132 research outputs found

    The Lagrangian cobordism group of T2T^2

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    We compute the Lagrangian cobordism group of the standard symplectic 2-torus and prove that it is isomorphic to the Grothendieck group of its derived Fukaya category. The proofs use homological mirror symmetry for the 2-torus.Comment: 43 pages, 12 figures. V2: Result of computation of the cobordism group reformulated; further minor changes and corrections. V3: Updated such as to agree with accepted version. To appear in Selecta Mathematic

    Teaching Inverse Reinforcement Learners via Features and Demonstrations

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    Learning near-optimal behaviour from an expert's demonstrations typically relies on the assumption that the learner knows the features that the true reward function depends on. In this paper, we study the problem of learning from demonstrations in the setting where this is not the case, i.e., where there is a mismatch between the worldviews of the learner and the expert. We introduce a natural quantity, the teaching risk, which measures the potential suboptimality of policies that look optimal to the learner in this setting. We show that bounds on the teaching risk guarantee that the learner is able to find a near-optimal policy using standard algorithms based on inverse reinforcement learning. Based on these findings, we suggest a teaching scheme in which the expert can decrease the teaching risk by updating the learner's worldview, and thus ultimately enable her to find a near-optimal policy.Comment: NeurIPS'2018 (extended version

    On the Quantum Homology of Real Lagrangians in Fano Toric Manifolds

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    Let R be the real Lagrangian in a toric symplectic manifold X, the fixed point set under complex conjugation. Assuming that X is Fano of minimal Chern number at least 2, we show that the Lagrangian quantum homology QH(R;Λ) of R over the ring is isomorphic to as a module. Moreover, we prove that QH(R;Λ) is isomorphic as a ring to the quantum homology QH(X;Λ) of the ambient symplectic manifol

    On the Quantum Homology of Real Lagrangians in Fano Toric Manifolds

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    We study the Lagrangian quantum homology of real parts of Fano toric manifolds of minimal Chern number at least 2, using coefficients in a ring of Laurent polynomials over Z/2Z. We show that these Lagrangians are wide, in the sense that their quantum homology is isomorphic as a module to their classical homology tensored with this ring. Moreover, we show that the quantum homology is isomorphic as a ring to the quantum homology of the ambient symplectic manifold.Comment: 36 pages, figures. Version 2: Typos corrected, minor changes. Version 3: Journal reference adde

    Polarization and Aharonov-Bohm oscillations in quantum-ring magnetoexcitons

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    We study interaction and radial polarization effects on the the absorption spectrum of neutral bound magnetoexcitons confined in quantum-ring structures. We show that the size and orientation of the exciton's dipole moment, as well as the interaction screening, play important roles in the Aharonov-Bohm oscillations. In particular, the excitonic absorption peaks display A-B oscillations both in position and amplitude for weak electron-hole interaction and large radial polarization. The presence of impurity scattering induces anticrossings in the exciton spectrum, leading to a modulation in the absorption strength. These properties could be used in experimental investigations of the effect in semiconductor quantum-ring structures.Comment: Updated version, 6 pages, 4 figures. To appear in Phys. Rev.

    Living Labs for Public Sector Innovation:Insights from a European case study

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    Living labs have gained increased attention in research and practice as both a practical and theoretical innovation phenomenon that emphasizes co-creation, real-life settings, and user/customer involvement. More recently, living labs have also emerged as a specific approach to open innovation processes in the context of publics across the EU. Nevertheless, it is still not clear how the understanding of living labs can be translated and organized into new sectorial settings, what type of public sector innovation challenges it addresses, and what role citizens and users have. The aim of this article is therefore to explore and analyze how living labs are applied as processes for public sector innovation. Based on a mixed method approach of 21 European living lab cases, the analysis reveals a pattern of three different processes for living lab organizational and actor roles: living labs organized as cross-sectorial collaboration, living labs emerging within the public sector as main initiator and beneficiary, and living labs developed by civil society actors. The findings are presented as three scenarios for implementing living labs, which also acts as a background for the article's final discussion about the potentials and pitfalls of living labs in public sector contexts.publishe

    Critical review of analytical methods for the determination of flame retardants in human matrices

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    Human biomonitoring is a powerful approach in assessing exposure to environmental pollutants. Flame retardants (FRs) are of particular concern due to their wide distribution in the environment and adverse health effects. This article reviews studies published in 2009-2020 on the chemical analysis of FRs in a variety of human samples and discusses the characteristics of the analytical methods applied to different FR biomarkers of exposure, including polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), novel halogenated flame retardants (NHFRs), bromophenols, incl. tetrabromobisphenol A (TBBPA), and organophosphorous flame retardants (PFRs). Among the extraction techniques, liquid-liquid extraction (LLE) and solid phase extraction (SPE) were used most frequently due to the good efficiencies in the isolation of the majority of the FR biomarkers, but with challenges for highly lipophilic FRs. Gas chromatography-mass spectrometry (GC-MS) is mainly applied in the instrumental analysis of PBDEs and most NHFRs, with recent inclusions of GC-MS/MS and high resolution MS techniques. Liquid chromatography-MS/MS is mainly applied to HBCD, bromophenols, incl. TBBPA, and PFRs (including metabolites), however, GC-based analysis following derivatization has also been used for phenolic compounds and PFR metabolites. Developments are noticed towards more universal analytical methods, which enable widening method scopes in the human biomonitoring of FRs. Challenges exist with regard to sensitivity required for the low concentrations of FRs in the general population and limited sample material for some human matrices. A strong focus on quality assurance/quality control (QA/QC) measures is required in the analysis of FR biomarkers in human samples, related to their variety of physical-chemical properties, low levels in most human samples and the risk of contamination.This study was part of the HBM4EU project receiving funding from the European Union's Horizon 2020 research and innovation programme under Grant Agreement No. 733032. The authors acknowledge Berith E. Knudsen for her help with the literature search.S
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