Universe最新文献

{"title":"Low-Energy Cosmic Rays and Associated MeV Gamma-Ray Emissions in the Protoplanetary System","authors":"Xulei Sun, Shuying Zheng, Zhaodong Shi, Bing Liu, Ruizhi Yang","doi":"10.3390/universe10080310","DOIUrl":"https://doi.org/10.3390/universe10080310","url":null,"abstract":"Low-energy cosmic rays (LECRs) play a crucial role in the formation of planetary systems, and detecting and reconstructing the properties of early LECRs is essential for understanding the mechanisms of planetary system formation. Given that LECRs interact with the surrounding medium to produce nuclear de-excitation line emissions, which are gamma-ray emissions with energy mainly within 0.1–10 MeV and are unaffected by stellar wind modulation, these emissions can accurately reflect the properties of LECRs. This study introduces an innovative method for using gamma-ray emissions to infer LECR properties. We employed the Parker transport equation to simulate the propagation and spectral evolution of LECRs in a protoplanetary disk and calculated the characteristic gamma-ray emissions resulting from interactions between LECRs and disk material. These gamma-ray emissions encapsulate the spectral information of LECRs, providing a powerful tool to reconstruct the cosmic ray environment at that time. This method, supported by further theoretical developments and observations, will fundamentally enhance our understanding of the impact of CRs on the origin and evolution of planetary systems and address significant scientific questions regarding the cosmic ray environment at the origin of life.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"26 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141771221","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}

{"title":"Construction of Ground-State Solutions of the Gross–Pitaevskii–Poisson System Using Genetic Algorithms","authors":"Carlos Tena-Contreras, Iván Alvarez-Ríos, Francisco S. Guzmán","doi":"10.3390/universe10080309","DOIUrl":"https://doi.org/10.3390/universe10080309","url":null,"abstract":"We present the construction of the ground state of the Gross–Pitaevskii–Poisson equations using genetic algorithms. By employing numerical solutions, we develop an empirical formula for the density that works within the considered parameter space. Through the analysis of both numerical and empirical solutions, we investigate the stability of these ground-state solutions. Our findings reveal that while the numerical solution outperforms the empirical formula, both solutions lead to similar oscillation modes. We observe that the stability of the solutions depends on specific values of the central density and the nonlinear self-interaction term and establish an empirical criterion delineating the conditions under which the solutions exhibit stability or instability.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"16 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141771223","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}

{"title":"Measurements of Decoherence in Small Sea-Level Extensive Air Showers","authors":"Roger Clay","doi":"10.3390/universe10080308","DOIUrl":"https://doi.org/10.3390/universe10080308","url":null,"abstract":"A study is made of the progressive ‘decoherence’ of cosmic ray extensive air-shower particle-detector signals in small air showers through measurements of coincidence rates for pairs of detectors versus the detector separation. Measurements are made both when only the two separated detectors themselves trigger in coincidence, and when that coincidence trigger also requires the detection of a local air shower by a small external air-shower array. The addition of the explicit air-shower trigger ensures that the latter data correspond to showers of a larger particle size, and triggering by very localised shower cores is then unlikely. When including a shower trigger, the decoherence results appear substantially different in form. The coincidence rate between two detectors only can be approximated by a power-law variation with separation distance. When triggering involves an air-shower array, the variation becomes close to an exponential form with characteristic exponent distances varying systematically with increasing detector and air-shower size thresholds. A result is that one can see that small air showers will exhibit clear non-Poissonian density fluctuations near their cores, out to distances of ~5 m, or at shower energies below ~0.05 PeV. These ideas can be helpful in understanding the statistical properties of signals when using large detectors in air-shower arrays.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"60 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141771222","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}

{"title":"A Study of Spin 1 Unruh–De Witt Detectors","authors":"F. M. Guedes, M. S. Guimaraes, I. Roditi, S. P. Sorella","doi":"10.3390/universe10080307","DOIUrl":"https://doi.org/10.3390/universe10080307","url":null,"abstract":"A study of the interaction of spin 1 Unruh–De Witt detectors with a relativistic scalar quantum field is presented here. After tracing out the field modes, the resulting density matrix for a bipartite qutrit system is employed to investigate the violation of the Bell–CHSH inequality. Unlike the case of spin 1/2, for which the effects of the quantum field result in a decrease in the size of violation, in the case of spin 1, both a decrease or an increase in the size of the violation may occur. This effect is ascribed to the fact that Tsirelson’s bound is not saturated in the case of qutrits.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"10 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141771225","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}

{"title":"Graviton Physics: A Concise Tutorial on the Quantum Field Theory of Gravitons, Graviton Noise, and Gravitational Decoherence","authors":"Jen-Tsung Hsiang, Hing-Tong Cho, Bei-Lok Hu","doi":"10.3390/universe10080306","DOIUrl":"https://doi.org/10.3390/universe10080306","url":null,"abstract":"The detection of gravitational waves in 2015 ushered in a new era of gravitational wave (GW) astronomy capable of probing the strong field dynamics of black holes and neutron stars. It has opened up an exciting new window for laboratory and space tests of Einstein’s theory of classical general relativity (GR). In recent years, two interesting proposals have aimed to reveal the quantum nature of perturbative gravity: (1) theoretical predictions on how graviton noise from the early universe, after the vacuum of the gravitational field was strongly squeezed by inflationary expansion; (2) experimental proposals using the quantum entanglement between two masses, each in a superposition (gravitational cat, or gravcat) state. The first proposal focuses on the stochastic properties of quantum fields (QFs), and the second invokes a key concept of quantum information (QI). An equally basic and interesting idea is to ask whether (and how) gravity might be responsible for a quantum system becoming classical in appearance, known as gravitational decoherence. Decoherence due to gravity is of special interest because gravity is universal, meaning, gravitational interaction is present for all massive objects. This is an important issue in macroscopic quantum phenomena (MQP), underlining many proposals in alternative quantum theories (AQTs). To fully appreciate or conduct research in these exciting developments requires a working knowledge of classical GR, QF theory, and QI, plus some familiarity with stochastic processes (SPs), namely, noise in quantum fields and decohering environments. Traditionally a new researcher may be conversant in one or two of these four subjects: GR, QFT, QI, and SP, depending on his/her background. This tutorial attempts to provide the necessary connective tissues between them, helping an engaged reader from any one of these four subjects to leapfrog to the frontier of these interdisciplinary research topics. In the present version, we shall address the three topics listed in the title, excluding gravitational entanglement, because, despite the high attention some recent experimental proposals have received, its nature and implications in relation to quantum gravity still contain many controversial elements.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"31 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141771224","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}

{"title":"ΛCDM Tensions: Localising Missing Physics through Consistency Checks","authors":"Özgür Akarsu, Eoin Ó Colgáin, Anjan A. Sen, M. M. Sheikh-Jabbari","doi":"10.3390/universe10080305","DOIUrl":"https://doi.org/10.3390/universe10080305","url":null,"abstract":"ΛCDM tensions are by definition model-dependent; one sees anomalies through the prism of ΛCDM. Thus, progress towards tension resolution necessitates checking the consistency of the ΛCDM model to localise missing physics either in redshift or scale. Since the universe is dynamical and redshift is a proxy for time, it is imperative to first perform consistency checks involving redshift, then consistency checks involving scale as the next steps to settle the “systematics versus new physics” debate and foster informed model building. We present a review of the hierarchy of assumptions underlying the ΛCDM cosmological model and comment on whether relaxing them can address the tensions. We focus on the lowest lying fruit of identifying missing physics through the identification of redshift-dependent ΛCDM model fitting parameters. We highlight the recent progress made on S8:=σ8Ωm/0.3 tension and elucidate how similar progress can be made on H0 tension. Our discussions indicate that H0 tension, equivalently a redshift-dependent H0, and a redshift-dependent S8 imply a problem with the background ΛCDM cosmology.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"67 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141771350","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}

{"title":"Dissipative Kinematics in Binary Neutron Star Mergers","authors":"Sreemoyee Sarkar, Souvik Priyam Adhya","doi":"10.3390/universe10070303","DOIUrl":"https://doi.org/10.3390/universe10070303","url":null,"abstract":"We highlight the recent progress in the calculation of transport coefficients pertinent to binary neutron star mergers. Specifically, we analyze the bulk viscosity coefficient driven by both the DURCA and MURCA processes and electron transport coefficients in dense and hot plasma relevant to the merger scenario. The study considers high temperatures (T>6×1010 K) and dense environments (nB∼n0−3n0). Bulk viscosity exhibits resonant behavior, with peak values and Peak positions dependent on particle interaction rates and thermodynamic susceptibilities. Susceptibilities are calculated by modeling the nuclear matter in the density functional approach. The bulk viscosity coefficient peaks at T∼1011 K, with a compression–rarefaction oscillation dissipation time scale of 20–50 ms. Electrical transports incorporate frequency-dependent dynamical screening in quantized electron–ion scattering rates. Consequently, dynamical screening reduces the maxima of electrical and thermal conductivities, shortening corresponding dissipation time scales. These results highlight the crucial role of dissipation coefficients in understanding binary neutron star mergers.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"1 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141744735","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}

{"title":"Direct and Indirect Measurements of the 19F(p,α)16O Reaction at Astrophysical Energies Using the LHASA Detector and the Trojan Horse Method","authors":"Giovanni L. Guardo, Giuseppe G. Rapisarda, Dimiter L. Balabanski, Giuseppe D’Agata, Alessia Di Pietro, Pierpaolo Figuera, Marco La Cognata, Marco La Commara, Livio Lamia, Dario Lattuada, Catalin Matei, Marco Mazzocco, Alessandro A. Oliva, Sara Palmerini, Teodora Petruse, Rosario G. Pizzone, Stefano Romano, Maria Letizia Sergi, Roberta Spartá, X. D. Su, Aurora Tumino, Nikola Vukman","doi":"10.3390/universe10070304","DOIUrl":"https://doi.org/10.3390/universe10070304","url":null,"abstract":"Fluorine is one of the most interesting elements in nuclear astrophysics. Its abundance can provide important hints to constrain the stellar models since fluorine production and destruction are strictly connected to the physical conditions inside the stars. The 19F(p,α)16O reaction is one of the fluorine burning processes and the correction evaluation of its reaction rate is of pivotal importance to evaluate the fluorine abundance. Moreover, the 19F(p,α)16O reaction rate can have an impact for the production of calcium in the first-generation of Population III stars. Here, we present the AsFiN collaboration efforts to the study of the 19F(p,α)16O reaction by means of direct and indirect measurements. On the direct measurements side, an experimental campaign aimed to the measurement of the 19F(p,α0,π)16O reaction is ongoing, taking advantage of the new versatile arrays of silicon strip detectors, LHASA and ELISSA. Moreover, the Trojan Horse Method (THM) was used to determine the 19F(p,α0)16O reaction S(E)-factor in the energy range of astrophysical interest (Ecm≈ 0–1 MeV), showing, for the first time, the presence of resonant structures within the astrophysical energy range. THM has been also applied for the study of the 19F(p,απ)16O reaction; data analysis is ongoing.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"27 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141744736","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}

{"title":"Nonlinear Dynamics in Variable-Vacuum Finsler–Randers Cosmology with Triple Interacting Fluids","authors":"Jianwen Liu, Ruifang Wang, Fabao Gao","doi":"10.3390/universe10070302","DOIUrl":"https://doi.org/10.3390/universe10070302","url":null,"abstract":"Considering the interaction among matter, vacuum, and radiation, this paper investigates the evolution of cosmic dynamics of the varying-vacuum model in a case of Finslerian geometry through dynamic analysis methods. Surprisingly, this model can alleviate the coincidence problem and allows for a stable later cosmological solution corresponding to the accelerating universe.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"17 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141744858","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}

{"title":"Estimate for the Neutrino Magnetic Moment from Pulsar Kick Velocities Induced at the Birth of Strange Quark Matter Neutron Stars","authors":"Alejandro Ayala, Santiago Bernal-Langarica, Daryel Manreza-Paret","doi":"10.3390/universe10070301","DOIUrl":"https://doi.org/10.3390/universe10070301","url":null,"abstract":"We estimate the magnetic moment of electron neutrinos by computing the neutrino chirality flip rate that can occur in the core of a strange quark matter neutron star at birth. We show that this process allows neutrinos to anisotropically escape, thus inducing the star kick velocity. Although the flip from left- to right-handed neutrinos is assumed to happen in equilibrium, the no-go theorem does not apply because right-handed neutrinos do not interact with matter and the reverse process does not happen, producing the loss of detailed balance. For simplicity, we model the star core as consisting of strange quark matter. We find that even when the energy released in right-handed neutrinos is a small fraction of the total energy released in left-handed neutrinos, the process describes kick velocities for natal conditions, which are consistent with the observed ones and span the correct range of radii, temperatures and chemical potentials for typical magnetic field intensities. The neutrino magnetic moment is estimated to be μν∼3.6×10−18μB, where μB is the Bohr magneton. This value is more stringent than the bound found for massive neutrinos in a minimal extension of the standard model.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"35 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141744737","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}