Narrow Results

We study the classification of the pairs (N, X) where N is a Stein surface and X is a ℂ-complete holomorphic vector field with isolated singularities on N. We describe the role of transverse sections in the classification of X and give necessary and sufficient conditions on X in order to have N biholomorphic to ℂ². As a sample of our results, we prove that N is biholomorphic to ℂ² if H²(N, ℤ) = 0, X has a finite number of singularities and exhibits a singularity with three separatrices or, equivalently, a singularity with first jet of the form where λ₁/λ₂ ∈ ℚ₊. We also study flows with many periodic orbits (i.e. orbits diffeomorphic to ℂ*), in a sense we will make clear, proving they admit a meromorphic first integral or they exhibit some special periodic orbit, whose holonomy map is a non-resonant nonlinearizable diffeomorphism map.

U(1) Chern–Simons theory is quantized canonically on manifolds of the form , where Σ is a closed orientable surface. In particular, we investigate the role of mapping class group of Σ in the process of quantization. We show that, by requiring the quantum states to form representation of the holonomy group and the large gauge transformation group, both of which are deformed by quantum effect, the mapping class group can be consistently represented, provided the Chern–Simons parameter k satisfies an interesting quantization condition. The representations of all the discrete groups are unique, up to an arbitrary sub-representation of the mapping class group. Also, we find a k↔1/k duality of the representations.

A complete decomposition of the space of the curvature tensors over tensor product of vector spaces into simple modules under the action of the group G = GL(p, ℝ) ⊗ GL(q, ℝ) is given. We use these results to study geometry of manifolds with Grassmann structure and Grassmann manifolds endowed with a connection whose torsion is not zero. We show that Osc^r M a manifold is an example of a manifold with Grassmann structure. Owing to this fact, we consider results of Miron, Atanasiu, Anastasiei, Čomić and others from representation theory point of view and connect them with some results of Alekseevsky, Cortes, and Devchand, as well as of Machida and Sato, and others. New examples of connections with torsion defined on four-dimensional Grassmann manifold are given. Symmetries of curvatures for half-flat connections are also investigated. We use algebraic results to reveal obstructions to the existence of corresponding connections.

We develop a new description of curved manifolds that represent a topological phase for the usual Levi-Civita connection and a dynamical phase for the torsion, being the only part of the connection that generates curvature. The holonomy group structure of such manifolds is studied, and different expressions of the torsion in terms of gauge fields are considered with the purpose to describe different dynamical scenarios. Additionally some models of torsion interacting with fermions are constructed; specifically a four-dimensional model that mimics an usual fermion-gauge fields system is considered; this model undergoes parity symmetry breaking with a dynamical background. Since these manifolds represent new gravitational backgrounds, we speculate on possible applications in the study of qualitative and quantitative aspects of the gauge/gravity duality.