Remo Ruffini Festschrift

A special issue of Universe (ISSN 2218-1997).

Deadline for manuscript submissions: closed (30 April 2023) | Viewed by 10761

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Guest Editor
International Center for Relativistic Astrophysics Network (ICRANet), Piazza della Repubblica, 10, 65122 Pescara, Italy
Interests: GRBs; black holes; physics; relativistic astrophysics

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Guest Editor
1. International Center for Relativistic Astrophysics Network (ICRANet), Piazza della Repubblica, 10, 65122 Pescara, Italy
2. ICRANet-Ferrara, Dipartimento di Fisica, Università di Ferrara, Via Giuseppe Saragat 1, 44122 Ferrara, Italy
Interests: relativistic astrophysics

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Guest Editor
ICRANet-Armenia at NAS RA, Yerevan, Armenia
Interests: high energy astrophysics; astroparticle physics; data analysis of astrophysical data; numerical simulations

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Guest Editor
International Center for Relativistic Astrophysics Network (ICRANet), Piazza della Repubblica, 10, 65122 Pescara, Italy
Interests: kinetic theory; plasma physics; astrophysics; cosmology
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Special Issue Information

Dear Colleagues,

Remo Ruffini received his doctorate at Sapienza University of Rome, in 1967. Since then, he has become the director of ICRANet, the president of ICRA, and the coauthor of more than 650 scientific publications and 13 books. He has taught in Hamburg, at Princeton University, at the Institute for Advanced Study, in Japan, China (at USTC), Australia, and CBPF (Brazil). One of his major works concerned boson stars, named, “Introducing the Black Hole” with J.A. Wheeler, which focused on the limiting critical mass of NS. He identified the first black hole (BH) in our galaxy (Cignus X-1) using UHURU satellite data with Riccardo Giacconi and consequentially, he received the Cressy Morrison Award in 1973. He returned to Sapienza University in 1978, and he promoted a Rome–Stanford collaboration on the subject of gravitational wave detectors. Together with European, US, and Chinese institutions, he established ICRA and later ICRANet, in Italy, Armenia, France, and Brazil in 2005. He developed the understanding of GRBs, confirmed by the largest telescopes on Earth from their discovery in 1973, to their cosmological origin in 1997, and to the determination of seven different GRB families and their conceptual understanding in 2018.

This Special Issue will collect original and review papers written by distinguished scholars and dedicated to Remo Ruffini on the above mentioned topics.

The deadline for paper submission is April 30, 2023.

Prof. Dr. Remo Ruffini
Prof. Dr. Jorge Armando Rueda Hernández
Prof. Dr. Narek Sahakyan
Prof. Dr. Gregory Vereshchagin
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Universe is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • black holes
  • energy extraction from black holes
  • neutron stars
  • gamma-ray bursts: supernovae: binary-driven hypernovae
  • gravitational waves
  • cosmology
  • dark matter
  • galactic halos
  • pair creation

Published Papers (11 papers)

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Research

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12 pages, 276 KiB  
Article
Spherically Symmetric C3 Matching in General Relativity
by Hernando Quevedo
Universe 2023, 9(9), 419; https://doi.org/10.3390/universe9090419 - 14 Sep 2023
Viewed by 783
Abstract
We study the problem of matching interior and exterior solutions to Einstein’s equations along a particular hypersurface. We present the main aspects of the C3 matching approach that involve third-order derivatives of the corresponding metric tensors in contrast to the standard [...] Read more.
We study the problem of matching interior and exterior solutions to Einstein’s equations along a particular hypersurface. We present the main aspects of the C3 matching approach that involve third-order derivatives of the corresponding metric tensors in contrast to the standard C2 matching procedures known in general relativity, which impose conditions on the second-order derivatives only. The C3 alternative approach does not depend on coordinates and allows us to determine the matching surface by using the invariant properties of the eigenvalues of the Riemann curvature tensor. As a particular example, we apply the C3 procedure to match the exterior Schwarzschild metric with a general spherically symmetric interior spacetime with a perfect fluid source and obtain that on the matching hypersurface, the density and pressure should vanish, which is in accordance with the intuitive physical expectation. Full article
(This article belongs to the Special Issue Remo Ruffini Festschrift)
7 pages, 924 KiB  
Communication
Binary Neutron-Star Mergers with a Crossover Transition to Quark Matter
by Grant J. Mathews, Atul Kedia, Hee Il Kim and In-Saeng Suh
Universe 2023, 9(9), 410; https://doi.org/10.3390/universe9090410 - 07 Sep 2023
Viewed by 886
Abstract
This paper summarizes recent work on the possible gravitational-wave signal from binary neutron-star mergers in which there is a crossover transition to quark matter. Although this is a small piece of a much more complicated problem, we discuss how the power spectral density [...] Read more.
This paper summarizes recent work on the possible gravitational-wave signal from binary neutron-star mergers in which there is a crossover transition to quark matter. Although this is a small piece of a much more complicated problem, we discuss how the power spectral density function may reveal the presence of a crossover transition to quark matter. Full article
(This article belongs to the Special Issue Remo Ruffini Festschrift)
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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 1024
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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12 pages, 960 KiB  
Article
Estimates of the Surface Magnetic Field Strength of Radio Pulsars
by Vitaliy Kim, Adel Umirbayeva and Yerlan Aimuratov
Universe 2023, 9(7), 334; https://doi.org/10.3390/universe9070334 - 14 Jul 2023
Viewed by 876
Abstract
We investigate the geometry of the magnetic field of rotation-powered pulsars. A new method for calculating an angle (β) between the spin and magnetic dipole axes of a neutron star (NS) in the ejector stage is considered within the frame of [...] Read more.
We investigate the geometry of the magnetic field of rotation-powered pulsars. A new method for calculating an angle (β) between the spin and magnetic dipole axes of a neutron star (NS) in the ejector stage is considered within the frame of the magnetic dipole energy loss mechanism. We estimate the surface magnetic field strength (Bns) for a population of known neutron stars in the radio pulsar (ejector) stage. The evaluated Bns(β) may differ by an order of magnitude from the values without considering the angle β. It is shown that Bns(β) lies in the range 1081014G for a known population of short and middle periodic radio pulsars. Full article
(This article belongs to the Special Issue Remo Ruffini Festschrift)
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12 pages, 855 KiB  
Article
Neutron Star Binaries Produced by Binary-Driven Hypernovae, Their Mergers, and the Link between Long and Short GRBs
by Laura M. Becerra, Chris Fryer, Jose F. Rodriguez, Jorge A. Rueda and Remo. Ruffini
Universe 2023, 9(7), 332; https://doi.org/10.3390/universe9070332 - 12 Jul 2023
Viewed by 726
Abstract
The binary-driven hypernova (BdHN) model explains long gamma-ray bursts (GRBs) associated with supernovae (SNe) Ic through physical episodes that occur in a binary composed of a carbon-oxygen (CO) star and a neutron star (NS) companion in close orbit. The CO core collapse triggers [...] Read more.
The binary-driven hypernova (BdHN) model explains long gamma-ray bursts (GRBs) associated with supernovae (SNe) Ic through physical episodes that occur in a binary composed of a carbon-oxygen (CO) star and a neutron star (NS) companion in close orbit. The CO core collapse triggers the cataclysmic event, originating the SN and a newborn NS (hereafter νNS) at its center. The νNS and the NS accrete SN matter. BdHNe are classified based on the NS companion fate and the GRB energetics, mainly determined by the orbital period. In BdHNe I, the orbital period is of a few minutes, so the accretion causes the NS to collapse into a Kerr black hole (BH), explaining GRBs of energies >1052 erg. BdHN II, with longer periods of tens of minutes, yields a more massive but stable NS, accounting for GRBs of 10501052 erg. BdHNe III have still longer orbital periods (e.g., hours), so the NS companion has a negligible role, which explains GRBs with a lower energy release of <1050 erg. BdHN I and II might remain bound after the SN, so they could form NS-BH and binary NS (BNS), respectively. In BdHN III, the SN likely disrupts the system. We perform numerical simulations of BdHN II to compute the characteristic parameters of the BNS left by them, their mergers, and the associated short GRBs. We obtain the mass of the central remnant, whether it is likely to be a massive NS or a BH, the conditions for disk formation and its mass, and the event’s energy release. The role of the NS nuclear equation of state is outlined. Full article
(This article belongs to the Special Issue Remo Ruffini Festschrift)
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16 pages, 3747 KiB  
Article
A Wheeler–DeWitt Quantum Approach to the Branch-Cut Gravitation with Ordering Parameters
by Benno August Ludwig Bodmann, César Augusto Zen Vasconcellos, Peter Otto Hess Bechstedt, José Antonio de Freitas Pacheco, Dimiter Hadjimichef, Moisés Razeira and Gervásio Annes Degrazia
Universe 2023, 9(6), 278; https://doi.org/10.3390/universe9060278 - 08 Jun 2023
Cited by 5 | Viewed by 912
Abstract
In this contribution to the Festschrift for Prof. Remo Ruffini, we investigate a formulation of quantum gravity using the Hořava–Lifshitz theory of gravity, which is General Relativity augmented by counter-terms to render the theory regularized. We are then led to the Wheeler–DeWitt (WDW) [...] Read more.
In this contribution to the Festschrift for Prof. Remo Ruffini, we investigate a formulation of quantum gravity using the Hořava–Lifshitz theory of gravity, which is General Relativity augmented by counter-terms to render the theory regularized. We are then led to the Wheeler–DeWitt (WDW) equation combined with the classical concepts of the branch-cut gravitation, which contemplates as a new scenario for the origin of the Universe, a smooth transition region between the contraction and expansion phases. Through the introduction of an energy-dependent effective potential, which describes the space-time curvature associated with the embedding geometry and its coupling with the cosmological constant and matter fields, solutions of the WDW equation for the wave function of the Universe are obtained. The Lagrangian density is quantized through the standard procedure of raising the Hamiltonian, the helix-like complex scale factor of branched gravitation as well as the corresponding conjugate momentum to the category of quantum operators. Ambiguities in the ordering of the quantum operators are overcome with the introduction of a set of ordering factors α, whose values are restricted, to make contact with similar approaches, to the integers α=[0,1,2], allowing this way a broader class of solutions for the wave function of the Universe. In addition to a branched universe filled with underlying background vacuum energy, primordial matter and radiation, in order to connect with standard model calculations, we additionally supplement this formulation with baryon matter, dark matter and quintessence contributions. Finally, the boundary conditions for the wave function of the Universe are imposed by assuming the Bekenstein criterion. Our results indicate the consistency of a topological quantum leap, or alternatively a quantum tunneling, for the transition region of the early Universe in contrast to the classic branched cosmology view of a smooth transition. Full article
(This article belongs to the Special Issue Remo Ruffini Festschrift)
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10 pages, 903 KiB  
Article
Magnetized Black Holes: Interplay between Charge and Rotation
by Vladimír Karas and Zdeněk Stuchlík
Universe 2023, 9(6), 267; https://doi.org/10.3390/universe9060267 - 03 Jun 2023
Cited by 4 | Viewed by 743
Abstract
Already in the cornerstone works on astrophysical black holes published as early as in the 1970s, Ruffini and collaborators have revealed the potential importance of an intricate interaction between the effects of strong gravitational and electromagnetic fields. Close to the event horizon of [...] Read more.
Already in the cornerstone works on astrophysical black holes published as early as in the 1970s, Ruffini and collaborators have revealed the potential importance of an intricate interaction between the effects of strong gravitational and electromagnetic fields. Close to the event horizon of the black hole, magnetic and electric lines of force become distorted and dragged even in a purely electro-vacuum system. Moreover, as the plasma effects inevitably arise in any astrophysically realistic environment, particles of different electric charges can separate from each other, become accelerated away from the black hole or accreted onto it, and contribute to the net electric charge of the black hole. From the point of principle, the case of super-strong magnetic fields is of particular interest, as the electromagnetic field can act as a source of gravity and influence spacetime geometry. In a brief celebratory note, we revisit aspects of rotation and charge within the framework of exact (asymptotically non-flat) solutions of mutually coupled Einstein–Maxwell equations that describe magnetized, rotating black holes. Full article
(This article belongs to the Special Issue Remo Ruffini Festschrift)
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Review

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10 pages, 413 KiB  
Review
Eclipses: A Brief History of Celestial Mechanics, Astrometry and Astrophysics
by Costantino Sigismondi and Paolo De Vincenzi
Universe 2024, 10(2), 90; https://doi.org/10.3390/universe10020090 - 13 Feb 2024
Viewed by 1054
Abstract
Solar and lunar eclipses are indeed the first astronomical phenomena which have been recorded since very early antiquity. Their periodicities gave birth to the first luni-solar calendars based on the Methonic cycle since the sixth century before Christ. The Saros cycle of 18.03 [...] Read more.
Solar and lunar eclipses are indeed the first astronomical phenomena which have been recorded since very early antiquity. Their periodicities gave birth to the first luni-solar calendars based on the Methonic cycle since the sixth century before Christ. The Saros cycle of 18.03 years is due to the Chaldean astronomical observations. Their eclipses’ observations reported by Ptolemy in the Almagest (Alexandria of Egypt, about 150 a.C.) enabled modern astronomers to recognize the irregular rotation rate of the Earth. The Earth’s rotation is some hours in delay after the last three millenia if we use the present rotation to simulate the 721 b.C. total eclipse in Babylon. This is one of the most important issues in modern celestial mechanics, along with the Earth’s axis nutation of 18 yr (discovered in 1737), precession of 25.7 Kyr (discovered by Ipparchus around 150 b.C.) and obliquity of 42 Kyr motions (discovered by Arabic astronomers and assessed from the Middle Ages to the modern era, IX to XVIII centuries). Newtonian and Einstenian gravitational theories explain fully these tiny motions, along with the Lense–Thirring gravitodynamic effect, which required great experimental accuracy. The most accurate lunar and solar theories, or their motion in analytical or numerical form, allow us to predict—along with the lunar limb profile recovered by a Japanese lunar orbiter—the appearance of total, annular solar eclipses or lunar occultations for a given place on Earth. The observation of these events, with precise timing, may permit us to verify the sphericity of the solar profile and its variability. The variation of the solar diameter on a global scale was claimed firstly by Angelo Secchi in the 1860s and more recently by Jack Eddy in 1978. In both cases, long and accurate observational campaigns started in Rome (1877–1937) and Greenwich Observatories, as well as at Yale University and the NASA and US Naval Observatory (1979–2011) with eclipses and balloon-borne heliometric observations. The IOTA/ES and US sections as well as the ICRA continued the eclipse campaigns. The global variations of the solar diameter over a decadal timescale, and at the millarcsecond level, may reflect some variation in solar energy output, which may explain some past climatic variations (such as the Allerød and Dryas periods in Pleistocene), involving the outer layers of the Sun. “An eclipse never comes alone”; in the eclipse season, lasting about one month, we can have also lunar eclipses. Including the penumbral lunar eclipses, the probability of occurrence is equi-distributed amongst lunar and solar eclipses, but while the lunar eclipses are visible for a whole hemisphere at once, the solar eclipses are not. The color of the umbral shadow on the Moon was known since antiquity, and Galileo (1632, Dialogo sopra i Massimi Sistemi del Mondo) shows clearly these phenomena from copper color to a totally dark, eclipsed full Moon. Three centuries later, André Danjon was able to correlate that umbral color with the 11-year cycle of solar activity. The forthcoming American total solar eclipse of 8 April 2024 will be probably the eclipse with the largest mediatic impact of the history; we wish that also the scientific impulse toward solar physics and astronomy will be relevant, and the measure of the solar diameter with Baily’s beads is indeed one of the topics significantly related to the Sun–Earth connections. Full article
(This article belongs to the Special Issue Remo Ruffini Festschrift)
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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 1 | Viewed by 875
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)
48 pages, 7424 KiB  
Review
A Short Survey of Matter-Antimatter Evolution in the Primordial Universe
by Johann Rafelski, Jeremiah Birrell, Andrew Steinmetz and Cheng Tao Yang
Universe 2023, 9(7), 309; https://doi.org/10.3390/universe9070309 - 27 Jun 2023
Cited by 4 | Viewed by 1054
Abstract
We offer a survey of the matter-antimatter evolution within the primordial Universe. While the origin of the tiny matter-antimatter asymmetry has remained one of the big questions in modern cosmology, antimatter itself has played a large role for much of the Universe’s early [...] Read more.
We offer a survey of the matter-antimatter evolution within the primordial Universe. While the origin of the tiny matter-antimatter asymmetry has remained one of the big questions in modern cosmology, antimatter itself has played a large role for much of the Universe’s early history. In our study of the evolution of the Universe we adopt the position of the standard model Lambda-CDM Universe implementing the known baryonic asymmetry. We present the composition of the Universe across its temperature history while emphasizing the epochs where antimatter content is essential to our understanding. Special topics we address include the heavy quarks in quark-gluon plasma (QGP), the creation of matter from QGP, the free-streaming of the neutrinos, the vanishing of the muons, the magnetism in the electron-positron cosmos, and a better understanding of the environment of the Big Bang Nucleosynthesis (BBN) producing the light elements. We suggest but do not explore further that the methods used in exploring the early Universe may also provide new insights in the study of exotic stellar cores, magnetars, as well as gamma-ray burst (GRB) events. We describe future investigations required in pushing known physics to its extremes in the unique laboratory of the matter-antimatter early Universe. Full article
(This article belongs to the Special Issue Remo Ruffini Festschrift)
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Other

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12 pages, 827 KiB  
Essay
Finding My Drumbeat: Applying Lessons Learned from Remo Ruffini to Understanding Astrophysical Transients
by Chris Fryer
Universe 2023, 9(6), 268; https://doi.org/10.3390/universe9060268 - 04 Jun 2023
Viewed by 732
Abstract
As with many fields from fashion to politics, science is susceptible to “bandwagon”-driven research where an idea becomes increasingly popular, garnering a growing amount of “scientific” support. Bandwagons allow scientists to converge on a solution, but when the prevailing bandwagon is incorrect or [...] Read more.
As with many fields from fashion to politics, science is susceptible to “bandwagon”-driven research where an idea becomes increasingly popular, garnering a growing amount of “scientific” support. Bandwagons allow scientists to converge on a solution, but when the prevailing bandwagon is incorrect or too simple, this rigid mentality makes it very difficult for scientists to find the right track. True scientific innovation often occurs through scientists willing to march to the beat of their own drum. Using examples in the field of astrophysical transients, this paper demonstrates the importance of supporting scientists in their quest to develop their own personal drumbeat. Full article
(This article belongs to the Special Issue Remo Ruffini Festschrift)
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