Article
Astronomy & Astrophysics
Alexandre M. R. Almeida, Julio C. Fabris, Mahamadou Hamani Daouda, Richard Kerner, Hermano Velten, Willian S. Hipolito-Ricaldi
Summary: This paper introduces a unimodular version of the Brans-Dicke theory with a constrained Lagrangian formulation, resulting in traceless field equations. The vacuum solutions in the cosmological background reproduce the solutions of the usual Brans-Dicke theory with an additional cosmological constant term. A perturbative analysis of the scalar modes reveals both stable and unstable configurations, contrasting with the Brans-Dicke case where only stable configurations occur. However, the tensorial modes remain unchanged in this theory compared to the traditional Brans-Dicke theory.
Article
Astronomy & Astrophysics
Kunio Kaneta, Kin-ya Oda, Motohiko Yoshimura
Summary: This paper presents a cosmological analysis of extended Jordan-Brans-Dicke (eJBD) gravity in the Einstein metric frame. It is the first systematic investigation of how to introduce the lagrangian of standard particle physics in the eJBD framework consistently. The study is significant for understanding the time evolution of eJBD gravity and its compatibility with observational and laboratory bounds.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Physics, Multidisciplinary
S. K. Maurya, Ksh Newton Singh, Saibal Ray
Summary: This study applies the Brans-Dicke theory of gravitation as an alternative to general relativity for modeling anisotropic compact stellar objects. By considering specific conditions for the space-time, the field equations become solvable and the numerical solution for the Brans-Dicke scalar field phi fits well with a known function. The solutions set appears viable based on observational data.
CHINESE JOURNAL OF PHYSICS
(2021)
Article
Astronomy & Astrophysics
Bardia H. Fahim, Valerio Faraoni, Andrea Giusti
Summary: A new one-parameter family of solutions to the vacuum Brans-Dicke field equations is reported in this study, which are spherically symmetric, inhomogeneous, and time-dependent. These solutions are conformal to the Roberts scalar field geometries of Einstein gravity and contain a naked central singularity. By using this new solution as a seed, another two-parameter family of solutions can be generated through a known symmetry of vacuum Brans-Dicke gravity.
Article
Physics, Particles & Fields
M. Dehghani
Summary: It has been shown that the exact solutions of the 4D Brans-Dicke-Maxwell (BDM) theory are Reissner-Nordstrom (RN) black holes coupled to a constant scalar field or zero. However, when the scalar potential is not constant or zero, novel black hole solutions affected by a nontrivial scalar hair are obtained. The inclusion of the scalar hair makes the asymptotic behavior of the solutions non-flat and non-AdS, and the theory allows for the occurrence of multi-horizon black holes due to the conformal invariance of Maxwell's electrodynamics, implying anti-evaporation quantum effect. The thermodynamic properties and stability of the BDM black holes are analyzed and found to satisfy the first law of black hole thermodynamics.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Multidisciplinary
Ashutosh Singh
Summary: This article explores the non-equilibrium thermodynamic aspects of cosmological apparent horizon in Brans-Dicke gravity, studying the time evolution of total entropy, entropy production, and entropy of matter inside the horizon. The validity of the generalized second law of thermodynamics in expanding and bouncing Brans-Dicke cosmologies is also examined.
EUROPEAN PHYSICAL JOURNAL PLUS
(2021)
Article
Physics, Particles & Fields
Hatice Ozer, Ozgur Delice
Summary: The study investigates weak field gravitational wave solutions in Brans-Dicke theory with a cosmological constant, revealing massless scalar waves and their effects on free particles and polarization properties. The analysis also includes the role of the cosmological constant in these phenomena and discusses the energy flux of these waves, leading to an extension of the Cosmic no Hair Conjecture to BD theory with a cosmological constant.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Physics, Particles & Fields
S. Habib Mazharimousavi
Summary: This article revisits the null energy condition in the context of thin-shell wormholes and introduces the general and stability conditions for satisfying this condition. Additionally, a specific metric is introduced that satisfies the null energy condition and remains stable.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
Naoki Tsukamoto
Summary: The study introduces reflection-asymmetric thin-shell wormholes with double shadows, composed of parts of Schwarzschild and Reissner-Nordstrom spacetimes with two photon spheres of different sizes. The researchers discussed the observational properties of these double shadows seen from an observer's perspective, emphasizing the presence of two photon rings with varying diameters.
Article
Physics, Multidisciplinary
S. Ghaffari, Giuseppe Gaetano Luciano, S. Capozziello
Summary: We constructed a holographic model for dark energy in the Brans-Dicke cosmology by incorporating the Barrow entropy. The Hubble horizon was used as the IR cutoff to explore the cosmological consequences. We found that both the non-interacting and interacting cases can explain the current accelerated expansion of the universe, unlike the standard holographic dark energy model. Stability analysis showed that the non-interacting model was unstable, while the sign-changeable interacting model was stable only for certain parameter values. The linear interacting model always predicted a stable universe. The consistency of the model with cosmological observations was discussed.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Astronomy & Astrophysics
Merce Guerrero, Gonzalo J. Olmo, Diego Rubiera-Garcia
Summary: This study examines reflection-asymmetric thin-shell wormholes within Palatini f(R) gravity and establishes conditions for stable wormholes supported by positive-energy matter sources. It also identifies parameter subsets for positioning the shell radius above the event horizon but below the photon sphere. Additionally, it demonstrates the phenomenon of two photon spheres allowing observers to see double shadows due to the effective potential on each side of the wormhole.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Grigoris Panotopoulos, Angel Rincon, Ilidio Lopes
Summary: This study focuses on the X-ray emission of low-mass black hole binaries in massive Brans-Dicke gravity. The accretion disk is computed using the Shakura-Sunyaev model, assuming the gravitational field generated by the stellar-mass black hole is analogous to the Schwarzschild space-time of Einstein's theory in massive Brans-Dicke gravity. The study investigates the effects of the mass of the scalar field on the properties of the binary.
Article
Astronomy & Astrophysics
Tong Jiang, Ning Dai, Yungui Gong, Dicong Liang, Chao Zhang
Summary: Intermediate/Extreme mass ratio inspiral (I/EMRI) system is an important tool to test the nature of gravity in strong field. By computing orbital evolutions and generating waveform templates, we constrain the parameters of Brans-Dicke theory.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Physics, Mathematical
Nisha Godani
Summary: The charged thin-shell wormholes are constructed using the cut-and-paste approach in the f(R) theory of gravity. The stability analysis is conducted in f(R) = R + alpha R-n gravity formalism with a linear equation of state. The effect of charge and mass on the throat radius is analyzed, and the stability of the thin shell is obtained.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2022)
Article
Physics, Multidisciplinary
M. Sharif, Faisal Javed
Summary: This paper compares the stability of geometrical structures of self-gravitating charged thin-shell and thin-shell wormholes with different types of matter distributions, finding that the thin-shell is more stable than the thin-shell wormhole.
Article
Physics, Multidisciplinary
Tinggui Chen, Baizhan Xia, Dejie Yu, Chuanxing Bi
Summary: This study proposes a gradient phononic crystal structure for enhanced acoustic sensing. By breaking the symmetry of the PC structure, topologically protected edge states are introduced, resulting in topological acoustic rainbow trapping. The robustness and enhancement properties are verified numerically and experimentally.
