Impact of QCD jets and heavy-quark production in cosmic-ray proton atmospheric showers up to 1020^{20} eV

The PYTHIA 6 Monte Carlo (MC) event generator, commonly used in collider physics, is interfaced for the first time with a fast transport simulation of a hydrogen atmosphere, with the same density as air, in order to study the properties of extended atmospheric showers (EAS) produced by cosmic ray protons with energies E$_{CR}\approx 10^{14}$--$10^{20}$ eV. At variance with the hadronic MC generators (EPOS-LHC, QGSJET, and SIBYLL) commonly used in cosmic-rays physics, PYTHIA includes the generation of harder hadronic jets and heavy (charm and bottom) quarks, thereby producing higher transverse momentum final particles, that could explain several anomalies observed in the data. The electromagnetic, hadronic, and muonic properties of EAS generated with various settings of PYTHIA 6, tuned to proton-proton data measured at the LHC, are compared to those from EPOS-LHC, QGSJET 01, QGSJET II, and SIBYLL 2.1. Despite their different underlying parton dynamics, the characteristics of the EAS generated with PYTHIA 6 are in between those predicted by the rest of MC generators. The only exceptions are the muonic components at large transverse distances from the shower axis, where PYTHIA predicts more activity than the rest of the models. Heavy-quark production, as implemented in this study for a hydrogen atmosphere, does not seem to play a key role in the EAS muon properties, pointing to nuclear effects as responsible of the muon anomalies observed in the air-shower data.Comment: 13 pages, 20 figure

An improved Noether's theorem for spacetime symmetries

We exploit an ambiguity somewhat hidden in Noether's theorem to derive systematically, for relativistic field theories, the stress-energy tensor's improvement terms that are associated with additional spacetime symmetries beyond translations. We work out explicitly the cases of Lorentz invariance, scale invariance, and full conformal invariance. The main idea is to use, directly in the translation Noether theorem, the fact that these additional symmetries can be thought of as suitably modulated translations. Compared to more standard derivations of the improvement terms, ours (1) unifies all different cases in a single framework, (2) involves no guesswork, (3) yields the desired algebraic properties (symmetry and/or tracelessness) of the stress-energy tensor off-shell, and (4) unifies the translation Noether theorem with those of the additional spacetime symmetries, yielding at the same time both the improved stress-energy tensor and the additional Noether currents.Comment: 17 page

Hospitalization Costs of COVID-19 Cases and Their Associated Factors in Guangdong, China: A Cross-Sectional Study

Background: The ongoing COVID-19 pandemic has brought significant challenges to health system and consumed a lot of health resources. However, evidence on the hospitalization costs and their associated factors in COVID-19 cases is scarce.Objectives: To describe the total and components of hospitalization costs of COVID-19 cases, and investigate the associated factors of costs.Methods: We included 876 confirmed COVID-19 cases admitted to 33 designated hospitals from January 15th to April 27th, 2020 in Guangdong, China, and collected their demographic and clinical information. A multiple linear regression model was performed to estimate the associations of hospitalization costs with potential associated factors.Results: The median of total hospitalization costs of COVID-19 cases was $2,869.4 (IQR:$3,916.8). We found higher total costs in male (% difference: 29.7, 95% CI: 15.5, 45.6) than in female cases, in older cases than in younger ones, in severe cases (% difference: 344.8, 95% CI: 222.5, 513.6) than in mild ones, in cases with clinical aggravation than those without, in cases with clinical symptoms (% difference: 47.7, 95% CI: 26.2, 72.9) than those without, and in cases with comorbidities (% difference: 21.1%, 21.1, 95% CI: 4.4, 40.6) than those without. We also found lower non-pharmacologic therapy costs in cases treated with traditional Chinese medicine (TCM) therapy (% difference: −47.4, 95% CI: −64.5 to −22.0) than cases without.Conclusion: The hospitalization costs of COVID-19 cases in Guangdong were comparable to the national level. Factors associated with higher hospitalization costs included sex, older age, clinical severity and aggravation, clinical symptoms and comorbidities at admission. TCM therapy was found to be associated with lower costs for some non-pharmacologic therapies

Charm and Bottom Contributions to Muon Production in Ultra-high Energy Cosmic-ray Showers

Current Monte Carlos used in cosmic ray shower simulations suffers a lack of muon production compared with measured value. With charm and bottom quarks taken into consideration, PYTHIA in a hydrogen atmosphere was expected to produce more muons compares with other models, therefore simulations were carried out using various models for comparison. However, the plots shows that PYTHIA does not stand out in muon production. Some analysis was carried out and further investigations are needed

A symmetry’s tale: from the material to the celestial

Symmetry has played a crucial role in our understanding of physical systems. In this thesis, we review several works based on investigating the symmetry properties of theories. We examine and improve the Noether's theorem and the coset construction, both powerful tools when studying the symmetry aspects of a physical system. We manipulate the intrinsic ambiguities in the derivation of the stress-energy tensor using Noether's theorem to systematically compute, without any guesswork, the necessary ``improvement terms'' which make the tensor satisfy certain algebraic properties such as symmetry and tracelessness, even off-shell. We then construct a new type of coset construction, which can accommodate relativistic particles with arbitrary spins. This is the first work we know of to incorporate arbitrary spin degrees of freedom into coset construction. We then present two interesting examples of condensed matter systems described by effective field theories that come from spontaneous symmetry breaking. For the so-called framid, we present the peculiar behavior of its stress-energy tensor that it is Lorentz-invariant even though the system breaks Lorentz boosts spontaneously. An analogy is drawn to the cosmological constant problem since the vacuum energy there and the Lorentz-breaking terms here are all surprisingly zero. Lastly, we describe how the inflation of the universe can be driven by a solid. We focus on the icosahedral inflation model, where the isotropies of background evolution and scalar power spectrum are guaranteed although the system is anisotropic. We discuss some observational signatures of this model

3D Pose Recognition of Small Special-Shaped Sheet Metal with Multi-Objective Overlapping

This paper addresses the challenging task of determining the position and posture of small-scale thin metal parts with multi-objective overlapping. To tackle this problem, we propose a method that utilizes instance segmentation and a three-dimensional (3D) point cloud for recognizing the posture of thin special-shaped metal parts. We investigate the process of obtaining a single target point cloud by aligning the target mask with the depth map. Additionally, we explore a pose estimation method that involves registering the target point cloud with the model point cloud, designing a registration algorithm that combines the sample consensus initial alignment algorithm (SAC-IA) for coarse registration and the iterative closest point (ICP) algorithm for fine registration. The experimental results demonstrate the effectiveness of our approach. The average accuracy of the instance segmentation models, utilizing ResNet50 + FPN and ResNet101 + FPN as backbone networks, exceeds 97%. The time consumption of the ResNet50 + FPN model is reduced by 50%. Furthermore, the registration algorithm, which combines the SAC-IA and ICP, achieves a lower average consumption time while satisfying the requirements for the manufacturing of new energy batteries