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Ivancevic_Applied-Diff-Geom

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<strong>Geom</strong>etrical Path Integrals and Their Applications 1103constructed out of them. They constitute a very useful tool to build theobservables of the theory.6.5.2 Seiberg–Witten Theory and TQFTRecall that the field of low–dimensional geometry and topology [Atiyah(1988b)] has undergone a dramatic phase of progress in the last decade ofthe 20th Century, prompted, to a large extend, by new ideas and discoveriesin mathematical physics. The discovery of quantum groups [Drinfeld(1986)] in the study of the Yang–Baxter equation [Baxter (1982)] has reshapedthe theory of knots and links [Jones (1985); Reshetikhin and Turaev(1991); Zhang et. al. (1991)]; the study of conformal field theory andquantum Chern–Simons theory [Witten (1989)] in physics had a profoundimpact on the theory of 3–manifolds; and most importantly, investigationsof the classical Yang–Mills (YM) theory led to the creation of the Donaldsontheory of 4–manifolds [Freed and Uhlenbeck (1984); Donaldson (1987)].Witten [Witten (1994)] discovered a new set of invariants of 4–manifoldsin the study of the Seiberg–Witten (SW) monopole equations, which havetheir origin in supersymmetric gauge theory. The SW theory, while closelyrelated to Donaldson theory, is much easier to handle. Using SW theory,proofs of many theorems in Donaldson theory have been simplified,and several important new results have also been obtained [Taubes (1990);Taubes (1994)].In [Zhang et. al. (1995)] a topological quantum field theory was introducedwhich reproduces the SW invariants of 4–manifolds. A geometricalinterpretation of the 3D quantum field theory was also given.6.5.2.1 SW Invariants and Monopole EquationsRecall that the SW monopole equations are classical field theoretical equationsinvolving a U(1) gauge field and a complex Weyl spinor on a 4Dmanifold. Let X denote the 4–manifold, which is assumed to be orientedand closed. If X is spin, there exist positive and negative spin bundles S ±of rank two. Introduce a complex line bundle L → X. Let A be a connectionon L and M be a section of the product bundle S + ⊗ L. Recall thatthe SW monopole equations readF + kl = − i 2 ¯MΓ kl M, D A M = 0, (6.167)

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