Universe

15 pages, 3604 KiB

Open AccessArticle

Off-Axis Color Characteristics of Binary Neutron Star Merger Events: Applications for Space Multi-Band Variable Object Monitor and James Webb Space Telescope

by Hongyu Gong, Daming Wei and Zhiping Jin

Universe 2024, 10(10), 403; https://doi.org/10.3390/universe10100403 - 19 Oct 2024

Viewed by 1099

Abstract

With advancements in gravitational wave detection technology, an increasing number of binary neutron star (BNS) merger events are expected to be detected. Due to the narrow opening angle of jet cores, many BNS merger events occur off-axis, resulting in numerous gamma-ray bursts (GRBs) [...] Read more.

With advancements in gravitational wave detection technology, an increasing number of binary neutron star (BNS) merger events are expected to be detected. Due to the narrow opening angle of jet cores, many BNS merger events occur off-axis, resulting in numerous gamma-ray bursts (GRBs) going undetected. Models suggest that kilonovae, which can be observed off-axis, offer more opportunities to be detected in the optical/near-infrared band as electromagnetic counterparts of BNS merger events. In this study, we calculate kilonova emission using a three-dimensional semi-analytical code and model the GRB afterglow emission with the open-source Python package afterglowpy at various inclination angles. Our results show that it is possible to identify the kilonova signal from the observed color evolution of BNS merger events. We also deduce the optimal observing window for SVOM/VT and JWST/NIRCam, which depends on the viewing angle, jet opening angle, and circumburst density. These parameters can be cross-checked with the multi-band afterglow fitting. We suggest that kilonovae are more likely to be identified at larger inclination angles, which can also help determine whether the observed signals without accompanying GRBs originate from BNS mergers. Full article

(This article belongs to the Special Issue Studies in Neutron Stars)

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15 pages, 312 KiB

Open AccessArticle

Spinor–Vector Duality and Mirror Symmetry

by Alon E. Faraggi

Universe 2024, 10(10), 402; https://doi.org/10.3390/universe10100402 - 19 Oct 2024

Viewed by 939

Abstract

Mirror symmetry was first observed in worldsheet string constructions, and was shown to have profound implications in the Effective Field Theory (EFT) limit of string compactifications, and for the properties of Calabi–Yau manifolds. It opened up a new field in pure mathematics, and [...] Read more.

Mirror symmetry was first observed in worldsheet string constructions, and was shown to have profound implications in the Effective Field Theory (EFT) limit of string compactifications, and for the properties of Calabi–Yau manifolds. It opened up a new field in pure mathematics, and was utilised in the area of enumerative geometry. Spinor–Vector Duality (SVD) is an extension of mirror symmetry. This can be readily understood in terms of the moduli of toroidal compactification of the Heterotic String, which includes the metric the antisymmetric tensor field and the Wilson line moduli. In terms of the toroidal moduli, mirror symmetry corresponds to mappings of the internal space moduli, whereas Spinor–Vector Duality corresponds to maps of the Wilson line moduli. In the past few of years, we demonstrated the existence of Spinor–Vector Duality in the effective field theory compactifications of string theories. This was achieved by starting with a worldsheet orbifold construction that exhibited Spinor–Vector Duality and resolving the orbifold singularities, hence generating a smooth, effective field theory limit with an imprint of the Spinor–Vector Duality. Just like mirror symmetry, the Spinor–Vector Duality can be used to study the properties of complex manifolds with vector bundles. Spinor–Vector Duality offers a top-down approach to the “Swampland” program, by exploring the imprint of the symmetries of the ultra-violet complete worldsheet string constructions in the effective field theory limit. The SVD suggests a demarcation line between (2,0) EFTs that possess an ultra-violet complete embedding versus those that do not. Full article

(This article belongs to the Special Issue Particle Physics and Cosmology: A Themed Issue in Honor of Professor Dimitri Nanopoulos)

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14 pages, 1124 KiB

Open AccessArticle

Corrections on the Distribution of Nuclei Due to Neutron Degeneracy and Its Effect on R-Process in Neutron Star Black Hole Mergers

by Rita K. Y. Lau

Universe 2024, 10(10), 401; https://doi.org/10.3390/universe10100401 - 18 Oct 2024

Viewed by 878

Abstract

The r-process is one of the processes that produces heavy elements in the Universe. One of its possible astrophysical sites is the neutron star–black hole (NS-BH) merger. We first show that the neutrons can degenerate before and during the r-process in these mergers. [...] Read more.

The r-process is one of the processes that produces heavy elements in the Universe. One of its possible astrophysical sites is the neutron star–black hole (NS-BH) merger. We first show that the neutrons can degenerate before and during the r-process in these mergers. Previous studies assumed neutrons were non-degenerate and the related rates were calculated under Maxwell–Boltzmann approximations. Hence, we corrected the related rates with neutron degeneracy put in the network code and calculated with the trajectories of NS-BH mergers. We show that there are differences in the nuclei distributions. The heating rates and the temperature at most can be two times larger. The change in heating rates and temperature can affect the light curves of the kilonovae. However, this has little effect on the final abundances. Full article

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24 pages, 774 KiB

Open AccessArticle

An Infinitely Old Universe with Planck Fields Before and After the Big Bang

by Dragana Pilipović

Universe 2024, 10(10), 400; https://doi.org/10.3390/universe10100400 - 17 Oct 2024

Viewed by 2140

Abstract

The Robertson–Walker minimum length (RWML) theory considers stochastically perturbed spacetime to describe an expanding universe governed by geometry and diffusion. We explore the possibility of static, torsionless universe eras with conserved energy density. We find that the RWML theory provides asymptotically static equations [...] Read more.

The Robertson–Walker minimum length (RWML) theory considers stochastically perturbed spacetime to describe an expanding universe governed by geometry and diffusion. We explore the possibility of static, torsionless universe eras with conserved energy density. We find that the RWML theory provides asymptotically static equations of state under positive curvature both far in the past and far into the future, with a Big Bang singularity in between. Full article

(This article belongs to the Special Issue Probing the Early Universe)

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6 pages, 653 KiB

Open AccessArticle

Neutral-Current Single π⁰ Production on Argon

by Marco Martini, Magda Ericson and Guy Chanfray

Universe 2024, 10(10), 399; https://doi.org/10.3390/universe10100399 - 16 Oct 2024

Viewed by 898

Abstract

We interpret the recent MicroBooNE data on neutral-current single

π^{0}

production on argon with the hypothesis that this process occurs via Delta excitation. We calculate the flux-integrated total cross section with our RPA-based model which allows for a simultaneous description of Delta-mediated [...] Read more.

We interpret the recent MicroBooNE data on neutral-current single

π^{0}

production on argon with the hypothesis that this process occurs via Delta excitation. We calculate the flux-integrated total cross section with our RPA-based model which allows for a simultaneous description of Delta-mediated resonant and coherent pion production. We also discuss the ratio between the two exclusive measurements with one proton and zero protons in the final state. Full article

(This article belongs to the Special Issue Neutrino Insights: Peering into the Subatomic Universe)

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18 pages, 766 KiB

Open AccessReview

Time-Delay Interferometry: The Key Technique in Data Pre-Processing Analysis of Space-Based Gravitational Waves

by Pan-Pan Wang and Cheng-Gang Shao

Universe 2024, 10(10), 398; https://doi.org/10.3390/universe10100398 - 16 Oct 2024

Viewed by 1291

Abstract

Space gravitational wave detection primarily focuses on the rich wave sources corresponding to the millihertz frequency band, which provide key information for studying the fundamental physics of cosmology and astrophysics. However, gravitational wave signals are extremely weak, and any noise during the detection [...] Read more.

Space gravitational wave detection primarily focuses on the rich wave sources corresponding to the millihertz frequency band, which provide key information for studying the fundamental physics of cosmology and astrophysics. However, gravitational wave signals are extremely weak, and any noise during the detection process could potentially overwhelm the gravitational wave signals. Therefore, data pre-processing is necessary to suppress the main noise sources. Among the various noise sources, laser phase noise is dominant, approximately seven orders of magnitude larger in strength than typical gravitational wave signals, and requires suppression using time-delay interferometry (TDI) techniques, which involve combining raw data with time delays. This paper will be based on the basic principles of TDI to present methods for obtaining multi-type TDI combinations, including algebraic methods for solving indeterminate equations and geometric methods for symbolic search. Furthermore, the applicability of TDI under actual operating conditions will be considered, such as the arm locking in conjunction with the TDI algorithm. Finally, the sensitivity functions for different types of TDI combinations will be provided, which can be used to evaluate the signal-to-noise ratio (SNRs) of different TDI combinations. Full article

(This article belongs to the Collection Gravitational Waves as a New Probe for Astronomy and Fundamental Physics)

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28 pages, 2471 KiB

Open AccessArticle

Universal Properties of the Evolution of the Universe in Modified Loop Quantum Cosmology

by Jamal Saeed, Rui Pan, Christian Brown, Gerald Cleaver and Anzhong Wang

Universe 2024, 10(10), 397; https://doi.org/10.3390/universe10100397 - 15 Oct 2024

Cited by 4 | Viewed by 1140

Abstract

In this paper, we systematically study the evolution of the Universe within the framework of a modified loop quantum cosmological model (mLQC-I) using various inflationary potentials, including chaotic, Starobinsky, generalized Starobinsky, polynomials of the first and second kinds, generalized T-models and natural inflation. [...] Read more.

In this paper, we systematically study the evolution of the Universe within the framework of a modified loop quantum cosmological model (mLQC-I) using various inflationary potentials, including chaotic, Starobinsky, generalized Starobinsky, polynomials of the first and second kinds, generalized T-models and natural inflation. In all these models, the big bang singularity is replaced by a quantum bounce, and the evolution of the Universe, both before and after the bounce, is universal and weakly dependent on the inflationary potentials, as long as the evolution is dominated by the kinetic energy of the inflaton at the bounce. In particular, the pre-bounce evolution can be universally divided into three different phases: pre-bouncing, pre-transition, and pre-de Sitter. The pre-bouncing phase occurs immediately before the quantum bounce, during which the evolution of the Universe is dominated by the kinetic energy of the inflaton. Thus, the equation of state of the inflaton is about one,

w (ϕ) ≃ 1

. Soon, the inflation potential takes over, so

w (ϕ)

rapidly falls from one to negative one. This pre-transition phase is very short and quickly turns into the pre-de Sitter phase, whereby the effective cosmological constant of Planck size takes over and dominates the rest of the contracting phase. Throughout the entire pre-bounce regime, the evolution of both the expansion factor and the inflaton can be approximated by universal analytical solutions, independent of the specific inflation potentials. Full article

(This article belongs to the Special Issue Loop Quantum Gravity and Non-Perturbative Approaches to Quantum Cosmology, Second Edition)

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22 pages, 332 KiB

Open AccessTutorial

Introduction to Bell’s Inequality in Quantum Mechanics

by Marcelo Santos Guimaraes, Itzhak Roditi and Silvio Paolo Sorella

Universe 2024, 10(10), 396; https://doi.org/10.3390/universe10100396 - 15 Oct 2024

Cited by 4 | Viewed by 1348

Abstract

A pedagogical introduction to Bell’s inequality in Quantum Mechanics is presented. Several examples, ranging from spin

1 / 2

to coherent and squeezed states are worked out. The generalization to Mermin’s inequalities and to GHZ states is also outlined. Full article

(This article belongs to the Section Foundations of Quantum Mechanics and Quantum Gravity)

26 pages, 52439 KiB

Open AccessArticle

Photometry and Models of Seven Main-Belt Asteroids

by Jun Tian, Haibin Zhao, Bin Li, Yongxiong Zhang, Jian Chen, Leonid Elenin and Xiaoping Lu

Universe 2024, 10(10), 395; https://doi.org/10.3390/universe10100395 - 14 Oct 2024

Viewed by 1411

Abstract

The China Near-Earth Object Survey Telescope (CNEOST) conducted four photometric surveys from 2015 to 2018 using image processing and aperture photometry techniques to obtain extensive light curve data on asteroids. The second-order Fourier series method was selected for its efficiency in determining the [...] Read more.

The China Near-Earth Object Survey Telescope (CNEOST) conducted four photometric surveys from 2015 to 2018 using image processing and aperture photometry techniques to obtain extensive light curve data on asteroids. The second-order Fourier series method was selected for its efficiency in determining the rotation periods of the observed asteroids. Our study successfully derived rotation periods for 892 asteroids, with 648 of those matching values recorded in the LCDB (for asteroids with U > 2). To enhance the reliability of the derived spin parameters and shape models, we also amassed a comprehensive collection of published light curve data supplemented by additional photometric observations on a targeted subset of asteroids conducted using multiple telescopes between 2021 and 2022. Through the application of convex inversion techniques, we successfully derived spin parameters and shape models for seven main-belt asteroids (MBAs): (2233) Kuznetsov, (2294) Andronikov, (2253) Espinette, (4796) Lewis, (1563) Noel, (2912) Lapalma, and (5150) Fellini. Our thorough analysis identified two credible orientations for the rotational poles of these MBAs, shedding light on the prevalent issue of “ambiguity in pole direction” that often accompanies photometric inversion processes. CNEOST continues its observational endeavors, and future collected data combined with other independent photometric measurements will facilitate further inversion to better constrain the spin parameters and yield more refined shape models. Full article

(This article belongs to the Special Issue Space Missions to Small Bodies: Results and Future Activities)

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15 pages, 15095 KiB

Open AccessArticle

Galaxy Classification Using EWGC

by Yunyan Nie, Zhiren Pan, Jianwei Zhou, Bo Qiu, A-Li Luo, Chong Luo and Xiaodong Luan

Universe 2024, 10(10), 394; https://doi.org/10.3390/universe10100394 - 12 Oct 2024

Viewed by 905

Abstract

The Enhanced Wide-field Galaxy Classification Network (EWGC) is a novel architecture designed to classify spiral and elliptical galaxies using Wide-field Infrared Survey Explorer (WISE) images. The EWGC achieves an impressive classification accuracy of 90.02%, significantly outperforming the previously developed WGC network and underscoring [...] Read more.

The Enhanced Wide-field Galaxy Classification Network (EWGC) is a novel architecture designed to classify spiral and elliptical galaxies using Wide-field Infrared Survey Explorer (WISE) images. The EWGC achieves an impressive classification accuracy of 90.02%, significantly outperforming the previously developed WGC network and underscoring its superior performance in galaxy morphology classification. Remarkably, the network demonstrates a consistent accuracy of 90.02% when processing both multi-target and single-target images. Such robustness indicates the EWGC’s versatility and potential for various applications in galaxy classification tasks. Full article

(This article belongs to the Section Astroinformatics and Astrostatistics)

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14 pages, 4193 KiB

Open AccessArticle

Decoding Quantum Gravity Information with Black Hole Accretion Disk

by Lei You, Yu-Hang Feng, Rui-Bo Wang, Xian-Ru Hu and Jian-Bo Deng

Universe 2024, 10(10), 393; https://doi.org/10.3390/universe10100393 - 11 Oct 2024

Cited by 6 | Viewed by 1128

Abstract

Integrating loop quantum gravity with classical gravitational collapse models offers an effective solution to the black hole singularity problem and predicts the formation of a white hole in the later stages of collapse. Furthermore, the quantum extension of Kruskal spacetime indicates that white [...] Read more.

Integrating loop quantum gravity with classical gravitational collapse models offers an effective solution to the black hole singularity problem and predicts the formation of a white hole in the later stages of collapse. Furthermore, the quantum extension of Kruskal spacetime indicates that white holes may convey information about earlier companion black holes. Photons emitted from the accretion disks of these companion black holes enter the black hole, traverse the highly quantum region, and then re-emerge from white holes in our universe. This process enables us to observe images of the companion black holes’ accretion disks, providing insights into quantum gravity. In our study, we successfully obtained these accretion disk images. Our results indicate that these accretion disk images are confined within a circle with a radius equal to the critical impact parameter, while traditional accretion disk images are typically located outside this circle. As the observational angle increases, the accretion disk images transition from a ring shape to a shell-like shape. Furthermore, the positional and width characteristics of these accretion disk images are opposite to those of traditional accretion disk images. These findings provide valuable references for astronomical observations aimed at validating the investigated quantum gravity model. Full article

(This article belongs to the Special Issue Loop Quantum Gravity and Non-Perturbative Approaches to Quantum Cosmology, Second Edition)

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35 pages, 7319 KiB

Open AccessArticle

Searching for Hadronic Signatures in the Time Domain of Blazar Emission: The Case of Mrk 501

by Margaritis Chatzis, Stamatios I. Stathopoulos, Maria Petropoulou and Georgios Vasilopoulos

Universe 2024, 10(10), 392; https://doi.org/10.3390/universe10100392 - 10 Oct 2024

Cited by 1 | Viewed by 967

Abstract

Blazars—a subclass of active galaxies—are intrinsically time-variable broadband sources of electromagnetic radiation. In this contribution, we explored relativistic proton (hadronic) signatures in the time domain blazar emission and searched for those parameter combinations that unveil their presence during flaring epochs. We generated time [...] Read more.

Blazars—a subclass of active galaxies—are intrinsically time-variable broadband sources of electromagnetic radiation. In this contribution, we explored relativistic proton (hadronic) signatures in the time domain blazar emission and searched for those parameter combinations that unveil their presence during flaring epochs. We generated time series for key model parameters, like magnetic field strength and the power-law index of radiating particles, which were motivated from a simulated time series with statistical properties describing the observed GeV gamma-ray flux. We chose the TeV blazar Mrk 501 as our test case, as it had been the study ground for extensive investigations during individual flaring events. Using the code LeHaMoC, we computed the electromagnetic and neutrino emissions for a period of several years that contained several flares of interest. We show that for both of those particle distributions the power-law index variations that were tied to moderate changes in the magnetic field strength of the emitting region might naturally lead to hard X-ray flares with very-high-energy

γ

-ray counterparts. We found spectral differences measurable by the Cherenkov Telescope Array Observatory at sub-TeV energies, and we computed the neutrino fluence over 14.5 years. The latter predicted ∼0.2 muon and anti-muon neutrinos, consistent with the non-detection of high-energy neutrinos from Mrk 501. Full article

(This article belongs to the Special Issue Blazar Bursts: Theory and Observation)

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18 pages, 14984 KiB

Open AccessEditor’s ChoiceArticle

The Mother’s Day Solar Storm of 11 May 2024 and Its Effect on Earth’s Radiation Belts

by Viviane Pierrard, Alexandre Winant, Edith Botek and Maximilien Péters de Bonhome

Universe 2024, 10(10), 391; https://doi.org/10.3390/universe10100391 - 10 Oct 2024

Cited by 10 | Viewed by 2481

Abstract

The month of May 2024 was characterized by solar energetic particles events directed towards the Earth, especially the big event causing a strong terrestrial geomagnetic storm during the night from 10 to 11 May 2024, with auroras observed everywhere in Europe. This was [...] Read more.

The month of May 2024 was characterized by solar energetic particles events directed towards the Earth, especially the big event causing a strong terrestrial geomagnetic storm during the night from 10 to 11 May 2024, with auroras observed everywhere in Europe. This was the strongest storm for the last 20 years with a Disturbed Storm Time index Dst < −400 nT. In the present work, we show with observations of GOES, PROBA-V/EPT and MetOP/MEPED that this exceptional event was associated with the injection of energetic protons in the proton radiation belt, with important consequences for the South part of the South Atlantic Anomaly (SAA). In addition, the geomagnetic storm caused by the solar eruption has had tremendous impacts on the electron radiation belts. Indeed, we show that for 0.3 to 1 MeV electrons, the storm led to a long lasting four belts configuration which was not observed before with EPT launched in 2013, until a smaller geomagnetic storm took place at the end of June 2024. Moreover, for the first time since its launch, observations of the EPT show that ultra-relativistic electrons with

E > 2

MeV have been injected into the inner belt down to McIlwain parameter L = 2.4, violating the impenetrable barrier previously estimated to be located at L = 2.8. Full article

(This article belongs to the Section Space Science)

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Graphical abstract

17 pages, 505 KiB

Open AccessEditor’s ChoiceArticle

Prigogine’s Second Law and Determination of the EUP and GUP Parameters in Small Black Hole Thermodynamics

by Giorgio Sonnino

Universe 2024, 10(10), 390; https://doi.org/10.3390/universe10100390 - 7 Oct 2024

Cited by 3 | Viewed by 1334

Abstract

In 1974, Stephen Hawking made the groundbreaking discovery that black holes emit thermal radiation, characterized by a specific temperature now known as the Hawking temperature. While his original derivation is intricate, retrieving the exact expressions for black hole temperature and entropy in a [...] Read more.

In 1974, Stephen Hawking made the groundbreaking discovery that black holes emit thermal radiation, characterized by a specific temperature now known as the Hawking temperature. While his original derivation is intricate, retrieving the exact expressions for black hole temperature and entropy in a simpler, more intuitive way without losing the core physical principles behind Hawking’s assumptions is possible. This is obtained by employing the Heisenberg Uncertainty Principle, which is known to be connected to thenvacuum fluctuation. This exercise allows us to easily perform more complex calculations involving the effects of quantum gravity. This work aims to answer the following question: Is it possible to reconcile Prigogine’s second law of thermodynamics for open systems and the second law of black hole dynamics with Hawking radiation? Due to quantum gravity effects, the Heisenberg Uncertainty Principle has been extended to the Generalized Uncertainty Principle (GUP) and successively to the Extended Uncertainty Principle (EUP). The expression for the EUP parameter is obtained by conjecturing that Prigogine’s second law of thermodynamics and the second law of black holes are not violated by the Hawking thermal radiation mechanism. The modified expression for the entropy of a Schwarzschild black hole is also derived. Full article

(This article belongs to the Section Cosmology)

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19 pages, 349 KiB

Open AccessEditor’s ChoiceReview

Spinning Systems in Quantum Mechanics: An Overview and New Trends

by E. Brito, Júlio E. Brandão and Márcio M. Cunha

Universe 2024, 10(10), 389; https://doi.org/10.3390/universe10100389 - 4 Oct 2024

Cited by 3 | Viewed by 1549

Abstract

The study of spinning systems plays a question of interest in several research branches in physics. It allows the understanding of simple classical mechanical systems but also provides us with tools to investigate a wide range of phenomena, from condensed matter physics to [...] Read more.

The study of spinning systems plays a question of interest in several research branches in physics. It allows the understanding of simple classical mechanical systems but also provides us with tools to investigate a wide range of phenomena, from condensed matter physics to gravitation and cosmology. In this contribution, we review some remarkable theoretical aspects involving the description of spinning quantum systems. We explore the nonrelativistic and relativistic domains and their respective applications in fields such as graphene physics and topological defects in gravitation. Full article

(This article belongs to the Section Foundations of Quantum Mechanics and Quantum Gravity)

10 pages, 289 KiB

Open AccessArticle

Universes Emerging from Nothing and Disappearing into Nothing as an Endless Cosmological Process

by Leonid Marochnik

Universe 2024, 10(10), 388; https://doi.org/10.3390/universe10100388 - 3 Oct 2024

Viewed by 1139

Abstract

The equation of state of quantum fluctuations of the gravitational field of the universe depends on

H^{4}

, where

H

is the Hubble constant. This means that it is invariant with respect to the Wick rotation, i.e., the transition from Lorentzian space-time [...] Read more.

The equation of state of quantum fluctuations of the gravitational field of the universe depends on

H^{4}

, where

H

is the Hubble constant. This means that it is invariant with respect to the Wick rotation, i.e., the transition from Lorentzian space-time to Euclidean space-time and vice versa. It is shown that the quantum birth of universes from Euclidean space-time, i.e., from nothing, and their quantum disappearance to nothing (return to Euclidean space-time) by the time the density of the matter filling the universe becomes negligible could be a likely cosmological scenario. On an infinite time axis, this is an endless process of birth and death of universes appearing and disappearing and replacing each other. Within this scenario, our current universe is going to disappear into nothing at

z \leq - 0.68

, i.e., after 18.37 billion years, and the lifetime of our universe and similar universes is about 32 billion years. Full article

(This article belongs to the Special Issue Cosmological Models of the Universe)

17 pages, 2072 KiB

Open AccessArticle

Exploring Neutrino Masses (g − 2)_μ,e in Type I+II Seesaw in L_e–L_α-Gauge Extended Model

by Papia Panda, Priya Mishra, Mitesh Kumar Behera, Shivaramakrishna Singirala and Rukmani Mohanta

Universe 2024, 10(10), 387; https://doi.org/10.3390/universe10100387 - 2 Oct 2024

Cited by 1 | Viewed by 899

Abstract

This paper aims to explore the implications of

U {(1)}_{L_{e} - L_{α}}

gauge symmetries, where

α = τ, μ

, in the neutrino sector through type-(I+II) seesaw mechanisms. To achieve such a hybrid framework, we include a [...] Read more.

This paper aims to explore the implications of

U {(1)}_{L_{e} - L_{α}}

gauge symmetries, where

α = τ, μ

, in the neutrino sector through type-(I+II) seesaw mechanisms. To achieve such a hybrid framework, we include a scalar triplet and three right-handed neutrinos. The model can successfully account for the active neutrino masses, mixing angles, mass squared differences, and the CP-violating phase within the

3 σ

bounds of NuFit v5.2 neutrino oscillation data. The presence of a new gauge boson at the MeV scale provides an explanation for the muon and electron

(g - 2)

within the confines of their experimental limits. Furthermore, we scrutinize the proposed models in the context of upcoming long-baseline neutrino experiments such as DUNE, P2SO, T2HK, and T2HKK. The findings reveal that P2SO and T2HK have the ability to probe both models in their

5 σ

-allowed oscillation parameter region, whereas DUNE and T2HKK can conclusively test only the model with

U {(1)}_{L_{e} - L_{μ}}

-symmetry within the

5 σ

parameter space if the true values of the oscillation parameters remain consistent with NuFit v5.2. Full article

(This article belongs to the Special Issue Current Trends in Neutrino Oscillation Physics: A Phenomenological and Experimental Perspective)

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10 pages, 252 KiB

Open AccessArticle

On Planetary Orbits, Ungravity and Entropic Gravity

by Gemma Pérez-Cuéllar and Miguel Sabido

Universe 2024, 10(10), 386; https://doi.org/10.3390/universe10100386 - 1 Oct 2024

Viewed by 866

Abstract

In previous works, entropic gravity and ungravity have been considered as possible solutions to the dark energy and dark matter problems. To test the viability of these models, modifications to planetary orbits are calculated for ungravity and different models of entropic gravity. Using [...] Read more.

In previous works, entropic gravity and ungravity have been considered as possible solutions to the dark energy and dark matter problems. To test the viability of these models, modifications to planetary orbits are calculated for ungravity and different models of entropic gravity. Using the gravitational sector of unparticles, an equation for the contribution to the effect of orbital precession is obtained. We conclude that the estimated values for the ungravity parameters from planetary orbits are inconsistent with the values needed for the cosmological constant. The same ideas are explored for entropic gravity arising from a modified entropy–area relationship. Full article

(This article belongs to the Section Gravitation)

32 pages, 1586 KiB

Open AccessArticle

The Magellanic Clouds Are Very Rare in the IllustrisTNG Simulations

by Moritz Haslbauer, Indranil Banik, Pavel Kroupa, Hongsheng Zhao and Elena Asencio

Universe 2024, 10(10), 385; https://doi.org/10.3390/universe10100385 - 1 Oct 2024

Cited by 3 | Viewed by 1060

Abstract

The Large and Small Magellanic Clouds (LMC and SMC) form the closest interacting galactic system to the Milky Way, therewith providing a laboratory to test cosmological models in the local Universe. We quantify the likelihood for the Magellanic Clouds (MCs) to be observed [...] Read more.

The Large and Small Magellanic Clouds (LMC and SMC) form the closest interacting galactic system to the Milky Way, therewith providing a laboratory to test cosmological models in the local Universe. We quantify the likelihood for the Magellanic Clouds (MCs) to be observed within the

Λ

CDM model using hydrodynamical simulations of the IllustrisTNG project. The orbits of the MCs are constrained by proper motion measurements taken by the Hubble Space Telescope and Gaia. The MCs have a mutual separation of

d_{MCs} = 24.5 kpc

and a relative velocity of

v_{MCs} = 90.8 km s^{- 1}

, implying a specific phase-space density of

f_{MCs, obs} \equiv {(d_{MCs} \cdot v_{MCs})}^{- 3} = 9.10 \times 10^{- 11} {km}^{- 3} s^{3} {kpc}^{- 3}

. We select analogues to the MCs based on their stellar masses and distances in MW-like halos. None of the selected LMC analogues have a higher total mass and lower Galactocentric distance than the LMC, resulting in >3.75

σ

tension. We also find that the

f_{MCs}

distribution in the highest resolution TNG50 simulation is in

3.95 σ

tension with observations. Thus, a hierarchical clustering of two massive satellites like the MCs in a narrow phase-space volume is unlikely in

Λ

CDM, presumably because of short merger timescales due to dynamical friction between the overlapping dark matter halos. We show that group infall led by an LMC analogue cannot populate the Galactic disc of satellites (DoS), implying that the DoS and the MCs formed in physically unrelated ways in

Λ

CDM. Since the

20^{\circ}

alignment of the LMC and DoS orbital poles has a likelihood of

P = 0.030

(

2.17 σ

), adding this

χ^{2}

to that of

f_{MCs}

gives a combined likelihood of

P = 3.90 \times 10^{- 5}

(

4.11 σ

). Full article

(This article belongs to the Special Issue Universe: Feature Papers 2024—"Galaxies and Clusters")

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19 pages, 425 KiB

Open AccessArticle

Finite Time Path Field Theory Perturbative Methods for Local Quantum Spin Chain Quenches

by Domagoj Kuić, Alemka Knapp and Diana Šaponja-Milutinović

Universe 2024, 10(10), 384; https://doi.org/10.3390/universe10100384 - 30 Sep 2024

Viewed by 968

Abstract

We discuss local magnetic field quenches using perturbative methods of finite time path field theory (FTPFT) in the following spin chains: Ising and XY in a transverse magnetic field. Their common characteristics are: (i) they are integrable via mapping to a second quantized [...] Read more.

We discuss local magnetic field quenches using perturbative methods of finite time path field theory (FTPFT) in the following spin chains: Ising and XY in a transverse magnetic field. Their common characteristics are: (i) they are integrable via mapping to a second quantized noninteracting fermion problem; and (ii) when the ground state is nondegenerate (true for finite chains except in special cases), it can be represented as a vacuum of Bogoliubov fermions. By switching on a local magnetic field perturbation at finite time, the problem becomes nonintegrable and must be approached via numeric or perturbative methods. Using the formalism of FTPFT based on Wigner transforms (WTs) of projected functions, we show how to: (i) calculate the basic “bubble” diagram in the Loschmidt echo (LE) of a quenched chain to any order in the perturbation; and (ii) resum the generalized Schwinger–Dyson equation for the fermion two-point retarded functions in the “bubble” diagram, hence achieving the resummation of perturbative expansion of LE for a wide range of perturbation strengths under certain analyticity assumptions. Limitations of the assumptions and possible generalizations beyond it and also for other spin chains are further discussed. Full article

(This article belongs to the Special Issue Universe: Feature Papers 2023—Field Theory)

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32 pages, 8140 KiB

Open AccessArticle

Constraining the Initial Mass Function via Stellar Transients

by Francesco Gabrielli, Lumen Boco, Giancarlo Ghirlanda, Om Sharan Salafia, Ruben Salvaterra, Mario Spera and Andrea Lapi

Universe 2024, 10(10), 383; https://doi.org/10.3390/universe10100383 - 29 Sep 2024

Cited by 1 | Viewed by 2363

Abstract

The stellar initial mass function (IMF) represents a fundamental quantity in astrophysics and cosmology describing the mass distribution of stars from low mass all the way up to massive and very massive stars. It is intimately linked to a wide variety of topics, [...] Read more.

The stellar initial mass function (IMF) represents a fundamental quantity in astrophysics and cosmology describing the mass distribution of stars from low mass all the way up to massive and very massive stars. It is intimately linked to a wide variety of topics, including stellar and binary evolution, galaxy evolution, chemical enrichment, and cosmological reionization. Nonetheless, the IMF still remains highly uncertain. In this work, we aim to determine the IMF with a novel approach based on the observed rates of transients of stellar origin. We parametrize the IMF with a simple but flexible Larson shape, and insert it into a parametric model for the cosmic UV luminosity density, local stellar mass density, type Ia supernova (SN Ia), core-collapse supernova (CCSN), and long gamma-ray burst (LGRB) rates as a function of redshift. We constrain our free parameters by matching the model predictions to a set of empirical determinations for the corresponding quantities via a Bayesian Markov Chain Monte Carlo method. Remarkably, we are able to provide an independent IMF determination with a characteristic mass

m_{c} = 0 . 10_{- 0.08}^{+ 0.24} M_{⊙}

and high-mass slope

ξ = - 2 . 53_{- 0.27}^{+ 0.24}

that are in accordance with the widely used IMF parameterizations (e.g., Salpeter, Kroupa, Chabrier). Moreover, the adoption of an up-to-date recipe for the cosmic metallicity evolution allows us to constrain the maximum metallicity of LGRB progenitors to

Z_{m a x} = 0 . 12_{- 0.05}^{+ 0.29} Z_{⊙}

. We also find which progenitor fraction actually leads to SN Ia or LGRB emission (e.g., due to binary interaction or jet-launching conditions), put constraints on the CCSN and LGRB progenitor mass ranges, and test the IMF universality. These results show the potential of this kind of approach for studying the IMF, its putative evolution with the galactic environment and cosmic history, and the properties of SN Ia, CCSN, and LGRB progenitors, especially considering the wealth of data incoming in the future. Full article

(This article belongs to the Special Issue Universe: Feature Papers 2024 – Compact Objects)

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12 pages, 337 KiB

Open AccessArticle

The Effective Baryon–Baryon Potential with Configuration Mixing in Quark Models

by Xinmei Zhu, Hongxia Huang and Jialun Ping

Universe 2024, 10(10), 382; https://doi.org/10.3390/universe10100382 - 29 Sep 2024

Viewed by 795

Abstract

The effective baryon–baryon potential can be derived in the framework of the quark model. The configurations with different quark spatial distributions are mixed naturally when two baryons get close. The effect of configuration mixing in the chiral quark model (ChQM) is studied by [...] Read more.

The effective baryon–baryon potential can be derived in the framework of the quark model. The configurations with different quark spatial distributions are mixed naturally when two baryons get close. The effect of configuration mixing in the chiral quark model (ChQM) is studied by calculating the effective potential between two non-strange baryons in the channels

I J = 01, 10

and 03. For comparison, the results of the color screening model (CSM) are also presented. Generally, configuration mixing will lower the potential when the separation between two baryons is small, and its effect will be ignorable when the separation becomes large. Due to the screened color confinement, the effect of configuration mixing is rather large, which leads to stronger intermediate-range attraction in the CSM, while the effect of configuration mixing is small in the ChQM due to the quadratic confinement and

σ

-meson exchange, which is responsible for the intermediate-range attraction. Full article

(This article belongs to the Section High Energy Nuclear and Particle Physics)

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13 pages, 2344 KiB

Open AccessArticle

Automated High-Precision Recognition of Solar Filaments Based on an Improved U²-Net

by Wendong Jiang and Zhengyang Li

Universe 2024, 10(10), 381; https://doi.org/10.3390/universe10100381 - 29 Sep 2024

Cited by 1 | Viewed by 1102

Abstract

Solar filaments are a significant solar activity phenomenon, typically observed in full-disk solar observations in the H-alpha band. They are closely associated with the magnetic fields of solar active regions, solar flare eruptions, and coronal mass ejections. With the increasing volume of observational [...] Read more.

Solar filaments are a significant solar activity phenomenon, typically observed in full-disk solar observations in the H-alpha band. They are closely associated with the magnetic fields of solar active regions, solar flare eruptions, and coronal mass ejections. With the increasing volume of observational data, the automated high-precision recognition of solar filaments using deep learning is crucial. In this study, we processed full-disk H-alpha solar images captured by the Chinese H-alpha Solar Explorer in 2023 to generate labels for solar filaments. The preprocessing steps included limb-darkening removal, grayscale transformation, K-means clustering, particle erosion, multiple closing operations, and hole filling. The dataset containing solar filament labels is constructed for deep learning. We developed the Attention U²-Net neural network for deep learning on the solar dataset by introducing an attention mechanism into U²-Net. In the results, Attention U²-Net achieved an average Accuracy of 0.9987, an average Precision of 0.8221, an average Recall of 0.8469, an average IoU of 0.7139, and an average F1-score of 0.8323 on the solar filament test set, showing significant improvements compared to other U-net variants. Full article

(This article belongs to the Special Issue Measurements, Observations and Theoretical Studies on the Solar Magnetic Field—Celebrating the 40th Anniversary of the Huairou Solar Observing Station)

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