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Hot Stars, Young Stellar Populations and Dust with Swift/UVOT 热恒星、年轻恒星群和尘埃与 Swift/UVOT
IF 2.9 4区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-16 DOI: 10.3390/universe10080330
Michael H. Siegel, Caryl Gronwall
In this review, we highlight the contributions made by the Swift/UVOT instrument to the understanding of the ultraviolet (UV) attenuation and extinction properties of interstellar dust and provide insight into hot stars and young stellar populations. The study of these two fields is interconnected: UV-bright objects can only be understood if the effects of foreground dust are accounted for, but foreground dust can only be accounted for by studying the properties of UV-bright objects. Decades worth of work have established that the effects of dust on background starlight vary in the ultraviolet, with proposed extinction laws having a wide variety of slopes and a strong “bump” spectroscopic feature at 2175 Å. We show that UVOT is uniquely suited to probe variations in the UV extinction law, specifically because of the uvm2 filter that is centered on the bump and the telescope’s ability to resolve nearby stellar populations. When used in combination with optical and infrared imaging, UVOT can provide strong constraints on variations in the extinction law, both from galaxy to galaxy and within individual galaxies, as well as the properties of young stellar populations. Surveys of UVOT have included the Milky Way, the galaxies of the Local Group, the Local Volume Legacy Survey (LVLS) and two deep fields. All of these are being utilized to provide the most detailed information yet about the UV dust attenuation law and the connection of its variation to underlying physical processes as well as the UV properties of hot stars and young stellar populations.
在这篇综述中,我们将重点介绍 Swift/UVOT 仪器在了解星际尘埃的紫外线(UV)衰减和消光特性方面做出的贡献,并深入探讨热恒星和年轻恒星群。这两个领域的研究是相互关联的:只有考虑到前景尘埃的影响,才能了解紫外亮天体,而只有研究紫外亮天体的特性,才能了解前景尘埃。数十年的研究已经证实,尘埃对紫外背景星光的影响是不同的,提出的消光定律有各种各样的斜率,在 2175 Å 处有一个很强的 "凹凸 "光谱特征。我们的研究表明,UVOT 非常适合探测紫外消光定律的变化,特别是因为它的 uvm2 滤光片以凹凸为中心,而且望远镜能够分辨附近的恒星群。当与光学和红外成像结合使用时,紫外可见光望远镜可以对星系与星系之间以及单个星系内部的消光规律变化以及年轻恒星群的特性提供强有力的约束。对 UVOT 的巡天观测包括银河系、本星系群的星系、本地体积遗产巡天(LVLS)和两个深场。所有这些都被用来提供有关紫外尘埃衰减规律及其变化与基本物理过程的联系以及热恒星和年轻恒星群的紫外特性的最详细的信息。
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引用次数: 0
Weak Deflection Angle by the Einstein–Cartan Traversable Wormhole Using Gauss–Bonnet Theorem with Time Delay 利用高斯-波内特定理和时间延迟计算爱因斯坦-卡尔坦可穿越虫洞的弱偏转角
IF 2.9 4区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-16 DOI: 10.3390/universe10080331
Susmita Sarkar, Nayan Sarkar, Abhisek Dutta, Farook Rahaman
In this article, we estimate the gravitational deflection angles of light in the spacetime of Einstein–Cartan wormholes supported by normal matter or phantom energy utilizing the Gauss–Bonnet theorem. The obtained deflection angles are examined in relation to the wormhole throat radius r0 and the equation of state parameter ω across four scenarios, and it has been seen that the larger throat radii r0 result in higher deflection angles. Moreover, the wormholes filled with phantom energy exhibit greater deflection angles compared to those filled with normal matter. The reported deflection angles are influenced by dark matter and Maxwell’s fish eye matter: Dark matter, as well as Maxwell’s fish eye matter, increases the deflection angles. The deflection angle is also estimated using the Keeton and Petters method, which is proportional to wormhole throat r0 and inversely proportional to the impact parameter b. Additionally, a comparative study is performed on the deflection angles obtained from four different scenarios. Finally, analytical results for time delay due to Einstein–Cartan wormholes are estimated for the four ω cases which are decreasing for increasing values of rc.
在这篇文章中,我们利用高斯-波内定理估算了由正常物质或幽灵能量支撑的爱因斯坦-卡尔坦虫洞时空中光的引力偏转角。研究了四种情况下得到的偏转角与虫洞洞喉半径r0和状态方程参数ω的关系,发现洞喉半径r0越大,偏转角越大。此外,与充满普通物质的虫洞相比,充满幽灵能量的虫洞表现出更大的偏转角。所报告的偏转角受到暗物质和麦克斯韦鱼眼物质的影响:暗物质和麦克斯韦鱼眼物质会增大偏转角。此外,还使用 Keeton 和 Petters 方法估算了偏转角,该方法与虫洞喉管 r0 成正比,与撞击参数 b 成反比。最后,估算了四种 ω 情况下爱因斯坦-卡尔坦虫洞引起的时间延迟的分析结果,这些结果随着 rc 值的增大而减小。
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引用次数: 0
Convolutional Neural Network Processing of Radio Emission for Nuclear Composition Classification of Ultra-High-Energy Cosmic Rays 卷积神经网络处理超高能量宇宙射线核成分分类中的无线电辐射
IF 2.9 4区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-15 DOI: 10.3390/universe10080327
Tudor Alexandru Calafeteanu, Paula Gina Isar, Emil Ioan Sluşanschi
Ultra-high-energy cosmic rays (UHECRs) are extremely rare energetic particles of ordinary matter in the Universe, traveling astronomical distances before reaching the Earth’s atmosphere. When primary cosmic rays interact with atmospheric nuclei, cascading extensive air showers (EASs) of secondary elementary particles are developed. Radio detectors have proven to be a reliable method for reconstructing the properties of EASs, such as the shower’s axis, its energy, and its maximum (Xmax). This aids in understanding fundamental astrophysical phenomena, like active galactic nuclei and gamma-ray bursts. Concurrently, data science has become indispensable in UHECR research. By applying statistical, computational, and deep learning methods to both real-world and simulated radio data, researchers can extract insights and make predictions. We introduce a convolutional neural network (CNN) architecture designed to classify simulated air shower events as either being generated by protons or by iron nuclei. The classification achieved a stable test error of 10%, with Accuracy and F1 scores of 0.9 and an MCC of 0.8. These metrics indicate strong prediction capability for UHECR’s nuclear composition, based on data that can be gathered by detectors at the world’s largest cosmic rays experiment on Earth, the Pierre Auger Observatory, which includes radio antennas, water Cherenkov detectors, and fluorescence telescopes.
超高能宇宙射线(UHECRs)是宇宙中普通物质中极为罕见的高能粒子,在到达地球大气层之前会飞行天文数字的距离。当原生宇宙射线与大气核相互作用时,就会产生次级基本粒子的级联大范围空气阵雨(EAS)。无线电探测器已被证明是重建 EAS 特性的可靠方法,如气雨的轴线、能量和最大值(Xmax)。这有助于理解基本的天体物理现象,如活动星系核和伽玛射线暴。与此同时,数据科学已成为 UHECR 研究中不可或缺的部分。通过将统计、计算和深度学习方法应用于真实世界和模拟无线电数据,研究人员可以提取见解并做出预测。我们介绍了一种卷积神经网络(CNN)架构,旨在将模拟的气雨事件分类为由质子或铁核产生。该分类的测试误差稳定在 10%,准确度和 F1 分数分别为 0.9 和 0.8。这些指标表明,基于皮埃尔-奥格天文台(包括无线电天线、水切伦科夫探测器和荧光望远镜)这一世界上最大的地球宇宙射线实验的探测器所能收集到的数据,对 UHECR 的核组成具有很强的预测能力。
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引用次数: 0
From the Janis–Newman–Winicour Naked Singularities to the Einstein–Maxwell Phantom Wormholes 从杰尼斯-纽曼-维尼库尔裸奇点到爱因斯坦-麦克斯韦尔幽灵虫洞
IF 2.9 4区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-15 DOI: 10.3390/universe10080328
Changjun Gao, Jianhui Qiu
The Janis–Newman–Winicour spacetime corresponds to a static spherically symmetric solution of Einstein equations with the energy momentum tensor of a massless quintessence field. It is understood that the spacetime describes a naked singularity. The solution has two parameters, b and s. To our knowledge, the exact physical meaning of the two parameters is still unclear. In this paper, starting from the Janis–Newman–Winicour naked singularity solution, we first obtain a wormhole solution by a complex transformation. Then, letting the parameter s approach infinity, we obtain the well-known exponential wormhole solution. After that, we embed both the Janis–Newman–Winicour naked singularity and its wormhole counterpart in the background of a de Sitter or anti-de Sitter universe with the energy momentum tensor of massive quintessence and massive phantom fields, respectively. To our surprise, the resulting quintessence potential is actually the dilaton potential found by one of us. It indicates that, by modulating the parameters in the charged dilaton black hole solutions, we can obtain the Janis–Newman–Winicour solution. Furthermore, a charged wormhole solution is obtained by performing a complex transformation on the charged dilaton black hole solutions in the background of a de Sitter or anti-de Sitter universe. We eventually find that s is actually related to the coupling constant of the dilaton field to the Maxwell field and b is related to a negative mass for the dilaton black holes. A negative black hole mass is physically forbidden. Therefore, we conclude that the Janis–Newman–Winicour naked singularity solution is not physically allowed.
杰尼斯-纽曼-维尼库尔时空对应于爱因斯坦方程的静态球对称解,其能量动量张量为无质量五元场。据了解,该时空描述了一个裸奇点。据我们所知,这两个参数的确切物理含义尚不清楚。本文从 Janis-Newman-Winicour 裸奇点解出发,首先通过复变得到虫洞解。然后,让参数 s 接近无穷大,我们得到了著名的指数虫洞解。之后,我们将杰尼斯-纽曼-维尼柯裸奇点及其虫洞对应方案分别嵌入到具有大质量五元场和大质量幻象场的能量动量张量的德西特宇宙或反德西特宇宙背景中。令我们惊讶的是,所得到的五元势实际上就是我们中的一个人发现的稀拉顿势。这表明,通过调节带电稀拉顿黑洞解的参数,我们可以得到杰尼斯-纽曼-维尼库尔解。此外,在德西特或反德西特宇宙背景下,通过对带电稀拉顿黑洞解进行复杂变换,可以得到带电虫洞解。我们最终发现,s 实际上与稀拉顿场与麦克斯韦场的耦合常数有关,而 b 则与稀拉顿黑洞的负质量有关。负的黑洞质量在物理上是被禁止的。因此,我们得出结论:物理上不允许出现杰尼斯-纽曼-维尼库尔裸奇点解。
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引用次数: 0
Multi-Messenger Connection in High-Energy Neutrino Astronomy 高能中微子天文学中的多信使联系
IF 2.9 4区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-13 DOI: 10.3390/universe10080326
Ankur Sharma
Low fluxes of astrophysical neutrinos at TeV energies, and the overwhelming background of atmospheric neutrinos below that, render the current paradigm of neutrino astronomy a severely statistics-limited one. While many hints have emerged, all the evidence gathered by IceCube and ANTARES, over the course of almost a decade and a half of operation, has fallen short of providing any conclusive answer to the puzzle of the origin of high-energy cosmic rays and neutrinos. The advancement of the field is thus closely associated with not only the neutrino observatories coming online in the next few years, but also on the coordinated efforts of the EM, GW and cosmic ray communities to develop dedicated channels and infrastructure that allow for the swift and comprehensive multi-messenger follow-up of relevant events detected in any of these sectors. This paper highlights the strides that have been already taken in that direction and the fruits that they have borne, as well as the challenges that lie ahead.
TeV能量下的天体物理中微子通量很低,而在TeV能量以下的大气中微子背景压倒一切,这使得当前的中微子天文学范式受到了严重的统计限制。虽然已经出现了许多蛛丝马迹,但在冰立方和 ANTARES 近十五年的运行过程中收集到的所有证据都不足以为高能宇宙射线和中微子的起源之谜提供任何确凿的答案。因此,这一领域的进步不仅与未来几年即将上线的中微子天文台密切相关,而且还与电磁、高能宇宙线和宇宙射线界的协调努力密切相关,即开发专用通道和基础设施,以便对在上述任何领域探测到的相关事件进行迅速和全面的多信使跟踪。本文重点介绍在这方面已经取得的进展和成果,以及今后面临的挑战。
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引用次数: 0
Constraint on the Cosmic Curvature in a Model with the Schwarzschild–de Sitter Metric from Supernovae and Gamma-Ray Burst Observational Data 从超新星和伽马射线暴观测数据看施瓦兹希尔德-德-西特公设模型中的宇宙曲率约束
IF 2.9 4区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-11 DOI: 10.3390/universe10080325
Vladimir N. Yershov
In developing his cosmological model of 1917, de Sitter theoretically predicted the phenomenon of cosmological redshift (the de Sitter effect), which he did long before the discovery of this phenomenon in observations. The de Sitter effect is gravitational by its nature, as it is due to differences between the coordinate systems of the observer and the distant source. However, the relationship between the redshift and distance derived from the de Sitter metric is at odds with observations, since this relationship is nonlinear (quadratic) for small redshifts, while the observed relationship between the same quantities is strictly linear. This paper discusses the possibility that cosmological redshift is gravitational by its nature, as in de Sitter’s 1917 model. At the same time, here, as in de Sitter’s model, an elliptical space is used, the main characteristic of which is the identification of its antipodal points. But, unlike de Sitter’s model, here, in order to ensure strict linear dependence of the redshift on distance, the origin of the reference system is transferred to the observer’s antipodal point. The Schwarzschild–de Sitter metric used in this model allows you to estimate the curvature of space from observational data. To achieve this, a theoretical Hubble diagram is built within the framework of the model with the Schwarzschild–de Sitter metric, which is compared with observations from the Pantheon+ catalogue of type Ia supernovae and the Amati catalogue of gamma-ray bursts in the redshift range of 0
在 1917 年建立宇宙学模型时,德-西特从理论上预言了宇宙学红移现象(德-西特效应),这比观测发现这一现象要早得多。德西特效应的本质是引力效应,因为它是由观察者和遥远来源的坐标系之间的差异造成的。然而,根据德西特度量得出的红移和距离之间的关系与观测结果不符,因为对于小红移来说,这种关系是非线性的(二次关系),而观测到的相同数量之间的关系却是严格的线性关系。本文讨论了宇宙学红移本质上是引力红移的可能性,就像在德-西特 1917 模型中一样。同时,与德-西特模型一样,本文也使用了椭圆空间,其主要特征是确定其对跖点。但是,与德西特模型不同的是,为了确保红移与距离的严格线性关系,这里参考系的原点被转移到了观测者的对跖点。该模型中使用的施瓦兹希尔德-德-西特度量可以根据观测数据估算空间曲率。为此,我们在施瓦兹希尔德-德-西特度量模型的框架内建立了一个理论哈勃图,并将其与红移范围为 0
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引用次数: 0
Coupled Quintessence Inspired by Warm Inflation 受暖膨胀启发的耦合昆体
IF 2.9 4区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-10 DOI: 10.3390/universe10080324
Paulo M. Sá
We investigate a coupled quintessence cosmological model in which a dark-energy scalar field with an exponential potential interacts directly with a dark-matter fluid through a dissipative term inspired by warm inflation. The evolution equations of this model give rise to a three-dimensional dynamical system for which a thorough qualitative analysis is performed for all values of the relevant parameters. We find that the model is able to replicate the observed sequence of late-time cosmological eras, namely, a long enough matter-dominated era followed by a present era of accelerated expansion. In situations where there is a significant transfer of energy from dark energy to dark matter, temporary scaling-type solutions may arise, but, asymptotically, all solutions are dominated by dark energy.
我们研究了一个耦合五元宇宙学模型,在这个模型中,具有指数势能的暗能量标量场通过受暖膨胀启发的耗散项与暗物质流体直接相互作用。该模型的演化方程产生了一个三维动力学系统,我们对该系统的所有相关参数值进行了全面的定性分析。我们发现,该模型能够复制观测到的晚期宇宙学时代序列,即一个足够长的物质主导时代,然后是现在的加速膨胀时代。在暗能量向暗物质大量转移的情况下,可能会出现暂时的缩放型解法,但从渐近的角度看,所有的解法都是由暗能量主导的。
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引用次数: 0
CME Forecasting System: Event Selection Algorithm, Dimming Data Application Limitations, and Analysis of the Results for Events of the Solar Cycle 24 集合放射粒子预报系统:太阳周期 24 事件的事件选择算法、调光数据应用限制和结果分析
IF 2.5 4区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-09 DOI: 10.3390/universe10080321
Ksenia Kaportseva, Yulia Shugay, Anna Vakhrusheva, V. Kalegaev, Anton Shiryaev, Valeriy Eremeev
The modeling of coronal mass ejections (CMEs) arrival to Earth was carried out using a one-dimensional drag-based model (DBM) over the period from 2010 to 2018. The CME propagation model includes a simulation of the interaction of the CME with background solar wind via the quasi-stationary solar wind (QSW) model. An analysis of the results of forecasting CME speed and time of arrival to Earth was performed. Input data were obtained from the CACTus database. To ensure real-time operation, a new algorithm was established to select events that can reach Earth more likely. Coronal dimming data were used to obtain coordinates of the CME source location. Forecasting results have been compared with interplanetary CME (ICME) catalogs. The system has predicted 189 of 280 events (68%), with a tolerance of 48 h for the period of maximum solar activity (from 2010 to 2015). The average absolute error of predicted CME arrival speed is about 90 km/s. Our system has predicted 80% of ICMEs associated with extreme geomagnetic storms (Dstmin ≤ −100 nT) within a tolerance of 24 h.
2010年至2018年期间,利用基于一维阻力的模型(DBM)对到达地球的日冕物质抛射(CMEs)进行了建模。日冕物质抛射传播模型包括通过准静止太阳风(QSW)模型模拟日冕物质抛射与背景太阳风的相互作用。对预测 CME 速度和到达地球时间的结果进行了分析。输入数据来自 CACTus 数据库。为确保实时运行,建立了一种新算法,以选择更有可能到达地球的事件。日冕暗淡数据被用来获取 CME 源位置的坐标。预测结果与行星际 CME(ICME)目录进行了比较。该系统预测了 280 个事件中的 189 个(68%),在太阳活动最频繁的时期(2010 年至 2015 年),预测误差为 48 小时。预测的 CME 到达速度的平均绝对误差约为 90 km/s。我们的系统预测了80%与极端地磁暴(Dstmin ≤ -100 nT)相关的集成流体介质事件,误差在24小时之内。
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引用次数: 0
UHECR Clustering: Lightest Nuclei from Local Sheet Galaxies UHECR 星团:来自局部片状星系的最亮星核
IF 2.5 4区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-09 DOI: 10.3390/universe10080323
D. Fargion, P. G. De Sanctis Lucentini, M. Khlopov
The ultra-high-energy cosmic ray (UHECR) puzzle is reviewed under the hints of a few basic results: clustering, anisotropy, asymmetry, bending, and composition changes with energies. We show how the lightest UHECR nuclei from the nearest AGN or Star-Burst sources, located inside a few Mpc Local Sheets, may explain, at best, the observed clustering of Hot Spots at tens EeV energy. Among the possible local extragalactic candidate sources, we derived the main contribution of very few galactic sources. These are located in the Local Sheet plane within a distance of a few Mpc, ejecting UHECR at a few tens of EeV energy. UHECR also shine at lower energies of several EeV, partially feeding the Auger dipole by LMC and possibly a few nearer galactic sources. For the very recent highest energy UHECR event, if a nucleon, it may be explained by a model based on the scattering of UHE ZeV neutrinos on low-mass relic neutrinos. Such scatterings are capable of correlating, via Z boson resonance, the most distant cosmic sources above the GZK bound with such an enigmatic UHECR event. Otherwise, these extreme events, if made by the heaviest composition, could originate from the largest bending trajectory of heaviest nuclei or from nearby sources, even galactic ones. In summary, the present lightest to heavy nuclei model UHECR from the Local Sheet could successfully correlate UHECR clustering with the nearest galaxies and AGN. Heavy UHECR may shine by being widely deflected from the Local Sheet or from past galactic, GRB, or SGR explosive ejection.
超高能宇宙射线(UHECR)之谜是在一些基本结果的提示下被回顾的:聚类、各向异性、不对称、弯曲和成分随能量的变化。我们展示了来自最近的 AGN 或星爆源的最轻 UHECR 核(位于几 Mpc 地方片内)是如何充其量解释在数十 EeV 能量下观测到的热点集群的。在可能的本地银河系外候选源中,我们得出了极少数星系源的主要贡献。这些星系源位于距离本地片平面几 Mpc 的范围内,喷射出几十 EeV 能量的 UHECR。UHECR 也以几 EeV 的较低能量闪耀,部分为 LMC 和可能更近的几个星系源的奥杰偶极子提供能量。对于最近的最高能量 UHECR 事件,如果是一个核子,则可以用一个基于 UHE ZeV 中微子对低质量遗迹中微子的散射的模型来解释。这种散射能够通过 Z 玻色子共振将 GZK 边界以上的最遥远宇宙源与这种神秘的 UHECR 事件联系起来。否则,如果这些极端事件是由最重的成分造成的,那么它们可能来自最重原子核的最大弯曲轨迹或附近的来源,甚至银河系来源。总之,目前来自本地片的从最轻核到最重核的 UHECR 模型可以成功地将 UHECR 聚类与最近的星系和 AGN 联系起来。重UHECR可能会从本片或过去的星系、GRB或SGR爆炸性抛射中广泛偏转而发光。
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引用次数: 0
Strange Dwarfs: A Review on the (in)Stability 奇怪的矮人关于(不)稳定性的评论
IF 2.9 4区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Pub Date : 2024-08-09 DOI: 10.3390/universe10080322
Francesco Di Clemente, Alessandro Drago, Giuseppe Pagliara
White dwarfs are the remnants of stars not massive enough to become supernovae. This review explores the concept of strange dwarfs, a unique class of white dwarfs that contain cores of strange quark matter. Strange dwarfs have different sizes, masses, and evolutionary paths with respect to white dwarfs. They might form through the accumulation of normal matter on strange quark stars or by the capture of strangelets. The stability of strange dwarfs has been debated, with initial studies suggesting stability, while later analyses indicated potential instability. This review revisits these discussions, focusing on the critical role of boundary conditions between nuclear and quark matter in determining stability. It also offers insights into their formation, structure, and possible detection in the universe.
白矮星是质量不足以成为超新星的恒星的残余物。这篇综述探讨了奇异矮星的概念,奇异矮星是一类独特的白矮星,含有奇异夸克物质的核心。与白矮星相比,奇异矮星具有不同的大小、质量和演化路径。它们可能是由奇异夸克星上的正常物质堆积而成,也可能是由奇异子捕获而成。关于奇异矮星的稳定性一直存在争议,最初的研究表明奇异矮星是稳定的,而后来的分析则表明奇异矮星可能是不稳定的。这篇综述重温了这些讨论,重点关注核物质和夸克物质之间的边界条件在决定稳定性方面的关键作用。它还对它们的形成、结构以及在宇宙中的可能探测提供了见解。
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引用次数: 0
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Universe
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