Weyl spinors λ and ψ that are often called ‘photinos’, and a complexneutral scalar a. They form an irreducible N = 2 representation that canbe decomposed as a sum of two N = 1 representations: a and ψ are ina chiral representation, A, while A µ and λ are in a vector representation,W α .We take the charged fields, the ‘electrons’, to consist of k hypermultipletsof electric charge one. Each hypermultiplet, for i = 1 . . . k, consists oftwo N = 1 chiral multiplets M i and ˜M i with opposite electric charge; suchan N = 1 chiral multiplet contains a Weyl fermion and a complex scalar.The renormalizable N = 2 invariant Lagrangian is described in an N =1 language by canonical kinetic terms and minimal gauge couplings for allthe fields as well as a superpotentialW = √ 2AM i ˜Mi + ∑ im i M i ˜Mi . (4.221)The first term in related by N = 2 supersymmetry to the gauge couplingand the second one leads to N = 2 invariant mass terms.The classical moduli space of the N = 2, SU(2) gauge theory isparametrized by u = 〈Tr( φ 2 )〉 where φ is a complex scalar field in theadjoint representation of the gauge group. For u ≠ 0 the gauge symmetryis broken to U(1). At u = 0 the space is singular and the gauge symmetry

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