Physics of the Dark Universe最新文献

We consider baryogenesis in quantum fluctuation modified gravity. We explore three forms (two are newly proposed here) of baryogenesis interaction and discuss the effect of these interaction terms on the baryon-to-entropy ratio during the radiation era of the expanding universe. We constrain the model parameters with the current observational data, implying that this modified gravity is capable to address the issue of baryon asymmetry in a successful manner.

The 21-cm signal is the most important measurement for us to understand physics during cosmic dawn. It is the key for us to understand the expansion history of the Universe and the nature of dark energy. In this paper, we focused on the characteristic 21-cm power spectrum of a special dynamic dark energy – the Interacting Chevallier-Polarski-Linder (ICPL) model – and compared it with those of the $\Lambda$CDM and CPL models. From the expected noise of HERA, we found more precise experiments in the future can detect the features of interacting dark energy in the 21-cm power spectra. By studying the brightness temperature, we found the ICPL model is closer to the observation of EDGES compared to the $\Lambda$CDM, thus alleviating the tension between theory and experiments.

The main aim of this manuscript is to analyze the viability and stability of pulsars filled with charged anisotropic matter configuration in extended symmetric teleparallel theory. A particular model of this gravitational theory is considered to reduce the complexity of the system and formulate the explicit field equations which govern the interaction between matter and geometry. The configuration of static spherical symmetric structures is examined through the non-singular viable solutions. The undetermined constants in the metric coefficients are determined by the Darmois junction conditions. Further, we explore different physical characteristics in the interior of charged pulsars to check their viability. The equilibrium state of the charged stellar objects is discussed using the Tolman–Oppenheimer–Volkoff equation and the stability is examined by the causality condition, Herrera cracking approach and adiabatic index, respectively. Our findings indicate that the proposed charged stars in this modified gravity are physically viable and stable.

We fit the solution of hydrostatic equations to the observed total and baryonic mass densities ${\rho }_{\text{tot}}\left(r\right)$ and ${\rho }_b\left(r\right)$ of 23 massive elliptical galaxies. Our purpose is to investigate how well these measurements constrain the cusp or core of elliptical galaxies, and the dark matter comoving temperature-to-mass ratio, or equivalently, the adiabatic invariant $v_{h\text{rms}}\left(1\right)$, of dark matter. These studies reinforce the view that the lower bound of the measured distribution of the comoving thermal velocity $v_{h\text{rms}}\left(1\right)$ is of cosmological origin, in agreement with studies of spiral and dwarf galaxies.

This paper explores the rapid expansion of the Universe during its later stages within the context of $f(R,L_m)$ gravity theory. We present a novel parametrization of the Hubble parameter in a manner independent of any specific model and employ it to analyze the Friedmann equations within the FLRW Universe framework. Using a Markov Chain Monte Carlo (MCMC) approach, we derive the model parameters by analyzing a composite dataset comprising 31 Cosmic Chronometers (CC) data points, 26 independent Baryonic Acoustic Oscillations (BAO) measurements, and 1701 data points from Pantheon+SH0ES dataset. The trajectory of the deceleration parameter highlights the shift from deceleration to acceleration in the evolution of the Universe. Additionally, we delve into the dynamics of fundamental cosmological variables for two nonlinear $f(R,L_m)$ models, including energy density, pressure, equation of state (EoS) parameter, and energy conditions.

A general covariant Einstein–Gauss–Bonnet Gravity in Four-Dimensional (4D EGB) spacetime is shown to bypass Lovelock’s theorem and is free from Ostrogradsky instability. Meanwhile, the bumblebee theory is a vector–tensor theory. It extends the Einstein–Maxwell theory that allows for the spontaneous symmetry breaking that leads to the field acquiring a vacuum expectation value, introducing Lorentz violation into the system. We investigate rotating black holes in the 4D EGB-bumblebee gravity model where Lorentz symmetry is spontaneously broken – Kerr EGB bumblebee (KEGBB) black holes. The latest observations from the Event Horizon Telescope (EHT) of the supermassive black holes (SMBHs) M87* and Sgr A* have sparked intensified interest in the study of black hole shadows, which present a novel avenue for investigating SMBHs within the strong-field regime. Motivated by this, we model SMBHs M87* and Sgr A* as KEGBB black holes, and using the EHT observation result, for given $l$, to find earlier upper limits on the $\alpha$ and $a$ are altered. The KEGBB and Kerr black holes are indiscernible in some parameter space, and one cannot rule out the possibility that the former may serve as strong candidates for astrophysical black holes. Employing our newly developed parameter estimation technique, we use two EHT observables – namely, the angular diameter of the shadow, $d_{sh}$, and the axial ratio, $D_A$ – to estimate parameters of M87* and Sgr A* taking into account observational errors associated with the EHT results.

In this paper, we present independent determinations of cosmological parameters and new constraints on $f\left(T\right)$ cosmologies, employing two new catalogs related to HII galaxy Hubble and CMB distance priors, along with the local standard measurements, SNIa, $H\left(z\right)$ measurements, growth rate data (RSD), and BAO baselines. We found that the marginalized best-fit C.L. $H_0$ and ${\sigma }_8$ parameters within $f\left(T\right)$ cosmologies allow $f\left(T\right)$ to relax the current cosmological tensions using HIIG data, which produces a larger range of admissible values for the current Hubble constant, and when all baselines are considered, the uncertainty bands for $H_0$ and the matter density parameter reduce significantly.

The primary goal of this article is to analyze the disproportion between matter and antimatter in the Universe using the phenomenon of gravitational baryogenesis under the framework of $f(R,G,T)$ gravity, where $R$, $G$ and $T$ are Ricci Scalar, Gauss–Bonnet invariant and the trace of energy momentum tensor. This phenomenon based on charge parity violation interactions and in this article we generate it through the coupling between the baryon matter current ($J^{\nu }$) and ${\partial }_{\nu }(R+G+T)$ as well as for generalized case with ($J^{\nu }$) and ${\partial }_{\nu }f(R+G+T)$. We evaluate the ratio $\frac{{\eta }_{{}_B}}{S}$ (baryon to entropy) of the propose model of $f(R,G,T)$ gravity for gravitational baryogenesis and generalized gravitational baryogenesis with power-law form consideration for the scale factor in different eras of the Universe. We notice that the results of ($\frac{{\eta }_{{}_B}}{S}$) are compatible with its observational bound under the optimal choice of model parameters and hence we say that this gravity is good for gravitational baryogenesis under certain constraints of model parameters.