arXiv subjects

Yi-Fan Wang

Publications and source records attributed to Yi-Fan Wang.

42 records · Page 3Linked to original sources

arXiv2018

Constraints on the Primordial Black Hole Abundance from the First Advanced LIGO Observation Run Using the Stochastic Gravitational-Wave Background

Advanced LIGO's discovery of gravitational-wave events is stimulating extensive studies on the origin of binary black holes. Assuming that the gravitational-wave events can be explained by binary primordial black hole mergers, we utilize the upper limits on the stochastic gravitational-wave background given by Advanced LIGO as a new observational window to independently constrain the abundance of primordial black holes in dark matter. We show that Advanced LIGO's first observation run gives the best constraint on the primordial black hole abundance in the mass range $1 M_\odot \lesssim M_\text{PBH}\lesssim 100 M_\odot$, pushing the previous microlensing and dwarf galaxy dynamics constraints tighter by 1 order of magnitude. Moreover, we discuss the possibility to detect the stochastic gravitational-wave background from primordial black holes, in particular from subsolar mass primordial black holes, by Advanced LIGO in the near future.

astro-ph.CO↗

arXiv2018

Constraints on the sum of neutrino masses using cosmological data including the latest extended Baryon Oscillation Spectroscopic Survey DR14 quasar sample

We investigate the constraints on the sum of neutrino masses ($Σm_ν$) using the most recent cosmological data, which combines the distance measurement from baryonic acoustic oscillation in the extended Baryon Oscillation Spectroscopic Survey DR14 quasar sample with the power spectra of temperature and polarization anisotropies in the cosmic microwave background from the Planck 2015 data release. We also use other low-redshift observations including the baryonic acoustic oscillation at relatively low redshifts, the supernovae of type Ia and the local measurement of Hubble constant. In the standard cosmological constant $Λ$ cold dark matter plus massive neutrino model, we obtain the $95\%$ \acl{CL} upper limit to be $Σm_ν<0.129~\mathrm{eV}$ for the degenerate mass hierarchy, $Σm_ν<0.159~\mathrm{eV}$ for the normal mass hierarchy, and $Σm_ν<0.189~\mathrm{eV}$ for the inverted mass hierarchy. Based on Bayesian evidence, we find that the degenerate hierarchy is positively supported, and the current data combination can not distinguish normal and inverted hierarchies. Assuming the degenerate mass hierarchy, we extend our study to non-standard cosmological models including the generic dark energy, the spatial curvature, and the extra relativistic degrees of freedom, respectively, but find these models not favored by the data.

astro-ph.CO↗

arXiv2017

Weighted H-index for identifying influential spreaders

Spreading is a ubiquitous process in the social, biological and technological systems. Therefore, identifying influential spreaders, which is important to prevent epidemic spreading and to establish effective vaccination strategies, is full of theoretical and practical significance. In this paper, a weighted h-index centrality based on virtual nodes extension is proposed to quantify the spreading influence of nodes in complex networks. Simulation results on real-world networks reveal that the proposed method provides more accurate and more consistent ranking than the five classical methods. Moreover, we observe that the monotonicity and the computational complexity of our measure can also yield excellent performance.

physics.soc-ph↗

arXiv2017

Hawking Radiation: A Comparison of Pure-state and Thermal Descriptions

The cases of the Hawking radiation field being described by a pure state and by the usual thermal state are compared within the CGHS dilaton gravity model. The field-strength fluctuations of the Fourier modes are computed, showing a discrepancy in the low-energy regime, while coinciding at high energies. Then by defining a distance for density operators and evaluating it for the cases concerned, the difference between the pure and thermal descriptions is quantified and found to be exponentially small with respect to the Hawking temperature. Possible physical interpretations are discussed.

gr-qc↗

arXiv2016

Impacts of dark energy on weighing neutrinos: mass hierarchies considered

Taking into account the mass splittings between three active neutrinos, we investigate impacts of dark energy on constraining the total neutrino mass $\sum m_ν$ by using recent cosmological observations. We consider two typical dark energy models, namely, the $w$CDM model and the holographic dark energy (HDE) model, which both have an additional free parameter compared with the $Λ$CDM model. We employ the Planck 2015 data of CMB temperature and polarization anisotropies, combined with low-redshift measurements on BAO distance scales, type Ia supernovae, Hubble constant, and Planck lensing. Compared to the $Λ$CDM model, our study shows that the upper limit on $\sum m_ν$ becomes much looser in the $w$CDM model while much tighter in the HDE model. In the HDE model, we obtain the $95\%$ CL upper limit $\sum m_ν<0.105~\textrm{eV}$ for three degenerate neutrinos. This might be the most stringent constraint on $\sum m_ν$ by far and is almost on the verge of diagnosing the neutrino mass hierachies in the HDE model. However, the difference of $χ^2$ is still not significant enough to distinguish the neutrino mass hierarchies, even though the minimal $χ^2$ of the normal hierarchy is slightly smaller than that of the inverted hierarchy.

astro-ph.CO↗

arXiv2015

Smoothing methods comparison for CMB E- and B-mode separation

The anisotropies of the B-mode polarization in the cosmic microwave background radiation play a crucial role for the study of the very early Universe. However, in the real observation, the mixture of the E-mode and B-mode can be caused by the partial sky surveys, which must be separated before applied to the cosmological explanation. The separation method developed by Smith (\citealt{PhysRevD.74.083002}) has been widely adopted, where the edge of the top-hat mask should be smoothed to avoid the numerical errors. In this paper, we compare three different smoothing methods, and investigate the leakage residuals of the E-B mixture. We find that, if the less information loss is needed and the smaller region is smoothed in the analysis, the \textit{sin}- and \textit{cos}-smoothing methods are better. However, if we need a clean constructed B-mode map, the larger region around the mask edge should be smoothed. In this case, the \textit{Gaussian}-smoothing method becomes much better. In addition, we find that the leakage caused by the numerical errors in the \textit{Gaussian}-smoothing method mostly concentrates on two bands, which is quite easy to be reduced for the further E-B separations.

astro-ph.CO↗