Article
Astronomy & Astrophysics
Srijita Sinha, Manisha Banerjee, Sudipta Das
Summary: In this paper, an interacting model of dark energy was examined, where the dark sectors are allowed to interact among themselves through an assumed relation. By solving the perturbation equations numerically, the imprints on the growth of matter and dark energy fluctuations were studied. It was observed that higher rates of interaction strength for the coupling term resulted in visible imprints on the dark energy density fluctuations at the early epochs of evolution.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Multidisciplinary Sciences
Cosmin Andrei, Anna Ijjas, Paul J. Steinhardt
Summary: In this paper, we investigate how short the remaining period of expansion can be given current observational constraints on dark energy, and discuss how this scenario fits naturally with cyclic cosmologies and recent conjectures about quantum gravity.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
Article
Astronomy & Astrophysics
Mohammad Ali Gorji, Hayato Motohashi, Shinji Mukohyama
Summary: In the context of scalar-tensor theories, stealth de Sitter solutions face issues of infinite strong coupling or gradient instability, which can be resolved by introducing a controlled detuning mechanism known as scordatura. This mechanism not only resolves the mentioned issues, but also ensures a well-defined quasi-static limit.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Francesco Pace, Carlo Schimd
Summary: This study extends the analysis of Pace et al. by considering the virialization process in clustering dark-energy models. The research finds that five out of seven clustering dark-energy models can be statistically distinguished from the Lambda CDM model and the corresponding smooth dark-energy models in large-scale surveys.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Physics, Particles & Fields
Christian Gross, Giacomo Landini, Alessandro Strumia, Daniele Teresi
Summary: First order phase transitions can create relic pockets of false vacua and their particles, which can manifest as macroscopic Dark Matter. This can be predicted by a model involving a gauge theory with dark quarks as relics. During the transition, these dark quarks remain in the false vacuum and form Fermi balls, which can collapse into stable dark dwarfs or primordial black holes.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Astronomy & Astrophysics
Sergei D. Odintsov, Tanmoy Paul, Indrani Banerjee, Ratbay Myrzakulov, Soumitra SenGupta
Summary: This study proposes a cosmological scenario in which the universe goes through a non-singular bounce, followed by deceleration and acceleration stages. By using Chern-Simons corrected F(R) gravity theory and confronting the model with observational data, the results are found to be consistent with the latest Planck 2018 constraints.
PHYSICS OF THE DARK UNIVERSE
(2021)
Article
Astronomy & Astrophysics
Junpei Harada
Summary: Three theoretical criteria for gravitational theories beyond general relativity are considered, and a new gravitational field equation is proposed to fulfill these criteria. A spherically symmetric exact solution is derived from this equation, which incorporates three terms and provides a novel explanation for the accelerating expansion of the universe. This solution does not require negative pressure as dark energy or a positive cosmological constant.
Article
Mathematics
Ahmad T. Ali
Summary: In this article, we classify developable surfaces in three-dimensional Euclidean space R-3 that are foliated by general ellipses. We prove that a surface has constant Gaussian curvature (CGC) and is foliated by general ellipses if and only if it is developable, meaning that the Gaussian curvature G vanishes everywhere. We characterize all developable surfaces that are foliated by general ellipses, including conical surfaces and surfaces generated by special base curves.
Article
Astronomy & Astrophysics
Shu-Lin Cheng, Da-Shin Lee, Kin-Wang Ng
Summary: We develop a nonperturbative method to examine the quantum fluctuation effects on the single-field inflationary models in a spatially flat FRW cosmological space-time using the Hartree factorization. We derive the modified Mukhanov-Sasaki equations for the mode functions of the quantum scalar field by introducing the nonzero Delta(B) term. We find that the presence of ultra slow roll inflation triggers the growth of Delta(B) and boosts the curvature perturbations, but the cosmic friction term may inhibit this boost effect.
Article
Astronomy & Astrophysics
Joseph P. Johnson, Archana Sangwan, S. Shankaranarayanan
Summary: In this study, we investigate an interacting field theory model for the interaction between dark energy and dark matter. By comparing with cosmological data, we find that this interacting model is consistent with observations and obtain quantitative tools to distinguish between interacting and non-interacting dark energy scenarios.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Marco Raveri, Levon Pogosian, Matteo Martinelli, Kazuya Koyama, Alessandra Silvestri, Gong -Bo Zhao
Summary: In this paper, a non-parametric reconstruction method is presented to determine three time-dependent functions in the cosmological model. The data constraints on the structure of these functions and their eigenmodes are analyzed. The results show that the combination of all data can constrain 15 combined eigenmodes of the three functions and explain the tensions between datasets.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Ido Ben-Dayan, Merav Hadad, Amir Michaelis
Summary: By analyzing the statistical physics and quantizing, we find that the cosmological constant of the Multiverse is exponentially small and does not require anthropic reasoning. Additionally, quantization allows the interpretation of a single Universe as a superposition of different energy levels and eigenstates.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Chayanika Rabha, Sanjeev Kalita
Summary: In this study, deceleration-acceleration and future evolution of cosmic expansion with curved dynamical dark energy models were constructed, and it was found that cosmic doomsday seems inevitable regardless of spatial curvature. Additionally, two novel parametrizations of dark energy equation of state were used to study the deceleration parameter q(z), showing that the quintessence component becomes sub-dominant in the future irrespective of spatial curvature.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2021)
Article
Mathematical & Computational Biology
Junjie Liu, Hui Wang, Xue Li, Kai Chen, Chaoyu Li
Summary: Inefficient trajectory planning of six-degree-of-freedom industrial manipulators is addressed by proposing a trajectory planning algorithm based on an improved multiverse algorithm (IMVO) for time, energy, and impact optimization. The algorithm improves convergence speed and global search capability by improving the wormhole probability curve, adaptive parameter adjustment, and population mutation fusion. The algorithm is applied to multi-objective optimization to derive the Pareto solution set and optimize the objective function using IMVO. Experimental results show improved timeliness and optimization of time, energy consumption, and impact problems in manipulator trajectory planning.
MATHEMATICAL BIOSCIENCES AND ENGINEERING
(2023)
Article
Astronomy & Astrophysics
Shweta Saklany, Neeraj Pant, Brajesh Pandey
Summary: The main aim of this study is to investigate the influence of background dark energy on a gravitationally compact star, PSRJ0740 + 6620. The Einstein field equations are used in an anisotropic regime to model the space-time fabric and associated gravity. The spatial metric potential of Vaidya-Tikekar type is utilized to obtain the temporal metric potential using Karmarkar's connecting relation and the unknown constants are calculated using Darmois-Israel conditions. Through rigorous theoretical analysis, it is found that the model star satisfies all the necessary and sufficient conditions to form a viable stellar configuration. The key findings suggest that the background repulsive scalar field of dark energy can aid in the formation of dense and stable stellar structures at masses beyond the TOV limit.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Astronomy & Astrophysics
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.
Article
Astronomy & Astrophysics
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.
Article
Astronomy & Astrophysics
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.
Article
Astronomy & Astrophysics
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.
