6,503 research outputs found

    Cusp anomalous dimension in maximally supersymmetric Yang-Mills theory at strong coupling

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    We construct an exact analytical solution to the integral equation which is believed to describe logarithmic growth of the anomalous dimensions of high spin operators in planar N=4 super Yang-Mills theory and use it to determine the strong coupling expansion of the cusp anomalous dimension.Comment: 5 pages. v3: minor corrections, references and important note adde

    Natural Z′Z' model with an inverse seesaw and leptonic dark matter

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    We consider a model for a Z'-boson coupled only to baryon minus lepton number and hypercharge. Besides the usual right-handed neutrinos, we add a pair of fermions with a fractional lepton charge, which we therefore call leptinos. One of the leptinos is taken to be odd under an additional Z_2 charge, the other even. This allows for a natural (inverse) seesaw mechanism for neutrino masses. The odd leptino is a candidate for dark matter, but has to be resonantly annihilated by the Z'-boson or the Higgs-boson responsible for giving mass to the former. Considering collider and cosmological bounds on the model, we find that the Z'-boson and/or the extra Higgs-boson can be seen at the LHC. With more pairs of leptinos leptogenesis is possible.Comment: 29 pages, 9 figures. RGE section moved to appendix and other minor corrections applied to matched published versio

    Direct calorimetric measurements of isothermal entropy change on single crystal W-type hexaferrites at the spin reorientation transition

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    We report on the magnetic field induced isothermal entropy change, \Delta s(Ha, T), of W-type ferrite with CoZn substitution. Entropy measurements are performed by direct calorimetry. Single crystals of the composition BaCo0.62_0.62Zn1.38_1.38Fe16_16O27_27, prepared by the flux method, are measured at different fixed temperatures under an applied field perpendicular and parallel to the c axis. At 296 K one deduces a value of K1_1 = 8.7 \times 10^{4} J m‚ąí3^-3 for the first anisotropy constant, which is in good agreement with the literature. The spin reorientation transition temperature is estimated to take place between 200 and 220 K

    Ground state optimization and hysteretic demagnetization: the random-field Ising model

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    We compare the ground state of the random-field Ising model with Gaussian distributed random fields, with its non-equilibrium hysteretic counterpart, the demagnetized state. This is a low energy state obtained by a sequence of slow magnetic field oscillations with decreasing amplitude. The main concern is how optimized the demagnetized state is with respect to the best-possible ground state. Exact results for the energy in d=1 show that in a paramagnet, with finite spin-spin correlations, there is a significant difference in the energies if the disorder is not so strong that the states are trivially almost alike. We use numerical simulations to better characterize the difference between the ground state and the demagnetized state. For d>=3 the random-field Ising model displays a disorder induced phase transition between a paramagnetic and a ferromagnetic state. The locations of the critical points R_c(DS), R_c(GS) differ for the demagnetized state and ground state. Consequently, it is in this regime that the optimization of the demagnetized stat is the worst whereas both deep in the paramagnetic regime and in the ferromagnetic one the states resemble each other to a great extent. We argue based on the numerics that in d=3 the scaling at the transition is the same in the demagnetized and ground states. This claim is corroborated by the exact solution of the model on the Bethe lattice, where the R_c's are also different.Comment: 13 figs. Submitted to Phys. Rev.

    Screening for hazardous alcohol use and dependence in psychiatric in-patients using the AUDIT questionnaire

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    The Alcohol Use Disorders Identification Test (AUDIT) has been used to screen for hazardous and harmful alcohol consumption among general hospital populations but not in psychiatric patients. Using the AUDIT, we assessed alcohol use in patients with four major types of psychiatric disorder, namely mood, adjustment, anxiety and psychotic disorders. Nine hundred and ninety consecutive admissions to the psychiatric units of two hospitals during a 12-month period underwent assessment. In each diagnostic group a high proportion of patients was alcohol-dependent. Among those with mood disorders 25.4% of men were alcohol-dependent, compared with 16.3% of women, while 34.5% of men with anxiety disorder were alcohol-dependent compared with 25.0% of women. Both gender differences were statistically significant. The differences were even greater for adjustment disorder (44.4% vs. 14.5%) and psychosis (29.2% and 4.2%, respectively). More men than women with anxiety disorder were classified as hazardous (24.1% vs. 11.7%) or harmful drinkers (13.8% vs. 3.3%), but for the other diagnostic groupings the percentages in these drinking categories were more nearly similar. Thus, there is a high rate of excessive alcohol consumption in people with psychiatric disorders, especially males. Such individuals may be particularly vulnerable to complications of alcohol misuse such as suicide and exacerbation of their disorder. The potential for decreased severity of psychiatric symptoms and a reduction in the number of hospital admissions following cessation or reduction in alcohol consumption is considerable. The AUDIT is a simple screening device for investigating alcohol use and dependence, and offers a means of initiating intervention in this population

    Event-based quickflow simulation with OpenLISEM in a burned Mediterranean forest catchment

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    Recently burnt areas typically reveal strong to extreme hydrological responses, as a consequence of loss of protective soil cover and heating-induced changes in topsoil properties. Soil water repellency (SWR) has frequently been referred to as one of the explanatory variables for fireenhanced surface runoff generation but this has been poorly demonstrated, especially at the catchment scale. This study employs a process-based modelling approach to better understand the relevance of SWR in the hydrological response of a small, entirely burnt catchment in central Portugal, in particular by comparing hydrological events under contrasting initial conditions of dry vs wet soils. The OpenLISEM model was applied to a selection of 16 major rainfall runoff events that occurred during the first 2 post-fire years. The automatic calibration procedure resulted in good model performance, but it worsened for validation events. Furthermore, uncertainty analysis revealed an elevated sensitivity of OpenLISEM to event-specific conditions, especially for predicting the events’ total and peak flows. Also, predicted spatial patterns in runoff poorly agreed with the runoff observed in microplots. Model performance improved when events were separated by dry and wet initial moisture conditions, particularly for wet conditions, suggesting the role of variables other than initial soil moisture.info:eu-repo/semantics/publishedVersio

    Self-organized criticality in the hysteresis of the Sherrington - Kirkpatrick model

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    We study hysteretic phenomena in random ferromagnets. We argue that the angle dependent magnetostatic (dipolar) terms introduce frustration and long range interactions in these systems. This makes it plausible that the Sherrington - Kirkpatrick model may be able to capture some of the relevant physics of these systems. We use scaling arguments, replica calculations and large scale numerical simulations to characterize the hysteresis of the zero temperature SK model. By constructing the distribution functions of the avalanche sizes, magnetization jumps and local fields, we conclude that the system exhibits self-organized criticality everywhere on the hysteresis loop.Comment: 4 pages, 4 eps figure

    Instability of the expression of morphological and phenological descriptors to environmental variation in white oat.

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    Made available in DSpace on 2018-01-11T23:31:30Z (GMT). No. of bitstreams: 1 445750711013.pdf: 442070 bytes, checksum: 9b519c484cf8867bc90e3d467624c188 (MD5) Previous issue date: 2018-01-10bitstream/item/170731/1/445750711013.pd

    TBA-like equations and Casimir effect in (non-)perturbative AdS/CFT

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    We consider high spin, ss, long twist, LL, planar operators (asymptotic Bethe Ansatz) of strong N=4{\cal N}=4 SYM. Precisely, we compute the minimal anomalous dimensions for large 't Hooft coupling őĽ\lambda to the lowest order of the (string) scaling variable ‚Ąď‚ąľL/(ln‚Ā°SőĽ)\ell \sim L/ (\ln \mathcal{S} \sqrt{\lambda}) with GKP string size ‚ąľln‚Ā°S‚Č°2ln‚Ā°(s/őĽ)\sim\ln \mathcal{S}\equiv 2 \ln (s/\sqrt{\lambda}). At the leading order (ln‚Ā°S)‚čÖ‚Ąď2(\ln \mathcal{S}) \cdot \ell ^2 , we can confirm the O(6) non-linear sigma model description for this bulk term, without boundary term (ln‚Ā°S)0(\ln \mathcal{S})^0. Going further, we derive, extending the O(6) regime, the exact effect of the size finiteness. In particular, we compute, at all loops, the first Casimir correction ‚Ąď0/ln‚Ā°S\ell ^0/\ln \mathcal{S} (in terms of the infinite size O(6) NLSM), which reveals only one massless mode (out of five), as predictable once the O(6) description has been extended. Consequently, upon comparing with string theory expansion, at one loop our findings agree for large twist, while reveal for negligible twist, already at this order, the appearance of wrapping. At two loops, as well as for next loops and orders, we can produce predictions, which may guide future string computations.Comment: Version 2 with: new exact expression for the Casimir energy derived (beyond the first two loops of the previous version); UV theory formulated and analysed extensively in the Appendix C; origin of the O(6) NLSM scattering clarified; typos correct and references adde
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