648,561 research outputs found

    Explicit birational geometry of 3-folds of general type, I

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    Let VV be a complex nonsingular projective 3-fold of general type. We prove P12(V):=dimH0(V,12KV)>0P_{12}(V):=\text{dim} H^0(V, 12K_V)>0 and Pm0(V)>1P_{m_0}(V)>1 for some positive integer m024m_0\leq 24. A direct consequence is the birationality of the pluricanonical map φm\varphi_m for all m126m\geq 126. Besides, the canonical volume Vol(V)\text{Vol}(V) has a universal lower bound ν(3)1631262\nu(3)\geq \frac{1}{63\cdot 126^2}.Comment: 29 pages, Ann Sci Ecole Norm Sup (to appear

    Phonological similarity effects in Cantonese word recognition

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    Two lexical decision experiments in Cantonese are described in which the recognition of spoken target words as a function of phonological similarity to a preceding prime is investigated. Phonological similaritv in first syllables produced inhibition, while similarity in second syllables led to facilitation. Differences between syllables in tonal and segmental structure had generally similar effects

    Anti-ferrodistortive Nanodomains in PMN Relaxor

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    Temperature dependent studies of the 1/2(hk0) superlattice reflections \alpha spots by synchrotron x-ray scattering measurements were performed in (PMN) and (PMN-xPT) with Ti doping x<0.32 single crystals. Separation of the \alpha spots from the underlying diffuse scattering background allowed studying them as separate entities for the first time. Structure factor calculations have shown that alpha spots constitute the presence of a new kind of anti-ferrodistortive nanoregions (AFR) in the form of fluctuations produced by anti-parallel short-range correlated Pb^2+ displacements. AFR appear to be different and unrelated to the chemical nanodomains (CND) and ferroelectric polar nanoregions (PNR). Simultaneous presence of AFR and PNR can explain relaxor behavior as a result of competition between randomly occurring ferroelectric and anti-ferroelectric fluctuations. Temperature dependence of the \alpha spots in PMN showed a direct correlation with the freezing phase transition near Tf~220 K.Comment: 10 pages, 7 figures, Conference-Fundamental Physics of Ferroelectrics 200

    Longevity impact on life insurers in low interest rate environment

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    This paper aims at shedding some light on the interplay between two key risk factors affecting most life insurance products, namely biometric and investment risk. We enhance the pioneering model by Briys and de Varenne, featuring a stylized participating life insurance company by explicitly tying benefits to the survivorship of a cohort of policyholders. In particular, we allow for the two main components of biometric risk, that is systematic (longevity) risk and diversifiable (process) risk

    Frustrated double ionization in two-electron triatomic molecules

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    Using a semi-classical model, we investigate frustrated double ionization (FDI) in D3+\mathrm{D_3^+}, a two-electron triatomic molecule, when driven by an intense, linearly polarized, near-infrared (800 nm) laser field. We compute the kinetic energy release of the nuclei and find a good agreement between experiment and our model. We explore the two pathways of FDI and show that, with increasing field strength, over-the-barrier ionization overtakes tunnel ionization as the underlying mechanism of FDI. Moreover, we compute the angular distribution of the ion fragments for FDI and identify a feature that can potentially be observed experimentally and is a signature of only one of the two pathways of FDI.Comment: 5 pages, 4 figure
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