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Ivancevic_Applied-Diff-Geom

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<strong>Applied</strong> Bundle <strong>Geom</strong>etry 725needs to be expressed through a certain holomorphic function F = F(a),called a prepotential. Then the Coulomb–branch, low–energy, effective actionfor the 4D N = 2 SUSY YM vector multiplets can be described interms of an auxiliary Riemann surface (i.e., a complex curve) Σ, equippedwith a meromorphic 1–form dS. The required Riemann surface Σ has somepeculiar properties:• The number of ‘live’ moduli (of complex structure) of Σ is stronglyrestricted (roughly ‘3 times’ less than for a generic Riemann surface).The genus of Σ for the SU(N) gauge theories is exactly equal 25 to therank of gauge group – i.e., to the number of independent moduli.• The variation of generating 1–form dS over these moduli gives holomorphicdifferentials.• The periods of the generating 1–form∮∮a = dS and a D = dSAgive the set of ‘dual’ masses, the W −bosons and the monopoles, whilethe period matrix T ij (Σ) represents the set of couplings in the low–energy effective theory. The prepotential F = F(a) is a function of halfof the variables (a, a D ), so that we havea i D = ∂F∂a iand T ij = ∂ai D∂a j= ∂2 F∂a i ∂a j.These data mean that the effective SW theory is formulated in terms ofa classical finite–gap integrable system (see, e.g., [Dubrovin et. al. (1985)])and their Whitham deformations [Marshakov (1997)].B4.14.2 Clifford Actions, Dirac Operators and Spinor BundlesRecall that the SW monopole equations were written in terms of a sectionof a Spinor bundle and a U(1) connection on a line bundle L. The first25 For generic gauge groups one should speak instead of genus (i.e., dimension of Jacobianof a spectral curve) – about the dimension of Prym–variety. Practically it meansthat for other than A N −type gauge theories one should consider the spectral curves withinvolution and only the invariant under the involution cycles possess physical meaning.We consider in detail only the A N theories, the generalization to the other gauge groups isstraightforward: for example, instead of periodic Toda chains [Toda (1981)], correspondingto A N theories, one has to consider the ‘generalized’ Toda chains, first introducedfor different Lie–algebraic series (B, C, D, E, F and G) in [Bogoyavlensky (1981)].

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