检索结果-内蒙古大学图书馆

arXiv 2023年

作者： Susemiehl, Nicholas Mandell, Avi M. Villanueva, Geronimo L. Liuzzi, Giuliano Moore, Michael Baines, Tyler Himes, Michael D. Smith, Adam J.R.W. Southeastern Universities Research Association WashingtonDC United States Center for Research and Exploration in Space Science and Technology NASA Goddard Space Flight Center GreenbeltMD United States NASA Goddard Space Flight Center GreenbeltMD United States Dep. of Physics American University WashingtonDC United States Business Integra Inc. BethesdaMD United States Planetary Sciences Group Department of Physics University of Central Florida OrlandoFL United States NASA Postdoctoral Program Fellow NASA Goddard Space Flight Center GreenbeltMD United States

Techniques to retrieve the atmospheric properties of exoplanets via direct observation of their reflected light have often been limited in scope due to computational constraints imposed by the forward-model calculations. We have developed a new set of techniques which significantly decreases the time required to perform a retrieval while maintaining accurate results. We constructed a grid of 1.4 million pre-computed geometric albedo spectra valued at discrete sets of parameter points. Spectra from this grid are used to produce models for a fast and efficient nested sampling routine called PSGnest. Beyond the upfront time to construct a spectral grid, the amount of time to complete a full retrieval using PSGnest is on the order of seconds to minutes using a personal computer. An extensive evaluation of the error induced from interpolating intermediate spectra from the grid indicates that this bias is insignificant compared to other retrieval error sources, with an average coefficient of determination between interpolated and true spectra of 0.998. We apply these new retrieval techniques to help constrain the optimal bandpass centers for retrieving various atmospheric and bulk parameters from a LuvEx-type mission observing several planetary archetypes. We show that spectral observations made using a 20% bandpass centered at 0.73 microns can be used alongside our new techniques to make detections of H2O and O2 without the need to increase observing time beyond what is necessary for a signal-to-noise ratio of 10. The methods introduced here will enable robust studies of the capabilities of future observatories to characterize exoplanets. © 2023, CC BY.

关键词： Personal computers

来源：评论

学校读者我要写书评

暂无评论

Cosmology with the Galaxy Bispectrum Multipoles: Optimal Estimation and Application to BOSS Data

arXiv

引用

arXiv 2023年

作者： Ivanov, Mikhail M. Philcox, Oliver H.E. Cabass, Giovanni Nishimichi, Takahiro Simonović, Marko Zaldarriaga, Matias School of Natural Sciences Institute for Advanced Study 1 Einstein Drive PrincetonNJ08540 United States NASA Hubble Fellowship Program Einstein Postdoctoral Fellow United States Center for Theoretical Physics Department of Physics Columbia University 538 West 120th Street New YorkNY10027 United States Simons Society of Fellows Simons Foundation New YorkNY10010 United States Department of Astrophysical Sciences Princeton University Peyton Hall 4 Ivy Lane PrincetonNJ08544 United States Center for Gravitational Physics and Quantum Information Yukawa Institute for Theoretical Physics Kyoto University Kyoto606-8502 Japan UTIAS The University of Tokyo Chiba Kashiwa277-8583 Japan Theoretical Physics Department CERN 1 Esplanade des Particules Geneva 23CH-1211 Switzerland

We present a framework for self-consistent cosmological analyses of the full-shape anisotropic bispectrum, including the quadrupole (` = 2) and hexadecapole (` = 4) moments. This features a novel window-free algorithm for extracting the latter quantities from data, derived using a maximum-likelihood prescription. Furthermore, we introduce a theoretical model for the bispectrum multipoles (which does not introduce new free parameters), and test both aspects of the pipeline on several high-fidelity mocks, including the PT Challenge suite of gigantic cumulative volume. This establishes that the systematic error is significantly below the statistical threshold, both for the measurement and modeling. As a realistic example, we extract the large-scale bispectrum multipoles from BOSS DR12 and analyze them in combination with the power spectrum data. Assuming a minimal ΛCDM model, with a BBN prior on the baryon density and a Planck prior on ns, we can extract the remaining cosmological parameters directly from the clustering data. The inclusion of the unwindowed higher-order (` > 0) large-scale bispectrum multipoles is found to moderately improve one-dimensional cosmological parameter posteriors (at the 5% − 10% level), though these multipoles are detected only in three out of four BOSS data segments at ≈ 5σ. Combining information from the power spectrum and bispectrum multipoles, the real space power spectrum, and the post-reconstructed BAO data, we find H0 = 68.2 ± 0.8 km s−1Mpc−1, Ωm = 0.33 ±0.01 and σ8 = 0.736 ±0.033 (the tightest yet found in perturbative full-shape analyses). Our estimate of the growth parameter S8 = 0.77 ±0.04 agrees with both weak lensing and CMB results. The estimators and data used in this work have been made publicly available. © 2023, CC BY-NC-SA.

关键词： Power spectrum

来源：评论

学校读者我要写书评

暂无评论

Population of X-ray Sources in the Intermediate-Age Cluster NGC 3532: a Test Bed for Machine-Learning Classification

arXiv

引用

arXiv 2022年

作者： Chen, Steven Kargaltsev, Oleg Yang, Hui Hare, Jeremy Volkov, Igor Rangelov, Blagoy Tomsick, John Department of Physics The George Washington University 725 21st St. NW WashingtonDC20052 United States NASA Goddard Space Flight Center GreenbeltMD20771 United States NASA Postdoctoral Program Fellow United States Department of Physics Texas State University 601 University Drive San MarcosTX78666 United States Space Sciences Laboratory University of California BerkeleyCA94720 United States

Open clusters are thought to be the birth place of most stars in the Galaxy. Thus, they are excellent laboratories for investigating stellar evolution, and X-ray properties of various types of stars (including binary stars, evolved stars, and compact objects). In this work, we investigate the population of X-ray sources in the nearby 300-Myr-old open cluster NGC 3532 using Chandra X-ray Observatory and multi-wavelength data from several surveys. We apply a random-forest machine-learning pipeline (MUWCLASS) to classify all confidently detected X-ray sources (S/N> 5) in the field of NGC 3532. We also perform a more detailed investigation of brighter sources, including their X-ray spectra and lightcurves. Most X-ray sources are confirmed as coronally-active low-mass stars, many of which are confidently identified by MUWCLASS. Several late B or early A-type stars are relatively bright in X-rays, most of which are likely binaries. We do not find any compact objects among X-ray sources reliably associated with NGC 3532, down to the limiting X-ray flux of ∼ 2 × 10−15 erg s−1 cm−2, corresponding to LX ∼ 6 × 1028 erg s−1 at the cluster’s distance. We also identify several Galactic sources beyond NGC 3532 that differ from typical coronally active stars, and were classified by MUWCLASS as potential compact objects. Detailed investigation reveals that these sources may indeed belong to rarer classes, and deserve follow up observations. Copyright © 2022, The Authors. All rights reserved.

关键词： Machine learning

来源：评论

学校读者我要写书评

暂无评论

Correlations between cascaded photons from spatially localized biexcitons in ZnSe

arXiv

引用

arXiv 2022年

作者： Pettit, Robert M. Karasahin, Aziz von den Driesch, Nils Jansen, Marvin Marco Pawlis, Alexander Waks, Edo Institute for Research in Electronics and Applied Physics Joint Quantum Institute University of Maryland College ParkMD20742 United States Intelligence Community Postdoctoral Research Fellowship Program University of Maryland College ParkMD20742 United States Forschungszentrum Jülich GmbH Jülich52425 Germany Jülich–Aachen Research Alliance Aechen 52062 Germany

Radiative cascades emit correlated photon pairs, providing a pathway for the generation of entangled photons. The realization of a radiative cascade with impurity atoms in semiconductors, a leading platform for the generation of quantum light, would therefore provide a new avenue for the development of entangled photon pair sources. Here we demonstrate a radiative cascade from the decay of a biexciton at an impurity-atom complex in a ZnSe quantum well. The emitted photons show clear temporal correlations revealing the time–ordering of the cascade. Our result establishes impurity atoms in ZnSe as a potential platform for photonic quantum technologies using radiative cascades. Copyright © 2022, The Authors. All rights reserved.

关键词： Selenium compounds

来源：评论

学校读者我要写书评

暂无评论

Automatic detection of large-scale flux ropes and their geoeffectiveness with a machine learning approach

arXiv

引用

arXiv 2024年

作者： Pal, Sanchita dos Santos, Luiz F.G. Weiss, Andreas J. Narock, Thomas Narock, Ayris Nieves-Chinchilla, Teresa Jian, Lan K. Good, Simon W. NASA Postdoctoral Program Fellow NASA Goddard Space Flight Center GreenbeltMD20771 United States SETI Institute Mountain ViewCA94043 United States Center for Natural Computer and Data Sciences Goucher College BaltimoreMD United States ADNET Systems Inc. 7515 Mission Drive LanhamMD20706 United States Heliophysics Science Division NASA Goddard Space Flight Center GreenbeltMD20771 United States Department of Physics University of Helsinki P.O. Box 64 HelsinkiFI-00014 Finland

Detecting large-scale flux ropes (FRs) embedded in interplanetary coronal mass ejections (ICMEs) and assessing their geoeffectiveness are essential since they can drive severe space weather. At 1 au, these FRs have an average duration of 1 day. Their most common magnetic features are large, smoothly rotating magnetic fields. Their manual detection has become a relatively common practice over decades, although visual detection can be time-consuming and subject to observer bias. Our study proposes a pipeline that utilizes two supervised binary-classification machine learning (ML) models trained with solar wind magnetic properties to automatically detect large-scale FRs and additionally determine their geoeffectiveness. The first model is used to generate a list of auto-detected FRs. Using the properties of southward magnetic field the second model determines the geoeffectiveness of FRs. Our method identifies 88.6% and 80% large-scale ICMEs (duration ≥ 1 day) observed at 1 au by Wind and Sun Earth Connection Coronal and Heliospheric Investigation (STEREO) mission, respectively. While testing with a continuous solar wind data obtained from Wind, our pipeline detected 56 of the 64 large-scale ICMEs during 2008 - 2014 period (recall= 0.875) but many false positives (precision= 0.56) as we do not take into account any additional solar wind properties than the magnetic properties. We found an accuracy of 0.88 when estimating the geoeffectiveness of the auto-detected FRs using our method. Thus, in space weather now-casting and forecasting at L1 or any planetary missions, our pipeline can be utilized to offer a first-order detection of large-scale FRs and geoeffectiveness. © 2024, CC BY.

关键词： Magnetic fields

来源：评论

学校读者我要写书评

暂无评论

Topological flat bands in a family of multilayer graphene moiré lattices

arXiv

引用

arXiv 2024年

作者： Waters, Dacen Su, Ruiheng Thompson, Ellis Okounkova, Anna Arreguin-Martinez, Esmeralda He, Minhao Hinds, Katherine Watanabe, Kenji Taniguchi, Takashi Xu, Xiaodong Zhang, Ya-Hui Folk, Joshua Yankowitz, Matthew Department of Physics University of Washington SeattleWA98195 United States Intelligence Community Postdoctoral Research Fellowship Program University of Washington SeattleWA98195 United States Stewart Blusson Quantum Matter Institute University of British Columbia VancouverBCV6T 1Z1 Canada Department of Physics and Astronomy University of British Columbia VancouverBCV6T 1Z1 Canada Department of Materials Science and Engineering University of Washington SeattleWA98195 United States Department of Physics Princeton University PrincetonNJ08544 United States Research Center for Functional Materials National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan International Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Department of Physics and Astronomy Johns Hopkins University BaltimoreMD21205 United States

Moiré materials host a wealth of intertwined correlated and topological states of matter, all arising from flat electronic bands with nontrivial quantum geometry [1, 2]. A prominent example is the family of alternating-twist magic-angle graphene stacks, which exhibit symmetry-broken states at rational fillings of the moiré band and superconductivity close to half filling [3–7]. Here, we introduce a second family of twisted graphene multilayers made up of twisted sheets of M- and N-layer Bernal-stacked graphene flakes. Calculations indicate that applying an electric displacement field isolates a flat and topological moiré conduction band that is primarily localized to a single graphene sheet below the moiré interface. Phenomenologically, the result is a striking similarity in the hierarchies of symmetry-broken phases across this family of twisted graphene multilayers. Our results show that this family of structures offers promising new opportunities for the discovery of exotic new correlated and topological phenomena, enabled by using the layer number to fine tune the flat moiré band and its screening environment. Copyright © 2024, The Authors. All rights reserved.

关键词： Graphene

来源：评论

学校读者我要写书评

暂无评论

Single quantum emitters with spin ground states based on Cl bound excitons in ZnSe

引用

Physical Review A 2022年第3期106卷 L030402-L030402页

作者： Aziz Karasahin Robert M. Pettit Nils von den Driesch Marvin Marco Jansen Alexander Pawlis Edo Waks Institute for Research in Electronics and Applied Physics Department of Electrical and Computer Engineering and Joint Quantum Institute University of Maryland College Park Maryland 20742 USA Intelligence Community Postdoctoral Research Fellowship Program University of Maryland College Park Maryland 20742 USA Peter-Grünberg-Institute (PGI-9) Forschungszentrum Jülich GmbH 52425 Jülich Germany JARA-FIT (Fundamentals of Future Information Technology) Jülich-Aachen Research Alliance 52062 Aachen Germany

Defects in wide-band-gap semiconductors are promising qubit candidates for quantum communication and computation. Epitaxially grown II-VI semiconductors are particularly promising host materials due to their direct band gap and potential for isotopic purification to a spin-zero nuclear background. Here, we show an alternative type of single photon emitter with potential electron spin qubits based on Cl impurities in ZnSe. We utilize a quantum well to increase the binding energies of donor emission and confirm single photon emission with short radiative lifetimes of 192 ps. Furthermore, we verify that the ground state of the Cl donor complex contains a single electron by observing two-electron-satellite emission, leaving the electron in higher orbital states. We also characterize the Zeeman splitting of the exciton transition by performing polarization-resolved magnetic spectroscopy on single emitters. Our results suggest single Cl impurities are suitable as a single photon source with a potential photonic interface.

关键词： Impurities Quantum information with solid state qubits Single photon sources Quantum wells Wide band gap systems Spectroscopy

来源：评论

学校读者我要写书评

暂无评论

Machine learning for improved current-density reconstruction from two-dimensional vector magnetic images

引用

Physical Review Applied 2025年第3期23卷 034035-034035页

作者： Niko R. Reed Danyal Bhutto Matthew J. Turner Declan M. Daly Sean M. Oliver Jiashen Tang Kevin S. Olsson Nicholas Langellier Mark J.H. Ku Department of Physics University of Maryland College Park Maryland USA Quantum Technology Center University of Maryland College Park Maryland USA Joint Quantum Institute University of Maryland College Park Maryland USA Department of Biomedical Engineering Boston University Boston Massachusetts USA A. A. Martinos Center for Biomedical Imaging Massachusetts General Hospital Charlestown Massachusetts USA Department of Electrical and Computer Engineering University of Maryland College Park Maryland USA The MITRE Corporation McLean Virginia 22102 USA Intelligence Community Postdoctoral Research Fellowship Program University of Maryland College Park Maryland 20742 USA Department of Physics Harvard University Cambridge Massachusetts USA Present address: VideaHealth Inc. Boston MA. Department of Materials Science and Engineering University of Delaware Newark Delaware 19716 USA Department of Physics and Astronomy University of Delaware Newark Delaware 19716 USA Present address: Northrop Grumman Mission Systems Linthicum Maryland 21090 USA.

The reconstruction of electrical current densities from magnetic field measurements is an important technique with applications in materials science, circuit design, quality control, plasma physics, and biology. Analytic reconstruction methods exist for planar currents, but break down in the presence of high-spatial-frequency noise or large standoff distance, restricting the types of systems that can be studied. Here, we demonstrate the use of a deep convolutional neural network for current density reconstruction from two-dimensional images of vector magnetic fields acquired by a quantum diamond microscope . Trained network performance significantly exceeds analytic reconstruction for data with high noise or large standoff distances. This machine learning technique can perform quality inversions on lower-signal-to-noise-ratio data, significantly reducing the data collection time and permitting reconstructions of weaker and three-dimensional current sources.

关键词： Signal to noise ratio

来源：评论

学校读者我要写书评

暂无评论

AstroPix: A Pixelated HVCMOS Sensor for Space-Based Gamma-Ray Measurement

arXiv

引用

arXiv 2025年

作者： Steinhebel, Amanda L. Caputo, Regina Violette, Daniel P. Affolder, Anthony Bauman, Autumn Chinatti, Carolyn Deshmukh, Aware Fadayev, Vitaliy Fukazawa, Yasushi Jadhav, Manoj Kierans, Carolyn Kim, Bobae Kim, Jihee Klest, Henry Kroger, Olivia Kumar, Kavic Kushima, Shin Lauenstein, Jean-Marie Leys, Richard Martinez-Mckinney, Forest Metcalfe, Jessica Metzler, Zachary Mitchell, John W. Nakano, Norito Ott, Jennifer Peric, Ivan Perkins, Jeremy S. Rudin, Max R. Shin, Taylor K.W. Sommer, Grant Striebig, Nicolas Suda, Yusuke Tajima, Hiroyasu Valverde, Janeth Zurek, Maria NASA Postdoctoral Program NASA Goddard Space Flight Center MD United States University of California Santa CruzCA United States University of Colorado DenverCO United States NASA Office of STEM Engagement WashingtonDC United States Carleton College Minnesota United States Center for Research and Exploration in Space Science and Technology Maryland United States Physics Program Graduate School of Advanced Science and Engineering Hiroshima University Japan Argonne National Laboratory Illinois United States University of Maryland MD United States Institute for Space-Earth Environmental Research Nagoya University Japan Karlsruher Institut für Technologie Germany Rice University TX United States The George Washington University WashingtonDC United States Kobayashi-Maskawa Institute for the Origin of Particles and the Universe Nagoya University Japan Department of Physics Center for Space Sciences and Technology University of Maryland Baltimore CountyMD United States

A next-generation medium-energy gamma-ray telescope targeting the MeV range would address open questions in astrophysics regarding how extreme conditions accelerate cosmic-ray particles, produce relativistic jet outflows, and more. One concept, AMEGO-X, relies upon the mission-enabling CMOS Monolithic Active Pixel Sensor silicon chip AstroPix. AstroPix is designed for space-based use, featuring low noise, low power consumption, and high scalability. Desired performance of the device include an energy resolution of 5 keV (or 10% FWHM) at 122 keV and a dynamic range per-pixel of 25 − 700 keV, enabled by the addition of a high-voltage bias to each pixel which supports a depletion depth of 500 μm. This work reports on the status of the AstroPix development process with emphasis on the current version under test, version three (v3), and highlights of version two (v2). Version 3 achieves energy resolution of 10.4 ± 3.2% at 59.5 keV and 94 ± 6 μm depletion in a low-resistivity test silicon substrate. © 2025, CC BY.

关键词： Cosmology

来源：评论

学校读者我要写书评

暂无评论

Graphene calorimetric single-photon detector

arXiv

引用

arXiv 2024年

作者： Huang, Bevin Arnault, Ethan G. Jung, Woochan Fried, Caleb Russell, B. Jordan Watanabe, Kenji Taniguchi, Takashi Henriksen, Erik A. Englund, Dirk Lee, Gil-Ho Fong, Kin Chung Intelligence Community Postdoctoral Research Fellowship Program Massachusetts Institute of Technology CambridgeMA02139 United States Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology CambridgeMA02139 United States Department of Physics Pohang University of Science and Technology Pohang790-784 Korea Republic of Department of Physics Washington University in St. Louis St. LouisMO United States Research Center for Electronic and Optical Materials National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Research Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan RTX BBN Technologies Quantum Engineering and Computing Group CambridgeMA02138 United States

Single photon detectors (SPDs) [1, 2] are essential technology in quantum science, quantum network, biology, and advanced imaging [3-5]. To detect the small quantum of energy carried in a photon, conventional SPDs rely on energy excitation across either a semiconductor bandgap or superconducting gap. While the energy gap suppresses the false-positive error, it also sets an energy scale that can limit the detection efficiency of lower energy photons and spectral bandwidth of the SPD [6-8]. Here, we demonstrate an orthogonal approach to detect single near-infrared photons using graphene calorimeters [9-13]. By exploiting the extremely low heat capacity of the pseudo-relativistic electrons in graphene near its charge neutrality point [14], we observe an electron temperature rise up to ∼2 K using a hybrid Josephson junction. In this proof-of-principle experiment, we achieve an intrinsic quantum efficiency of 87% (75%) with dark count © 2024, CC BY.

关键词： Particle beams

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：