4,093 research outputs found

    Calibration of Multicurrency LIBOR Market Models

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    This paper presents a methodf or calibrating a multi currency lognormal LIBOR Market Model to market data of at-the-money caps, swaptions and FX options. By exploiting the fact that multivariate normal distributions are invariant under orthonormal transformations, the calibration problem is decomposed into manageable stages, while maintaining the ability to achieve realistic correlation structures between all modelled market variables.currency options; LIBOR market model; exchange rate risk; interest rate risk

    Electrical Control of Structural and Physical Properties via Strong Spin-Orbit Interactions in Sr2IrO4

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    Electrical control of structural and physical properties is a long-sought, but elusive goal of contemporary science and technology. We demonstrate that a combination of strong spin-orbit interactions (SOI) and a canted antiferromagnetic (AFM) Mott state is sufficient to attain that goal. The AFM insulator Sr2IrO4 provides a model system in which strong SOI lock canted Ir magnetic moments to IrO6-octahedra, causing them to rigidly rotate together. A novel coupling between an applied electrical current and the canting angle reduces the N\'eel temperature and drives a large, non-linear lattice expansion that closely tracks the magnetization, increases the electron mobility, and precipitates a unique resistive switching effect. Our observations open new avenues for understanding fundamental physics driven by strong SOI in condensed matter, and provide a new paradigm for functional materials and devices.Comment: 5 figures; to be published in Physical Review Letter

    Breaking the Curve with CANDELS: A Bayesian Approach to Reveal the Non-Universality of the Dust-Attenuation Law at High Redshift

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    Dust attenuation affects nearly all observational aspects of galaxy evolution, yet very little is known about the form of the dust-attenuation law in the distant Universe. Here, we model the spectral energy distributions (SEDs) of galaxies at z = 1.5--3 from CANDELS with rest-frame UV to near-IR imaging under different assumptions about the dust law, and compare the amount of inferred attenuated light with the observed infrared (IR) luminosities. Some individual galaxies show strong Bayesian evidence in preference of one dust law over another, and this preference agrees with their observed location on the plane of infrared excess (IRX, LTIR/LUVL_{\text{TIR}}/L_{\text{UV}}) and UV slope (ÎČ\beta). We generalize the shape of the dust law with an empirical model, Aλ,ÎŽ=E(B−V) kλ (λ/λV)ÎŽA_{\lambda,\delta}=E(B-V)\ k_\lambda\ (\lambda/\lambda_V)^\delta where kλk_\lambda is the dust law of Calzetti et al. (2000), and show that there exists a correlation between the color excess E(B−V){E(B-V)} and tilt ÎŽ\delta with ÎŽ=(0.62±0.05)log⁥(E(B−V)){\delta=(0.62\pm0.05)\log(E(B-V))}+ (0.26 ± 0.02){(0.26~\pm~0.02)}. Galaxies with high color excess have a shallower, starburst-like law, and those with low color excess have a steeper, SMC-like law. Surprisingly, the galaxies in our sample show no correlation between the shape of the dust law and stellar mass, star-formation rate, or ÎČ\beta. The change in the dust law with color excess is consistent with a model where attenuation is caused by by scattering, a mixed star-dust geometry, and/or trends with stellar population age, metallicity, and dust grain size. This rest-frame UV-to-near-IR method shows potential to constrain the dust law at even higher (z>3z>3) redshifts.Comment: 20 pages, 18 figures, resubmitted to Ap

    Discovery of New Ultracool White Dwarfs in the Sloan Digital Sky Survey

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    We report the discovery of five very cool white dwarfs in the Sloan Digital Sky Survey (SDSS). Four are ultracool, exhibiting strong collision induced absorption (CIA) from molecular hydrogen and are similar in color to the three previously known coolest white dwarfs, SDSS J1337+00, LHS 3250 and LHS 1402. The fifth, an ultracool white dwarf candidate, shows milder CIA flux suppression and has a color and spectral shape similar to WD 0346+246. All five new white dwarfs are faint (g > 18.9) and have significant proper motions. One of the new ultracool white dwarfs, SDSS J0947, appears to be in a binary system with a slightly warmer (T_{eff} ~ 5000K) white dwarf companion.Comment: 15 pages, 3 figures, submitted to ApJL. Higher resolution versions of finding charts are available at http://astro.uchicago.edu/~gates/findingchart

    Thermodynamics of nanodomain formation and breakdown in Scanning Probe Microscopy: Landau-Ginzburg-Devonshire approach

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    Thermodynamics of tip-induced nanodomain formation in scanning probe microscopy of ferroelectric films and crystals is studied using the Landau-Ginzburg-Devonshire phenomenological approach. The local redistribution of polarization induced by the biased probe apex is analyzed including the effects of polarization gradients, field dependence of dielectric properties, intrinsic domain wall width, and film thickness. The polarization distribution inside subcritical nucleus of the domain preceding the nucleation event is very smooth and localized below the probe, and the electrostatic field distribution is dominated by the tip. In contrast, polarization distribution inside the stable domain is rectangular-like, and the associated electrostatic fields clearly illustrate the presence of tip-induced and depolarization field components. The calculated coercive biases of domain formation are in a good agreement with available experimental results for typical ferroelectric materials. The microscopic origin of the observed domain tip elongation in the region where the probe electric field is much smaller than the intrinsic coercive field is the positive depolarization field in front of the moving counter domain wall. For infinitely thin domain walls local domain breakdown through the sample depth appears. The results obtained here are complementary to the Landauer-Molotskii energetic approach.Comment: 35 pages, 8 figures, suplementary attached, to be submitted to Phys. Rev.

    Magnetic and Structural Properties of Nd₂Fe₁₇₋ₓMnₓ Solid Solutions

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    A series of Nd2Fe17-xMnx solid solutions with x values between 0 and and 6 were prepared and analyzed using magnetic measurements, neutron diffraction, and Mössbauer spectroscopy. All of the Nd2Fe17-xMnx samples crystallized in the Th2Zn17-x-type rhombohedral structure. The lattice parameters and unit cell volumes decrease with increasing manganese content up to ∌ x equal to 2, and then increase for higher manganese content. The magnetizations of Nd2Fe17-xMnx decrease with increasing manganese content and Nd2Fe17-xMnx is paramagnetic at room temperature for x greater than 3. The Curie temperature in Nd2Fe17-xMnx solid solutions is maximum for x equal to 0.5 and decreases at a rate of ∌ 10° per substituted manganese up to x equal to 3, after which it drops sharply. These results are discussed in terms of the manganese she occupancies in Nd2Fe17-xMnx

    Assessing the perceived value of Reflexive Groups for supporting Clergy in the Church of England

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    This is an Accepted Manuscript of an article published by Taylor & Francis in Mental Health, Religion and Culture on 18-7-16, available online: http://dx.doi.org/10.1080/13674676.2016.1197194Little research has been conducted to assess the effectiveness of reïŹ‚exive groups in supporting clergy. For this research, eight Church of England Bishops’ Advisors for Pastoral Care and Counselling were interviewed to ascertain the value of reïŹ‚exive groups. These data were analysed using a thematic analysis. Two superordinate themes emerged: Contextual issues and BeneïŹts, along with 20 subordinate themes. An online survey, consisting of questions that came from the Bishops’ Advisors data, was then sent to reïŹ‚exive group participants (n=64), to see if their experiences matched those beneïŹts identiïŹed by the Bishops’ Advisors. The data from 37 participants was statistically analysed. The data from both sets of participants reveal that reïŹ‚exive groups are psychologically beneïŹcial to clergy. The research concludes that the implementation of reïŹ‚exive groups as a way of developing self-awareness and enculturating attitudes towards resilience and self-care is important to foster psychologically and spiritually healthy practice

    Introduction effort, climate matching and species traits as predictors of global establishment success in non-native reptiles

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    Non-native reptiles are often detrimental to native communities and ecosystems and can be extremely difficult to manage once established. Thus, there is considerable interest in predicting the likelihood of establishment of nonnative reptiles. We assessed three hypotheses describing possible factors contributing to the successful establishment of introduced reptiles in an effort to better identify potential invaders
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