Emergent Commensurability from Hilbert Space Truncation in Fractional Quantum Hall Fluids

We show that model states of fractional quantum Hall fluids at all experimentally detected plateau can be uniquely determined by imposing translational invariance with a particular scheme of Hilbert space truncation motivated from physical local measurements. The scheme allows us to identify filling factors, topological shifts and pairing/clustering of topological quantum fluids unambiguously in a universal way without resorting to microscopic Hamiltonians. This prompts us to propose the notion of emergent commensurability as a fundamental property for at least most of the known FQH states, which allows us to predict if a particular FQH state conforming to a set of paradigms can be realised \emph{in principle}. We also discuss the implications of certain missing states proposed from other phenomenological approaches, and suggest that the physics of fractional quantum Hall physics could fundamentally arise from the algebra of the Hilbert space in a single Landau level.Comment: 4+ pages, 2 figures, comments very welcome (typo corrected

A note on the almost one half holomorphic pinching

Motivated by a previous work of Zheng and the second named author, we study pinching constants of compact K\"ahler manifolds with positive holomorphic sectional curvature. In particular we prove a gap theorem following the work of Petersen and Tao on Riemannian manifolds with almost quarter-pinched sectional curvature.Comment: 6 pages. This is the version which the authors submitted to a journal for consideration for publication in June 2017. The reference has not been updated since the