Giant Holes

We study the semiclassical spectrum of excitations around a long spinning string in AdS_3. In addition to the usual small fluctuations, we find the spectrum contains a branch of solitonic excitations of finite energy. We determine the dispersion relation for these excitations. This has a relativistic form at low energies but also matches the dispersion relation for the "hole" of the dual gauge theory spin chain at high energies. The low-energy behaviour is consistent with the hypothesis that the solitonic excitations studied here are continuously related to the elementary excitations of the string.Comment: 17 pages, 1 figure; additional references include

Spiky strings and the AdS/CFT correspondence

In this dissertation, we explore some aspects of semiclassical type IIB string theory on AdS3 × S1 and on pure AdS3 in the limit of large angular momentum S. We first focus on the integrability technique known as finite-gap formalism for strings in AdS3 × S1, leading to the definition of a hyperelliptic Riemann surface, the spectral curve, which encodes, albeit in a rather implicit fashion, the semiclassical spectrum of a very large family of string solutions. Then, we show that, in the large angular momentum limit, the spectral curve separates into two distinct surfaces, allowing the derivation of an explicit expression for the spectrum, which is correspondingly characterised by two separate branches. The latter may be interpreted in terms of two kinds of spikes appearing on the strings: “large” spikes, yielding an infinite contribution to the energy and angular momentum of the string, and “small” spikes, representing finite excitations over the background of the “large” spikes. According to the AdS/CFT correspondence, strings moving in AdS3 × S1 should be dual to single trace operators in the sl(2) sector of N = 4 super Yang- Mills theory. The corresponding one-loop spectrum in perturbation theory may also be computed through integrability methods and, in the large conformal spin limit S → ∞ (equivalent to the AdS3 angular momentum in string theory) is also expressed in terms of a spectral curve and characterised in terms of the so-called holes. We show that, with the appropriate identifications and with the usual extrapolation from weak to strong ’t Hooft coupling described by the cusp anomalous dimension, the large-S spectra of gauge theory and of string theory coincide. Furthermore, we explain how “small” and “large” holes may be identified with “small” and “large” spikes. Finally, we discuss several explicit spiky string solutions in AdS3 which, at the leading semiclassical order, display the previously studied finite-gap spectrum. We compute the spectral curves of these strings in the large S limit, finding that they correspond to specific regions of the moduli space of the finite-gap curves. We also explain how “large” spikes may be used in order to extract a discrete system of degrees of freedom from string theory, which can then be matched with the degrees of freedom of the dual gauge theory operators, and how “small” spikes are in fact very similar to the Giant Magnons living in R × S2.Domestic Research Scholarship (fees only); Cambridge European Trust and Isaac Newton Trust (Isaac Newton Trust European Research Studentship)

Spiky Strings and Giant Holes

We analyse semiclassical strings in AdS in the limit of one large spin. In this limit, classical string dynamics is described by a finite number of collective coordinates corresponding to spikes or cusps of the string. The semiclassical spectrum consists of two branches of excitations corresponding to "large" and "small" spikes respectively. We propose that these states are dual to the excitations known as large and small holes in the spin chain description of N=4 SUSY Yang-Mills. The dynamics of large spikes in classical string theory can be mapped to that of a classical spin chain of fixed length. In turn, small spikes correspond to classical solitons propagating on the background formed by the large spikes. We derive the dispersion relation for these excitations directly in the finite gap formalism.Comment: 36 pages, 9 figure

Association between common cardiovascular risk factors and clinical phenotype in patients with hypertrophic cardiomyopathy from the European Society of Cardiology (ESC) EurObservational Research Programme (EORP) Cardiomyopathy/Myocarditis registry

© The Author(s) 2022. Published by Oxford University Press on behalf of the European Society of Cardiology. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.Aims: The interaction between common cardiovascular risk factors (CVRF) and hypertrophic cardiomyopathy (HCM) is poorly studied. We sought to explore the relation between CVRF and the clinical characteristics of patients with HCM enrolled in the EURObservational Research Programme (EORP) Cardiomyopathy registry. Methods and results: 1739 patients with HCM were studied. The relation between hypertension (HT), diabetes (DM), body mass index (BMI) and clinical traits was analyzed. Analyses were stratified according to the presence or absence of a pathogenic variant in a sarcomere gene.The prevalence of HT, DM and obesity (Ob) was 37%, 10%, and 21%, respectively. HT, DM and Ob were associated with older age (p<0.001), less family history of HCM (HT and DM p<0.001), higher New York Heart Association (NYHA) class (p<0.001), atrial fibrillation (HT and DM p<0.001; Ob p = 0.03) and LV (left ventricular) diastolic dysfunction (HT and Ob p<0.001; DM p = 0.003). Stroke was more frequent in HT (p<0.001) and mutation-positive patients with DM (p = 0.02). HT and Ob were associated with higher provocable LV outflow tract gradients (HT p<0.001, Ob p = 0.036). LV hypertrophy was more severe in Ob (p = 0.018). HT and Ob were independently associated with NYHA class (OR 1.419, p = 0.017 and OR 1.584, p = 0.004, respectively). Other associations, including a higher proportion of females in HT and of systolic dysfunction in HT and Ob, were observed only in mutation-positive patients. Conclusion: Common CVRF are associated with a more severe HCM phenotype, suggesting a proactive management of CVRF should be promoted. An interaction between genotype and CVRF was observed for some traits.info:eu-repo/semantics/publishedVersio

Diagnostic performance of FibroTest, SteatoTest and ActiTest in patients with NAFLD using the SAF score as histological reference

BACKGROUND: Blood tests of liver injury are less well validated in non‐alcoholic fatty liver disease (NAFLD) than in patients with chronic viral hepatitis. AIMS: To improve the validation of three blood tests used in NAFLD patients, FibroTest for fibrosis staging, SteatoTest for steatosis grading and ActiTest for inflammation activity grading. METHODS: We pre‐included new NAFLD patients with biopsy and blood tests from a single‐centre cohort (FibroFrance) and from the multicentre FLIP consortium. Contemporaneous biopsies were blindly assessed using the new steatosis, activity and fibrosis (SAF) score, which provides a reliable and reproducible diagnosis and grading/staging of the three elementary features of NAFLD (steatosis, inflammatory activity) and fibrosis with reduced interobserver variability. We used nonbinary‐ROC (NonBinAUROC) as the main endpoint to prevent spectrum effect and multiple testing. RESULTS: A total of 600 patients with reliable tests and biopsies were included. The mean NonBinAUROCs (95% CI) of tests were all significant (P < 0.0001): 0.878 (0.864–0.892) for FibroTest and fibrosis stages, 0.846 (0.830–0.862) for ActiTest and activity grades, and 0.822 (0.804–0.840) for SteatoTest and steatosis grades. FibroTest had a higher NonBinAUROC than BARD (0.836; 0.820–0.852; P = 0.0001), FIB4 (0.845; 0.829–0.861; P = 0.007) but not significantly different than the NAFLD score (0.866; 0.850–0.882; P = 0.26). FibroTest had a significant difference in median values between adjacent stage F2 and stage F1 contrarily to BARD, FIB4 and NAFLD scores (Bonferroni test P < 0.05). CONCLUSIONS: In patients with NAFLD, SteatoTest, ActiTest and FibroTest are non‐invasive tests that offer an alternative to biopsy, and they correlate with the simple grading/staging of the SAF scoring system across the three elementary features of NAFLD: steatosis, inflammatory activity and fibrosis

On the Chemical Composition and Hygroscopicity of Aerosols Deposited on the Insulators of Italian Power Lines

The reliability of the national power grid is a key issue in modern society. Atmospheric aerosols are the main cause of the reduction in the performance of insulators and the increase in the possibility of flashovers, resulting in power line failures. Under high ambient humidity, the water-soluble compounds of atmospheric aerosols collected on the insulators’ surface can dissociate in ions and form a conductive layer, which may lead to flashover events. With a view to investigating the processes that drive these phenomena, the chemical composition of aerosol deposits on insulators in Italy was determined by ion chromatography analysis and thermos-optical and X-ray techniques. In addition, a synthetic aerosol with the same analyzed chemical composition was generated in a laboratory and deposited on PTFE filters and glass specimens allowing us to determine the deliquescence and crystallization relative humidity and the conductive effect in an aerosol exposure chamber. The results evidenced the presence of a hazardous inorganic ion layer, which generates a sharp phase transition of the aerosol deposit as a function of the ambient relative humidity; this layer poses a dangerous threat to the reliability of the power grid, increasing the probability of flashover events where the conductive layer facilitates the flow of electrical current across the insulator surface, potentially causing power outages or damage to the power lines