Topical Collection "A Trip across the Universe: Our Present Knowledge and Future Perspectives"

Editor

Prof. Dr. Emilio Elizalde
E-Mail Website
Guest Editor
Consejo Superior de Investigaciones Científicas, Instituto de Ciencias del Espacio (CSIC), Institut d'Estudis Espacials de Catalunya (IEEC/CSIC), Campus UAB, Carrer de Can Magrans s/n, 08193 Bellaterra, Spain
Interests: zeta functions; regularization of infinite sums; spexial functions of mathemtatical physics; vacuum fluctuations; theoretical cosmology
Special Issues and Collections in MDPI journals

Topical Collection Information

Dear Colleagues,

The rapid development of the different areas of knowledge that is taking place worldwide is especially remarkable and of paramount importance in the domains of Astronomy and Cosmology. This happens for different reasons—some of which are common to other developments in many branches of knowledge at different levels—with a specific thrust coming in this case from the very important fact that future high-energy experimentation on Earth is bound to become prohibitive in the near future, due to the enormous costs involved. Thus, a good number of high-energy projects are now headed towards the cosmos.

After such breathtaking developments, it is now the perfect time to stop for a moment and recapitulate. In other words, it would be beneficial to spend some time in writing down an elaborated summary of what we have learned until now, that is, what we know at present (or seriously think to know) about our Universe at its many different levels: its origins, evolution, its large-scale structure, the main important details at galactic scale and at the inside level of our own galaxy, and its current evolution towards a still-uncertain future.

The purpose of this Collection should not be mistaken. The Collection will focus on proven evidence, rather than speculations; in the contrasted results published in top-level international journals, which will be summarized here by their authors in a concise and comprehensive way. Cut-and-paste disconnected pieces will not have a place in this Collection, but only brand new—from beginning to end—elaborated accounts of important research facts that are written in a highly understandable way. The aim is to bring this knowledge from the highly specialized journals (often using a rather intricate language and obscure acronyms) to non-specialists (i.e., to a much larger readership) which are avid to gain this knowledge directly from highly reliable sources but in a professional way (thus skipping the too many divulgation source, which abound, containing erroneous concepts and approximations, and wild, unproven speculations).

For the reasons already given, this Collection will find its place within the existing literature. The idea is to situate it half-way between the Special Editions which are now so intensively promoted by different Editorial Houses, and the good non-fiction novels written by first-rated cosmologists and astronomers, who provide their particular visions of the Cosmos. It will be a collective effort, with different contrasting inputs by renowned specialists in the different subjects (this is characteristic of the Special Editions), which will make their knowledge available to non-specialists (which is typical and the main value of the other mentioned category).

This Collection will be a summary of high-quality papers from excellent scholars around the world invited by the Editorial Office and the Editor-in-Chief. Both original research articles and comprehensive review papers are welcome. The papers will be published, free of charge, with full open access after peer review to benefit both authors and readers.

The list of subtopics corresponds to the one given in Galaxies; namely:

  • Astronomy;
  • Astrophysics;
  • Cosmology;
  • Observational astronomy—radio, infrared, optical, X-ray, neutrino, etc.;
  • Planetary science;
  • Astronomy equipment and technologies;
  • Aerospace engineering;
  • Astronomical data analyses;
  • Astrochemistry and astrobiology;
  • Archaeoastronomy;
  • History of astronomy and cosmology;
  • Philosophical issues in cosmology.

Prof. Dr. Emilio Elizalde
Guest Editor

Best Paper Award 2020 (800 CHF) text
 
Winner announcement date: 31 January 2022
download description

2020 Galaxies Best Paper Award for the Topical Collection "A Trip across the Universe: Our Present Knowledge and Future Perspectives" aims to celebrate the 70th birthday of Prof. Dr. Emilio Elizalde (800 CHF)

Winner Announcement Deadline: 31 January 2022

Galaxies Editorial Office is inviting submissions to the Topical Collection "A Trip across the Universe: Our Present Knowledge and Future Perspectives". You can see more details about the Topical Collection here (https://www.mdpi.com/journal/galaxies/special_issues/UniversePerspectives). One winner will be selected for this award based on the citations by 31 December 2021.

Judging Criteria

  • Scientific merit and broad impact;
  • Relevance to the Topical Collection’s field;
  • Originality of research objectives and/or ideas presented;
  • Creativity of the study design or uniqueness of approaches and concepts;
  • Clarity of presentation.

Please submit your paper here (https://susy.mdpi.com/user/manuscripts/upload?journal=galaxies), the sooner the better.

Keywords

  • models of the Universe
  • origin and evolution
  • universal constants
  • theories of gravity
  • astronomical surveys
  • history of astronomy and cosmology
  • philosophical issues

Published Papers (19 papers)

2021

Jump to: 2020

Article
Application of Spatio-Temporal Spectral Analysis for Detection of Seismic Waves in Gravitational-Wave Interferometer
Galaxies 2021, 9(3), 50; https://doi.org/10.3390/galaxies9030050 - 14 Jul 2021
Viewed by 284
Abstract
Mixed spatio–temporal spectral analysis was applied for the detection of seismic waves passing through the west–end building of the Virgo interferometer. The method enables detection of a passing wave, including its frequency, length, direction, and amplitude. A thorough analysis aimed at improving sensitivity [...] Read more.
Mixed spatio–temporal spectral analysis was applied for the detection of seismic waves passing through the west–end building of the Virgo interferometer. The method enables detection of a passing wave, including its frequency, length, direction, and amplitude. A thorough analysis aimed at improving sensitivity of the Virgo detector was made for the data gathered by 38 seismic sensors, in the two–week measurement period, from 24 January to 6 February 2018, and for frequency range 5–20 Hz. Two dominant seismic–wave frequencies were found: 5.5 Hz and 17.1 Hz. The presented method can be applied for a better understanding of the interferometer seismic environment, and by identifying noise sources, help the noise–hunting and mitigation work that eventually leads to interferometer noise suppression. Full article
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Article
Favored Inflationary Models by Scalar Field Condensate Baryogenesis
Galaxies 2021, 9(3), 49; https://doi.org/10.3390/galaxies9030049 - 10 Jul 2021
Viewed by 269
Abstract
We calculate the baryon asymmetry value generated in the Scalar Field Condensate (SCF) baryogenesis model obtained in several inflationary scenarios and different reheating models. We provide analysis of the baryon asymmetry value obtained for more than 70 sets of parameters of the SCF [...] Read more.
We calculate the baryon asymmetry value generated in the Scalar Field Condensate (SCF) baryogenesis model obtained in several inflationary scenarios and different reheating models. We provide analysis of the baryon asymmetry value obtained for more than 70 sets of parameters of the SCF model and the following inflationary scenarios, namely: new inflation, chaotic inflation, Starobinsky inflation, MSSM inflation, quintessential inflation. We considered both cases of efficient thermalization after inflation and delayed thermalization. We have found that the SFC baryogenesis model produces baryon asymmetry orders of magnitude bigger than the observed one for the following inflationary models: new inflation, new inflation model by Shafi and Vilenkin, MSSM inflation, chaotic inflation with high reheating temperature and the simplest Shafi–Vilenkin chaotic inflationary model. Strong diluting mechanisms are needed for these models to reduce the resultant baryon excess at low energies to its observational value today. We have found that a successful generation of the observed baryon asymmetry is possible by the SCF baryogenesis model in Modified Starobinsky inflation, chaotic inflation with low reheating temperature, chaotic inflation in SUGRA, and Quintessential inflation. Full article
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Article
SS 433 Optical Flares: A New Analysis Reveals Their Origin in L2 Overflow Episodes
Galaxies 2021, 9(3), 46; https://doi.org/10.3390/galaxies9030046 - 22 Jun 2021
Viewed by 303
Abstract
The microquasar SS 433 exhibits in Hα intermittent flares. A sequence of observations made in 2004 showed flaring Doppler shifted to both the red and the blue simultaneously. The mean shifts varied from day to day, following the orbital phase of the compact object. At the time, this behaviour was interpreted as indicating an origin in the outer rim of the accretion disk. A new analysis of these old data, presented in this paper, shows that the flares are not eclipsed by the Companion that eclipses the photosphere surrounding the compact object. They are therefore not intermittent sightings of an accretion disk. The alternative explanation is plasma expelled through the L2 point, following the phase of the orbit as it invades the space beyond the system. That space has been mapped with comparatively recent GRAVITY observations of a similar flare in Brγ, indeed revealing a strong rotation component. Full article
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Article
Effects of 2HDM in Electroweak Phase Transition
Galaxies 2021, 9(2), 45; https://doi.org/10.3390/galaxies9020045 - 20 Jun 2021
Cited by 1 | Viewed by 356
Abstract
The entropy production scenarios due to the electroweak phase transition (EWPT) in the framework of the minimal extension of standard model, namely the two Higgs doublet model (2HDM), are revisited. The possibility of first order phase transition is discussed. Intense parameter scanning was [...] Read more.
The entropy production scenarios due to the electroweak phase transition (EWPT) in the framework of the minimal extension of standard model, namely the two Higgs doublet model (2HDM), are revisited. The possibility of first order phase transition is discussed. Intense parameter scanning was done with the help of BSMPT, a C++ package. We perform numerical calculations in order to calculate the entropy production with numerous benchmark points. Full article
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Article
Ergosphere, Photon Region Structure, and the Shadow of a Rotating Charged Weyl Black Hole
Galaxies 2021, 9(2), 43; https://doi.org/10.3390/galaxies9020043 - 18 Jun 2021
Cited by 3 | Viewed by 356
Abstract
In this paper, we explore the photon region and the shadow of the rotating counterpart of a static charged Weyl black hole, which has been previously discussed according to null and time-like geodesics. The rotating black hole shows strong sensitivity to the electric [...] Read more.
In this paper, we explore the photon region and the shadow of the rotating counterpart of a static charged Weyl black hole, which has been previously discussed according to null and time-like geodesics. The rotating black hole shows strong sensitivity to the electric charge and the spin parameter, and its shadow changes from being oblate to being sharp by increasing in the spin parameter. Comparing the calculated vertical angular diameter of the shadow with that of M87*, we found that the latter may possess about 1036 protons as its source of electric charge, if it is a rotating charged Weyl black hole. A complete derivation of the ergosphere and the static limit is also presented. Full article
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Article
Astronomical Seeing at Maidanak Observatory during the Year 2018
Galaxies 2021, 9(2), 38; https://doi.org/10.3390/galaxies9020038 - 21 May 2021
Viewed by 527
Abstract
Results of a four-month campaign of astronomical seeing measurements at Maidanak astronomical observatory (MAO) are presented. A differential image motion monitor (DIMM) was used for seeing estimations during the period from August to November 2018. The observation was organized within the framework of [...] Read more.
Results of a four-month campaign of astronomical seeing measurements at Maidanak astronomical observatory (MAO) are presented. A differential image motion monitor (DIMM) was used for seeing estimations during the period from August to November 2018. The observation was organized within the framework of a site testing for a new telescope which is going to be installed at the observatory. The median value of seeing for the entire period was determined as 0.70 arcseconds, which agrees well with the results of the period 1996–2003. The comparison of monthly values showed that some monthly median values differ from the seasonal trend of the previous period. Full article
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Review
Naturally-Coupled Dark Sectors
Galaxies 2021, 9(2), 33; https://doi.org/10.3390/galaxies9020033 - 12 May 2021
Viewed by 394
Abstract
The dark sector, composed of fields that are neutral under the standard model (SM) gauge group, can couple to the SM through the Higgs, hypercharge and neutrino portals, and pull the SM towards its scale by loop corrections. This instability, which is not [...] Read more.
The dark sector, composed of fields that are neutral under the standard model (SM) gauge group, can couple to the SM through the Higgs, hypercharge and neutrino portals, and pull the SM towards its scale by loop corrections. This instability, which is not possible to prevent in the known SM completions, such as supersymmetry, due to the sizable couplings to the SM, calls for alternative mechanisms that can neutralize sensitivities of the SM to the dark sector scale and to the ultraviolet cutoff above it. Here we review such a mechanism in which incorporation of gravity into the SM predicts the existence of a dark sector and allows it to be naturally coupled to the SM. We discuss and illustrate salient processes that can probe the naturally coupled dark sectors. Full article
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Article
Modeling of Spiral Structure in a Multi-Component Milky Way-Like Galaxy
Galaxies 2021, 9(2), 29; https://doi.org/10.3390/galaxies9020029 - 28 Apr 2021
Viewed by 491
Abstract
Using recent observational data, we construct a set of multi-component equilibrium models of the disk of a Milky Way-like galaxy. The disk dynamics are studied using collisionless-gaseous numerical simulations, based on the joined integration of the equations of motion for the collision-less particles [...] Read more.
Using recent observational data, we construct a set of multi-component equilibrium models of the disk of a Milky Way-like galaxy. The disk dynamics are studied using collisionless-gaseous numerical simulations, based on the joined integration of the equations of motion for the collision-less particles using direct integration of gravitational interaction and the gaseous SPH-particles. We find that after approximately one Gyr, a prominent central bar is formed having a semi-axis length of about three kpc, together with a multi-armed spiral pattern represented by a superposition of m= 2-, 3-, and 4-armed spirals. The spiral structure and the bar exist for at least 3 Gyr in our simulations. The existence of the Milky Way bar imposes limitations on the density distributions in the subsystems of the Milky Way galaxy. We find that a bar does not form if the radial scale length of the density distribution in the disk exceeds 2.6 kpc. As expected, the bar formation is also suppressed by a compact massive stellar bulge. We also demonstrate that the maximum value in the rotation curve of the disk of the Milky Way galaxy, as found in its central regions, is explained by non-circular motion due to the presence of a bar and its orientation relative to an observer. Full article
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Article
History of Astronomy in Australia: Big-Impact Astronomy from World War II until the Lunar Landing (1945–1969)
Galaxies 2021, 9(2), 24; https://doi.org/10.3390/galaxies9020024 - 31 Mar 2021
Viewed by 1022
Abstract
Radio astronomy commenced in earnest after World War II, with Australia keenly engaged through the Council for Scientific and Industrial Research. At this juncture, Australia’s Commonwealth Solar Observatory expanded its portfolio from primarily studying solar phenomena to conducting stellar and extragalactic research. Subsequently, [...] Read more.
Radio astronomy commenced in earnest after World War II, with Australia keenly engaged through the Council for Scientific and Industrial Research. At this juncture, Australia’s Commonwealth Solar Observatory expanded its portfolio from primarily studying solar phenomena to conducting stellar and extragalactic research. Subsequently, in the 1950s and 1960s, astronomy gradually became taught and researched in Australian universities. However, most scientific publications from this era of growth and discovery have no country of affiliation in their header information, making it hard to find the Australian astronomy articles from this period. In 2014, we used the then-new Astrophysics Data System (ADS) tool Bumblebee to overcome this challenge and track down the Australian-led astronomy papers published during the quarter of a century after World War II, from 1945 until the lunar landing in 1969. This required knowledge of the research centres and facilities operating at the time, which are briefly summarised herein. Based on citation counts—an objective, universally-used measure of scientific impact—we report on the Australian astronomy articles which had the biggest impact. We have identified the top-ten most-cited papers, and thus also their area of research, from five consecutive time-intervals across that blossoming quarter-century of astronomy. Moreover, we have invested a substantial amount of time researching and providing a small tribute to each of the 62 scientists involved, including several trail-blazing women. Furthermore, we provide an extensive list of references and point out many interesting historical connections and anecdotes. Full article
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Article
Neutrino Charge in a Magnetized Media
Galaxies 2021, 9(2), 22; https://doi.org/10.3390/galaxies9020022 - 30 Mar 2021
Viewed by 532
Abstract
In the presence of a thermal medium or an external electro-magnetic field, neutrinos can interact with photon, mediated by the corresponding charged leptons (real or virtual). The effect of a medium or an electromagnetic field is two-fold—to induce an effective νγ vertex and to modify the dispersion relations of all the particles involved to render the processes kinematically viable. It has already been noted that, in a medium, neutrinos acquire an effective charge, which in the standard model of electroweak interaction comes from the vector type vertex of weak interaction. On the other hand, in a magnetized plasma, the axial vector part also starts contributing to the effective charge of a neutrino. This contribution corresponding to the axial vector part in the interaction Lagrangian is denoted as the axial polarisation tensor. In this note, we outline the calculation of the axial polarization tensor to odd and even powers in eB. We further show its gauge invariance properties. Finally, we infer upon the zero external momentum limit of this axial polarisation tensor. Full article
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Article
A Possible Quasi-Periodic Oscillation in the X-ray Emission of 3C 120
Galaxies 2021, 9(2), 20; https://doi.org/10.3390/galaxies9020020 - 25 Mar 2021
Viewed by 568
Abstract
We present here the detection of a possible quasi-periodic oscillation (QPO) signal in the X-ray light curve of the active galactic nucleus 3C 120, a broad line radio galaxy at z = 0.033. The hint of a QPO at the 3σ level at 7.1 × 106 Hz (∼1.65 days) was detected based on the analysis of X-ray data acquired in the 3–79 keV band by the Nuclear Spectroscopic Telescope Array (NuSTAR). The data, when processed separately in the soft (3–10 keV), hard (10–79 keV) and the total (3–79 keV) bands using four different techniques, namely discrete correlation function, Lomb Scargle periodogram, structure–function, and power spectral density indicated the presence of a QPO. 3C 120 very well fits in the negative correlation in the frequency of the QPO versus the black hole mass (FQPO versus MBH) diagram known for stellar-mass and supermassive black hole sources. Considering the observed signs of QPO to represent the innermost stable orbit of the accretion disk, we found a black hole mass of 1.9×109 M for a Kerr black hole and 3.04×108 M for a Schwarzschild black hole. This deduced black hole mass from QPO measurement is a few times larger than the black hole mass obtained from reverberation mapping observations. Full article
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Article
The Dirac Electron Consistent with Proper Gravitational and Electromagnetic Field of the Kerr–Newman Solution
Galaxies 2021, 9(1), 18; https://doi.org/10.3390/galaxies9010018 - 17 Mar 2021
Viewed by 631
Abstract
The Dirac electron is considered as a particle-like solution consistent with its own Kerr–Newman (KN) gravitational field. In our previous works we considered the regularized by López KN solution as a bag-like soliton model formed from the Higgs field in a supersymmetric vacuum [...] Read more.
The Dirac electron is considered as a particle-like solution consistent with its own Kerr–Newman (KN) gravitational field. In our previous works we considered the regularized by López KN solution as a bag-like soliton model formed from the Higgs field in a supersymmetric vacuum state. This bag takes the shape of a thin superconducting disk coupled with circular string placed along its perimeter. Using the unique features of the Kerr–Schild coordinate system, which linearizes Dirac equation in KN space, we obtain the solution of the Dirac equations consistent with the KN gravitational and electromagnetic field, and show that the corresponding solution takes the form of a massless relativistic string. Obvious parallelism with Heisenberg and Schrödinger pictures of quantum theory explains remarkable features of the electron in its interaction with gravity and in the relativistic scattering processes. Full article
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Article
Black Holes and Other Clues to the Quantum Structure of Gravity
Galaxies 2021, 9(1), 16; https://doi.org/10.3390/galaxies9010016 - 25 Feb 2021
Cited by 1 | Viewed by 597
Abstract
Bringing gravity into a quantum-mechanical framework is likely the most profound remaining problem in fundamental physics. The “unitarity crisis” for black hole evolution appears to be a key facet of this problem, whose resolution will provide important clues. Investigating this raises the important [...] Read more.
Bringing gravity into a quantum-mechanical framework is likely the most profound remaining problem in fundamental physics. The “unitarity crisis” for black hole evolution appears to be a key facet of this problem, whose resolution will provide important clues. Investigating this raises the important structural question of how to think about subsystems and localization of information in quantum gravity. Paralleling field theory, the answer to this is expected to be an important ingredient in the mathematical structure of the theory. Perturbative gravity results indicate a structure different from that of quantum field theory, but suggest an avenue to defining subsystems. If black holes do behave similarly to familiar subsystems, unitarity demands new interactions that transfer entanglement from them. Such interactions can be parameterized in an effective approach, without directly addressing the question of the fundamental dynamics, whether that is associated with quantum spacetime, wormholes, or something else. Since such interactions need to extend outside the horizon, that raises the question of whether they can be constrained, or might be observed, by new electromagnetic or gravitational wave observations of strong gravity regions. This note overviews and provides connections between these developments. Full article
Review
Survey of CO2 Radiation Experimental Data in Relation with Planetary Entry
Galaxies 2021, 9(1), 15; https://doi.org/10.3390/galaxies9010015 - 23 Feb 2021
Viewed by 494
Abstract
This paper focuses on a survey of experimental data related to radiation into CO2 plasma flows, which are encountered during Mars and Venus entries. The review emphasizes on VUV and IR radiation, since recent experimental efforts has been devoted to these wavelength [...] Read more.
This paper focuses on a survey of experimental data related to radiation into CO2 plasma flows, which are encountered during Mars and Venus entries. The review emphasizes on VUV and IR radiation, since recent experimental efforts has been devoted to these wavelength ranges since they contribute mostly to CO2 plasma radiation. The main objective of the study is to identify the most attractive datasets for future crosscheck comparisons with the results obtained during future test campaigns with ESTHER shock-tube. The survey accounts for the results obtained in shock-tubes, expansion tube and plasma arc-jets for Mars and Venus test campaigns. The experimental results obtained for propulsion related studies have also been considered. Full article
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Article
Dark Supernova Remnants Revealed by CO-Line Bubbles in the W43 Molecular Complex along the 4-kpc Galactic Arm
Galaxies 2021, 9(1), 13; https://doi.org/10.3390/galaxies9010013 - 04 Feb 2021
Viewed by 555
Abstract
Fine structure of the density distribution in giant molecular clouds (GMCs) around W43 (G31+00+90 km s1at ∼5.5 kpc) was analyzed using the FUGIN* CO-line survey at high-angular (20”∼0.5 pc) and velocity (1.3 km s1) resolutions (*Four-receiver-system Unbiased Galactic Imaging survey with the Nobeyama 45-m telescope). The GMCs show highly turbulent structures, and the eddies are found to exhibit spherical bubble morphology appearing in narrow ranges of velocity channels. The bubbles are dark in radio continuum emission, unlike usual supernova remnants (SNR) or HII regions, and in infrared dust emission, unlike molecular bubbles around young stellar objects. The CO bubbles are interpreted as due to fully evolved buried SNRs in molecular clouds after rapid exhaustion of the released energy in dense molecular clouds. Then, the CO bubbles may be a direct evidence for exciting and maintaining the turbulence in GMCs by SN origin. Search for CO bubbles as “dark SNRs” (dSNR) will have implication to estimate the supernova rate more accurately, and hence the star formation activity in the Milky Way. Full article
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Review
Radio Constraints of Dark Matter: A Review and Some Future Perspectives
Galaxies 2021, 9(1), 11; https://doi.org/10.3390/galaxies9010011 - 28 Jan 2021
Viewed by 697
Abstract
In the past few decades, many studies have analyzed the data of gamma-rays, X-rays, radio waves, electrons, positrons, anti-protons, and neutrinos to search for the signal of dark matter annihilation. In particular, analyzing radio data has been one of the most important and [...] Read more.
In the past few decades, many studies have analyzed the data of gamma-rays, X-rays, radio waves, electrons, positrons, anti-protons, and neutrinos to search for the signal of dark matter annihilation. In particular, analyzing radio data has been one of the most important and effective ways to constrain dark matter. In this article, we review the physics and the theoretical framework of using radio data to constrain annihilating dark matter. We also review some important radio constraints of annihilating dark matter and discuss the future perspectives of using radio detection to reveal the nature of dark matter. Full article
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Article
Gravitational Measurements in Higher Dimensions
Galaxies 2021, 9(1), 4; https://doi.org/10.3390/galaxies9010004 - 11 Jan 2021
Cited by 2 | Viewed by 851
Abstract
We attempt to study three significant tests of general relativity in higher dimensions, both in commutative and non-commutative spaces. In the context of non-commutative geometry, we will consider a solution of Einstein’s equation in higher dimensions, with a source given by a static, [...] Read more.
We attempt to study three significant tests of general relativity in higher dimensions, both in commutative and non-commutative spaces. In the context of non-commutative geometry, we will consider a solution of Einstein’s equation in higher dimensions, with a source given by a static, spherically symmetric Gaussian distribution of mass. The resulting metric would describe a regular or curvature singularity free black hole in higher dimensions. The metric should smoothly interpolate between Schwarzschild geometry at large distance, and de-Sitter spacetime at short distance. We will consider gravitational redshift, lensing, and time delay in each sector. It will be shown that, compared to the four-dimensional spacetime, there can be significant modifications due to the presence of extra dimensions and the non-commutative corrected black holes. Finally, we shall attempt to obtain a lower bound on the size of the extra dimensions and on the mass needed to form a black hole in different dimensions. Full article
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2020

Jump to: 2021

Review
Messengers of the Universe-Cosmic Rays Exploring Supermassive Black Holes
Galaxies 2021, 9(1), 2; https://doi.org/10.3390/galaxies9010002 - 29 Dec 2020
Viewed by 648
Abstract
Cosmic rays were discovered over one hundred years ago but there are still unsolved problems. One of the hot problems is the origin of cosmic rays of the highest energies. Sources are still unclear and it is neither clear how particles gain ultra-high [...] Read more.
Cosmic rays were discovered over one hundred years ago but there are still unsolved problems. One of the hot problems is the origin of cosmic rays of the highest energies. Sources are still unclear and it is neither clear how particles gain ultra-high energies. Possible sources of cosmic rays at the highest energies are supermassive black holes. From this perspective we discuss in a popular form some recent developments in cosmic ray studies along with author’s recent results. The paper also offers materials for further reading. Full article
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Article
Anomalous Sun Flyby of 1I/2017 U1 (`Oumuamua)
Galaxies 2020, 8(4), 83; https://doi.org/10.3390/galaxies8040083 - 07 Dec 2020
Cited by 1 | Viewed by 1067
Abstract
The findings of Micheli et al. (Nature2018, 559, 223–226) that 1I/2017 U1 (`Oumuamua) showed anomalous orbital accelerations have motivated us to apply an impact model of gravity in search for an explanation. A small deviation from the 1/r potential, where r is the heliocentric distance, is expected for the gravitational interaction of extended bodies as a consequence of this model. This modification of the potential results from an offset of the effective gravitational centre from the geometric centre of a spherically symmetric body. Applied to anomalous Earth flybys, the model accounts for energy gains relative to an exact Kepler orbit and an increased speed of several spacecraft. In addition, the flat rotation profiles of eight disk galaxies could be explained, as well as the anomalous perihelion advances of the inner planets and the asteroid Icarus. The solution in the case of `Oumuamua is also based on the proposal that the offset leads to an approach and flyby trajectory different from a Kepler orbit without postulating cometary activity. As a consequence, an adjustment of the potential and centrifugal orbital energies can be envisaged outside the narrow uncertainty ranges of the published post-perihelion data without a need to re-analyse the original data. The observed anomalous acceleration has been modelled with respect to the orbit solutions JPL 16 and “Pseudo-MPEC” for 1I/`Oumuamua. Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Planned Paper 1:

Tentative Title: Probing the central engine of bare Seyfert type 1 AGNs
Abstract: We present a detailed spectral and timing behaviour of a few bare active galactic nuclei using observations performed with the Neil Gehrels Swift Observatory.  Instruments onboard Swift mission are X-ray telescope (XRT) covering the 0.2-10 keV range and the Ultraviolet (UV)/Optical telescope covers simultaneously in 1900-6500 angstrom. In the X-ray range, normally, we find the soft X-ray excess below 2 keV and a big blue bump peaking in the UV regime. The origin of the soft excess is not well understood to date and this is expected either the cool Comptonization in the inner accretion disk or the blurred reflection from the partially ionized material close to the supermassive black hole. The UV/optical emission may play a crucial role to remove the ambiguity using either spectral energy distribution and timing information and the relationship with the X-ray emission. To do so, we will be applying the spectral models and cross-correlation techniques to investigate the origin of soft X-ray excess in the bare galaxies.

Planned Paper 2:

Tentative Title: On the origin and evolution of the Intra-Cluster Light: from its formation to its importance as a tracer of the dark matter in galaxy clusters
Abstract: Not all the light in galaxy groups and clusters comes from stars that are bound to galaxies. A significant fraction of it constitutes the so-called intracluster or diffuse light (ICL), a low surface brightness component of groups/clusters generally believed to be the envelop of the brightest cluster galaxies and  intermediate/massive satellites. In this review, I will address the mechanisms responsible for its formation and evolution, considering the large contribution given to the topic in the last decades by both the theoretical and observational sides. Starting from the methods that are commonly used to isolate the ICL, I will address the remarkable problem given by its own definition, which still makes the comparisons among different studies not trivial, to conclude by giving an overview of the most recent studies that take advantage of the ICL as a luminous tracer of the dark matter distribution in galaxy groups and clusters.

Author: Emanuele Contini

Affiliation: School of Astronomy and Space Science, Nanjing University

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