Universe最新文献_第3页

Combined Studies Approach to Rule Out Cosmological Models Which Are Based on Nonlinear Electrodynamics 排除基于非线性电动力学的宇宙学模型的综合研究方法

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-09-04 DOI: 10.3390/universe10090353

Ricardo García-Salcedo, Isidro Gómez-Vargas, Tame González, Vicent Martinez-Badenes, Israel Quiros

{"title":"Combined Studies Approach to Rule Out Cosmological Models Which Are Based on Nonlinear Electrodynamics","authors":"Ricardo García-Salcedo, Isidro Gómez-Vargas, Tame González, Vicent Martinez-Badenes, Israel Quiros","doi":"10.3390/universe10090353","DOIUrl":"https://doi.org/10.3390/universe10090353","url":null,"abstract":"We apply a combined study in order to investigate the dynamics of cosmological models incorporating nonlinear electrodynamics (NLED). The study is based on the simultaneous investigation of such fundamental aspects as stability and causality, complemented with a dynamical systems investigation of the involved models, as well as Bayesian inference for parameter estimation. We explore two specific NLED models: the power-law and the rational Lagrangian. We present the theoretical framework of NLED coupled with general relativity, followed by an analysis of the stability and causality of the various NLED Lagrangians. We then perform a detailed dynamical analysis to identify the ranges where these models are stable and causal. Our results show that the power-law Lagrangian model transitions through various cosmological phases, evolving from a Maxwell radiation-dominated state to a matter-dominated state. For the rational Lagrangian model, including the Maxwell term, stable and causal behavior is observed within specific parameter ranges, with critical points indicating the evolutionary pathways of the universe. To validate our theoretical findings, we perform Bayesian parameter estimation using a comprehensive set of observational data, including cosmic chronometers, baryon acoustic oscillation (BAO) measurements, and supernovae type Ia (SNeIa). The estimated parameters for both models align with the expected values for the current universe, particularly the matter density Ωm and the Hubble parameter h. However, the parameters of the models are not tightly constrained within the prior ranges. Our combined studies approach rules out the mentioned models as an appropriate description of the cosmos. Our results highlight the need for further refinement and exploration of NLED-based cosmological models to fully integrate them into the standard cosmological framework.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"13 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210898","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

Different Aspects of Entropic Cosmology 熵宇宙学的不同方面

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-09-03 DOI: 10.3390/universe10090352

Shin’ichi Nojiri, Sergei D. Odintsov, Tanmoy Paul

{"title":"Different Aspects of Entropic Cosmology","authors":"Shin’ichi Nojiri, Sergei D. Odintsov, Tanmoy Paul","doi":"10.3390/universe10090352","DOIUrl":"https://doi.org/10.3390/universe10090352","url":null,"abstract":"We provide a short review of the recent developments in entropic cosmology based on two thermodynamic laws of the apparent horizon, namely the first and the second laws of thermodynamics. The first law essentially provides the change in entropy of the apparent horizon during the cosmic evolution of the universe; in particular, it is expressed by TdS=−d(ρV)+WdV (where W is the work density and other quantities have their usual meanings). In this way, the first law actually links various theories of gravity with the entropy of the apparent horizon. This leads to a natural question—“What is the form of the horizon entropy corresponding to a general modified theory of gravity?”. The second law of horizon thermodynamics states that the change in total entropy (the sum of horizon entropy + matter fields’ entropy) with respect to cosmic time must be positive, where the matter fields behave like an open system characterised by a non-zero chemical potential. The second law of horizon thermodynamics importantly provides model-independent constraints on entropic parameters. Finally, we discuss the standpoint of entropic cosmology on inflation (or bounce), reheating and primordial gravitational waves from the perspective of a generalised entropy function.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"19 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210908","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 Classical Limit of Freely Falling Quantum Particles, Quantum Corrections and the Emergence of the Equivalence Principle 论自由落体量子粒子的经典极限、量子修正和等效原理的出现

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-09-02 DOI: 10.3390/universe10090351

Juan A. Cañas, J. Bernal, A. Martín-Ruiz

引用次数: 0

About Jordan and Einstein Frames: A Study in Inflationary Magnetogenesis 关于约旦和爱因斯坦框架：胀磁发生研究

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-09-01 DOI: 10.3390/universe10090350

Joel Velásquez, Héctor J. Hortua, Leonardo Castañeda

引用次数: 0

Characterisation of the Atmosphere in Very High Energy Gamma-Astronomy for Imaging Atmospheric Cherenkov Telescopes 用于大气切伦科夫望远镜成像的甚高能伽马天文学中的大气特征描述

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-08-30 DOI: 10.3390/universe10090349

Dijana Dominis Prester, Jan Ebr, Markus Gaug, Alexander Hahn, Ana Babić, Jiří Eliášek, Petr Janeček, Sergey Karpov, Marta Kolarek, Marina Manganaro, Razmik Mirzoyan

{"title":"Characterisation of the Atmosphere in Very High Energy Gamma-Astronomy for Imaging Atmospheric Cherenkov Telescopes","authors":"Dijana Dominis Prester, Jan Ebr, Markus Gaug, Alexander Hahn, Ana Babić, Jiří Eliášek, Petr Janeček, Sergey Karpov, Marta Kolarek, Marina Manganaro, Razmik Mirzoyan","doi":"10.3390/universe10090349","DOIUrl":"https://doi.org/10.3390/universe10090349","url":null,"abstract":"Ground-based observations of Very High Energy (VHE) gamma rays from extreme astrophysical sources are significantly influenced by atmospheric conditions. This is due to the atmosphere being an integral part of the detector when utilizing Imaging Atmospheric Cherenkov Telescopes (IACTs). Clouds and dust particles diminish atmospheric transmission of Cherenkov light, thereby impacting the reconstruction of the air showers and consequently the reconstructed gamma-ray spectra. Precise measurements of atmospheric transmission above Cherenkov observatories play a pivotal role in the accuracy of the analysed data, among which the corrections of the reconstructed energies and fluxes of incoming gamma rays, and in establishing observation strategies for different types of gamma-ray emitting sources. The Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes and the Cherenkov Telescope Array Observatory (CTAO), both located on the Observatorio del Roque de los Muchachos (ORM), La Palma, Canary Islands, use different sets of auxiliary instruments for real-time characterisation of the atmosphere. In this paper, historical data taken by MAGIC LIDAR (LIght Detection And Ranging) and CTAO FRAM (F/Photometric Robotic Telescope) are presented. From the atmospheric aerosol transmission profiles measured by the MAGIC LIDAR and CTAO FRAM aerosol optical depth maps, we obtain the characterisation of the clouds above the ORM at La Palma needed for data correction and optimal observation scheduling.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"268 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210932","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

Infrared Regularization of Very Special Relativity Models 非常狭义相对论模型的红外正则化

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-08-29 DOI: 10.3390/universe10090348

Jorge Alfaro

引用次数: 0

Strange and Odd Morphology Extragalactic Radio Sources (STROMERSs): A Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) Look at the Strange and Odd Radio Sources 银河系外奇异形貌射电源（STROMERSs）：二十厘米射电天空的微弱图像（FIRST）--奇异射电源的观察

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-08-28 DOI: 10.3390/universe10090347

Soumen Kumar Bera, Tapan K. Sasmal, Soumen Mondal, Taotao Fang, Xuelei Chen

{"title":"Strange and Odd Morphology Extragalactic Radio Sources (STROMERSs): A Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) Look at the Strange and Odd Radio Sources","authors":"Soumen Kumar Bera, Tapan K. Sasmal, Soumen Mondal, Taotao Fang, Xuelei Chen","doi":"10.3390/universe10090347","DOIUrl":"https://doi.org/10.3390/universe10090347","url":null,"abstract":"We report the identification of an extremely rare and peculiar set of irregular radio sources, termed “STROMERSs” (STRange and Odd Morphology Extragalactic Radio Sources).ingThe irregular radio sources with very anomalous morphologies that make them exceptionally different from all the known classes and subclasses of irregular radio sources are detected as STROMERSs. A thorough search for this class of sources from the Very Large Array (VLA) Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) gave a total of nine such candidates. We checked the corresponding morphology of the identified sources in other frequency surveys. We found a detectable radio emission for all of the nine sources in the NRAO VLA Sky Survey (NVSS) at 1.4 GHz and in the TIFR GMRT Sky Survey (TGSS) at 150 MHz, while the same was found for only three sources in the Westerbork Northern Sky Survey (WENSS) at 625 MHz. However, the strange morphology was not found in all of those other survey images. We also characterized the sources with their corresponding physical parameters like optical counterpart, size, spectral index, and radio luminosity. ingThe estimated spectral values of the sources indicated that the STROMERSs were most likely radio galaxies. The presence of any nearby galaxy clusters for the STROMERSs was also checked.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"4 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227830","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

First Results of the CREDO-Maze Cosmic Ray Project CREDO-Maze 宇宙射线项目的首批成果

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-08-28 DOI: 10.3390/universe10090346

Tadeusz Wibig, Michał Karbowiak, Punsiri Dam-O, Karol Jȩdrzejczak, Jari Joutsenvaara, Julia Puputti, Juha Sorri, Ari-Pekka Leppänen

引用次数: 0

On Quark–Lepton Mixing and the Leptonic CP Violation 关于夸克-质子混合和质子 CP Violation

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-08-28 DOI: 10.3390/universe10090345

Alessio Giarnetti, Simone Marciano, Davide Meloni

引用次数: 0

The Intrinsic Correlations between Prompt Emission and X-ray Flares of Gamma-Ray Bursts 伽马射线暴的瞬时发射与 X 射线耀斑之间的内在相关性

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-08-27 DOI: 10.3390/universe10090343

Xing-Ting Zhong, Si-Yuan Zhu, Li-Ming Zhuo, Zeng Zhang, Fu-Wen Zhang

{"title":"The Intrinsic Correlations between Prompt Emission and X-ray Flares of Gamma-Ray Bursts","authors":"Xing-Ting Zhong, Si-Yuan Zhu, Li-Ming Zhuo, Zeng Zhang, Fu-Wen Zhang","doi":"10.3390/universe10090343","DOIUrl":"https://doi.org/10.3390/universe10090343","url":null,"abstract":"X-ray flare (XRF) is a common phenomenon in the X-ray afterglow of gamma-ray bursts (GRBs). Although it is commonly believed that XRFs may share a common origin with prompt emission, i.e., the “internal” origin, the origin of XRFs is still unknown. In this work, we compile a GRB sample containing 31 GRBs with a single XRF, a well-measured spectrum, and a redshift, and investigate the intrinsic properties and correlations between prompt emission and the XRFs of these events. We find that the distributions of main physical parameters of prompt emission and XRFs are basically log-normal. The median value of the rise time is shorter than the decay time for all flares, with a ratio of about 1:2, which is similar to the fast rise and exponential decay structure of prompt emission pulses. We also find that the prompt emission energy (Eiso) and peak luminosity (Liso) have tight correlations with XRF energy (EX,iso) and peak luminosity (LX,p), Eiso∝EX,iso0.74 (LX,p0.62) and Liso∝EX,iso0.85 (LX,p0.68). However, the durations of prompt emissions are independent of the temporal properties of XRFs. Furthermore, we also analyze the three-parameter correlations between prompt emissions and XRFs, and find that there are tight correlations among the XRF peak time (Tp,z), LX,p, and Eiso/Liso, LX,p∝Tp,z−1.08Eiso0.84 and LX,p∝Tp,z−1.09Liso0.71. Interestingly, these results are very similar to the properties of an X-ray plateau in GRBs, which indicates that X-ray flares and plateaus may have the same physical origin, and strongly supports that the two emission components originate from the late-time activity of the central engine.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"4 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227845","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