Congratulations to Prof. Roger Penrose, Advisory Board member of Universe, for receiving the Nobel Prize in Physics 2020.
Journal Description
Universe
Universe
is a peer-reviewed open access journal focused on principles and new discoveries in the universe. Universe is published monthly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, SCIE (Web of Science), Astrophysics Data System, INSPIRE, CAPlus / SciFinder, Inspec, and other databases.
- Journal Rank: JCR - Q2 (Astronomy & Astrophysics) / CiteScore - Q2 (General Physics and Astronomy)
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 20.6 days after submission; acceptance to publication is undertaken in 2.9 days (median values for papers published in this journal in the second half of 2023).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
- Companion journal: Astronomy.
Impact Factor:
2.9 (2022);
5-Year Impact Factor:
2.4 (2022)
Latest Articles
Impact of Newly Measured Nuclear Reaction Rates on 26Al Ejected Yields from Massive Stars
Universe 2024, 10(5), 204; https://doi.org/10.3390/universe10050204 - 01 May 2024
Abstract
Over the last three years, the rates of all the main nuclear reactions involving the destruction and production of 26Al in stars (26Al(n, p)26Mg, 26Al(n, α)23Na, 26Al(p
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Over the last three years, the rates of all the main nuclear reactions involving the destruction and production of 26Al in stars (26Al(n, p)26Mg, 26Al(n, α)23Na, 26Al(p, γ)27Si and 25Mg(p, γ)26Al) have been re-evaluated thanks to new high-precision experimental measurements of their crosssections at energies of astrophysical interest, considerably reducing the uncertainties in the nuclear physics affecting their nucleosynthesis. We computed the nucleosynthetic yields ejected by the explosion of a high-mass star (20 M⊙, Z = 0.0134) using the FRANEC stellar code, considering two explosion energies, 1.2 × 1051 erg and 3 × 1051 erg. We quantify the change in the ejected amount of 26Al and other key species that is predicted when the new rate selection is adopted instead of the reaction rates from the STARLIB nuclear library. Additionally, the ratio of our ejected yields of 26Al to those of 14 other short-lived radionuclides (36Cl, 41Ca, 53Mn, 60Fe, 92Nb, 97Tc, 98Tc, 107Pd, 126Sn, 129I, 36Cs, 146Sm, 182Hf, 205Pb) are compared to early solar system isotopic ratios, inferred from meteorite measurements. The total ejected 26Al yields vary by a factor of ~3 when adopting the new rates or the STARLIB rates. Additionally, the new nuclear reaction rates also impact the predicted abundances of short-lived radionuclides in the early solar system relative to 26Al. However, it is not possible to reproduce all the short-lived radionuclide isotopic ratios with our massive star model alone, unless a second stellar source could be invoked, which must have been active in polluting the pristine solar nebula at a similar time of a core-collapse supernova.
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(This article belongs to the Special Issue Recent Outcomes and Future Challenges in Nuclear Astrophysics)
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Supernova Remnants in Gamma Rays
by
Andrea Giuliani and Martina Cardillo
Universe 2024, 10(5), 203; https://doi.org/10.3390/universe10050203 - 01 May 2024
Abstract
In the 1960s, the remnants of supernova explosions (SNRs) were indicated as a possible source of galactic cosmic rays through the Diffusive Shock Acceleration (DSA) mechanism. Since then, the observation of gamma-ray emission from relativistic ions in these objects has been one of
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In the 1960s, the remnants of supernova explosions (SNRs) were indicated as a possible source of galactic cosmic rays through the Diffusive Shock Acceleration (DSA) mechanism. Since then, the observation of gamma-ray emission from relativistic ions in these objects has been one of the main goals of high-energy astrophysics. A few dozen SNRs have been detected at GeV and TeV photon energies in the last two decades. However, these observations have shown a complex phenomenology that is not easy to reduce to the standard paradigm based on DSA acceleration. Although the understanding of these objects has greatly increased, and their nature as efficient electron and proton accelerators has been observed, it remains to be clarified whether these objects are the main contributors to galactic cosmic rays. Here, we review the observations of -ray emission from SNRs and the perspectives for the future.
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(This article belongs to the Special Issue Recent Advances in Gamma Ray Astrophysics and Future Perspectives)
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Theory of Majorana-Type Heavy Ion Double Charge Exchange Reactions by Pion–Nucleon Isotensor Interactions
by
Horst Lenske, Jessica Bellone, Maria Colonna and Danilo Gambacurta
Universe 2024, 10(5), 202; https://doi.org/10.3390/universe10050202 (registering DOI) - 30 Apr 2024
Abstract
The theory of heavy ion double charge exchange (DCE) reactions proceeding by effective rank-2 isotensor interactions is presented. Virtual pion–nucleon charge exchange interactions are investigated as the source for induced isotensor interactions, giving rise to the Majorana DCE (MDCE) reaction mechanism. MDCE is
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The theory of heavy ion double charge exchange (DCE) reactions proceeding by effective rank-2 isotensor interactions is presented. Virtual pion–nucleon charge exchange interactions are investigated as the source for induced isotensor interactions, giving rise to the Majorana DCE (MDCE) reaction mechanism. MDCE is of a generic character, proceeding through pairs of complementary ( ) reactions in the projectile and target nucleus. The dynamics of the elementary processes is discussed, where the excitation of pion–nucleon resonances are of central importance. Investigations of initial and final state ion–ion interactions show that these effects are acting as vertex renormalizations. In closure approximation, well justified by the finite pion mass, the second-order transition matrix elements reduce to pion potentials and effective two-body isotensor DCE interactions, giving rise also to two-body correlations in either of the participating nuclei. Connections to neutrinoless Majorana double beta decay (MDBD) are elucidated at various levels of the dynamics, from the underlying fundamental electro-weak and QCD scales to the physical scales of nuclear MDBD and MDCE physics. It is pointed out that heavy ion MDCE reactions may also proceed by competing electro-weak charge exchange processes, leading to lepton MDCE by electrons, positrons, and neutrinos.
Full article
(This article belongs to the Special Issue Recent Advances in Double Beta Decay Investigations: In Honor of Prof. Sabin Stoica at His 70th Anniversary)
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An Investigation of the Loop Oscillations after a Solar Flare
by
Jun Xu, Zongjun Ning, Dong Li, Fanpeng Shi, Yuxiang Song and Yuzhi Yang
Universe 2024, 10(5), 201; https://doi.org/10.3390/universe10050201 - 29 Apr 2024
Abstract
We study the loop oscillations after a solar flare on 19 January 2023, in the active region N11E40 3196, which is well observed by the SDO/AIA. After tracing the loop position and fitting, we find that the loop oscillations have a period between
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We study the loop oscillations after a solar flare on 19 January 2023, in the active region N11E40 3196, which is well observed by the SDO/AIA. After tracing the loop position and fitting, we find that the loop oscillations have a period between 3 and 9 min at various locations, such as from the leg to the top or from the inner to the outer loop. Their oscillating amplitudes decrease with time. Two loops display the position oscillation simultaneously with their brightness oscillation. After the analysis of the differential emission measure (DEM), we find that two of their loop position oscillations resulted from the plasma density fluctuation. Meanwhile, it is interesting that the brightness of these two position oscillations displays a typical period of about 4 min, similar to that of the position oscillation. This is possible due to both the plasma density and temperature fluctuation there. Our findings provide the physical clues for studying and understanding the mechanism of the loop position and brightness oscillations.
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(This article belongs to the Section Solar System)
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Variation in XCO Factor in N55 Region
by
Qiang Li, Mingyue Li, Li Zhang and Songpeng Pei
Universe 2024, 10(5), 200; https://doi.org/10.3390/universe10050200 - 29 Apr 2024
Abstract
The factor is defined as . It is useful for estimating cloud mass. However, there is only limited research on how the factor
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The factor is defined as . It is useful for estimating cloud mass. However, there is only limited research on how the factor varies within a single cloud. Employing and spectral data, we computed an factor of 3.6 (K km s for luminous gas of the N55 region. Our analysis revealed a V-shaped correlation between the factor and column densities, while the relationship with excitation temperature exhibited obscurity. This suggests that the CO-to- conversion is not consistent on small scale (∼1 pc). Additionally, we found that star formation activity has little influence on the variability in the factor.
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(This article belongs to the Section Stellar Astronomy)
Open AccessReview
The Spectral Condition, Plane Waves, and Harmonic Analysis in de Sitter and Anti-de Sitter Quantum Field Theories
by
Ugo Moschella
Universe 2024, 10(5), 199; https://doi.org/10.3390/universe10050199 - 28 Apr 2024
Abstract
We review the role of the spectral condition as a characteristic of Minkowski, de Sitter, and anti-de Sitter quantum field theories. We also discuss the role of plane waves that are compatible with the relevant analyticity domains linked to the spectral condition(s) and
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We review the role of the spectral condition as a characteristic of Minkowski, de Sitter, and anti-de Sitter quantum field theories. We also discuss the role of plane waves that are compatible with the relevant analyticity domains linked to the spectral condition(s) and discuss harmonic analysis in terms of them.
Full article
(This article belongs to the Special Issue The Friedmann Cosmology: A Century Later)
Open AccessArticle
Higher Time-Derivative Theories from Space–Time Interchanged Integrable Field Theories
by
Andreas Fring, Takano Taira and Bethan Turner
Universe 2024, 10(5), 198; https://doi.org/10.3390/universe10050198 - 28 Apr 2024
Abstract
We compare a relativistic and a nonrelativistic version of Ostrogradsky’s method for higher-time derivative theories extended to scalar field theories and consider as an alternative a multi-field variant. We apply the schemes to space–time rotated modified Korteweg–de Vries systems and, exploiting their integrability,
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We compare a relativistic and a nonrelativistic version of Ostrogradsky’s method for higher-time derivative theories extended to scalar field theories and consider as an alternative a multi-field variant. We apply the schemes to space–time rotated modified Korteweg–de Vries systems and, exploiting their integrability, to Hamiltonian systems built from space–time rotated inverse Legendre transformed higher-order charges of these systems. We derive the equal-time Poisson bracket structures of these theories, establish the integrability of the latter theories by means of the Painlevé test and construct exact analytical period benign solutions in terms of Jacobi elliptic functions to the classical equations of motion. The classical energies of these partially complex solutions are real when they respect a certain modified CPT-symmetry and complex when this symmetry is broken. The higher-order Cauchy and initial-boundary value problem are addressed analytically and numerically. Finally, we provide the explicit quantization of the simplest mKdV system, exhibiting the usual conundrum of having the choice between having to deal with either a theory that includes non-normalizable states or spectra that are unbounded from below. In our non-Hermitian system, the choice is dictated by the correct sign in the decay width.
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(This article belongs to the Section Field Theory)
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Dynamics of Cosmological Scalar Fields Revisited
by
Jan-Willem van Holten
Universe 2024, 10(5), 197; https://doi.org/10.3390/universe10050197 - 28 Apr 2024
Abstract
This paper reviews the dynamics of a single isotropic and homogeneous scalar field in the context of cosmological models. A non-standard approach to the solution of the Einstein–Klein–Gordon equations is described which uses the scalar field as the evolution
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This paper reviews the dynamics of a single isotropic and homogeneous scalar field in the context of cosmological models. A non-standard approach to the solution of the Einstein–Klein–Gordon equations is described which uses the scalar field as the evolution parameter for cosmic dynamics. General conclusions about the qualitative behaviour of the solutions can be drawn, and examples of how to obtain explicit solutions for some cosmological models of interest are given. For arbitrary potentials, analytical results can be obtained from the slow-roll approximation by using a series expansion for the Hubble parameter , from which a quantitative estimate for the number of e-folds of expansion is obtained. This approach is illustrated with the examples of quadratic potentials and hilltop models, with special consideration of Higgs-type potentials. The GUT-scale is shown to come out of such a model quite naturally. Finally, it is discussed how to find scalar potentials giving rise to a predetermined scalar-field behaviour and the associated evolution of the scale factor.
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(This article belongs to the Special Issue The Languages of Physics—A Themed Issue in Honor of Professor Richard Kerner on the Occasion of His 80th Birthday)
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An Investigation on the Distribution of Martian Ionospheric Particles, Based on the Mars Atmosphere and Volatile Evolution (MAVEN)
by
Shican Qiu, Ruichao Li and Willie Soon
Universe 2024, 10(5), 196; https://doi.org/10.3390/universe10050196 - 26 Apr 2024
Abstract
In this paper, we use the key parameters data set of the Neutral Gas and Ion Mass Spectrometer from the Mars Atmosphere and Volatile Evolution (MAVEN) mission. The particle density profiles of electrons, / ,
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In this paper, we use the key parameters data set of the Neutral Gas and Ion Mass Spectrometer from the Mars Atmosphere and Volatile Evolution (MAVEN) mission. The particle density profiles of electrons, / , , , , , and from 90 to 500 km have been deduced by adopting the Chapman modeling methodology. The correlation of the peak density/altitude with the solar zenith angle, the changes in the profile of the Martian ionosphere during solar flares, and the effects of Martian dust storms are analyzed. The results exhibit a positive/negative correlation between the peak density/altitude of the M2 layer and the solar zenith angle. Within the MAVEN observational record available, only three C-Class flares occurred on 26 August 2016, 29 November 2020, and 26 August 2021. The analysis reveals during these solar flare events, the electron density of the M2 layer above 200 km increases obviously. The peak density of M1 increases by 33.4%, 13.2% and 7.4%, while the peak height decreases by 0.1%, 10.2% and 4.4%, respectively. The Martian dust storm causes the peak height of the M2 layer to increase by 19.5 km, and the peak density to decrease by 4.2 × . Our study shows that the Martian ionosphere is similar to the Earth’s, which is of great significance for understanding the planetary ionosphere.
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(This article belongs to the Special Issue Planetary Space Weather)
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Shanghai Tianma Radio Telescope and Its Role in Pulsar Astronomy
by
Zhen Yan, Zhiqiang Shen, Yajun Wu, Rongbing Zhao, Jie Liu, Zhipeng Huang, Rui Wang, Xiaowei Wang, Qinghui Liu, Bin Li, Jinqing Wang, Weiye Zhong, Wu Jiang and Bo Xia
Universe 2024, 10(5), 195; https://doi.org/10.3390/universe10050195 - 26 Apr 2024
Abstract
After two phases of on-site construction and testing (2010–2013 and 2013–2017), the Shanghai Tianma Radio Telescope (TMRT) can work well, with efficiencies better than 50% from 1.3 to 50.0 GHz, mainly benefiting from its low-noise cryogenic receivers and active surface system. Pulsars were
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After two phases of on-site construction and testing (2010–2013 and 2013–2017), the Shanghai Tianma Radio Telescope (TMRT) can work well, with efficiencies better than 50% from 1.3 to 50.0 GHz, mainly benefiting from its low-noise cryogenic receivers and active surface system. Pulsars were chosen as important targets of research at the TMRT because of their important scientific and applied values. To meet the demands of pulsar-related observations, TMRT is equipped with some necessary backends, including a digital backend system (DIBAS) supporting normal pulsar observation modes, a real-time fast-radio-burst-monitoring backend, and baseband backends for very-long-baseline interferometry (VLBI) observations. Utilizing its high sensitivity and simultaneous dual-frequency observation capacity, a sequence of pulsar research endeavors has been undertaken, such as long-term pulsar timing, magnetar monitoring, multi-frequency (or high-frequency) observations, interstellar scintillation, pulsar VLBI, etc. In this paper, we give a short introduction about pulsar observation systems at the TMRT and briefly review the results obtained by these pulsar research projects.
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(This article belongs to the Special Issue Pulsar Astronomy)
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Changes in and Recovery of the Turbulence Properties in the Magnetosheath for Different Solar Wind Streams
by
Liudmila Rakhmanova, Alexander Khokhlachev, Maria Riazantseva, Yuri Yermolaev and Georgy Zastenker
Universe 2024, 10(5), 194; https://doi.org/10.3390/universe10050194 - 26 Apr 2024
Abstract
Solar wind is known to have different properties depending on its origin at the Sun. In addition to the differences in plasma and magnetic field parameters, these streams differ due to the properties of turbulent fluctuations involved in the flow. The present study
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Solar wind is known to have different properties depending on its origin at the Sun. In addition to the differences in plasma and magnetic field parameters, these streams differ due to the properties of turbulent fluctuations involved in the flow. The present study addresses the changes in the turbulence properties in the magnetosheath—the transition region in front of the magnetosphere. This study is based on statistics from the simultaneous measurements of magnetic field fluctuations in the solar wind and in the magnetosheath. Both the dayside and flank magnetosheath regions are focused on to detect the evolution of the turbulent fluctuations during their flow around the magnetosphere. Turbulent cascade is shown to save its properties for fast solar wind streams. Conditions favorable for the preservation of the turbulence properties at the bow shock may correspond to the increased geoefficiency of large-scale solar wind structures.
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(This article belongs to the Section Space Science)
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Cosmological Test of an Ultraviolet Origin of Dark Energy
by
Hans Christiansen, Bence Takács and Steen H. Hansen
Universe 2024, 10(5), 193; https://doi.org/10.3390/universe10050193 - 25 Apr 2024
Abstract
The accelerated expansion of the Universe is impressively well described by a cosmological constant. However, the observed value of the cosmological constant is much smaller than expected based on quantum field theories. Recent efforts to achieve consistency in these theories have proposed a
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The accelerated expansion of the Universe is impressively well described by a cosmological constant. However, the observed value of the cosmological constant is much smaller than expected based on quantum field theories. Recent efforts to achieve consistency in these theories have proposed a relationship between Dark Energy and the most compact objects, such as black holes (BHs). However, experimental tests are very challenging to devise and perform. In this article, we present a testable model with no cosmological constant in which the accelerated expansion can be driven by black holes. The model couples the expansion of the Universe (the Friedmann equation) with the mass function of cosmological halos (using the Press–Schechter formalism). Through the observed link between halo masses and BH masses, one thus gets a coupling between the expansion rate of the Universe and the BHs. We compare the predictions of this simple BH model with SN1a data and find poor agreement with observations. Our method is sufficiently general to allow us to also test a fundamentally different model, also without a cosmological constant, where the accelerated expansion is driven by a new force proportional to the internal velocity dispersion of galaxies. Surprisingly enough, this model cannot be excluded using the SN1a data.
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(This article belongs to the Special Issue The Nature of Dark Energy)
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Non-Commutative Classical and Quantum Fractionary Cosmology: FRW Case
by
J. Socorro, J. Juan Rosales and Leonel Toledo-Sesma
Universe 2024, 10(5), 192; https://doi.org/10.3390/universe10050192 - 25 Apr 2024
Abstract
In this work, we will explore the effects of non-commutativity in fractional classical and quantum schemes using the flat Friedmann–Robertson–Walker (FRW) cosmological model coupled to a scalar field in the K-essence formalism. In previous work, we have obtained the commutative solutions in both
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In this work, we will explore the effects of non-commutativity in fractional classical and quantum schemes using the flat Friedmann–Robertson–Walker (FRW) cosmological model coupled to a scalar field in the K-essence formalism. In previous work, we have obtained the commutative solutions in both regimes in the fractional framework. Here, we introduce non-commutative variables, considering that all minisuperspace variables do not commute, so the symplectic structure was modified. In the quantum regime, the probability density presents a new structure in the scalar field corresponding to the value of the non-commutative parameter, in the sense that this probability density undergoes a shift back to the direction of the scale factor, causing classical evolution to arise earlier than in the commutative world.
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(This article belongs to the Special Issue Recent Advances in Quantum Cosmology)
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Combining Empirical and Physics-Based Models for Solar Wind Prediction
by
Rob Johnson, Soukaina Filali Boubrahimi, Omar Bahri and Shah Muhammad Hamdi
Universe 2024, 10(5), 191; https://doi.org/10.3390/universe10050191 - 24 Apr 2024
Abstract
Solar wind modeling is classified into two main types: empirical models and physics-based models, each designed to forecast solar wind properties in various regions of the heliosphere. Empirical models, which are cost-effective, have demonstrated significant accuracy in predicting solar wind at the L1
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Solar wind modeling is classified into two main types: empirical models and physics-based models, each designed to forecast solar wind properties in various regions of the heliosphere. Empirical models, which are cost-effective, have demonstrated significant accuracy in predicting solar wind at the L1 Lagrange point. On the other hand, physics-based models rely on magnetohydrodynamics (MHD) principles and demand more computational resources. In this research paper, we build upon our recent novel approach that merges empirical and physics-based models. Our recent proposal involves the creation of a new physics-informed neural network that leverages time series data from solar wind predictors to enhance solar wind prediction. This innovative method aims to combine the strengths of both modeling approaches to achieve more accurate and efficient solar wind predictions. In this work, we show the variability of the proposed physics-informed loss across multiple deep learning models. We also study the effect of training the models on different solar cycles on the model’s performance. This work represents the first effort to predict solar wind by integrating deep learning approaches with physics constraints and analyzing the results across three solar cycles. Our findings demonstrate the superiority of our physics-constrained model over other unconstrained deep learning predictive models.
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(This article belongs to the Special Issue Solar and Stellar Activity: Exploring the Cosmic Nexus)
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Betti Functionals as Probes for Cosmic Topology
by
Ralf Aurich and Frank Steiner
Universe 2024, 10(5), 190; https://doi.org/10.3390/universe10050190 - 24 Apr 2024
Abstract
The question of the global topology of the Universe (cosmic topology) is still open. In the CDM concordance model, it is assumed that the space of the Universe possesses the trivial topology of , and thus that the Universe has
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The question of the global topology of the Universe (cosmic topology) is still open. In the CDM concordance model, it is assumed that the space of the Universe possesses the trivial topology of , and thus that the Universe has an infinite volume. As an alternative, in this paper, we study one of the simplest non-trivial topologies given by a cubic 3-torus describing a universe with a finite volume. To probe cosmic topology, we analyze certain structure properties in the cosmic microwave background (CMB) using Betti functionals and the Euler characteristic evaluated on excursions sets, which possess a simple geometrical interpretation. Since the CMB temperature fluctuations are observed on the sphere surrounding the observer, there are only three Betti functionals , . Here, denotes the temperature threshold normalized by the standard deviation of . The analytic approximations of the Gaussian expectations for the Betti functionals and an exact formula for the Euler characteristic are given. It is shown that the amplitudes of and decrease with an increasing volume of the cubic 3-torus universe. Since the computation of the ’s from observational sky maps is hindered due to the presence of masks, we suggest a method that yields lower and upper bounds for them and apply it to four Planck 2018 sky maps. It is found that the ’s of the Planck maps lie between those of the torus universes with side-lengths and in units of the Hubble length and above the infinite CDM case. These results give a further hint that the Universe has a non-trivial topology.
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(This article belongs to the Section Cosmology)
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CP Conservation in the Strong Interactions
by
Wen-Yuan Ai, Björn Garbrecht and Carlos Tamarit
Universe 2024, 10(5), 189; https://doi.org/10.3390/universe10050189 - 23 Apr 2024
Abstract
We discuss matters related to the point that topological quantization in the strong interaction is a consequence of an infinite spacetime volume. Because of the ensuing order of limits, i.e., infinite volume prior to summing over topological sectors, is conserved. Here,
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We discuss matters related to the point that topological quantization in the strong interaction is a consequence of an infinite spacetime volume. Because of the ensuing order of limits, i.e., infinite volume prior to summing over topological sectors, is conserved. Here, we show that this reasoning is consistent with the construction of the path integral from steepest-descent contours. We reply to some objections that aim to support the case for violation in strong interactions that are based on the role of the -odd theta-parameter in three-form effective theories, the correct sampling of all configurations in the dilute instanton gas approximation and the volume dependence of the partition function. We also show that the chiral effective field theory derived from taking the volume to infinity first is in no contradiction with analyses based on partially conserved axial currents.
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(This article belongs to the Special Issue CP Violation and Flavor Physics)
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Two-Pion Bose–Einstein Correlations in Au+Au Collisions at
by
Anna Kraeva
Universe 2024, 10(4), 188; https://doi.org/10.3390/universe10040188 - 20 Apr 2024
Abstract
The correlation femtoscopy technique makes it possible to estimate the geometric dimensions and lifetime of the particle emission region after the collision of ions. Measurements of the emission region characteristics not only at midrapidity but also at backward (forward) rapidity can provide new
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The correlation femtoscopy technique makes it possible to estimate the geometric dimensions and lifetime of the particle emission region after the collision of ions. Measurements of the emission region characteristics not only at midrapidity but also at backward (forward) rapidity can provide new information about the source and make it possible to impose constraints on the heavy-ion collision models. This work is devoted to revealing the dependence of the spatial and temporal parameters of the emission region of identical pions in Au+Au collisions at = 3 GeV from the fixed-target program of the STAR experiment. The extracted femtoscopic radii, , , , , and the correlation strength, , are presented as a function of collision centrality, pair rapidity, and transverse momentum. Physics implications will be discussed.
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(This article belongs to the Special Issue Multiparticle Dynamics)
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Future Perspectives for Gamma-ray Burst Detection from Space
by
Enrico Bozzo, Lorenzo Amati, Wayne Baumgartner, Tzu-Ching Chang, Bertrand Cordier, Nicolas De Angelis, Akihiro Doi, Marco Feroci, Cynthia Froning, Jessica Gaskin, Adam Goldstein, Diego Götz, Jon E. Grove, Sylvain Guiriec, Margarita Hernanz, C. Michelle Hui, Peter Jenke, Daniel Kocevski, Merlin Kole, Chryssa Kouveliotou, Thomas Maccarone, Mark L. McConnell, Hideo Matsuhara, Paul O’Brien, Nicolas Produit, Paul S. Ray, Peter Roming, Andrea Santangelo, Michael Seiffert, Hui Sun, Alexander van der Horst, Peter Veres, Jianyan Wei, Nicholas White, Colleen Wilson-Hodge, Daisuke Yonetoku, Weimin Yuan and Shuang-Nan Zhangadd
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Universe 2024, 10(4), 187; https://doi.org/10.3390/universe10040187 - 19 Apr 2024
Abstract
Since their first discovery in the late 1960s, gamma-ray bursts have attracted an exponentially growing interest from the international community due to their central role in the most highly debated open questions of the modern research of astronomy, astrophysics, cosmology, and fundamental physics.
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Since their first discovery in the late 1960s, gamma-ray bursts have attracted an exponentially growing interest from the international community due to their central role in the most highly debated open questions of the modern research of astronomy, astrophysics, cosmology, and fundamental physics. These range from the intimate nuclear composition of high-density material within the core of ultra-dense neuron stars, to stellar evolution via the collapse of massive stars, the production and propagation of gravitational waves, as well as the exploration of the early universe by unveiling the first stars and galaxies (assessing also their evolution and cosmic re-ionization). GRBs in the past ∼50 years have stimulated the development of cutting-edge technological instruments for observations of high-energy celestial sources from space, leading to the launch and successful operations of many different scientific missions (several of them still in data-taking mode currently). In this review, we provide a brief description of the GRB-dedicated missions from space being designed and developed for the future. The list of these projects, not meant to be exhaustive, shall serve as a reference to interested readers to understand what is likely to come next to lead the further development of GRB research and the associated phenomenology.
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(This article belongs to the Special Issue Recent Advances in Gamma Ray Astrophysics and Future Perspectives)
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The Changes in Multiscale Solar Wind Fluctuations on the Path from the Sun to Earth
by
Igor D. Volodin, Maria O. Riazantseva, Liudmila S. Rakhmanova, Alexander A. Khokhlachev and Yuri I. Yermolaev
Universe 2024, 10(4), 186; https://doi.org/10.3390/universe10040186 - 19 Apr 2024
Abstract
This paper is devoted to the analysis of fluctuations in the solar wind plasma and interplanetary magnetic field parameters observed by Solar Orbiter and WIND spacecraft at different scales ranging from ~103 to 107 km. We consider two long data intervals
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This paper is devoted to the analysis of fluctuations in the solar wind plasma and interplanetary magnetic field parameters observed by Solar Orbiter and WIND spacecraft at different scales ranging from ~103 to 107 km. We consider two long data intervals where the distances between the spacecraft are 0.1 and 0.5 AU, respectively, and they are located close to the Sun–Earth line. Transformation of the fluctuation’s properties on the way from the Sun to Earth is analyzed for different types of solar wind associated with quasi-stationary and transient solar phenomena. The time series of bulk speed are shown to undergo a slight modification, even for large spacecraft separation, while the time series of the interplanetary magnetic field magnitude and components as well as proton density may be transformed even at a relatively short distance. Though the large-scale solar wind structures propagate the distance up to 0.5 AU without significant change, local structures at smaller scales may be modified. The statistical properties of the fluctuations such as relative standard deviation or probability distribution function and its moments remain nearly unchanged at different distances between the two spacecraft and are likely to depend mostly on the type of the solar wind.
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(This article belongs to the Special Issue The Multi-Scale Dynamics of Solar Wind)
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The High Mass Accretion in the Innermost Regions of a Viscously Evolved Protoplanetary Disk
by
Chunjian Liu, Zhen Yao and Yue Quan
Universe 2024, 10(4), 185; https://doi.org/10.3390/universe10040185 - 18 Apr 2024
Abstract
In this paper, we investigate the mass accretion properties in the innermost regions of a viscously evolved protoplanetary disk and try to find some clues to the outburst events. In our newly developed one-dimensional time-dependent disk model based on the diffusion equation for
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In this paper, we investigate the mass accretion properties in the innermost regions of a viscously evolved protoplanetary disk and try to find some clues to the outburst events. In our newly developed one-dimensional time-dependent disk model based on the diffusion equation for surface density, we take into account the following physical effects: the gravitational collapse of the parent molecular cloud core, the irradiation from the central star to the disk, the effect of the photoevaporation mechanism, the viscosity due to the magnetorotational instability (MRI) and the gravitational instability (GI), and the thermal ionization mechanism in the inner regions. We find that the mass accretion rate in the innermost regions is statistically high enough to generate outbursts, although there are regions where the accretion rate is low. Additionally, we find that there is a weak correlation between the high mass accretion rate and the molecular cloud core’s properties (angular velocity and mass ), as well as a strong correlation with the minimum viscosity parameter . In general, there are two regions of outburst, the inner Region I and outer Region II. The outburst of Region I is caused by the MRI mechanism and thermal instability, while neither the MRI, the GI, nor the thermal instability causes the outburst of Region II. Our analysis suggests that the outer Region II is dominated by, or largely related to, the Rosseland mean opacity and the parameter.
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(This article belongs to the Section Planetary Sciences)
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