Hasil untuk "Physics"

James F. Steiner, Edward Nathan, Kun Hu et al.

We present the first X-ray spectropolarimetric results for Cygnus X-1 in its soft state from a campaign of five IXPE observations conducted during 2023 May–June. Companion multiwavelength data during the campaign are likewise shown. The 2–8 keV X-rays exhibit a net polarization degree PD = 1.99% ± 0.13% (68% confidence). The polarization signal is found to increase with energy across the Imaging X-ray Polarimetry Explorer’s (IXPE) 2–8 keV bandpass. The polarized X-rays exhibit an energy-independent polarization angle of PA = −25.°7 ± 1.°8 east of north (68% confidence). This is consistent with being aligned to Cyg X-1’s au-scale compact radio jet and its parsec-scale radio lobes. In comparison to earlier hard-state observations, the soft state exhibits a factor of 2 lower polarization degree but a similar trend with energy and a similar (also energy-independent) position angle. When scaling by the natural unit of the disk temperature, we find the appearance of a consistent trend line in the polarization degree between the soft and hard states. Our favored polarimetric model indicates that Cyg X-1’s spin is likely high ( a _* ≳ 0.96). The substantial X-ray polarization in Cyg X-1's soft state is most readily explained as resulting from a large portion of X-rays emitted from the disk returning and reflecting off the disk surface, generating a high polarization degree and a polarization direction parallel to the black hole spin axis and radio jet. In IXPE’s bandpass, the polarization signal is dominated by the returning reflection emission. This constitutes polarimetric evidence for strong gravitational lensing of X-rays close to the black hole.

Liu Shenghua, Jamieson Nathan, Lannon Kevin et al.

An increasingly frequent challenge faced in HEP data analysis is to characterize the agreement between a prediction that depends on a dozen or more model parameters—such as predictions coming from an effective field theory (EFT) framework—and the observed data. Traditionally, such characterizations take the form of a negative log likelihood (NLL) function, which can only be evaluated numerically. The lack of a closed-form description of the NLL function makes it difficult to convey results of the statistical analysis. Typical results are limited to extracting “best fit” values of the model parameters and 1D intervals or 2D contours extracted from scanning the higher dimensional parameter space. It is desirable to explore these high-dimensional model parameter spaces in more sophisticated ways. One option for overcoming this challenge is to use a neural network to approximate the NLL function. This approach has the advantage of being continuous and differentiable by construction, which are essential properties for an NLL function and may also provide useful handles in exploring the NLL as a function of the model parameters. In this talk, we describe the advantages and limitations of this approach in the context of applying it to a CMS data analysis using the framework of EFT.

Germán Rodrigo

We motivate the use of quantum algorithms in particle physics and provide a brief overview of the most recent applications at high-energy colliders. In particular, we discuss in detail how a quantum approach reduces the complexity of jet clustering algorithms, such as anti-kT , and show how quantum algorithms efficiently identify causal configurations of multiloop Feynman diagrams. We also present a quantum integration algorithm, called QFIAE, which is successfully applied to the evaluation of one-loop Feynman integrals in a quantum simulator or in a real quantum device.

Huibin Qiu, Zuozhi Hu, Shengfa Wu et al.

Qiyuan Dai, Liang Ma, Li Li et al.

Using finite element calculations, we investigated the near field properties of two types of commonly used metal nanostructures (a tip-substrate model representing a scanning tunneling microscope type setup (TS) and a nanoparticle-on-mirror (NPoM) configuration) with atomic sharpness and extreme focusing capabilities. The spatial confinement and electric field enhancement of the local field as well as the fluorescence quantum efficiency of a model molecule (as represented by an oscillating dipole) in the cavity region of the two models were systematically studied. It was found that the TS model tends to support higher local electric field enhancement while the NPoM model can provide a more localized plasmon electric field near the nanoparticle. Calculations with the radiating model molecule indicate that both TS and NPoM can cause significant enhancements to the non-radiative decay rates at the order of 106 in the wavelength range of 500–1000 nm. The TS model shows better performance for the radiative enhancements and the resulting emission quantum yield. These results are not only helpful to improve the understanding of such important nanocavities but also supply a reference for their further applications in different areas.

Mohammad Talafha, Sora Kim, Kyung-Suk Suh

Numerical simulations of atmospheric dispersion and dose assessment were performed for the Jordan Research and Training Reactor (JRTR) to evaluate its radiological effects on surrounding population and the environment. A three-dimensional atmospheric dispersion model was applied to investigate the behavior of the radionuclides released into the air, and a dose assessment model was used to estimate the radiological impact on the population residing in nearby cities around the JRTR. Considering full core meltdown an accidental scenario, most of the source term was assumed to be released from the JRTR. Simulations were performed to calculate the air and deposition concentrations of radioactive materials for July 2013 and January 2014. The monthly averaged values of concentrations, depositions, and dose rates were analyzed to identify the most harmful effects in each month. The results showed that relatively harmful effects occurred in January 2014, and the total annual dose rate was estimated to be approximately 1 mSv outside the 10 km radius from JRTR. However, the impact of a nuclear accident is not as severe as it might seem, as the affected area is not highly populated, and appropriate protective measures can significantly reduce the radiation exposure. This study provides useful information for emergency preparedness and response planning to mitigate the radiological consequences of a nuclear accident at the JRTR.

Li-Xin Guo, Meng-Long Hsieh, Olga Gorodetskaya et al.

Abstract The Yellow River Plain (YRP), being regarded as the cradle of Chinese civilization, is traditionally thought to be the locale of the Great Flood, a hazardous flood (or floods) tamed by Yu who started China’s first “dynasty”, Xia, in ~ 2000 BC. However, by integrating published archaeological data, we propose that the Great Flood in fact impacted the Jianghan Plain (JHP) along the middle course of the Yangtze River. The arguments include: (1) around the era of the Great Flood, the most civilized and populated society in East Asia, named the Jianghan society, was located around the JHP (at that time, the habitation on the YRP remained limited); (2) the Jianghan society lived on river resources (shipping and rice growing) and was thus subject to flood risks (but not for the people inhabiting the YRP); (3) the people in the Jianghan society were experienced in dredging moats/ditches for shipping and irrigation; (4) unlike the floods on the YRP that were characterized by dynamic sedimentation and channel avulsion, those on the JHP typically occurred with slow-moving water manageable to ancient people; (5) the JHP has been associated with lake/wetland systems serving as detention basins during floods. Here, the recorded method for controlling the Great Flood, dredging channels to divert flood water to a “sea”, was feasible. Known speleothem paleo-rainfall data from multiple sites show that the climate of the JHP had been wet since the middle Holocene (earlier than the era of the Great Flood) and significantly turned dry after ~ 1850 BC (~ 150 years later than the Great Flood). Thus, the uniqueness of the Great Flood was likely to reflect an increase in land use on the JHP with the expansion of the Jianghan society, and the success in taming this flood was mainly due to the efforts of the society, not by luck.

Alexandre Landry, Robert J. van den Hoogen

A complete perturbation theory suitable for teleparallel gravity is developed. The proposed perturbation scheme takes into account perturbations of the coframe, the metric, and the spin-connection, while ensuring that the resulting perturbed system continues to describe a teleparallel gravity situation. The resulting perturbation scheme can be transformed to one in which perturbations all take place within the co-frame. A covariant definition of a teleparallel Minkowski geometry is proposed. We compute the perturbed field equations for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>f</mi><mo>(</mo><mi>T</mi><mo>)</mo></mrow></semantics></math></inline-formula> teleparallel gravity and discuss the stability of the teleparallel Minkowski geometry within <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>f</mi><mo>(</mo><mi>T</mi><mo>)</mo></mrow></semantics></math></inline-formula> teleparallel gravity.

Marilena Cozzolino, Antonio De Simone, Vincenzo Gentile et al.

The application of non-invasive geophysical techniques and digital surveys to explore cultural heritage is becoming a very important research field. The capability to detect inner and superficial changes in the inspected surfaces allows for imaging spatial inhomogeneity and material features and planning targeted conservation and restoration interventions. In this work, the results of a research project carried out on the famous Battle of Issus Mosaic, also known as the “Alexander Mosaic”, are presented. It is a masterpiece of ancient art that was found in 1831 in the House of Faun, the most luxurious and spacious house in Pompeii. It is notable for its size (3.41 × 5.82 m), the quality of workmanship and the subject that represents the culminating phase of the battle between Alexander Magno’s army and the Persian one of Darius. In 1916, it was moved inside the National Archaeological Museum of Naples, where the original horizontal location was changed with a vertical arrangement supported by an inner wooden structure, whose exact manufacture is unclear. Today, the mosaic is affected by important instability phenomena highlighted by the appearance of the significant detachment of tiles, superficial lesions and swelling of the surface. Given the important need to preserve it, a high-detail diagnostic study was realized through a digital survey and non-invasive geophysical surveys using ground-penetrating radar (GPR). The investigation was repeated after two years, in 2018 and 2020, with the aim of verifying the evolution of degradation. The work provided a high-resolution estimate of the state of the health of the mosaic and allowed for obtaining a three-dimensional reconstruction of the internal mosaic structure, including the formulation of hypotheses on the engineering supporting works of the twentieth century; this provides an essential tool for the imminent conservation project, which also implies restoring the original horizontal position.

Yijing Chu, Ming Wu, Hongling Sun

Active noise and vibration control aims at attenuating unwanted sound or vibration by automatically generating an anti-sound or vibration [...]

J. Klusoň

Abstract We study string theory with momentum living on de Sitter space. We argue that consistency of the theory implies that the global momentum can be defined on de Sitter space. Then we perform careful canonical analysis and we we also show that this presumption leads to the string with deformed dispersion relation.

Kharanshu Solanki

This paper examines the incommensurability thesis - one of the most important and controversial ideas to emerge from the simultaneous work of Kuhn and Feyerabend. In the first half, I discuss three aspects of incommensurability - methodological incommensurability (the view that each paradigm supplies different standards of evaluation), observational incommensurability (the view that the theories we accept alter how we see the world), and finally, semantic incommensurability (which claims that as paradigms change, the very meanings of central theoretical terms also change). In the latter half, I tackle the general arguments of physicists against incommensurability by primarily considering the so called unifying cube of physics. I show that the cube of physics does not get rid of incommensurability, but rather favours it.

Ben Van Dusen, Christoph Vogelsang, Joseph Taylor et al.

Preparing future physics teachers for the demanding nature of their profession is an important and complex endeavor. Teacher education systems must provide a structure for the coherent professional development of prospective teachers. Worldwide, physics teacher education is organized in different ways, but have to face similar challenges, like the relation between academic studies and practical preparation. To meet these challenges, it is worth taking look at different teacher education systems. In this chapter, we compare physics teacher education in two countries, representing two different educational traditions: Germany and the USA. Comparing different aspects of physics teacher education (standards, organization and institutionalization, content of teacher education, quality assurance), we describe both systems in their current state and why they are organized in the way they are. In doing so, we identify surprising commonalities but also different opportunities for both systems to learn from each other.

Nikolay Bobev, Emanuel Malek, Brandon Robinson et al.

Abstract We apply recently developed tools from exceptional field theory to calculate the full Kaluza-Klein spectrum of the AdS5 Pilch-Warner solution of type IIB supergravity. Through the AdS/CFT correspondence this yields detailed information about the spectrum of protected and unprotected operators of the four-dimensional N $$ \mathcal{N} $$ = 1 Leigh-Strassler SCFT, in the planar limit. We also calculate explicitly the superconformal index of the SCFT in this limit and show that it agrees precisely with the spectrum of protected operators in the supergravity calculation.

A. Matzkin

We connect the weak measurements framework to the path integral formulation of quantum mechanics. We show how Feynman propagators can in principle be experimentally inferred from weak value measurements. We also obtain expressions for weak values parsing unambiguously the quantum and the classical aspects of weak couplings between a system and a probe. These expressions are shown to be useful in quantum-chaos-related studies (an illustration involving quantum scars is given), and also in solving current weak-value-related controversies (we discuss the existence of discontinuous trajectories in interferometers and the issue of anomalous weak values in the classical limit).

Marco Villani, Salvatore Magrì, Andrea Roli et al.

Living beings share several common features at the molecular level, but there are very few large-scale &#8220;operating principles&#8221; which hold for all (or almost all) organisms. However, biology is subject to a deluge of data, and as such, general concepts such as this would be extremely valuable. One interesting candidate is the &#8220;criticality&#8221; principle, which claims that biological evolution favors those dynamical regimes that are intermediaries between ordered and disordered states (i.e., &#8220;at the edge of chaos&#8221;). The reasons why this should be the case and experimental evidence are briefly discussed, observing that gene regulatory networks are indeed often found on, or close to, the critical boundaries. Therefore, assuming that criticality provides an edge, it is important to ascertain whether systems that are critical can further evolve while remaining critical. In order to explore the possibility of achieving such &#8220;always-critical&#8221; evolution, we resort to simulated evolution, by suitably modifying a genetic algorithm in such a way that the newly-generated individuals are constrained to be critical. It is then shown that these modified genetic algorithms can actually develop critical gene regulatory networks with two interesting (and quite different) features of biological significance, involving, in one case, the average gene activation values and, in the other case, the response to perturbations. These two cases suggest that it is often possible to evolve networks with interesting properties without losing the advantages of criticality. The evolved networks also show some interesting features which are discussed.

Trevor I. Smith, Philip Eaton, Suzanne White Brahmia et al.

We have developed the Physics Inventory of Quantitative Literacy (PIQL) as a tool to measure students' quantitative literacy in the context of introductory physics topics. We present the results from various quantitative analyses used to establish the validity of both the individual items and the PIQL as a whole. We show how examining the results from classical test theory analyses, factor analysis, and item response curves informed decisions regarding the inclusion, removal, or modification of items. We also discuss how the choice to include multiple-choice/multiple-response items has informed both our choices for analyses and the interpretations of their results. We are confident that the most recent version of the PIQL is a valid and reliable instrument for measuring students' physics quantitative literacy in calculus-based introductory physics courses at our primary research site. More data are needed to establish its validity for use at other institutions and in other courses.

Saumen Datta, Sourendu Gupta, Rishi Sharma

In our world the standard model of particle physics contains within it the fairly intractable theory called QCD. A toy version with two colours is often studied as a model confining and chiral symmetry breaking field theory. Here we investigate the cascade of changes at various distance scales if we make this change within the standard model. It is possible to limit the changes at the hadronic scale. However, the minor changes that occur actually cascade down to the far infrared, into nuclear and atomic physics, and chemistry. Through this it also possibly affects the evolution of stars and galaxies. We remark on this unexpected sensitivity of the universe to physics at the scale of quarks.

Fengyu Zhang, Lin Li, Mingliang Sun et al.

The goal of this research was to analyze the fungal community responsible for the biodeterioration of a pirogue in the National Maritime Museum of China and to make recommendations for the protection of this artifact. Molecular identification of fungal strains isolated from the surface of the pirogue and the air of the storage room that were most closely related to <i>Cladosporium</i>, <i>Penicillium</i>, <i>Talaromyces</i> and <i>Trichoderma</i> spp. DNA extracted from the samples was sequenced on the Illumina MiSeq platform. The results showed that the predominant fungal genera present were <i>Penicillium</i> sp., <i>Cladosporium</i> sp. and <i>Exophiala</i> sp. Thereafter, cellulose degradation experiments were carried out on the predominant fungi screened by pure culturing. Finally, we tested the sensitivity of the predominant fungal isolates to four biocides. This work suggests that we should pay more attention to <i>Penicillium</i> sp. and <i>Cladosporium</i> sp. in the protection of wooden artifacts, and environmental control is recommended as the main means of protecting the pirogue.

Marc Barthelemy

Challenges due to the rapid urbanization of the world -- especially in emerging countries -- range from an increasing dependence on energy, to air pollution, socio-spatial inequalities, environmental and sustainability issues. Modelling the structure and evolution of cities is therefore critical because policy makers need robust theories and new paradigms for mitigating these problems. Fortunately, the increased data available about urban systems opens the possibility of constructing a quantitative 'science of cities', with the aim of identifying and modelling essential phenomena. Statistical physics plays a major role in this effort by bringing tools and concepts able to bridge theory and empirical results. This article illustrates this point by focusing on fundamental objects in cities: the distribution of the urban population; segregation phenomena and spin-like models; the polycentric transition of the activity organization; energy considerations about mobility and models inspired by gravity and radiation concepts; CO2 emitted by transport; and finally, scaling that describes how various socio-economical and infrastructures evolve when cities grow.