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Universe, Volume 9, Issue 8 (August 2023) – 32 articles

Cover Story (view full-size image): De Sitter black holes and other non-perturbative configurations can be used to probe the holographic degrees of freedom of de Sitter space. For small black holes, evidence was first provided in the seminal work of Banks, Fiol, and Morrise and follow-ups by Banks and Fischler, showing that dS is described by a form of matrix theory. For large black holes, the evidence provided here is new: Gravitational calculations and matrix theory calculations of the rates of exponentially rare fluctuations match one another in surprising detail. The occurrences of Nariai geometry and the “inside-out” transition are particularly interesting examples, and will be explained in this paper. View this paper
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27 pages, 397 KiB  
Article
Novel Free Differential Algebras for Supergravity
by Pietro Antonio Grassi
Universe 2023, 9(8), 376; https://doi.org/10.3390/universe9080376 - 21 Aug 2023
Viewed by 684
Abstract
We develop the theory of Free Integro-Differential Algebras (FIDA) extending the powerful technique of Free Differential Algebras constructed by D. Sullivan. We extend the analysis beyond the superforms to integral- and pseudo-forms used in supergeometry. It is shown that there are novel structures [...] Read more.
We develop the theory of Free Integro-Differential Algebras (FIDA) extending the powerful technique of Free Differential Algebras constructed by D. Sullivan. We extend the analysis beyond the superforms to integral- and pseudo-forms used in supergeometry. It is shown that there are novel structures that might open the road to a deeper understanding of the geometry of supergravity. We apply the technique to some models as an illustration and we provide a complete analysis for D = 11 supergravity. There, it is shown how the Hodge star operator for supermanifolds can be used to analyze the set of cocycles and to build the corresponding FIDA. A new integral form emerges which plays the role of the truly dual to 4-form F(4) and we propose a new variational principle on supermanifolds. Full article
(This article belongs to the Section Mathematical Physics)
10 pages, 253 KiB  
Review
Solving the Mystery of Fast Radio Bursts: A Detective’s Approach
by Bing Zhang
Universe 2023, 9(8), 375; https://doi.org/10.3390/universe9080375 - 18 Aug 2023
Cited by 4 | Viewed by 958
Abstract
Fast radio bursts (FRBs) are still a mystery in contemporary astrophysics. Unlike many other astronomical objects whose basic physical mechanism is already identified and the research on which focuses mainly on refining details, FRBs are still largely unknown regarding their source(s) and radiation [...] Read more.
Fast radio bursts (FRBs) are still a mystery in contemporary astrophysics. Unlike many other astronomical objects whose basic physical mechanism is already identified and the research on which focuses mainly on refining details, FRBs are still largely unknown regarding their source(s) and radiation mechanism(s). To make progress in the field, a “top-down” or “detective’s approach” is desirable. I will summarize how some key observational facts have narrowed down the options to interpret FRBs and show that at least some FRBs are produced from the magnetospheres of highly magnetized neutron stars (or magnetars). I will also argue that the current data seem to favor a type of coherent inverse Compton scattering process by relativistic particle bunches off a low-frequency wave propagating in the magnetosphere. This brief contribution is a shorter version of an extended review to be published in Reviews of Modern Physics, and it was written as a tribute to the 80th anniversary of Remo Ruffini. Full article
(This article belongs to the Special Issue Remo Ruffini Festschrift)
14 pages, 2753 KiB  
Article
Solar-Cycle Variations of Forbidden Energetic Electrons Enhancements
by Alla V. Suvorova
Universe 2023, 9(8), 374; https://doi.org/10.3390/universe9080374 - 17 Aug 2023
Viewed by 762
Abstract
Intense fluxes of electrons from the Earth’s radiation belt (ERB) with energies of tens and hundreds of keV can penetrate to low altitudes at low latitudes outside the South Atlantic Anomaly. This region is known as a forbidden zone of quasi-trapped energetic particles. [...] Read more.
Intense fluxes of electrons from the Earth’s radiation belt (ERB) with energies of tens and hundreds of keV can penetrate to low altitudes at low latitudes outside the South Atlantic Anomaly. This region is known as a forbidden zone of quasi-trapped energetic particles. Flux enhancements of energetic electrons in the forbidden zone, so-called forbidden energetic electrons (FEE), produce significant ionization effects in the upper atmosphere at low latitudes. In this work, solar-cycle variations of the FEE enhancements with energy > 30 keV were analyzed over a 25-year period using a database of low-orbit satellites of the NOAA/POES and MetOp series. We found the highest correlations of the annual occurrence of FEE with the F10.7 solar activity index (−0.87) and the Alfven Mach number of the upstream solar wind (0.76). Using multiparameter regression analysis, a power expression was obtained with those parameters as well as with plasma beta and the interplanetary magnetic field strength with a total correlation coefficient of 0.94. The role of the conductivity of the high-latitude ionosphere in the mechanism of the penetration of ERB electrons into the forbidden zone is discussed. Full article
(This article belongs to the Section Space Science)
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14 pages, 417 KiB  
Article
Quantum Big Bounce of the Isotropic Universe Using Relational Time
by Eleonora Giovannetti, Fabio Maione and Giovanni Montani
Universe 2023, 9(8), 373; https://doi.org/10.3390/universe9080373 - 16 Aug 2023
Cited by 5 | Viewed by 795
Abstract
We analyze the canonical quantum dynamics of the isotropic Universe with a metric approach by adopting a self-interacting scalar field as relational time. When the potential term is absent, we are able to associate the expanding and collapsing dynamics of the Universe with [...] Read more.
We analyze the canonical quantum dynamics of the isotropic Universe with a metric approach by adopting a self-interacting scalar field as relational time. When the potential term is absent, we are able to associate the expanding and collapsing dynamics of the Universe with the positive- and negative-frequency modes that emerge in the Wheeler–DeWitt equation. On the other side, when the potential term is present, a non-zero transition amplitude from positive- to negative-frequency states arises, as in standard relativistic scattering theory below the particle creation threshold. In particular, we are able to compute the transition probability for an expanding Universe that emerges from a collapsing regime both in the standard quantization procedure and in the polymer formulation. The probability distribution results similar in the two cases, and its maximum takes place when the mean values of the momentum essentially coincide in the in-going and out-going wave packets, as it would take place in a semiclassical Big Bounce dynamics. Full article
(This article belongs to the Special Issue Universe: Feature Papers 2023—Cosmology)
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9 pages, 1169 KiB  
Article
Galaxy Rotation Curve Fitting Using Machine Learning Tools
by Carlos R. Argüelles and Santiago Collazo
Universe 2023, 9(8), 372; https://doi.org/10.3390/universe9080372 - 16 Aug 2023
Viewed by 1123
Abstract
Galaxy rotation curve (RC) fitting is an important technique which allows the placement of constraints on different kinds of dark matter (DM) halo models. In the case of non-phenomenological DM profiles with no analytic expressions, the art of finding RC best-fits including the [...] Read more.
Galaxy rotation curve (RC) fitting is an important technique which allows the placement of constraints on different kinds of dark matter (DM) halo models. In the case of non-phenomenological DM profiles with no analytic expressions, the art of finding RC best-fits including the full baryonic + DM free parameters can be difficult and time-consuming. In the present work, we use a gradient descent method used in the backpropagation process of training a neural network, to fit the so-called Grand Rotation Curve of the Milky Way (MW) ranging from ∼1 pc all the way to ∼105 pc. We model the mass distribution of our Galaxy including a bulge (inner + main), a disk, and a fermionic dark matter (DM) halo known as the Ruffini-Argüelles-Rueda (RAR) model. This is a semi-analytical model built from first-principle physics such as (quantum) statistical mechanics and thermodynamics, whose more general density profile has a dense corediluted halo morphology with no analytic expression. As shown recently and further verified here, the dark and compact fermion-core can work as an alternative to the central black hole in SgrA* when including data at milliparsec scales from the S-cluster stars. Thus, we show the ability of this state-of-the-art machine learning tool in providing the best-fit parameters to the overall MW RC in the 102105 pc range, in a few hours of CPU time. Full article
(This article belongs to the Special Issue Remo Ruffini Festschrift)
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11 pages, 605 KiB  
Article
Analytical Approximations to Charged Black Hole Solutions in Einstein–Maxwell–Weyl Gravity
by Sheng-Yuan Li, Ming Zhang, De-Cheng Zou and Meng-Yun Lai
Universe 2023, 9(8), 371; https://doi.org/10.3390/universe9080371 - 15 Aug 2023
Viewed by 683
Abstract
The homotopy analysis method (HAM) is a useful method to derive analytical approximate solutions of black holes in modified gravity theories. In this paper, we study the Einstein–Weyl gravity coupled with Maxwell field and obtain analytical approximation solutions for charged black holes by [...] Read more.
The homotopy analysis method (HAM) is a useful method to derive analytical approximate solutions of black holes in modified gravity theories. In this paper, we study the Einstein–Weyl gravity coupled with Maxwell field and obtain analytical approximation solutions for charged black holes by using the HAM. It is found that the analytical approximate solutions are sufficiently accurate in the entire spacetime outside the black hole’s event horizon and also consistent with numerical ones for charged black holes in the Einstein–Maxwell–Weyl gravity. Full article
(This article belongs to the Special Issue Black Hole Thermodynamics, 2nd Edition)
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7 pages, 1023 KiB  
Communication
Proposition of FSR Photon Suppression Employing a Two-Positron Decay Dark Matter Model to Explain Positron Anomaly in Cosmic Rays
by Ramin Barak, Konstantin Belotsky and Ekaterina Shlepkina
Universe 2023, 9(8), 370; https://doi.org/10.3390/universe9080370 - 15 Aug 2023
Viewed by 776
Abstract
The origin of an anomalous excess of high-energy (about 100 GeV and higher) positrons in cosmic rays is one of the rare problems in this field, which is proposed to be solved with dark matter (DM). Attempts to solve this problem are faced [...] Read more.
The origin of an anomalous excess of high-energy (about 100 GeV and higher) positrons in cosmic rays is one of the rare problems in this field, which is proposed to be solved with dark matter (DM). Attempts to solve this problem are faced with the issue of having to satisfy the data on cosmic positrons and cosmic gamma radiation, which inevitably accompanies positron production, such as FSR (final state radiation), simultaneously. We have been trying to come up with a solution by means of two approaches: making assumptions (*) about the spatial distribution of the dark matter and (**) about the physics of its interactions. This work is some small final step of a big investigation regarding the search for gamma suppression by employing the second approach, and a model with a doubly charged particle decaying into two positrons (X++e+e+) is suggested as the most prospective one from those considered before. Full article
(This article belongs to the Special Issue Focus on Dark Matter)
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12 pages, 3001 KiB  
Article
The Upcoming GAMMA-400 Experiment
by Sergey I. Suchkov, Irina V. Arkhangelskaja, Andrey I. Arkhangelskiy, Aleksey V. Bakaldin, Irina V. Chernysheva, Arkady M. Galper, Oleg D. Dalkarov, Andrey E. Egorov, Maxim D. Kheymits, Mikhail G. Korotkov, Aleksey A. Leonov, Svetlana A. Leonova, Alexandr G. Malinin, Vladimir V. Mikhailov, Pavel Yu Minaev, Nikolay Yu. Pappe, Mikhail V. Razumeyko, Nikolay P. Topchiev and Yuri T. Yurkin
Universe 2023, 9(8), 369; https://doi.org/10.3390/universe9080369 - 14 Aug 2023
Viewed by 852
Abstract
The upcoming GAMMA-400 experiment will be implemented aboard the Russian astrophysical space observatory, which will be operating in a highly elliptical orbit over a period of 7 years to provide new data on gamma-ray emissions and cosmic-ray electron + positron fluxes, mainly from [...] Read more.
The upcoming GAMMA-400 experiment will be implemented aboard the Russian astrophysical space observatory, which will be operating in a highly elliptical orbit over a period of 7 years to provide new data on gamma-ray emissions and cosmic-ray electron + positron fluxes, mainly from the galactic plane, the Galactic Center, and the Sun. The main observation mode will be a continuous point-source mode, with a duration of up to ~100 days. The GAMMA-400 gamma-ray telescope will study high-energy gamma-ray emissions of up to several TeV and cosmic-ray electrons + positrons up to 20 TeV. The GAMMA-400 telescope will have a high angular resolution, high energy and time resolutions, and a very good separation efficiency for separating gamma rays from the cosmic-ray background and the electrons + positrons from protons. A distinctive feature of the GAMMA-400 gamma-ray telescope is its wonderful angular resolution for energies of >30 GeV (0.01° for Eγ = 100 GeV), which exceeds the resolutions of space-based and ground-based gamma-ray telescopes by a factor of 5–10. GAMMA-400 studies can reveal gamma-ray emissions from dark matter particles’ annihilation or decay, identify many unassociated, discrete sources, explore the extended sources’ structures, and improve the cosmic-ray electron + positron spectra data for energies of >30 GeV. Full article
(This article belongs to the Special Issue Astrophysics of Cosmic Rays from Space)
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20 pages, 559 KiB  
Article
Black Holes Hint towards De Sitter Matrix Theory
by Leonard Susskind
Universe 2023, 9(8), 368; https://doi.org/10.3390/universe9080368 - 11 Aug 2023
Cited by 62 | Viewed by 1687
Abstract
De Sitter black holes and other non-perturbative configurations can be used to probe the holographic degrees of freedom of de Sitter space. For small black holes, evidence was first provided in the seminal work of Banks, Fiol, and Morrise and follow-ups by Banks [...] Read more.
De Sitter black holes and other non-perturbative configurations can be used to probe the holographic degrees of freedom of de Sitter space. For small black holes, evidence was first provided in the seminal work of Banks, Fiol, and Morrise and follow-ups by Banks and Fischler, showing that dS is described by a form of matrix theory. For large black holes, the evidence provided here is new: Gravitational calculations and matrix theory calculations of the rates of exponentially rare fluctuations match one another in surprising detail. The occurrences of Nariai geometry and the “inside-out” transition are particularly interesting examples, which I explain in this paper. Full article
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27 pages, 3402 KiB  
Review
Lepton–Nucleus Interactions within Microscopic Approaches
by Alessandro Lovato, Alexis Nikolakopoulos, Noemi Rocco and Noah Steinberg
Universe 2023, 9(8), 367; https://doi.org/10.3390/universe9080367 - 9 Aug 2023
Cited by 5 | Viewed by 1739
Abstract
This review paper emphasizes the significance of microscopic calculations with quantified theoretical error estimates in studying lepton–nucleus interactions and their implications for electron scattering and accelerator neutrino oscillation measurements. We investigate two approaches: Green’s Function Monte Carlo and the extended factorization scheme, utilizing [...] Read more.
This review paper emphasizes the significance of microscopic calculations with quantified theoretical error estimates in studying lepton–nucleus interactions and their implications for electron scattering and accelerator neutrino oscillation measurements. We investigate two approaches: Green’s Function Monte Carlo and the extended factorization scheme, utilizing realistic nuclear target spectral functions. In our study, we include relativistic effects in Green’s Function Monte Carlo and validate the inclusive electron scattering cross section on carbon using available data. We compare the flux-folded cross sections for neutrino-carbon scattering with T2K and MINERνA experiments, noting the substantial impact of relativistic effects in reducing the theoretical curve strength when compared to MINERνA data. Additionally, we demonstrate that quantum Monte Carlo-based spectral functions accurately reproduce the quasi-elastic region in electron scattering data and T2K flux-folded cross sections. By comparing results from Green’s Function Monte Carlo and the spectral function approach, which share a similar initial target state description, we quantify errors associated with approximations in the factorization scheme and the relativistic treatment of kinematics in Green’s Function Monte Carlo. Full article
(This article belongs to the Special Issue Many Body Theory)
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14 pages, 3906 KiB  
Article
Untying the Growth Index to Relieve the σ8 Discomfort
by Ziad Sakr
Universe 2023, 9(8), 366; https://doi.org/10.3390/universe9080366 - 8 Aug 2023
Cited by 8 | Viewed by 883
Abstract
The matter fluctuation parameter σ8 is, by model construction, degenerate with the growth index γ. Here, we study the effect on the cosmological parameter constraints by treating each independently from one another, considering σ8 as a free and non-derived parameter [...] Read more.
The matter fluctuation parameter σ8 is, by model construction, degenerate with the growth index γ. Here, we study the effect on the cosmological parameter constraints by treating each independently from one another, considering σ8 as a free and non-derived parameter along with a free γ. We then try to constrain all parameters using three probes that span from deep to local redshifts, namely the CMB spectrum, the growth measurements from redshift space distortions fσ8, and the galaxy cluster counts. We also aim to assess the impact of this relaxation on the σ8 tension between its inferred CMB value in comparison to that obtained from local cluster counts. We also propose a more sophisticated correction, along with the classical one, that takes into account the impact of cosmology on the growth measurements when the parameters are varied in the Monte Carlo process, which consist in adjusting the growth to keep the observed power spectrum, integrated over all angles and scales, as invariant with the background evolution. We found by using the classical correction that untying the two parameters does not shift the maximum likelihood of either σ8 or γ, but it rather enables larger bounds with respect to when σ8 is a derived parameter, and that when considering CMB + fσ8, or when further combining with cluster counts albeit with tighter bounds. Precisely, we obtain σ8=0.809±0.043 and γ=0.613±0.046 in agreement with Planck’s constraint for the former and compatible with ΛCDM for the latter but with bounds wide enough to accommodate both values subject to the tensions. Allowing for massive neutrinos does not change the situation much. On the other hand, considering a tiered correction yields σ8=0.734±0.013 close to ∼1 σ for the inferred local values albeit with a growth index of γ=0.636±0.022 at ∼2 σ from its ΛCDM value. Allowing for massive neutrinos in this case yielded σ8=0.756±0.024, still preferring low values but with much looser constraints on γ=0.549±0.048 and a slight preference for Σmν0.19. We conclude that untying σ8 and γ helps in relieving the discomfort on the former between the CMB and local probes, and that careful analysis should be followed when using data products treated in a model-dependent way. Full article
(This article belongs to the Special Issue Modified Gravity Approaches to the Tensions of ΛCDM)
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12 pages, 8396 KiB  
Article
Effects of Coupling Constants on Chaos of Charged Particles in the Einstein–Æther Theory
by Caiyu Liu and Xin Wu
Universe 2023, 9(8), 365; https://doi.org/10.3390/universe9080365 - 7 Aug 2023
Cited by 3 | Viewed by 803
Abstract
There are two free coupling parameters c13 and c14 in the Einstein–Æther metric describing a non-rotating black hole. This metric is the Reissner–Nordström black hole solution when 02c13<c14<2, but it is [...] Read more.
There are two free coupling parameters c13 and c14 in the Einstein–Æther metric describing a non-rotating black hole. This metric is the Reissner–Nordström black hole solution when 02c13<c14<2, but it is not for 0c14<2c13<2. When the black hole is immersed in an external asymptotically uniform magnetic field, the Hamiltonian system describing the motion of charged particles around the black hole is not integrable; however, the Hamiltonian allows for the construction of explicit symplectic integrators. The proposed fourth-order explicit symplectic scheme is used to investigate the dynamics of charged particles because it exhibits excellent long-term performance in conserving the Hamiltonian. No universal rule can be given to the dependence of regular and chaotic dynamics on varying one or two parameters c13 and c14 in the two cases of 02c13<c14<2 and 0c14<2c13<2. The distributions of order and chaos in the binary parameter space (c13,c14) rely on different combinations of the other parameters and the initial conditions. Full article
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16 pages, 2963 KiB  
Article
The Infrared Extinction Law in the Ophiuchus Molecular Cloud Based on the UKIDSS and Spitzer c2d Surveys
by Jun Li and Xi Chen
Universe 2023, 9(8), 364; https://doi.org/10.3390/universe9080364 - 4 Aug 2023
Cited by 2 | Viewed by 796
Abstract
Investigating the extinction properties in dense molecular clouds is of significant importance for understanding the behavior of interstellar dust and its impact on observations. In this study, we comprehensively examined the extinction law in the Ophiuchus cloud across a wavelength range from 0.8 [...] Read more.
Investigating the extinction properties in dense molecular clouds is of significant importance for understanding the behavior of interstellar dust and its impact on observations. In this study, we comprehensively examined the extinction law in the Ophiuchus cloud across a wavelength range from 0.8 μm to 8 μm. To achieve this, we analyzed NIR and MIR data obtained from the UKIDSS GCS and the Spitzer c2d survey, respectively. By fitting a series of color–color diagrams, we determined color-excess ratios EJλ/EJK for seven passbands. These ratios were then directly converted to derive the relative extinction law Aλ/AK. Our findings demonstrate that the Ophiuchus cloud exhibits a characteristic of flat MIR extinction, consistent with previous studies. Additionally, our results reveal variations in the extinction law with extinction depth, indicating a flatter trend from the NIR to MIR bands as extinction increases. Notably, our analysis reveals no significant difference in the MIR extinction law among the four dark clouds: L1712, L1689, L1709, and L1688. However, distinct variations were observed in the extinction law for regions outside the dark clouds, specifically L1688N and L1688W. These regions displayed lower color-excess ratios EJλ/EJK in the Spitzer/IRAC bands. This observation lends support to the dust growth occurring in the dense regions of the Ophiuchus cloud. Full article
(This article belongs to the Special Issue Distribution and Evolution of Interstellar Dust)
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12 pages, 489 KiB  
Article
Constraining the Thickness of the Galactic Halo through Cosmic-Ray Anisotropy Using the Spatial-Dependent-Propagation Model
by Bing-Qiang Qiao, Yu-Hua Yao, Wei Liu, Qiang Yuan, Xiao-Jun Bi, Hong-Bo Hu and Yi-Qing Guo
Universe 2023, 9(8), 363; https://doi.org/10.3390/universe9080363 - 4 Aug 2023
Viewed by 869
Abstract
The spatial-dependent-propagation (SDP) model with a nearby source works well to reproduce the coevolving features of both cosmic-ray (CR)-nuclei spectra and anisotropy. However, it is well known that the Sun is actually deviating from the galactic disk. This will lead to a dominating [...] Read more.
The spatial-dependent-propagation (SDP) model with a nearby source works well to reproduce the coevolving features of both cosmic-ray (CR)-nuclei spectra and anisotropy. However, it is well known that the Sun is actually deviating from the galactic disk. This will lead to a dominating anisotropy in the direction perpendicular to the galactic disk, which is discrepant with current observations. Thus, it is necessary to further investigate the effect of the solar offset on anisotropy. In this work, to the best of our knowledge, this is the first time that the combined studies of the solar offset, nuclei spectra, and anisotropy have been performed based on the SDP model. As a result, to reproduce CR spectra and anisotropy, the thickness of the inner halo (ZIH) needs to increase linearly with the displacement of the Sun. We also know that the PeV anisotropy could be used to estimate the value of the diffusion coefficient, thus breaking the degeneracy between the diffusion coefficient and halo thickness. Therefore, it is a good approach to constrain the halo thickness. Moreover, the anisotropy in the PeV energy region, as a new probe, might also shed new light on constraining the solar offset. It is hoped that the anisotropy of the energies from ∼TeV to PeV can be finely measured with the LHAASO experiment, leading to a better understanding of the thick halo. Full article
(This article belongs to the Section Space Science)
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23 pages, 904 KiB  
Article
Search for Super-Deformed Identical Bands in the A = 190 Mass Region on the Basis of Level Spin
by Poonam Jain, Yogesh Kumar, Vinod Kumar and Pargin Bangotra
Universe 2023, 9(8), 362; https://doi.org/10.3390/universe9080362 - 3 Aug 2023
Viewed by 837
Abstract
The systematic study of Super-Deformed (SD) bands in the A=190 mass region has been performed. We observed a large number of pairs of SD bands, with different mass numbers, having transition energies nearly equal (within 3 keV) and having identical dynamic [...] Read more.
The systematic study of Super-Deformed (SD) bands in the A=190 mass region has been performed. We observed a large number of pairs of SD bands, with different mass numbers, having transition energies nearly equal (within 3 keV) and having identical dynamic moments of inertia. The bands having nearly equal transitions energies and other parameters are called identical bands. We have performed detailed analysis and found 16 pairs of Super-Deformed Identical Bands (SDIBs) whose Eγ energies and moment of inertia are in good agreement with each other. The modified Variable Moment of Inertia (VMI) model is applied to 16 pairs of SDIBs to estimate the band spins by fitting the two parameters J0 and C. We found that out of 16 pairs, the band-head spin is consistent with moment of inertia and transition energies for four pairs. For another seven pairs, the transition energies and moment of inertia are identical, but originate from levels with different spins. The remaining five pairs have the identical energy but spins are either increasing or decreasing by one unit in the pair. Secondly, the NpNn scheme is applied to verify the existence of SDIBs. The parameters deduced from the NpNn scheme are also in good agreement for the mentioned case. The study indicates that each pair of conjugate nuclei have nearly identical spin, moment of inertia (dynamic) and gamma transition energy. Full article
(This article belongs to the Special Issue Collectivity in High-Energy Proton-Proton and Heavy-Ion Collisions)
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13 pages, 355 KiB  
Article
Lévy α-Stable Model for the Non-Exponential Low-|t| Proton–Proton Differential Cross-Section
by Tamás Csörgő, Sándor Hegyi and István Szanyi
Universe 2023, 9(8), 361; https://doi.org/10.3390/universe9080361 - 3 Aug 2023
Cited by 2 | Viewed by 755
Abstract
It is known that the Real Extended Bialas–Bzdak (ReBB) model describes the proton–proton (pp) and proton–antiproton (pp¯) differential cross-section data in a statistically non-excludible way, i.e., with a confidence level greater than or equal to 0.1% [...] Read more.
It is known that the Real Extended Bialas–Bzdak (ReBB) model describes the proton–proton (pp) and proton–antiproton (pp¯) differential cross-section data in a statistically non-excludible way, i.e., with a confidence level greater than or equal to 0.1% in the center of mass energy range 546 GeV s8 TeV and in the squared four-momentum transfer range 0.37 GeV2 ≤ −t ≤ 1.2 GeV2. Considering, instead of Gaussian, a more general Lévy α-stable shape for the parton distributions of the constituent quark and diquark inside the proton and for the relative separation between them, a generalized description of data is obtained, where the ReBB model corresponds to the α=2 special case. Extending the model to α<2, we conjecture that the validity of the model can be extended to a wider kinematic range, in particular, to lower values of the four-momentum transfer t. We present the formal Lévy α-stable generalization of the Bialas–Bzdak model and show that a simplified version of this model can be successfully fitted, with α<2, to the non-exponential, low t differential cross-section data of elastic proton–proton scattering at s=8 TeV. Full article
(This article belongs to the Special Issue Zimányi School – Heavy Ion Physics)
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10 pages, 902 KiB  
Article
Observation and Data Reduction of the Brown Dwarf 2MASSW J0746425 + 200032 by Five-Hundred-Meter Aperture Spherical Radio Telescope
by Tianhao Su, Liyun Zhang, Xuyang Gao, Qingfeng Pi, Prabhakar Misra and Xianming L. Han
Universe 2023, 9(8), 360; https://doi.org/10.3390/universe9080360 - 3 Aug 2023
Viewed by 862
Abstract
The unprecedented sensitivity provided by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) could shed light on studies of the magnetic field and plasma properties of brown dwarfs by catching polarized radio flares. With the FAST L-band 19-beam receiver, we observe a nearby dwarf [...] Read more.
The unprecedented sensitivity provided by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) could shed light on studies of the magnetic field and plasma properties of brown dwarfs by catching polarized radio flares. With the FAST L-band 19-beam receiver, we observe a nearby dwarf stellar system 2MASSW J0746425 + 200032 which has been reported to show 4.86 GHz and 8.46 GHz radio flare emission. The L-band radio signals from the target are searched in both total intensity and circular polarization during the entire 147 min tracking observation. No radio flare down to a sensitivity of ∼13 mJy and ∼2 mJy (5σ) in Stokes I and V can be identified. The non-detection may lie in the intrinsic physical condition of the stellar system, e.g., the magnetic field strength and the electron density distribution and/or the sampling rate, which should be higher to reveal the sub-second structures but are smeared out with a lower rate in our observations. Full article
(This article belongs to the Section Stellar Astronomy)
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15 pages, 1774 KiB  
Article
A Concept of Assessment of LIV Tests with THESEUS Using the Gamma-Ray Bursts Detected by Fermi/GBM
by Anastasia Tsvetkova, Luciano Burderi, Alessandro Riggio, Andrea Sanna and Tiziana Di Salvo
Universe 2023, 9(8), 359; https://doi.org/10.3390/universe9080359 - 31 Jul 2023
Viewed by 1118
Abstract
According to Einstein’s special relativity theory, the speed of light in a vacuum is constant for all observers. However, quantum gravity effects could introduce its dispersion depending on the energy of photons. The investigation of the spectral lags between the gamma-ray burst (GRB) [...] Read more.
According to Einstein’s special relativity theory, the speed of light in a vacuum is constant for all observers. However, quantum gravity effects could introduce its dispersion depending on the energy of photons. The investigation of the spectral lags between the gamma-ray burst (GRB) light curves recorded in distinct energy ranges could shed light on this phenomenon: the lags could reflect the variation of the speed of light if it is linearlydependent on the photon energy and a function of the GRB redshift. We propose a methodology to start investigating the dispersion law of light propagation in a vacuum using GRB light curves. This technique is intended to be fully exploited using the GRB data collected with THESEUS. Full article
(This article belongs to the Special Issue GRBs Phenomenology, Models and Applications: A Beginner Guide)
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12 pages, 373 KiB  
Article
Mission Target: Tetraquark Mesons of Flavour-Cryptoexotic Type
by Wolfgang Lucha
Universe 2023, 9(8), 358; https://doi.org/10.3390/universe9080358 - 31 Jul 2023
Viewed by 1136
Abstract
Currently, flavour-cryptoexotic tetraquarks form the most common sort of all experimentally established exotic multiquark hadrons. This note points out a few promising concepts that should help improve theoretical (but, for several reasons, not quite straightforward) analyses of this kind of states; among others, [...] Read more.
Currently, flavour-cryptoexotic tetraquarks form the most common sort of all experimentally established exotic multiquark hadrons. This note points out a few promising concepts that should help improve theoretical (but, for several reasons, not quite straightforward) analyses of this kind of states; among others, their scope of application encompasses the strong interactions in the limit of (arbitrarily) large numbers of colours, and equally analytical and nonperturbative approaches to multiquark states. Full article
(This article belongs to the Special Issue Recent Progress in Hadron Spectroscopy)
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34 pages, 7302 KiB  
Article
Jovian Periodicities (~10 h, ~40, 20, 15 min) at ACE, Upstream from the Earth’s Bow Shock, on 25–27 November 2003
by Georgios C. Anagnostopoulos, Panagiotis K. Marhavilas, Efthymios Vassiliadis and Emmanuel T. Sarris
Universe 2023, 9(8), 357; https://doi.org/10.3390/universe9080357 - 30 Jul 2023
Viewed by 1030
Abstract
It is known that Jovian radio and high energy electron emissions are observed near Earth. The question we address in this study is whether the quasi-periodic ~10 h and ~40/15–20 min (QP-10 h, QP-40/15–20 min) energetic particle and magnetic field periodicities observed by [...] Read more.
It is known that Jovian radio and high energy electron emissions are observed near Earth. The question we address in this study is whether the quasi-periodic ~10 h and ~40/15–20 min (QP-10 h, QP-40/15–20 min) energetic particle and magnetic field periodicities observed by Ulysses during its distant encounter with Jupiter in 2003 were also detectable as far as the Earth’s orbit. Surprisingly, we found that at the end of the extreme 2003 Halloween events, during times of a highly disturbed Jovian magnetosphere, as inferred from strong bKOM radio emissions observed by Ulysses, and a magnetic connection of Earth with the Jovian magnetosphere, as suggested by simulation results of the interplanetary magnetic field (IMF), the ACE satellite observed, between at least 25–27 November 2013 at the Lagrangian Point L1 (LPL1), all the characteristic Jovian periodicities. In particular, by using high-time resolution data (1/5 min), we found, for the first time, quasi-permanent electron, and magnetic field QP-10/5 h, QP-40 min and QP-15/20 data variations at LPL1 for at least three days. These observations reasonably suggest that low energy (~50–~300 keV) Jovian electrons reached the Earth’s environment; the observations examined extend the lowest energy limit of the Jovian electron spectrum from 200 keV to ~50 keV. In addition, the ACE satellite observed an impressive series of QP-10/5 h energetic (≤0.05 MeV) ion bursts (EIBs) with strong cross-field intensity gradients at the onset/decay phase of the events and energy-dependent field aligned anisotropy suggesting ion streaming in the anti-sunward direction during their main phase. A comparison of simultaneously obtained measurements by ACE at the LPL1 and by Geotail upstream from the bow shock and in the magnetosphere suggests that the QP-10/5 h EIBs are inconsistent with the concept of a terrestrial origin. On the contrary, the observations indicate that the series of QP-10/5 h EIBs on 25–27 November 2003 was a spatial effect caused by the ~10/5 h quasi-periodic approach of a large-scale sheet to the Earth’s environment. The source of the ion population forming the QP-10/5 h sharp EIBs seems most probably Jovian ions accumulated in the interplanetary space, although a solar ion contribution is possible. Based on the above results, it is reasonable to suggest that the observed QP-10 h, QP-40 min and QP-15/20 periodicities are due to Jovian influence. Further research is needed to study the cause of the QP-10/5 h EIBs. This study presents new data which extend our view on the influence of the QP-10 h/QP-40/QP-15/20 min Jovian emissions from the outer to the inner heliosphere at 1 AU. Full article
(This article belongs to the Special Issue Solar Energetic Particles)
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20 pages, 333 KiB  
Article
An Exact Model of a Gravitational Wave in the Bianchi III Universe Based on Shapovalov II Wave Spacetime and the Quadratic Theory of Gravity
by Konstantin Osetrin, Ilya Kirnos and Evgeny Osetrin
Universe 2023, 9(8), 356; https://doi.org/10.3390/universe9080356 - 30 Jul 2023
Cited by 1 | Viewed by 747
Abstract
Exact models of primordial gravitational waves in the Bianchi type-III universe were constructed on the basis of the quadratic theory of gravity with a scalar field and pure radiation in Shapovalov wave spacetimes of type II (subtype 2). Exact solutions of the field [...] Read more.
Exact models of primordial gravitational waves in the Bianchi type-III universe were constructed on the basis of the quadratic theory of gravity with a scalar field and pure radiation in Shapovalov wave spacetimes of type II (subtype 2). Exact solutions of the field equations and scalar equation were obtained. The characteristics of pure radiation were determined. An explicit form of the scalar field functions included in the Lagrangian of the considered quadratic theory of gravity was found. The trajectories of the propagation of light rays in the considered gravitational wave models were obtained. Full article
(This article belongs to the Special Issue Universe: Feature Papers 2023—Gravitation)
14 pages, 3773 KiB  
Article
Design and Construction of a Variable-Angle Three-Beam Stimulated Resonant Photon Collider toward eV-Scale ALP Search
by Takumi Hasada, Kensuke Homma and Yuri Kirita
Universe 2023, 9(8), 355; https://doi.org/10.3390/universe9080355 - 29 Jul 2023
Cited by 2 | Viewed by 756
Abstract
We aim to search for axion-like particles in the eV mass range using a variable-angle stimulated resonance photon collider (SRPC) with three intense laser beams. By changing angle of incidence of the three beams, the center-of-mass-system collision energy can be varied and the [...] Read more.
We aim to search for axion-like particles in the eV mass range using a variable-angle stimulated resonance photon collider (SRPC) with three intense laser beams. By changing angle of incidence of the three beams, the center-of-mass-system collision energy can be varied and the eV mass range can be continuously searched for. In this paper, we present the design and construction of such a variable-angle three-beam SRPC (tSRPC), the verification of the variable-angle mechanism using a calibration laser, and realistic sensitivity projections for searches in the near future. Full article
(This article belongs to the Special Issue Origins and Natures of Inflation, Dark Matter and Dark Energy)
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16 pages, 613 KiB  
Article
Synthesis of Elements in Compact Stars in Pycnonuclear Reactions with Carbon Isotopes: Quasibound States vs. States of Zero-Points Vibrations
by Sergei P. Maydanyuk, Gyorgy Wolf and Kostiantyn A. Shaulsky
Universe 2023, 9(8), 354; https://doi.org/10.3390/universe9080354 - 29 Jul 2023
Cited by 1 | Viewed by 759
Abstract
(1) Purpose: Conditions of formation of compound nuclear systems needed for synthesis of heavy nuclei in pycnonuclear reactions in compact stars are studied on a quantum mechanical basis. (2) Methods: The method of multiple internal reflections is applied for pycnonuclear reactions in compact [...] Read more.
(1) Purpose: Conditions of formation of compound nuclear systems needed for synthesis of heavy nuclei in pycnonuclear reactions in compact stars are studied on a quantum mechanical basis. (2) Methods: The method of multiple internal reflections is applied for pycnonuclear reactions in compact stars with new calculations of quasibound spectra and spectra of zero-point vibrations. (3) Results: Peculiarities of the method are analyzed for reaction with isotopes of Carbon. The developed method takes into account continuity and conservation of quantum flux (describing pycnonuclear reaction) inside the full spacial region of reaction, including the nuclear region. This gives the appearance of new states (called quasibound states) in which compound nuclear systems of Magnesium are formed with the largest probability. These states have not been studied yet in synthesis of elements in stars. Energy spectra of zero-point vibrations and spectra of quasibound states are estimated with high precision for reactions with isotopes of Carbon. For the first time, the influence of plasma screening on quasibound states and states of zero-point vibrations in pycnonuclear reactions has been studied. (4) Conclusions: The probability of formation of a compound nucleus in quasibound states in pycnonuclear reaction is essentially larger than the probability of formation of this system in states of zero-point vibrations studied by Zel’dovich and followers. Therefore, synthesis of Magnesium from isotopes of Carbon is more probable through the quasibound states than through the states of zero-point vibrations in compact stars. Energy spectra of zero-point vibrations are changed essentially after taking plasma screening into account. Analysis shows that from all studied isotopes of Magnesium, only 24Mg is stable after synthesis at an energy of relative motion of 4.881 MeV of the incident nuclei 12C. Full article
(This article belongs to the Special Issue Zimányi School – Heavy Ion Physics)
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11 pages, 6309 KiB  
Article
Conjunction Ground Triangulation of Auroras and Magnetospheric Processes Observed by the Van Allen Probe Satellite near 6 Re
by Boris V. Kozelov and Elena E. Titova
Universe 2023, 9(8), 353; https://doi.org/10.3390/universe9080353 - 29 Jul 2023
Viewed by 878
Abstract
Conjunction observations of auroras with electron distributions and broadband electrostatic fluctuations on Van Allen Probe A satellite in the equatorial region are considered. Using triangulation measurements, the energy spectra of the precipitating electrons in the rayed auroral structures were determined for the 17 [...] Read more.
Conjunction observations of auroras with electron distributions and broadband electrostatic fluctuations on Van Allen Probe A satellite in the equatorial region are considered. Using triangulation measurements, the energy spectra of the precipitating electrons in the rayed auroral structures were determined for the 17 March 2015 event. A comparison of the spectra of precipitating electrons in the auroral rays with satellite measurements of electrons in the equatorial region related to the aurora showed their agreement. The concomitance between Van Allen Probe A broadband electric waves and auroral variations measured by the ground-based auroral camera was observed on 17 March 2015. This suggests that broadband electrostatic waves may be responsible for electron precipitation, leading to the formation of rayed structures in the aurora. Full article
(This article belongs to the Special Issue Auroral Physics)
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13 pages, 774 KiB  
Communication
A Generalized Double Chaplygin Model for Anisotropic Matter: The Newtonian Case
by Gabriel Abellán, Ángel Rincón and Eduard Sanchez
Universe 2023, 9(8), 352; https://doi.org/10.3390/universe9080352 - 28 Jul 2023
Cited by 4 | Viewed by 814
Abstract
In this work, we investigate astrophysical systems in a Newtonian regime using anisotropic matter. For this purpose, we considered that both radial and tangential pressures satisfy a generalized Chaplygin-type equation of state. Using this model, we found the Lane–Emden equation for this system [...] Read more.
In this work, we investigate astrophysical systems in a Newtonian regime using anisotropic matter. For this purpose, we considered that both radial and tangential pressures satisfy a generalized Chaplygin-type equation of state. Using this model, we found the Lane–Emden equation for this system and solved it numerically for several sets of parameters. Finally, we explored the mass supported by this physical system and compared it with the Chandrasekhar mass. Full article
(This article belongs to the Section Gravitation)
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16 pages, 3394 KiB  
Article
Analysis of the Ionospheric Response to Sudden Stratospheric Warming and Geomagnetic Forcing over Europe during February and March 2023
by Rumiana Bojilova and Plamen Mukhtarov
Universe 2023, 9(8), 351; https://doi.org/10.3390/universe9080351 - 28 Jul 2023
Cited by 3 | Viewed by 1017
Abstract
A study of the behavior of the main characteristics of the ionosphere over Europe during the 26–28 February 2023 ionospheric storm was carried out in this present work. The additional influence of sudden stratospheric warming on the ionosphere was considered. The behavior of [...] Read more.
A study of the behavior of the main characteristics of the ionosphere over Europe during the 26–28 February 2023 ionospheric storm was carried out in this present work. The additional influence of sudden stratospheric warming on the ionosphere was considered. The behavior of the critical frequency of the ionosphere foF2 (characterizing the maximum electron density), the peak height of the F2-layer (hmF2), and Total Electron Content (TEC) were investigated through their relative deviations from the quiet conditions. The behavior of the TEC over Europe showed the geographic latitudinal dependence of the response. The variability in the ionospheric critical frequency was represented by the data of 10 ionospheric stations for vertical sounding located in two groups: (i) near the prime meridian and (ii) near the 25° E meridian. Some differences were found in the response compared to the TEC response, which was explained by the different responses of the top maximum region and bottom maximum region. The peak height of the F2 layer varied strongly during the storm, which was due to the forced drift of ionospheric plasma induced by additional electric fields. The present detailed analysis of the ionospheric response shows that the considered storm exhibited characteristic features inherent in the winter season but with some manifestations of reactions in equinox conditions. Full article
(This article belongs to the Special Issue Insights in Space Weather and Space Climate of the Solar System)
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11 pages, 530 KiB  
Article
Statistical Study of Geo-Effectiveness of Planar Magnetic Structures Evolved within ICME’s
by Kalpesh Ghag, Bhagyashri Sathe, Anil Raghav, Zubair Shaikh, Digvijay Mishra, Ankush Bhaskar, Tarun Kumar Pant, Omkar Dhamane, Prathmesh Tari, Prachi Pathare, Vinit Pawaskar, Kishor Kumbhar and Greg Hilbert
Universe 2023, 9(8), 350; https://doi.org/10.3390/universe9080350 - 27 Jul 2023
Cited by 4 | Viewed by 972
Abstract
Interplanetary coronal mass ejections (ICME) are large-scale eruptions from the Sun and prominent drivers of space weather disturbances, especially intense/extreme geomagnetic storms. Recent studies by our group showed that ICME sheaths and/or magnetic clouds (MC) could be transformed into a planar magnetic structure [...] Read more.
Interplanetary coronal mass ejections (ICME) are large-scale eruptions from the Sun and prominent drivers of space weather disturbances, especially intense/extreme geomagnetic storms. Recent studies by our group showed that ICME sheaths and/or magnetic clouds (MC) could be transformed into a planar magnetic structure (PMS) and speculate that these structures might be more geo-effective. Thus, we statistically investigated the geo-effectiveness of planar and non-planar ICME sheaths and MC regions. We analyzed 420 ICME events observed from 1998 to 2017, and we found that the number of intense (100 to 200 nT) and extreme (<200 nT) geomagnetic storms are large during planar ICMEs (almost double) compared to non-planar ICMEs. In fact, almost all the extreme storm events occur during PMS molded ICME crossover. The observations suggest that planar structures are more geo-effective than non-planar structures. Thus, the current study helps us to understand the energy transfer mechanism from the ICME/solar wind into the magnetosphere, and space-weather events. Full article
(This article belongs to the Special Issue The Solar Origin of Space Weather)
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9 pages, 1355 KiB  
Review
The Andromeda Galaxy and Its Star Formation History
by Denis Leahy
Universe 2023, 9(8), 349; https://doi.org/10.3390/universe9080349 - 26 Jul 2023
Cited by 1 | Viewed by 1413
Abstract
The state of knowledge of the properties of the Andromeda Galaxy (also known as M31) is reviewed. The spatial structure of the Andromeda Galaxy, its main source populations, and the properties of its gas and dust are discussed. To understand the formation history [...] Read more.
The state of knowledge of the properties of the Andromeda Galaxy (also known as M31) is reviewed. The spatial structure of the Andromeda Galaxy, its main source populations, and the properties of its gas and dust are discussed. To understand the formation history of the Andromeda Galaxy, the critical issues of its star formation history and the gas streams and dwarf galaxies in its surrounding environment are reviewed. Emphasis is on recent studies, with important earlier work described in the references provided here. It is important to understand the Andromeda Galaxy because it is the nearest large external galaxy and is close enough for high-resolution studies. This allows the Andromeda Galaxy to be used as a template for understanding more distant and less resolved galaxies in the universe. Full article
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19 pages, 1961 KiB  
Article
Trajectory Optimization and Control Applied to Landing Maneuvers on Phobos from Mars-Phobos Distant Retrograde Orbits
by Vittorio Baraldi and Davide Conte
Universe 2023, 9(8), 348; https://doi.org/10.3390/universe9080348 - 25 Jul 2023
Viewed by 1753
Abstract
This paper presents research on the application of trajectory design, optimization, and control to an orbital transfer from Mars–Phobos Distant Retrograde Orbits to the surface of Phobos. Given a Distant Retrograde Orbit and a landing location on the surface of Phobos, landing trajectories [...] Read more.
This paper presents research on the application of trajectory design, optimization, and control to an orbital transfer from Mars–Phobos Distant Retrograde Orbits to the surface of Phobos. Given a Distant Retrograde Orbit and a landing location on the surface of Phobos, landing trajectories for which total Δv for a direct 2-burn maneuver is minimized are computed. This is accomplished through the use of Particle Swarm Optimization in which the required Δv and time of flight are optimization parameters. The non-uniform gravitational environment of Phobos is considered in the computation. Results show how direct transfers can be achieved with Δv on the order of ∼30 m/s. Full article
(This article belongs to the Section Gravitation)
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19 pages, 3625 KiB  
Review
The ESSnuSB Design Study: Overview and Future Prospects
by A. Alekou, E. Baussan, A. K. Bhattacharyya, N. Blaskovic Kraljevic, M. Blennow, M. Bogomilov, B. Bolling, E. Bouquerel, F. Bramati, A. Branca, O. Buchan, A. Burgman, C. J. Carlile, J. Cederkall, S. Choubey, P. Christiansen, M. Collins, E. Cristaldo Morales, L. D’Alessi, H. Danared, D. Dancila, J. P. A. M. de André, J. P. Delahaye, M. Dracos, I. Efthymiopoulos, T. Ekelöf, M. Eshraqi, G. Fanourakis, A. Farricker, E. Fernandez-Martinez, B. Folsom, T. Fukuda, N. Gazis, B. Gålnander, Th. Geralis, M. Ghosh, A. Giarnetti, G. Gokbulut, L. Halić, M. Jenssen, R. Johansson, A. Kayis Topaksu, B. Kildetoft, B. Kliček, M. Kozioł, K. Krhač, Ł. Łacny, M. Lindroos, A. Longhin, C. Maiano, S. Marangoni, C. Marrelli, C. Martins, D. Meloni, M. Mezzetto, N. Milas, M. Oglakci, T. Ohlsson, M. Olvegård, T. Ota, M. Pari, J. Park, D. Patrzalek, G. Petkov, P. Poussot, F. Pupilli, S. Rosauro-Alcaraz, D. Saiang, J. Snamina, A. Sosa, G. Stavropoulos, M. Stipčević, B. Szybiński, R. Tarkeshian, F. Terranova, J. Thomas, T. Tolba, E. Trachanas, R. Tsenov, G. Vankova-Kirilova, N. Vassilopoulos, E. Wildner, J. Wurtz, O. Zormpa and Y. Zouadd Show full author list remove Hide full author list
Universe 2023, 9(8), 347; https://doi.org/10.3390/universe9080347 - 25 Jul 2023
Cited by 5 | Viewed by 1338
Abstract
ESSnuSB is a design study for an experiment to measure the CP violation in the leptonic sector at the second neutrino oscillation maximum using a neutrino beam driven by the uniquely powerful ESS linear accelerator. The reduced impact of systematic errors on sensitivity [...] Read more.
ESSnuSB is a design study for an experiment to measure the CP violation in the leptonic sector at the second neutrino oscillation maximum using a neutrino beam driven by the uniquely powerful ESS linear accelerator. The reduced impact of systematic errors on sensitivity at the second maximum allows for a very precise measurement of the CP violating parameter. This review describes the fundamental advantages of measurement at the second maximum, the necessary upgrades to the ESS linac in order to produce a neutrino beam, the near and far detector complexes, and the expected physics reach of the proposed ESSnuSB experiment, concluding with the near future developments aimed at the project realization. Full article
(This article belongs to the Special Issue Neutrinos from Artificial Sources)
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