DOI: https://doi.org/10.1051/0004-6361/202347845

Pace, C. M., The Solution of the Einstein’s Equations in the Vacuum Region Surrounding a Spherically Symmetric Mass Distribution, published in Journal of Modern Physics, Volume 15 on August 2024.

 

In this article, we address the solution of the Einstein’s equations in the vacuum region surrounding a spherically symmetric mass distribution. There are two different types of mathematical solutions, depending on the value of a constant of integration. These two types of solutions are analysed from a physical point of view. The comparison with the linear theory limit is also considered. This leads to a new solution, different from the well known one. If one considers the observational data in the weak field limit this new solution is in agreement with the available data. While the traditional Schwarzschild solution is characterized by a horizon at r=2GM/c², no horizon exists in this new solution.

 

DOI: https://doi.org/10.4236/jmp.2024.159055

Pace, C. M., The Correct Reissner-Nordstrøm, Kerr and Kerr-Newman Metrics, published in Journal of Modern Physics, Volume 15 on September 2024.

 

In a very recent article of mine I have corrected the traditional derivation of the Schwarzschild metric thus arriving to formulate a correct Schwarzschild metric different from the traditional Schwarzschild metric. In this article, starting from this correct Schwarzschild metric, I also propose corrections to the other traditional Reissner-Nordstrøm, Kerr and Kerr-Newman metrics on the basis of the fact that these metrics should be equal to the correct Schwarzschild metric in the borderline case in which they reduce to the case described by this metric. In this way, we see that, like the correct Schwarzschild metric, also the correct Reissner-Nordstrøm, Kerr and Kerr-Newman metrics do not present any event horizon (and therefore do not present any black hole) unlike the traditional Reissner-Nordstrøm, Kerr and Kerr-Newman metrics.

 

DOI: https://doi.org/10.4236/jmp.2024.1510062

 

B Eslam Panah, B Hazarika, P Phukon, Thermodynamic Topology of Topological Black Hole in F(R)-ModMax Gravity’s Rainbow, published in Progress of Theoretical and Experimental Physics, Volume 2024, Issue 8, on August 2024.

 

In order to include the effect of high energy and topological parameters on black holes in F(R) gravity, we consider two corrections to this gravity: energy-dependent spacetime with different topological constants, and a nonlinear electrodynamics field. In other words, we combine F(R) gravity’s rainbow with ModMax nonlinear electrodynamics theory to see the effects of high energy and topological parameters on the physics of black holes. For this purpose, we first extract topological black hole solutions in F(R)-ModMax gravity’s rainbow. Then, by considering black holes as thermodynamic systems, we obtain thermodynamic quantities and check the first law of thermodynamics. The effect of the topological parameter on the Hawking temperature and the total mass of black holes is obvious. We also discuss the thermodynamic topology of topological black holes in F(R)-ModMax gravity’s rainbow using the off-shell free energy method. In this formalism, black holes are assumed to be equivalent to defects in their thermodynamic spaces. For our analysis, we consider two different types of thermodynamic ensembles. These are: fixed q ensemble and fixed ensemble. We take into account all the different types of curvature hypersurfaces that can be constructed in these black holes. The local and global topology of these black holes are studied by computing the topological charges at the defects in their thermodynamic spaces. Finally, in accordance with their topological charges, we classify the black holes into three topological classes with total winding numbers corresponding to -1,0, and 1. We observe that the topological classes of these black holes are dependent on the value of the rainbow function, the sign of the scalar curvature, and the choice of ensembles.

 

DOI: https://doi.org/10.1093/ptep/ptae116

J. Sedaghat, B. Eslam Panah, R. Moradi, S. M. Zebarjad & G. H. Bordbar, Quark stars in massive gravity might be candidates for the mass gap objects, published in European Physical Journal C 84 (2024) 259 on February 2024.

 

We have investigated the structural properties of strange quark stars (SQSs) in a modified theory of gravity known as massive gravity. In order to obtain the equation of state (EOS) of strange quark matter, we have employed a modified version of the Nambu–Jona-Lasinio model (MNJL) which includes a combination of NJL Lagrangian and its Fierz transformation by using weighting factors (1-α) and α. Additionally, we have also calculated dimensionless tidal deformability Λ in massive gravity. To constrain the allowed values of the parameters appearing in massive gravity, we have imposed the condition Λ_1.4M☉ ≤ 580. Notably, in the MNJL model, the value of α varies between zero and one. As α increases, the EOS becomes stiffer, and the value of Λ increases accordingly. We have demonstrated that by softening the EOS with increasing the bag constant, one can obtain objects in massive gravity that not only satisfy the constraint Λ_1.4M☉ ≤ 580, but they also fall within the unknown mass gap region (2.5 M_☉ - 5 M_☉). To establish that the obtained objects in this region are not black holes, we have calculated Schwarzschild radius, compactness, and Λ_MTOV in massive gravity.

 

DOI: https://doi.org/10.1140/epjc/s10052-024-12505-2

B. Eslam Panah, S. Zare & H. Hassanabadi, Accelerating AdS black holes in gravity’s rainbow, published in European Physical Journal C 84, 259 (2024) on March 2024.

 

Motivated by the effect of the energy of moving particles in C-metric, we first obtain exact accelerating black hole solutions in gravity’s rainbow. Then, we study the effects of gravity’s rainbow and C-metric parameters on the Ricci and Kretschmann scalars, and also the asymptotical behavior of this solution. Next, we indicate how different parameters of the obtained accelerating black holes in gravity’s rainbow affect thermodynamics quantities (such as the Hawking temperature, and entropy) and the local stability (by evaluating the heat capacity). In the following, we extract the geodesic equations to determine the effects of various parameters on photon trajectory in the vicinity of this black hole, as well as obtain the radius of the photon sphere and the corresponding critical impact parameter to gain insight into AdS black hole physics by adding the gravity’s rainbow to C-metric.

 

DOI: https://doi.org/10.1140/epjc/s10052-024-12624-w

Behzad Eslam Panah, Analytic Electrically Charged Black Holes in F(R)-ModMax Theory, published in Progress of Theoretical and Experimental Physics, Volume 2024, Issue 2, February 2024.

 

Motivated by a new model of nonlinear electrodynamics known as Modified Maxwell (ModMax) theory, an exact analytical solution for black holes is obtained by coupling ModMax nonlinear electrodynamics and F(R) gravity. Then, the effects of the system’s parameters (F(R)-ModMax gravity parameters) on the event horizons are analyzed. The obtained black hole thermodynamic properties in the F(R)-ModMax theory are investigated by extracting their thermodynamic quantities such as Hawking temperature, electric charge, electric potential, entropy, and also total mass. The first law of thermodynamics for the system under study is evaluated. Next, by considering these black holes, the impacts of various parameters on both the local stability and global stability are investigated by examining the heat capacity and the Helmholtz free energy, respectively. Finally, the thermodynamic geometry of the black hole in F(R)-ModMax gravity is investigated by applying the Hendi–Panahiyan–Eslam Panah–Momennia thermodynamic metric (HPEM’s metric).

 

DOI: https://doi.org/10.1093/ptep/ptae012

Kh Jafarzade, B Eslam Panah and M E Rodrigues, Thermodynamics and optical properties of phantom AdS black holes in massive gravity, published in Classical and Quantum Gravity, Volume 41, Number 6 on February 2024.

 

Motivated by high interest in Lorentz invariant massive gravity models known as dRGT massive gravity, we present an exact phantom black hole solution in this theory of gravity and discuss the thermodynamic structure of the black hole in the canonical ensemble. Calculating the conserved and thermodynamic quantities, we check the validity of the first law of thermodynamics and the Smarr relation in the extended phase space. In addition, we investigate both the local and global stability of these black holes and show how massive parameters affect the regions of stability. We extend our study to investigate the optical features of the black holes such as the shadow geometrical shape, energy emission rate, and deflection angle. Also, we discuss how these optical quantities are affected by massive coefficients. Finally, we consider a massive scalar perturbation minimally coupled to the background geometry of the black hole and examine the quasinormal modes by employing the WKB approximation.

 

DOI: https://doi.org/10.1088/1361-6382/ad242e

A. Bagheri Tudeshki, G.H. Bordbar, B. Eslam Panah, Effect of rainbow function on the structural properties of dark energy star, published in Physics Letters B Volume 848 on January 2024.

 

Confirming the existence of compact objects with a mass greater than 2.5 M☉ by observational results such as GW190814 makes that is possible to provide theories to justify these observational results using modified gravity. This motivates us to use gravity's rainbow, which is the appropriate case for dense objects, to investigate the dark energy star structure as a suggested alternative case to the mass gap between neutron stars and black holes in the perspective of quantum gravity. Hence, in the present work, we derive the modified hydrostatic equilibrium equation for an anisotropic fluid, represented by the extended Chaplygin equation of state in gravity's rainbow. Then, for two isotropic and anisotropic cases, using the numerical solution, we obtain energy-dependent maximum mass and its corresponding radius, and the other properties of the dark energy star including the pressure, energy density, stability, etc. In the following, using the observational data, we compare the obtained results in two frameworks of general relativity and gravity's rainbow.

 

DOI: https://doi.org/10.1016/j.physletb.2023.138333

B. Eslam Panah, K. Jafarzade & Á. Rincón, Three-dimensional AdS black holes in massive-power-Maxwell theory, published in General Relativity and Gravitation, Volume 56, article number 46, on April 2024.

 

Recently, it was shown that the power-Maxwell (PM) theory could remove the singularity of the electric field (B. Eslam Panah, Europhys. Lett. 134, 20005 (2021). Motivated by a great interest in three-dimensional black holes and a surge of success in studying massive gravity from both the cosmological and astrophysical points of view, we investigate three-dimensional black hole solutions in de Rham, Gabadadze, and Tolley massive theory of gravity in the presence of PM electrodynamics. First, we extract exact three-dimensional solutions in this theory of gravity. Then we study the geometrical properties of these solutions. Calculating conserved and thermodynamic quantities, we check the validity of the first law of thermodynamics for these black holes. We also examine the stability of these black holes in the context of the canonical ensemble. We continue calculating this kind of black hole’s optical features, such as the photon orbit radius, the energy emission rate, and the deflection angle. Considering these optical quantities, finally, we analyze the effective role of the parameters of models on them.

 

DOI: https://doi.org/10.1007/s10714-024-03229-5

Shakeri, Soroush; Karkevandi, Davood RafieI, Bosonic dark matter in light of the NICER precise mass-radius measurements, published in Physical Review D, Volume 109, Issue 4 on February 2024.

 

We explore the presence of self-interacting bosonic dark matter (DM) within neutron stars (NSs) in light of the latest multimessenger observations of the Neutron Star Interior Composition Explorer (NICER) and LIGO/Virgo detectors. The bosonic DM is distributed as a core inside the NS or as a halo around it leading to formation of a DM admixed NS. We focus on the variation of the visible and dark radius of the mixed object due to DM model parameters and fractions. It is shown that DM core formation reduces the visible radius and the total mass pushing them below observational limits while halo formation is in favor of the latest mass-radius observations. Moreover, we scan over the parameter space of the bosonic DM model considering two nuclear matter equation of states by applying the radius, maximum mass and tidal deformability constraints. Our investigation allows for the exclusion of a range of DM fractions, self-coupling constant and sub-GeV boson masses, which limits the amount of accumulated DM to relatively low values to be consistent with astrophysical bounds. In this paper, we introduce main features of the pulse profile corresponding to the DM admixed NS as a novel observable quantity. We find that the depth of minimum fluxes in the pulse profiles crucially depends on the amount of DM around NS and its compactness. The current/future astrophysics missions may test for the possibility of the existence of DM within NSs and break the degeneracies between different scenarios via multiple observations.

 

DOI: https://doi.org/10.1103/PhysRevD.109.043029

Sigismondi, Costantino; De Vincenzi, Paolo, Eclipses: A Brief History of Celestial Mechanics, Astrometry and Astrophysics, published in Universe, Volume 10, Issue 2 on February 2024.

 

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.

 

DOI: https://doi.org/10.3390/universe10020090

Prakapenia, Mikalai; Vereshchagin, Gregory, Pair Creation in Hot Electrosphere of Compact Astrophysical Objects, published in The Astrophysical Journal, Volume 963, Issue 2 on March 2024.

 

The mechanism of pair creation in the electrosphere of compact astrophysical objects such as quark stars or neutron stars is revisited, paying attention to evaporation of electrons and acceleration of electrons and positrons, which were previously not addressed in the literature. We perform a series of numerical simulations using the Vlasov–Maxwell equations. The rate of pair creation strongly depends on electric field strength in the electrosphere. Although Pauli blocking is explicitly taken into account, we find no exponential suppression of the pair creation rate at low temperatures. The luminosity in pairs increases with temperature and it may reach up to L _± ∼ 10⁵² erg s^‑1, much larger than previously assumed.

 

DOI: https://doi.org/10.3847/1538-4357/ad24ee

Rafiei Karkevandi, Davood; Shahrbaf, Mahboubeh; Shakeri, Soroush; Typel, Stefan, Exploring the Distribution and Impact of Bosonic Dark Matter in Neutron Stars, published in Particles, Volume 7, Issue 1 on March 2024.

 

The presence of dark matter (DM) within neutron stars (NSs) can be introduced by different accumulation scenarios in which DM and baryonic matter (BM) may interact only through the gravitational force. In this work, we consider asymmetric self-interacting bosonic DM, which can reside as a dense core inside the NS or form an extended halo around it. It is seen that depending on the boson mass (mχ), self-coupling constant (λ) and DM fraction (Fχ), the maximum mass, radius and tidal deformability of NSs with DM admixture will be altered significantly. The impact of DM causes some modifications in the observable features induced solely by the BM component. Here, we focus on the widely used nuclear matter equation of state (EoS) called DD2 for describing NS matter. We show that by involving DM in NSs, the corresponding observational parameters will be changed to be consistent with the latest multi-messenger observations of NSs. It is seen that for mχ≳200 MeV and λ≲2π, DM-admixed NSs with 4%≲Fχ≲20% are consistent with the maximum mass and tidal deformability constraints.

DOI: https://doi.org/10.3390/particles7010011

Millauro, C. ; Argüelles, C. R.; Vieyro, F. L.; Crespi, V.; Mestre, M. F., Accretion discs onto supermassive compact objects: A portal to dark matter physics in active galaxies, published in Astronomy & Astrophysics, Volume 685 on May 2024.

 

Context. The study of the physics of the accretion discs that develop around supermassive black hole (BH) candidates provides essential theoretical tools to test their nature. Aims: Here, we study the accretion flow and associated emission using generalised α-discs accreting onto horizonless dark compact objects in order to make comparisons with the traditional BH scenario. The BH alternative proposed here consists in a dense and highly degenerate core made of fermionic dark matter (DM) and surrounded by a more diluted DM halo. This dense core-diluted halo DM configuration is a solution of Einstein's equation of general relativity (GR) in spherical symmetry, which naturally arises once the quantum nature of the DM fermions is duly accounted for. Methods: The methodology followed in this work consists in first generalising the theory of α-discs to work in the presence of regular and horizonless compact objects, and then applying it to the case of core-halo DM profiles typical of active-like galaxies. Results: The fact that the compactness of the dense and transparent DM core scales with particle mass allows the following key findings of this work: (i) There is always a given core compacity - corresponding particle mass - that produces a luminosity spectrum that is almost indistinguishable from that of a Schwarzschild BH of the same mass as the DM core. (ii) The disc can enter deep inside the non-rotating DM core, allowing accretion-powered efficiencies of as high as 28%, which is comparable to that of a highly rotating Kerr BH. Conclusions: These results, together with the existence of a critical DM core mass of collapse into a supermassive BH, open new avenues of research for two seemingly unrelated topics: AGN phenomenology and dark matter physics.

DOI: https://doi.org/10.1051/0004-6361/202348461

Punsly, B., First image of a jet launching from a black hole accretion system: Kinematics, published in Astronomy & Astrophysics, Volume 685 on May 2024.

 

Jets are endemic to both Galactic solar mass and extragalactic supermassive black holes. A recent 86 GHz image of M 87 shows a jet emerging from the accretion ring around a black hole, providing the first direct observational constraint on the kinematics of the jet-launching region in any black hole jetted system. The very wide (∼280 μas), highly collimated, limb-brightened cylindrical jet base is not predicted in current numerical simulations. The emission was shown to be consistent with that of a thick-walled cylindrical source that apparently feeds the flow that produces the bright limbs of the outer jet at an axial distance downstream of 0.4 mas < z < 0.65 mas. The analysis here applies the conservation laws of energy, angular momentum, and magnetic flux to the combined system of the outer jet, the cylindrical jet, and the launch region. It also uses the brightness asymmetries of the jet and counterjet to constrain the Doppler factor. The only global solutions have a source that is located < 34 μas from the event horizon. This includes the Event Horizon Telescope annulus of emission and the regions interior to this annulus. The axial jet begins as a magnetically dominated flow that spreads laterally from the launch radius (< 34 μas). It becomes super-magnetosonic before it reaches the base of the cylindrical jet. The flow is ostensibly redirected and collimated by a cylindrical nozzle formed in a thick accretion disk. The flow emerges from the nozzle as a mildly relativistic (0.3c < v < 0.4c) jet with a significant protonic kinetic energy flux.

 

DOI: https://doi.org/10.1051/0004-6361/202449956

Bianco, C. L.; Mirtorabi, M. T.; Moradi, R.; Rastegarnia, F.; Rueda, J. A.; Ruffini, R.; Wang, Y.; Della Valle, M.; Li, Liang; Zhang, S. R., Probing Electromagnetic Gravitational-wave Emission Coincidence in a Type I Binary-driven Hypernova Family of Long Gamma-Ray Bursts at Very High Redshift, published in The Astrophysical Journal, Volume 966, Issue 2 on May 2024.

 

The repointing time of the X-Ray Telescope (XRT) instrument on the Neil Gehrels Swift Observatory satellite has posed challenges in observing and studying the early X-ray emissions within ≈40 s after a gamma-ray burst (GRB) trigger. To address this issue, we adopt a novel approach that capitalizes on the cosmological time dilation in GRBs with redshifts ranging from 3 to 9. Applying this strategy to Swift/XRT data, we investigate the earliest X-ray emissions of 368 GRBs from the Swift catalog, including short and long GRBs. We compare the observed time delay between the GRB trigger and the initial Swift/XRT observation, measured in the GRB observer frame, and the corresponding cosmological rest-frame time delay (RTD). This technique is here used in the analysis of GRB 090423 at z = 8.233 (RTD ∼8.2 s), GRB 090429B at z ≈ 9.4 (RTD ∼10.1 s), and GRB 220101A at z = 4.61 (RTD ∼14.4 s). The cosmological time dilation enables us to observe the very early X-ray afterglow emission in these three GRBs. We thus validate the observation of the collapse of the carbon–oxygen core and the coeval newborn neutron star (νNS) formation triggering the GRB event in the binary-driven hypernova (BdHN) scenario. We also evidence the νNS spin-up due to supernova ejecta fallback and its subsequent slowing down due to the X-ray/optical/radio synchrotron afterglow emission. A brief gravitational-wave signal may separate the two stages owing to a fast-spinning νNS triaxial-to-axisymmetric transition. We also analyze the long GRB redshift distribution for the different BdHN types and infer that BdHNe II and III may originate the NS binary progenitors of short GRBs.

DOI: https://doi.org/10.3847/1538-4357/ad2fa9

Gao, Li-Yang ; Xue, She-Sheng ; Zhang, Xin, Dark energy and matter interacting scenario to relieve H 0 and S8 tensions, published in Chinese Physics C, Volume 48, Issue 5 on May 2024.

 

We consider a new cosmological model (called ΛCDM), in which the vacuum energy interacts with matter and radiation, and test this model using the current cosmological observations. Using the CMB+BAO+SN (CBS) dataset to constrain the model, we find that H₀ and S₈ tensions are relieved to 2.87σ and 2.77σ, respectively. However, in this case, the ΛCDM model is not favored by the data, compared with ΛCDM. We find that when the H₀ and S₈ data are added to the data combination, the situation is significantly improved. In the CBS+ H0 case, the model relieves the H0 tension to 0.47σ, and the model is favored over ΛCDM. In the CBS+ H0 + S8 case, we obtain a synthetically best situation, in which the H₀ and S₈ tensions are relieved to 0.72σ and 2.11σ, respectively. In this case, the model is most favored by the data. Therefore, this cosmological model can greatly relieve the H₀ tension and simultaneously effectively alleviate the S₈ tension.

DOI: https://doi.org/10.48550/arXiv.2212.13146

Xue, She-Sheng, Holographic massive plasma state in Friedman universe: cosmological fine-tuning and coincidence problems, published in Journal of Cosmology and Astroparticle Physics, Volume 2024, Issue 05 on May 2024.

 

Massive particle and antiparticle pair production and oscillation on the horizon form a holographic and massive pair plasma state in the Friedman Universe. Via this state, the Einstein cosmology term (dark energy) interacts with matter and radiation and is time-varying Λ̃ in the Universe's evolution. It is determined by a close set of ordinary differential equations for dark energy, matter, and radiation energy densities. The solutions are unique, provided the initial conditions given by observations. In inflation and reheating, dark energy density decreases from the inflation scale, converting to matter and radiation energy densities. In standard cosmology, matter and radiation energy densities convert to dark energy density, reaching the present Universe. By comparing with ΛCDM, quintessence and dark energy interacting models, we show that these results can be the possible solutions for cosmological fine-tuning and coincidence problems.

DOI: https://doi.org/10.1088/1475-7516/2024/05/113

Mahmoudi, Somayyeh; Sadegh, Mahdi; Khodagholizadeh, Jafar; Motie, Iman; Xue, She-Sheng; Blanchard, Alain, Generation of the CMB cosmic birefringence through axion-like particles, sterile and active neutrinos, published in The European Physical Journal C, Volume 84, Issue 6 on June 2024.

 

The cosmic birefringence (CB) angle refers to the rotation of the linear polarization plane of Cosmic Microwave Background (CMB) radiations when parity-violating theories are considered. We analyzed the Quantum Boltzmann equation for an ensemble of CMB photons interacting with the right-handed sterile neutrino dark matter (DM) and axion-like particles (ALPs) DM in the presence of the scalar metric perturbation. We used the birefringence angle of CMB to study those probable candidates of DM. It is shown that the CB angle contribution of sterile neutrino is much less that two other sources considered here. Next, we combined the results of the cosmic neutrinos' contribution and the contribution of the ALPs to producing the CMB birefringence and discussed the uncertainty on the parameter space of axions caused by the share of CMB-cosmic neutrino interaction in generating this effect. Finally, we plotted the EB power spectrum of the CMB and showed that this spectrum behaves differently in the presence of cosmic neutrinos and ALPs interactions in small l. Hence, future observed data for CEBl, will help us to distinguish the CB angle value due to the various sources of its production.

DOI: https://doi.org/10.1140/epjc/s10052-024-13004-0

Bini, Donato; Geralico, Andrea; Jantzen, Robert T.; Ruffini, Remo, On Fermi's Resolution of the "4/3 Problem" in the Classical Theory of the Electron, published in Foundations of Physics, Volume 54, on June 2024.

 

We discuss the solution proposed by Fermi to the so called "4/3 problem" in the classical theory of the electron, a problem which puzzled the physics community for many decades before and after his contribution. Unfortunately his early resolution of the problem in 1922–1923 published in three versions in Italian and German journals (after three preliminary articles on the topic) went largely unnoticed. Even more recent texts devoted to classical electron theory still do not present his argument or acknowledge the actual content of those articles. The calculations initiated by Fermi at the time are completed here by formulating and discussing the conservation of the total 4-momentum of the accelerated electron as seen from the instantaneous rest frame in which it is momentarily at rest.

DOI: https://doi.org/10.1007/s10701-024-00770-w

Ruffini, Remo; Sigismondi, Costantino, Fitting the Crab Supernova with a Gamma-Ray Burst, published in Universe, Volume 10, Issue 7 on June 2024.

 

Here, we reconsider the historical data, assuming a gamma-ray burst (GRB) as its source. A Supernova correlated with the GRB explains well the fading time observed by the ancient Chinese astronomers in the daytime and the nighttime, while the GRB power law explains the present X-rays and GeV emission of the Crab. On the grounds of a recent understanding of the first episode of binary-driven hypernova GRB (BDHN GRB) in terms of the collapse of a ten solar masses core, we propose the possible identification of the real Supernova event at an earlier time than Chinese chronicles. This work allows a new understanding of the significance of historical astronomical observations, including a fireball due to gamma-ray air shower observation and a plague of acute radiation syndrome, documented with several thousands of victims in the Eurasian area (Egypt, Iraq, and Syria).

DOI: https://doi.org/10.3390/universe10070275

Zhang, Shu-Rui; Prakapenia, Mikalai, The transformation of the rotational energy of a Kerr black hole, published in Classical and Quantum Gravity, Volume 41, Issue 13 on July 2024.

 

This paper analyzes the feedback of the rotational energy extraction from a Kerr black hole (BH) by the 'ballistic method', i.e. the test particle decay in the BH ergosphere pioneered by Roger Penrose. The focus is on the negative energy counterrotating particles (which can be massive or massless) going in towards the horizon, and the feedback on the BH irreducible mass is assessed. Generally, the change in irreducible mass is a function of the conserved quantities of the particle. For an extreme Kerr BH and in the limit , all the reduced transformable energy goes into the irreducible mass (i.e. ), resulting in high irreversibility. The amount of extracted energy from the BH using test particles is much lower than the change of transformable energy. For non-extreme Kerr BHs, the effective potential of particle motion on the equatorial plane in Kerr spacetime is analyzed, and it is demonstrated that the Penrose process can only be undergone by BHs with a dimensionless spin if the decay point coincides with the turning point. Based on that, the lower limit of the change in irreducible mass is provided as a function of the dimensionless spin of the BH. The significance of the increase in the irreducible mass of the BH during the energy extraction process is generally and concisely illustrated by introducing the concept of transformable energy of the BH. The feedback from the Penrose process on the irreducible mass demonstrates the irreversibility of energy extraction and highlights that the total amount of energy that can be extracted from a BH is less than previously anticipated.

DOI: https://doi.org/10.1088/1361-6382/ad51c2

Gao, Hao-Xuan; Geng, Jin-Jun; Sun, Tian-Rui; Li, Liang; Huang, Yong-Feng; Wu, Xue-Feng, Probing Thermal Electrons in Gamma-Ray Burst Afterglows, published in The Astrophysical Journal, Volume 971, Issue 1 on August 2024.

 

Particle-in-cell simulations have unveiled that shock-accelerated electrons do not follow a pure power-law distribution, but have an additional low-energy "thermal" part, which owns a considerable portion of the total energy of the electrons. Investigating the effects of these thermal electrons on gamma-ray burst (GRB) afterglows may provide valuable insights into the particle acceleration mechanisms. We solve the continuity equation of electrons in energy space, from which multiwavelength afterglows are derived by incorporating processes including synchrotron radiation, synchrotron self-absorption, synchrotron self-Compton scattering, and γ–γ annihilation. First, there is an underlying positive correlation between the temporal and spectral indices due to the cooling of electrons. Moreover, thermal electrons result in simultaneous nonmonotonic variations of both the spectral and temporal indices at multiple wavelengths, which could be individually recorded by the 2.5 m Wide Field Survey Telescope and Vera Rubin Observatory Legacy Survey of Space and Time (LSST). The thermal electrons could also be diagnosed using afterglow spectra from synergistic observations in the optical (with LSST) and X-ray (with the Microchannel X-ray Telescope on board the Space Variable Objects Monitor) bands. Finally, we use Monte Carlo simulations to obtain the distribution of the peak flux ratio (RX) between the soft and hard X-rays, and of the time delay (Δt) between the peak times of the soft X-ray and optical light curves. The thermal electrons significantly raise the upper limits of both RX and Δt. Thus, the distribution of GRB afterglows with thermal electrons is more scattered in the RX‑Δt plane.

DOI: https://doi.org/10.3847/1538-4357/ad5443

Ajmal, S.; Gaglione, J. T.; Gurrola, A.; Panella, O.; Presilla, M.; Romeo, F.; Sun, H.; Xue, S. -S., Searching for exclusive leptoquarks with the Nambu-Jona-Lasinio composite model at the LHC and HL-LHC, published in Journal of High Energy Physics, Volume 2024, Issue 8 on August 2024.

 

We present a detailed study concerning a new physics scenario involving four fermion operators of the Nambu-Jona-Lasinio type characterized by a strong-coupling ultraviolet fixed point where composite particles are formed as bound states of elementary fermions at the scale Λ=OTeV. After implementing the model in the Universal FeynRules Output format, we focus on the phenomenology of the scalar leptoquarks at the LHC and the High-Luminosity option. Leptoquark particles have undergone extensive scrutiny in the literature and experimental searches, primarily relying on pair production and, more recently, incorporating single, Drell-Yan t-channel, and lepton-induced processes. This study marks, for the first time, the examination of these production modes at varying jet multiplicities. Novel mechanisms emerge, enhancing the total production cross section. A global strategy is devised to capture all final state particles produced in association with leptoquarks or originating from their decay, which we termed "exclusive", in an analogy to the nomenclature used in nuclear reactions. The assessment of the significance in current and future LHC runs, focusing on the case of a leptoquark coupling to a muon–c quark pair, reveals greater sensitivity compared to ongoing searches. Given this heightened discovery potential, we advocate the incorporation of exclusive leptoquark searches in future investigations at the LHC.

DOI: https://doi.org/10.48550/arXiv.2311.18472

Della Valle, Massimo; Shafter, Allen W.; Starrfield, Sumner, Jet-induced Enhancement of the Nova Rate in M87, published in Research Notes of the AAS, Volume 8, Issue 8, on August 2024.

 

We argue that the Bondi accretion mechanism has the potential to enhance classical nova production near the M87 jet. According to our estimates, the jet's influence can increase the nova rate in its vicinity by up to a factor of two over the background rate by triggering explosions on single white dwarfs. This result may offer a straightforward explanation for the recently observed excess of novae near the M87 jet.

DOI: https://iopscience.iop.org/article/10.3847/2515-5172/ad6a55

Mestre, Martín Federico; Argüelles, Carlos Raul; Carpintero, Daniel Diego; Crespi, Valentina; Krut, Andreas, Modeling the track of the GD-1 stellar stream inside a host with a fermionic dark matter core-halo distribution, published in Astronomy & Astrophysics, Volume 68 on September 2024.

 

Context. Traditional studies of stellar streams typically involve phenomenological ΛCDM halos or ad hoc dark matter (DM) profiles with different degrees of triaxiality, which preclude us from gaining insights into the nature and mass of the DM particles. Recently, the maximum entropy principle of halo formation has been applied to provide a DM halo model that incorporates the fermionic (quantum) nature of the particles while leading to DM profiles that depend on the fermion mass. These profiles develop a more general "dense core – diluted halo" morphology that can explain the Galactic rotation curve, while the degenerate fermion core can mimic the central massive black hole (BH). Aims. We model the GD-1 stellar stream using a spherical core-halo DM distribution for the host that simultaneously explains the dynamics of the S-cluster stars through its degenerate fermion core without a central BH. Methods. We used two optimization algorithms in order to fit both the initial conditions of the stream orbit and the fermionic model. We modeled the baryonic potential with a bulge and two disks (thin and thick) with fixed parameters according to the recent literature. The stream observables were 5D phase-space data from the Gaia DR2 survey. Results. We were able to find good fits for both the GD-1 stream and the S-stars for a family of fermionic core-halo profiles parameterized by the fermion mass. The particle masses are constrained in the range 56 keV c^‑2, with a corresponding DM core of ∼10³ Schwarzschild radii, to 360 keV c^‑2, which corresponds to the most compact core of 5 Schwarzschild radii prior to the gravitational collapse into a BH of about 4 × 10⁶ M_⊙. Conclusions. This work provides evidence that the fermionic profile is a reliable model for the massive central object and for the DM of the Galaxy. Remarkably, this model predicts a total Milky Way mass of 2.3 × 10¹¹ M_⊙, which agrees with recent mass estimates obtained from Gaia DR3 rotation curves (Gaia RC). In summary, with one single fermionic model for the DM distribution of the Milky Way, we obtain a good fit on three totally different distance scales of the Galaxy: ∼10^‑6 kpc (central, S-stars), ∼14 kpc (middle, GD-1), and ∼30 kpc (boundary, Gaia RC mass estimate).

DOI: https://doi.org/10.1051/0004-6361/202348626

Li, Liang; Wang, Yu, GRB 190114C: Fireball Energy Budget and Radiative Efficiency Revisited, published in The Astrophysical Journal, Volume 972, Issue 2 on September 2024.

 

The jet composition of gamma-ray bursts (GRBs), as well as how efficiently the jet converts its energy to radiation, are long-standing problems in GRB physics. Here, we reported a comprehensive temporal and spectral analysis of the TeV-emitting bright GRB 190114C. Its high fluence (∼4.4 × 10^‑4 erg cm^‑2) allows us to conduct the time-resolved spectral analysis in great detail and study their variations down to a very short timescale (∼0.1 s) while preserving a high significance. Its prompt emission consists of three well-separated pulses. The first two main pulses (P₁ and P₂) exhibit independently strong thermal components, starting from the third pulse (P₃) and extending to the entire afterglow, the spectra are all nonthermal, and the synchrotron plus Compton upscattering model well interprets the observation. By combining the thermal (P₁ and P₂) and the nonthermal (P₃) observations based on two different scenarios (global and pulse properties) and following the method described in Zhang et al., we measure the fireball parameters and GRB radiative efficiency with little uncertainties for this GRB. A relevantly high GRB radiative efficiency is obtained based on both the global and pulse properties, suggesting that if GRBs are powered by fireballs, the efficiency can sometimes be high. More interestingly, though the observed parameters are individually different (e.g., the amount of mass loading M), the radiative efficiency obtained from P₁ (ηγ = 36.0% ± 6.5%) and P2 (ηγ = 41.1% ± 1.9%) is roughly the same, which implies that the central engine of the same GRB has some common properties.

DOI: https://doi.org/10.3847/1538-4357/ad2511

Moradi, R.; Rastegarnia, F.; Wang, Y.; Mirtorabi, M. T., FNet II: spectral classification of quasars, galaxies, stars, and broad absorption line (BAL) quasars, published in Monthly Notices of the Royal Astronomical Society, Volume 533, Issue 2 on September 2024.

 

In this work, we enhance the FNet, a 1D convolutional neural network (CNN) with a residual neural network (ResNet) architecture, to perform spectral classification of quasars, galaxies, stars, and broad absorption line (BAL)-quasars in the SDSS-IV catalogue from DR17 of eBOSS. Leveraging its convolutional layers and the ResNet structure with different kernel sizes, FNet autonomously identifies various patterns within the entire sample of spectra. Since FNet does not require the intermediate step of identifying specific lines, a simple modification enabled our current network to classify all SDSS spectra. This modification involves changing the final output layer from a single value (redshift) to multiple values (probabilities of all classes), and accordingly adjusting the loss function from mean squared error to cross-entropy. FNet achieves a completeness of 99.00 per cent ± 0.20 for galaxies, 98.50 per cent ± 0.30 for quasars, 99.00 per cent ± 0.18 for BAL-quasars, and 98.80 per cent ± 0.20 for stars. These results are comparable to those obtained using QuasarNET, a standard CNN employed in the SDSS routine, comprises convolutional layers without the ResNet structure with equal kernel sizes, and is utilized for redshift measurement and classification by identifying seven emission lines. QuasarNET, in order to overcome the problem of finding a C IV emission line with broad absorption which is slightly more challenging than that of detecting emission lines requires to add BAL C IV line to the list of lines that the network learns to identify. However, this procedure is not necessary in FNet as it learns the features through a self-learning procedure.

DOI: https://doi.org/10.1093/mnras/stae1878