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Location Problem in Relativistic Positioning: Relative Formulation 相对论定位中的位置问题：相对公式
IF 2.5 4区 物理与天体物理
Universe Pub Date : 2024-07-17 DOI: 10.3390/universe10070299
Ramón Serrano Montesinos, J. J. Ferrando, J. A. Morales-Lladosa
{"title":"Location Problem in Relativistic Positioning: Relative Formulation","authors":"Ramón Serrano Montesinos, J. J. Ferrando, J. A. Morales-Lladosa","doi":"10.3390/universe10070299","DOIUrl":"https://doi.org/10.3390/universe10070299","url":null,"abstract":"A relativistic positioning system is a set of four emitters broadcasting their proper times by means of light signals. The four emitter times received at an event constitute the emission coordinates of the event. The covariant quantities associated with relativistic positioning systems are analysed relative to an observer in Minkowski space-time by splitting them in their relative space-like and time-like components. The location of a user in inertial coordinates from a standard set of emission data (emitted times and satellite trajectories) is solved in the underlying 3+1 formalism. The analytical location solution obtained by Kleusberg for the GPS system is recovered and interpreted in a Minkowskian context.","PeriodicalId":48646,"journal":{"name":"Universe","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141830052","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Study of Wide-Field-of-View X-ray Observations of the Virgo Cluster Using the Lobster Eye Imager for Astronomy 利用龙虾眼天文成像仪对室女座星团进行宽视场 X 射线观测的研究
IF 2.9 4区 物理与天体物理
Universe Pub Date : 2024-07-17 DOI: 10.3390/universe10070300
Wen-Cheng Feng, Shu-Mei Jia, Hai-Hui Zhao, Heng Yu, Hai-Wu Pan, Cheng-Kui Li, Yu-Lin Cheng, Shan-Shan Weng, Yong Chen, Yuan Liu, Zhi-Xing Ling, Chen Zhang
{"title":"Study of Wide-Field-of-View X-ray Observations of the Virgo Cluster Using the Lobster Eye Imager for Astronomy","authors":"Wen-Cheng Feng, Shu-Mei Jia, Hai-Hui Zhao, Heng Yu, Hai-Wu Pan, Cheng-Kui Li, Yu-Lin Cheng, Shan-Shan Weng, Yong Chen, Yuan Liu, Zhi-Xing Ling, Chen Zhang","doi":"10.3390/universe10070300","DOIUrl":"https://doi.org/10.3390/universe10070300","url":null,"abstract":"The Lobster Eye Imager for Astronomy (LEIA) is the pathfinder of the wide-field X-ray telescope used in the Einstein Probe mission. In this study, we present an image of the Virgo Cluster taken by LEIA in the 0.5–4.5 keV band with an exposure time of ∼17.3 ks in the central region. This extended emission is generally consistent with the results obtained by ROSAT. However, the field is affected by bright point sources due to the instrument’s Point Spread Function (PSF) effect. Through fitting of the LEIA spectrum of the Virgo Cluster, we obtained a temperature of 2.1−0.1+0.3 keV, which is consistent with the XMM-Newton results (∼2.3 keV). Above 1.6 keV, the spectrum is dominated by the X-ray background. In summary, this study validates LEIA’s extended source imaging and spectral resolution capabilities for the first time.","PeriodicalId":48646,"journal":{"name":"Universe","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141721386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Screened Scalar Fields in the Laboratory and the Solar System 实验室和太阳系中的筛选标量场
IF 2.9 4区 物理与天体物理
Universe Pub Date : 2024-07-15 DOI: 10.3390/universe10070297
Hauke Fischer, Christian Käding, Mario Pitschmann
{"title":"Screened Scalar Fields in the Laboratory and the Solar System","authors":"Hauke Fischer, Christian Käding, Mario Pitschmann","doi":"10.3390/universe10070297","DOIUrl":"https://doi.org/10.3390/universe10070297","url":null,"abstract":"The last few decades have provided abundant evidence for physics beyond the two standard models of particle physics and cosmology. As is now known, the by far largest part of our universe’s matter/energy content lies in the ‘dark’, and consists of dark energy and dark matter. Despite intensive efforts on the experimental as well as the theoretical side, the origins of both are still completely unknown. Screened scalar fields have been hypothesized as potential candidates for dark energy or dark matter. Among these, some of the most prominent models are the chameleon, symmetron, and environment-dependent dilaton. In this article, we present a summary containing the most recent experimental constraints on the parameters of these three models. For this, experimental results have been employed from the qBounce collaboration, neutron interferometry, and Lunar Laser Ranging (LLR), among others. In addition, constraints are forecast for the Casimir and Non-Newtonian force Experiment (Cannex). Combining these results with previous ones, this article collects the most up-to-date constraints on the three considered screened scalar field models.","PeriodicalId":48646,"journal":{"name":"Universe","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141721399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Soft X-ray Spectrum Changes over the 35-Day Cycle in Hercules X-1 Observed with AstroSat SXT 用 AstroSat SXT 卫星观测到的海格力斯 X-1 在 35 天周期内的软 X 射线光谱变化
IF 2.5 4区 物理与天体物理
Universe Pub Date : 2024-07-15 DOI: 10.3390/universe10070298
Denis Leahy , Riddhiman Sharma 
{"title":"Soft X-ray Spectrum Changes over the 35-Day Cycle in Hercules X-1 Observed with AstroSat SXT","authors":"Denis Leahy , Riddhiman Sharma ","doi":"10.3390/universe10070298","DOIUrl":"https://doi.org/10.3390/universe10070298","url":null,"abstract":"Observations of the X-ray binary system Her X-1 by the AstroSat Soft X-ray Telescope (SXT) were carried out in 2020 through 2023 with the goals of measuring X-ray spectrum changes with the 35-day disk precession phase and measuring eclipses at different 35-day phases. Her X-1 exhibits a regular flux modulation with a period of ≃35 days with different intensity levels at various 35-day phases (called “states”). The four multi-day long observations were scheduled to cover most of these states. Each 35-day phase was determined using monitoring observations with the Swift Burst Alert Telescope (BAT). Nine eclipses were observed in the range of 35-day phases, with at least one eclipse during each observation. Data with dips were separated from data without dips. The variation in X-ray spectral parameters vs. 35-day phase shows the following: eclipse parameters are nearly constant, showing that the scattering corona does not change with 35-day phase; dips show an increase in covering fraction but not column density compared to non-dip data; the1 keV line normalization behaves similarly to the powerlaw normalization, consistent with an origin near the powerlaw emission region, likely the magnetospheric accretion flow from the inner disk onto the neutron star; and the blackbody normalization (area) is large (∼3×105 km2) during the Main High and Short High states, consistent with the inner edge of the accretion disk.","PeriodicalId":48646,"journal":{"name":"Universe","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141648313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Thermodynamics of Magnetic Black Holes with Nonlinear Electrodynamics in Extended Phase Space 扩展相空间中具有非线性电动力学的磁性黑洞热力学
IF 2.9 4区 物理与天体物理
Universe Pub Date : 2024-07-13 DOI: 10.3390/universe10070295
Sergey Il’ich Kruglov
{"title":"Thermodynamics of Magnetic Black Holes with Nonlinear Electrodynamics in Extended Phase Space","authors":"Sergey Il’ich Kruglov","doi":"10.3390/universe10070295","DOIUrl":"https://doi.org/10.3390/universe10070295","url":null,"abstract":"We study Einstein’s gravity in AdS space coupled to nonlinear electrodynamics. Thermodynamics in extended phase space of magnetically charged black holes is investigated. We compute the metric and mass functions and their asymptotics, showing that black holes may have one or two horizons. The metric function is regular, f(0)=1, and corrections to the Reissner–Nordström solution are in the order of O(r−3) when the Schwarzschild mass is zero. We prove that the first law of black hole thermodynamics and the generalized Smarr relation hold. The magnetic potential and vacuum polarization conjugated to coupling are computed and depicted. We calculate the Gibbs free energy and the heat capacity showing that first-order and second-order phase transitions take place.","PeriodicalId":48646,"journal":{"name":"Universe","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141608979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
On the Choice of Variable for Quantization of Conformal GR 关于共形 GR 量子化变量的选择
IF 2.9 4区 物理与天体物理
Universe Pub Date : 2024-07-13 DOI: 10.3390/universe10070294
A. B. Arbuzov, A. A. Nikitenko
{"title":"On the Choice of Variable for Quantization of Conformal GR","authors":"A. B. Arbuzov, A. A. Nikitenko","doi":"10.3390/universe10070294","DOIUrl":"https://doi.org/10.3390/universe10070294","url":null,"abstract":"The possibility of using spin connection components as basic quantization variables of a conformal version of general relativity is studied. The considered model contains gravitational degrees of freedom and a scalar dilaton field. The standard tetrad formalism is applied. Properties of spin connections in this model are analyzed. Secondary quantization of the chosen variables is performed. The gravitational part of the model action turns out to be quadratic with respect to the spin connections. So at the quantum level, the model looks trivial, i.e., without quantum self-interactions. Meanwhile the correspondence to general relativity is preserved at the classical level.","PeriodicalId":48646,"journal":{"name":"Universe","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141608981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Lorentzian Quantum Cosmology from Effective Spin Foams 从有效自旋泡沫看洛伦兹量子宇宙学
IF 2.9 4区 物理与天体物理
Universe Pub Date : 2024-07-13 DOI: 10.3390/universe10070296
Bianca Dittrich, José Padua-Argüelles
{"title":"Lorentzian Quantum Cosmology from Effective Spin Foams","authors":"Bianca Dittrich, José Padua-Argüelles","doi":"10.3390/universe10070296","DOIUrl":"https://doi.org/10.3390/universe10070296","url":null,"abstract":"Effective spin foams provide the most computationally efficient spin foam models yet and are therefore ideally suited for applications, e.g., to quantum cosmology. Here, we provide the first effective spin foam computations of a finite time evolution step in a Lorentzian quantum de Sitter universe. We will consider a setup that computes the no-boundary wave function and a setup describing the transition between two finite scale factors. A key property of spin foams is that they implement discrete spectra for the areas. We therefore study the effects that are induced by the discrete spectra. To perform these computations, we had to identify a technique to deal with highly oscillating and slowly converging or even diverging sums. Here, we illustrate that high-order Shanks transformation works very well and is a promising tool for the evaluation of Lorentzian (gravitational) path integrals and spin foam sums.","PeriodicalId":48646,"journal":{"name":"Universe","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141608980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Isospin QCD as a Laboratory for Dense QCD 作为高密度 QCD 实验室的等空间 QCD
IF 2.9 4区 物理与天体物理
Universe Pub Date : 2024-07-12 DOI: 10.3390/universe10070293
Toru Kojo, Daiki Suenaga, Ryuji Chiba
{"title":"Isospin QCD as a Laboratory for Dense QCD","authors":"Toru Kojo, Daiki Suenaga, Ryuji Chiba","doi":"10.3390/universe10070293","DOIUrl":"https://doi.org/10.3390/universe10070293","url":null,"abstract":"QCD with the isospin chemical potential μI is a useful laboratory to delineate the microphysics in dense QCD. To study the quark–hadron continuity, we use a quark–meson model that interpolates hadronic and quark matter physics at microscopic level. The equation of state is dominated by mesons at low density but taken over by quarks at high density. We extend our previous studies with two flavors to the three-flavor case to study the impact of the strangeness, which may be brought by kaons (K+,K0)=(us¯,sd¯) and the UA(1) anomaly. In the normal phase, the excitation energies of kaons are reduced by μI in the same way as hyperons in nuclear matter at the finite baryon chemical potential. Once pions condense, kaon excitation energies increase as μI does. Moreover, strange quarks become more massive through the UA(1) coupling to the condensed pions. Hence, at zero and low temperature, the strange hadrons and quarks are highly suppressed. The previous findings in two-flavor models, sound speed peak, negative trace anomaly, gaps insensitive to μI, persist in our three-flavor model and remain consistent with the lattice results to μI∼ 1 GeV. We discuss the non-perturbative power corrections and quark saturation effects as important ingredients to understand the crossover equations of state measured on the lattice.","PeriodicalId":48646,"journal":{"name":"Universe","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141608982","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Stochastic Tunneling in de Sitter Spacetime 德西特时空中的随机隧道效应
IF 2.9 4区 物理与天体物理
Universe Pub Date : 2024-07-11 DOI: 10.3390/universe10070292
Taiga Miyachi, Jiro Soda, Junsei Tokuda
{"title":"Stochastic Tunneling in de Sitter Spacetime","authors":"Taiga Miyachi, Jiro Soda, Junsei Tokuda","doi":"10.3390/universe10070292","DOIUrl":"https://doi.org/10.3390/universe10070292","url":null,"abstract":"Tunneling processes in de Sitter spacetime are studied by using the stochastic approach. We evaluate the Martin–Siggia–Rose–Janssen–de Dominicis (MSRJD) functional integral by using the saddle-point approximation to obtain the tunneling rate. The applicability conditions of this method are clarified using the Schwinger–Keldysh formalism. In the case of a shallow potential barrier, we reproduce the Hawking–Moss (HM) tunneling rate. Remarkably, in contrast to the HM picture, the configuration derived from the MSRJD functional integral satisfies physically natural boundary conditions. We also discuss the case of a steep potential barrier and find an interesting Coleman–de Luccia (CDL) bubblelike configuration. Since the starting point of our analysis is the Schwinger–Keldysh path integral, which can be formulated in a more generic setup and incorporates quantum effects, our formalism sheds light on further studies of tunneling phenomena from a real-time perspective.","PeriodicalId":48646,"journal":{"name":"Universe","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141586208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Wormhole Restrictions from Quantum Energy Inequalities 从量子能量不等式看虫洞限制
IF 2.9 4区 物理与天体物理
Universe Pub Date : 2024-07-06 DOI: 10.3390/universe10070291
Eleni-Alexandra Kontou
{"title":"Wormhole Restrictions from Quantum Energy Inequalities","authors":"Eleni-Alexandra Kontou","doi":"10.3390/universe10070291","DOIUrl":"https://doi.org/10.3390/universe10070291","url":null,"abstract":"Wormhole solutions, bridges that connect different parts of spacetime, were proposed early in the history of General Relativity. Soon after, it was shown that all wormholes violate classical energy conditions, which are non-negativity constraints on contractions of the stress–energy tensor. Since these conditions are violated by quantum fields, it was believed that wormholes can be constructed in the context of semiclassical gravity. But negative energies in quantum field theory are not without restriction: quantum energy inequalities (QEIs) control renormalized negative energies averaged over a geodesic. Thus, QEIs provide restrictions on the construction of wormholes. This work is a review of the relevant literature, thus focusing on results where QEIs restrict traversable wormholes. Both ‘short’ and ‘long’ (without causality violations) wormhole solutions in the context of semiclassical gravity are examined. A new result is presented on constraints on the Maldacena, Milekhin, and Popov ‘long’ wormhole from the recently derived doubled smeared null energy condition.","PeriodicalId":48646,"journal":{"name":"Universe","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141566973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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