Next Issue
Volume 8, July
Previous Issue
Volume 8, May
 
 

Universe, Volume 8, Issue 6 (June 2022) – 44 articles

Cover Story (view full-size image): We calculate the spin structure functions for spin-dependent elastic and inelastic WIMP scattering off 119Sn and 121Sb. Estimates for detection rates are also given. 119Sn and 121Sb are amenable to nuclear structure calculations using the nuclear shell model (NSM). With the possible exception of 201Hg, they are the only such nuclei still unexplored theoretically for their potential of inelastic WIMP scattering to a very low excited state. The present calculations have been carried out using a state-of-the-art WIMP–nucleus scattering formalism. Structure functions were found to be high for both nuclei in the case of elastic scattering. Detection rate calculations indicate that inelastic scattering is relevant for both nuclei, even surpassing elastic rates for some recoil energies. View this paper
  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Reader to open them.
Order results
Result details
Section
Select all
Export citation of selected articles as:
20 pages, 360 KiB  
Article
Significance of Charge on the Dynamics of Hyperbolically Distributed Fluids
by Z. Yousaf, G. G. L. Nashed, M. Z. Bhatti and H. Asad
Universe 2022, 8(6), 337; https://doi.org/10.3390/universe8060337 - 20 Jun 2022
Cited by 4 | Viewed by 1155
Abstract
This manuscript is devoted to analyze hyperbolically symmetric non-static fluid distribution incorporated with heat flux and electromagnetic field. We have developed a general framework in order to examine the dynamic regime of the matter configuration which eventually results in the static spacetime. With [...] Read more.
This manuscript is devoted to analyze hyperbolically symmetric non-static fluid distribution incorporated with heat flux and electromagnetic field. We have developed a general framework in order to examine the dynamic regime of the matter configuration which eventually results in the static spacetime. With the aim of doing this, we constructed the Einstein-Maxwell (EM) field equations and obtained the conservation equation. Furthermore, the formulation of mass function indicates the presence of the negative energy density, which leads towards the significant quantum implications. Taking into account the transport equation, we have observed the thermodynamical attributes of the fluid. Additionally, quasi- homologous constraint has been utilized to construct several models. We have deduced the worthwhile applications of the astrophysical objects by evaluating several analytical solutions in terms of the kinematical variables. Full article
(This article belongs to the Section Mathematical Physics)
3 pages, 3039 KiB  
Editorial
Editorial to the Special Issue “Quantum Cosmology”
by Paulo Vargas Moniz
Universe 2022, 8(6), 336; https://doi.org/10.3390/universe8060336 - 20 Jun 2022
Cited by 1 | Viewed by 1076
Abstract
Some time ago, when I first inquired as to ‘what quantum cosmology is about’, I did approach the hall with a combination of caution as well as eagerness [...] Full article
(This article belongs to the Special Issue Quantum Cosmology)
15 pages, 852 KiB  
Review
Ultra Long Period Cepheids: Observation and Theory
by Ilaria Musella
Universe 2022, 8(6), 335; https://doi.org/10.3390/universe8060335 - 18 Jun 2022
Cited by 6 | Viewed by 1596
Abstract
Ultra Long Period Cepheids are becoming a very interesting and important topic thanks to the contribution that they can give to understanding the current tension existing between the early-universe and local Hubble constant measurements. These bright pulsating variables are observable up to cosmological [...] Read more.
Ultra Long Period Cepheids are becoming a very interesting and important topic thanks to the contribution that they can give to understanding the current tension existing between the early-universe and local Hubble constant measurements. These bright pulsating variables are observable up to cosmological distances (larger than 100 Mpc) allowing us, in principle, to measure the Hubble constant without the need for secondary indicators, thus reducing the possible systematic errors in the calibration of the extragalactic distance scale. The Ultra Long Period Cepheids also represent a useful tool for obtaining information on the star formation history of the host galaxy and a challenge for the evolutionary and pulsational models, particularly in the very metal poor regime. In this paper, the largest known ULP sample, consisting of 72 objects, including 10 new candidates, is analyzed to give an observational and theoretical overview of their role as distance indicators and of their evolutionary properties. Full article
(This article belongs to the Special Issue Recent Advances in Pulsating Stars)
Show Figures

Figure 1

39 pages, 523 KiB  
Review
Review on Stochastic Approach to Inflation
by Diego Cruces
Universe 2022, 8(6), 334; https://doi.org/10.3390/universe8060334 - 17 Jun 2022
Cited by 18 | Viewed by 1638
Abstract
We present a review on the state-of-the-art of the mathematical framework known as stochastic inflation, paying special attention to its derivation, and giving references for the readers interested in results coming from the application of the stochastic framework to different inflationary scenarios, especially [...] Read more.
We present a review on the state-of-the-art of the mathematical framework known as stochastic inflation, paying special attention to its derivation, and giving references for the readers interested in results coming from the application of the stochastic framework to different inflationary scenarios, especially to those of interest for primordial black hole formation. During the derivation of the stochastic formalism, we will emphasise two aspects in particular: the difference between the separate universe approach and the true long wavelength limit of scalar inhomogeneities and the generically non-Markovian nature of the noises that appear in the stochastic equations. Full article
(This article belongs to the Special Issue Primordial Black Holes from Inflation)
13 pages, 603 KiB  
Article
Explaining the ‘Outliers’ Track in Black Hole X-ray Binaries with a BZ-Jet and Inner-Disk Coupling
by Ning Chang, Xiang Liu, Fu-Guo Xie, Lang Cui and Hao Shan
Universe 2022, 8(6), 333; https://doi.org/10.3390/universe8060333 - 17 Jun 2022
Cited by 1 | Viewed by 1552
Abstract
In this paper, we investigate the black hole (BH) spin contribution to jet power, especially for the magnetic arrested disk (MAD), where only inner accretion disk luminosity is closely coupled with the spin-jet power, and try to explain the ‘outliers’ track of the [...] Read more.
In this paper, we investigate the black hole (BH) spin contribution to jet power, especially for the magnetic arrested disk (MAD), where only inner accretion disk luminosity is closely coupled with the spin-jet power, and try to explain the ‘outliers’ track of the radio LR to X-ray luminosity LX in two black hole X-ray binaries (BHXBs). Our results suggest that the BZ-jet and the inner-disk coupling could account for the ‘outliers’ track of the radio/X-ray correlation in two BHXBs, H1743-322 and MAXI J1348-630. Although the accretion disk of H1743-322 in the outburst could be in the MAD state, there is a lower probability that MAXI J1348-630 is in the MAD state due to its low jet production efficiency. The difference in the inner-disk bolometric luminosity ratio of the two sources implies that these two BHXBs are in different inner-disk accretion states. We further investigate the phase-changing regime of MAXI J1348-630 and find that there is a phase transition around LX/LEdd103. The assumption of sub-MAD is discussed as well. Full article
(This article belongs to the Special Issue Advances in Astrophysics and Cosmology – in Memory of Prof. Tan Lu)
Show Figures

Figure 1

18 pages, 502 KiB  
Article
Topological Gauge Actions on the Lattice as Overlap Fermion Determinants
by Nikhil Karthik and Rajamani Narayanan
Universe 2022, 8(6), 332; https://doi.org/10.3390/universe8060332 - 17 Jun 2022
Viewed by 1274
Abstract
Overlap fermion on the lattice has been shown to properly reproduce topological aspects of gauge fields. In this paper, we review the derivation of Overlap fermion formalism in a torus of three space-time dimensions. Using the formalism, we show how to use the [...] Read more.
Overlap fermion on the lattice has been shown to properly reproduce topological aspects of gauge fields. In this paper, we review the derivation of Overlap fermion formalism in a torus of three space-time dimensions. Using the formalism, we show how to use the Overlap fermion determinants in the massless and infinite mass limits to construct different continuum topological gauge actions, such as the level-k Chern–Simons action, “half-CS” term and the mixed Chern–Simons (BF) coupling, in a gauge-invariant lattice UV regulated manner. Taking special Abelian and non-Abelian background fields, we demonstrate numerically how the lattice formalism beautifully reproduces the continuum expectations, such as the flow of action under large gauge transformations. Full article
Show Figures

Figure 1

15 pages, 3605 KiB  
Article
Numerical Simulation of Ionospheric Disturbances Due to Rocket Plume and Its Influence on HF Radio Waves Propagation
by Hongwei Gong, Hanxian Fang and Zeyun Li
Universe 2022, 8(6), 331; https://doi.org/10.3390/universe8060331 - 15 Jun 2022
Cited by 1 | Viewed by 1330
Abstract
In this paper, the ionospheric disturbances of CO2, which is released by rocket exhaust plumes, was simulated. The effect of this disturbance on the propagation of high-frequency (HF) radio waves at different incident frequencies was also simulated by using three-dimensional digital [...] Read more.
In this paper, the ionospheric disturbances of CO2, which is released by rocket exhaust plumes, was simulated. The effect of this disturbance on the propagation of high-frequency (HF) radio waves at different incident frequencies was also simulated by using three-dimensional digital ray tracing technique. The results show that CO2 can effectively dissipate the background electrons and form ionospheric holes after being released in the ionosphere. At the peak height of ionospheric electron density (about 300 km), the electrons are dissipated fastest and the radius of ionospheric hole is also largest. This is due to the fact that the diffusion coefficient of CO2 usually increases with height while the electron density just increases before reaching its peak height and then decreases with height, and the chemical reaction rate between ions and CO2 also becomes largest at the peak height of electron density (about 300 km). Around 100 s after the release of CO2, when the radio waves at a frequency of 8 MHz pass through the ionosphere with an elevation range of 85~95°, the “secondary focusing effect” can occur, and we believe that this is due to the reflection of HF shortwaves on the walls of the ionospheric holes. With time going on, this phenomenon disappears at 300 s and only one focus is left at this time. For the HF shortwaves at same incident frequency, the focusing effect of waves displays a weakening trend with time increasing, and the height of focus center also ascends gradually. At the same time after CO2 releasing, with the increasing of radio waves frequency, the focusing effect also becomes weaker and the focus center displays an ascending trend. Full article
(This article belongs to the Section Space Science)
Show Figures

Figure 1

10 pages, 1998 KiB  
Article
Modulation of Solar Wind Impact on the Earth’s Magnetosphere during the Solar Cycle
by Francesco Carbone, Daniele Telloni, Emiliya Yordanova and Luca Sorriso-Valvo
Universe 2022, 8(6), 330; https://doi.org/10.3390/universe8060330 - 14 Jun 2022
Cited by 1 | Viewed by 1528
Abstract
The understanding of extreme geomagnetic storms is one of the key issues in space weather. Such phenomena have been receiving increasing attention, especially with the aim of forecasting strong geomagnetic storms generated by high-energy solar events since they can severely perturb the near-Earth [...] Read more.
The understanding of extreme geomagnetic storms is one of the key issues in space weather. Such phenomena have been receiving increasing attention, especially with the aim of forecasting strong geomagnetic storms generated by high-energy solar events since they can severely perturb the near-Earth space environment. Here, the disturbance storm time index Dst, a crucial geomagnetic activity proxy for Sun–Earth interactions, is analyzed as a function of the energy carried by different solar wind streams. To determine the solar cycle activity influence on Dst, a 12-year dataset was split into sub-periods of maximum and minimum solar activity. Solar wind energy and geomagnetic activity were closely correlated for both periods of activity. Slow wind streams had negligible effects on Earth regardless of their energy, while high-speed streams may induce severe geomagnetic storming depending on the energy (kinetic or magnetic) carried by the flow. The difference between the two periods may be related to the higher rate of geo-effective events during the maximum activity, where coronal mass ejections represent the most energetic and geo-effective driver. During the minimum period, despite a lower rate of high energetic events, a moderate disturbance in the Dst index can be induced. Full article
(This article belongs to the Special Issue Advances in Solar Wind Origin and Evolution)
Show Figures

Figure 1

15 pages, 6046 KiB  
Review
The Role of Radio Observations in Studies of Infrared-Bright Galaxies: Prospects for a Next-Generation Very Large Array
by Eric Joseph Murphy
Universe 2022, 8(6), 329; https://doi.org/10.3390/universe8060329 - 14 Jun 2022
Cited by 2 | Viewed by 1642
Abstract
The bulk of the present-day stellar mass was formed in galaxies when the universe was less than half its current age (i.e., 1z3). While this likely marks one of the most critical time periods for galaxy evolution, we [...] Read more.
The bulk of the present-day stellar mass was formed in galaxies when the universe was less than half its current age (i.e., 1z3). While this likely marks one of the most critical time periods for galaxy evolution, we currently do not have a clear picture on the radial extent and distribution of cold molecular gas and associated star formation within the disks of galaxies during this epoch. Such observations are essential to properly estimate the efficiency at which such galaxies convert their gas into stars, as well as to account for the various energetic processes that govern this efficiency. Long-wavelength (i.e., far-infrared–to–radio) observations are critical to penetrate the high-levels of extinction associated with dusty, infrared-bright galaxies that are driving the stellar mass assembly at such epochs. In this article, we discuss how the next-generation Very Large Array will take a transformative step in our understanding of galaxy formation and evolution by delivering the ability to simultaneously study the relative distributions molecular gas and star formation on sub-kpc scales unbiased by dust for large populations of typical galaxies in the early universe detected by future far-infrared space missions. Full article
(This article belongs to the Special Issue Recent Advances in Infrared Galaxies and AGN)
Show Figures

Figure 1

23 pages, 588 KiB  
Article
Onset of Electron Captures and Shallow Heating in Magnetars
by Nicolas Chamel and Anthea Francesca Fantina
Universe 2022, 8(6), 328; https://doi.org/10.3390/universe8060328 - 11 Jun 2022
Cited by 1 | Viewed by 1952
Abstract
The loss of magnetic pressure accompanying the decay of the magnetic field in a magnetar may trigger exothermic electron captures by nuclei in the shallow layers of the stellar crust. Very accurate analytical formulas are obtained for the threshold density and pressure, as [...] Read more.
The loss of magnetic pressure accompanying the decay of the magnetic field in a magnetar may trigger exothermic electron captures by nuclei in the shallow layers of the stellar crust. Very accurate analytical formulas are obtained for the threshold density and pressure, as well as for the maximum amount of heat that can be possibly released, taking into account the Landau–Rabi quantization of electron motion. These formulas are valid for arbitrary magnetic field strengths, from the weakly quantizing regime to the most extreme situation in which electrons are all confined to the lowest level. Numerical results are also presented based on experimental nuclear data supplemented with predictions from the Brussels-Montreal model HFB-24. This same nuclear model has been already employed to calculate the equation of state in all regions of magnetars. Full article
(This article belongs to the Special Issue Advances in Magnetars)
Show Figures

Figure 1

15 pages, 1036 KiB  
Article
Estimating the Transit Speed and Time of Arrival of Interplanetary Coronal Mass Ejections Using CME and Solar Flare Data
by Anatoly Belov, Nataly Shlyk, Maria Abunina, Artem Abunin and Athanasios Papaioannou
Universe 2022, 8(6), 327; https://doi.org/10.3390/universe8060327 - 11 Jun 2022
Cited by 6 | Viewed by 1794
Abstract
The dependence of Interplanetary Coronal Mass Ejections’ (ICMEs) transit speed on the corresponding Coronal Mass Ejections’ (CMEs) initial speed is investigated. It is shown that the transit speed and transit time depend not only on the CME’s initial speed, but also on the [...] Read more.
The dependence of Interplanetary Coronal Mass Ejections’ (ICMEs) transit speed on the corresponding Coronal Mass Ejections’ (CMEs) initial speed is investigated. It is shown that the transit speed and transit time depend not only on the CME’s initial speed, but also on the longitude of the solar source. The longitudinal dependence of the expected transit speeds and times are obtained from the analysis of 288 CMEs, associated with solar flares, observed from 1995 to 2020. A model, estimating the transit and maximum speeds, as well as the time of arrival of an ICME to Earth, based on the initial CME speed and the longitude of the associated solar flare has been created. It is shown that taking into account the longitude of the solar source in addition to the initial CME speed significantly improves the quality of the model, especially for events in the central part of the solar disk (E10°–W10°). The simplicity of the described model makes it accessible to a wide range of users and provides opportunities for further improvement as the statistics and the number of input parameters increase. Full article
(This article belongs to the Special Issue Propagation of Coronal Mass Ejections)
Show Figures

Figure 1

31 pages, 548 KiB  
Article
Leading Singularities in Higher-Derivative Yang–Mills Theory and Quadratic Gravity
by Gabriel Menezes
Universe 2022, 8(6), 326; https://doi.org/10.3390/universe8060326 - 10 Jun 2022
Cited by 4 | Viewed by 1325
Abstract
In this work, we explore general leading singularities of one-loop amplitudes in higher-derivative Yang–Mills and quadratic gravity. These theories are known to possess propagators which contain quadratic and quartic momentum dependence, which leads to the presence of an unstable ghostlike resonance. However, unitarity [...] Read more.
In this work, we explore general leading singularities of one-loop amplitudes in higher-derivative Yang–Mills and quadratic gravity. These theories are known to possess propagators which contain quadratic and quartic momentum dependence, which leads to the presence of an unstable ghostlike resonance. However, unitarity cuts are not to be taken through unstable particles and therefore unitarity is still satisfied. On the other hand, this could engender issues when calculating leading singularities which are generalizations of unitarity cuts. Nevertheless, we will show with explicit examples how leading singularities are still well defined and accordingly they are able to capture relevant information on the analytic structure of amplitudes in such higher-derivative theories. We discuss some simple one-loop amplitudes which clarify these features. Full article
(This article belongs to the Special Issue Probing the Quantum Space-Time)
Show Figures

Figure 1

10 pages, 271 KiB  
Article
Analytic Solution and Noether Symmetries for the Hyperbolic Inflationary Model in the Jordan Frame
by Andronikos Paliathanasis
Universe 2022, 8(6), 325; https://doi.org/10.3390/universe8060325 - 10 Jun 2022
Cited by 3 | Viewed by 1204
Abstract
The Noether symmetry analysis is applied for the study of a multifield cosmological model in a spatially flat FLRW background geometry. The gravitational Action Integral consists of two scalar fields, the Brans–Dicke field and a second scalar field minimally coupled to gravity. However, [...] Read more.
The Noether symmetry analysis is applied for the study of a multifield cosmological model in a spatially flat FLRW background geometry. The gravitational Action Integral consists of two scalar fields, the Brans–Dicke field and a second scalar field minimally coupled to gravity. However, the two scalar fields interact in kinetic terms. This multifield has been found to describe the equivalent of hyperbolic inflation in the Jordan frame. The application of Noether’s theorems constrains the free parameters of the model so that conservation laws exist. We find that the field equations form an integrable dynamical system, and the analytic solution is derived. Full article
(This article belongs to the Section Cosmology)
18 pages, 3278 KiB  
Article
Ulysses Flyby in the Heliosphere: Comparison of the Solar Wind Model with Observational Data
by Evgeniy V. Maiewski, Helmi V. Malova, Victor Yu. Popov and Lev M. Zelenyi
Universe 2022, 8(6), 324; https://doi.org/10.3390/universe8060324 - 10 Jun 2022
Cited by 2 | Viewed by 1959
Abstract
A model capable of reproducing a set of solar wind parameters along the virtual spacecraft orbit out of an ecliptic plane has been developed. In the framework of a quasi-stationary axisymmetric self-consistent MHD model the spatial distributions of magnetic field and plasma characteristics [...] Read more.
A model capable of reproducing a set of solar wind parameters along the virtual spacecraft orbit out of an ecliptic plane has been developed. In the framework of a quasi-stationary axisymmetric self-consistent MHD model the spatial distributions of magnetic field and plasma characteristics at distances from 20 to 1200 Solar radii at almost all solar latitudes could be obtained and analyzed. This model takes into account the Sun’s magnetic field evolution during the solar cycle, when the dominant dipole magnetic field is replaced by the quadrupole one. Self-consistent solutions for solar wind characteristics were obtained, depending on the phase of the solar cycle. To verify the model, its results are compared with the observed characteristics of solar wind along the Ulysses trajectory during its flyby around the Sun from 1990 to 2009. It is shown that the results of numerical simulation are generally consistent with the observational data obtained by the Ulysses spacecraft. A comparison of the model and experimental data confirms that the model can adequately describe the solar wind parameters and can be used for heliospheric studies at different phases of the solar activity cycle, as well as in a wide range of latitudinal angles and distances to the Sun. Full article
Show Figures

Figure 1

31 pages, 464 KiB  
Review
Lorentz Symmetry Violation of Cosmic Photons
by Ping He and Bo-Qiang Ma
Universe 2022, 8(6), 323; https://doi.org/10.3390/universe8060323 - 9 Jun 2022
Cited by 20 | Viewed by 2569
Abstract
As a basic symmetry of space-time, Lorentz symmetry has played important roles in various fields of physics, and it is a glamorous question whether Lorentz symmetry breaks. Since Einstein proposed special relativity, Lorentz symmetry has withstood very strict tests, but there are still [...] Read more.
As a basic symmetry of space-time, Lorentz symmetry has played important roles in various fields of physics, and it is a glamorous question whether Lorentz symmetry breaks. Since Einstein proposed special relativity, Lorentz symmetry has withstood very strict tests, but there are still motivations for Lorentz symmetry violation (LV) research from both theoretical consideration and experimental feasibility, that attract physicists to work on LV theories, phenomena and experimental tests with enthusiasm. There are many theoretical models including LV effects, and different theoretical models predict different LV phenomena, from which we can verify or constrain LV effects. Here, we introduce three types of LV theories: quantum gravity theory, space-time structure theory and effective field theory with extra-terms. Limited by the energy of particles, the experimental tests of LV are very difficult; however, due to the high energy and long propagation distance, high-energy particles from astronomical sources can be used for LV phenomenological researches. Especially with cosmic photons, various astronomical observations provide rich data from which one can obtain various constraints for LV researches. Here, we review four common astronomical phenomena which are ideal for LV studies, together with current constraints on LV effects of photons. Full article
(This article belongs to the Special Issue Ultra High Energy Photons)
24 pages, 482 KiB  
Article
The Macro-Physics of the Quark-Nova: Astrophysical Implications
by Rachid Ouyed
Universe 2022, 8(6), 322; https://doi.org/10.3390/universe8060322 - 9 Jun 2022
Cited by 3 | Viewed by 1589
Abstract
A quark-nova is a hypothetical stellar evolution branch where a neutron star converts explosively into a quark star. Here, we discuss the intimate coupling between the micro-physics and macro-physics of the quark-nova and provide a prescription for how to couple the Burn-UD code [...] Read more.
A quark-nova is a hypothetical stellar evolution branch where a neutron star converts explosively into a quark star. Here, we discuss the intimate coupling between the micro-physics and macro-physics of the quark-nova and provide a prescription for how to couple the Burn-UD code to the stellar evolution code in order to simulate neutron-star-to-quark-star burning at stellar scales and estimate the resulting energy release and ejecta. Once formed, the thermal evolution of the proto-quark star follows. We found much higher peak neutrino luminosities (>1055 erg/s) and a higher energy neutrino (i.e., harder) spectrum than previous stellar evolution studies of proto-neutron stars. We derived the neutrino counts that observatories such as Super-Kamiokande-III and Halo-II should expect and suggest how these can differentiate between a supernova and a quark-nova. Due to the high peak neutrino luminosities, neutrino pair annihilation can deposit as much as 1052 ergs in kinetic energy in the matter overlaying the neutrinosphere, yielding relativistic quark-nova ejecta. We show how the quark-nova could help us understand many still enigmatic high-energy astrophysical transients, such as super-luminous supernovae, gamma-ray bursts and fast radio bursts. Full article
(This article belongs to the Special Issue Properties and Dynamics of Neutron Stars and Proto-Neutron Stars)
Show Figures

Figure 1

15 pages, 352 KiB  
Review
Testing Quantum Gravity in the Multi-Messenger Astronomy Era
by Aleksandra Piórkowska-Kurpas and Marek Biesiada
Universe 2022, 8(6), 321; https://doi.org/10.3390/universe8060321 - 8 Jun 2022
Cited by 2 | Viewed by 1710
Abstract
Quantum gravity (QG) remains elusive despite almost century-long efforts to combine general relativity and quantum mechanics. All the approaches triggered and powered by purely theoretical considerations eventually failed with a prevailing feeling of a complete lack of guidance from the experimental side. Currently, [...] Read more.
Quantum gravity (QG) remains elusive despite almost century-long efforts to combine general relativity and quantum mechanics. All the approaches triggered and powered by purely theoretical considerations eventually failed with a prevailing feeling of a complete lack of guidance from the experimental side. Currently, however, this circumstance is beginning to change considerably. We have entered the era of multi-messenger astronomy. The electromagnetic window to the universe—so far the only one—has been tremendously enlarged in the energy range beyond gamma rays up to ultra-high-energy photons and has been complemented by other messengers: high-energy cosmic rays, cosmic neutrinos, and gravitational waves (GWs). This has created a unique environment in which to observationally constrain various phenomenological QG effects. In this paper, we focus on the LIV phenomenology manifested as energy-dependent time-of-flight delays and strong lensing time delays. We review results regarding time-of-flight delays obtained with GRBs. We also recall the idea of energy-dependent lensing time delays, which allow one to constrain LIV models independently of the intrinsic time delay. Lastly, we show how strongly a gravitationally lensed GW signal would place interesting constraints on the LIV. Full article
(This article belongs to the Special Issue Ultra High Energy Photons)
12 pages, 3691 KiB  
Article
Chaos in a Magnetized Modified Gravity Schwarzschild Spacetime
by Daqi Yang, Wenfu Cao, Naying Zhou, Hongxing Zhang, Wenfang Liu and Xin Wu
Universe 2022, 8(6), 320; https://doi.org/10.3390/universe8060320 - 8 Jun 2022
Cited by 16 | Viewed by 1569
Abstract
Based on the scalar–tensor–vector modified gravitational theory, a modified gravity Schwarzschild black hole solution has been given in the existing literature. Such a black hole spacetime is obtained through the inclusion of a modified gravity coupling parameter, which corresponds to the modified gravitational [...] Read more.
Based on the scalar–tensor–vector modified gravitational theory, a modified gravity Schwarzschild black hole solution has been given in the existing literature. Such a black hole spacetime is obtained through the inclusion of a modified gravity coupling parameter, which corresponds to the modified gravitational constant and the black hole charge. In this sense, the modified gravity parameter acts as not only an enhanced gravitational effect but also a gravitational repulsive force contribution to a test particle moving around the black hole. Because the modified Schwarzschild spacetime is static spherical symmetric, it is integrable. However, the spherical symmetry and the integrability are destroyed when the black hole is immersed in an external asymptotic uniform magnetic field and the particle is charged. Although the magnetized modified Schwarzschild spacetime is nonintegrable and inseparable, it allows for the application of explicit symplectic integrators when its Hamiltonian is split into five explicitly integrable parts. Taking one of the proposed explicit symplectic integrators and the techniques of Poincaré sections and fast Lyapunov indicators as numerical tools, we show that the charged particle can have chaotic motions under some circumstances. Chaos is strengthened with an increase of the modified gravity parameter from the global phase space structures. There are similar results when the magnetic field parameter and the particle energy increase. However, an increase of the particle angular momentum weakens the strength of chaos. Full article
Show Figures

Figure 1

18 pages, 720 KiB  
Review
Maximal Kinematical Invariance Group of Fluid Dynamics and Applications
by V. V. Sreedhar and Amitabh Virmani
Universe 2022, 8(6), 319; https://doi.org/10.3390/universe8060319 - 7 Jun 2022
Cited by 2 | Viewed by 1359
Abstract
The maximal kinematical invariance group of the Euler equations of fluid dynamics for the standard polytropic exponent is larger than the Galilei group. Specifically, the inversion transformation [...] Read more.
The maximal kinematical invariance group of the Euler equations of fluid dynamics for the standard polytropic exponent is larger than the Galilei group. Specifically, the inversion transformation (Σ:t1/t,xx/t) leaves the Euler equation’s invariant. This duality has been used to explain the striking similarities observed in simulations of the supernova explosions and laboratory implosions induced in plasma by intense lasers. The inversion symmetry extends to discontinuous fluid flows as well. In this contribution, we provide a concise review of these ideas and discuss some applications. We also explicitly work out the implosion dual of the Sedov’s explosion solution. Full article
(This article belongs to the Special Issue Quantum Gravity Phenomenology)
Show Figures

Figure 1

48 pages, 622 KiB  
Review
Covariant Evolution of Gravitoelectromagnetism
by Ashkbiz Danehkar
Universe 2022, 8(6), 318; https://doi.org/10.3390/universe8060318 - 7 Jun 2022
Cited by 2 | Viewed by 1837
Abstract
The long-range gravitational terms associated with tidal forces, frame-dragging effects, and gravitational waves are described by the Weyl conformal tensor, the traceless part of the Riemann curvature that is not locally affected by the matter field. The Ricci and Bianchi identities provide a [...] Read more.
The long-range gravitational terms associated with tidal forces, frame-dragging effects, and gravitational waves are described by the Weyl conformal tensor, the traceless part of the Riemann curvature that is not locally affected by the matter field. The Ricci and Bianchi identities provide a set of dynamical and kinematic equations governing the matter coupling and evolution of the electric and magnetic parts of the Weyl tensor, so-called gravitoelectric and gravitomagnetic fields. A detailed analysis of the Weyl gravitoelectromagnetic fields can be conducted using a number of algebraic and differential identities prescribed by the 1+3 covariant formalism. In this review, we consider the dynamical constraints and propagation equations of the gravitoelectric/-magnetic fields and covariantly debate their analytic properties. We discuss the special conditions under which gravitational waves can propagate, the inconsistency of a Newtonian-like model without gravitomagnetism, the nonlinear generalization to multi-fluid models with different matter species, as well as observational effects caused by the Weyl fields via the kinematic quantities. The 1+3 tetrad and 1+1+2 semi-covariant methods, which can equally be used for gravitoelectromagnetism, are briefly explained, along with their correspondence with the covariant formulations. Full article
(This article belongs to the Special Issue Frame-Dragging and Gravitomagnetism)
11 pages, 444 KiB  
Article
Constraints on the Helium Abundance from Fast Radio Bursts
by Liang Jing and Jun-Qing Xia
Universe 2022, 8(6), 317; https://doi.org/10.3390/universe8060317 - 5 Jun 2022
Cited by 1 | Viewed by 1370
Abstract
Through the relationship between dispersion measures (DM) and redshifts, fast radio bursts (FRBs) are considered to be very promising cosmological probes. In this paper, we attempted to use the DM-z relationship of FRBs to study the helium abundance (YHe) in [...] Read more.
Through the relationship between dispersion measures (DM) and redshifts, fast radio bursts (FRBs) are considered to be very promising cosmological probes. In this paper, we attempted to use the DM-z relationship of FRBs to study the helium abundance (YHe) in the universe. First, we used 17 current FRBs with known redshifts for our study. Due to their low redshifts and the strong degeneracy between YHe and Ωbh2, however, this catalog could not provide a good constraint on the helium abundance. Then, we simulated 500 low redshift FRB mock data with z[0,1.5] to forecast the constraining ability on YHe. In order to break the degeneracy between YHe and Ωbh2 further, we introduced the shift parameters of the Planck measurement (R,lA,Ωbh2) as a prior, where Ωbh2 represents the baryon density parameter, and R and lA correspond to the scaled distance to recombination and the angular scale of the sound horizon at recombination, respectively. We obtained the standard deviation for the helium abundance: σ(YHe)=0.025. Finally, we considered 2000 higher redshift FRB data with the redshift distribution of [0,3] and found that the constraining power for YHe would be improved by more than 2 times, σ(YHe)=0.011, which indicates that the FRB data with high redshift can provide a better constraint on the helium abundance. Hopefully, large FRB samples with high redshift from the Square Kilometre Array can provide high-precision measurements of the helium abundance in the near future. Full article
(This article belongs to the Section Cosmology)
Show Figures

Figure 1

20 pages, 1950 KiB  
Review
Shape Invariant Potentials in Supersymmetric Quantum Cosmology
by Shahram Jalalzadeh, Seyed Meraj M. Rasouli and Paulo Moniz
Universe 2022, 8(6), 316; https://doi.org/10.3390/universe8060316 - 5 Jun 2022
Cited by 6 | Viewed by 1889
Abstract
In this brief review, we comment on the concept of shape invariant potentials, which is an essential feature in many settings of N=2 supersymmetric quantum mechanics. To motivate its application within supersymmetric quantum cosmology, we present a case study to illustrate [...] Read more.
In this brief review, we comment on the concept of shape invariant potentials, which is an essential feature in many settings of N=2 supersymmetric quantum mechanics. To motivate its application within supersymmetric quantum cosmology, we present a case study to illustrate the value of this promising tool. Concretely, we take a spatially flat FRW model in the presence of a single scalar field, minimally coupled to gravity. Then, we extract the associated Schrödinger–Wheeler–DeWitt equation, allowing for a particular scope of factor ordering. Subsequently, we compute the corresponding supersymmetric partner Hamiltonians, H1 and H2. Moreover, we point out how the shape invariance property can be employed to bring a relation among several factor orderings choices for our Schrödinger–Wheeler–DeWitt equation. The ground state is retrieved, and the excited states easily written. Finally, the Hamiltonians, H1 and H2, are explicitly presented within a N=2 supersymmetric quantum mechanics framework. Full article
(This article belongs to the Special Issue Quantum Cosmology)
Show Figures

Figure 1

23 pages, 399 KiB  
Article
Superposition Principle and Kirchhoff’s Integral Theorem
by Mikhail I. Krivoruchenko
Universe 2022, 8(6), 315; https://doi.org/10.3390/universe8060315 - 3 Jun 2022
Cited by 2 | Viewed by 1728
Abstract
The need for modification of the Huygens–Fresnel superposition principle arises even in the description of the free fields of massive particles and, more extensively, in nonlinear field theories. A wide range of formulations and superposition schemes for secondary waves are captured by Kirchhoff’s [...] Read more.
The need for modification of the Huygens–Fresnel superposition principle arises even in the description of the free fields of massive particles and, more extensively, in nonlinear field theories. A wide range of formulations and superposition schemes for secondary waves are captured by Kirchhoff’s integral theorem. We discuss various versions of this theorem as well as its connection with the superposition principle and the method of Green’s functions. A superposition scheme inherent in linear field theories, which is not based on Kirchhoff’s integral theorem but instead relies on the completeness condition, is also discussed. Full article
(This article belongs to the Special Issue Selected Topics in Gravity, Field Theory and Quantum Mechanics)
29 pages, 3133 KiB  
Article
ALPINE: A Large Survey to Understand Teenage Galaxies
by Andreas L. Faisst, Lin Yan, Matthieu Béthermin, Paolo Cassata, Miroslava Dessauges-Zavadsky, Yoshinobu Fudamoto, Michele Ginolfi, Carlotta Gruppioni, Gareth Jones, Yana Khusanova, Olivier LeFèvre, Francesca Pozzi, Michael Romano, John Silverman and Brittany Vanderhoof
Universe 2022, 8(6), 314; https://doi.org/10.3390/universe8060314 - 1 Jun 2022
Cited by 4 | Viewed by 2309
Abstract
A multiwavelength study of galaxies is important to understand their formation and evolution. Only in the recent past, thanks to the Atacama Large (Sub) Millimeter Array (ALMA), were we able to study the far-infrared (IR) properties of galaxies at high redshifts. In this [...] Read more.
A multiwavelength study of galaxies is important to understand their formation and evolution. Only in the recent past, thanks to the Atacama Large (Sub) Millimeter Array (ALMA), were we able to study the far-infrared (IR) properties of galaxies at high redshifts. In this article, we summarize recent research highlights and their significance to our understanding of early galaxy evolution from the ALPINE survey, a large program with ALMA to observe the dust continuum and 158μm C+ emission of normal star-forming galaxies at z= 4–6. Combined with ancillary data at UV through near-IR wavelengths, ALPINE provides the currently largest multiwavelength sample of post-reionization galaxies and has advanced our understanding of (i) the demographics of C+ emission; (ii) the relation of star formation and C+ emission; (iii) the gas content; (iv) outflows and enrichment of the intergalactic medium; and (v) the kinematics, emergence of disks, and merger rates in galaxies at z>4. ALPINE builds the basis for more detailed measurements with the next generation of telescopes, and places itself as an important post-reionization baseline sample to allow a continuous study of galaxies over 13 billion years of cosmic time. Full article
(This article belongs to the Special Issue Recent Advances in Infrared Galaxies and AGN)
Show Figures

Figure 1

21 pages, 410 KiB  
Article
Antistars or Antimatter Cores in Mirror Neutron Stars?
by Zurab Berezhiani
Universe 2022, 8(6), 313; https://doi.org/10.3390/universe8060313 - 31 May 2022
Cited by 10 | Viewed by 1783
Abstract
The oscillation of the neutron n into mirror neutron n, its partner from the dark mirror sector, can gradually transform an ordinary neutron star into a mixed star consisting in part of mirror dark matter. The implications of the reverse process [...] Read more.
The oscillation of the neutron n into mirror neutron n, its partner from the dark mirror sector, can gradually transform an ordinary neutron star into a mixed star consisting in part of mirror dark matter. The implications of the reverse process taking place in the mirror neutron stars depend on the sign of baryon asymmetry in the mirror sector. Namely, if it is negative, as predicted by certain baryogenesis scenarios, then n¯n¯ transitions create a core of our antimatter gravitationally trapped in the mirror star interior. The annihilation of accreted gas on such antimatter cores could explain the origin of γ-source candidates with an unusual spectrum compatible with baryon–antibaryon annihilation, recently identified in the Fermi LAT catalog. In addition, some part of this antimatter escaping after the mergers of mirror neutron stars can produce the flux of cosmic antihelium and also heavier antinuclei which are hunted in the AMS-02 experiment. Full article
(This article belongs to the Special Issue Focus on Dark Matter)
10 pages, 260 KiB  
Article
Solving Linear Tensor Equations II: Including Parity Odd Terms in Four Dimensions
by Damianos Iosifidis
Universe 2022, 8(6), 312; https://doi.org/10.3390/universe8060312 - 31 May 2022
Cited by 3 | Viewed by 1087
Abstract
In this paper, focusing on 4-dimensional space, we extend our previous results of solving linear tensor equations. In particular, we consider a 30-parameter linear tensor equation for the unknown tensor component Nαμν in terms of the known component (source) [...] Read more.
In this paper, focusing on 4-dimensional space, we extend our previous results of solving linear tensor equations. In particular, we consider a 30-parameter linear tensor equation for the unknown tensor component Nαμν in terms of the known component (source) Bαμν. The extension also included the parity even linear terms in Nαμν (and the associated traces), which are formed by contracting the latter with the 4-dimensional Levi-Civita pseudotensor. Assuming generic non-degeneracy conditions and following a step-by-step procedure, we show how to explicitly solve for the unknown tensor field component Nαμν and, consequently, derive its unique and exact solution in terms of the component Bαμν. Full article
(This article belongs to the Section Mathematical Physics)
10 pages, 390 KiB  
Article
Many-Quark Interactions: Large-N Scaling and Contribution to Baryon Masses
by Fabien Buisseret, Cintia T. Willemyns and Claude Semay
Universe 2022, 8(6), 311; https://doi.org/10.3390/universe8060311 - 31 May 2022
Cited by 3 | Viewed by 1275
Abstract
Starting from an effective Hamiltonian modeling, of a baryon made of N identical quarks in the large-N approach of QCD, we obtain analytical formulas, allowing to estimate the contributions of multiquark interactions to the baryon mass. The cases of vanishing (mass spectrum) [...] Read more.
Starting from an effective Hamiltonian modeling, of a baryon made of N identical quarks in the large-N approach of QCD, we obtain analytical formulas, allowing to estimate the contributions of multiquark interactions to the baryon mass. The cases of vanishing (mass spectrum) and non-vanishing (baryon melting) temperatures are treated. Full article
(This article belongs to the Section High Energy Nuclear and Particle Physics)
Show Figures

Figure 1

30 pages, 4326 KiB  
Review
GRB Prompt Emission: Observed Correlations and Their Interpretations
by Tyler Parsotan and Hirotaka Ito
Universe 2022, 8(6), 310; https://doi.org/10.3390/universe8060310 - 31 May 2022
Cited by 7 | Viewed by 2181
Abstract
The prompt emission of Gamma Ray Bursts (GRBs) is still an outstanding question in the study of these cataclysmic events. Part of what makes GRBs difficult to study is how unique each event seems to be. However, aggregating many GRB observations and analyzing [...] Read more.
The prompt emission of Gamma Ray Bursts (GRBs) is still an outstanding question in the study of these cataclysmic events. Part of what makes GRBs difficult to study is how unique each event seems to be. However, aggregating many GRB observations and analyzing the population allows us to obtain a better understanding of the emission mechanism that produces the observed prompt emission. In this review, we outline some of the most prevalent correlations that have emerged from GRB prompt emission observations and how these correlations are interpreted in relation to physical properties and prompt emission models of GRB. Full article
(This article belongs to the Special Issue GRBs Phenomenology, Models and Applications: A Beginner Guide)
Show Figures

Figure 1

10 pages, 730 KiB  
Article
Shell Model Description of Spin-Dependent Elastic and Inelastic WIMP Scattering off 119Sn and 121Sb
by Joona Kasurinen, Jouni Suhonen, Praveen C. Srivastava and Pekka Pirinen
Universe 2022, 8(6), 309; https://doi.org/10.3390/universe8060309 - 31 May 2022
Viewed by 2041
Abstract
In this work, we calculate the spin structure functions for spin-dependent elastic and inelastic WIMP scattering off 119Sn and 121Sb. Estimates for detection rates are also given. 119Sn and 121Sb are amenable to nuclear structure calculations using the nuclear [...] Read more.
In this work, we calculate the spin structure functions for spin-dependent elastic and inelastic WIMP scattering off 119Sn and 121Sb. Estimates for detection rates are also given. 119Sn and 121Sb are amenable to nuclear structure calculations using the nuclear shell model (NSM). With the possible exception of 201Hg, they are the only such nuclei still unexplored theoretically for their potential of inelastic WIMP scattering to a very low excited state. The present calculations were conducted using a state-of-the-art WIMP–nucleus scattering formalism, and the available effective NSM two-body interactions describe the spectroscopic properties of these nuclei reasonably well. Structure functions were found to be high for both nuclei in the case of elastic scattering. Elastic scattering dominated at the zero momentum transfer limit. Detection rate calculations indicated that inelastic scattering was relevant for both nuclei, even surpassing elastic rates for some recoil energies. Full article
Show Figures

Figure 1

5 pages, 252 KiB  
Communication
A Note on Proton Stability in the Standard Model
by Seth Koren
Universe 2022, 8(6), 308; https://doi.org/10.3390/universe8060308 - 30 May 2022
Cited by 6 | Viewed by 1342
Abstract
In this short note, we describe the symmetry responsible for absolute, nonperturbative proton stability in the Standard Model. The SM with Nc colors and Ng generations has an exact, anomaly-free, generation-independent, global symmetry group [...] Read more.
In this short note, we describe the symmetry responsible for absolute, nonperturbative proton stability in the Standard Model. The SM with Nc colors and Ng generations has an exact, anomaly-free, generation-independent, global symmetry group U(1)BNcL×ZNgL, which contains a subgroup of baryon plus lepton number of order 2NcNg. This disallows proton decay for Ng>1. Many well-studied models beyond the SM explicitly break this global symmetry, and the alternative deserves further attention. Full article
Previous Issue
Next Issue
Back to TopTop