Quantum and classical criticality in a dimerized quantum antiferromagnet

A quantum critical point (QCP) is a singularity in the phase diagram arising due to quantum mechanical fluctuations. The exotic properties of some of the most enigmatic physical systems, including unconventional metals and superconductors, quantum magnets, and ultracold atomic condensates, have been related to the importance of the critical quantum and thermal fluctuations near such a point. However, direct and continuous control of these fluctuations has been difficult to realize, and complete thermodynamic and spectroscopic information is required to disentangle the effects of quantum and classical physics around a QCP. Here we achieve this control in a high-pressure, high-resolution neutron scattering experiment on the quantum dimer material TlCuCl3. By measuring the magnetic excitation spectrum across the entire quantum critical phase diagram, we illustrate the similarities between quantum and thermal melting of magnetic order. We prove the critical nature of the unconventional longitudinal ("Higgs") mode of the ordered phase by damping it thermally. We demonstrate the development of two types of criticality, quantum and classical, and use their static and dynamic scaling properties to conclude that quantum and thermal fluctuations can behave largely independently near a QCP.Comment: 6 pages, 4 figures. Original version, published version available from Nature Physics websit

The Familial Clustering of Age at Menarche in Extended Twin Families

The timing of puberty is complex, possibly involving many genetic factors that may interact with environmental influences. Familial resemblance for age at menarche was studied in a sample of 4,995 female twins, 1,296 sisters, 2,946 mothers and 635 female spouses of male twins. They had indicated their age at menarche as part of a larger longitudinal survey. We assessed assortative mating for age at menarche, gene–environment interaction effects and estimated the heritability of individual differences in pubertal timing. There was significant evidence of gene–environment interaction, accounting for 1.5% of the variance. There was no indication of consistent mate assortment on age at menarche. Individual differences in age at menarche are highly heritable, with additive genetic factors explaining at least 70% of the true variation. An additional 1.5% of the variation can be explained by a genotype–environment interaction effect where environmental factors are more important in individuals genetically predisposed for late menarche

The Formation of the First Massive Black Holes

Supermassive black holes (SMBHs) are common in local galactic nuclei, and SMBHs as massive as several billion solar masses already exist at redshift z=6. These earliest SMBHs may grow by the combination of radiation-pressure-limited accretion and mergers of stellar-mass seed BHs, left behind by the first generation of metal-free stars, or may be formed by more rapid direct collapse of gas in rare special environments where dense gas can accumulate without first fragmenting into stars. This chapter offers a review of these two competing scenarios, as well as some more exotic alternative ideas. It also briefly discusses how the different models may be distinguished in the future by observations with JWST, (e)LISA and other instruments.Comment: 47 pages with 306 references; this review is a chapter in "The First Galaxies - Theoretical Predictions and Observational Clues", Springer Astrophysics and Space Science Library, Eds. T. Wiklind, V. Bromm & B. Mobasher, in pres

Combination of searches for heavy spin-1 resonances using 139 fb−1 of proton-proton collision data at √s = 13 TeV with the ATLAS detector

A combination of searches for new heavy spin-1 resonances decaying into diferent pairings of W, Z, or Higgs bosons, as well as directly into leptons or quarks, is presented. The data sample used corresponds to 139 fb−1 of proton-proton collisions at √ s = 13 TeV collected during 2015–2018 with the ATLAS detector at the CERN Large Hadron Collider. Analyses selecting quark pairs (qq, bb, tt¯, and tb) or third-generation leptons (τν and τ τ ) are included in this kind of combination for the frst time. A simplifed model predicting a spin-1 heavy vector-boson triplet is used. Cross-section limits are set at the 95% confdence level and are compared with predictions for the benchmark model. These limits are also expressed in terms of constraints on couplings of the heavy vector-boson triplet to quarks, leptons, and the Higgs boson. The complementarity of the various analyses increases the sensitivity to new physics, and the resulting constraints are stronger than those from any individual analysis considered. The data exclude a heavy vector-boson triplet with mass below 5.8 TeV in a weakly coupled scenario, below 4.4 TeV in a strongly coupled scenario, and up to 1.5 TeV in the case of production via vector-boson fusion

Accuracy versus precision in boosted top tagging with the ATLAS detector

Abstract The identification of top quark decays where the top quark has a large momentum transverse to the beam axis, known as top tagging, is a crucial component in many measurements of Standard Model processes and searches for beyond the Standard Model physics at the Large Hadron Collider. Machine learning techniques have improved the performance of top tagging algorithms, but the size of the systematic uncertainties for all proposed algorithms has not been systematically studied. This paper presents the performance of several machine learning based top tagging algorithms on a dataset constructed from simulated proton-proton collision events measured with the ATLAS detector at √ s = 13 TeV. The systematic uncertainties associated with these algorithms are estimated through an approximate procedure that is not meant to be used in a physics analysis, but is appropriate for the level of precision required for this study. The most performant algorithms are found to have the largest uncertainties, motivating the development of methods to reduce these uncertainties without compromising performance. To enable such efforts in the wider scientific community, the datasets used in this paper are made publicly available.</jats:p

Search for light long-lived particles in pp collisions at √s = 13 TeV using displaced vertices in the ATLAS inner detector

A search for long-lived particles (LLPs) using 140 fb−1 of pp collision data with √s = 13 TeV recorded by the ATLAS experiment at the LHC is presented. The search targets LLPs with masses between 5 and 55 GeV that decay hadronically in the ATLAS inner detector. Benchmark models with LLP pair production from exotic decays of the Higgs boson and models featuring long-lived axionlike particles (ALPs) are considered. No significant excess above the expected background is observed. Upper limits are placed on the branching ratio of the Higgs boson to pairs of LLPs, the cross section for ALPs produced in association with a vector boson, and, for the first time, on the branching ratio of the top quark to an ALP and a u/c quark

Toltrazuril treatment of congenitally acquired Neospora caninum infection in newborn mice

C57BL/6 mice were infected with Neospora caninum tachyzoites during pregnancy, yielding a transplacental infection of developing fetuses. Subsequently, congenitally infected newborn mice were treated either once or three times with toltrazuril (or placebo) at a concentration of 31.25 mg compound per kg body weight. Both toltrazuril and placebo treatment had no negative effect on newborns, as noninfected treated pups developed normally without differences in mortality and morbidity to matching nontreated control animals. Already one application of toltrazuril was significantly (p < 0.01) able to delay the outbreak of neosporosis in newborn mice, when compared to placebo-treated infected controls. We found significantly higher proportion of surviving newborns in one-time-toltrazuril-treated and three-time-toltrazuril-treated groups (34% and 54%, respectively) when compared to one-time-placebo-treated and three-time-placebo-treated groups (14% and 30%, respectively). There was no significant difference (p = 0.2) in the proportion of surviving pups between one-time-toltrazuril and three-time-toltrazuril treatment. However, the number of diseased and Neospora-positive pups (46% and 47%, respectively) was markedly reduced after three-time-toltrazuril treatment compared to all other groups. Three-time-treatment also resulted in the highest antibody (IgG, IgG2a) response. Pharmacokinetic analyses using individual serum samples revealed that, although toltrazuril was absorbed and metabolized to toltrazuril sulfone by newborn mice, medicated animals exhibited an unexpected rapid turn-over (half-life time) of the compound. Toltrazuril and the metabolite were also found in brain tissues, indicating that passage of the blood-brain barrier occurred. In conclusion, we could show that three times treatment with toltrazuril had a high impact on the course of infection in congenitally N. caninum-infected newborn mice

Study on viscosity modification of human and formula milk for infants with dysphagia

Objetivo: analisar o leite humano e a fórmula láctea infantil com a viscosidade modificada. Métodos: foram realizados três estudos considerando a viscosidade e efeito do tempo na fórmula nas concentrações 2, 3 e 5% e no leite humano cru e pasteurizado nas concentrações 2, 3, 5 e 7% na temperatura de 37ºC pelo tempo de 60 minutos. O cereal de arroz foi utilizado como agente espessante. A viscosidade foi avaliada pelo viscosímetro do tipo Copo Ford e as amostras analisadas em quatro intervalos de tempo. Diferenças significativas foram avaliadas por meio do teste da Anova. Resultados: não foram observadas diferenças significativas da viscosidade em relação ao tempo para as concentrações de 2, 3 e 5%. Observou-se diferença na viscosidade entre leite humano e fórmula nas concentrações de 2% e 5%, 2% e 7%, 3% e 5%, e 3% e 7%, independente dos intervalos de tempo considerados. Conclusão: o estudo aponta para a necessidade de diferentes concentrações para leite humano e fórmula. O cereal de arroz apresenta-se como opção terapêutica adequada para os recém-nascidos com disfagia nas concentrações de 2, 3, 5 e 7% pelo seu efeito na viscosidade e redução do fluxo, desde que se observe o tempo de mamada.Purpose: to analyze the modification of the viscosity of human milk and infant formula. Methods: three studies were performed to assess the viscosity and effect of time on infant formula with a thickener, at concentrations of 2, 3, and 5%, as well as raw and pasteurized human milk at concentrations of 2, 3, 5, and 7% at 37ºC, for 60 minutes. Rice cereal was used as a thickening agent. The viscosity was evaluated using a Ford Cup-type viscometer, and the samples were analyzed at 20-minute intervals. Significant differences were assessed using the ANOVA test. Results: no significant differences in viscosity were observed over time in concentrations of 2, 3, and 5%. There was a difference in the viscosity between human milk and infant formula, in concentrations of 2% and 5%, 2% and 7%, 3% and 5%, and 3% and 7%, independently of the time intervals evaluated. Conclusion: the findings of this study demonstrate the need for different concentrations of the thickening agent for human milk and infant formula. Rice cereal is a suitable therapeutic option for newborns presented with dysphagia in concentrations of 2, 3, 5, and 7%, due to its effect on the viscosity and flow reduction, provided that the feeding time is considered