Article
Physics, Multidisciplinary
Ahmad Sheykhi, Maral Sahebi Hamedan
Summary: The thermodynamics-gravity conjecture suggests a strong connection between the gravitational field equations and the first law of thermodynamics, meaning any changes in entropy expression directly impact the field equations. By considering the modified Barrow entropy associated with the apparent horizon, the Friedmann equations are altered as well. This paper explores the implications of this modification on the holographic dark energy (HDE) model, highlighting changes in energy density and the Friedmann equations. The study also investigates the cosmological consequences of using the Hubble horizon and future event horizon as infrared cutoffs, including interactions between dark matter (DM) and dark energy (DE), and the impact of the Barrow exponent on the cosmological behavior of HDE, such as crossing the phantom line and shifting the universe phase transition time.
Article
Multidisciplinary Sciences
Giuseppe Gaetano Luciano, Yang Liu
Summary: This paper investigates the correspondence between the tachyon dark energy model and Barrow holographic dark energy. The dynamics of the tachyon scalar field T in a curved Friedmann-Robertson-Walker universe are reconstructed, both with and without interactions between dark energy and matter. The study shows that the tachyon field exhibits non-trivial dynamics, with different behaviors in flat and non-flat universes.
Article
Astronomy & Astrophysics
T. Harko, K. Asadi, H. Moshafi, H. Sheikhahmadi
Summary: This study investigates the effects of interaction, decay, and particle generation in a many-component Universe using an approach based on open system thermodynamics. By introducing particle number balance equations and creation pressures, the cosmological evolution equations are thermodynamically consistent. Constrained by multiple observational data sets, this model provides a solution to the Hubble tension problem.
PHYSICS OF THE DARK UNIVERSE
(2022)
Article
Astronomy & Astrophysics
Rabia Saleem, Shahnila
Summary: In this work, the phenomenon of cosmic evolution is explored using curved FLRW space-time bounded by apparent horizon with a specific holographic cut-off in the framework of Rastall gravity. The results show that the interacting model is closer to the ΛCDM model compared to the non-interacting case, supporting the idea that the holographic proposal is sufficient to describe the cosmic evolution at an accelerating rate.
PHYSICS OF THE DARK UNIVERSE
(2021)
Article
Physics, Particles & Fields
Yang Liu
Summary: In this article, we investigate three inflation models - Higgs inflation model, Higgs-dilaton model, and Palatini Higgs inflation model - to simultaneously satisfy the further refining dS swampland conjecture and scalar weak gravity conjecture (SWGC). We determine the conditions for these three models to satisfy scalar weak gravity conjecture (SWGC) and strong scalar weak gravity conjecture (SSWGC).
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
G. G. Luciano, J. Gine
Summary: In this paper, we construct a generalized interacting model of Barrow Holographic Dark Energy (BHDE) with the infrared cutoff given by the Hubble horizon. We analyze the cosmological evolution of a flat Friedmann-Lemaitre-Robertson-Walker Universe filled with pressureless dark matter, BHDE, and radiation fluid. The interaction between the dark sectors is assumed to be of non-gravitational origin and satisfying the second law of thermodynamics and Le Chatelier-Braun principle. We study various model parameters and investigate the growth rate of matter fluctuations in the linear regime, showing that our model is consistent with current observations and provides a suitable candidate to describe dark energy. We also explore the thermodynamics of our framework, with a focus on the validity of the generalized second law.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Physics, Multidisciplinary
Rong-Gen Cai, Shao-Jiang Wang
Summary: We have proposed a refined version of the trans-Planckian censorship conjecture (TCC) based on the strong scalar weak gravity conjecture and some entropy bounds. This refined TCC does not require fine-tuning on inflation model-building and passes tests from stringy examples supporting the original TCC. Additionally, it could be compatible with hilltop eternal inflation.
SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY
(2021)
Article
Astronomy & Astrophysics
Hassan Amirhashchi, Anil Kumar Yadav, Nafis Ahmad, Vikrant Yadav
Summary: This study presents observational constraints on the coupling between dark energy and dark matter in an anisotropic Bianchi type I universe. The findings suggest that there is no interaction between the dark components, indicating support for a model without interaction.
PHYSICS OF THE DARK UNIVERSE
(2022)
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
R. Raushan, A. Singh
Summary: We investigate the flat-FRW model in the dynamical Chern-Simons gravity with interacting dark energy. The model yields late-time accelerating universe with decelerating past having matter, radiation and stiff matter dominated phases. The modification term of the Chern-Simons gravity gives a nontrivial impact on the cosmological evolution of universe in the model. The model possess an attractor corresponding to the accelerated expansion at late-times, compatible with the observations. The evolution of cosmological parameters like deceleration parameter, effective equation of state parameter, state-finder diagnostic analysis and classical stability of the model have been discussed in detail. We show that the model possesses decelerating past originating with stiff-matter like evolution, further evolving into radiation and/or matter dominated phases with late-time accelerating universe evolution as ultimate fate, on the basis of model parameter values. The model is classically stable in nature.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Physics, Multidisciplinary
E. H. Baffou, M. J. S. Houndjo, I. G. Salako, F. K. Ahloui, A. D. Kanfon
Summary: In this paper, the Ricci dark energy model (RDE) with bulk viscosity is investigated in the context of f(R, T) gravity to explain the universe's accelerated expansion. By assuming that the cosmological evolution is governed by the RDE model with bulk viscosity, the modified Friedmann equations in flat geometry are derived from f(R, T) gravity. For a specific form of f(R, T) = R + 2AT model and a bulk viscosity coefficient of the form ξ = ξ0+ξ1H, various cosmological parameters such as the Hubble parameter, deceleration parameter, effective equation of state, statefinder, and Om diagnostic parameters are calculated. The results suggest that this model can be considered as an alternative candidate to describe dark energy.
CHINESE JOURNAL OF PHYSICS
(2023)
Article
Physics, Particles & Fields
Armin van de Venn, David Vasak, Johannes Kirsch, Juergen Struckmeier
Summary: The paper investigates the implications of metric compatible covariant canonical gauge theory of gravity on cosmological scales. The resulting equations of motion in a Friedmann-Lemaitre-Robertson-Walker Universe are derived for a totally anti-symmetric torsion tensor. The modifications of the Friedmann equations, equivalent to spatial curvature, are shown in the limit of a vanishing quadratic Riemann-Cartan term and are further investigated in the early and late times of the Universe's history.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Multidisciplinary Sciences
Shivangi Rathore, S. Surendra Singh
Summary: This paper investigates an interacting dark energy model in LRS Bianchi type I cosmological model with a scalar field in the form of an exponential potential. By calculating the critical points and eigenvalues of the Jacobian matrix, we find that the Universe is accelerating and obtain the critical points and behavior of dark energy for different coupling parameters.
SCIENTIFIC REPORTS
(2023)
Article
Astronomy & Astrophysics
Eleonora Di Valentino, Olga Mena
Summary: This paper analyzes the constraints and potential hints obtained for models involving an interaction between the dark matter and dark energy sectors using simulated Planck data. The simulations suggest a potential fake detection for a non-zero interaction among the dark matter and dark energy fluids when dealing with current cosmic microwave background (CMB) Planck measurements alone. Future CMB observations, particularly cosmic variance limited polarization experiments, may provide more reliable cosmological constraints and break existing parameter degeneracies.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Jafar Sadeghi, Mohammad Reza Alipour, Saeed Noori Gashti
Summary: In this article, the compatibility of four inflation models with the swampland program's conjectures is studied. It is found that these models are not compatible with all conjectures in all regions, except for a specific area. The super Yang-Mills inflation model and Orientifold inflation model show higher compatibility with all the conjectures.
Article
Astronomy & Astrophysics
Yungui Gong, Jun Luo, Bin Wang
Summary: The concepts and development milestones of the two Chinese space-based gravitational wave observatories, TianQin and Taiji, are introduced. Possible collaborations among them are discussed, considering their similar goals and operation window with LISA. Both facilities, planned to be launched in the 2030s, are complementary to LISA and aim to improve GW source localization and characterization.
Editorial Material
Astronomy & Astrophysics
Yungui Gong
Article
Astronomy & Astrophysics
Jiong Lin, Shengqing Gao, Yungui Gong, Yizhou Lu, Zhongkai Wang, Fengge Zhang
Summary: We address the potential-restriction issue in K/G inflation by introducing nonminimal coupling, where the Higgs field drives inflation in accordance with cosmic microwave background (CMB) observations and enhances curvature perturbations at small scales, thereby explaining the formation of primordial black holes (PBHs) and scalar induced gravitational waves (SIGWs). We further analyze the effect of the noncanonical kinetic coupling function and its observational constraint. Additionally, we provide a gauge invariant expression for the integral kernel of SIGWs, which relates to terms propagating at the speed of light. Lastly, we examine the non-Gaussian effect on the abundance of PBHs and SIGWs, finding that while non-Gaussianity facilitates PBH formation, it has negligible impact on the energy density of SIGWs.
Article
Physics, Particles & Fields
Xuchen Lu, Yungui Gong
Summary: Hubble tension is a significant problem in cosmology, and by recalibrating the luminosity distances using gravitational waves, the issues of zero-point calibration and model dependence in SNe Ia measurements can be resolved.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
Chao Zhang, Yungui Gong
Summary: In this study, we investigate extreme mass ratio inspirals and numerically demonstrate that space-based gravitational wave detectors, such as the Laser Interferometer Space Antenna, can detect small charge to mass ratios q of charged particles.
Article
Astronomy & Astrophysics
Ning Dai, Yungui Gong, Tong Jiang, Dicong Liang
Summary: This study investigates the impact of a dark matter minispike around an intermediate massive black hole on the orbital evolution of a binary system. The existence of the minispike leads to deviations from the Keplerian orbit and can potentially be detected in future space-based gravitational wave detectors.
Article
Astronomy & Astrophysics
Hong Guo, Yunqi Liu, Chao Zhang, Yungui Gong, Wei-Liang Qian, Rui-Hong Yue
Summary: We study extreme mass ratio inspirals in modified gravity, modeling a system where a small compact object with scalar charge spirals into a supermassive Kerr black hole. Besides tensorial gravitational waves, radiation is induced by the scalar field. By investigating the dependence of observables on specific spacetime configurations, we find that the presence of additional scalar emission leads to a more significant rate of overall energy loss and has a greater impact on the gravitational radiation produced by a central black hole with higher spin, indicating the possibility of detecting the scalar charge.
Article
Astronomy & Astrophysics
Chunyu Zhang, Yungui Gong, Chao Zhang
Summary: The sky localization of the gravitational wave source can be significantly improved with a network of space-based GW detectors. The improvement is mainly determined by the angle between the detector planes and the time delay, while the effects of arm length and higher harmonics are negligible for source localization.
Article
Astronomy & Astrophysics
Chao Zhang, Yungui Gong, Dicong Liang, Chunyu Zhang
Summary: This study introduces a specific data analysis pipeline for detecting the polarization modes of gravitational waves. Through an example analysis using simulated data, it demonstrates that the method is capable of detecting pure and mixed polarizations without knowing the exact polarization modes.
Article
Astronomy & Astrophysics
Chao Zhang, Yungui Gong, Bin Wang, Chunyu Zhang
Summary: By employing the Fisher information matrix analysis, parameter errors of TianQin and Laser Interferometer Space Antenna (LISA) for monochromatic gravitational waves are estimated. Different patterns in angular resolutions and estimation errors of sources' parameters between LISA and TianQin are disclosed at different frequency regimes. In the high-frequency regime, numerical calculations show that the parameter estimation errors measured by TianQin are smaller than those by LISA.
Article
Astronomy & Astrophysics
Chao Zhang, Yungui Gong, Hang Liu, Bin Wang, Chunyu Zhang
Summary: By utilizing the Fisher information matrix approximation, the angular resolutions of the LISA and TianQin space-based gravitational wave detectors were computed, with considerations given to the impact of various detector configuration properties on the accuracy of source localization for monochromatic sources. The study found that LISA has better accuracy at lower frequencies, while TianQin performs better at higher frequencies in sky localization. The potential advantages of the LISA-TianQin network in sky localization were also explored.
Article
Astronomy & Astrophysics
Zhu Yi, Qing Gao, Yungui Gong, Zong-hong Zhu
Summary: With the proposed enhancement mechanism using a noncanonical kinetic term with a peak, the study demonstrates the amplification of primordial curvature perturbations and the generation of primordial black hole dark matter and gravitational waves. Using examples from the Higgs model and T-model, the research illustrates the production of black hole dark matter of different masses and gravitational waves with varying peak frequencies.
Article
Astronomy & Astrophysics
Zhu Yi, Yungui Gong, Bin Wang, Zong-hong Zhu
Summary: Researchers have proposed a novel mechanism to demonstrate the ability of the Higgs model in particle physics to drive inflation in the universe. The study also suggests that secondary gravitational waves induced by Higgs fluctuations could provide clues for detecting primordial black holes.
Article
Astronomy & Astrophysics
Jiong Lin, Yungui Gong, Yizhou Lu, Fengge Zhang
Summary: In the framework of spatially covariant gravity, the extension of a gravitational theory with two physical degrees of freedom (DoF) is studied by putting the lapse function N and the spatial metric h(ij) on an equal footing. Two sufficient and necessary conditions for ensuring these two DoF are identified through Hamiltonian analysis. Different cases with coupling functions dependent on N or spatial derivatives of N are explored, revealing the possibility of wave solutions and the recovery of general relativity (GR) in certain scenarios. Additionally, a disformal transformation is shown to lead to a class of quadratic actions with two DoF that can be derived from GR.
Article
Astronomy & Astrophysics
Arshad Ali, Yungui Gong, Yizhou Lu
Summary: The paragraph discusses the results of studying scalar-induced tensor perturbations during matter domination in various gauges, revealing that the kernel functions in synchronous and comoving gauges are the same and identifying oscillating terms in the perturbations as the secondary gravitational waves induced by scalars. Additionally, it is found that the energy density of these waves is gauge independent and behaves like radiation in the matter-dominated era.
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.
