Article
Astronomy & Astrophysics
Pritam Banerjee, Suvankar Paul, Rajibul Shaikh, Tapobrata Sarkar
Summary: Black holes and wormholes, although showing similar Newtonian behaviors at large distances, have different tidal effects on stars when close to the event horizon or throat due to their respective geometries. Quantitative analysis in Schwarzschild black hole and exponential wormhole backgrounds reveals that tidal disruption rates and peak fallback rates of tidal debris are several times higher for wormholes compared to black holes.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Valerio De Luca, Justin Khoury, Sam S. C. Wong
Summary: This paper investigates the tidal deformability of neutral black holes when nonlinearities in the theory are taken into account. It is found that the tidal Love numbers may be nonvanishing depending on the scalar interactions in the bulk theory.
Article
Astronomy & Astrophysics
Juliano C. S. Neves
Summary: The study presents complete and analytic solutions of regular black holes in a brane context, where the metrics are regular on both the four-dimensional brane and the five-dimensional bulk. The regular black holes have a de Sitter core on the brane and extend to the extra dimension as five-dimensional objects from the bulk perspective.
Article
Astronomy & Astrophysics
A. Belhaj, H. Belmahi, M. Benali, W. El Hadri, H. El Moumni, E. Torrente-Lujan
Summary: This study investigates the shadow behaviors of five dimensional black holes embedded in type IIB superstring/supergravity inspired spacetimes, analyzing geometrical properties such as shapes and sizes. It is found that physical parameters significantly distort the shapes and decrease the size of the shadows. The research also delves into geometrical observables and energy emission rate aspects.
Article
Astronomy & Astrophysics
Ming Zhang, Jie Jiang
Summary: This study investigates the nontrivial effects of NUT charges on the shadows of Kerr-Taub-NUT black holes seen by zero-angular-momentum-observers. It is found that as the observer approaches the string singularity, the shadow size can be relatively very small while the distortion is quite large. Additionally, in cases where the string singularity is only located at the south pole axis of the black hole with large NUT charge, the shadow size is maximal for a north pole observer.
Article
Astronomy & Astrophysics
Sumanta Chakraborty, Sayak Datta, Subhadip Sau
Summary: The phase information from tidal heating in the gravitational wave waveform can constrain the tidal charge inherited from extra dimensions to a value of around 10^-6, providing the most stringent constraint to date. Additionally, second order effects in tidal heating for exotic compact objects reveal oscillatory behavior with respect to spin, which has unique signatures.
Article
Astronomy & Astrophysics
Philip Lu, Volodymyr Takhistov, Graciela B. Gelmini, Kohei Hayashi, Yoshiyuki Inoue, Alexander Kusenko
Summary: Research has found that black holes formed in the early universe can exist as dark matter and may contribute to black hole merger events observed in gravitational waves. By studying the interactions of primordial black holes (PBHs) with the interstellar medium, a new limit on the abundance of PBHs has been established. Taking into account generic heating mechanisms, including emission from the accretion disk, dynamical friction, and disk outflows, a cosmology-independent limit on the abundance of PBHs in the O(1)M-circle dot-10(7)M(circle dot) mass range has been set using data from the Leo T dwarf galaxy, which is relevant for recently detected gravitational-wave signals from intermediate-mass black holes.
ASTROPHYSICAL JOURNAL LETTERS
(2021)
Article
Astronomy & Astrophysics
Giacomo Fragione, Abraham Loeb
Summary: Mergers of black hole (BH) and neutron star (NS) binaries are of interest due to the potential for electromagnetic counterparts following gravitational wave emissions. A proposed method utilizes the presence (absence) of a remnant disc and spin measurements to derive lower (upper) limits on the radius of the NS. This method is most effective when the aligned component of the BH spin is the largest, providing valuable information on the NS equation of state beyond what can be extracted from the GW signal.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Physics, Particles & Fields
Meirong Tang, Zhaoyi Xu
Summary: The successful observation of the M87 supermassive black hole using the EHT provides an opportunity to study the theory of gravity. In this study, the researchers obtained the exact solution for a rotating short-hair black hole and analyzed the effect of hairs on the black hole shadow. The results show that the rotation and scalar hairs have significant influences on the shape of the black hole shadow.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Astronomy & Astrophysics
Guo-Ping Li, Ke-Jian He
Summary: In this paper, the shadows and rings of the KS black hole in deformed HL gravity were carefully investigated using the ray-tracing method. The results show a decrease in certain parameters and an increase in effective potential with an increase in the omega parameter, with direct emissions dominating the total observed intensity.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Ivo Sengo, Pedro V. P. Cunha, Carlos A. R. Herdeiro, Eugen Radu
Summary: We investigate the gravitational lensing by spinning Proca stars and Kerr black holes with Proca hair, discussing their theoretical aspects and observational constraints from EHT data. Theoretical analysis reveals the optical appearance and exotic features of these BHs, interpreted in terms of photon orbit structure. Observationally, the current EHT constraints are compatible with BHs formed from the superradiant instability of Kerr BHs. The resolution of future observations is estimated to better constrain this model.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Francesco Paolo Rizzuto, Thorsten Naab, Antti Rantala, Peter H. Johansson, Jeremiah P. Ostriker, Nicholas C. Stone, Shihong Liao, Dimitrios Irodotou
Summary: We performed N-body simulations with post-Newtonian dynamics to study the formation and growth of black holes in low-mass star clusters. The simulations showed that a significant fraction of stars form Bahcall-Wolf cusps, preventing core collapse. Within the first 40 Myr, the systems experienced hundreds to thousands of tidal disruption events (TDEs), with most originating from stars in the Bahcall-Wolf cusp. We derived an analytical formula for the TDE rate and found that TDEs can drive the formation and growth of massive black holes.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Balendra Pratap Singh
Summary: In this work, the photon region and shadows of rotating black holes in the quintessential dark energy are studied when the observer is static in the domain of outer communication. The characteristics of the black hole shadow are determined by its mass, spin parameter, quintessential dark energy parameter, and normalization factor, with the state parameter significantly affecting the shape and size of the shadow. The geodesic equations of motion are generalized for the state parameter, allowing visualization of the black hole shadow by a static observer at any distance in the domain of outer communication. The angular diameter of the black hole shadow is estimated using the numerical values of the shadow radius and area, with specific values provided for the M87 and Sgr A* black holes.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Physics, Particles & Fields
Toshifumi Noumi, Hibiki Satake
Summary: This study investigates the higher derivative corrections to black brane thermodynamics and their implications for the weak gravity conjecture for p-form gauge fields. The results show that higher derivative corrections decrease the tension-to-charge ratios of extremal black branes, in line with the weak gravity conjecture, if four-derivative couplings follow scattering positivity bounds. It is also demonstrated that entropy corrections in the microcanonical ensemble are positive under the same assumptions.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Astronomy & Astrophysics
A. Ditta, G. Mustafa, G. Abbas, Farruh Atamurotov, Kimet Jusufi
Summary: The latest observation of the M87 supermassive black hole by the EHT provides insights into the accretion process onto black holes and the geodesic structure. The study investigates the circular orbits and accretion of particles near a nonlinear electrodynamics BH in strong and weak field approximations. The findings highlight the significance of the parameters beta and Q in understanding the circular orbits and mass accretion rates.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Physics, Multidisciplinary
J. C. S. Neves
Article
History & Philosophy Of Science
Juliano C. S. Neves
FOUNDATIONS OF SCIENCE
(2019)
Article
Astronomy & Astrophysics
R. Maluf, Juliano C. S. Neves
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2019)
Article
History & Philosophy Of Science
Juliano C. S. Neves
FOUNDATIONS OF SCIENCE
(2020)
Article
Mathematics, Interdisciplinary Applications
Juliano C. S. Neves
JOURNAL OF MATHEMATICAL SOCIOLOGY
(2020)
Article
Physics, Particles & Fields
Juliano C. S. Neves
EUROPEAN PHYSICAL JOURNAL C
(2020)
Article
Physics, Multidisciplinary
Juliano C. S. Neves, Alberto Saa
Article
Physics, Particles & Fields
R. Maluf, Juliano C. S. Neves
Summary: This article points out the effect of Lorentz symmetry breaking in the cosmological context, which leads to different rates of expansion in a given spatial direction. It focuses on the coupling constant xi(1), which generates the Lorentz violation in the gravity sector of the minimal Standard Model Extension. The coupling constant increases the rate of expansion of the universe in a given direction during a dark energy era, and a range of validity for this constant is obtained.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
R. Maluf, Juliano C. S. Neves
Summary: In this work, a bumblebee field is utilized to generate cosmological anisotropies by violating Lorentz symmetry through a nonzero vacuum expectation value. When coupled to Bianchi I geometry, the bumblebee field produces a preferred axis, contributing to cosmic anisotropies. The article concludes by attempting to place an upper limit on the bumblebee field using the quadrupole and octopole moments of the cosmic microwave background radiation.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Physics, Multidisciplinary
Juliano C. S. Neves
Summary: Kasner cosmology is a vacuum and anisotropically expanding spacetime studied in the bumblebee model, where Lorentz symmetry is broken. The anisotropic nature of Kasner cosmology can be explained by the bumblebee context, suggesting that the anisotropy in this model could stem from the breaking of Lorentz symmetry. An application in pre-inflationary cosmology is proposed.
Article
Physics, Multidisciplinary
D. A. Frizo, C. A. M. de Melo, L. G. Medeiros, Juliano C. S. Neves
Summary: In this study, a new method for the gravitational field equations based on the Bopp-Podolsky electrodynamics in curved spacetimes was utilized to obtain an approximate and spherically symmetric wormhole solution. The calculations considered linear approximations for both the spacetime geometry and the radial electric field. The solution introduced a new parameter, which was constrained by comparing it to the shadow radius of Sagittarius A* revealed by the Event Horizon Telescope Collaboration. Remarkably, the wormhole presented in this study is viable when comparing its shadow to that of Sagittarius A*.
Article
Astronomy & Astrophysics
Juliano C. S. Neves
Summary: The study presents complete and analytic solutions of regular black holes in a brane context, where the metrics are regular on both the four-dimensional brane and the five-dimensional bulk. The regular black holes have a de Sitter core on the brane and extend to the extra dimension as five-dimensional objects from the bulk perspective.
Article
Astronomy & Astrophysics
R. Maluf, Juliano C. S. Neves
Summary: This work introduces black hole solutions with a cosmological constant in bumblebee gravity, where the nonzero vacuum expectation value of the bumblebee field leads to Lorentz symmetry violation. These solutions are spherically symmetric black holes with an effective cosmological constant, supported by an anisotropic energy-momentum tensor. The study calculates the shadow angular radius for the proposed black hole solution, establishing a relationship between the bumblebee field and the shadow angular size for the first time.
Article
Astronomy & Astrophysics
R. V. Maluf, Juliano C. S. Neves