Hasil untuk "Geophysics. Cosmic physics"

J. Julve, M. Moreno, S. Barbot et al.

Abstract The role of upper‐plate faulting in the seismic cycle of large megathrust earthquakes remains poorly understood. We use quasi‐dynamic numerical simulations of seismic cycles to analyze the interaction between crustal faulting and the foreshock sequence of the 2014 Iquique (Mw 8.2) earthquake in Northern Chile. Multi‐cycle models incorporating upper‐plate faulting align better with coseismic displacements, replicating events akin to the Iquique earthquake. Upper‐plate faulting significantly influences foreshock seismicity and deformation patterns. By calibrating the average hydraulic state—varying the effective normal stress—along the megathrust with pre‐earthquake seismicity, we find that lower pore pressure ratios result in more seismicity before the mainshock. This implies that the hydraulic state of the megathrust is critical for foreshock activity. This comprehensive modeling approach underscores the importance of the mechanical interplay between the megathrust and upper‐plate faults in precursory sequences of large subduction zone earthquakes.

Carlo Burigana, Tiziana Trombetti, Matteo Bonato et al.

Cosmic background radiation, both diffuse and discrete in nature, produced at different cosmic epochs before and after recombination, provides key information on the evolution of cosmic structures. We discuss the main classes of sources that contribute to the extragalactic background light from radio to sub-millimetre wavelenghs and the currently open question on the level of the cosmic radio background spectrum. The redshifted 21cm line signal from cosmological neutral Hydrogen during the primeval phases of cosmic structures as a probe of the cosmological reionisation process is presented, along with the route for confident detection of this signal. We then describe the basic formalism and the feasibility to study via a differential approach, based mainly on dipole analysis, the tiny imprints in the CB spectrum expected from a variety of cosmological and astrophysical processes at work during the early phases of cosmic perturbation and structure evolution. Finally, we discuss the identification of high-redshift sub-millimetre lensed galaxies with extreme magnifications in the Planck maps and their use for the comprehension of fundamental processes in early galaxy formation and evolution.

R. Benbrik, M. Boukidi, Stefano Moretti Polydisciplinary Faculty et al.

We explore the phenomenology of charged Higgs bosons ($H^\pm$) and Vector-Like Quarks (VLQs), specifically the top-like $T$, within the Two Higgs Doublet Model Type-II (2HDM-II). We consider both a singlet VLQ $(T)$ and a doublet $(TB)$ scenario, demonstrating that the presence of VLQs influences the scalar sector, particularly by alleviating the stringent mass constraints on $H^\pm$ imposed by $B$-physics observables such as $B\to X_s\gamma$. This relaxation arises from modifications in the couplings between $H^\pm$ and Standard Model (SM) quarks, with the magnitude of the effect differing between the singlet and doublet cases. We further analyse the constraints from the oblique parameters $S$ and $T$ on VLQ mixing angles.

Jihua Zhang, Qiao Rui, Yushun Yang et al.

Abstract The variation in the width of the mining face significantly affects the stability of the face, leading to potential roof fracturing and collapse. Additionally, strong mining pressure can manifest, severely impeding the safe production of coal mines. This study uses the No. 16705 conventional working face of Jinda Coal Mine as its engineering background to investigate the characteristics of roof strata movement and instability under conditions of variable-width mining in shallow-buried thin coal seams. First, the dynamic load of the roof strata is estimated based on the key strata theory. Next, a mechanical model of the immediate roof strata movement in the working face is established based on the theory of elastic thin plates, which has been used to reveal the impact of different dimensions of the overhanging plate structure and residual overhanging structures in the corner on roof movement and its associated fracture mechanics. The findings indicated that the maximum bending deformation, deformation moment, and bending stress all have an exponential function relationship with the roof width. Similarly, these metrics have an exponential function relationship with the overhanging span of the roof. In addition, these parameters all have a linear functional relationship with the size of the residual overhanging structures in the corner. Finally, the effect of roof instability on overlying pressure is analyzed, and both the initial fracture step length and cyclic movement fracture step length of the roof are estimated. These insights offer valuable scientific guidance and a theoretical foundation for analyzing the adaptability of load-bearing pillars pressure in thin coal seam mining faces, bearing significant relevance to safety production.

Shuke He, Chen Jin, Lisheng Shu et al.

High spatial resolution (HSR) remote sensing imagery presents a rich tapestry of foreground-background intricacies, rendering semantic segmentation in aerial contexts a formidable and vital undertaking. At its core, this challenge revolves around two pivotal questions: 1) Mitigating Background Interference and Enhancing Foreground Clarity. 2) Accurate Segmentation in Dense Small Object Cluster. Conventional semantic segmentation methods primarily cater to the segmentation of large-scale objects in natural scenes, yet they often falter when confronted with aerial imagery’s characteristic traits such as vast background areas, diminutive foreground objects, and densely clustered targets. In response, we propose a novel semantic segmentation framework tailored to overcome these obstacles. To address the first challenge, we leverage PointFlow modules in tandem with the Foreground-Scene (F-S) module. PointFlow modules act as a barrier against extraneous background information, while the F-S module fosters a symbiotic relationship between the scene and foreground, enhancing clarity. For the second challenge, we adopt a dual-branch structure termed disentangled learning, comprising Foreground Precedence Estimation and Small Object Edge Alignment (SOEA). Our foreground saliency guided loss optimally directs the training process by prioritizing foreground examples and challenging background instances. Extensive experimentation on the iSAID and Vaihingen datasets validates the efficacy of our approach. Not only does our method surpass prevailing generic semantic segmentation techniques, but it also outperforms state-of-the-art remote sensing segmentation methods.

Longfei LU, Guoliang TAO, Junyu WAN et al.

Using techniques such as ultra-microscopic organic petrology, the study explores the relationship between bioclasts such as siliceous and calcareous skeleton-wall-shell organism and high-quality hydrocarbon source rocks in terms of their biomolecular composition and stability. Common organisms containing biosilica and siliceous derivatives are mainly radiolarians and other protozoa, sponges, diatoms, chrysophytes, and the siliceous skeleton-wall-shell and debris of some planktonic algae like scales-bearing dinoflagellates. The biogenic calcium preserved in high-quality hydrocarbon source rocks is mainly derived from calcareous skeleton-wall-shell and their debris of animals such as planktonic foraminifera and pteropods and planktonic algae like coccolithophores or acritarchs. These biogenic siliceous and calcareous skeleton-wall-shell debris particles often contain varying amounts of organic matter (pectin or scleroprotein, equivalent to type Ⅲ organic matter), which can generate a certain amount of hydrocarbons at high to over-mature stages and can be preserved in the native pores of biological structures.

Quanyang Shao, Guangyu Fu, Yun Wang

The R-2 rotary seismograph can record rotating three components, MEMS acceleration, and tilt angle. In this study, the difference between ground acceleration and tilted background noise were analyzed using two phases of continuous observation data implemented in the ground and deep underground of the Huainan Deep Earth Laboratory. It was found that the deep earth environmental background interference was weaker, with background noise differences on the spectrum of up to 10 dB, showing that the Deep Earth Laboratory has superior conditions regarding low vibration and noise. The contrast before and after the skew correction of the MEMS acceleration using the tilt data revealed that the tilt had a non-negligible influence. The time-frequency analysis showed that the deep earth environment was favorable relative to the surface environment. The precision requirements of solid tide signal observations and shortcomings of existing instruments were also analyzed, proving the necessity of high precision observations in the deep earth environment.

Noah Wolfe, S. Vitale, C. Talbot

The detection of a sub-solar mass black hole could yield dramatic new insights into the nature of dark matter and early-Universe physics, as such objects lack a traditional astrophysical formation mechanism. Gravitational waves allow for the direct measurement of compact object masses during binary mergers, and we expect the gravitational-wave signal from a low-mass coalescence to remain within the LIGO frequency band for thousands of seconds. However, it is unclear whether one can confidently measure the properties of a sub-solar mass compact object and distinguish between a sub-solar mass black hole or other exotic objects. To this end, we perform Bayesian parameter estimation on simulated gravitational-wave signals from sub-solar mass black hole mergers to explore the measurability of their source properties. We find that the LIGO/Virgo detectors during the O4 observing run would be able to confidently identify sub-solar component masses at the threshold of detectability; these events would also be well-localized on the sky and may reveal some information on their binary spin geometry. Further, next-generation detectors such as Cosmic Explorer and the Einstein Telescope will allow for precision measurement of the properties of sub-solar mass mergers and tighter constraints on their compact-object nature.

Yong Yang, Chenxu Wan, Shuying Huang et al.

The purpose of pansharpening is to fuse a multispectral (MS) image with a panchromatic (PAN) image to generate a high spatial-resolution multispectral (HRMS) image. However, the traditional pansharpening methods do not adequately take consideration of the information of MS images, resulting in inaccurate detail injection and spectral distortion in the pansharpened results. To solve this problem, a new pansharpening approach based on adaptive high-frequency fusion and injection coefficients optimization is proposed, which can obtain an accurate injected high-frequency component (HFC) and injection coefficients. First, we propose a multi-level sharpening model to enhance the spatial information of the MS image, and then extract the HFCs from the sharpened MS image and PAN image. Next, an adaptive fusion strategy is designed to obtain the accurate injected HFC by calculating the similarity and difference of the extracted HFCs. Regarding the injection coefficients, we propose injection coefficients optimization scheme based on the spatial and spectral relationship between the MS image and PAN image. Finally, the HRMS image is obtained through injecting the fused HFC into the upsampled MS image with the injection coefficients. Experiments with simulated and real data are performed on IKONOS and Pléiades datasets. Both subjective and objective results indicate that our method has better performance than state-of-the-art pansharpening approaches.

Zhiwei Chong

This paper aims to show how to guide students with a familiar example to extract as much physics as possible before jumping into mathematical calculation. The period for a physical pendulum made up of a uniform rod is changed by attaching a piece of putty on it. The period for the combined system depends on the location of the putty. Simple reasoning without calculation shows that there are two locations for the putty that do not change the period of the physical pendulum: the axis and the center of percussion. Moreover, without calculation, we reason that there is at least one minimal period when the putty lies somewhere between these two locations.

I Kit Cheng, Nicholas Achilleos, Andy Smith

Two algorithms set for automatic detection of bow shock (BS) and magnetopause (MP) boundaries at Saturn using in situ magnetic field and plasma data acquired by the Cassini spacecraft are presented. Traditional threshold-based and modern deep learning algorithms were investigated for the task of boundary detection. Sections of Cassini’s orbits were pre-selected based on empirical BS and MP boundary models, and from outlier detection in magnetic field data using an autoencoder neural network. The threshold method was applied to pre-selected magnetic field and plasma data independently to compute parameters to which a threshold was applied to determine the presence of a boundary. The deep learning method used a type of convolutional neural network (CNN) called ResNet on images of magnetic field time series data and electron energy-time spectrograms to classify the presence of boundaries. 2012 data were held out of the training data to test and compare the algorithms on unseen data. The comparison showed that the CNN method applied to plasma data outperformed the threshold method. A final multiclass CNN classifier trained on plasma data obtained F1 scores of 92.1% ± 1.4% for BS crossings and 84.7% ± 1.9% for MP crossings on a corrected test dataset (from use of a bootstrap method). Reliable automated detection of boundary crossings could enable future spacecraft experiments like the PEP instrument on the upcoming JUICE spacecraft mission to dynamically adapt the best observing mode based on rapid classification of the boundary crossings as soon as it appears, thus yielding higher quality data and improved potential for scientific discovery.

Vanessa López-Barquero, Paolo Desiati

As cosmic rays (CRs) propagate in the Galaxy, they can be affected by magnetic structures that temporarily trap them and cause their trajectories to display chaotic behavior, therefore modifying the simple diffusion scenario. When CRs arrive at the Earth, they do so anisotropically. These chaotic effects can be a fundamental contributor to this anisotropy. Accordingly, this requires a comprehensive description of chaos in trapping conditions since assessing their repercussions on the CR arrival directions is necessary. This study utilizes a new method described in López-Barquero and Desiati (2021) to characterize chaotic trajectories in bound systems. This method is based on the Finite-Time Lyapunov Exponent (FTLE), a quantity that determines the levels of chaos based on the trajectories' divergence rate. The FTLE is useful since it adapts to trapping conditions in magnetic structures or even propagating media changes. Here, we explore the effects that chaos and trapping can have on the TeV CR anisotropy. Concretely, we apply this method to study the behavior of CRs entering the heliosphere. Specifically, how the distinct heliospheric structures and CR impinging directions from the ISM can affect chaos levels. The heliosphere has an intrinsic directionality that affects CRs differently depending on where they enter it. This feature causes preferential directions from which particles tend to be more chaotic than others. This eventually translates into changes in the arrival maps which are not uniformly distributed. Instead, we expect sectors in the map to change separately from others, creating a time variation that could be detected. Consequently, this result points to the idea that time-variability in the maps is essential to understanding the CR anisotropy's overall processes.

H. Kurokawa, M. Laneuville, Y. Li et al.

Earth's mantle nitrogen (N) content is comparable to that found in its N-rich atmosphere. Mantle N has been proposed to be primordial or sourced by later subduction, yet its origin has not been elucidated. Here we model N partitioning during the magma ocean stage following planet formation and the subsequent cycling between the surface and mantle over Earth history using argon (Ar) and N isotopes as tracers. The partitioning model, constrained by Ar, shows that only about 10% of the total N content can be trapped in the solidified mantle due to N's low solubility in magma and low partitioning coefficients in minerals in oxidized conditions supported from geophysical and geochemical studies. A possible solution for the primordial origin is that Earth had about 10 times more N at the time of magma ocean solidification. We show that the excess N could be removed by impact erosion during late accretion. The cycling model, constrained by N isotopes, shows that mantle N can originate from efficient N subduction, if the sedimentary N burial rate on early Earth is comparable to that of modern Earth. Such a high N burial rate requires biotic processing. Finally, our model provides a methodology to distinguish the two possible origins with future analysis of the surface and mantle N isotope record.

K. Freese, Aliki Litsa, M. Winkler

In Chain Inflation the universe tunnels along a series of false vacua of ever-decreasing energy. The main goal of this paper is to embed Chain Inflation in high energy fundamental physics. We begin by illustrating a simple effective formalism for calculating Cosmic Microwave Background (CMB) observables in Chain Inflation. Density perturbations seeding the anisotropies emerge from the probabilistic nature of tunneling (rather than from quantum fluctuations of the inflation). To obtain the correct normalization of the scalar power spectrum and the scalar spectral index, we find an upper limit on the scale of inflation at horizon crossing of CMB scales, V 1/4 ∗ < 10 12 GeV. We then provide an explicit realization of chain inflation, in which the inflaton is identified with an axion in supergravity. The axion enjoys a perturbative shift symmetry which is broken to a discrete remnant by instantons. The model, which we dub ‘natural chain inflation’ satisfies all cosmological constraints and can be embedded into a standard ΛCDM cosmology. Our work provides a major step towards the ultraviolet completion of chain inflation in string theory.

R. Garcia, M. Anzorena, J. Valdes-Galicia et al.

Abstract Machine learning is a powerful tool used in many different areas, from image processing to space navigation and high-energy physics. In this paper we present a configuration of different artificial intelligent tools aimed at the extraction of features from data registered in the SciBar Cosmic Ray Telescope (SciCRT). The SciCRT is an array of plastic scintillator bars that work nearly independently as particle detectors. When a particle crosses inside the telescope, scintillation photons are emitted by the plastics. The intensity of photons is directly proportional to the energy deposited in each bar. Taking advantage of the construction of the telescope, the small transverse area of the scintillator bars, it is possible to do particle tracking and analysis. The main purpose of SciCRT is the detection of solar neutrons originated in the violent phenomena taking place at the surface of the Sun. Nonetheless, the SciCRT is capable of detecting different kinds of secondary particles produced by the interactions of primary cosmic rays with the atmospheric nuclei. For this reason, the task of signal classification is essential. Our final goal will be the classification of detected cosmic ray particles, as well as, the unfolding of the neutron energy spectrum and the estimation of the angular distribution. To achieve this our methodology relies of pattern recognition, artificial neural networks, k-means clustering and k-Nearest Neighbors. In addition, our paper presents a Monte Carlo simulation of the SciCRT for the training and evaluation of the machine learning algorithms.

Z. Weng

The Alpha Magnetic Spectrometer is a general-purpose particle physics detector operating on the International Space Station. Precision measurements by AMS of the cosmic-ray elementary particle fluxes and nuclei fluxes reveal new unexpected phenomena. The positron flux exhibits a significant excess starting from 25.2 ± 1.8GeV followed by a sharp drop-off above 284+91 −64 GeV, consistent with a primary source of cosmic-ray positrons from either dark matter collisions or new astrophysical sources. The different behavior of the cosmic-ray electron flux and positron flux shows that most high energy electrons originate from different sources than high energy positrons. Intriguingly, the positron flux and the antiproton flux have strikingly similar behavior at high energies. New observations from AMS on cosmic nuclei show that primary cosmic-ray He, C, and O have an identical rigidity dependence above 60 GV and deviate from a single powerlaw above 200 GV. Unexpectedly, the primary Ne, Mg, and Si also have an identical rigidity dependence above 86.5 GV, but they are different from that of He, C, and O. This shows that primary cosmic rays have at least two distinct classes of rigidity dependence. Above 30 GV, secondary cosmic nuclei Li, Be, and B have identical rigidity dependence which is distinctly different from those of primary cosmic rays. The results from AMS on many different types of cosmic rays are not explained by the current theoretical models and provide unique input to the understanding of the origins and evolution of cosmic rays in the galaxy.

A. Dutfoy

F. Arleo, G. Jackson, St'ephane Peign'e

The phenomenon of fully coherent energy loss (FCEL) in the collisions of protons on light ions affects the physics of cosmic ray air showers. As an illustration, we address two closely related observables: hadron production in forthcoming proton-oxygen collisions at the LHC, and the atmospheric neutrino fluxes induced by the semileptonic decays of hadrons produced in proton-air collisions. In both cases, a significant nuclear suppression due to FCEL is predicted. The conventional and prompt neutrino fluxes are suppressed by $\sim 10...25\%$ in their relevant neutrino energy ranges. Previous estimates of atmospheric neutrino fluxes should be scaled down accordingly to account for FCEL.

M. Parvu, I. Lazanu

The Deep Underground Neutrino Experiment (DUNE) is a leading-edge, international experiment for neutrino science and proton decay studies. This experiment is looking for answers regarding several fundamental questions about the nature of matter and the evolution of the universe: origin of matter, unification of forces, physics of black holes. Two far detector prototypes using two distinct technologies have been developed at CERN. The prototypes are testing and validating the liquid argon time projection chamber technology (LArTPC). In neutrino physics, as well as in any experiment with rare interaction rate, the good knowledge of the radioactive backgrounds is important to the success of the study. Muons and neutrons represent the main sources of background for this kind of experiments. In this paper, we have considered two sources of neutrons: cosmic neutrons and neutrons coming from the accelerating tunnel. Also, cosmic muons are taken into account. The contribution of these particles to the production of radioactive isotopes inside the active volume of the detector in comparison to the one corresponding to muons is shown. Also, simulations of nuclear reactions for the processes of interest for investigating the radioactive background due to the lack of measurements or insufficient experimental data are presented. Most of the results presented in this paper will be of interest for the future underground DUNE experiment.

Xiao-Nan Wang, X. Lan, Yong-Sheng Huang et al.

An energetic muon beam is an attractive key to unlock new physics beyond the Standard Model: the lepton flavor violation or the anomalous magnetic moment, and also is a competitive candidate for the expected neutrino factory. Lots of the muon scientific applications are limited by low flux cosmic-ray muons, low energy muon sources or extremely expensive muon accelerators. An prompt acceleration of the low-energy muon beam is found in the beam-driven plasma wakefield up to $\mathrm{TV/m}$. The muon beam is accelerated from $275\mathrm{MeV}$ to more than $10\mathrm{GeV}$ within $22.5\mathrm{ps}$. Choosing the injection time of the muon beam in a proper range, the longitudinal spatial distribution and the energy distribution of the accelerated muon beam are compressed. The efficiency of the energy transfer from the driven electron beam to the muon beam can reach $20\%$. The prompt acceleration scheme is a promising avenue to bring the expected neutrino factory and the muon collider into reality and to catch new physics beyond the Standard Model.