Abstract A line of first-order phase transitions is conjectured in the phase diagram of Quantum Chromodynamics at non-zero baryon density. If this is the case, numerical simulations of neutron star mergers suggest that various regions of the stars may cross this line multiple times. This results in the nucleation of bubbles of the preferred phase, which subsequently expand and collide. The resulting gravitational wave spectrum is highly sensitive to the velocity of the bubble walls. We use holography to perform the first microscopic simulation of bubble dynamics in a theory that qualitatively mirrors the expected phase diagram of Quantum Chromodynamics. We determine the wall velocity in the metastable regions and we compare it to theoretical estimates. We discuss implications for gravitational wave production.
Nuclear and particle physics. Atomic energy. Radioactivity
Gravitational waves (GWs) accompanied by electromagnetic counterparts, known as bright sirens, provide a novel methodology to measure the Hubble constant ( H _0 ). However, the rarity of such multimessenger events limits the precision of the H _0 constraint. Recently, the newly discovered class of nuclear transient, quasiperiodic eruptions (QPEs), shows intriguing evidence of a stellar-mass companion captured by a supermassive black hole in an extreme/intermediate mass ratio inspiral, which is the most promising source of space-based GW detectors, such as LISA. Here, we model the secular orbital evolution of known QPE systems using two frameworks: a stripping scenario in which periodic mass transfer at periapsis drives the evolution, and an orbiter–disk collision scenario in which the companion interacts with a misaligned accretion disk, modulated by coupled orbiter–disk precession. For each framework, we assess detectability by LISA, together with the resulting constraints on H _0 . Our principal findings are (i) in the stripping scenario, no currently known QPE reaches detectability within a four-year LISA mission; (ii) in the orbiter–disk scenario, two sources—eRO-QPE2 and eRO-QPE4—are detectable with signal-to-noise ratios ≃8.5–28.8 and constrain H _0 with a fractional uncertainty of 6.7%–14.9%. QPE systems remain uncertain on the decade-long secular evolution. Therefore, they motivate continued time-domain monitoring of QPE candidates.
The ongoing exponential growth of computational power, and the growth of the commercial High Performance Computing (HPC) industry, has led to a point where ten commercial systems currently exceed the performance of the highest-used HPC system in radio astronomy in Australia, and one of these exceeds the expected requirements of the Square Kilometre Array (SKA) Science Data Processors. In order to explore implications of this emerging change in the HPC landscape for radio astronomy, we report results from a survey conducted via semi-structured interviews with 14 Australian scientists and providers with experience of commercial HPC in astronomy and similar data intensive fields. We supplement these data with learnings from two earlier studies in which we investigated the application of commercial HPC to radio astronomy data processing, using cases with very different data and processing considerations. We use the established qualitative research approach of thematic analysis to extract key messages from our interviews. We find that commercial HPC can provide major advantages in accessibility and availability, and may contribute to increasing researchers' career productivity. Significant barriers exist, however, including the need for access to increased expertise in systems programming and parallelisation, and a need for recognition in research funding. We comment on potential solutions to these issues.
The Office of Astronomy for Development (OAD) believes that in order for astronomy-for-development activities to be effective, a scientific approach is required. Evaluation is an essential component in identifying which projects work best, for whom and under what conditions. Evidence-informed project design and selection ensures that projects build on past lessons, thereby reducing the risk of negative unintended consequences and increasing the probabilities of positive cost-effective impact. The OAD has developed an Impact Cycle that aims to enhance project design, selection and delivery systems to support such continual improvement and potential expansion. By determining what works - and, importantly, what doesn't work - the OAD can build a library of evidence on best practice and ensure a positive feedback loop for future projects.
The term artificial intelligence (AI) first appeared in the mid-20th century. It wasn't until well into the 21st century that AI began to flourish. Today, AI has found very diverse applications. One area that is just beginning to be explored is physics education. The aim of this work is to contribute to this burgeoning educational field through a ChatGPT application named Networked Observatory for Virtual Astronomy (NOVA). This application provides students with simulated astronomical data in a ChatGPT-based environment, where they can put their scientific skills to work by formulating hypotheses, analyzing data, and drawing verifiable conclusions through interaction with ChatGPT.
Priscilla Muheki, Mirjana Pović, Somaya Saad
et al.
In preparation for the International Astronomical Union (IAU) General Assembly (GA) 2024, the first GA held in Africa, the African Network of Women in Astronomy (AfNWA) embarked on a visionary project: the creation of an inspiring storytelling book that showcases the remarkable journeys of professional female astronomers in Africa. This book is not merely a collection of biographies; it is a tapestry of resilience, passion, and scientific excellence woven through the lives of women who have ventured into the cosmos from the African continent. The primary aim of this book is twofold. Firstly, it seeks to bring greater visibility to women astronomers in Africa, highlighting their groundbreaking research and the personal stories that have shaped their careers. By shining a light on their achievements and awards, we hope to acknowledge their contributions to the field of astronomy and underscore the importance of diversity in science. Secondly, this book aspires to inspire and empower the next generation of scientists, particularly young women and girls across Africa. Through the personal narratives and professional achievements of these trailblazing astronomers and students in astronomy, we aim to spark curiosity, foster a love for science, and demonstrate that the sky is not the limit but just the beginning for those who dare to dream. As you delve into the stories within these pages, you will encounter a rich array of experiences and insights that reflect the unique challenges and triumphs women face in astronomy. From overcoming societal barriers to making groundbreaking discoveries, these women have carved paths that others can follow, proving that with determination and passion, the stars are within reach for everyone.
The inflated radii of hot Jupiters have been explored by various theoretical mechanisms. By connecting planetary thermal evolution models with the observed properties of hot Jupiters using hierarchical Bayesian models, a theoretical parameter called the heating efficiency has been introduced to describe the heating of the interiors of these planets. Previous studies have shown that the marginal distribution of this heating-efficiency parameter has a single-peak distribution along the planetary equilibrium temperature ( T _eq ). Since the observed properties of hot Jupiters are the foundation of these Bayesian inference models, there must be a corresponding feature in the observed data that leads to the inferred single-peak distribution of the heating efficiency. This study aims to find the underlying cause of the single-peak heating-efficiency distribution without relying on specific theoretical models. By analyzing the relationships between different observed physical properties, we obtain a similar single-peak distribution of the radius expansion efficiency of hot Jupiters along T _eq , which can be explained by the correlation with the stellar effective temperature. However, a detailed investigation suggests that this single-peak distribution is actually the result of straightforward physical processes. Specifically, the increase in heating efficiency can be attributed to the increase in incident stellar flux, while the decrease in heating efficiency can be attributed to the rise in the gravitational binding energy associated with the increase in planetary mass.
پژوهش حاضر، عملکرد دادههای بازتحلیل در بازتولید پارامترهای دما و رطوبت طی دوره 1990 تا 2020 را در 9 ایستگاه جو بالا با دوبار گمانهزنی در روز ارزیابی میکند. پارامترهای مورد بررسی شامل دما، دمای نقطه شبنم، رطوبت ویژه، آهنگ کاهش دما ( در لایههای یک کیلومتری، سه کیلومتری و سه تا شش کیلومتری از سطح) و نسبت اختلاط در ارتفاعهای 100، 300 و 500 متری از سطح زمین بود. شاخصهای آماری اریبی، همبستگی، ریشه میانگین مربعات خطا و شاخص توافق استفاده شد. نتایج نشان داد که دادههای بازتحلیل دمای هوا در تراز 850 هکتوپاسکال را در شب/روز فراتخمین/فروتخمین کردهاند؛ اما در ترازهای بالاتر دقت و همبستگی بیشتری داشتند. دمای نقطه شبنم بازتحلیل در ترازهای 700 و 500 هکتوپاسکال در اغلب موارد بیشبرآورد شده بودند و میزان خطا در تراز 500 بیشتر از 700 هکتوپاسکال بود. دقت برآورد آهنگ کاهش دما در یک کیلومتر ابتدایی جو در اغلب ایستگاهها پایین بود و پدیدههایی، مانند، سرمایش سطحی و وارونگی دما به دقت بازیابی نشدند. پارامترهای رطوبتی نیز در سطوح پایین جو بهویژه در شب بیشبرآورد شدند. نسبت اختلاط در ارتفاعهای 100، 300 و 500 متری در تمامی ایستگاهها بهجز اهواز، بهویژه در شب بیشبرآورد شدند. ایستگاه اهواز با کمترین ارتفاع از سطح دریا، هم در شب و هم در روز فروتخمین نسبت اختلاط را تجربه کرد. نتایج نشان میدهد که در این منطقه عملکرد دادههای بازتحلیل در سطوح پایین جو نسبت به سطوح بالاتر از دقت کمتری برخوردار است و نیاز به اصلاح یا تلفیق با دادههای مشاهداتی دارد.
Rahul K. Kushwaha, Murthy S. Gudipati, Bryana L. Henderson
Amorphous ice is understood to be the predominant phase of water in cometary nuclei. A significant number of other volatiles can be trapped in amorphous H _2 O ice and released during the amorphous-to-crystalline phase transition (ACPT). This phase transition is an exothermic and is considered a potential cause of cometary outbursts, such as those observed in Comet 1P/Halley and Comet Hale–Bopp. However, only a single experimental study reported in the literature suggests that the presence of impurities (>2%) in amorphous H _2 O ice suppresses the exothermic effect and results in an endothermic phase transition, which contradicts the hypothesis of exothermic-phase-transition-driven comet outbursts. To further explore this phenomenon, we conducted experiments on pure H _2 O, CO:H _2 O, and CO _2 :H _2 O ice mixtures with varying fractions (11%, 50%, and 80% CO, and 11%, 25%, and 50% CO _2 , both relative to H _2 O (100%)). Our experimental setup is a highly sensitive cryogenic differential scanning calorimeter with a μ K noise floor and fifth-decimal resolution in temperature ratio of reference and ice. Our calorimetric data have been internally calibrated to ice sublimation endotherm to derive quantitative calorimetric data. We find that ACPT is exothermic in all CO:H _2 O mixtures and CO _2 :H _2 O mixtures with lower CO _2 fractions. In mixtures with the highest CO _2 content (50% relative to H _2 O (100%)) examined, the ACPT exotherm is weakened. Our results demonstrate that ACPT exothermicity persists throughout the CO and CO _2 mixing ratios observed in a majority of comets, and it should play an important role in comet outbursts when CO and CO _2 are the major volatiles trapped in amorphous H _2 O ice.
This brief review is based on a lecture given by one of the authors at the international youth conference AYSS-2023. It is devoted to multimessenger astronomy, which studies astrophysical objects and phenomena using various particles and waves that bring information from space. The messengers include electromagnetic and gravitational waves, neutrinos, and cosmic rays. We discuss new opportunities that open up with the combined use of several carriers of information. Combination of data obtained through various observation channels allows one to obtain more complete and accurate information about the processes occurring in the Universe, and even to use it for studying fundamental physics.
Rapid progress in the capabilities of machine learning approaches in natural language processing has culminated in the rise of large language models over the last two years. Recent works have shown unprecedented adoption of these for academic writing, especially in some fields, but their pervasiveness in astronomy has not been studied sufficiently. To remedy this, we extract words that ChatGPT uses more often than humans when generating academic text and search a total of 1 million articles for them. This way, we assess the frequency of word occurrence in published works in astronomy tracked by the NASA Astrophysics Data System since 2000. We then perform a statistical analysis of the occurrences. We identify a list of words favoured by ChatGPT and find a statistically significant increase for these words against a control group in 2024, which matches the trend in other disciplines. These results suggest a widespread adoption of these models in the writing of astronomy papers. We encourage organisations, publishers, and researchers to work together to identify ethical and pragmatic guidelines to maximise the benefits of these systems while maintaining scientific rigour.
By compressing matter to densities up to several times the density of atomic nuclei, the catastrophic gravitational collapse of the core of stars with a mass <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>M</mi><mo>≳</mo><mn>8</mn><msub><mi>M</mi><mo>⊙</mo></msub></mrow></semantics></math></inline-formula> during supernova explosions and the neutron star left behind (see, e [...]
Coded computing is recognized as a promising solution to address the privacy leakage problem and the straggling effect in distributed computing. This technique leverages coding theory to recover computation tasks using results from a subset of workers. In this paper, we propose the adaptive privacy-preserving coded computing (APCC) strategy, designed to be applicable to various types of computation tasks, including polynomial and non-polynomial functions, and to adaptively provide accurate or approximated results. We prove the optimality of APCC in terms of encoding rate, defined as the ratio between the computation loads of tasks before and after encoding, based on the optimal recovery threshold of Lagrange Coded Computing. We demonstrate that APCC guarantees information-theoretical data privacy preservation. Mitigation of the straggling effect in APCC is achieved through hierarchical task partitioning and task cancellation, which further reduces computation delays by enabling straggling workers to return partial results of assigned tasks, compared to conventional coded computing strategies. The hierarchical task partitioning problems are formulated as mixed-integer nonlinear programming (MINLP) problems with the objective of minimizing task completion delay. We propose a low-complexity maximum value descent (MVD) algorithm to optimally solve these problems. The simulation results show that APCC can reduce the task completion delay by a range of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>20.3</mn><mo>%</mo></mrow></semantics></math></inline-formula> to <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>47.5</mn><mo>%</mo></mrow></semantics></math></inline-formula> when compared to other state-of-the-art benchmarks.
Abstract We investigate the exclusive $$J/\psi $$ J / ψ production at the future Electron-ion collider in China by utilizing the eSTARlight event generator. We model the cross-section and kinematics by fitting to the world data of $$J/\psi $$ J / ψ photoproduction. Projected statistical uncertainties on $$J/\psi $$ J / ψ production are based on the design of a central detector, which consists of a tracker and vertex subsystem. The precision of the pseudo-data allows us to probe the near-threshold mechanism, e.g. the re-scattering effect. The significance of the forward amplitudes is discussed as well. The design and optimization of the detector enhance the potential for exploring the near-threshold region and the realm of high four-momentum transfer squared, which is of particular interest on several physics topics.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Mamta Pandey-Pommier, Arianna Piccialli, Belinda J. Wilkes
et al.
Women in the Astronomy and STEM fields face systemic inequalities throughout their careers. Raising awareness, supported by detailed statistical data, represents the initial step toward closely monitoring hurdles in career progress and addressing underlying barriers to workplace equality. This, in turn, contributes to rectifying gender imbalances in STEM careers. The International Astronomical Union Women in Astronomy (IAU WiA) working group, a part of the IAU Executive Committee, is dedicated to increasing awareness of the status of women in Astronomy and supporting the aspirations of female astronomers globally. Its mission includes taking concrete actions to advance equal opportunities for both women and men in the field of astronomy. In August 2021, the IAU WiA Working Group established a new organizing committee, unveiling a comprehensive four-point plan. This plan aims to strengthen various aspects of the group's mission, encompassing: (i) Awareness Sustainability: Achieved through surveys and data collection, (ii) Training and Skill Building: Focused on professional development, (iii) Fundraising: To support key initiatives, and (iv) Communication: Dissemination of results through conferences, WG Magazines, newsletters, and more. This publication provides an overview of focused surveys that illuminate the factors influencing the careers of women in Astronomy, with a particular focus on the careers of mothers. It highlights the lack of inclusive policies, equal opportunities, and funding support for women researchers in the field. Finally, we summarize the specific initiatives undertaken by the IAU WiA Working Group to advance inclusivity and equal opportunities in Astronomy.
Tata Institute of Fundamental Research (TIFR) has a very long tradition of conducting space astronomy experiments. Within a few years of the discovery of the first non-solar X-ray source in 1962, TIFR leveraged its expertise in balloon technology to make significant contributions to balloon-borne hard X-ray astronomy. This initial enthusiasm led to extremely divergent all-round efforts in space astronomy: balloon-borne X-ray and infrared experiments, rocket and satellite-based X-ray experiments and a host of other new initiatives. In the early eighties, however, TIFR could not keep up with the torrent of results coming from the highly sophisticated satellite experiments from around the world but kept the flag flying by continuing research in a few low-key experiments. These efforts culminated in the landmark project, AstroSat, the first multi-wavelength observatory from India, with TIFR playing a pivotal role in it. In this article, I will present a highly personalised and anecdotal sketch of these exciting developments.
Coded mask instruments have been used in high-energy astronomy for the last forty years now and designs for future hard X-ray/low gamma-ray telescopes are still based on this technique when they need to reach moderate angular resolutions over large field of views, particularly for observations dedicated to the, now flourishing, field of time domain astrophysics. However these systems are somehow unfamiliar to the general astronomers as they actually are two-step imaging devices where the recorded picture is very different from the imaged object and the data processing takes a crucial part in the reconstruction of the sky image. Here we present the concepts of these optical systems applied to high-energy astronomy, the basic reconstruction methods including some useful formulae and the trend of the expected and observed performances as function of the system designs. We review the historical developments and recall the flown space-borne coded mask instruments along with the description of a few relevant examples of major successful implementations and future projects in space astronomy.
Oxygen-free high-conductivity copper (OFHC), chromium-zirconium copper (CuCrZr), and Glidcop<sup>®</sup> AL-15 are widely used in the high heat load absorber elements at the front end of synchrotron radiation facilities. It is necessary to choose the most suitable material according to the actual engineering conditions (such as the specific heat load, material performance, and costs). In the long-term service period, the absorber elements have to bear hundreds or kilowatts of high heat load and its “load-unload” cyclic loading mode. Therefore, the thermal fatigue and thermal creep properties of the materials are critical and have been extensively studied. In this paper, based on the published pieces of the literature, the thermal fatigue theory, experimental principles, methods, test standards, test types of equipment, and key indicators of the thermal fatigue performance of typical copper metal materials used in the front end of synchrotrons radiation Facilities are reviewed, as well as the relevant studies carried out by the well-known synchrotron radiation institutions. In particular, the fatigue failure criteria for these materials and some effective methods for improving the thermal fatigue resistance performance of the high-heat load components are also presented.
Abstract An ideal blackbody absorbs all light impinging on it, and it radiates electromagnetic waves with a broad spectrum that depends only on the temperature. Conversely, a white object is characterized by a finite reflectance to visible light, hence being the opposite of a blackbody. Challenging this concept, here we find that various substances exhibit strong optical absorption capabilities like blackbodies when exposed to intense light, despite appearing pure white in the sunlight. We name this phenomenon photoinduced blackbody effect. Under near infrared light, the photoinduced blackbody effect is accompanied by photon avalanche optical frequency conversion and optical bistable luminescence. Namely, the energy states and absorption properties of the samples are modified under strong laser irradiation. The modified absorption transitions cause the switch of the sample from a quasi-whitebody into a quasi-blackbody via an avalanche mechanism. At the same time, the sample emits a broadband electromagnetic radiation, becoming a bright blackbody.