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Why Thomas-Yau has predictive power [047N]

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Why Thomas-Yau has predictive power

At this moment an objection may arise: since the Thomas-Yau-Joyce picture is beset by some vagueness and plenty of technical difficulties, why is it useful as a guiding principle at all? Besides the supportive evidence that we shall soon discuss, the main answer is that the Thomas-Yau philosophy transforms a PDE problem (the existence of special Lagrangians) into a categorical framework, which if better understood is in principle checkable by algebraic means. A Bridgeland stability is the interplay between a category and a numerical property. In the analogous problem of Hermitian Yang-Mills connections, the existence criterion is formulated by μ\mu-stability, which compresses the information of the Kähler form into only certain intersection numbers/cohomological integrals (cf. section 2.5). Likewise, the stability condition responsible for the existence of special Lagrangians, even though it is not adequately specified, is in principle a compression of the analytic data of a holomorphic volume form, and quite plausibly enters only through cohomological integrals of Ω\Omega, as will be discussed more fully in Chapter 3. As an indication of the possible predicative power of the Thomas-Yau picture, here is a sample question as food for thought:

Question 1.

Fix the holomorphic volume form Ω\Omega. Let ω1,ω2\omega_{1},\omega_{2} be two generic Kähler forms, differing only by the differential of a compactly supported 1-form. Can we define a count of special Lagrangian rational homology spheres, such that the numbers agree for ω1\omega_{1} and ω2\omega_{2}?

Remark 2.4.

As we shall see, the main evidence of Thomas-Yau picture (cf. section 2.2) does not really use the complex Monge-Ampère equation.1111 11 The almost Calabi-Yau setting is desirable not only for the sake of generality, but may be essential to achieve suitable genericity. As an additional motivation on the side of physics, the SCFT condition translates into a Kähler condition on the target space metric, which satisfies the Ricci-flatness only approximately [38, section 14.2.4]. On the mirror side, as a consequence of the μ\mu-stability characterisation, the existence of Hermitian Yang Mills connections on a compact Kähler manifold does not depend on the choice of the Kähler form within a fixed Kähler class.

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