Article
Astronomy & Astrophysics
Energy rates due to Fe isotopes during presupernova evolution of massive stars
Jameel-Un Nabi, Asim Ullah, Majid Iqbal
Summary: This study presents microscopic calculations of energy rates due to weak decay of selected Fe isotopes, with a focus on γ-ray heating and (anti)neutrino cooling rates. The results show significant differences in cooling rates among different models, while γ-ray heating rates are found to be correlated with temperature and density. This study is important for a realistic simulation of the presupernova evolution of massive stars.
NEW ASTRONOMY (2024)
Article
Astronomy & Astrophysics
Spiral-Elliptical automated galaxy morphology classification from telescope images
M. J. Baumstark, G. Vinci
Summary: The classification of galaxy morphologies is important for studying hierarchical structure formation theories. Traditional manual visual classification cannot cope with the large influx of data, leading to the proposal of crowdsourced visual classification and automated computational methods. This study develops two novel galaxy morphology statistics and simplifies existing image statistics, demonstrating their accuracy and effectiveness.
ASTRONOMY AND COMPUTING (2024)
Article
Astronomy & Astrophysics
Inhomogeneity of a rotating quark-gluon plasma from holography
Nelson R. F. Braga, Octavio C. Junqueira
Summary: This study investigates the influence of rotation on the transition temperature of strongly interacting matter produced in non-central heavy ion collisions. By using a holographic description of an AdS black hole, the authors extend the analysis to the more realistic case where the matter spreads over a region around the rotational axis. The results show the coexistence of confined and deconfined phases and are consistent with the concept of local temperature in rotating frames developed by Tolman and Ehrenfest.
PHYSICS LETTERS B (2024)
Article
Astronomy & Astrophysics
Constrain the time variation of the gravitational constant via the propagation of gravitational waves
Bing Sun, Jiachen An, Zhoujian Cao
Summary: This paper investigates the effect of gravitational constant variation on the propagation of gravitational waves. By employing two analytical methods, the study finds that variations in the gravitational constant result in amplitude and phase corrections for gravitational waves, and the time variation of the gravitational constant can be constrained through the propagation of gravitational waves.
PHYSICS LETTERS B (2024)
Review
Astronomy & Astrophysics
GRMHD study of accreting massive black hole binaries in astrophysical environment: A review
Federico Cattorini, Bruno Giacomazzo
Summary: This article presents recent numerical advances in the theoretical characterization of massive binary black hole (MBBH) mergers in astrophysical environments. These systems are significant sources of gravitational waves (GWs) and promising candidates for multimessenger astronomy. Coincident detection of GWs and electromagnetic (EM) signals from merging MBBHs is a leading area of study in contemporary astrophysics. The scarcity of strong predictions for EM signals before, during, and after merger poses a major challenge in observational efforts. To address this, significant theoretical work has focused on characterizing EM counterparts that accompany GW signals. Full general relativistic modeling using Einstein's field equations coupled with magnetohydrodynamics equations has been key in producing accurate EM predictions. This review explores numerical investigations into the astrophysical manifestations of MBBH mergers and their potentially observable EM signatures.
ASTROPARTICLE PHYSICS (2024)
Article
Astronomy & Astrophysics
Thermodynamics under the extended uncertainty principle background: Q - φ criticality analysis
Amritendu Haldar, Anendu Haldar
Summary: This article investigates the thermodynamics in the background of the "extended uncertainty principle", focusing on a charged black hole in higher dimensional space-time. The thermodynamic parameters are presented based on a semiclassical framework, and extended within the EUP background. The effects of EUP on phase transition and stability of the black holes are studied.
NEW ASTRONOMY (2024)
Article
Astronomy & Astrophysics
Avoiding parameter fine-tuning in mass varying neutrino models of DE?
Michael Maziashvili, Vakhtang Tsintsabadze
Summary: Coupled models of quintessence are introduced to avoid or mitigate the parameter fine-tuning problem and also should avoid the fine-tuning problem related to the initial conditions. Coupled models can explain the timescale of the coincidence between dark energy and matter energy densities, as well as the transition of dark energy dominance. Studying the mass varying neutrino model of dark energy with inverse power-law potential helps to understand its naturalness.
ASTROPARTICLE PHYSICS (2024)
Article
Astronomy & Astrophysics
Compact stars: To cross or go around? That is the question
Shahar Hod
Summary: The travel times of light signals between two antipodal points on a compact star's surface are calculated for two different trajectories. It is shown that, for highly dense stars, the longer trajectory along the surface may have a shorter travel time as measured by asymptotic observers. A critical value of the dimensionless density-area parameter is determined for constant density stars to distinguish cases where crossing through the star's center or following a semi-circular trajectory on the surface has a shorter travel time as measured by asymptotic observers.
PHYSICS LETTERS B (2024)
Article
Astronomy & Astrophysics
Quantum tunneling from Schwarzschild black hole in non-commutative gauge theory of gravity
Abdellah Touati, Zaim Slimane
Summary: This letter presents the first study of Hawking radiation as a tunneling process within the framework of non-commutative gauge theory of gravity. The non-commutative Schwarzschild black hole is reconstructed using the Seiberg-Witten map and the star product. The emission spectrum of outgoing massless particles is computed using the quantum tunneling mechanism. The results reveal pure thermal radiation in the low-frequency scenario, but a deviation from pure thermal radiation in the high-frequency scenario due to energy conservation. It is also found that noncommutativity enhances the correlations between successively emitted particles.
PHYSICS LETTERS B (2024)
Article
Astronomy & Astrophysics
A new look at the YY CrB binary system
Somayeh Soomandar, Atila Poro
Summary: This study presents a new analysis of the W UMa binary star YY CrB observed by TESS. The light curve was analyzed using the PHOEBE Python version and the MCMC method. The analysis reveals the presence of a hot spot and l3 in the light curve solutions. New eclipse times were extracted from TESS observations, and the O-C curve of primary and secondary minima showed an anti-correlated manner. The study also investigates the O-C curve of minima between 1991 and 2023, resulting in a new linear ephemeris and the calculation of the orbital period rate and mass exchange rate. The presence of a third body in the binary was determined using the light travel time function, but its existence is considered unlikely based on the O-C curve analysis and the quantity of mass. This binary system is expected to evolve into a broken-contact phase and supports the thermal relaxation oscillation model.
NEW ASTRONOMY (2024)
Article
Astronomy & Astrophysics
Asymptotic symmetries in Bondi gauge and the sub-subleading soft graviton theorem
Bart Horn
Summary: We investigate asymptotic symmetries that preserve the Bondi gauge conditions but do not preserve the asymptotic falloff conditions for the metric near the null boundary and their connection to soft graviton theorems for scattering amplitudes.
CLASSICAL AND QUANTUM GRAVITY (2023)
Article
Astronomy & Astrophysics
Reconciling absence of vDVZ discontinuity with absence of ghosts in nonlocal linearized gravity
D. Dalmazi
Summary: Modern massive gravity theories address the historical tension between the absence of mass discontinuity and the absence of ghosts by introducing a fine-tuned gravitational potential and a sophisticated screening mechanism. Linearized nonlocal theories with exponential terms offer a solution to these issues and can be further extended to non-linear completions.
CLASSICAL AND QUANTUM GRAVITY (2023)
Article
Astronomy & Astrophysics
Deformations of dispersionless Lax systems
Wojciech Krynski
Summary: This study focuses on dispersionless Lax systems and proposes a systematic method for deriving new integrable systems from existing ones. Several examples, including the dispersionless Hirota equation, the generalized heavenly equation, and equations related to Veronese webs, are provided to demonstrate the effectiveness of the proposed method.
CLASSICAL AND QUANTUM GRAVITY (2023)
Article
Astronomy & Astrophysics
Black holes and hot shells in the Euclidean path integral approach to quantum gravity
Jose P. S. Lemos, Oleg B. Zaslavskii
Summary: In this study, we investigate a black hole surrounded by a hot self-gravitating thin shell in the canonical ensemble. Using the Euclidean path integral approach, we derive the quantum statistical mechanics partition function of this matter-black hole system and obtain the thermodynamics of the system. We find that the total entropy is solely determined by the gravitational radius of the system and is not affected by the black hole inside the shell. We also determine the free energy, thermodynamic energy, and the temperature stratification along the system. Additionally, we establish the first law of thermodynamics and analyze the thermodynamic stability of the system through the calculation of the heat capacity.
CLASSICAL AND QUANTUM GRAVITY (2023)
Article
Astronomy & Astrophysics
In horizon penetrating coordinates: Kerr black hole metric perturbation, construction and completion
Fawzi Aly, Dejan Stojkovic
Summary: In this study, we investigate the behavior of perturbation waves in the Teukolsky equation using horizon-penetrating coordinates. We find that the radial functions satisfy physical boundary conditions and the Hertz-Weyl scalar equations preserve their characteristics in these coordinates. Using the angular equation, we construct the metric perturbation for a perturber orbiting a black hole in Kerr spacetime in a horizon-penetrating setting and provide an explicit formula for the metric perturbation.
CLASSICAL AND QUANTUM GRAVITY (2023)
Article
Astronomy & Astrophysics
Galaxy rotation curve in hyperconical universes: a natural relativistic MOND
Robert Monjo
Summary: This paper proposes a modified gravity model that can explain the excess rotation of galaxies and mass-discrepancy acceleration, and it adjusts well to experimental data.
CLASSICAL AND QUANTUM GRAVITY (2023)
Article
Astronomy & Astrophysics
Geometric post-Newtonian description of massive spin-half particles in curved spacetime
Ashkan Alibabaei, Philip K. Schwartz, Domenico Giulini
Summary: This study investigates the Dirac equation coupled to an external electromagnetic field in a four-dimensional curved spacetime with a given timelike worldline representing a classical clock. By using generalised Fermi normal coordinates and performing expansions, a weak-gravity post-Newtonian expression for the Pauli Hamiltonian of a spin-half particle in an external electromagnetic field is derived.
CLASSICAL AND QUANTUM GRAVITY (2023)
Article
Astronomy & Astrophysics
Quantum gravity phenomenology from the perspective of quantum general relativity and quadratic gravity
Gabriel Menezes
Summary: Multi-messenger astronomy provides us with the possibility of discovering phenomenological signatures of quantum-gravity effects. Feasible explorations within the effective field theory (EFT) treatment of general relativity have been discussed. Current techniques borrowed from modern amplitude methods were used to calculate leading quantum corrections to the classical radiated momentum and spectral waveforms. The results highlight the potential applications of the EFT approach in gravitational-wave physics. Furthermore, possible phenomenological surveys from the perspective of a UV completion for quantum gravity employing quadratic gravity were examined, revealing a deviation from the standard general-relativity prediction.
CLASSICAL AND QUANTUM GRAVITY (2023)
Article
Astronomy & Astrophysics
The effects of gravitational waves on a hydrogen atom
N. Wanwieng, N. Chattrapiban, A. Watcharangkool
Summary: We investigate the influence of gravitational waves on a freely falling hydrogen atom by analyzing the dynamics of the bound electron described by the Dirac equation in the curved spacetime of a gravitational wave. We derive the corresponding Dirac Hamiltonian in the local inertial frame of the atom and employ the Foldy-Wouthuysen transformation to obtain a non-relativistic description. The analysis of interaction terms and comparison with flat spacetime counterparts provide valuable insights into the effects of gravitational waves on the hydrogen atom.
CLASSICAL AND QUANTUM GRAVITY (2023)
Article
Astronomy & Astrophysics
Local momentum space: scalar field and gravity
Sukanta Panda, Abbas Tinwala, Archit Vidyarthi
Summary: This study employs the local momentum space technique to derive the first-order expansion of Feynman propagators for scalar field and graviton in the presence of background curvature. The obtained propagators are validated by comparing them with previous literature and traced heat kernel coefficients. These propagators are then utilized to calculate the one-loop divergences in the Vilkovisky-Dewitt's effective action for a scalar field non-minimally coupled with gravity in an arbitrary spacetime metric. The comparison between the VD effective action and the standard effective action reveals an important result regarding the limit kappa = 0 and the presence of gravity.
CLASSICAL AND QUANTUM GRAVITY (2023)
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