arXiv subjects

Xin-He Meng

Publications and source records attributed to Xin-He Meng.

At least 19 recordsLinked to original sources

arXiv2024

Restoring cosmological concordance with axion-like early dark energy and dark matter characterized by a constant equation of state?

The Hubble tension persists as a challenge in cosmology. Even early dark energy (EDE) models, initially considered the most promising for alleviating the Hubble tension, fall short of addressing the issue without exacerbating other tensions, such as the $S_8$ tension. Considering that a negative dark matter (DM) equation of state (EoS) parameter is conducive to reduce the value of $σ_8$ parameter, we extend the axion-like EDE model in this paper by replacing the cold dark matter (CDM) with DM characterized by a constant EoS $w_{\rm dm}$ (referred as WDM hereafter). We then impose constraints on this axion-like EDE extension model, along with three other models: the axion-like EDE model, $Λ$WDM, and $Λ$CDM. These constraints are derived from a comprehensive analysis incorporating data from the Planck 2018 cosmic microwave background (CMB), baryon acoustic oscillations (BAO), the Pantheon compilation, as well as a prior on $H_0$ (i.e., $H_0=73.04\pm1.04$, based on the latest local measurement by Riess et al.) and a Gaussianized prior on $S_8$ (i.e., $S_8=0.766\pm0.017$, determined through the joint analysis of KID1000+BOSS+2dLenS). We find that although the new model maintains the ability to alleviate the Hubble tension to $\sim$ 1.4$σ$, it still exacerbate the $S_8$ tension to a level similar to that of the axion-like EDE model.

astro-ph.CO↗

arXiv2024

Can interacting dark energy with dynamical coupling resolve the Hubble tension

The $H_0$ tension between low- and high- redshift measurements is definitely a serious issue faced by current cosmologists since it ranges from 4$σ$ to 6$σ$. To relieve this tension, in this paper we propose a new interacting dark energy model with time varying coupling parameter by parameterizing the densities of dark matter and dark energy, this parametric approach for interacting dark sectors are inspired by our previous work concerning the coupled generalized three-form dark energy model in which dark matter and dark energy behave like two uncoupled dark sectors with effective equation of state when the three-form $|κX|\gg1$, for this reason, we reconstruct coupled generalized three-form dark energy from such parametric model under the condition $|κX_0|\gg1$. In the end, we place constraints on three parametric models in light of the Planck 2018 cosmic microwave background (CMB) distance priors, baryon acoustic oscillations (BAO) data and the Pantheon compilation of Type Ia supernovae (SN Ia) data by assuming the parameter $k$ as 0,5,10 respectively. The fitting results show that, for all the observational data sets, the parametric models with $k=0,5,10$ relieve the Hubble tension with the latest local determinations of the Hubble constant from ${\rm SH_0ES}$ team, i.e. the so called R22, to 2.3 $σ$, 1.9 $σ$ and 1.3 $σ$ with $χ_{\rm min}^2=10.43,10.47,10.48$ respectively, revealing that $k$ is positive correlated to the Hubble constant.

astro-ph.CO↗

arXiv2024

Observational constraints on noncold dark matter and phenomenological emergent dark energy

It is well known that there are several long-standing problems implying the discordance of the $Λ$CDM model. Although most of the models proposed to resolve these problems assume that dark matter is pressureless, it is still possible that dark matter is not cold, as current observations have not ruled out this possibility yet. Therefore, in this article, we treat the dark matter equation of state parameter as a free parameter, and apply observational data to investigate the non-coldness of dark matter. Impressing by the simplicity of the phenomenological emergent dark energy (PEDE) and its ability to relieve the Hubble tension, we propose the PEDE+$w_{\rm dm}$ model based on PEDE and non-cold dark matter. We then place constraints on this model in light of the Planck 2018 Cosmic Microwave Background (CMB) anisotropies, baryon acoustic oscillation (BAO) measurements, and the Pantheon compilation of Type Ia supernovae. The results indicate a preference for a negative dark matter equation of state parameter at $95\%$ CL for all data sets except CMB alone and CMB+BAO, which suggests that the non-coldness assumption of dark matter worth to be investigated further in order to understand the nature of dark matter. The Hubble tension is alleviated in this scenario compared to the $Λ$CDM model, with a significance below 3$σ$ level for all data sets except CMB+Pantheon. However, from the analysis based on Bayesian evidence, we clearly see that the data sets favor $Λ$CDM over the PEDE+$w_{\rm dm}$ model.

astro-ph.CO↗

arXiv2024

CPL effective dark energy from the backreaction effect

In this paper, we interpret the dark energy as an effect caused by small scale inhomogeneities of the universe with the use of the spatial averaged approach of Buchert. The model considered here adopts the Chevallier-Polarski-Linder(CPL) parameterizations of the equation of state of the effective perfect fluid from the backreaction effect. Thanks to the effective geometry introduced by Larena et. al.\cite{larena2009testing} in their previous work, we confront such backreaction model with latest type Ia supernova and Hubble parameter observations, coming out with results that reveal the difference between the Friedmann-Lema\^ıtre-Robertson-Walker model and backreaction model.

astro-ph.CO↗

arXiv2022

A new pressure-parametric cosmological model

We put forward a pressure-parametric model to study the tiny deviation from cosmological constant(CC) behavior of the dark sector accelerating the expansion of the Universe. Data from cosmic microwave background (CMB) anisotropies, baryonic acoustic oscillations (BAO), Type Ia supernovae (SN Ia) observation are applied to constrict the model parameters. The constraint results show that such model suffers with $H_0$ tension as well. To realize this model more physically, we reconstruct it with the quintessence and phantom scalar fields, and find out that although the model predicts a quintessence-induced acceleration of the Universe at past and present, at some moment of the future, dark energy's density have a disposition to increase.

astro-ph.CO↗

arXiv2022

A coupled generalized three-form dark energy model

A coupled dark energy model is considered, in which dark energy is represented by a generalized three-form field and dark matter by dust. By assuming the functions $N$ and $I$ in the model's Lagrangian as two power-law functions of the three-form field, we obtain two fixed points of the autonomous system of evolution equations, consisting of a attractor and a tracking saddle point which can be used to alleviate the coincidence problem. After marginalizing the present three-form field $κX_{0}$ which is unable to be strictly restricted, we confront the model with the latest Type Ia Supernova (SN \uppercase\expandafter{\romannumeral1}a), Baryon Acoustic Oscillations (BAO) and Cosmic Microwave Backround (CMB) radiation observations with the fitting results $Ω_{m0}= 0.280_{-0.048}^{+0.048}$ and $λ=0.011_{-0.032}^{+0.032}$ in the $2σ$ confidence level, we also find that the best fitting effective dark energy equation of state (EOS) crosses $ -1$ at redshift around 0.2.

astro-ph.CO↗

arXiv2022

A new coupled three-form dark energy model and implications for the $H_0$ tension

We propose a new coupled three-form dark energy model to relieve the Hubble tension in this paper. Firstly, by performing a dynamical analysis with the coupled three-form dark energy model, we obtain four fixed points, including a saddle point representing a radiation dominated Universe, a saddle point representing a matter dominated Universe, and two attractors representing two saturated de Sitter Universes. Secondly, by confronting the coupled three-form dark energy model and the $Λ$ cold dark matter model (the $Λ$CDM model) with cosmic microwave background (CMB), baryonic acoustic oscillations (BAO), Type Ia supernovae (SN Ia) observations, we obtain $H_0= 67.8_{-0.6}^{+0.7}$($1σ$ level) km/s/Mpc for the coupled three-form dark energy model and $H_0=67.6_{-0.5}^{+0.5}$($1σ$ level) km/s/Mpc for the $Λ$CDM model, the former is in strong tension with the latest local measured $H_0$ value at $4.3σ$ confidence level, while the latter is in strong tension with the latest local measured $H_0$ value at $5.1σ$ level.

astro-ph.CO↗

arXiv2022

Testing backreaction effects with type Ia supernova data and observational Hubble parameter data

The backreaction term ${\cal Q}_\CD$ and the averaged spatial Ricci scalar $\average{\CR}$ in the spatially averaged inhomogeneous Universe can be used to combine into effective perfect fluid energy density $\varrho_{\rm eff}^{\CD}$ and pressure $p_{\rm eff}^{\CD}$ that can be regarded as new effective sources for the backreaction effects. In order to model the realistic evolution of backreaction, we adopt the Chevallier-Polarski-Linder(CPL) parameterizations of the equation of state(EoS) of the effective perfect fluid. To deal with observations in the backreaction context, in this paper, we employ two metrics to describe the the late time Universe, one of them is the standard Friedmann-Lema\^ıtre-Robertson-Walker(FLRW) metric, and the other is a template metric with an evolving curvature parameter introduced by Larena et. al. in \cite{larena2009testing}. We also fit the CPL backreaction model using type Ia supernova(SN Ia) data and observational Hubble parameter data(OHD) with these two metrics, and find out that parameter tensions between two different data sets are larger when the backreaction model is equipped with the template metric, therefore we conclude that the prescription of the geometrical instantaneous spatially-constant curvature $κ_{\CD}$ needs to be modified.

astro-ph.CO↗

arXiv2021

First comprehensive constraints on the Finslerian models using cosmological observations

We perform the first comprehensive constraints on two Finslerian models, i.e., the simplest Finslerian $Λ$CDM (F$Λ$) and non-flat F$Λ$ models using the Type Ia supernovae, baryonic acoustic oscillations, cosmic microwave background and lensing observations. Using the most stringent constraints we can provide, we find that the constrained typical parameters of both Finslerian models are all consistent with zero at the $2σ$ confidence level (C.L.). This means that both Finslerian models just deviate very slightly from the $Λ$CDM one, which is also verified by using two geometrical diagnostics to distinguish three different models from each other. We also find that a spatially flat universe is still preferred in the framework of Finsler geometry, that our measured values of the spectral index $n_s$ of primordial power spectrum in both Fisnlerian models exclude the scale invariance at more than $8σ$ C.L., and that the current $H_0$ tension can be relieved from $3.4σ$ to $2.9σ$ and $2.8σ$ in the F$Λ$ and non-flat F$Λ$ models, respectively.

astro-ph.CO↗

arXiv2021

Constraining viscous dark energy models with the latest cosmological data

Based on the assumption that the dark energy possessing bulk viscosity is homogenously and isotropically permeated in the universe, we propose three new viscous dark energy (VDE) models to characterize the accelerating universe. By constraining these three models with the latest cosmological observations, we find that they just deviate very slightly from the standard cosmological model and can alleviate effectively the current $H_0$ tension between the local observation by the Hubble Space Telescope and the global measurement by the Planck Satellite. Interestingly, we conclude that a spatially flat universe in our VDE model with cosmic curvature is still supported by current data, and the scale invariant primordial power spectrum is strongly excluded at least at the $5.5σ$ confidence level in three VDE models as the Planck result. We also give the $95\%$ upper limits of the typical bulk viscosity parameter $η$ in three VDE scenarios.

astro-ph.CO↗

arXiv2020

The dark energy phenomenon from backreacation effect

In this paper, we interpret the dark energy phenomenon as an averaged effect caused by small scale inhomogeneities of the universe with the use of the spatial averaged approach of Buchert. Two models are considered here, one of which assumes that the backreaction term ${\cal Q}_\CD$ and the averaged spatial Ricci scalar $\average{\CR}$ obey the scaling laws of the volume scale factor $a_\CD$ at adequately late times, and the other one adopts the ansatz that the backreaction term ${\cal Q}_\CD$ is a constant in the recent universe. Thanks to the effective geometry introduced by Larena et. al. in their previous work, we confront these two backreaction models with latest type Ia supernova and Hubble parameter observations, coming out with the results that the constant backreaction model is slightly favoured over the other model, and within $1σ$ confidence interval of the parameter $n$ in the scaling backreaction model, $\mid{\cal Q}_\CD\mid$ decreases with the increase of the volume scale factor $a_\CD$ at adequately late times. Also, the numerical simulation results show that the constant backreaction model predicts a smaller expansion rate and decelerated expansion rate than the other model does at redshifts higher than about 1, and both backreaction terms begin to accelerate the universe at a redshift around 0.6. In addition, by confronting the standard cosmological model against the same datasets, we find that the effective geometry tends to push the constraint toward a smaller cosmological constant term.

astro-ph.CO↗

arXiv2020

Thin-shell wormholes constrained by cosmological observations

We investigate the thin-shell wormholes constrained by cosmological observations for the first time in the literature. Without loss of generality, we study the thin-shell wormholes in $ω$CDM model and analyze their stability under perturbations preserving the symmetry. Firstly, we constrain the $ω$CDM model using a combination of Union 2.1 SNe Ia data, the latest $H(z)$ data and CMB data. Secondly, we use the constrained dark energy equation of state (EoS) $ω$ which lies in $[-1.05,-0.89]$ to investigate thin-shell wormholes of various black hole spacetimes. We find that the stable Schwarzschild and Reinssner-Nordström thin-shell wormholes constrained by cosmological observations do not exist. In addition, the method we developed can be applied into exploring the stable thin-shell wormholes from any black hole spacetime in the framework of any cosmological theory.

gr-qc↗

arXiv2019

Exploring the deviation of cosmological constant by a generalized pressure dark energy model

We bring forward a generalized pressure dark energy (GPDE) model to explore the evolution of the universe. This model has covered three common pressure parameterization types and can be reconstructed as quintessence and phantom scalar fields, respectively. We adopt the cosmic chronometer (CC) datasets to constrain the parameters. The results show that the inferred late-universe parameters of the GPDE model are (within $1σ$): The present value of Hubble constant $H_{0}=(72.30^{+1.26}_{-1.37})$km s$^{-1}$ Mpc$^{-1}$; Matter density parameter $Ω_{\text{m0}}=0.302^{+0.046}_{-0.047}$, and the universe bias towards quintessence. While when we combine CC data and the $H_0$ data from Planck, the constraint implies that our model matches the $Λ$CDM model nicely. Then we perform dynamic analysis on the GPDE model and find that there is an attractor or a saddle point in the system corresponding to the different values of parameters. Finally, we discuss the ultimate fate of the universe under the phantom scenario in the GPDE model. It is demonstrated that three cases of pseudo rip, little rip, and big rip are all possible.

astro-ph.CO↗

arXiv2019

Searching for the Evidence of Dynamical Dark Energy

In the statistical framework of model-independent Gaussian processes (GP), we search for the evidence of dynamical dark energy (DDE) using the "Joint Light-curve Analysis" (JLA) Type Ia supernovae (SNe Ia) sample, the 30 latest cosmic chronometer data points (H(z)), Planck's shift parameter from cosmic microwave background (CMB) anisotropies, the 156 latest HII galaxy measurements and 79 calibrated gamma-ray bursts (GRBs). We find that the joint constraint from JLA + H(z) + CMB + HII + GRB supports the global measurement of $H_0$ by Planck collaboration very much in the low redshift range $z\in[0, 0.76]$ at the $2σ$ confidence level (C.L.), gives a cosmological constant crossing (quintom-like) equation of state (EoS) of DE at the $2σ$ C.L. and implies that the evolution of the late-time Universe may be actually dominated by the DDE.

astro-ph.CO↗

arXiv2018

Describing the ADD model in a warped geometry

We propose a new description of the (4+N)-dimensional Arkani-Hamed-Dimopoulos-Dvali (ADD) model in a (4+1)-dimensional warped geometry to solve the gauge hierarchy problem. It has the same KK spectrum as in the ADD model and recovers its phenomenons that do not involve the interaction among the graviton KK modes. There is no hierarchy between the fundamental length and the size of the extra dimension. An explicit realization is constructed in the nonlocal gravity theory to give a warped description of the six-dimensional ADD model. Remarkably, the equivalent number N of the extra dimensions in this description may be non-integral, which provides a new mechanism to escape the experimental constrains.

hep-th↗

arXiv2018

A pressure parametric dark energy model

In this paper, we propose a new pressure parametric model of the total cosmos energy components in a spatially flat Friedmann-Robertson-Walker (FRW) universe and then reconstruct the model into quintessence and phantom scenarios, respectively. By constraining with the datasets of the type Ia supernova (SNe Ia), the baryon acoustic oscillation (BAO) and the observational Hubble parameter data(OHD), we find that $Ω_{m0}=0.270^{+0.039}_{-0.034}$ at the 1$σ$ level and our universe slightly biases towards quintessence behavior. Then we use two diagnostics including $Om(a)$ diagnostic and statefinder to discriminate our model from the cosmology constant cold dark matter ($Λ$CDM) model. From $Om(a)$ diagnostic, we find that our model has a relatively large deviation from the $Λ$CDM model at high redshifts and gradually approaches the $Λ$CDM model at low redshifts and in the future evolution, but they can be easily differentiated from each other at the 1$σ$ level all along. By the statefinder, we find that both of quintessence case and phantom case can be well distinguished from the $Λ$CDM model and will gradually deviate from each other. Finally, we discuss the fate of universe evolution (named the rip analysis) for the phantom case of our model and find that the universe will run into a little rip stage.

astro-ph.CO↗

arXiv2018

Can decaying vacuum elucidate the late-time dynamics of the Universe ?

We examine the decay vacuum model with a parameter $ε$ that indicates the vacuum energy decay rate. By constraining this model with cosmic microwave background radiation, baryon acoustic oscillation, type Ia supernovae and 30 H(z) cosmic chronometer data points, we find that $ε=-0.0003\pm0.00024$ with the best fitted $χ^{2}$ value slightly smaller than that in the $Λ$CDM model. A negative value of $ε$ suggesting dark matter energy decay into vacuum energy. We also obtain the Hubble constant $H_{0}=68.05\pm0.56$ that can alleviate the current $H_{0}$ tension between the local observation by the Hubble Space Telescope and the global measurement by the Planck Satellite. Using the effective equation of state formalism, we find this model is quintessence-like.

astro-ph.CO↗

arXiv2017

Exploring the expansion dynamics of the universe from galaxy cluster surveys

To understand the expansion dynamics of the universe from galaxy cluster scales, using the angular diameter distance (ADD) data from two different galaxy cluster surveys, we constrain four cosmological models to explore the underlying value of $H_0$ and employ the model-independent Gaussian Processes to investigate the evolution of the equation of state of dark energy. The ADD data in the X-ray bands consists of two samples covering the redshift ranges [0.023, 0.784] and [0.14, 0.89], respectively. We find that: (i) For these two samples, the obtained values of $H_0$ are more consistent with the recent local observation by Riess et al. than the global measurement by the Plank Collaboration, and the $Λ$CDM model is still preferred utilizing the information criterions; (ii) For the first sample, there is no evidence of dynamical dark energy (DDE) at the $2σ$ confidence level (CL); (iii) For the second one, the reconstructed equation of state of dark energy exhibits a phantom-crossing behavior in the relatively low redshift range over the $2σ$ CL, which gives a hint that the late-time universe may be actually dominated by the DDE from galaxy cluster scales; (iv) By adding a combination of Type Ia Supernovae, cosmic chronometers and Planck-2015 shift parameter and HII galaxy measurements into both ADD samples, the DDE exists evidently over the $2σ$ CL.

astro-ph.CO↗