Article
Physics, Particles & Fields
Alvaro S. de Jesus, Nelson Pinto-Neto, Farinaldo S. Queiroz, Joseph Silk, Deivid R. da Silva
Summary: The Hubble constant derived from the 6-parameter fit to the CMB power spectrum contradicts the value obtained from direct measurements via type Ia supernova and Cepheids observations. We propose a mechanism involving effective operators that produce relativistic dark matter particles at early times, increasing the number of relativistic degrees of freedom. This mechanism can raise the value of the Hubble constant derived from CMB and reconcile discrepancies between local and CMB probes. By itself, it can increase H-0 up to 70 km s(-1) Mpc(-1), and with the addition of a Phantom-like cosmology, reach H-0 ? 71-73 km s(-1)Mpc(-1). We also outline the parameter space that reproduces H-0? 71-73 km s(-1) Mpc(-1) while satisfying all relevant constraints.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Materials Science, Multidisciplinary
M. Koussour, N. Myrzakulov, S. Myrzakulova, D. Sofuoglu
Summary: This study proposes a novel parametrization approach for the dimensionless Hubble parameter in the context of scalar field dark energy models. The evolution of cosmological parameters is explored using observational data from Cosmic Chronometers, Baryonic Acoustic Oscillations, and the Pantheon+ datasets. The results are compared with the standard ΛCDM model.
RESULTS IN PHYSICS
(2023)
Article
Multidisciplinary Sciences
Renjie Wang, Wen-Hong Ruan, Qing Yang, Zong-Kuan Guo, Rong-Gen Cai, Bin Hu
Summary: The Hubble parameter, a central parameter in cosmology, describes the expansion rate of the universe. Late-time observations yield higher values than early-time measurements by about 10%. The future LISA-Taiji network can accurately measure the Hubble parameter through gravitational wave observations, providing more reliable conclusions.
NATIONAL SCIENCE REVIEW
(2022)
Article
Astronomy & Astrophysics
Liang-Gui Zhu, Xian Chen
Summary: Dark sirens, i.e., gravitational-wave sources without electromagnetic counterparts, can be used as probes to study the expansion of the universe. However, the accuracy of measuring cosmological parameters using dark sirens can be compromised by incorrect spatial localizations caused by astrophysical environments. In this study, we investigate the precision of measuring the Hubble-Lemaitre constant H(0) in future observations of dark sirens using the Cosmic Explorer and the Einstein Telescope. Our results show that the precision remains high as long as the number of well-localized dark sirens is below 300, but starts to decrease when the number exceeds 300 and incorrect spatial localizations become statistically noticeable.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Enis Belgacem, Tomislav Prokopec
Summary: Local measurements of the Hubble parameter are in disagreement with global values, and the assumptions on the cosmological history and origin of dark energy play a key role in this tension. The researchers propose a scenario where dark energy arises from the amplification of quantum fluctuations during inflation. They find that spatial correlations from inflationary quantum fluctuations can reduce the Hubble tension, relieving the problem with respect to the standard cosmological model. Upcoming missions will provide tests for these predictions.
Article
Astronomy & Astrophysics
Angel Garcia-Chung, Benito A. Juarez-Aubr, Daniel Sudarsky
Summary: In a seminal paper, Unruh and Wald showed that the detection of a Rindler particle corresponds to the creation of a Minkowski particle from the inertial viewpoint. This paper revisits the situation studied in that work and discusses the possibility of superluminal communication protocols between observers confined to the right and left Rindler wedges. Various ways in which physics could prevent such measurement-induced faster-than-light signaling protocols are discussed.
Article
Physics, Nuclear
Sirachak Panpanich, Piyabut Burikham, Supakchai Ponglertsakul, Lunchakorn Tannukij
Summary: Recent low-redshift observations have shown that the current Hubble parameter value is higher than the predicted value based on Planck's observations of the Cosmic Microwave Background radiation and the CDM model. By adding an extra component with negative density to the Friedmann equation, the Hubble tension can be addressed without changing Planck's constraints on matter and dark energy densities. The proposed quintom model, involving two scalar fields, potentially alleviates the Hubble tension while achieving a viable cosmological scenario.
Article
Physics, Multidisciplinary
A. Najafi, H. Hossienkhani
Summary: In this work, a cosmological model based on the BI metric and the Ricci dark energy model is implemented using the most recent SNIa compilations and H(z) data. The present values of Hubble's constant, matter density parameter, and anisotropy parameter are estimated and the equation of state parameter is constrained using maximum likelihood technique and observational data. The model also provides the present value of the deceleration parameter and the transition redshift. Finally, the anisotropy effects on the evolution of H(z) are compared with different observational datasets.
COMMUNICATIONS IN THEORETICAL PHYSICS
(2022)
Article
Astronomy & Astrophysics
Shota Nakagawa, Fuminobu Takahashi, Wen Yin
Summary: We propose a new scenario of early dark energy (EDE) with a dark Higgs field trapped at the origin. The trapping effect is achieved by using dark photons produced nonthermally by coherent oscillations of axions. The dark Higgs quickly decays into dark photons, which act as self-interacting dark radiation. Interestingly, the axion not only produces dark photons but also explains dark matter.
Article
Astronomy & Astrophysics
Abdolali Banihashemi, Nima Khosravi, Arman Shafieloo
Summary: A new critically emergent dark energy model (CEDE) is proposed, which is consistent with both Planck's CMB data and Riess et al.'s local Hubble constant measurements. The model suggests that dark energy emerges at a transition redshift, providing a possible explanation for the Hubble constant tension.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
H. R. M. Zarandi, E. Ebrahimi
Summary: This paper studies the cosmic age problem in holographic and generalized ghost dark energy models, and finds that non-linear interactions can alleviate the age problem. By analyzing age tests and data sets, the study also discovers a new bound for a parameter and shows that the generalized ghost dark energy can completely alleviate the cosmic age problem.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Physics, Multidisciplinary
Michael Paul Gough
Summary: This article explores the role of information energy as a source of dark energy. The formation of stars and structure in the universe leads to the emergence of dynamic and transitional dark energy, primarily contributed by heated gas and dust from stars. This information dark energy exhibits characteristics that can resolve various tensions and problems in cosmology, and it can be potentially falsified through experimental observation.
Article
Astronomy & Astrophysics
Yan-Hong Yao, Xin-He Meng
Summary: The H0 tension between low- and high-redshift measurements is a serious issue. To address this, the authors propose a new interacting dark energy model with a time-varying coupling parameter. They parameterize the densities of dark matter and dark energy, and their findings suggest a correlation between the parameter and the Hubble constant.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Physics, Multidisciplinary
Vinod Kumar Bhardwaj, Priyanka Garg, Anirudh Pradhan, Syamala Krishnannair
Summary: In this study, we investigate the power-law entropy corrected holographic dark energy (PLECHDE) model with Hubble horizon cutoff. Using observational data, we constrain the model and calculate relevant cosmological parameters. The results show that the model is consistent with modern observations and matches well with current datasets.
CHINESE JOURNAL OF PHYSICS
(2022)
Article
Astronomy & Astrophysics
Shulei Cao, Joseph Ryan, Bharat Ratra
Summary: By jointly analyzing data from various cosmological models, we obtained model-independent estimates of the Hubble constant and non-relativistic matter density parameter, as well as more restrictive constraints by including data from quasar angular size and H II starburst galaxy measurements.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
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.