arXiv subjects

Yuhao Mu

Publications and source records attributed to Yuhao Mu.

12 recordsLinked to original sources

arXiv2025

A Revisiting of the Pressure Elimination for a Fluid-Structure PDE Interaction and Its Implications

In this paper we construct a novel technique for eliminating and recovering the pressure for a fluid-structure interaction model. This pressure elimination methodology is valid for general bounded Lipschitz domains. The specific fluid-structure interaction (FSI) that we consider is a well-known model of Stokes flow coupled to a system of linear elasticity, which constitutes a coupled parabolic-hyperbolic system. The coupling between the two distinct PDE dynamics occurs across a boundary interface, with each of the components evolving on its own distinct geometry, with the domains of each being Lipschitz. Our new pressure elimination technique admits of an explicit $C_{0}$-semigroup generator representation $\mathcal{A}: D(\mathcal{A}) \subset \mathbf{H} \to \mathbf{H}$, where $\mathbf{H}$ is the associated finite energy space of fluid-structure initial data. This leads to a novel proof of well-posedness in the explicit semigroup sense of the continuous PDE, now valid in general geometries. Subsequently, we illustrate an immediate consequence of our semigroup well-posedness result; namely a finite element method (FEM) with associated rates of convergence for a static version of the FSI, posed on polygonal domains.

math.AP↗

arXiv2023

Coupled Dark Sector Models and Cosmological Tensions

In this paper, we introduce two coupling models of early dark energy (EDE) and cold dark matter aimed at alleviating cosmological tensions. We utilize the EDE component in the coupling models to relieve the Hubble tension, while leveraging the interaction between dark matter and dark energy to alleviate the large-scale structure tension. The interaction is implemented in the form of pure momentum coupling and Yukawa coupling. We employed various cosmological datasets, including cosmic microwave background radiation, baryon acoustic oscillations, Type Ia supernovae, the local distance-ladder data (SH0ES), and the Dark Energy Survey Year-3 data, to analyze our models. We first exclude SH0ES data from the entire dataset to constrain the parameters of novel models. We observe that the constraints on $H_0$ from two coupling models are slightly higher than that from the $\Lambda$CDM model, but they exhibit a significant inconsistency with the SH0ES data, consistent with prior research findings in the EDE model. Subsequently, we incorporate SH0ES data to re-constrain the parameters of various models, our findings reveal that both coupling models yield best-fit values for $H_0$ approximately around $72.23$ km/s/Mpc, effectively mitigating the Hubble tension. Similar to the EDE model, the coupling models yield the $S_8$ values that still surpasses the result of the $\Lambda$CDM model. Nevertheless, the best-fit values for $S_8$ obtained with the two new models are 0.8192 and 0.8177, respectively, which are lower than the 0.8316 achieved by the EDE model. Consequently, although our coupling models fail to fully resolve the large-scale structure tension, they partially mitigate the adverse effect of the original EDE model.

astro-ph.CO↗

arXiv2023

Mitigating Cosmological Tensions via Momentum-Coupled Dark Sector Model

In this paper, we investigate the momentum coupling between early dark energy (EDE) and cold dark matter to alleviate cosmological tensions. EDE has exhibited promising efficacy in addressing the Hubble tension, but it exacerbates the large-scale structure tension. We consider the interaction between EDE and cold dark matter, introducing a pure momentum exchange between them to alleviate the large-scale structure tension introduced by the EDE model. We find that this coupling model is consistent with the EDE model, yielding a higher value for $H_0$, which can resolve the Hubble tension. Additionally, the new model exhibits a suppressive effect on structure growth, contributing to the alleviation of the large-scale structure tension. By utilizing the Markov Chain Monte Carlo method and incorporating various cosmological data, the coupling model constrains the best-fit values for $H_0$ to be $72.23$ km/s/Mpc and for $S_8$ to be 0.8192. Compared to the $\Lambda$CDM model, the new models have not fully resolved the large-scale structure tension. However, in contrast to the best-fit value of 0.8316 for $S_8$ obtained from the EDE model, the new model alleviates the negative impact of the EDE model.

astro-ph.CO↗

arXiv2023

Cosmological Constraints on Thermal Friction of Axion Dark Matter

In this paper, we investigate the process in which axion dark matter undergoes thermal friction, resulting in energy injection into dark radiation, with the aim of mitigating the Hubble tension and large-scale structure tension. In the early universe, this scenario led to a rapid increase in the energy density of dark radiation; in the late universe, the evolution of axion dark matter is similar to that of cold dark matter, with this scenario resembling decaying dark matter and serving to ease the large-scale structure tension. We employ cosmological observational data, including cosmic microwave background (CMB), baryon acoustic oscillation (BAO), supernova data (SNIa), $H_0$ measurement from SH0ES, and $S_8$ from the Dark Energy Survey Year-3 (DES), to study and analyze this model. Our results indicate that the thermal friction model offers partial alleviation of the large-scale structure tension, while its contribution on alleviating Hubble tension can be ignored. The new model yields the value of $S_8$ is $0.795\pm 0.011$ at a 68% confidence level, while the $\Lambda$CDM model yields a result of $0.8023\pm 0.0085$. In addition, the new model exhibits a lower $\chi^2_\mathrm{tot}$ value, with a difference of -2.60 compared to the $\Lambda$CDM model. Additionally, we incorporate Lyman-$\alpha$ data to re-constrain the new model and find a slight improvement in the results, with the values of $H_0$ and $S_8$ being $68.76^{+0.39}_{-0.35}$ km/s/Mpc and $0.791\pm 0.011$ at a 68% confidence level, respectively.

astro-ph.CO↗

arXiv2023

Kinetically Coupled Scalar Fields Model and Cosmological Tensions

In this paper, we investigate the kinetically coupled early dark energy (EDE) and scalar field dark matter to address cosmological tensions. The EDE model presents an intriguing theoretical approach to resolving the Hubble tension, but it exacerbates the large-scale structure tension. We consider the interaction between dark matter and EDE, such that the drag of dark energy on dark matter suppresses structure growth, which can alleviate large-scale structure tension. We replace cold dark matter with scalar field dark matter, which has the property of suppressing structure growth on small scales. We employed the Markov Chain Monte Carlo method to constrain the model parameters, our new model reveals a non-zero coupling constant of $0.030 \pm 0.026$ at a 68% confidence level. The coupled model yields the Hubble constant value of $72.38^{+0.71}_{-0.82}$ km/s/Mpc, which resolves the Hubble tension. However, similar to the EDE model, it also obtains a larger $S_8$ value compared to the $\Lambda$CDM model, further exacerbating the large-scale structure tension. The EDE model and the new model yield the best-fit values of $0.8316$ and $0.8146$ for $S_8$, respectively, indicating that the new model partially alleviates the negative effect of the EDE model. However, this signature disappears when comparing marginalised posterior probabilities, and both models produce similar results. The values obtained from the EDE model and the new model are $0.822^{+0.011}_{-0.0093}$ and $0.819^{+0.013}_{-0.0092}$, respectively, at a 68% confidence level.

astro-ph.CO↗

arXiv2023

Alleviating Cosmological Tensions with a Coupled Scalar Fields Model

In this paper, we investigate the interaction between early dark energy (EDE) and scalar field dark matter, proposing a coupled scalar fields model to address the Hubble tension and $S_8$ tension. While the EDE model successfully alleviates the Hubble tension, it exacerbates the $S_8$ tension. To mitigate the negative impact of EDE, we introduce the interaction between EDE and dark matter. Specifically, we replace cold dark matter with scalar field dark matter, given its capability to suppress structure growth on small scales. We constrained the new model using cosmological observations including the temperature and polarization anisotropy power spectra data of cosmic microwave background radiation (CMB) from \textit{Planck} 2018 results, baryon acoustic oscillations (BAO) measurements extracted from 6dFGS, SDSS and BOSS, the Pantheon sample of type Ia supernovae (SNIa), the local distance-ladder data (SH0ES), and the Dark Energy Survey Year-3 data. Employing Markov Chain Monte Carlo method, we find that this novel model yields best-fit values of $H_0$ and $S_8$ equal to $71.13$ km/s/Mpc and $0.8256$, respectively. Compared to the $\Lambda$CDM model, the new model alleviates the Hubble tension but still fails to resolve the $S_8$ tension. However, we obtain a smaller value of $S_8$ compared to the result of $0.8316$ obtained for EDE model, which mitigates to some extent the shortcoming of the EDE model.

astro-ph.CO↗

arXiv2023

Data-driven and Almost Model-independent Reconstruction of Modified Gravity

In this paper, a modified factor $\mu$, which characterizes modified gravity in the linear matter density perturbation theory, is reconstructed in a data-driven and almost model-independent way via Gaussian process by using currently available cosmic observations. Utilizing the Pantheon+ SNe Ia samples, the observed Hubble parameter $H(z)$ and the redshift space distortion $f\sigma_8(z)$ data points, one finds out a time varying $\mu$ at low redshifts. The reconstructed $\mu$ implies that more complicated modified gravity beyond the simplest general relativity and the Dvali-Gabadadze-Porrati braneworld model is required.

astro-ph.CO↗

arXiv2023

Cosmography via Gaussian Process with Gamma Ray Bursts

In this paper, we firstly calibrate the Amati relation (the $E_{\rm p}-E_{\rm iso}$ correlation) of gamma ray bursts (GRBs) at low redshifts ($z<0.8$) via Gaussian process by using the type Ia supernovae samples from Pantheon+ under the philosophy that objects at the same redshift should have the same luminosity distance in any cosmology. As a result, this calibration derives the distance moduli of GRBs at high redshifts ($z>0.8$). For an application of these derived distance modulus of GRBs to cosmology, via Gaussian process again, a series of cosmography parameters, which describe kinematics of our Universe, up to the fifth oder and the redshift $z\sim 5$, i.e. the Hubble parameter $H(z)$, the deceleration parameter $q(z)$, the jerk parameter $j(z)$, the snap parameter $s(z)$ and the lerk parameter $l(z)$, are reconstructed from the cosmic observations. The reconstructed cosmography parameters show a transition singularity at $z\sim 6$, it may resort to two possible explanations: one is that the GRBs data points at high redshift $z>5$ are still reliable, it means that new physics beyond the $\Lambda$CDM model happens; another one is that the quality and quantity of GRBs data points at high redshift $z>5$ are not good enough to give any viable prediction of the kinematics of our Universe. To pin down this problem, more high redshifts $z>5$ cosmic observational are still needed.

astro-ph.CO↗

arXiv2022

Equality scale-based and sound horizon-based analysis of the Hubble tension

The Hubble horizon at matter-radiation equality ($k^{-1}_{\rm{eq}}$) and the sound horizon at the last scattering surface ($r_s(z_*)$) provides interesting consistency check for the $\Lambda$CDM model and its extensions. It is well known that the reduction of $r_s$ can be compensated by the increase of $H_0$, while the same is true for the standard rulers $k_{\rm{eq}}$. Adding extra radiational component to the early universe can reduce $k_{\rm{eq}}$. The addition of early dark energy (EDE), however, tends to increase $k_{\rm{eq}}$. We perform $k_{\rm{eq}}$- and $r_s$-based analyses in both the EDE model and the Wess-Zumino Dark Radiation (WZDR) model. In the latter case we find $\Delta H_0 = 0.4$ between the $r_s$- and $k_{\rm{eq}}$-based datasets, while in the former case we find $\Delta H_0 = 1.2$. This result suggests that the dark radiation scenario is more consistent in the fit of the two standard rulers ($k_{\rm{eq}}$ and $r_s$). As a forecast analyses, we fit the two models with a mock $k_{\rm{eq}}$ prior derived from \emph{Planck} best-fit $\Lambda$CDM model. Compared with the best-fit $H_0$ in baseline $\Lambda$CDM model, we find $\Delta H_0 = 1.1$ for WZDR model and $\Delta H_0 = - 2.4$ for EDE model.

astro-ph.CO↗

arXiv2022

Limit on the dark matter mass from its interaction with photons

In this work, we explore the phenomenology of generalized dark matter (GDM) which interacts with photons ($\gamma$). We assume that DM establishes elastic scattering with $\gamma$ when it has already become nonrelativistic, otherwise the abundance of DM today is disfavored by current observations. Within this scenario, the equation of state (EoS) of DM is determined by its mass ($m_\chi$) and the DM-$\gamma$ scattering cross-section. The distinctive imprints of a nonzero EoS of DM on CMB angular power spectrum allow us to set a lower limit on $m_\chi$ with Planck 2018 data alone, i.e., $m_{\chi} > 8.7$ keV at $95\%$ C.L. In the study of cosmic concordance problems, we find that the GDM scenario preserves the sound horizon ($r_s(z_*)$) predicted in the fiducial $\Lambda$CDM model, and thus does not solve the $H_0$ tension. When performing the joint analysis of Planck+LSS datasets, the best-fit $S_8= 0.785\pm 0.017$ closely matches the given $S_8$ prior. This suggests that the GDM scenario can be counted as a viable candidate to restore the $S_8$ ($\sigma_{8}$) tension.

astro-ph.CO↗

arXiv2021

Can phantom transition at $z\sim 1$ restore the Cosmic concordance?

The tension among inferences of Hubble constant ($H_0$) is found in a large array of datasets combinations. Modification to the late expansion history is the most direct solution to this discrepancy. In this work, we examine the viability of restoring the cosmological concordance with a novel version of transitional dark energy (TDE). The main anchors for the cosmic distance scale: cosmic microwave background (CMB) radiation, baryon acoustic oscillation (BAO), and Type Ia supernova (SNe Ia) calibrated by Cepheids form a "impossible trinity", i.e., it's plausible to reconcile with any two of the three but unlikely to accommodate them all. Particularly, the tension between BAO and the calibrated SNe Ia can not be reconciled within the scenarios of late dark energy. Nevertheless, our analysis suggests that the TDE model can reconcile with CMB and SNe Ia calibrated by its absolute magnitude ($M_{\rm{B}}$) when the equation of state (EoS) of DE transits around $z\sim1$. Meanwhile, we see a positive sign that the EoS transits with the inclusion of a local prior on $M_{\rm{B}}$, whereas the opposite is true without the $M_{\rm{B}}$ prior.

astro-ph.CO↗

arXiv2019

Detecting the neutrino mass and mass hierarchy from global data

In this paper, we have constrained the neutrino mass and mass hierarchy in the $\Lambda$CDM cosmology with the neutrino mass hierarchy parameter $\Delta$, which represents different mass orderings, by using the {\it Planck} 2015 + BAO + SN + $H_{0}$ data set, together with the neutrino oscillation and neutrinoless double beta decay data. We find that the mass of the lightest neutrinos and the total neutrino mass are no more than $0.035$eV and $0.133$ eV at $95\%$ confidence level, respectively. Comparing the result of our joint analysis with that obtained using cosmological data alone, we find that, by adding the neutrino oscillation and neutrinoless double beta decay data, the tendency for normal hierarchy has increased a lot. By means of importance sampling, three other priors are taken into account, i.e., the flat logarithmic prior on the absolute value of the neutrino hierarchy parameter $\Delta$, the flat linear prior on the total neutrino mass $\Sigma m_{\nu}$, and the flat logarithmic prior on $\Sigma m_{\nu}$. We find that the preference for the normal hierarchy is in agreement whatever what kinds of priors we choose. Finally, we make a Bayesian model analysis about four priors and we find that flat-linear and the flat logarithmic priors on $\Sigma m_{\nu}$ are the most favored priors.

astro-ph.CO↗