Lessons from crossing symmetry at large N

20 pages, v2: Assumptions stated more clearly, version published in JHEPWe consider the four-point correlator of the stress tensor multiplet in N=4 SYM. We construct all solutions consistent with crossing symmetry in the limit of large central charge c ~ N^2 and large g^2 N. While we find an infinite tower of solutions, we argue most of them are suppressed by an extra scale \Delta_{gap} and are consistent with the upper bounds for the scaling dimension of unprotected operators observed in the numerical superconformal bootstrap at large central charge. These solutions organize as a double expansion in 1/c and 1/\Delta_{gap}. Our solutions are valid to leading order in 1/c and to all orders in 1/\Delta_{gap} and reproduce, in particular, instanton corrections previously found. Furthermore, we find a connection between such upper bounds and positivity constraints arising from causality in flat space. Finally, we show that certain relations derived from causality constraints for scattering in AdS follow from crossing symmetry.Peer reviewe

Large spin systematics in CFT

20 pages; v2: version published in JHEPUsing conformal field theory (CFT) arguments we derive an infinite number of constraints on the large spin expansion of the anomalous dimensions and structure constants of higher spin operators. These arguments rely only on analiticity, unitarity, crossing-symmetry and the structure of the conformal partial wave expansion. We obtain results for both, perturbative CFT to all order in the perturbation parameter, as well as non-perturbatively. For the case of conformal gauge theories this provides a proof of the reciprocity principle to all orders in perturbation theory and provides a new "reciprocity" principle for structure constants. We argue that these results extend also to non-conformal theories.Peer reviewe

Characterization and application of Bragg-edge transmission imaging for strain measurement and crystallographic analysis on the IMAT beamline

This paper presents a series of experiments to characterize the performance of the new IMAT beamline at the ISIS pulsed neutron source and provides examples to showcase the potential applications of Bragg-edge transmission imaging on the instrument. The characterization includes determination of the IMAT spectral and spatial resolutions through calibration measurements, and also determination of the precision and the accuracy of Bragg-edge analysis for lattice parameters of ceramics, metals and textured engineering alloys through high-temperature measurements. A novel Bragg-edge analysis method based on the cross-correlation of different Bragg edges has been developed to provide an estimate of the change in lattice parameter, which is especially useful for measurements of textured samples. Three different applications of the Bragg-edge transmission imaging technique are presented, including strain mapping, texture mapping and obtaining crystallographic information, i.e. the dependence on temperature of the Debye–Waller factor. The experimental results demonstrate the ability of the IMAT beamline to provide accurate strain measurements with uncertainties as low as 90 µ[epsilon] with reasonable measurement time, while characteristic materials parameters can be mapped across the sample with a spatial resolution of 300–600 µm for a strain map and down to ∼90 µm for a texture map

Changes in urinary metabolomic profile during relapsing renal vasculitis

Current biomarkers of renal disease in systemic vasculitis lack predictive value and are insensitive to early damage. To identify novel biomarkers of renal vasculitis flare, we analysed the longitudinal urinary metabolomic profile of a rat model of anti-neutrophil cytoplasmic antibody (ANCA) vasculitis. Wistar-Kyoto (WKY) rats were immunised with human myeloperoxidase (MPO). Urine was obtained at regular intervals for 181 days, after which relapse was induced by re-challenge with MPO. Urinary metabolites were assessed in an unbiased fashion using nuclear magnetic resonance (NMR) spectroscopy, and analysed using partial least squares discriminant analysis (PLS-DA) and partial least squares regression (PLS-R). At 56 days post-immunisation, we found that rats with vasculitis had a significantly different urinary metabolite profile than control animals; the observed PLS-DA clusters dissipated between 56 and 181 days, and re-emerged with relapse. The metabolites most altered in rats with active or relapsing vasculitis were trimethylamine N-oxide (TMAO), citrate and 2-oxoglutarate. Myo-inositol was also moderately predictive. The key urine metabolites identified in rats were confirmed in a large cohort of patients using liquid chromatography-mass spectrometry (LC-MS). Hypocitraturia and elevated urinary myo-inositol remained associated with active disease, with the urine myo-inositol:citrate ratio being tightly correlated with active renal vasculitis

Classical Conformal Blocks and Accessory Parameters from Isomonodromic Deformations

Classical conformal blocks naturally appear in the large central charge limit of 2D Virasoro conformal blocks. In the $AdS_{3}/CFT_{2}$ correspondence, they are related to classical bulk actions and are used to calculate entanglement entropy and geodesic lengths. In this work, we discuss the identification of classical conformal blocks and the Painlev\'e VI action showing how isomonodromic deformations naturally appear in this context. We recover the accessory parameter expansion of Heun's equation from the isomonodromic $\tau$-function. We also discuss how the $c = 1$ expansion of the $\tau$-function leads to a novel approach to calculate the 4-point classical conformal block.Comment: 32+10 pages, 2 figures; v3: upgraded notation, discussion on moduli space and monodromies, numerical and analytic checks; v2: added refs, fixed emai

The Fermi GBM Gamma-Ray Burst Spectral Catalog: Four Years Of Data

In this catalog we present the updated set of spectral analyses of GRBs detected by the Fermi Gamma-Ray Burst Monitor (GBM) during its first four years of operation. It contains two types of spectra, time-integrated spectral fits and spectral fits at the brightest time bin, from 943 triggered GRBs. Four different spectral models were fitted to the data, resulting in a compendium of more than 7500 spectra. The analysis was performed similarly, but not identically to Goldstein et al. 2012. All 487 GRBs from the first two years have been re-fitted using the same methodology as that of the 456 GRBs in years three and four. We describe, in detail, our procedure and criteria for the analysis, and present the results in the form of parameter distributions both for the observer-frame and rest-frame quantities. The data files containing the complete results are available from the High-Energy Astrophysics Science Archive Research Center (HEASARC).Comment: Accepted for publication in ApJ

The Effective Field Theory of Cosmological Large Scale Structures

Large scale structure surveys will likely become the next leading cosmological probe. In our universe, matter perturbations are large on short distances and small at long scales, i.e. strongly coupled in the UV and weakly coupled in the IR. To make precise analytical predictions on large scales, we develop an effective field theory formulated in terms of an IR effective fluid characterized by several parameters, such as speed of sound and viscosity. These parameters, determined by the UV physics described by the Boltzmann equation, are measured from N-body simulations. We find that the speed of sound of the effective fluid is c_s^2 10^(-6) and that the viscosity contributions are of the same order. The fluid describes all the relevant physics at long scales k and permits a manifestly convergent perturbative expansion in the size of the matter perturbations \delta(k) for all the observables. As an example, we calculate the correction to the power spectrum at order \delta(k)^4. The predictions of the effective field theory are found to be in much better agreement with observation than standard cosmological perturbation theory, already reaching percent precision at this order up to a relatively short scale k \sim 0.24 h/Mpc.Comment: v2: typos corrected, JHEP published versio

The quality of English-language websites offering falls-prevention advice to older members of the public and their families

Falls among older people are a major public health issue. Increasing numbers of older people are accessing the internet for health-related information, including information on falls risk and prevention. However, we are aware of no study that has assessed the quality of such websites. Using techniques for conducting systematic literature reviews, we evaluated English-language websites offering falls-related advice to members of the public. Forty-two websites were identified using popular search engines; these were assessed using evidence-based guidelines and codes of conduct on coverage of falls-related information, credibility and senior friendliness. Overall, scores were poor for coverage of falls information and credibility, although they were higher for senior friendliness. Few of the websites had been recently updated and none provided individually-tailored advice. We conclude that websites have fallen short of their potential to provide accessible, evidence-based information on the risks of falls and their prevention. © The Author(s) 2012

Measuring the Polarization of Boosted Hadronic Tops

We propose a new technique for measuring the polarization of hadronically decaying boosted top quarks. In particular, we apply a subjet-based technique to events where the decay products of the top are clustered within a single jet. The technique requires neither b-tagging nor W-reconstruction, and does not rely on assumptions about either the top production mechanism or the sources of missing energy in the event. We include results for various new physics scenarios made with different Monte Carlo generators to demonstrate the robustness of the technique.Comment: v2: version accepted for publication in JHE