41,967 research outputs found

    Fermions in non-relativistic AdS/CFT correspondence

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    We extend the non-relativistic AdS/CFT correspondence to the fermionic fields. In particular we study the two point function of a fermionic operator in non-relativistic CFTs by making use of a massive fermion propagating in geometries with Schrodinger group isometry. Although the boundary of the geometries with Schrodinger group isometry differ from that in AdS geometries where the dictionary of AdS/CFT is established, using the general procedure of AdS/CFT correspondence, we see that the resultant two point function has the expected form for fermionic operators in non-relativistic CFTs, though a non-trivial regularization may be needed.Comment: 12 pages,Latex file; V2: typos corrected, refs adde

    Massive Dirac surface states in topological insulator/magnetic insulator heterostructures

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    Topological insulators are new states of matter with a bulk gap and robust gapless surface states protected by time-reversal symmetry. When time-reversal symmetry is broken, the surface states are gapped, which induces a topological response of the system to electromagnetic field--the topological magnetoelectric effect. In this paper we study the behavior of topological surface states in heterostructures formed by a topological insulator and a magnetic insulator. Several magnetic insulators with compatible magnetic structure and relatively good lattice matching with topological insulators Bi2Se3,Bi2Se3,Sb2Te3{\rm Bi_2Se_3}, {\rm Bi_2Se_3}, {\rm Sb_2Te_3} are identified, and the best candidate material is found to be MnSe, an anti-ferromagnetic insulator. We perform first-principles calculation in Bi2Se3/MnSe{\rm Bi_2Se_3/MnSe} superlattices and obtain the surface state bandstructure. The magnetic exchange coupling with MnSe induces a gap of ∼\sim54 meV at the surface states. In addition we tune the distance between Mn ions and TI surface to study the distance dependence of the exchange coupling.Comment: 8 pages, 7 figure

    Religious affiliation and extramarital sex among men in Brazil.

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    CONTEXT: Since 1990, HIV infection in Brazil has spread among the heterosexual population, particularly in the north. Containment of the epidemic can be informed by a better understanding of men's sexual risk behavior. METHODS: Logistic, Poisson and multilevel logit models were applied to data on married and cohabiting men who had participated in the 1996 Brazilian Demographic and Health Survey. RESULTS: Twelve percent of married or cohabiting men reported having had at least one extramarital partner in the previous 12 months; half of these had had two or more. The majority (77%) of partners were described as friends or lovers; 4% had been prostitutes and 15% strangers. Among men who had had sex with an extramarital partner in the last year, 40% reported having used condoms during last extramarital sex. Compared with members of evangelical religions, other men were significantly more likely to report having had an extramarital partner (odds ratios, 3.0-4.7) and unprotected extramarital sex in the last 12 months (3.4-7.9). Region of residence was also strongly correlated with extramarital sex: Compared with men in southern or central Brazil, those in the north had more than three times the odds of having had extramarital sex and unprotected extramarital sex in the last year (3.1-3.8). CONCLUSION: In Brazil, religious affiliation and region of residence exert a major influence on risk behavior

    The Timing Noise of PSR 0823+26, PSR 1706-16, PSR 1749-28, PSR 2021+51 and The Anomalous Braking Indices

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    We have investigated the stability of the pulse frequency second derivatives (ν¨\ddot \nu ) of PSR 0823+26, PSR 1706-16, PSR 1749-28, PSR 2021+51 which show significant quadratic trends in their pulse frequency histories in order to determine whether the observed second derivatives are secular or they arise as part of noise processes. We have used TOA data extending to more than three decades which are the longest time spans ever taken into account in pulse timing analyses. We investigated the stability of pulse frequency second derivative in the framework of low resolution noise power spectra (Deeter 1984) estimated from the residuals of pulse frequency and TOA data. We have found that the ν¨\ddot \nu terms of these sources arise from the red torque noise in the fluctuations of pulse frequency derivatives which may originate from the external torques from the magnetosphere of pulsar

    Testing Creditor Moral Hazard in Sovereign Bond Markets: A Unified Theoretical Approach and Empirical Evidence

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    This paper critically evaluates the existing empirical literature on creditor moral hazard in sovereign bond markets, proposes a unified theoretical approach to test for IMF-induced creditor moral hazard, and provides empirical evidence, using daily sovereign bond market spreads of Indonesia and Korea. The results suggest that IMF-related news regarding program negotiations and approval may be associated with creditor moral hazard, but their impact on spreads is short-lived, indicating that creditor moral hazard could be best described as a short-run phenomenon.Creditor moral hazard, financial markets, the IMF, and news

    Geodesic Congruences in the Palatini f(R) Theory

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    We shall investigate the properties of a congruence of geodesics in the framework of Palatini f(R) theories. We shall evaluate the modified geodesic deviation equation and the Raychaudhuri's equation and show that f(R) Palatini theories do not necessarily lead to attractive forces. Also we shall study energy condition for f(R) Palatini gravity via a perturbative analysis of the Raychaudhuri's equation
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