{"results":[{"id":"doaj_10.1016/j.physletb.2026.140158","title":"Graviton condensate stars and its gravitational echoes","authors":[{"name":"Muhammad Fitrah Alfian Rangga Sakti"}],"abstract":"We construct the exact stellar configurations that contain an ordinary perfect-fluid matter that interacts minimally with a condensate of gravitons with distinct pressure conditions on the surface. We propose vanishing transverse pressure on the surface for, namely graviton condensate type 1 and vanishing radial pressure on the surface for type 2. The condition for the radial pressure of type 1 requires the existence of a thin shell that will balance the pressure discontinuity while for type 2, the discontinuity on transverse pressure does not require the additional thin shell. It is found that the Buchdahl inequality of the resulting stellar configurations depends on the parameter related to the graviton condensate, such that we can find the ultra-compact regime of the stellar models. Moreover, the echo time and echo frequency within the ultra-compact regime are computed. At the same compactness, it is found that the presence of the graviton condensate will delay the gravitational echoes for type 2 and will expedite the gravitational echoes for type 1 compared to constant density star, τecho2 \u003e τCDS \u003e τecho1. Furthermore, the gravitational perturbation of a massless scalar wave is also investigated to support these results. These results could open more opportunities for the observational study of graviton in the near future, mostly from the compact astrophysical objects.","source":"DOAJ","year":2026,"language":"","subjects":["Physics"],"doi":"10.1016/j.physletb.2026.140158","url":"http://www.sciencedirect.com/science/article/pii/S0370269326000122","is_open_access":true,"published_at":"","score":70},{"id":"doaj_10.1038/s42005-025-02475-6","title":"Reinforcement learning with learned gadgets to tackle hard quantum problems on real hardware","authors":[{"name":"Akash Kundu"},{"name":"Leopoldo Sarra"}],"abstract":"Abstract Quantum computing offers exciting opportunities for simulating complex quantum systems and optimizing large-scale combinatorial problems, but its practical use is limited by device noise and constrained connectivity. Designing quantum circuits, which are fundamental to quantum algorithms, is therefore a central challenge in current quantum hardware. Existing reinforcement learning-based methods for circuit design lose accuracy when restricted to hardware-native gates and device-level compilation. Here, we introduce gadget reinforcement learning (GRL) that combines learning with program synthesis to automatically construct composite gates that expand the action space while respecting hardware constraints. We show that this approach improves accuracy, hardware compatibility, and scalability for transverse-field Ising and quantum chemistry problems, reaching systems of up to ten qubits within realistic computational budgets. This framework demonstrates how learned, reusable circuit building blocks can guide the co-design of algorithms and hardware for quantum processors.","source":"DOAJ","year":2026,"language":"","subjects":["Astrophysics","Physics"],"doi":"10.1038/s42005-025-02475-6","url":"https://doi.org/10.1038/s42005-025-02475-6","is_open_access":true,"published_at":"","score":70},{"id":"doaj_10.3847/1538-4357/ae2610","title":"Is There a Retrograde Accretion Disk around 4U 1626–67? Tracking Torque Reversals with a State-space Model","authors":[{"name":"Joseph O’Leary"},{"name":"Andrew Melatos"},{"name":"Tom Kimpson"},{"name":"Dimitris M. Christodoulou"},{"name":"Nicholas J. O’Neill"},{"name":"Patrick M. Meyers"},{"name":"Sayantan Bhattacharya"},{"name":"Silas G. T. Laycock"}],"abstract":"X-ray timing studies of the persistent, Galactic, accretion-powered pulsar 4U 1626−67 reveal torque reversals, during which the pulse frequency ν ( t ) alternates between multiyear episodes of secular acceleration and deceleration, separated by transitions lasting ≲150 days. Here an unscented Kalman filter is applied to track the ν ( t ) fluctuations observed in 22.7 yr (3340 samples) of publicly available Compton Gamma-Ray Observatory and Fermi Gamma-Ray Space Telescope data to test the canonical picture of magnetocentrifugal accretion for consistency with prograde–prograde and retrograde–prograde accretion disk configurations on either side of the 2008 torque reversal. It is found that the retrograde–prograde model is preferred, with a log Bayes factor equal to 0.44 and a maximum a posteriori log likelihood ratio equal to 2.5. The mass accretion rate Q ( t ) and magnetocentrifugal fastness ω ( t ) transition smoothly between episodes of deceleration and acceleration: Q ( t ) shifts by ≤0.34 dex across the reversal, and one measures ω ( t ) ≈ 0.25 and ω ( t ) ≈ 0.30 during deceleration and acceleration, respectively. The angular acceleration $\\dot{{\\rm{\\Omega }}}(t)$ satisfies $-9\\,\\lesssim \\,\\dot{{\\rm{\\Omega }}}(t)/(1{0}^{-12}\\,{\\rm{rad}}\\,{{\\rm{s}}}^{-2})\\,\\lesssim \\,-5$ and $2\\,\\lesssim \\,\\dot{{\\rm{\\Omega }}}(t)/(1{0}^{-12}\\,{\\rm{rad}}\\,{{\\rm{s}}}^{-2})\\,\\lesssim \\,9$ before and after the 2008 reversal, respectively, compared to $\\dot{{\\rm{\\Omega }}}\\approx -3.0\\,\\times 1{0}^{-12}\\,{\\rm{rad}}\\,{{\\rm{s}}}^{-2}$ before reversal and $\\dot{{\\rm{\\Omega }}}\\approx 2.5\\times 1{0}^{-12}\\,{\\rm{rad}}\\,{{\\rm{s}}}^{-2}$ after reversal, as inferred from previous long-term X-ray timing and spectral analysis of 4U 1626−67.","source":"DOAJ","year":2026,"language":"","subjects":["Astrophysics"],"doi":"10.3847/1538-4357/ae2610","url":"https://doi.org/10.3847/1538-4357/ae2610","is_open_access":true,"published_at":"","score":70},{"id":"doaj_10.3847/1538-4357/adb61d","title":"The JWST Resolved Stellar Populations Early Release Science Program. VIII. The Spatially Resolved Star Formation History of WLM","authors":[{"name":"Roger E. Cohen"},{"name":"Kristen B. W. McQuinn"},{"name":"Alessandro Savino"},{"name":"Max J. B. Newman"},{"name":"Daniel R. Weisz"},{"name":"Andrew E. Dolphin"},{"name":"Martha L. Boyer"},{"name":"Matteo Correnti"},{"name":"Marla C. Geha"},{"name":"Mario Gennaro"},{"name":"Karoline M. Gilbert"},{"name":"Nitya Kallivayalil"},{"name":"Jack T. Warfield"},{"name":"Benjamin F. Williams"},{"name":"Alyson M. Brooks"},{"name":"Andrew A. Cole"},{"name":"Evan D. Skillman"},{"name":"Christopher T. Garling"},{"name":"Jason S. Kalirai"},{"name":"Jay Anderson"}],"abstract":"Radial stellar population gradients within dwarf galaxies provide a promising avenue for disentangling the drivers of galaxy evolution, including environment. Within the Local Volume, radial stellar age gradient slopes correlate with interaction history, contrary to model predictions, so dwarfs that are isolated provide a critical control sample. We measure radial stellar age gradients in the relatively isolated gas-rich dwarf irregular Wolf–Lundmark–Melotte Galaxy (WLM), combining JWST NIRCam and NIRISS imaging with six archival Hubble Space Telescope fields over semimajor axis equivalent distances of 0 ≲  R _SMA  ≲ 4 kpc (≲3 R _hl ). Fitting lifetime star formation histories to resolved color–magnitude diagrams, radial age gradients are quantified using τ _90 and τ _50 , the lookback times to form 90% and 50% of the cumulative stellar mass. We find that globally, the outskirts of WLM are older on average, with ( δτ _90 , δτ _50 )/ δ R _SMA  = (0.82 ${}_{-0.10}^{+0.10}$ , 1.60 ${}_{-0.22}^{+0.23}$ ) Gyr kpc ^−1 (stat.), in good agreement with simulations. However, we also detect an azimuthal dependence of radial stellar age gradients, finding that stars on the leading edge of WLM (relative to its proper motion) are both younger and have a flatter age gradient compared to the trailing edge. This difference persists over 0.6 ≲  R _SMA  ≲ 3.2 kpc (∼0.5–2.5 R _hl ) and lookback times up to ∼8 Gyr, and is robust to the assumed stellar evolutionary model. Our results are consistent with star formation triggered by ram pressure stripping from a circumgalactic and/or intergalactic medium, suggested by recent H I observations. If confirmed, processes typifying dense environments, such as ram pressure stripping, may be more relevant to the evolution of isolated galaxies than previously thought.","source":"DOAJ","year":2025,"language":"","subjects":["Astrophysics"],"doi":"10.3847/1538-4357/adb61d","url":"https://doi.org/10.3847/1538-4357/adb61d","is_open_access":true,"published_at":"","score":69},{"id":"doaj_10.1088/2632-2153/ae1f05","title":"Towards instance-wise calibration: local amortized diagnostics and reshaping of conditional densities (LADaR)","authors":[{"name":"Biprateep Dey"},{"name":"David Zhao"},{"name":"Brett H Andrews"},{"name":"Jeffrey A Newman"},{"name":"Rafael Izbicki"},{"name":"Ann B Lee"}],"abstract":"Key science questions, such as galaxy distance estimation and weather forecasting, often require knowing the full predictive distribution of a target variable Y given complex inputs X . Despite recent advances in machine learning and physics-based models, it remains challenging to assess whether an initial model is calibrated for all x , and when needed, to reshape the densities of y toward ‘instance-wise’ calibration. This paper introduces the local amortized diagnostics and reshaping of conditional densities (LADaR) framework and proposes a new computationally efficient algorithm ( Cal-PIT ) that produces interpretable local diagnostics and provides a mechanism for adjusting conditional density estimates (CDEs). Cal-PIT learns a single interpretable local probability–probability map from calibration data that identifies where and how the initial model is miscalibrated across feature space, which can be used to morph CDEs such that they are well-calibrated. We illustrate the LADaR framework on synthetic examples, including probabilistic forecasting from image sequences, akin to predicting storm wind speed from satellite imagery. Our main science application involves estimating the probability density functions of galaxy distances given photometric data, where Cal-PIT achieves better instance-wise calibration than all 11 other literature methods in a benchmark data challenge, demonstrating its utility for next-generation cosmological analyzes ^9 .","source":"DOAJ","year":2025,"language":"","subjects":["Computer engineering. Computer hardware","Electronic computers. Computer science"],"doi":"10.1088/2632-2153/ae1f05","url":"https://doi.org/10.1088/2632-2153/ae1f05","is_open_access":true,"published_at":"","score":69},{"id":"arxiv_2601.04224","title":"Sustainable, Local Socio-Economic Development Through Astronomy","authors":[{"name":"Joyful E. Mdhluli"},{"name":"IAU Office of Astronomy for Development"}],"abstract":"Astronomy, often perceived as a distant or luxury science, holds immense potential as a driver for sustainable local socio-economic development. This paper explores how astronomy can create tangible benefits for communities through education, tourism, technology transfer, and capacity building. Using case studies from South Africa, Chile, Indonesia, and India, we demonstrate how astronomical facilities and initiatives have stimulated local economies, generated employment, supported small enterprises, and enhanced STEM participation, while simultaneously inspiring a sense of shared global heritage. The analysis identifies both successes and challenges, including unequal benefit distribution, limited local ownership, and sustainability gaps once external funding ends. Building on these lessons, we propose a practical framework/guidelines for designing, implementing, and evaluating astronomy-based community initiatives, rooted in participatory engagement and aligned with the UN Sustainable Development Goals (SDGs). This paper positions astronomy as a catalyst for inclusive growth, demonstrating that investment in the cosmos can translate into grounded, measurable benefits for people and places on Earth.","source":"arXiv","year":2025,"language":"en","subjects":["astro-ph.IM","physics.soc-ph"],"url":"https://arxiv.org/abs/2601.04224","pdf_url":"https://arxiv.org/pdf/2601.04224","is_open_access":true,"published_at":"2025-12-28T08:18:55Z","score":69},{"id":"arxiv_2507.15827","title":"Astrotourism for Development: An Overview of Resources from the IAU Office of Astronomy for Development","authors":[{"name":"Joyful E. Mdhluli"},{"name":"IAU Office of Astronomy for Development"}],"abstract":"Astrotourism has emerged as a powerful cross sectoral tool to promote science education, sustainable economic development, and cultural exchange. Recognising its potential, the International Astronomical Union's Office of Astronomy for Development (IAU OAD) has developed a suite of openly accessible resources to support individuals and institutions interested in implementing astrotourism initiatives globally. These resources also encourage individuals and existing businesses to broaden their offerings to include activities that use the night sky as a backdrop, such as food experiences, wellness practices, and cultural exploration. This paper offers a comprehensive summary of these resources, available on the OAD's Astrotourism Portal, and situates them within the broader context of astronomy for development work. The paper is targeted at educators, policymakers, tourism operators, grassroots organisers, and entrepreneurs, providing guidance on how they can foster inclusive, locally grounded, and sustainable astrotourism efforts, particularly in underresourced or emerging contexts.","source":"arXiv","year":2025,"language":"en","subjects":["astro-ph.IM","physics.soc-ph"],"url":"https://arxiv.org/abs/2507.15827","pdf_url":"https://arxiv.org/pdf/2507.15827","is_open_access":true,"published_at":"2025-07-21T17:36:22Z","score":69},{"id":"arxiv_2502.19433","title":"Recommended Actions for the American Astronomical Society: CSWA's Perspective on Steps for a more Inclusive Astronomy -- II. Recommendations","authors":[{"name":"Rachel Wexler"},{"name":"Patricia Knezek"},{"name":"Gregory Rudnick"},{"name":"Nicolle Zellner"},{"name":"Kathleen Eckert"},{"name":"JoEllen McBride"},{"name":"Maria Patterson"},{"name":"Christina Richey"},{"name":"the Committee on the Status of Women in Astronomy"}],"abstract":"This paper, the second in a series of two, provides a set of recommendations that the American Astronomical Society (AAS) can take to create a more diverse and inclusive professional society for astronomers, with a focus on women astronomers. As noted in Paper I, now is the time for the AAS to take decisive action to transform astronomy into a diverse and inclusive profession. By combining the results of our 2019 survey, which is described in Paper I, peer-reviewed academic literature, and findings from many of the white papers submitted to Astro2020, the CSWA has developed 26 specific actions the AAS can take to help end harassment and bullying in astronomy; advance career development for astronomers who are women, members of other underrepresented groups, and intersections of these populations; and improve the climate and culture of AAS meetings. Actions to reduce rates of harassment and bullying include improvements to the AAS's anti-harassment policies and procedures and the development of astronomy-specific anti-harassment training resources. Actions to advance career development include creating a compensation database, improving how jobs are posted in the AAS Job Register, and supporting/enhancing a distance mentorship program. Finally, we call on the AAS to continue improving the accessibility of AAS meetings and to continue to support meeting sessions whose focus is to discuss issues of equity, diversity, and inclusion.","source":"arXiv","year":2025,"language":"en","subjects":["physics.soc-ph","astro-ph.IM"],"doi":"10.3847/25c2cfeb.144eafda","url":"https://arxiv.org/abs/2502.19433","pdf_url":"https://arxiv.org/pdf/2502.19433","is_open_access":true,"published_at":"2025-02-15T19:27:58Z","score":69},{"id":"arxiv_2502.19432","title":"Recommended Actions for the American Astronomical Society: CSWA's Perspective on Steps for a more Inclusive Astronomy -- I. Background and Methods","authors":[{"name":"Rachel Wexler"},{"name":"Patricia Knezek"},{"name":"Gregory Rudnick"},{"name":"Nicolle Zellner"},{"name":"Kathleen Eckert"},{"name":"JoEllen McBride"},{"name":"Maria Patterson"},{"name":"Christina Richey"},{"name":"the Committee on the Status of Women in Astronomy"}],"abstract":"In a series of two papers, we provide a comprehensive agenda of actions the American Astronomical Society (AAS) can take to create a more diverse and inclusive professional system for astronomers, with a focus on women astronomers. This first paper of the series outlines the background and methods, while the recommendations are treated in the second companion paper (Paper II). We take the stance that since the 2020 Decadal Survey (Astro2020) was delivered in 2021, with its first-ever set of recommendations on the State of the Profession, now is the time for the AAS to take decisive action to transform astronomy into a diverse and inclusive profession. In the spring of 2019, the CSWA surveyed the astronomical community to assess the popularity and feasibility of actions that the AAS can take to reduce harassment and advance career development for women in astronomy. Here we present the quantitative results of that survey and a synopsis of the free response sections, which are publicly accessible. By combining the results of our survey, peer-reviewed academic literature, and findings from many of the white papers submitted to Astro2020, the CSWA has developed 26 specific actions that the AAS can take to help end harassment in astronomy, to advance career development for astronomers who are women and who are other members of historically marginalized groups, and intersections of these populations, and to improve the climate and culture of AAS and AAS-sponsored meetings. This paper presents the data we used to make these recommendations, and the recommendations themselves will be presented in Paper II.","source":"arXiv","year":2025,"language":"en","subjects":["physics.soc-ph","astro-ph.IM"],"doi":"10.3847/25c2cfeb.cdff43a1","url":"https://arxiv.org/abs/2502.19432","pdf_url":"https://arxiv.org/pdf/2502.19432","is_open_access":true,"published_at":"2025-02-15T19:20:40Z","score":69},{"id":"arxiv_2501.04333","title":"Gravitational physics in the context of Indian astronomy: A vision document","authors":[{"name":"P. Ajith"},{"name":"K. G. Arun"},{"name":"Sukanta Bose"},{"name":"Sumanta Chakraborty"},{"name":"Shantanu Desai"},{"name":"A. Gopakumar"},{"name":"Sanved Kolekar"},{"name":"Rajesh Nayak"},{"name":"Archana Pai"},{"name":"Sudipta Sarkar"},{"name":"Jasjeet Singh Bagla"},{"name":"Patrick Das Gupta"},{"name":"Rahul Kashyap"},{"name":"Prashant Kocherlakota"},{"name":"Prayush Kumar"},{"name":"Banibrata Mukhopadhyay"}],"abstract":"Contributions from the Indian gravity community have played a significant role in shaping several branches of astronomy and astrophysics. This document reviews some of the most important contributions and presents a vision for gravity research in the context of astronomy \\\u0026 astrophysics in India. This is an expanded version of one of the chapters in the recently released Vision Document of the Astronomical Society of India.","source":"arXiv","year":2025,"language":"en","subjects":["astro-ph.IM","astro-ph.HE","gr-qc"],"doi":"10.1007/s12036-024-10031-x","url":"https://arxiv.org/abs/2501.04333","pdf_url":"https://arxiv.org/pdf/2501.04333","is_open_access":true,"published_at":"2025-01-08T08:10:38Z","score":69},{"id":"doaj_10.3390/e26030260","title":"Restoring the Fluctuation–Dissipation Theorem in Kardar–Parisi–Zhang Universality Class through a New Emergent Fractal Dimension","authors":[{"name":"Márcio S. Gomes-Filho"},{"name":"Pablo de Castro"},{"name":"Danilo B. Liarte"},{"name":"Fernando A. Oliveira"}],"abstract":"The Kardar–Parisi–Zhang (KPZ) equation describes a wide range of growth-like phenomena, with applications in physics, chemistry and biology. There are three central questions in the study of KPZ growth: the determination of height probability distributions; the search for ever more precise universal growth exponents; and the apparent absence of a fluctuation–dissipation theorem (FDT) for spatial dimension \u003cinline-formula\u003e\u003cmath xmlns=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"\u003e\u003csemantics\u003e\u003cmrow\u003e\u003cmi\u003ed\u003c/mi\u003e\u003cmo\u003e\u003e\u003c/mo\u003e\u003cmn\u003e1\u003c/mn\u003e\u003c/mrow\u003e\u003c/semantics\u003e\u003c/math\u003e\u003c/inline-formula\u003e. Notably, these questions were answered exactly only for \u003cinline-formula\u003e\u003cmath xmlns=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"\u003e\u003csemantics\u003e\u003cmrow\u003e\u003cmn\u003e1\u003c/mn\u003e\u003cmo\u003e+\u003c/mo\u003e\u003cmn\u003e1\u003c/mn\u003e\u003c/mrow\u003e\u003c/semantics\u003e\u003c/math\u003e\u003c/inline-formula\u003e dimensions. In this work, we propose a new FDT valid for the KPZ problem in \u003cinline-formula\u003e\u003cmath xmlns=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"\u003e\u003csemantics\u003e\u003cmrow\u003e\u003cmi\u003ed\u003c/mi\u003e\u003cmo\u003e+\u003c/mo\u003e\u003cmn\u003e1\u003c/mn\u003e\u003c/mrow\u003e\u003c/semantics\u003e\u003c/math\u003e\u003c/inline-formula\u003e dimensions. This is achieved by rearranging terms and identifying a new correlated noise which we argue to be characterized by a fractal dimension \u003cinline-formula\u003e\u003cmath xmlns=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"\u003e\u003csemantics\u003e\u003cmsub\u003e\u003cmi\u003ed\u003c/mi\u003e\u003cmi\u003en\u003c/mi\u003e\u003c/msub\u003e\u003c/semantics\u003e\u003c/math\u003e\u003c/inline-formula\u003e. We present relations between the KPZ exponents and two emergent fractal dimensions, namely \u003cinline-formula\u003e\u003cmath xmlns=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"\u003e\u003csemantics\u003e\u003cmsub\u003e\u003cmi\u003ed\u003c/mi\u003e\u003cmi\u003ef\u003c/mi\u003e\u003c/msub\u003e\u003c/semantics\u003e\u003c/math\u003e\u003c/inline-formula\u003e, of the rough interface, and \u003cinline-formula\u003e\u003cmath xmlns=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"\u003e\u003csemantics\u003e\u003cmsub\u003e\u003cmi\u003ed\u003c/mi\u003e\u003cmi\u003en\u003c/mi\u003e\u003c/msub\u003e\u003c/semantics\u003e\u003c/math\u003e\u003c/inline-formula\u003e. Also, we simulate KPZ growth to obtain values for transient versions of the roughness exponent \u003cinline-formula\u003e\u003cmath xmlns=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"\u003e\u003csemantics\u003e\u003cmi\u003eα\u003c/mi\u003e\u003c/semantics\u003e\u003c/math\u003e\u003c/inline-formula\u003e, the surface fractal dimension \u003cinline-formula\u003e\u003cmath xmlns=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"\u003e\u003csemantics\u003e\u003cmsub\u003e\u003cmi\u003ed\u003c/mi\u003e\u003cmi\u003ef\u003c/mi\u003e\u003c/msub\u003e\u003c/semantics\u003e\u003c/math\u003e\u003c/inline-formula\u003e and, through our relations, the noise fractal dimension \u003cinline-formula\u003e\u003cmath xmlns=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"\u003e\u003csemantics\u003e\u003cmsub\u003e\u003cmi\u003ed\u003c/mi\u003e\u003cmi\u003en\u003c/mi\u003e\u003c/msub\u003e\u003c/semantics\u003e\u003c/math\u003e\u003c/inline-formula\u003e. Our results indicate that KPZ may have at least two fractal dimensions and that, within this proposal, an FDT is restored. Finally, we provide new insights into the old question about the upper critical dimension of the KPZ universality class.","source":"DOAJ","year":2024,"language":"","subjects":["Science","Astrophysics","Physics"],"doi":"10.3390/e26030260","url":"https://www.mdpi.com/1099-4300/26/3/260","is_open_access":true,"published_at":"","score":68},{"id":"doaj_10.1140/epjc/s10052-024-12616-w","title":"Gravitationally induced unified relation among duality, coherence, steering, and maximal average fidelity","authors":[{"name":"Duo-Duo Chen"},{"name":"Dong-Dong Dong"},{"name":"Xue-Ke Song"},{"name":"Liu Ye"},{"name":"Dong Wang"}],"abstract":"Abstract Recently, numerous measures have been proposed for quantifying the quantumness of a given system, and the existence of intrinsic connections among quantum resource measures has been proven. Here, we study the unified relationship between duality, first-order coherence, three-setting linear steering inequality, and maximum average fidelity between two masses due to gravity. Under gravitational inducement, an equivalent relationship was identified between the first-order coherence and duality. The coherence of a system can be controlled by adjusting arm lengths and the distance between the arms of an interferometer. In most cases, the first-order coherence of a system cannot be maximised. Furthermore, a trade-off relationship between gravitationally induced duality and steering violations was derived. We can adjust the arm length and distance between the arms of the interferometer such that the steering violation reaches its maximum at phase $$\\pi $$ π . The results show that the value of the steering violation is always greater than 1; that is, the state of the system is steerable. In addition, we explored the intrinsic relationship between duality and the maximal average fidelity due to gravity. In most cases, the maximum average fidelity of the system is greater than 2/3, indicating that the state is useful for quantum teleportation. These results are important for investigating the intrinsic relationships among various quantum resources within the framework of gravity.","source":"DOAJ","year":2024,"language":"","subjects":["Astrophysics","Nuclear and particle physics. Atomic energy. Radioactivity"],"doi":"10.1140/epjc/s10052-024-12616-w","url":"https://doi.org/10.1140/epjc/s10052-024-12616-w","is_open_access":true,"published_at":"","score":68},{"id":"arxiv_2407.00335","title":"Journey of X-ray astronomy: Indian perspectives","authors":[{"name":"A R Rao"}],"abstract":"X-ray astronomy is a mature area of observational astronomy. After the discovery of the first non-solar X-ray source in 1962, X-ray astronomy proliferated during the Apollo era's space race. Then, it matured as an established area of research during the period of Great Observatories, and now it has become an indispensable tool to understand a wide variety of astrophysical phenomena. Consequently, in recent times, niche observational areas in X-ray astronomy have been explored, and attempts have been made to expand the sensitivity of observations vastly. India was an active partner in the growth of X-ray astronomy. In the initial years, India leveraged its expertise in balloon technology to get significant results in the research area of hard X-ray astronomy. During the rapid growth phase of X-ray astronomy, India made divergent all-round efforts. Later on, however, the technical expertise available in India was insufficient to compete with the highly sophisticated satellite experiments from around the world. During this phase, work in X-ray astronomy continued in a few low-key experiments, eventually resulting in the launch of India's first multi-wavelength astronomical satellite, AstroSat, in 2015. In this article, I will trace the journey of X-ray astronomy and the developments in the Indian context. I will also explore the sociological aspects of the growth of X-ray astronomy, and, in the end, I will present a speculative sketch of the future of X-ray astronomy with an emphasis on the Indian contribution.","source":"arXiv","year":2024,"language":"en","subjects":["astro-ph.IM"],"url":"https://arxiv.org/abs/2407.00335","pdf_url":"https://arxiv.org/pdf/2407.00335","is_open_access":true,"published_at":"2024-06-29T06:40:59Z","score":68},{"id":"doaj_10.22034/ijism.2022.1977746.0","title":"Social Network Analysis of Editorial Board Interlocking Phenomena from the Perspective of Astronomy and Astrophysics Journals","authors":[{"name":"Farshid Danesh"},{"name":"Samaneh Kesht Karan"},{"name":"Lili Banihashemi"},{"name":"Somayeh GhaviDel"}],"abstract":"Editorial board members (EBMs) of journals play a pivotal role in authentic international scientific journals. Editorial Board Interlocking (EBI) phenomenon reflects the effectiveness and importance of the scholarly journal's editorial boards in various scientific fields. The primary purpose of this paper is to conduct a Social Network Analysis (SNA) of EBI phenomena from the perspective of astronomy and astrophysics journals. The present study is applied research based on EBI, SNA, and the descriptive-analytical approach. The statistical population of this study consists of the editorial board members of all journals of astronomy and astrophysics indexed in the JCR and official journal websites. There are 1597 job positions in 67 astronomy and astrophysics journals occupied by the 1394 scholars. Data analysis shows EBI for 95 scholars and 79 organizations. \"Aleksei A. Starobinsky\" from Russia and the Russian Academy of Sciences, \"Daniel J. Scheeres\" from the United States, and the University of Colorado Boulder have the highest EBI contributions in five journals. \"Daniel J. Scheeres,\" with a centrality of 39, has the highest degree of centrality measurement among the EBMs. The presence of more than five times as many men as women indicates that astronomy and astrophysics journals are considered \"masculine\" by the editorial board. The EBI phenomenon is observed in astronomy and astrophysics journals due to the limited number of peop le eligible for the editorial board. Due to EBI, a limited number of famous scholars are made macro-policies such as publishing the articles, referees selections, and the reviewing process. Astronomy and astrophysics journals have \"elite\" academic networks. Gender inequality exists among EBMs, and the majority of them are male. Accordingly, these journals are \"men's journals.\"","source":"DOAJ","year":2023,"language":"","subjects":["Information resources (General)","Transportation and communications"],"doi":"10.22034/ijism.2022.1977746.0","url":"https://ijism.ricest.ac.ir/article_700756_9208d514293adf1eaa17de5955477120.pdf","pdf_url":"https://ijism.ricest.ac.ir/article_700756_9208d514293adf1eaa17de5955477120.pdf","is_open_access":true,"published_at":"","score":67},{"id":"doaj_10.1029/2023GL104610","title":"Shocklets and Short Large Amplitude Magnetic Structures (SLAMS) in the High Mach Foreshock of Venus","authors":[{"name":"Glyn A. Collinson"},{"name":"Heli Hietala"},{"name":"Ferdinand Plaschke"},{"name":"Tomas Karlsson"},{"name":"Lynn B. Wilson III"},{"name":"Martin Archer"},{"name":"Markus Battarbee"},{"name":"Xochitl Blanco‐Cano"},{"name":"Cesar Bertucci"},{"name":"David Long"},{"name":"Merav Opher"},{"name":"Nick Sergis"},{"name":"Claire Gasque"},{"name":"Terry Liu"},{"name":"Savvas Raptis"},{"name":"Sofia Burne"},{"name":"Rudy Frahm"},{"name":"Tielong Zhang"},{"name":"Yoshifumi Futaana"}],"abstract":"Abstract Shocklets and short large‐amplitude magnetic structures (SLAMS) are steepened magnetic fluctuations commonly found in Earth's upstream foreshock. Here we present Venus Express observations from the 26th of February 2009 establishing their existence in the steady‐state foreshock of Venus, building on a past study which found SLAMS during a substantial disturbance of the induced magnetosphere. The Venusian structures were comparable to those reported near Earth. The 2 Shocklets had magnetic compression ratios of 1.23 and 1.34 with linear polarization in the spacecraft frame. The 3 SLAMS had ratios between 3.22 and 4.03, two of which with elliptical polarization in the spacecraft frame. Statistical analysis suggests SLAMS coincide with unusually high solar wind Alfvén mach‐number at Venus (12.5, this event). Thus, while we establish Shocklets and SLAMS can form in the stable Venusian foreshock, they may be rarer than at Earth. We estimate a lower limit of their occurrence rate of ≳14%.","source":"DOAJ","year":2023,"language":"","subjects":["Geophysics. Cosmic physics"],"doi":"10.1029/2023GL104610","url":"https://doi.org/10.1029/2023GL104610","is_open_access":true,"published_at":"","score":67},{"id":"doaj_10.3847/2041-8213/acab5d","title":"Evidence for Enrichment of Niobium-92 in the Outer Protosolar Disk","authors":[{"name":"Yuki Hibiya"},{"name":"Tsuyoshi Iizuka"},{"name":"Hatsuki Enomoto"},{"name":"Takehito Hayakawa"}],"abstract":"The short-lived radionuclide, niobium-92 ( ^92 Nb), has been used to estimate the site of nucleosynthesis for p- nuclei and the timing of planetary differentiation, assuming that it was uniformly distributed in the early solar system. Here, we present the internal niobium–zirconium (Nb–Zr) isochron dating of Northwest Africa (NWA) 6704, an achondrite thought to form in the outer protosolar disk due to nucleosynthetic isotope similarities with carbonaceous chondrites. The isochron defines an initial ^92 Nb/ ^93 Nb ratio of (2.72 ± 0.25) × 10 ^−5 at the NWA 6704 formation, 4562.76 ± 0.30 million years ago. This corresponds to a ^92 Nb/ ^93 Nb ratio of (2.96 ± 0.27) × 10 ^−5 at the time of solar system formation, which is ∼80% higher than the values obtained from meteorites formed in the inner disk. The results suggest that a significant proportion of the solar ^92 Nb was produced by a nearby core-collapse supernova (CCSN) and that the outer disk was more enriched in CCSN ejecta, which could account for the heterogeneity of short-lived ^26 Al and nucleosynthetic stable-isotope anomalies across the disk. We propose that NWA 6704 serves as the best anchor for mapping relative Nb–Zr ages of objects in the outer solar system onto the absolute timescale.","source":"DOAJ","year":2023,"language":"","subjects":["Astrophysics"],"doi":"10.3847/2041-8213/acab5d","url":"https://doi.org/10.3847/2041-8213/acab5d","is_open_access":true,"published_at":"","score":67},{"id":"arxiv_2310.13407","title":"Preserving your skies since 1988 -- Committee on Radio Astronomy Frequencies (CRAF) -- Periodic Review 2011-2021","authors":[{"name":"Committee on Radio Astronomy Frequencies"},{"name":"Benjamin Winkel"},{"name":"Simon Garrington"},{"name":"Francesco Colomer"},{"name":"Waleed Madkour"},{"name":"Agnieszka Slowikowska"},{"name":"Pietro Bolli"},{"name":"Michael Lindqvist"},{"name":"José Antonio López-Pérez"},{"name":"Leif Morten Tangen"},{"name":"Ivan Thomas"},{"name":"Peter Thomasson"},{"name":"Roel Witvers"},{"name":"Joe McCauley"},{"name":"Marta Bautista"},{"name":"Miguel Bergano"},{"name":"Vladislavs Bezrukovs"},{"name":"Fabio Giovanardi"},{"name":"Hayo Hase"},{"name":"Karel Jiricka"},{"name":"Gyula I. G. Józsa"},{"name":"Juha Kallunki"},{"name":"Christophe Marqué"},{"name":"Derek McKay"},{"name":"Axel Murk"},{"name":"Vincent Pietu"},{"name":"Vincenza Tornatore"},{"name":"Busang Sethole"},{"name":"Marian Soida"},{"name":"Boris Sorokin"},{"name":"Gie Han Tan"},{"name":"Adrian Tiplady"},{"name":"L. Viktor Tóth"},{"name":"Federico Di Vruno"},{"name":"Susanne Wampfler"},{"name":"Andrew Williams"},{"name":"Serge Yerin"},{"name":"Justin Bray"},{"name":"Axel Jessner"},{"name":"Nectaria Gizani"},{"name":"Christian Monstein"},{"name":"Mike Peel"},{"name":"João Salmim Ferreira"},{"name":"Harry Smith"},{"name":"Giorgios P. Veldes"},{"name":"Pawel Wolak"}],"abstract":"The Committee on Radio Astronomy Frequencies (CRAF) is an Expert Committee of the European Science Foundation. It aims to provide a cost-effective single voice on frequency protection issues for European radio astronomy observatories and research institutes, achieving a significantly greater impact than that achievable by individual national institutions. By working together, European observatories and institutes can profit from synergy effects, cover many more topics, and learn from each other. CRAF was founded in 1988 and has since then been engaged with the International Telecommunication Union (ITU), in particular its Radiocommunication Sector (ITU-R), and the European Conference of Postal and Telecommunications Administrations (CEPT) and its European Communications Committee (ECC). This is the self-evaluation report prepared by CRAF for its periodic review of the years 2011-2021.","source":"arXiv","year":2023,"language":"en","subjects":["astro-ph.IM"],"url":"https://arxiv.org/abs/2310.13407","pdf_url":"https://arxiv.org/pdf/2310.13407","is_open_access":true,"published_at":"2023-10-20T10:24:54Z","score":67},{"id":"crossref_10.3390/astronomy2010002","title":"Acknowledgment to the Reviewers of Astronomy in 2022","authors":[{"name":"Astronomy Editorial Office"}],"abstract":"High-quality academic publishing is built on rigorous peer review [...]","source":"CrossRef","year":2023,"language":"en","subjects":null,"doi":"10.3390/astronomy2010002","url":"https://doi.org/10.3390/astronomy2010002","is_open_access":true,"published_at":"","score":67},{"id":"doaj_10.1063/9.0000307","title":"Spin dynamics in permalloy nano-ellipses for honeycomb and square lattices","authors":[{"name":"Wonbae Bang"},{"name":"M. T. Kaffash"},{"name":"M. T. Hossain"},{"name":"A. Hoffmann"},{"name":"J. B. Ketterson"},{"name":"M. B. Jungfleisch"}],"abstract":"We report experimental and theoretical studies of spin dynamics in lattice structures of permalloy (Ni80Fe20) nano-ellipses, with four different types of networks including honeycomb and square lattices. The lattices are patterned at the center line of the co-planar wave guide and consist of non-contacting or contacting ellipses. Micromagnetic simulations show excellent agreement with the broadband ferromagnetic resonance (FMR) experimental results. We find the existence of a spin-wave mode localized in the vertex region of the contacting nano-ellipse network. Our finding has important implications when designing an artificial spin ice (ASI) network for functional magnonics.","source":"DOAJ","year":2022,"language":"","subjects":["Physics"],"doi":"10.1063/9.0000307","url":"http://dx.doi.org/10.1063/9.0000307","is_open_access":true,"published_at":"","score":66},{"id":"doaj_10.1088/1367-2630/ac7df6","title":"Inferring Markovian quantum master equations of few-body observables in interacting spin chains","authors":[{"name":"Francesco Carnazza"},{"name":"Federico Carollo"},{"name":"Dominik Zietlow"},{"name":"Sabine Andergassen"},{"name":"Georg Martius"},{"name":"Igor Lesanovsky"}],"abstract":"Full information about a many-body quantum system is usually out-of-reach due to the exponential growth—with the size of the system—of the number of parameters needed to encode its state. Nonetheless, in order to understand the complex phenomenology that can be observed in these systems, it is often sufficient to consider dynamical or stationary properties of local observables or, at most, of few-body correlation functions. These quantities are typically studied by singling out a specific subsystem of interest and regarding the remainder of the many-body system as an effective bath. In the simplest scenario, the subsystem dynamics, which is in fact an open quantum dynamics, can be approximated through Markovian quantum master equations. Here, we formulate the problem of finding the generator of the subsystem dynamics as a variational problem, which we solve using the standard toolbox of machine learning for optimization. This dynamical or ‘Lindblad’ generator provides the relevant dynamical parameters for the subsystem of interest. Importantly, the algorithm we develop is constructed such that the learned generator implements a physically consistent open quantum time-evolution. We exploit this to learn the generator of the dynamics of a subsystem of a many-body system subject to a unitary quantum dynamics. We explore the capability of our method to recover the time-evolution of a two-body subsystem and exploit the physical consistency of the generator to make predictions on the stationary state of the subsystem dynamics.","source":"DOAJ","year":2022,"language":"","subjects":["Science","Physics"],"doi":"10.1088/1367-2630/ac7df6","url":"https://doi.org/10.1088/1367-2630/ac7df6","is_open_access":true,"published_at":"","score":66}],"total":268831,"page":1,"page_size":20,"sources":["DOAJ","arXiv","CrossRef"],"query":"Astronomy"}