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Universe, Volume 8, Issue 8 (August 2022) – 51 articles

Cover Story (view full-size image): The detection of gravitational waves from binary neutron star systems has rekindled our hopes for unraveling the nature of dense nuclear matter. Specifically, constraints on the tidal deformability of a neutron star can be used to gain information about several neutron star properties using a set of universal relations. Supernova explosions are also promising candidates for the detection of multimessenger signals and may allow us to impose bounds on the binding energy of neutron stars. In this work, we aim to examine the compatibility of hot equations of state with established universal relations and to investigate the possible existence of an empirical relation between the tidal deformability and the binding energy of a neutron star. View this paper
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15 pages, 1276 KiB  
Article
The Kinetic Monte Carlo Model of the Auroral Electron Precipitation into N2-O2 Planetary Atmospheres
by Dmitri Bisikalo, Valery Shematovich and Benoit Hubert
Universe 2022, 8(8), 437; https://doi.org/10.3390/universe8080437 - 22 Aug 2022
Cited by 4 | Viewed by 1243
Abstract
Auroral events are the prominent manifestation of solar/stellar forcing on planetary atmospheres. They are closely related to the energy deposition by and evolution of planetary atmospheres, and their observations are widely used to analyze the composition, structure, and chemistry of the atmosphere under [...] Read more.
Auroral events are the prominent manifestation of solar/stellar forcing on planetary atmospheres. They are closely related to the energy deposition by and evolution of planetary atmospheres, and their observations are widely used to analyze the composition, structure, and chemistry of the atmosphere under study, as well as energy fluxes of the precipitating particles that affect the atmosphere. A numerical kinetic Monte Carlo model had been developed, allowing us to study the processes of precipitation of high-energy auroral electrons into the N2-O2 atmospheres of the rocky planets in the Solar and exosolar planetary systems. This model describes on a molecular level the collisions of auroral electrons and atmospheric gas, taking into account the stochastic nature of collisional scattering at high kinetic energies. The current status of the kinetic model is illustrated in the applications to the auroral events on the Earth such as the production of suprathermal nitrogen atoms due to the electron impact dissociation of N2. It was found that electron impact dissociation of N2 can potentially be an important source of suprathermal N atoms in the auroral regions of the N2-O2 atmosphere of terrestrial-type planets. Such research will allow us to study the odd nitrogen chemistry as an atmospheric marker of the N2-O2 atmosphere of rocky exoplanets. Full article
(This article belongs to the Section Planetary Sciences)
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13 pages, 1816 KiB  
Article
The Classification of Blazar Candidates of Uncertain Types
by Jun-Hui Fan, Ke-Yin Chen, Hu-Bing Xiao, Wen-Xin Yang, Jing-Chao Liang, Guo-Hai Chen, Jiang-He Yang, Yu-Hai Yuan and De-Xiang Wu
Universe 2022, 8(8), 436; https://doi.org/10.3390/universe8080436 - 22 Aug 2022
Cited by 6 | Viewed by 1284
Abstract
In this work, the support vector machine (SVM) method is adopted to separate BL Lacertae objects (BL Lacs) and flat spectrum radio quasars (FSRQs) in the plots of the photon spectrum index against the photon flux, αphlogF, those [...] Read more.
In this work, the support vector machine (SVM) method is adopted to separate BL Lacertae objects (BL Lacs) and flat spectrum radio quasars (FSRQs) in the plots of the photon spectrum index against the photon flux, αphlogF, those of the photon spectrum index against the variability index, αphlogVI and those of the variability index against the photon flux, logVIlogF. Then, we used the dividing lines to distinguish BL Lacs from FSRQs in the blazar candidates of uncertain types from the Fermi/LAT catalogue. Our main conclusions are: 1. We separate BL Lacs and FSRQs by αph=0.123logF+1.170 in the αphlogF plot, αph=0.161logVI+2.594 in the αphlogVI plot and logVI=0.792logF+9.203 in the logVIlogF plot. 2. We obtain 932 BL Lac candidates and possible BL Lac candidates, and 585 FSRQ candidates and possible FSRQ candidates. 3. Discussion is given regarding comparisons with the literature. Full article
(This article belongs to the Special Issue Multi-Messengers of Black Hole Accretion and Emission)
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16 pages, 532 KiB  
Review
Ultra-High-Energy Astroparticles as Probes for Lorentz Invariance Violation
by Rodrigo Guedes Lang, Humberto Martínez-Huerta and Vitor de Souza
Universe 2022, 8(8), 435; https://doi.org/10.3390/universe8080435 - 22 Aug 2022
Cited by 1 | Viewed by 1458
Abstract
Compelling evidence for Lorentz invariance violation (LIV) would demand a complete revision of modern physics. Therefore, searching for a signal or extending the validity of the invariance is fundamental for building our understanding of the extreme phenomena in the Universe. In this paper, [...] Read more.
Compelling evidence for Lorentz invariance violation (LIV) would demand a complete revision of modern physics. Therefore, searching for a signal or extending the validity of the invariance is fundamental for building our understanding of the extreme phenomena in the Universe. In this paper, we review the potential of ultra-high-energy astroparticles in setting limits on LIV. The standard framework of LIV studies in astroparticle physics is reviewed and its use on the electromagnetic and hadronic sectors are discussed. In particular, the current status of LIV tests using experimental data on ultra-high-energy photons and cosmic rays is addressed. A detailed discussion with improved argumentation about the LIV kinematics of the relevant interactions is shown. The main previous results are presented together with new calculations based on recently published astrophysical models. Full article
(This article belongs to the Special Issue Ultra High Energy Photons)
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4 pages, 236 KiB  
Editorial
Properties and Dynamics of Neutron Stars and Proto-Neutron Stars
by Veronica Dexheimer
Universe 2022, 8(8), 434; https://doi.org/10.3390/universe8080434 - 21 Aug 2022
Cited by 1 | Viewed by 1111
Abstract
This Special Issue provides a comprehensive collection of papers that present modern theories to describe neutron star interiors and dynamics [...] Full article
(This article belongs to the Special Issue Properties and Dynamics of Neutron Stars and Proto-Neutron Stars)
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9 pages, 348 KiB  
Article
Search for Gamma-ray Emission from Accretion Flares of Tidal Disruption Events Possibly Associated with the IceCube Neutrinos
by Fang-Kun Peng, Ben-Yang Zhu, Lu-Ming Sun, Xin-Wen Shu and Xiang-Yu Wang
Universe 2022, 8(8), 433; https://doi.org/10.3390/universe8080433 - 21 Aug 2022
Viewed by 1389
Abstract
Outflows or disk-coronas generated in tidal disruption events (TDEs) of supermassive black holes have been suggested as possible sites of high-energy neutrinos. Three TDEs (AT2019dsg, AT2019fdr and AT2019aalc) have been claimed to be associated with high-energy astrophysical neutrinos in multi-messenger follow-ups. No GeV [...] Read more.
Outflows or disk-coronas generated in tidal disruption events (TDEs) of supermassive black holes have been suggested as possible sites of high-energy neutrinos. Three TDEs (AT2019dsg, AT2019fdr and AT2019aalc) have been claimed to be associated with high-energy astrophysical neutrinos in multi-messenger follow-ups. No GeV photons have been detected accompanying the neutrino for the three sources. In this work, we searched for the high-energy gamma-ray emission from a larger sample of TDE candidates observed by the Zwicky Transient Facility (ZTF). No significant GeV emission was observed, and the upper limits of the gamma-ray emission flux are reported. We then performed a stacking analysis for the sample sources and found that the collective gamma-ray emission of this class of sources was also not bright enough to be detected by the Fermi Large Area Telescope (Fermi-LAT). The nondetection of the high-energy gamma-ray emission from the sample TDEs could be due to the fact that the high-energy gamma rays are absorbed by soft photons in the source. Using a model-based hypothesis, the upper limit on the emission radius of the neutrino production is obtained for these TDEs: R<1016 cm for typical TDE parameter values. Full article
(This article belongs to the Special Issue Advances in Astrophysics and Cosmology – in Memory of Prof. Tan Lu)
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12 pages, 422 KiB  
Article
Construction and Evolution of Equilibrium Configurations of the Schrödinger–Poisson System in the Madelung Frame
by Iván Alvarez-Ríos and Francisco S. Guzmán
Universe 2022, 8(8), 432; https://doi.org/10.3390/universe8080432 - 21 Aug 2022
Cited by 3 | Viewed by 1012
Abstract
We present the construction of ground state equilibrium configurations of the Schrödinger–Poisson (SP) system in the Madelung frame and evolve such configuration using finite volume methods. We compare the behavior of these configurations when evolved within the SP and Madelung frames, in terms [...] Read more.
We present the construction of ground state equilibrium configurations of the Schrödinger–Poisson (SP) system in the Madelung frame and evolve such configuration using finite volume methods. We compare the behavior of these configurations when evolved within the SP and Madelung frames, in terms of conservation of mass and energy. We also discuss the issues of the equations in the Madelung frame and others inherent to the numerical methods used to solve them. Full article
(This article belongs to the Special Issue Frontiers in Numerical Precision: From Astrophysics to Cosmology)
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26 pages, 427 KiB  
Review
Noncompactified Kaluza–Klein Gravity
by Seyed Meraj Mousavi Rasouli, Shahram Jalalzadeh and Paulo Moniz
Universe 2022, 8(8), 431; https://doi.org/10.3390/universe8080431 - 21 Aug 2022
Cited by 7 | Viewed by 1274
Abstract
We present a brief description of noncompactified higher-dimensional theories from the perspective of general relativity. More concretely, the Space–Time–Matter theory, or Induced Matter theory, and the reduction procedure used to construct the modified Brans–Dicke theory and the modified Sáez–Ballester theory are briefly explained. [...] Read more.
We present a brief description of noncompactified higher-dimensional theories from the perspective of general relativity. More concretely, the Space–Time–Matter theory, or Induced Matter theory, and the reduction procedure used to construct the modified Brans–Dicke theory and the modified Sáez–Ballester theory are briefly explained. Finally, we apply the latter to the Friedmann–Lemaître–Robertson–Walker (FLRW) cosmological models in arbitrary dimensions and analyze the corresponding solutions. Full article
(This article belongs to the Collection Modified Theories of Gravity and Cosmological Applications)
11 pages, 1495 KiB  
Article
Stark Broadening of Zn III Spectral Lines
by Milan S. Dimitrijević and Magdalena D. Christova
Universe 2022, 8(8), 430; https://doi.org/10.3390/universe8080430 - 20 Aug 2022
Cited by 1 | Viewed by 1067
Abstract
Stark widths for spectral lines within 24 multiplets of Zn III singlets and triplets have been calculated using modified semiempirical method for an electron density of 1017 cm−3 and temperatures from 5000 K up to 100,000 K. The obtained results have [...] Read more.
Stark widths for spectral lines within 24 multiplets of Zn III singlets and triplets have been calculated using modified semiempirical method for an electron density of 1017 cm−3 and temperatures from 5000 K up to 100,000 K. The obtained results have been used for the investigation of the influence of Stark broadening on Zn III spectral lines in stellar atmospheres and for the considerations of Stark width similarites within supermultiplets and transition arrays. Full article
(This article belongs to the Special Issue The Past, Present, and Future of Stellar Spectroscopy)
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14 pages, 293 KiB  
Article
Brans–Dicke Unimodular Gravity
by Alexandre M. R. Almeida, Júlio C. Fabris, Mahamadou Hamani Daouda, Richard Kerner, Hermano Velten and Willian S. Hipólito-Ricaldi
Universe 2022, 8(8), 429; https://doi.org/10.3390/universe8080429 - 20 Aug 2022
Cited by 4 | Viewed by 1120
Abstract
We propose a unimodular version of the Brans–Dicke theory designed with a constrained Lagrangian formulation. The resulting field equations are traceless. The vacuum solutions in the cosmological background reproduce the corresponding solutions of the usual Brans–Dicke theory but with a cosmological constant term. [...] Read more.
We propose a unimodular version of the Brans–Dicke theory designed with a constrained Lagrangian formulation. The resulting field equations are traceless. The vacuum solutions in the cosmological background reproduce the corresponding solutions of the usual Brans–Dicke theory but with a cosmological constant term. A perturbative analysis of the scalar modes is performed and stable and unstable configurations appear, in contrast with the Brans–Dicke case for which only stable configurations occur. On the other hand, tensorial modes in this theory remain the same as in the traditional Brans–Dicke theory. Full article
(This article belongs to the Section Gravitation)
9 pages, 281 KiB  
Article
On Possible Origin of an Artificial Wormhole
by Alexander A. Kirillov and Elena P. Savelova
Universe 2022, 8(8), 428; https://doi.org/10.3390/universe8080428 - 19 Aug 2022
Cited by 4 | Viewed by 1230
Abstract
We assume the picture in which a vacuum is filled with virtual wormholes. The presence of external fields changes the distribution of virtual wormholes and, in principle, allows for the creation of a coherent structure that can work as an actual wormhole or [...] Read more.
We assume the picture in which a vacuum is filled with virtual wormholes. The presence of external fields changes the distribution of virtual wormholes and, in principle, allows for the creation of a coherent structure that can work as an actual wormhole or the Alcubierre bubble. We establish the explicit functional relationship between the external field and the distribution of virtual wormholes in vacuum. This opens a way for examining the question about the possibility of the artificial creation of such objects in a laboratory. We show that weak and quasihomogeneous fields suppress the density of wormholes and cannot be used. We also discuss the existence of a threshold for the intensity of an external field beyond which the formation of wormhole-type structures becomes possible. Full article
(This article belongs to the Special Issue Recent Advances in Wormhole Physics)
20 pages, 1658 KiB  
Review
Dark Matter in Supersymmetry
by Sven Heinemeyer and Carlos Muñoz
Universe 2022, 8(8), 427; https://doi.org/10.3390/universe8080427 - 18 Aug 2022
Cited by 2 | Viewed by 1281
Abstract
Supersymmetry is a well-motivated theory for physics beyond the Standard Model. In particular, supersymmetric models can naturally possess dark matter candidates that can give rise to the measured dark matter content of the universe. We review several models that have been analyzed with [...] Read more.
Supersymmetry is a well-motivated theory for physics beyond the Standard Model. In particular, supersymmetric models can naturally possess dark matter candidates that can give rise to the measured dark matter content of the universe. We review several models that have been analyzed with regard to dark matter by groups based in Spain in recent years. These models include, in particular, the Minimal Supersymmetric Standard Model (MSSM) and the ‘μ from ν’ Supersymmetric Standard Model (μνSSM) in various versions. Full article
(This article belongs to the Special Issue Studying the Universe from Spain)
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21 pages, 387 KiB  
Article
Spinor-Vector Duality and the Swampland
by Alon E. Faraggi
Universe 2022, 8(8), 426; https://doi.org/10.3390/universe8080426 - 18 Aug 2022
Viewed by 1102
Abstract
The Swampland Program aims to address the question, “when does an effective field theory model of quantum gravity have an ultraviolet complete embedding in string theory?”, and can be regarded as a bottom-up approach for investigations of quantum gravity. An alternative top-down approach [...] Read more.
The Swampland Program aims to address the question, “when does an effective field theory model of quantum gravity have an ultraviolet complete embedding in string theory?”, and can be regarded as a bottom-up approach for investigations of quantum gravity. An alternative top-down approach aims to explore the imprints and the constraints imposed by string-theory dualities and symmetries on the effective field theory representations of quantum gravity. The most celebrated example of this approach is mirror symmetry. Mirror symmetry was first observed in worldsheet contructions of string compactifications. It was completely unexpected from the effective field theory point of view, and its implications in that context were astounding. In terms of the moduli parameters of toroidally compactified Narain spaces, mirror symmetry can be regarded as arising from mappings of the moduli of the internal compactified space. Spinor-vector duality, which was discovered in worldsheet constructions of string vacua, is an extension of mirror symmetry that arises from mappings of the Wilson line moduli and provide a probe to constrain and explore the moduli spaces of (2, 0) string compactifications. Mirror symmetry and spinor-vector duality are mere two examples of a much wider symmetry structure, whose implications have yet to be unravelled. A mapping between supersymmetric and non-supersymmetric vacua is briefly discussed. T-duality is another important property of string theory and can be thought of as phase-space duality in compact space. I propose that manifest phase-space duality and the related equivalence postulate of quantum mechanics provide the background independent overarching principles underlying quantum gravity. Full article
(This article belongs to the Section High Energy Nuclear and Particle Physics)
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20 pages, 1347 KiB  
Article
Analysis of the Capability of Detection of Extensive Air Showers by Simple Scintillator Detectors
by Jerzy Seweryn Pryga, Weronika Stanek, Krzysztof Wiesław Woźniak, Piotr Homola, Kevin Almeida Cheminant, Sławomir Stuglik, David Alvarez-Castillo, Łukasz Bibrzycki, Marcin Piekarczyk, Olaf Bar, Tadeusz Wibig, Arman Tursunov, Michał Niedźwiecki, Tomasz Sośnicki and Krzysztof Rzecki
Universe 2022, 8(8), 425; https://doi.org/10.3390/universe8080425 - 18 Aug 2022
Cited by 2 | Viewed by 1634
Abstract
One of the main objectives of the CREDO project is to register cosmic-ray cascades in many distributed detectors in the search for so-called Cosmic-Ray Ensembles (CRE). This requires precise knowledge of the probability of detection of individual Extensive Air Showers (EAS) in a [...] Read more.
One of the main objectives of the CREDO project is to register cosmic-ray cascades in many distributed detectors in the search for so-called Cosmic-Ray Ensembles (CRE). This requires precise knowledge of the probability of detection of individual Extensive Air Showers (EAS) in a very wide range of energies and an analysis of their correlations. The standard approach based on detailed and extensive simulations is not possible for many such systems; thus, a faster method is developed. Knowing the characteristics of EAS from more general simulations, any required probability is calculated. Such probability depends on particle density at a given point, which is a function of the distance from the centre of the cascade, the energy, mass and the zenith angle of the primary cosmic-ray particle. It is necessary to use proper distribution of the number of secondary particles reaching the ground and their fluctuations. Finally, to calculate the total probability of EAS detection, the primary cosmic-ray spectrum and abundance of various particles in it have to be taken into account. The effective probability can be used to estimate the expected number of EAS events measured by a set of small detectors. In this work, results from several versions of calculations, with different complexity levels, are presented and compared with the first measurement performed with a test detector system. These results confirm that the majority of events observed with this small detector array are caused by cosmic-ray particles with very high energies. Such analysis can be also useful for the design of more effective systems in the future. Slightly larger systems of simple detectors may be used to distinguish cascades initiated by photons from those started from other primary cosmic-ray particles. Full article
(This article belongs to the Special Issue Ultra High Energy Photons)
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12 pages, 7921 KiB  
Article
The Simultaneous Influence of the Solar Wind and Earth’s Magnetic Field on the Weather
by Ramy Mawad, Mahmoud Fathy and Essam Ghamry
Universe 2022, 8(8), 424; https://doi.org/10.3390/universe8080424 - 17 Aug 2022
Cited by 1 | Viewed by 3254
Abstract
The correlation between simultaneous observations of the atmospheric weather and geomagnetic field has been studied during the period 1999–2021. We found that there is a strong correlation between atmospheric weather and the geomagnetic field. This correlation is lower at the Earth’s surface, due [...] Read more.
The correlation between simultaneous observations of the atmospheric weather and geomagnetic field has been studied during the period 1999–2021. We found that there is a strong correlation between atmospheric weather and the geomagnetic field. This correlation is lower at the Earth’s surface, due to the strong influence of the source of the magnetic field coming from the core of the Earth. In contrast, when we move towards the outer magnetosphere, the interaction between weather and the magnetic field strength is stronger. This indicates that the weather and external magnetic field could play an important role in the variations of the atmospheric weather parameters. Full article
(This article belongs to the Section Space Science)
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9 pages, 399 KiB  
Article
The Galactic Interstellar Medium Has a Preferred Handedness of Magnetic Misalignment
by Zhiqi Huang
Universe 2022, 8(8), 423; https://doi.org/10.3390/universe8080423 - 17 Aug 2022
Cited by 2 | Viewed by 1595
Abstract
The Planck mission detected a positive correlation between the intensity (T) and B-mode polarization of the Galactic thermal dust emission. The TB correlation is a parity-odd signal, whose statistical mean vanishes in models with mirror symmetry. Recent work has [...] Read more.
The Planck mission detected a positive correlation between the intensity (T) and B-mode polarization of the Galactic thermal dust emission. The TB correlation is a parity-odd signal, whose statistical mean vanishes in models with mirror symmetry. Recent work has shown, with strong evidence, that local handedness of the misalignment between the dust filaments and the sky-projected magnetic field produces TB signals. However, it remains unclear whether the observed global TB signal is caused by statistical fluctuations of magnetic misalignment angles or whether some parity-violating physics in the interstellar medium sets a preferred misalignment handedness. The present work aims to make a quantitative statement about how confidently the statistical fluctuation interpretation is ruled out by filament-based simulations of polarized dust emission. We use the publicly available DUSTFILAMENTS code to simulate the dust emission from filaments whose magnetic misalignment angles are symmetrically randomized and construct the probability density function of ξp, a weighted sum of the TB power spectrum. We find that the Planck data have a ≳10σ tension with the simulated ξp distribution. Our results strongly support the idea that the Galactic filament misalignment has a preferred handedness, whose physical origin is yet to be identified. Full article
(This article belongs to the Special Issue Cosmic Microwave Background)
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19 pages, 388 KiB  
Article
On the Issue of Magnetic Monopoles in the Prospect of UHE Photon Searches
by Łukasz Bratek and Joanna Jałocha
Universe 2022, 8(8), 422; https://doi.org/10.3390/universe8080422 - 15 Aug 2022
Cited by 1 | Viewed by 1033
Abstract
Ultra-high energy (UHE) photons with energies exceeding 1018eV can potentially be observed. They are produced in various processes involving electrically charged particles. However, more exotic scenarios are also possible. UHE photons could be emitted in encounters of massive magnetically charged monopole-antimonopole [...] Read more.
Ultra-high energy (UHE) photons with energies exceeding 1018eV can potentially be observed. They are produced in various processes involving electrically charged particles. However, more exotic scenarios are also possible. UHE photons could be emitted in encounters of massive magnetically charged monopole-antimonopole pairs or in processes associated with monopoles accelerated to high energies, typically 1021eV or beyond. Observing UHE photons can pose constraints on the properties of magnetic monopoles. There are compelling theoretical reasons in favor of the presence of magnetic monopoles in nature. The predicted observational signatures of these particles are therefore searched for in dedicated experiments currently in operation. Despite these attempts, magnetic monopoles have yet to be empirically proved. There are also theoretical reasons why magnetic monopoles allowed by Dirac’s theory might not be realized in nature in the form of isolated particles. Detection or non-detection of UHE photon signatures of magnetic monopoles would bring us closer to solving this fascinating puzzle. Full article
(This article belongs to the Special Issue Ultra High Energy Photons)
38 pages, 3885 KiB  
Review
Interstellar Propulsion Using Laser-Driven Inertial Confinement Fusion Physics
by Kelvin F. Long
Universe 2022, 8(8), 421; https://doi.org/10.3390/universe8080421 - 15 Aug 2022
Cited by 6 | Viewed by 3354
Abstract
To transport a spacecraft to distances far beyond the solar heliosphere and around the planets of other stars will require advanced space propulsion systems that go beyond the existing technological state of the art. The release of fusion energy from the interaction of [...] Read more.
To transport a spacecraft to distances far beyond the solar heliosphere and around the planets of other stars will require advanced space propulsion systems that go beyond the existing technological state of the art. The release of fusion energy from the interaction of two low mass atomic nuclei that are able to overcome the Coulomb barrier offers the potential for ∼1011J/g specific energy release and implies that robotic missions to the nearby stars to distances of ∼5–10 ly may be possible in trip durations of the order of ∼50–100 years, travelling at cruise speeds of the order of ∼0.05–0.15 c. Such missions would be characterised with ∼kN-MN thrust levels, ∼GW-TW jet powers, ∼kW/kg-MW/kg specific powers. One of the innovative methods by which fusion reactions can be ignited is via the impingement of laser beams onto an inertial confinement fusion capsule, imploding it to a thermonuclear state. This paper gives an overview of the physics of inertial confinement fusion and the interaction of a laser beam with a capsule to include the simulation of a 1D particle-in-cell code calculation to illustrate the effects. In the application to deep space missions, various spacecraft concepts from the literature are discussed, and the range of values assumed for the pulse frequency, burn fraction and areal density appropriate for the mission are presented. It is concluded that advanced space propulsion via inertial confinement fusion is a plausible part of our future, provided that experimental validation of ignition is on the horizon and numerical models for feasibility concepts are developed to high fidelity and on a consistent basis. Full article
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23 pages, 3630 KiB  
Article
Centrality-Dependent Chemical Potentials of Light Hadrons and Quarks Based on pT Spectrum and Particle Yield Ratio in Au-Au Collisions at RHIC Energies
by Xing-Wei He, Hua-Rong Wei, Bi-Hai Hong, Hong-Yu Wu, Wei-Ting Zhu and Feng-Min Wu
Universe 2022, 8(8), 420; https://doi.org/10.3390/universe8080420 - 12 Aug 2022
Viewed by 1176
Abstract
We analyze the pT spectra of π±, K±, p, and p¯ produced in different centralities’ Au-Au collisions at different collision energies from 7.7 to 62.4 GeV using a two-component Erlang distribution in the framework of a [...] Read more.
We analyze the pT spectra of π±, K±, p, and p¯ produced in different centralities’ Au-Au collisions at different collision energies from 7.7 to 62.4 GeV using a two-component Erlang distribution in the framework of a multi-source thermal model. The fitting results are consistent with the experimental data, and the yield ratios of negative to positive particles are obtained from the normalization constants. Based on the yield ratios, the chemical potentials of light hadrons (π, K, and p) and quarks (u, d, and s) are extracted. This study shows that only the yield ratios of p decrease with the increase in centrality. The logarithms of these yield ratios in the same centrality show obvious linear dependence on 1/sNN. The extracted chemical potentials (the absolute magnitude for π) of light hadrons and quarks decrease with the increase in energy. The curves of chemical potential vs. energy for all centralities derived from the linear fits of the logarithms of the yield ratio as a function of energy have their maximum (the absolute magnitude for π) at the same energy of 3.526 GeV, which is possibly the critical energy of phase transition from a liquid-like hadron state to a gas-like quark state in the collision system. Full article
(This article belongs to the Special Issue Collectivity in High-Energy Proton-Proton and Heavy-Ion Collisions)
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17 pages, 349 KiB  
Article
Galaxy Phase-Space Density Data Preclude That Bose–Einstein Condensate Be the Total Dark Matter
by Héctor J. de Vega and Norma G. Sanchez
Universe 2022, 8(8), 419; https://doi.org/10.3390/universe8080419 - 11 Aug 2022
Cited by 13 | Viewed by 1820
Abstract
Ultralight scalars with a typical mass of the order m1022 eV and light scalars forming a Bose–Einstein condensate (BEC) exhibit a Jeans length in the kpc scale and were therefore proposed as dark matter (DM) candidates. Our treatment here [...] Read more.
Ultralight scalars with a typical mass of the order m1022 eV and light scalars forming a Bose–Einstein condensate (BEC) exhibit a Jeans length in the kpc scale and were therefore proposed as dark matter (DM) candidates. Our treatment here is generic, independent of the particle physics model and applies to all DM BEC, in both in or out of equilibrium situations. Two observed quantities crucially constrain DM in an inescapable way: the average DM density ρDM and the phase-space density Q. The observed values of ρDM and Q in galaxies today constrain both the possibility to form a BEC, and the DM mass m. These two constraints robustly exclude the axion DM that decouples after inflation. Moreover, the value m1022 eV can only be obtained with a number of ultrarelativistic degrees of freedom at decoupling in the trillions, which is impossible for decoupling in the radiation dominated era. In addition, we find for the axion vacuum misalignment scenario that axions are produced strongly out of thermal equilibrium and that the axion mass in such a scenario turns to be 17 orders of magnitude too large to reproduce the observed galactic structures. Moreover, we also consider inhomogenous gravitationally bounded BEC’s supported by the bosonic quantum pressure independently of any particular particle physics scenario. For a typical size R kpc and compact object masses M107M they remarkably lead to the same particle mass m1022 eV as the BEC free-streaming length. However, the phase-space density for the gravitationally bounded BEC’s turns out to be more than sixty orders of magnitude smaller than the galaxy-observed values. We conclude that the BEC cannot be the total DM. The axion can be candidates to be only part of the DM of the universe. Besides, an axion in the mili-eV scale may be a relevant source of dark energy through the zero point cosmological quantum fluctuations. Full article
(This article belongs to the Collection Women Physicists in Astrophysics, Cosmology and Particle Physics)
12 pages, 291 KiB  
Article
A Proposal to Solve Finite N Matrix Theory: Reduced Model Related to Quantum Cosmology
by José Luis López-Picón, Octavio Obregón and José Ríos-Padilla
Universe 2022, 8(8), 418; https://doi.org/10.3390/universe8080418 - 11 Aug 2022
Viewed by 1067
Abstract
The SU(N) invariant model of matrix theory that emerges as the regularization of the 11-dimensional super membrane is studied. This matrix model is identified with M theory in the limit N. It has been conjectured that [...] Read more.
The SU(N) invariant model of matrix theory that emerges as the regularization of the 11-dimensional super membrane is studied. This matrix model is identified with M theory in the limit N. It has been conjectured that matrix models are also relevant for finite N where several examples and arguments have been given in the literature. By the use of a Dirac-like formulation usually developed in finding solutions in Supersymmetric Quantum Cosmology, we exhibit a method that could solve, in principle, any finite N model. As an example of our procedure, we choose a reduced SU(2) model and also show that this matrix model contains relevant supersymmetric quantum cosmological models as solutions. By these means, our solutions constitute an example in order to consider why the finite N matrix models are also relevant. Since the degrees of freedom of matrix models are, in some limit, identified with those of Super Yang Mills Theory SYM with a finite number of supercharges, our methodology offers the possibility, through some but yet unspecified identification, to relate the quantization presented here with that of SYM theory for any finite N. Full article
(This article belongs to the Section Foundations of Quantum Mechanics and Quantum Gravity)
16 pages, 2872 KiB  
Review
Activity of Comets Constrains the Chemistry and Structure of the Protoplanetary Disk
by Marco Fulle
Universe 2022, 8(8), 417; https://doi.org/10.3390/universe8080417 - 10 Aug 2022
Cited by 1 | Viewed by 1384
Abstract
Recent data of molecular clouds and protoplanetary disks constrain the composition and structure of the disk and planetesimals. Laboratory experiments suggest that dust accretion in disks stops at pebble sizes. Sublimation and recondensation of water ice at the disk water-snow line suggest that [...] Read more.
Recent data of molecular clouds and protoplanetary disks constrain the composition and structure of the disk and planetesimals. Laboratory experiments suggest that dust accretion in disks stops at pebble sizes. Sublimation and recondensation of water ice at the disk water-snow line suggest that pebbles split into water-rich and water-poor ones. The same conclusion has been recently reached by models of cometary activity consistent with the structure of porous Interplanetary Dust Particles (IDPs) and of porous dust collected by the Stardust and Rosetta missions. The observation of crystalline water ice in protoplanetary disks by the Herschel satellite, the erosion of comets, and the seasonal evolution of the nucleus color require that the two pebble families have a water-ice mass fraction close to 33% and 2%, respectively. Here, we show that the diversity of comets is thus due to random mixtures with different area fractions Ap and Ar of water-poor and water-rich pebbles, predicting most of the data observed in comets: why the deuterium-to-hydrogen ratio in cometary water correlates to the ratio Ap/Ar, which pebbles dominate the activity of Dynamically New Comets (DNCs), what is the origin of cometary outbursts, why comets cannot be collisional products, and why the brightness evolution of DNCs during their first approach to the Sun is actually unpredictable. Full article
(This article belongs to the Special Issue The Advances of Comets' Activity)
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18 pages, 1312 KiB  
Article
Advances in Mass Spectrometers for Flyby Space Missions for the Analysis of Biosignatures and Other Complex Molecules
by Rico G. Fausch, Janis A. Schertenleib and Peter Wurz
Universe 2022, 8(8), 416; https://doi.org/10.3390/universe8080416 - 10 Aug 2022
Cited by 3 | Viewed by 1654
Abstract
Spacecraft flybys provide access to the chemical composition of the gaseous envelope of the planetary object. Typical relative encounter velocities range from km/s to tens of km/s in flybys. For speeds exceeding about 5 km/s, modern mass spectrometers analyzing the rapidly encountering gas [...] Read more.
Spacecraft flybys provide access to the chemical composition of the gaseous envelope of the planetary object. Typical relative encounter velocities range from km/s to tens of km/s in flybys. For speeds exceeding about 5 km/s, modern mass spectrometers analyzing the rapidly encountering gas suffer from intrinsic hypervelocity impact-induced fragmentation processes causing ambiguous results when analyzing complex molecules. In this case, instruments use an antechamber, inside which the incoming species collide many times with the chamber wall. These collisions cause the desired deceleration and thermalization of the gas molecules. However, these collisions also dissociate molecular bonds, thus fragmenting the molecules, and possibly forming new ones precluding scientists from inferring the actual chemical composition of the sampled gas. We developed a novel time-of-flight mass spectrometer that handles relative encounter velocities of up to 20 km/s omitting an antechamber and its related fragmentation. It analyzes the complete mass range of m/z 1 to 1000 at an instance. This innovation leads to unambiguous analysis of complex (organic) molecules. Applied to Enceladus, Europa or Io, it will provide reliable chemical composition datasets for exploration of the Solar System to determine its status, origin and evolution. Full article
(This article belongs to the Special Issue Developments and Technology Trends in the Space-Borne Instrumentation)
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4 pages, 222 KiB  
Editorial
Editorial of Modified Theories of Gravity and Cosmological Applications
by Panayiotis Stavrinos and Emmanuel Saridakis
Universe 2022, 8(8), 415; https://doi.org/10.3390/universe8080415 - 9 Aug 2022
Viewed by 1086
Abstract
General Relativity is a theory of gravity that describes some of the effects of gravity with high accuracy, such as solar system tests, gravitational lensing, gravitational waves, black holes, deflection angle, etc [...] Full article
(This article belongs to the Special Issue Modified Theories of Gravity and Cosmological Applications)
16 pages, 2342 KiB  
Article
Phenomenological Inflationary Model in Supersymmetric Quantum Cosmology
by Nephtalí E. Martínez-Pérez, Cupatitzio Ramírez-Romero and Víctor M. Vázquez-Báez
Universe 2022, 8(8), 414; https://doi.org/10.3390/universe8080414 - 6 Aug 2022
Cited by 2 | Viewed by 1104
Abstract
We consider the effective evolution of a phenomenological model from FLRW supersymmetric quantum cosmology with a scalar field. The scalar field acts as a clock and inflaton. We examine a family of simple superpotentials that produce an inflation whose virtual effect on inhomogeneous [...] Read more.
We consider the effective evolution of a phenomenological model from FLRW supersymmetric quantum cosmology with a scalar field. The scalar field acts as a clock and inflaton. We examine a family of simple superpotentials that produce an inflation whose virtual effect on inhomogeneous fluctuations shows very good agreement with PLANCK observational evidence for the tensor-to-scalar ratio and the scalar spectral index. Full article
(This article belongs to the Special Issue Quantum Gravity Phenomenology II)
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10 pages, 259 KiB  
Article
On the Hilbert Space in Quantum Gravity
by Ednardo Paulo Spaniol, Ronni Geraldo Gomes Amorim and Sergio Costa Ulhoa
Universe 2022, 8(8), 413; https://doi.org/10.3390/universe8080413 - 5 Aug 2022
Viewed by 1094
Abstract
This article deals with the fractional problem of Sturm–Liouville and the Hilbert space associated with the solutions of this differential equation. We apply a quantization procedure to Schwarzschild space–time and obtain a fractional differential equation. The Hilbert space for these solutions is established. [...] Read more.
This article deals with the fractional problem of Sturm–Liouville and the Hilbert space associated with the solutions of this differential equation. We apply a quantization procedure to Schwarzschild space–time and obtain a fractional differential equation. The Hilbert space for these solutions is established. We used equations arising from quantization for the FRW and Reissner–Nordstron metrics to build the respective Hilbert spaces. Full article
(This article belongs to the Special Issue Quantum Gravity Phenomenology)
19 pages, 11949 KiB  
Article
Transient Luminous Events in the Lower Part of the Atmosphere Originated in the Peripheral Regions of a Thunderstorm
by Ashot Chilingarian, Gagik Hovsepyan, Tigran Karapetyan, Balabek Sargsyan and Ekaterina Svechnikova
Universe 2022, 8(8), 412; https://doi.org/10.3390/universe8080412 - 5 Aug 2022
Cited by 5 | Viewed by 1219
Abstract
We present and discuss transient luminous events (TLEs) in the lower atmosphere, observed during large disturbances of the near-surface electric fields (NSEF) and coinciding with large enhancements of the particle fluxes (thunderstorm ground enhancements—TGEs). Despite large distances from the strongest electric field region, [...] Read more.
We present and discuss transient luminous events (TLEs) in the lower atmosphere, observed during large disturbances of the near-surface electric fields (NSEF) and coinciding with large enhancements of the particle fluxes (thunderstorm ground enhancements—TGEs). Despite large distances from the strongest electric field region, the maximum energy of TGE particles on 22 and 25 May 2018 reaches ≈40 MeV. Thus, the accelerating electric field reaches ≈2.0 keV/cm far from the zone of the strong lightning activity on the periphery of the storm. Light glows appearing simultaneously in the skies may be due to the local charge rearrangement generating a small illuminating discharge without initiating the lightning flash. This type of charge rearrangement does not lower the potential difference in the cloud, allowing the electron accelerator to operate and send particle fluxes in the direction of the earth’s surface. Full article
(This article belongs to the Section Planetary Sciences)
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16 pages, 455 KiB  
Review
Is Core Angular Momentum Key to the Giant Dynamo?
by Klaus-Peter Schröder and Renada Konstantinova-Antova
Universe 2022, 8(8), 411; https://doi.org/10.3390/universe8080411 - 5 Aug 2022
Viewed by 929
Abstract
The pros and cons of core angular momentum dissipation into the convective envelopes of giants as a driver of giant activity is discussed in face of the observational evidence, which points to two ”magnetic strips“, in the HRD, where in the first, at [...] Read more.
The pros and cons of core angular momentum dissipation into the convective envelopes of giants as a driver of giant activity is discussed in face of the observational evidence, which points to two ”magnetic strips“, in the HRD, where in the first, at the base of the RGB, activity of moderate mass stars is freshly started and rejuvenated in the second strip, ascending along the mid-AGB. It remains unclear, though, which depths the giant dynamo is operating. Both concentrations of active giants in the HRD are related to stellar evolution phases with core contraction and spin-up, and presumably the dissipation of angular momentum into the convective envelope above. At the same time, the latter has a small Rossby number by virtue of its increasing convective turn-over time—i.e., favourable conditions to run an alpha-omega dynamo. Since coronal X-ray emission appears to give an incomplete picture of stellar activity across the HR diagramme, we here focus on the observed chromospheric emissions across the giant branches and find good agreement with the magnetic field Zeeman-detections there. Stable evolution phases—solar-type main sequence stars with central hydrogen burning and moderate mass, central Helium burning K giants—by contrast demonstrate a decline in activity, apparently imposed by magnetic braking, as such stars are also slower rotators. In that sense, the observed picture of two magnetic activity strips across the HR diagramme could empirically be explained as an interplay of magnetic braking during the stable phase of core helium burning and supply by internal angular momentum during episodes of fast core contraction with core spin-up and angular momentum dredge-up, while meeting dynamo-friendly envelope conditions. At the same time, the sporadic external supply of angular momentum by the engulfment events of a planet, in the course of the evolutionary envelope expansion, may explain some cases of exceptional activity outside the here-described general picture. Full article
(This article belongs to the Special Issue Magnetic Fields and Activity through Stellar Evolution)
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25 pages, 4208 KiB  
Review
Towards In-Situ Geochemical Analysis of Planetary Rocks and Soils by Laser Ablation/Ionisation Time-of-Flight Mass Spectrometry
by Marek Tulej, Peter Keresztes Schmidt, Salome Gruchola, Coenraad P. de Koning, Kristina A. Kipfer, Nikita J. Boeren, Niels F. W. Ligterink, Andreas Riedo and Peter Wurz
Universe 2022, 8(8), 410; https://doi.org/10.3390/universe8080410 - 4 Aug 2022
Viewed by 2525
Abstract
Spectroscopic instruments were a part of payloads on orbiter and lander missions and delivered vast data sets to explore minerals, elements and molecules on air-less rocky planets, asteroids and comets on global and local scales. To answer current space science questions, the chemical [...] Read more.
Spectroscopic instruments were a part of payloads on orbiter and lander missions and delivered vast data sets to explore minerals, elements and molecules on air-less rocky planets, asteroids and comets on global and local scales. To answer current space science questions, the chemical composition of planetary rocks and soils at grain scale is required, as well as measurements of element (isotope) concentrations down to the part per million or lower. Only mass spectrometric methods equipped with laser sampling ion sources can deliver the necessary information. Laser sampling techniques can reduce the dimensions of the investigated sample material down to micrometre scale, allowing for the composition analysis of grain-sized objects or thin mineral layers with sufficiently high spatial resolution, such that important geological processes can be recognised and studied as they progressed in time. We describe the performance characteristics, when applied to meteorite and geological samples, of a miniaturised laser ablation/ionisation mass spectrometer (named LMS) system that has been developed in our group. The main advantages of the LMS instrument over competing techniques are illustrated by examples of high spatial (lateral and vertical) resolution studies in different meteorites, terrestrial minerals and fossil-like structures in ancient rocks for most elements of geochemical interest. Top-level parameters, such as dimension, weight, and power consumption of a possible flight design of the LMS system are presented as well. Full article
(This article belongs to the Special Issue Developments and Technology Trends in the Space-Borne Instrumentation)
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23 pages, 499 KiB  
Article
Chemical Tracing and the Origin of Carbon in the Galactic Disk
by Bengt Gustafsson
Universe 2022, 8(8), 409; https://doi.org/10.3390/universe8080409 - 4 Aug 2022
Cited by 2 | Viewed by 1313
Abstract
A basic problem in studies of the evolution of chemical elements in galaxies is the uncertainties in the yields of elements produced by different types of stars. The possibilities of tracing the sites producing chemical elements and corresponding yields in stellar populations by [...] Read more.
A basic problem in studies of the evolution of chemical elements in galaxies is the uncertainties in the yields of elements produced by different types of stars. The possibilities of tracing the sites producing chemical elements and corresponding yields in stellar populations by studying ratios of abundances in stars of different ages and metallicities, with an approach with minimal assumptions concerning the yields, is explored by means of simple models of Galactic chemical evolution. Elemental abundances of carbon and oxygen, obtained by recent observations of samples of solar-type stars with estimated ages in the thin disk of the Galaxy, are analysed. Constraints on the yields from winds of intermediate-mass stars and of hot massive stars, including core-collapse supernovae, are derived. It is found that a dominating contribution of carbon from massive stars is most probable, although stars in the mass interval of two to three solar masses may have provided some amounts of carbon in the Sun. The results are consistent with those obtained by using theoretical yields and more elaborate models of Galactic evolution. The uncertainties as regards the mixing of stellar populations due to migration of stars in the Galactic disk may be important for the conclusions. Variations in the star formation rates, lack of chemical homogeneity in the Galactic gas, the inflow of gas from the intergalactic space and possible variations in the Initial mass function may also limit conclusions about the sites and their yields. Very accurate abundance ratios and the determination of stellar ages provide further important constraints on the yields. Full article
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10 pages, 279 KiB  
Article
Curvature Inheritance Symmetry in Ricci Flat Spacetimes
by Mohammad Salman, Musavvir Ali and Mohd Bilal
Universe 2022, 8(8), 408; https://doi.org/10.3390/universe8080408 - 4 Aug 2022
Cited by 2 | Viewed by 1227
Abstract
In this article, we study curvature inheritance symmetry in Ricci flat spacetimes. We show that, if Ricci flat spacetimes are not of Petrov type N, and admit curvature inheritance symmetries, then the only existing symmetries are conformal motions. We also prove that the [...] Read more.
In this article, we study curvature inheritance symmetry in Ricci flat spacetimes. We show that, if Ricci flat spacetimes are not of Petrov type N, and admit curvature inheritance symmetries, then the only existing symmetries are conformal motions. We also prove that the only Ricci flat spacetime that admits a proper curvature inheritance symmetry and is of Petrov type other than N is the flat spacetime. Next, we find that the vacuum pp-waves of Petrov type N if admit curvature inheritance symmetry, then conformal motion implies homothetic motion. Full article
(This article belongs to the Special Issue Spacetime Symmetry)
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