24,803 research outputs found

    Continuum Limits of ``Induced QCD": Lessons of the Gaussian Model at d=1 and Beyond

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    We analyze the scalar field sector of the Kazakov--Migdal model of induced QCD. We present a detailed description of the simplest one dimensional {(dd==11)} model which supports the hypothesis of wide applicability of the mean--field approximation for the scalar fields and the existence of critical behaviour in the model when the scalar action is Gaussian. Despite the ocurrence of various non--trivial types of critical behaviour in the d=1d=1 model as N→∞N\rightarrow\infty, only the conventional large-NN limit is relevant for its {\it continuum} limit. We also give a mean--field analysis of the N=2N=2 model in {\it any} dd and show that a saddle point always exists in the region m2>mcrit2(=d)m^2>m_{\rm crit}^2(=d). In d=1d=1 it exhibits critical behaviour as m2→mcrit2m^2\rightarrow m_{\rm crit}^2. However when dd>>11 there is no critical behaviour unless non--Gaussian terms are added to the scalar field action. We argue that similar behaviour should occur for any finite NN thus providing a simple explanation of a recent result of D. Gross. We show that critical behaviour at dd>>11 and m2>mcrit2m^2>m^2_{\rm crit} can be obtained by adding a logarithmiclogarithmic term to the scalar potential. This is equivalent to a local modification of the integration measure in the original Kazakov--Migdal model. Experience from previous studies of the Generalized Kontsevich Model implies that, unlike the inclusion of higher powers in the potential, this minor modification should not substantially alter the behaviour of the Gaussian model.Comment: 31 page

    Analytical mode normalization and resonant state expansion for optical fibers - an efficient tool to model transverse disorder

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    We adapt the resonant state expansion to optical fibers such as capillary and photonic crystal fibers. As a key requirement of the resonant state expansion and any related perturbative approach, we derive the correct analytical normalization for all modes of these fiber structures, including leaky modes that radiate energy perpendicular to the direction of propagation and have fields that grow with distance from the fiber core. Based on the normalized fiber modes, an eigenvalue equation is derived that allows for calculating the influence of small and large perturbations such as structural disorder on the guiding properties. This is demonstrated for two test systems: a capillary fiber and an endlessly single mode fiber.Comment: 10 pages, 4 figure

    Sexual behaviour and HIV/sexually transmitted infection risk behaviours in the general population of Slovenia, a low HIV prevalence country in central Europe.

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    OBJECTIVES: To describe sexual and HIV/sexually transmitted infection (STI) risk behaviours in Slovenia. METHODS: A nationally representative cross-sectional survey of the general population aged 18-49 years in 1999-2001 was conducted. The data were collected by face-to-face interviews and anonymous self-administered questionnaires. Statistical methods for complex survey data were used. RESULTS: 849 men and 903 women were interviewed. In the past 5 years, both men and women reported a median of one heterosexual partner (means 3.2, 1.5, respectively), concurrent heterosexual partnerships were reported by 24.4% of men and 8.2% of women, heterosexual sex with non-Slovenian partners by 12.6% of men and 12.2% of women, forced sex by 4.8% of women, paid heterosexual sex by 2.6% of men, sex with another man by 0.6% of men and heterosexual sex with an injecting drug user by 1.2% of men and 1.3% of women. In the past year, 22.7% of men and 9.5% of women reported forming at least one new heterosexual partnership. The mean numbers of episodes of heterosexual sex in the previous 4 weeks were 6.1 for men and 6.0 for women. Consistent and inconsistent condom use was reported more frequently among men reporting multiple female partners and those not married or cohabiting. CONCLUSIONS: Recent patterns of reported sexual behaviour are consistent with a low risk of HIV and STI transmission in Slovenia. The results will inform Slovenian sexual health policies including HIV/STI prevention, and are particularly valuable because population-based data on HIV/STI risk behaviour have not previously been available in low HIV prevalence countries of central Europe

    A Generalised Sidelobe Canceller Architecture Based on Oversampled Subband Decompositions

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    Adaptive broadband beamforming can be performed in oversampled subband signals, whereby an independent beamformer is operated in each frequency band. This has been shown to result in a considerably reduced computational complexity. In this paper, we primarily investigate the convergence behaviour of the generalised sidelobe canceller (GSC) based on normalised least mean squares algorithm (NLMS) when operated in subbands. The minimum mean squared error can be limited, amongst other factors, by the aliasing present in the subbands. With regard to convergence speed, there is strong indication that the subband-GSC converges faster than a fullband counterpart of similar modelling capabilities. Simulations are presented

    QED With Unequal Charges: A study of spontaneous Zn symmetry breaking

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    We study two-dimensional QED with unequal charges at finite temperature, and show that there is a phase with a spontaneously broken ZnZ_n symmetry. In spite of this, we were not able to establish the presence of domain walls. The relevance for QCD in higher dimensions is discussed.Comment: 14 Page

    Influences of an impurity on the transport properties of one-dimensional antisymmetric spin filter

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    The influences of an impurity on the spin and the charge transport of one-dimensional antisymmetric spin filter are investigated using bosonization and Keldysh formulation and the results are highlighted against those of spinful Luttinger liquids. Due to the dependence of the electron spin orientation on wave number the spin transport is not affected by the impurity, while the charge transport is essentially identical with that of spinless one-dimensional Luttinger liquid.Comment: 7 pages, 2 figures. To appear in Physical Review

    Title IX versus Candian Human Rights Legislation: How the United States Should Learn from Canada\u27s Human Rights Act in the Context of Sexual Harassment in Schools

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    This Article critically examines the success of Title IX in eradicating sexual harassment in educational settings after the Supreme Court decisions in Gebser v. Lago and Monroe v. Davis. Regrettably, the high bar for recovery established by these cases, in addition to poor administrative enforcement of Title IX have eroded its ability to maintain discrimination-free schools. After an examination of the manner in which the Canadian human rights model operates in the context of sexual harassment in educational settings, recommendations are made that the United States should use the Canadian example to improve its own system. Specifically, the United States should streamline and simplify its administrative enforcement of Title IX and articulate clearer legal standards for injunctive relief as opposed to recovery of compensatory damages

    Violation of the Leggett-Garg Inequality in Neutrino Oscillations

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    The Leggett-Garg inequality, an analogue of Bell's inequality involving correlations of measurements on a system at different times, stands as one of the hallmark tests of quantum mechanics against classical predictions. The phenomenon of neutrino oscillations should adhere to quantum-mechanical predictions and provide an observable violation of the Leggett-Garg inequality. We demonstrate how oscillation phenomena can be used to test for violations of the classical bound by performing measurements on an ensemble of neutrinos at distinct energies, as opposed to a single neutrino at distinct times. A study of the MINOS experiment's data shows a greater than 6σ6{\sigma} violation over a distance of 735 km, representing the longest distance over which either the Leggett-Garg inequality or Bell's inequality has been tested.Comment: Updated to match published version. 6 pages, 2 figure
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